JP7325516B2 - Power conversion device, motor drive device and air conditioner - Google Patents

Description

The present invention relates to a power conversion device, a motor drive device, and an air conditioner that convert AC power into DC power.

2. Description of the Related Art Conventionally, there is a power converter that converts supplied AC power into DC power and outputs the same using a bridge circuit composed of diodes. In recent years, there is a power converter using a so-called bridgeless circuit in which switching elements are connected in parallel to diodes. A power conversion apparatus using a bridgeless circuit can perform control for boosting the voltage of AC power, power factor improvement control, synchronous rectification control for rectifying AC power, and the like by turning switching elements on and off.

Patent Literature 1 discloses a technique in which a power converter uses a bridgeless circuit to perform synchronous rectification control, boost control, power factor improvement control, and the like. The power conversion device described in Patent Document 1 controls the on/off of switching elements according to the size of the load, and selects control modes, specifically diode rectification control, synchronous rectification control, partial switching control, and high-speed switching control. Various operations are performed by switching the .

JP 2018-7326 A

Bridgeless circuits generally use MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) as switching elements. The characteristics of diodes and MOSFETs used in bridgeless circuits change with temperature. Specifically, diodes have a lower forward voltage drop as temperature increases. The on-resistance of the MOSFET increases as the temperature rises.

When the power conversion device described in Patent Document 1 performs high-speed switching control and synchronous rectification control under high load conditions, the amount of heat generated by the MOSFET increases. Therefore, in the power conversion device described in Patent Document 1, the surrounding temperature rises due to the heat generated by the MOSFET, the on-resistance increases, and the amount of heat generated further increases. There was a problem that it could lead to To solve this problem, a method of selecting diode rectification control or synchronous rectification control depending on the temperature is conceivable, but this requires a dedicated temperature sensor, increases the number of parts, increases the size of the device, and increases the cost. A new problem arises that leads to

SUMMARY OF THE INVENTION It is an object of the present invention to provide a power conversion device capable of achieving highly efficient operation while suppressing device size increase and occurrence of thermal runaway.

In order to solve the above-described problems and achieve the object, a power converter according to the present invention has a reactor having a first end and a second end, the first end being connected to an AC power supply; It is connected to the second end of the reactor and has two arms in which two switching elements having diodes connected in parallel are connected in series. , a smoothing capacitor connected in parallel to two arms of the rectifier circuit, and a detector that detects a physical quantity indicating the operating state of the rectifier circuit. Of the two arms provided in the rectifier circuit, the first arm is connected to an AC power supply via a reactor through a wiring provided between two switching elements, and the second arm is provided between the two switching elements. The wiring connected to the reactor is connected to the AC power supply without going through the reactor. A power converter is a section in which a current from an AC power supply can flow through either a diode or a switching element in a rectifier circuit based on the result of comparing a physical quantity or a value obtained from the physical quantity with three thresholds. , if the physical quantity or the value obtained from the physical quantity is equal to or less than the smallest first threshold value, the power factor improvement control is stopped, the rectifier circuit performs synchronous rectification control in which the current from the AC power supply flows through the switching element, and the physical quantity Alternatively, if the value obtained from the physical quantity is greater than the first threshold and is less than or equal to the second threshold, which is the next smaller threshold than the first threshold, the current from the AC power supply is applied to the switching element of the second arm as the reactor and the rectifier. half of the power supply voltage supplied by the AC power supply Simple switching control that is performed once or a specified number of times in a cycle is performed, and synchronous rectification control is performed, and a physical quantity or a value obtained from the physical quantity is larger than the second threshold and the third smaller than the second threshold. If it is equal to or less than the threshold, simple switching control is performed, synchronous rectification control is performed for the first arm, and diode rectification control is performed to pass the current from the AC power supply to the diode for the second arm. If the physical quantity or the value obtained from the physical quantity is greater than the third threshold, the switching element of the second arm is switched to the power supply short-circuit mode and the current from the AC power supply is transferred from the rectifier circuit to the smoothing capacitor. Pulse Amplitude Modulation control for continuously switching the load power supply mode to flow is continuously performed, and partial synchronous rectification control is performed.

ADVANTAGE OF THE INVENTION The power converter device which concerns on this invention is effective in the ability to implement|achieve highly efficient operation|movement, suppressing the generation|occurrence|production of the enlargement and thermal runaway of a device.

1 is a diagram showing a configuration example of a power converter according to Embodiment 1; FIG. FIG. 2 shows another example of a rectifier circuit included in the power conversion device according to Embodiment 1; Schematic cross-sectional view showing a schematic structure of a MOSFET that constitutes a switching element according to Embodiment 1. FIG. FIG. 2 is a diagram showing paths of currents flowing through the power converter according to the first embodiment; FIG. 4 is a diagram showing timings at which a control unit turns on switching elements in the power converter according to Embodiment 1; FIG. 4 shows an example of an alternating current control method using the power supply short-circuit mode and the load power supply mode of the power converter according to Embodiment 1; A first flow chart showing a control mode switching operation in the control unit of the power converter according to the first embodiment FIG. 4 is a diagram showing another example of paths of currents flowing through the power conversion device according to the first embodiment; FIG. 2 is a diagram for explaining switching loss that occurs in a typical switching element used in the power conversion device according to Embodiment 1; 4 is a diagram showing temperature characteristics of a MOSFET, which is a switching element used in the rectifier circuit of the power converter according to Embodiment 1; FIG. FIG. 2 is a diagram showing temperature characteristics of general diodes such as parasitic diodes used in the rectifier circuit of the power converter according to Embodiment 1; A second flowchart showing the control mode switching operation in the control unit of the power converter according to the first embodiment FIG. 2 is a diagram showing an example of a hardware configuration that realizes a control unit included in the power converter according to Embodiment 1; FIG. FIG. 10 is a diagram showing paths of currents flowing through the power conversion device according to the second embodiment; First flow chart showing control mode switching operation in the control unit of the power converter according to the second embodiment A second flowchart showing a control mode switching operation in the control unit of the power converter according to Embodiment 2 FIG. 5 is a diagram schematically showing losses of MOSFETs and diodes, which are switching elements used in the rectifier circuit of the power converter according to the second embodiment; FIG. 5 is a diagram schematically showing losses of switching elements and parasitic diodes used in the rectifier circuit of the power converter according to the second embodiment; Third flowchart showing control mode switching operation in the control unit of the power converter according to the second embodiment FIG. 10 is a diagram showing an example of heat dissipation of a switching element when the power conversion device according to Embodiment 3 is mounted in an air conditioner; FIG. 11 is a diagram showing a configuration example of a motor drive device according to Embodiment 4; A diagram showing a configuration example of an air conditioner according to Embodiment 5

EMBODIMENT OF THE INVENTION Below, the power converter device which concerns on embodiment of this invention, a motor drive device, and an air conditioner are demonstrated in detail based on drawing. In addition, this invention is not limited by this embodiment.

Embodiment 1.
FIG. 1 is a diagram showing a configuration example of a power conversion device 100 according to Embodiment 1 of the present invention. The power conversion device 100 is a power supply device having an AC/DC conversion function of converting AC power supplied from an AC power supply 1 into DC power using a rectifier circuit 3 and applying the DC power to a load 50 . As shown in FIG. 1, the power conversion device 100 includes a reactor 2, a rectifier circuit 3, a smoothing capacitor 4, a power supply voltage detection unit 5, a power supply current detection unit 6, a bus voltage detection unit 7, a control unit 10. The reactor 2 has a first end and a second end, the first end being connected to the AC power supply 1 .

The rectifier circuit 3 is a circuit having two arms in which two switching elements each having a diode connected in parallel are connected in series, and the two arms are connected in parallel. Specifically, the rectifier circuit 3 includes a first arm 31 that is a first circuit and a second arm 32 that is a second circuit. The first arm 31 comprises a switching element 311 and a switching element 312 connected in series. A parasitic diode 311 a is formed in the switching element 311 . Parasitic diode 311 a is connected in parallel between the drain and source of switching element 311 . A parasitic diode 312 a is formed in the switching element 312 . A parasitic diode 312 a is connected in parallel between the drain and source of the switching element 312 . Each of the parasitic diodes 311a and 312a is a diode used as a freewheeling diode.

The second arm 32 comprises a switching element 321 and a switching element 322 connected in series. The second arm 32 is connected in parallel with the first arm 31 . A parasitic diode 321 a is formed in the switching element 321 . Parasitic diode 321 a is connected in parallel between the drain and source of switching element 321 . A parasitic diode 322 a is formed in the switching element 322 . A parasitic diode 322 a is connected in parallel between the drain and source of the switching element 322 . Each of the parasitic diodes 321a and 322a is a diode used as a freewheeling diode.

Specifically, the power conversion device 100 includes a first wiring 501 and a second wiring 502 each connected to an AC power supply 1 and a reactor 2 arranged on the first wiring 501 . Also, the first arm 31 includes a switching element 311 as a first switching element, a switching element 312 as a second switching element, and a third wiring 503 having a first connection point 506 . The switching element 311 and the switching element 312 are connected in series by a third wiring 503 . A first wiring 501 is connected to the first connection point 506 . The first connection point 506 is connected to the AC power supply 1 via the first wiring 501 and the reactor 2 . A first connection point 506 is connected to the second end of the reactor 2 .

The second arm 32 includes a switching element 321 that is a third switching element, a switching element 322 that is a fourth switching element, and a fourth wiring 504 that includes a second connection point 508. 321 and switching element 322 are connected in series by a fourth wiring 504 . A second wiring 502 is connected to the second connection point 508 . A second connection point 508 is connected to the AC power supply 1 via a second wiring 502 . Note that the rectifier circuit 3 may include at least one or more switching elements so that the AC voltage output from the AC power supply 1 can be converted into a DC voltage.

The smoothing capacitor 4 is a capacitor connected in parallel with the rectifier circuit 3 , specifically the second arm 32 . In the rectifier circuit 3 , one end of the switching element 311 is connected to the positive side of the smoothing capacitor 4 , the other end of the switching element 311 is connected to one end of the switching element 312 , and the other end of the switching element 312 is connected to the negative side of the smoothing capacitor 4 . connected to the side.

The switching elements 311, 312, 321, 322 are composed of MOSFETs. The switching elements 311, 312, 321, and 322 are made of wide band gap (WBG) semiconductors such as gallium nitride (GaN), silicon carbide (SiC), diamond, or aluminum nitride. MOSFETs can be used. By using WBG semiconductors for the switching elements 311, 312, 321 and 322, the voltage resistance is high and the allowable current density is high, so that the size of the module can be reduced. Since the WBG semiconductor has high heat resistance, it is possible to reduce the size of the heat radiation fins of the heat radiation section.

The control unit 10 generates drive signals for operating the switching elements 311, 312, 321, and 322 of the rectifier circuit 3 based on signals output from the power supply voltage detection unit 5, the power supply current detection unit 6, and the bus voltage detection unit 7, respectively. to generate The power supply voltage detection unit 5 is a voltage detection unit that detects a power supply voltage Vs, which is the voltage value of the output voltage of the AC power supply 1, and outputs an electric signal indicating the detection result to the control unit 10. FIG. The power supply current detection unit 6 is a current detection unit that detects the power supply current Is, which is the current value of the current output from the AC power supply 1, and outputs an electric signal indicating the detection result to the control unit 10. FIG. The power supply current Is is the current value of the current flowing between the AC power supply 1 and the rectifier circuit 3 . It should be noted that the power supply current detector 6 only needs to be able to detect the current flowing through the rectifier circuit 3, so the installation position is not limited to the example shown in FIG. It may be between the smoothing capacitor 4 and the load 50 . The bus voltage detection unit 7 is a voltage detection unit that detects the bus voltage Vdc and outputs an electric signal indicating the detection result to the control unit 10 . The bus voltage Vdc is a voltage obtained by smoothing the output voltage of the rectifier circuit 3 with the smoothing capacitor 4 . In the following description, the power supply voltage detection unit 5, the power supply current detection unit 6, and the bus voltage detection unit 7 may be simply referred to as detection units. The power supply voltage Vs detected by the power supply voltage detection unit 5, the power supply current Is detected by the power supply current detection unit 6, and the bus voltage Vdc detected by the bus voltage detection unit 7 are used to determine the operating state of the rectifier circuit 3. It may be referred to as a physical quantity shown. The control unit 10 controls on/off of the switching elements 311, 312, 321, and 322 according to the power supply voltage Vs, the power supply current Is, and the bus voltage Vdc. Note that the control unit 10 may control on/off of the switching elements 311, 312, 321, and 322 using at least one of the power supply voltage Vs, the power supply current Is, and the bus voltage Vdc.

Next, basic operation of the power converter 100 according to Embodiment 1 will be described. Hereinafter, the switching elements 311 and 321 connected to the positive terminal of the AC power supply 1, that is, the positive terminal of the AC power supply 1, may be referred to as upper switching elements. Also, the switching elements 312 and 322 connected to the negative side of the AC power supply 1, that is, to the negative terminal of the AC power supply 1, may be referred to as lower switching elements.

In the first arm 31, the upper switching element and the lower switching element operate complementarily. That is, when one of the upper switching element and the lower switching element is on, the other is off. The switching elements 311 and 312 forming the first arm 31 are driven by a PWM signal, which is a drive signal generated by the controller 10, as will be described later. The ON or OFF operation of the switching elements 311 and 312 according to the PWM signal is hereinafter also referred to as switching operation. In order to prevent a short circuit of the smoothing capacitor 4 via the AC power supply 1 and the reactor 2, both the switching elements 311 and 312 are turned off when the absolute value of the power supply current Is output from the AC power supply 1 is equal to or less than the current threshold. becomes. Below, the short circuit of the smoothing capacitor 4 is called a capacitor short circuit. A capacitor short-circuit is a state in which the energy stored in the smoothing capacitor 4 is released and current is regenerated in the AC power supply 1 .

The switching elements 321 and 322 forming the second arm 32 are turned on or off by a drive signal generated by the control section 10 . The switching elements 321 and 322 are basically turned on or off according to the power supply voltage polarity, which is the polarity of the voltage output from the AC power supply 1 . Specifically, when the power supply voltage polarity is positive, the switching element 322 is on and the switching element 321 is off, and when the power supply voltage polarity is negative, the switching element 321 is on and switching Element 322 is off. In FIG. 1, arrows directed from the control unit 10 to the rectifier circuit 3 indicate drive signals for controlling the on/off of the switching elements 321 and 322 and the aforementioned PWM signals for controlling the on/off of the switching elements 311 and 312. FIG.

In the power converter 100 shown in FIG. 1, only the parasitic diodes 311a, 312a, 321a, and 322a are described for the switching elements 311, 312, 321, and 322, but this is an example, and the switching elements 311, 312, and 321 , 322 may be separately connected in parallel with a rectifying diode, a Schottky barrier diode, or the like. In addition, in the power conversion device 100 shown in FIG. 1, the rectifier circuit 3 is configured to include four switching elements 311, 312, 321, and 322, but two switching elements are eliminated for one arm, and two diodes are provided. It may be a configuration consisting of. FIG. 2 is a diagram showing another example of the rectifier circuit 3 included in the power converter 100 according to the first embodiment. FIG. 2 shows an example in which the second arm 32 is composed of two diodes 321b and 322b. Thus, the rectifier circuit 3 may have a circuit configuration that uses both the switching elements 311 and 312 and the diodes 321b and 322b. Even with the circuit configuration as shown in FIG. 2, the effects of the present embodiment can be obtained. However, in the case of the configuration of the rectifier circuit 3 shown in FIG. Henceforth, the power converter device 100 shown in FIG. 1 is made into an example, and it demonstrates.

Next, the relationship between the states of the switching elements 311, 312, 321, and 322 in Embodiment 1 and the paths of the currents flowing through the power converter 100 according to Embodiment 1 will be described. Prior to this description, the structure of the MOSFET will be described with reference to FIG.

FIG. 3 is a schematic cross-sectional view showing a schematic structure of MOSFETs forming switching elements 311, 312, 321, and 322 according to the first embodiment. FIG. 3 illustrates an n-type MOSFET. For an n-type MOSFET, a p-type semiconductor substrate 600 is used, as shown in FIG. A source electrode S, a drain electrode D and a gate electrode G are formed on the semiconductor substrate 600 . An n-type region 601 is formed in a portion in contact with the source electrode S and the drain electrode D by implanting high-concentration impurity ions. In addition, an oxide insulating film 602 is formed between the portion of the semiconductor substrate 600 where the n-type region 601 is not formed and the gate electrode G. As shown in FIG. That is, an oxide insulating film 602 is interposed between the gate electrode G and the p-type region 603 in the semiconductor substrate 600 .

When a positive voltage is applied to the gate electrode G, electrons are attracted to the interface between the p-type region 603 and the oxide insulating film 602 in the semiconductor substrate 600, and the interface is negatively charged. Where electrons gather, the electron density is higher than the hole density and the area becomes n-type. This n-type portion is called a channel 604 and serves as a passage for current. Channel 604 is an n-type channel in the example of FIG. By turning on the MOSFET, more current flows through the channel 604 than through the parasitic diode formed in the p-type region 603 .

FIG. 4 is a diagram showing paths of currents flowing through the power converter 100 according to the first embodiment. In FIG. 4, only the switching elements 311, 312, 321, and 322 are given reference numerals for the sake of simplicity. In FIG. 4, the switching elements that are turned on for synchronous rectification control are indicated by solid-line circles, and the switching elements that are on for power supply short-circuiting are indicated by dotted-line circles.

FIG. 4A is a diagram showing paths of currents flowing through the power converter 100 according to the first embodiment when the absolute value of the power supply current Is is greater than the current threshold and the polarity of the power supply voltage is positive. . In FIG. 4A, the polarity of the power supply voltage is positive, the switching elements 311 and 321 are on, and the switching elements 312 and 322 are off. Switching element 311 is turned on for synchronous rectification control, and switching element 321 is turned on for power supply short-circuit. FIG. 4(a) shows the state of the power supply short-circuit mode when the power supply voltage polarity is positive. In this state, current flows in the order of AC power supply 1, reactor 2, switching element 311, switching element 321, and AC power supply 1, and a power supply short-circuit path not passing through smoothing capacitor 4 is formed. As described above, in the first embodiment, the current flows through the respective channels of the switching elements 311 and 321 rather than through the parasitic diodes 311a and 321a, thereby forming a power supply short-circuit path. .

FIG. 4B is a diagram showing paths of currents flowing through the power converter 100 according to the first embodiment when the absolute value of the power supply current Is is greater than the current threshold and the polarity of the power supply voltage is positive. . In FIG. 4B, the power supply voltage polarity is positive, the switching elements 311 and 322 are on, and the switching elements 312 and 321 are off. Switching element 311 and switching element 322 are turned on for synchronous rectification control. FIG. 4(b) shows the state of the load power supply mode when the polarity of the power supply voltage is positive. In this state, current flows in the order of AC power supply 1, reactor 2, switching element 311, smoothing capacitor 4, switching element 322, and AC power supply 1. FIG. As described above, in the first embodiment, synchronous rectification control is performed by current flowing through the respective channels of the switching elements 311 and 322 instead of flowing through the parasitic diodes 311a and 322a.

FIG. 4(c) is a diagram showing paths of current flowing through the power converter 100 according to the first embodiment when the absolute value of the power supply current Is is greater than the current threshold and the polarity of the power supply voltage is negative. . In FIG. 4(c), the power supply voltage polarity is negative, the switching elements 312 and 322 are on, and the switching elements 311 and 321 are off. Switching element 312 is turned on for synchronous rectification control, and switching element 322 is turned on for power supply short circuit. FIG. 4(c) shows the state of the power supply short-circuit mode when the power supply voltage polarity is negative. In this state, current flows in the order of AC power supply 1, switching element 322, switching element 312, reactor 2, and AC power supply 1, and a power supply short-circuit path not passing through smoothing capacitor 4 is formed. As described above, in the first embodiment, the current flows through the respective channels of the switching element 322 and the switching element 312 instead of flowing through the parasitic diode 322a and the parasitic diode 312a, thereby forming a power supply short-circuit path. .

FIG. 4(d) is a diagram showing paths of currents flowing through the power converter 100 according to the first embodiment when the absolute value of the power supply current Is is greater than the current threshold and the polarity of the power supply voltage is negative. . In FIG. 4(d), the power supply voltage polarity is negative, the switching elements 312 and 321 are on, and the switching elements 311 and 322 are off. Switching element 312 and switching element 321 are turned on for synchronous rectification control. FIG. 4(d) shows the state of the load power supply mode when the polarity of the power supply voltage is negative. In this state, current flows in the order of AC power supply 1, switching element 321, smoothing capacitor 4, switching element 312, reactor 2, and AC power supply 1. FIG. As described above, in the first embodiment, synchronous rectification control is performed by current flowing through each channel of the switching element 321 and the switching element 312 instead of flowing through the parasitic diode 321a and the parasitic diode 312a.

The control unit 10 can control the values of the power supply current Is and the bus voltage Vdc by controlling the switching of the current paths described above. Specifically, the control unit 10 performs power factor improvement control and boost control by controlling the on/off of the switching elements 311, 312, 321, and 322 so as to generate a current path that short-circuits the power supply via the reactor 2. conduct. The power conversion device 100 continuously switches between the load power supply mode shown in FIG. 4B and the power supply short-circuit mode shown in FIG. 4A when the power supply voltage polarity is positive, and when the power supply voltage polarity is negative By continuously switching between the load power supply mode shown in FIG. 4(d) and the power supply short-circuit mode shown in FIG. do. Specifically, the control unit 10 sets the switching frequency of the switching elements 311 and 312 that perform switching operations by PWM higher than the switching frequency of the switching elements 321 and 322 that perform switching operations according to the polarity of the power supply voltage Vs. to control the on/off of the switching elements 311 , 312 , 321 and 322 . In the following description, the switching elements 311, 312, 321, and 322 may be simply referred to as switching elements when they are not distinguished. Similarly, when the parasitic diodes 311a, 312a, 321a, and 322a are not distinguished, they may simply be referred to as parasitic diodes.

Note that the switching pattern of each switching element shown in FIG. 4 is an example, and the power converter 100 can use a current path other than the switching pattern of each switching element shown in FIG. The power converter 100 can obtain the effects of the present embodiment in any switching pattern.

Next, the timing at which the control unit 10 turns on and off the switching elements will be described. FIG. 5 is a diagram showing timings at which the control unit 10 turns on the switching elements in the power converter 100 according to the first embodiment. In FIG. 5, the horizontal axis is time. 5, Vs is the power supply voltage Vs detected by the power supply voltage detector 5, and Is is the power supply current Is detected by the power supply current detector 6. In FIG. In FIG. 5, the switching elements 311 and 312 are current synchronous switching elements whose ON/OFF is controlled according to the polarity of the power supply current Is. This indicates that it is a voltage synchronous switching element whose ON/OFF is controlled. Also, in FIG. 5, Ith indicates a current threshold. Although FIG. 5 shows one cycle of the AC power output from the AC power supply 1, the control unit 10 performs control similar to that shown in FIG. 5 also in other cycles.

When the power supply voltage polarity is positive, the control unit 10 turns on the switching element 322 and turns off the switching element 321 . Also, when the polarity of the power supply voltage is negative, the control unit 10 turns on the switching element 321 and turns off the switching element 322 . Note that in FIG. 5, the timing at which the switching element 322 is turned off is the same as the timing at which the switching element 321 is turned on from off, but the present invention is not limited to this. The control unit 10 may provide a dead time during which both the switching elements 321 and 322 are turned off between the timing when the switching element 322 is turned off from on and the timing when the switching element 321 is turned on from off. Similarly, the control unit 10 provides a dead time during which both the switching elements 321 and 322 are turned off between the timing when the switching element 321 is turned off from on and the timing when the switching element 322 is turned on from off. good too.

When the polarity of the power supply voltage is positive, the control unit 10 turns on the switching element 311 when the absolute value of the power supply current Is becomes equal to or greater than the current threshold value Ith. After that, when the absolute value of the power supply current Is becomes smaller and the absolute value of the power supply current Is becomes smaller than the current threshold value Ith, the control unit 10 turns off the switching element 311 . Further, when the polarity of the power supply voltage is negative, the control unit 10 turns on the switching element 312 when the absolute value of the power supply current Is becomes equal to or greater than the current threshold value Ith. After that, when the absolute value of the power supply current Is becomes smaller and the absolute value of the power supply current Is becomes smaller than the current threshold value Ith, the control unit 10 turns off the switching element 312 .

When the absolute value of the power supply current Is is equal to or less than the current threshold Ith, the control unit 10 controls the switching element 311 and the switching element 321 of the upper switching element so as not to turn on at the same time, and also controls the switching element of the lower switching element. 312 and switching element 322 are controlled so as not to be turned on at the same time. Thereby, the control unit 10 can prevent a capacitor short circuit in the power conversion device 100 . The control unit 10 can improve the efficiency of the power conversion device 100 by turning on and off each switching element as shown in FIG.

FIG. 6 is a diagram showing an example of an AC current control method using the power supply short-circuit mode and the load power supply mode of the power converter 100 according to Embodiment 1. In FIG. FIG. 6 shows the waveform of the power supply voltage Vs, the waveform of the power supply current Is, The PWM signal and characteristics for switching element 321 are shown.

Passive control is the same control state as the example of FIG. 5 described above. In passive control, the control unit 10 does not turn on/off each switching element with a PWM signal. Passive control has less loss due to turning on and off of switching elements, but is inferior to other AC current control methods in suppressing harmonics.

The simple switching control is a control mode in which the control unit 10 implements the power supply short-circuit mode once or several times during the half cycle of the power supply. A feature of the simple switching control is that the number of times of switching is small, so that the switching loss is small. However, in the simple switching control, since the number of times of switching is small, it is difficult to control the alternating current waveform to be perfectly sinusoidal, so the improvement rate of the power factor is small.

Full PAM control is a control mode in which the control unit 10 continuously switches between the power supply short-circuit mode and the load power supply mode, and the switching frequency is several kHz or higher. A feature of full PAM control is that the power supply short-circuit mode and the load power supply mode are continuously switched, so that the power factor improvement rate is high. However, full PAM control has a large switching loss due to a large number of switching times. A common point of simple switching control and full PAM control is that the power factor can be improved compared to passive control.

An operation of switching between simple switching control and full PAM control when the control unit 10 performs power factor improvement control will be described. FIG. 7 is a first flow chart showing the control mode switching operation in the control unit 10 of the power converter 100 according to the first embodiment. As an example in FIG. 7 , the control unit 10 selects the control mode according to the input power Pin input from the AC power supply 1 to the power converter 100 . The control unit 10 can calculate the input power Pin using the power supply voltage Vs detected by the power supply voltage detection unit 5 and the power supply current Is detected by the power supply current detection unit 6 . Instead of the input power Pin, the control unit 10 controls parameters correlated with the input power Pin, such as the power supply voltage Vs, the power supply current Is, the bus voltage Vdc detected by the bus voltage detection unit 7, the power conversion device The control may be performed using the operating conditions of the load 50 of 100 or the like. That is, the control unit 10 may perform control according to a physical quantity or a value obtained from the physical quantity. Here, the physical quantity is, for example, the power supply voltage Vs, which is the input voltage from the AC power supply 1 to the power converter 100, or the power supply current Is, which is the input current, or the bus voltage Vdc, which is the output voltage from the power converter 100. is. Moreover, the value obtained from the physical quantity is, for example, the input power Pin from the AC power supply 1 to the power converter 100 . The same applies to the description of the subsequent flowcharts.

The control unit 10 compares the input power Pin with a predetermined threshold value Pin_th1 (step S1). When the input power Pin is greater than the threshold Pin_th1 (step S1: Yes), the control unit 10 compares the input power Pin with a predetermined threshold Pin_th2 (step S2). Note that threshold value Pin_th1<threshold value Pin_th2. When the input power Pin is greater than the threshold value Pin_th2 (step S2: Yes), the control unit 10 selects full PAM control as the power factor improvement control (step S3). For example, assume that the power conversion device 100 is installed in an air conditioner. Air conditioners require converter operation in consideration of breaker limits. In the air conditioner, as the load increases, the current flowing in the alternating current also increases. If the power factor of the air conditioner is poor, the alternating current will increase, and the breaker may trip, making it impossible to operate under heavy load conditions. Therefore, the power conversion device 100 performs full PAM control under the condition that the input power Pin becomes larger as in the case of being installed in an air conditioner.

When the input power Pin is equal to or less than the threshold Pin_th2 (step S2: No), that is, when the input power Pin is greater than the threshold Pin_th1 and equal to or less than the threshold Pin_th2, the control unit 10 selects simple switching control as the power factor improvement control (step S4). In this way, the control unit 10 determines the content of the power factor improvement control according to the input power Pin, that is, the physical quantity or the value obtained from the physical quantity.

When the input power Pin is equal to or less than the threshold value Pin_th1 (step S1: No), the control unit 10 stops the power factor improvement control (step S5). As described above, in the simple switching control and the full PAM control, the control unit 10 short-circuits the power source in the rectifier circuit 3, so the number of switching times increases and the switching loss due to the switching element increases. Under the condition that the input power Pin is small, the power factor improvement control is not necessary with the capacity of the breaker or the like. Performing power factor improvement control in a region where the input power Pin is small causes unnecessary loss. Therefore, the control unit 10 does not perform power factor improvement control in a region where the input power Pin is equal to or less than the threshold value Pin_th1. Threshold Pin_th1 and threshold Pin_th2 are set in advance by the user or the manufacturer of power conversion device 100 assuming the operation of load 50 connected to power conversion device 100 .

Note that FIG. 7 describes a case where the control unit 10 selects simple switching control or full PAM control as the power factor improvement control using two thresholds, but this is an example and the present invention is not limited to this. The control unit 10 may use one threshold to select only simple switching control or only full PAM control as power factor improvement control. The same applies to the description of the subsequent flowcharts.

Next, the relationship between the power supply short-circuit mode, the load power supply mode, and the synchronous rectification control in the power converter 100 will be described. In the example of the power supply short-circuit mode and the load power supply mode shown in FIG. 4, as described above, the switching elements indicated by the dotted line circles are the switching elements that are turned on to generate the power supply short-circuit path, Switching elements indicated by solid-line circles are switching elements that are turned on to perform synchronous rectification control. The example of FIG. 4 is based on the premise that the power conversion device 100 performs synchronous rectification control simultaneously with the power supply short-circuit mode or the load power supply mode. However, in the power conversion device 100, as shown in FIG. 8, it is also possible to perform control using diode rectification control together.

FIG. 8 is a diagram showing another example of paths of currents flowing through the power converter 100 according to the first embodiment. In FIG. 8, among the switching elements shown in FIG. 4, all the switching elements indicated by solid-line circles are in the OFF state. This is because when the switching element is a MOSFET, there is a conduction path using the parasitic diode of the MOSFET. As shown in FIG. 8, the control unit 10 can realize the power supply short-circuit mode and the load power supply mode even when all the switching elements other than the switching elements that perform power supply short-circuit switching are turned off. In this manner, the control unit 10 can cause the power converter 100 to operate as desired without necessarily performing synchronous rectification control in the circuit configuration as shown in FIG. FIG. 8 shows the switching pattern of each switching element under the condition that synchronous rectification control is completely stopped. can be controlled by

As shown in FIG. 6, in the power conversion device 100, at least one power supply short-circuit operation is required to perform power factor improvement control. In general, semiconductor device losses can be divided into conduction losses and switching losses. Conduction losses tend to increase in proportion to the magnitude of the current conducted through the semiconductor device or in proportion to the square of the magnitude of the current. The switching loss is determined by the product of the current and voltage in the overlapping section in the schematic diagram of the switching waveforms shown in FIG. FIG. 9 is a diagram for explaining switching loss generated in a general switching element used in the power converter 100 or the like according to the first embodiment. Ideally, the current _iD and the voltage _vDS applied to the switching element rise or fall vertically, but in practice, as shown in FIG. Occur.

From the operation waveforms shown in FIG. 5, when performing synchronous rectification control in passive control, the control unit 10 performs two switching operations per switching element during one cycle of the power supply, that is, one turn-on and one turn-off. conduct. In this case, the switching loss is very small and the conduction loss is dominant because switching is performed in a section in which the conduction current is small. On the other hand, when the simple switching control and the full PAM control shown in FIG. 6 are performed, the control unit 10 performs switching in a region where the power supply current Is and the power supply voltage Vs are high. Losses dominate. In particular, in the case of full PAM control, it can be said that this is remarkable because the number of times of switching is large. Therefore, if the conduction current, that is, the power supply current Is is assumed to be the same, the loss of the switching element is "passive control<simple switching control<full PAM control", and the heat generation of the switching element increases.

As described above, diodes and MOSFETs generally have temperature characteristics in which the voltage drop varies with temperature. This also applies to the parasitic diodes 311a, 312a, 321a, 322a and the switching elements 311, 312, 321, 322, which are MOSFETs, included in the rectifier circuit 3. FIG. 10 is a diagram showing temperature characteristics of a MOSFET, which is a switching element used in the rectifier circuit 3 of the power converter 100 according to the first embodiment. In FIG. 10, the horizontal axis indicates current, and the vertical axis indicates on-resistance. FIG. 10 shows the difference in on-resistance of the MOSFET depending on the temperature, showing that the higher the temperature, the higher the on-resistance, that is, the higher the voltage between the drain and the source. FIG. 11 is a diagram showing temperature characteristics of general diodes such as parasitic diodes used in the rectifier circuit 3 of the power converter 100 according to the first embodiment. In FIG. 11, the horizontal axis indicates forward voltage, and the vertical axis indicates current. FIG. 11 shows the difference in diode forward voltage drop with temperature, showing that the higher the temperature, the smaller the forward voltage drop.

From the contents shown in FIGS. 10 and 11, the power conversion device 100 selects diode rectification control under conditions where the temperature of the semiconductor device is high, for example, when performing power factor improvement control where the loss of the switching element increases. It is possible to operate with higher efficiency. That is, the control unit 10 of the power converter 100 performs switching as shown in FIG. 8 when performing power factor improvement control. As a result, the power converter 100 can be operated with high efficiency and high reliability.

On the other hand, the control unit 10 selects the synchronous rectification control shown in FIG. 4 when not performing the power factor improvement control. This is because in the rectifier circuit 3, the loss is smaller when the MOSFET is turned on rather than the diode. In addition, synchronous rectification control does not generate switching loss because it does not short-circuit the power supply, so it can reduce the loss compared to power factor improvement control that short-circuits the power supply.

FIG. 12 is a second flowchart showing the control mode switching operation in the control unit 10 of the power conversion device 100 according to the first embodiment. The flowchart shown in FIG. 12 is obtained by adding selection of diode rectification control and synchronous rectification control to the flowchart shown in FIG.

The control unit 10 compares the input power Pin and the threshold value Pin_th1 (step S11). If the input power Pin is greater than the threshold Pin_th1 (step S11: Yes), the control unit 10 compares the input power Pin and the threshold Pin_th2 (step S12). When the input power Pin is greater than the threshold value Pin_th2 (step S12: Yes), the control unit 10 selects full PAM control and diode rectification control as the power factor improvement control (step S13). When the input power Pin is equal to or less than the threshold Pin_th2 (step S12: No), that is, when the input power Pin is greater than the threshold Pin_th1 and equal to or less than the threshold Pin_th2, the control unit 10 selects simple switching control as the power factor improvement control, Diode rectification control is selected (step S14). Thus, the control unit 10 selects the diode rectification control when performing power factor improvement control, that is, when the input power Pin is greater than the threshold value Pin_th1.

When the input power Pin is equal to or less than the threshold value Pin_th1 (step S11: No), the control unit 10 stops power factor improvement control and selects synchronous rectification control (step S15). This is because, as described above, the switching loss is very small when the power factor improvement control is stopped, so the temperature rise of the semiconductor element is smaller than that during the power factor improvement control. The power conversion device 100 can operate more efficiently under synchronous rectification control in which power factor improvement control is stopped and the MOSFET is turned on.

In this way, when performing power factor improvement control, the control unit 10 causes the current from the AC power supply 1 to flow through the diode in the rectifier circuit 3 according to the input power Pin, that is, the physical quantity or the value obtained from the physical quantity. or switching element. Specifically, in the present embodiment, the control unit 10 controls the current from the AC power supply 1 to either the diode or the switching element in the rectifier circuit 3 according to the input power Pin, that is, the physical quantity or the value obtained from the physical quantity. is made to conduct through the diode in one or more of the sections through which the is allowed to conduct.

4 ( 4B), the section including the switching element 311 and the parasitic diode 311a of the switching element 311, and the section including the switching element 322 and the parasitic diode 322a of the switching element 322 in the case of FIG. Similarly, the section in which the current from the AC power supply 1 can flow through either the diode or the switching element in the rectifier circuit 3 is, for example, the path of the current flowing in the power conversion device 100 shown in FIG. A section including the switching element 321 and the parasitic diode 321a of the switching element 321 in the case of FIG. 4D, and a section including the switching element 312 and the parasitic diode 312a of the switching element 312 in the case of FIG. 4D.

Next, the hardware configuration of the control unit 10 included in the power converter 100 will be described. FIG. 13 is a diagram showing an example of a hardware configuration that implements the control unit 10 included in the power conversion device 100 according to Embodiment 1. As shown in FIG. The control unit 10 is realized by a processor 201 and a memory 202. FIG.

The processor 201 is a CPU (Central Processing Unit, central processing unit, processor, arithmetic unit, microprocessor, microcomputer, processor, DSP (Digital Signal Processor)), or system LSI (Large Scale Integration). The memory 202 is a non-volatile or volatile memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), EEPROM (Registered Trademark) (Electrically Erasable Programmable Read-Only Memory). can be exemplified. Moreover, the memory 202 is not limited to these, and may be a magnetic disk, an optical disk, a compact disk, a mini disk, or a DVD (Digital Versatile Disc).

As described above, according to the present embodiment, in the power conversion device 100, the control unit 10 considers the temperature characteristics of the diodes and MOSFETs that constitute the rectifier circuit 3, and when performing power factor improvement control, Diode rectification control was selected, and synchronous rectification control was selected when power factor improvement control was not performed. As a result, the control unit 10 does not need to add a dedicated temperature sensor or the like, so it is possible to suppress the increase in the size of the device, further suppress the occurrence of thermal runaway, and realize highly efficient operation with simple control. , It has the effect of

Embodiment 2.
In the first embodiment, the power conversion device 100 performs diode rectification control during power factor improvement control and performs control with a switching pattern in which synchronous rectification control is not performed. Embodiment 2 will explain an example of another switching pattern.

FIG. 14 is a diagram showing paths of currents flowing through the power converter 100 according to the second embodiment. FIG. 14 shows a switching pattern in which the control unit 10 performs synchronous rectification control on the switching elements 311 and 312 and does not perform synchronous rectification control on the switching elements 321 and 322 . The operation of the control unit 10 shown in FIG. 14 is such that the switching elements 321 and 322 that perform switching for short-circuiting the power supply do not perform synchronous rectification control, and the switching elements 311 and 312 that do not perform switching for short-circuiting the power supply perform synchronous rectification control. This is the operation to control. As described above, the switching elements 321 and 322 that perform switching for short-circuiting the power supply generate a large amount of heat due to a large switching loss during the power factor improvement control. On the other hand, the switching elements 311 and 312, which do not perform switching for short-circuiting the power supply, have very small switching loss and little heat generation from the above description of the synchronous rectification control. FIG. 14 shows a switching pattern in which the switching elements 321 and 322 that generate a large amount of heat are diode rectified and the switching elements 311 and 312 that generate a relatively small amount of heat are synchronously rectified. In the following description, the control of the switching pattern for each switching element as shown in FIG. 14 by the controller 10 is called partial synchronous rectification control.

FIG. 15 is a first flow chart showing the control mode switching operation in the control unit 10 of the power converter 100 according to the second embodiment. The flowchart shown in FIG. 15 is obtained by adding selection of partial synchronous rectification control and synchronous rectification control to the flowchart shown in FIG.

The control unit 10 compares the input power Pin and the threshold value Pin_th1 (step S21). When the input power Pin is greater than the threshold Pin_th1 (step S21: Yes), the control unit 10 compares the input power Pin and the threshold Pin_th2 (step S22). When the input power Pin is greater than the threshold value Pin_th2 (step S22: Yes), the control unit 10 selects full PAM control and partial synchronous rectification control as the power factor improvement control (step S23). When the input power Pin is equal to or less than the threshold Pin_th2 (step S22: No), that is, when the input power Pin is greater than the threshold Pin_th1 and equal to or less than the threshold Pin_th2, the control unit 10 selects simple switching control as the power factor improvement control, Partial synchronous rectification control is selected (step S24). In this way, the control unit 10 selects the partial synchronous rectification control when performing the power factor improvement control, that is, when the input power Pin is greater than the threshold value Pin_th1. When the input power Pin is equal to or less than the threshold value Pin_th1 (step S21: No), the control unit 10 stops power factor improvement control and selects synchronous rectification control (step S25).

Note that the control unit 10 may add a new threshold value Pin_th3 for selection of synchronous rectification control. FIG. 16 is a second flowchart showing the control mode switching operation in the control unit 10 of the power conversion device 100 according to the second embodiment. The flowchart shown in FIG. 16 indicates that the control unit 10 selects the partial synchronous rectification control when the input power Pin is greater than the threshold Pin_th3, and selects the synchronous rectification control when the input power Pin is equal to or less than the threshold Pin_th3. ing. Threshold value Pin_th3 is set in advance by the user or manufacturer of power conversion device 100 using the temperature characteristics shown in FIGS. 10 and 11 .

The control unit 10 compares the input power Pin and the threshold value Pin_th1 (step S31). When the input power Pin is greater than the threshold Pin_th1 (step S31: Yes), the control unit 10 compares the input power Pin and the threshold Pin_th3 (step S32). If the input power Pin is greater than the threshold Pin_th3 (step S32: Yes), the control unit 10 compares the input power Pin and the threshold Pin_th2 (step S33). When the input power Pin is greater than the threshold value Pin_th2 (step S33: Yes), the control unit 10 selects full PAM control and partial synchronous rectification control as the power factor improvement control (step S34). When the input power Pin is equal to or less than the threshold Pin_th2 (step S33: No), that is, when the input power Pin is greater than the threshold Pin_th3 and equal to or less than the threshold Pin_th2, the control unit 10 selects simple switching control as the power factor improvement control, Partial synchronous rectification control is selected (step S35). Thus, the control unit 10 selects partial synchronous rectification control when performing power factor improvement control, that is, when the input power Pin is greater than the threshold value Pin_th3.

When the input power Pin is equal to or less than the threshold Pin_th3 (step S32: No), that is, when the input power Pin is greater than the threshold Pin_th1 and equal to or less than the threshold Pin_th3, the control unit 10 selects simple switching control as the power factor improvement control, Synchronous rectification control is selected (step S36). When the input power Pin is equal to or less than the threshold value Pin_th1 (step S31: No), the control unit 10 stops the power factor improvement control and selects the synchronous rectification control (step S37).

FIG. 17 is a diagram schematically showing losses in MOSFETs and diodes, which are switching elements used in the rectifier circuit 3 of the power converter 100 according to the second embodiment. FIG. 17 shows the difference between the loss at room temperature and the loss at high temperature. A normal temperature is generally 25°C, and a high temperature is a temperature higher than 25°C. The drain-source voltage of a MOSFET is expressed as an on-resistance, and the loss is a characteristic proportional to the square of the conduction current. On the other hand, the forward voltage drop of the diode is almost constant once the current starts to flow, and the loss is proportional to the conduction current. Here, the MOSFET and diode losses each have a crosspoint with respect to the conduction current. In the example of FIG. 17, the cross-point current at room temperature is I3, and the cross-point current at high temperature is I2. In FIG. 17, the magnitude relationship between the current I3 and the current I2 is I3>I2 in relation to the temperature characteristics shown in FIGS. Therefore, the power conversion device 100 can be operated with high efficiency when the current is higher than or equal to I2 at a high temperature and the current flows through the diode. Therefore, in the power converter 100, when the operation of the flowchart shown in FIG. 16 is performed, the threshold Pin_th3, which is the input power corresponding to the current I2 in FIG. 17, is set in advance.

Here, in the flowchart shown in FIG. 16, the control unit 10 selects the partial synchronous rectification control when the input power Pin is equal to or greater than the threshold value Pin_th3. This is because, as described above, the switching elements 321 and 322 that perform switching for short-circuiting the power supply have a large number of switching times, and thus have a large loss compared to the switching elements 311 and 312 that do not perform switching for short-circuiting the power supply. , the temperature rise also increases according to the loss. FIG. 18 schematically shows this state. FIG. 18 is a diagram schematically showing the loss of each switching element and parasitic diode used in the rectifier circuit 3 of the power converter 100 according to the second embodiment. In FIG. 18, the cross points of the losses of the switching elements 311, 312, 321 and 322 which are MOSFETs and the losses of the parasitic diodes 311a, 312a, 321a and 322a are compared. As shown in FIG. 18, the current I22x, which is the cross point of the losses of the switching elements 321 and 322 and the losses of the parasitic diodes 321a and 322a, is expressed by The current I21x, which is the point, increases. This is because the switching elements 321 and 322 generate more heat due to switching loss than the switching elements 311 and 312, as described above. That is, the optimum point of whether to perform diode rectification control or synchronous rectification control changes depending on whether or not switching for power supply short-circuiting is performed. Therefore, the power conversion device 100 can realize a more highly efficient operation by performing the partially synchronous rectification control as shown in FIG. 14 .

In the operation of the flowchart shown in FIG. 16, the control unit 10 additionally sets the threshold value Pin_th3 by limiting the selection to the synchronous rectification control and the partial synchronous rectification control, but it is also possible to select the diode rectification control as well. . FIG. 19 is a third flow chart showing the control mode switching operation in the control unit 10 of the power converter 100 according to the second embodiment. The flowchart shown in FIG. 19 indicates that the control unit 10 selects diode rectification control when the input power Pin is greater than the threshold value Pin_th4. As for threshold Pin_th4, the user or manufacturer of power conversion device 100 previously sets the input power corresponding to current I21x in FIG. 18 as threshold Pin_th4 using the temperature characteristics shown in FIGS. put.

The control unit 10 compares the input power Pin and the threshold value Pin_th1 (step S41). If the input power Pin is greater than the threshold Pin_th1 (step S41: Yes), the control unit 10 compares the input power Pin and the threshold Pin_th3 (step S42). When the input power Pin is greater than the threshold Pin_th3 (step S42: Yes), the control unit 10 compares the input power Pin and the threshold Pin_th2 (step S43). When the input power Pin is greater than the threshold Pin_th2 (step S43: Yes), the control unit 10 compares the input power Pin and the threshold Pin_th4 (step S44). When the input power Pin is greater than the threshold value Pin_th4 (step S44: Yes), the control unit 10 selects full PAM control and diode rectification control as the power factor improvement control (step S45).

When the input power Pin is equal to or less than the threshold Pin_th4 (step S44: No), that is, when the input power Pin is greater than the threshold Pin_th2 and equal to or less than the threshold Pin_th4, the control unit 10 selects full PAM control as the power factor improvement control, Partial synchronous rectification control is selected (step S46). When the input power Pin is equal to or less than the threshold Pin_th2 (step S43: No), that is, when the input power Pin is greater than the threshold Pin_th3 and equal to or less than the threshold Pin_th2, the control unit 10 selects simple switching control as the power factor improvement control, Partial synchronous rectification control is selected (step S47). When the input power Pin is equal to or less than the threshold Pin_th3 (step S42: No), that is, when the input power Pin is greater than the threshold Pin_th1 and equal to or less than the threshold Pin_th3, the control unit 10 selects simple switching control as the power factor improvement control, Synchronous rectification control is selected (step S48). When the input power Pin is equal to or less than the threshold value Pin_th1 (step S41: No), the control unit 10 stops power factor improvement control and selects synchronous rectification control (step S49).

It should be noted that the flowcharts shown in FIGS. 15, 16, and 19 are examples, and the combination of power factor improvement control, synchronous rectification control, partially synchronous rectification control, and diode rectification control may be can be freely set by the user.

As described above, according to the present embodiment, in the power converter 100, the control unit 10 considers the individual temperature characteristics of the diodes and MOSFETs that make up the rectifier circuit 3 when performing power factor improvement control. Then, it was decided whether to conduct the current through the diode or through the switching element, which is a MOSFET. Specifically, based on the result of comparing the input power Pin, that is, the physical quantity or a value obtained from the physical quantity with the threshold value, the control unit 10 causes the diode or the switching element in the rectifier circuit 3 to receive the power from the AC power supply 1. A section through which a diode is allowed to flow is determined among the sections through which current can flow. In addition, the control unit 10 passes the current from the AC power supply 1 to either the diode or the switching element in the rectifier circuit 3 based on the result of comparing the input power Pin, that is, the physical quantity or the value obtained from the physical quantity with the threshold. In sections where current can flow, the diode is made to conduct. As a result, the control unit 10 has the effect of being able to realize a more efficient operation than in the first embodiment.

Embodiment 3.
In the third embodiment, the control of the control unit 10 considering the arrangement positions of the switching elements in the power conversion device 100 will be described.

As described above, the power conversion device 100 is mounted on a domestic air conditioner. Generally, an air conditioner includes a heat sink for dissipating heat from heat-generating components. Air conditioners often employ a structure in which a single heat sink cools a plurality of semiconductor elements, which are heat-generating components, in consideration of material costs, processing costs, installation restrictions, and the like. Therefore, as a path for heat transfer of the loss generated from the semiconductor element, a path between switching elements via a heat sink can be considered in addition to the path for dissipating heat into the air.

FIG. 20 is a diagram showing an example of heat dissipation of switching elements when power converter 100 according to Embodiment 3 is mounted in an air conditioner. FIG. 20 shows an example in which four switching elements 311 , 312 , 321 and 322 are attached to one heat sink 701 . As described above, the switching elements 321 and 322 that perform switching for short-circuiting the power supply have large switching losses. Therefore, the temperature of the switching elements 311 and 312, which do not perform switching for short-circuiting the power supply, is likely to rise due to the amount of heat generated by the switching elements 321 and 322 in addition to the self loss.

As described above, according to the present embodiment, in power conversion device 100, control unit 10 performs power factor improvement control when each switching element is installed on common heat sink 701 as shown in FIG. Under these conditions, all switching elements are diode rectified. That is, when the switching elements are installed on the common heat sink 701, the control unit 10 controls the diode or the switching element in the rectifier circuit 3 in the section where the current from the AC power supply 1 can flow. flow to Thereby, the control unit 10 can ensure reliability in the operation of the power converter 100 .

Embodiment 4.
Embodiment 4 describes a motor drive device including the power conversion device 100 described in Embodiments 1 to 3. FIG.

FIG. 21 is a diagram showing a configuration example of the motor drive device 101 according to the fourth embodiment. A motor drive device 101 drives a motor 42 as a load. The motor drive device 101 includes the power conversion device 100 of Embodiments 1 to 3, an inverter 41 , a motor current detection section 44 and an inverter control section 43 . The inverter 41 converts the DC power supplied from the power conversion device 100 into AC power and outputs the AC power to the motor 42 to drive the motor 42 . An example in which the load of the motor drive device 101 is the motor 42 has been described, but this is only an example, and the device connected to the inverter 41 may be a device to which AC power is input. Other equipment may be used.

The inverter 41 is a circuit in which switching elements such as IGBTs (Insulated Gate Bipolar Transistors) are configured in a three-phase bridge configuration or a two-phase bridge configuration. The switching elements used in inverter 41 are not limited to IGBTs, and may be switching elements made of WBG semiconductors, IGCTs (Integrated Gate Commutated Thyristors), FETs (Field Effect Transistors), or MOSFETs.

A motor current detector 44 detects a current flowing between the inverter 41 and the motor 42 . The inverter control unit 43 uses the current detected by the motor current detection unit 44 to generate a PWM signal for driving the switching elements in the inverter 41 so that the motor 42 rotates at a desired rotation speed. is applied to the inverter 41. The inverter control unit 43 is realized by a processor and memory, like the control unit 10 . Note that the inverter control unit 43 of the motor drive device 101 and the control unit 10 of the power conversion device 100 may be realized by one circuit.

When the power conversion device 100 is used in the motor driving device 101 , the bus voltage Vdc necessary for controlling the rectifier circuit 3 changes according to the operating state of the motor 42 . In general, the higher the rotation speed of the motor 42, the higher the output voltage of the inverter 41 needs to be. The upper limit of the output voltage of the inverter 41 is limited by the input voltage to the inverter 41, that is, the bus voltage Vdc which is the output of the power converter 100. FIG. A region where the output voltage from the inverter 41 exceeds the upper limit limited by the bus voltage Vdc and saturates is called an overmodulation region.

In such a motor driving device 101, it is not necessary to boost the bus voltage Vdc in the low rotation range of the motor 42, that is, in the range in which the overmodulation region is not reached. On the other hand, when the motor 42 rotates at a high speed, the overmodulation region can be shifted to a higher speed side by increasing the bus voltage Vdc. As a result, the operating range of the motor 42 can be expanded to the high rotation side.

Also, if it is not necessary to expand the operating range of the motor 42, the number of windings on the stator of the motor 42 can be increased accordingly. By increasing the number of turns of the windings, the motor voltage generated across the windings increases in the low rotation region, and the current flowing through the windings decreases accordingly. can reduce the loss caused by The number of turns of the windings of the motor 42 is set to an appropriate value in order to obtain both the effects of expanding the operating range of the motor 42 and improving the loss in the low rotation region.

As described above, according to the present embodiment, by using the power conversion device 100, uneven heat generation between arms can be reduced, and the motor drive device 101 with high reliability and high output can be realized.

Embodiment 5.
Embodiment 5 describes an air conditioner provided with motor drive device 101 described in Embodiment 4. FIG.

FIG. 22 is a diagram showing a configuration example of an air conditioner 700 according to Embodiment 5. As shown in FIG. Air conditioner 700 is an example of a refrigeration cycle device, and includes motor drive device 101 and motor 42 of the fourth embodiment. The air conditioner 700 includes a compressor 81 incorporating a compression mechanism 87 and a motor 42, a four-way valve 82, an outdoor heat exchanger 83, an expansion valve 84, an indoor heat exchanger 85, and a refrigerant pipe 86. . The air conditioner 700 is not limited to a separate type air conditioner in which the outdoor unit is separated from the indoor unit, and may be one in which the compressor 81, the indoor heat exchanger 85, and the outdoor heat exchanger 83 are provided in one housing. A body type air conditioner may be used. The motor 42 is driven by a motor drive device 101 .

A compression mechanism 87 that compresses refrigerant and a motor 42 that operates the compression mechanism 87 are provided inside the compressor 81 . The refrigerant circulates through the compressor 81, the four-way valve 82, the outdoor heat exchanger 83, the expansion valve 84, the indoor heat exchanger 85, and the refrigerant pipe 86, thereby forming a refrigeration cycle. It should be noted that the components included in air conditioner 700 can also be applied to devices such as refrigerators or freezers that include a refrigeration cycle.

Further, in the present embodiment, a configuration example in which the motor 42 is used as the drive source of the compressor 81 and the motor 42 is driven by the motor drive device 101 has been described. However, the motor 42 may be applied to the drive source for driving the indoor unit fan and the outdoor unit fan (not shown) provided in the air conditioner 700 and the motor 42 may be driven by the motor drive device 101 . Alternatively, the motor 42 may be applied to the driving source of the indoor blower, the outdoor blower, and the compressor 81 , and the motor 42 may be driven by the motor driving device 101 .

In addition, in the air conditioner 700, the intermediate condition in which the output is less than half the rated output, that is, the operation under the low output condition is dominant throughout the year. Become. Further, in the air conditioner 700, the rotational speed of the motor 42 tends to be low, and the bus voltage Vdc required to drive the motor 42 tends to be low. Therefore, it is effective in terms of system efficiency to operate the switching elements used in air conditioner 700 in a passive state. Therefore, the power conversion device 100 capable of reducing loss in a wide range of operation modes from passive state to high frequency switching state is useful for the air conditioner 700. As described above, the reactor 2 can be made smaller in the interleaved method, but since the air conditioner 700 is often operated under intermediate conditions, it is not necessary to make the reactor 2 smaller. However, it is effective in terms of harmonic suppression and power supply power factor.

In addition, since the power conversion device 100 can suppress switching loss, the temperature rise of the power conversion device 100 is suppressed. Cooling capacity can be secured. Therefore, the power conversion device 100 is highly efficient and suitable for the air conditioner 700 with a high output of 4.0 kW or more.

In addition, according to the present embodiment, the use of the power conversion device 100 reduces uneven heat generation between the arms. Weight gain can be suppressed. Further, according to the present embodiment, switching loss is reduced by high-frequency driving of the switching elements, the energy consumption rate is low, and highly efficient air conditioner 700 can be realized.

The configuration shown in the above embodiment shows an example of the content of the present invention, and it is possible to combine it with another known technology, and one configuration can be used without departing from the scope of the present invention. It is also possible to omit or change the part.

Reference Signs List 1 AC power supply 2 Reactor 3 Rectifier circuit 4 Smoothing capacitor 5 Power supply voltage detection unit 6 Power supply current detection unit 7 Bus voltage detection unit 10 Control unit 31 First arm 32 Second arm 41 Inverter 42 Motor 43 Inverter control unit 44 Motor current detection unit 50 Load 81 Compressor 82 Four-way valve 83 Outdoor heat exchanger 84 Expansion valve 85 Indoor heat exchanger 86 Refrigerant pipe 87 Compression mechanism , 100 power conversion device 101 motor drive device 201 processor 202 memory 311, 312, 321, 322 switching elements 311a, 312a, 321a, 322a parasitic diodes 321b, 322b diodes 501 first wiring 502 second 2 wiring 503 third wiring 504 fourth wiring 506 first connection point 508 second connection point 600 semiconductor substrate 601, 603 region 602 oxide insulating film 604 channel 700 air conditioner machine, 701 heat sink.

Claims (5)

a reactor having a first end and a second end, the first end being connected to an AC power source;
The alternating current output from the alternating current power supply is connected to the second end of the reactor and includes two arms in which two switching elements having diodes connected in parallel are connected in series, and the two arms are connected in parallel. a rectifier circuit that converts the voltage to a DC voltage;
a smoothing capacitor connected in parallel to the two arms included in the rectifier circuit;
a detection unit that detects a physical quantity indicating the operating state of the rectifier circuit;
with
Of the two arms included in the rectifier circuit, the first arm is connected to the AC power supply via the reactor by a wiring provided between the two switching elements, and the second arm is connected to the two switching elements. wiring provided between switching elements is connected to the AC power supply without passing through the reactor;
Based on the result of comparing the physical quantity or a value obtained from the physical quantity with three thresholds, it is possible to cause current from the AC power supply to flow through either the diode or the switching element in the rectifier circuit. In the interval
When the physical quantity or the value obtained from the physical quantity is equal to or lower than the smallest first threshold, the power factor improvement control is stopped, and the rectifier circuit performs synchronous rectification control in which the current from the AC power supply flows through the switching element. do,
When the physical quantity or a value obtained from the physical quantity is larger than the first threshold and is equal to or smaller than a second threshold, which is the next smallest to the first threshold, the switching element of the second arm is supplied with the alternating current Forming a power supply short-circuit path in which current from a power supply flows in the order of the reactor, the rectifier circuit, and the AC power supply, or a power supply short-circuit path in which the current from the AC power supply flows in the order of the rectifier circuit, the reactor, and the AC power supply. performing simple switching control for performing a power supply short-circuit mode once or a specified number of times during a half cycle of the power supply voltage supplied from the AC power supply, and performing the synchronous rectification control,
When the physical quantity or the value obtained from the physical quantity is greater than the second threshold and is equal to or less than the third threshold, which is the next smallest to the second threshold, the simple switching control is performed, and the first arm is performing the synchronous rectification control with the second arm, and performing partial synchronous rectification control for performing diode rectification control for causing the current from the AC power supply to flow through the diode for the second arm,
When the physical quantity or the value obtained from the physical quantity is greater than the third threshold value, the current from the power supply short-circuit mode and the AC power supply is transferred to the switching element of the second arm from the rectifier circuit to the smoothing capacitor. A power conversion device that continuously performs Pulse Amplitude Modulation control for continuously switching the load power supply mode to be supplied to the power converter and performs the partial synchronous rectification control. a reactor having a first end and a second end, the first end being connected to an AC power source;
The alternating current output from the alternating current power supply is connected to the second end of the reactor and includes two arms in which two switching elements having diodes connected in parallel are connected in series, and the two arms are connected in parallel. a rectifier circuit that converts the voltage to a DC voltage;
a smoothing capacitor connected in parallel to the two arms included in the rectifier circuit;
a detection unit that detects a physical quantity indicating the operating state of the rectifier circuit;
with
Of the two arms included in the rectifier circuit, the first arm is connected to the AC power supply via the reactor by a wiring provided between the two switching elements, and the second arm is connected to the two switching elements. wiring provided between switching elements is connected to the AC power supply without passing through the reactor;
Based on the result of comparing the physical quantity or a value obtained from the physical quantity with four thresholds, current from the AC power supply can be caused to flow through either the diode or the switching element in the rectifier circuit. In the interval
When the physical quantity or the value obtained from the physical quantity is equal to or lower than the smallest first threshold, the power factor improvement control is stopped, and the rectifier circuit performs synchronous rectification control in which the current from the AC power supply flows through the switching element. do,
When the physical quantity or a value obtained from the physical quantity is larger than the first threshold and is equal to or smaller than a second threshold, which is the next smallest to the first threshold, the switching element of the second arm is supplied with the alternating current Forming a power supply short-circuit path in which current from a power supply flows in the order of the reactor, the rectifier circuit, and the AC power supply, or a power supply short-circuit path in which the current from the AC power supply flows in the order of the rectifier circuit, the reactor, and the AC power supply. performing simple switching control for performing a power supply short-circuit mode once or a specified number of times during a half cycle of the power supply voltage supplied from the AC power supply, and performing the synchronous rectification control,
When the physical quantity or the value obtained from the physical quantity is greater than the second threshold and is equal to or less than the third threshold, which is the next smallest to the second threshold, the simple switching control is performed, and the first arm is performing the synchronous rectification control with the second arm, and performing partial synchronous rectification control for performing diode rectification control for causing the current from the AC power supply to flow through the diode for the second arm,
When the physical quantity or a value obtained from the physical quantity is larger than the third threshold and is equal to or smaller than a fourth threshold, which is the next smallest to the third threshold, the power supply is short-circuited to the switching element of the second arm. Continuously performing Pulse Amplitude Modulation control for continuously switching the mode and the load power supply mode in which the current from the AC power supply flows from the rectifier circuit to the smoothing capacitor, and performing the partial synchronous rectification control,
When the physical quantity or a value obtained from the physical quantity is greater than the fourth threshold, the pulse amplitude modulation control is continuously performed, and the diode causes current from the AC power supply to flow through the diode in the rectifier circuit. A power conversion device that performs rectification control. The physical quantity is the input voltage or input current from the AC power supply to the power conversion device, or the output voltage from the power conversion device, and the value obtained from the physical quantity is the value from the AC power supply to the power conversion device. 3. The power converter according to claim 1 or 2, wherein the input power is A motor drive device for driving a motor,
A power converter according to any one of claims 1 to 3;
an inverter that converts the DC power output from the power conversion device into AC power and outputs the AC power to the motor;
A motor drive device comprising: a motor;
a motor driving device according to claim 4;
air conditioner.

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