JP2002027758A - Power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply capable of improving power factor while minimizing the drop of conversion efficiency and of effectively removing harmonic components contained in an input current. SOLUTION: This power supply is provided with a first input rectifier circuit 10 that rectifies the input voltage Vin supplied from an AC power supply 1, a transformer 41 that receives the output from the circuit 10 at primary windings 43, an output rectifier circuit 50 that filters the output from the secondary windings 43 of the transformer 41, and a voltage-booster circuit 30 that raises the voltage of the primary windings 42 of the transformer 41. This structure enables the drop of the conversion efficiency to be minimized by the presence of the circuit 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply, and more particularly, to a power supply for converting an AC voltage to a DC voltage.

[0002]

2. Description of the Related Art A capacitor-input rectifier is widely used as a power supply circuit for obtaining a DC voltage from an AC voltage such as a commercial power supply.

A typical circuit diagram of a capacitor input type rectifier circuit is described, for example, in FIG. 5 of Japanese Patent Application Laid-Open No. 4-138506. As described in the publication, in the capacitor-input rectifier circuit, an input smoothing capacitor is inserted between both output terminals of the input rectifying diode, and the output voltage from the input rectifying diode is output by the input smoothing capacitor. The pulsation is smoothed.

However, in the capacitor-input rectifier circuit, the input current becomes a pulse current that flows for a very short time every half cycle of the input voltage, and contains many harmonic components. For this reason, the power factor is extremely low, voltage distortion occurs, and reactive power increases, which adversely affects power supply equipment.

[0005]

In order to solve such a problem, there has been proposed a method of inserting a booster circuit between an input rectifier diode and an input smoothing capacitor (see FIG. 8 of the publication). . According to this method, the power factor can be brought close to 1, but there is a problem that the conversion efficiency is reduced due to the loss of the booster circuit.

On the other hand, there has been proposed a method in which an input smoothing capacitor is not provided at a stage subsequent to the input rectifier diode, and the two output terminals of the input rectifier diode are directly connected to the primary winding of a high-frequency transformer via a switching transistor. (See FIG. 1 of the publication). According to this method, the power factor can be improved by optimally controlling the conduction / non-conduction of the switching transistor. However, when the input voltage is low, the input current does not flow. I can't. Another problem is that harmonic components contained in the input current cannot be effectively removed.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a power supply device with an improved power factor and capable of effectively removing harmonic components contained in an input current while minimizing a decrease in conversion efficiency. That is.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
A first input rectifier for rectifying an input voltage supplied from an AC power supply, a transformer receiving an output from the first input rectifier in a primary winding, and an output from a secondary winding of the transformer. An output rectifier circuit for smoothing, and boosting means for boosting a voltage of the primary winding of the transformer in response to an instantaneous value of the input voltage supplied from the AC power supply being equal to or less than a predetermined voltage. This is achieved by a power supply device having:

According to the present invention, the voltage of the primary winding of the transformer is boosted in response to the instantaneous value of the input voltage being equal to or lower than the predetermined voltage. In some cases, such boosting is not performed, so that when the instantaneous value of the input voltage is equal to or higher than a predetermined voltage, the input current supplied from the AC power flows into the primary winding of the transformer without passing through the boosting means. Therefore, it is possible to minimize a decrease in the conversion efficiency due to the intervening step-up means.

In a preferred embodiment of the present invention, a turn ratio of the primary winding to the secondary winding of the transformer is 1: n, and the predetermined voltage is output from the output rectifier circuit. Output voltage divided by n.

According to the preferred embodiment of the present invention, the predetermined voltage is defined by the voltage obtained by dividing the output voltage output from the output rectifier circuit by n. In response to the region in which no current flows in the next winding, the boosting by the boosting means is performed. Therefore, even when the instantaneous value of the input voltage is reduced and the current does not flow through the primary winding of the transformer, the input current can always flow from the AC power supply. As a result, the input current waveform is input. It is possible to match the voltage waveform. Thereby, the power factor can be improved.

In a further preferred aspect of the present invention, the boosting means boosts an output from the second input rectifying means and a second input rectifying means for rectifying the input voltage. A booster circuit for supplying the primary winding.

In a further preferred aspect of the present invention, the apparatus further comprises switch means for setting a voltage waveform of the primary winding of the transformer to a pulse waveform.

In a further preferred aspect of the present invention, a control signal having a sinusoidal waveform synchronized with a phase of the AC power supply is generated based on at least one of an output voltage and an output current output from the output rectifier circuit. A sine wave generating means, a current detecting means for detecting a current flowing through the primary winding of the transformer, and a current waveform of the current detected by the current detecting means generated by the sine wave generating means. Control means for controlling switching of the switch means so as to match a waveform of the control signal.

According to a further preferred embodiment of the present invention, since the current waveform of the current flowing through the primary winding of the transformer has a sine wave shape, it is possible to make the waveform of the input current coincide with the waveform of the input voltage. . Thereby, the power factor can be improved. Further, since the current waveform of the current flowing through the primary winding of the transformer is determined based on at least one of the output voltage and the output current output from the output rectifier circuit, the output voltage output from the output rectifier circuit is kept constant. In either case, when it is desired to keep the output current output from the output rectifier circuit constant, or when it is desired to keep the output power output from the output rectifier circuit constant, Switching can be performed.

In a further preferred aspect of the present invention, a harmonic component is included in a sine wave waveform of the control signal generated by the sine wave generating means.

[0017] In a further preferred aspect of the present invention, the sine wave generating means responds when at least one of an output voltage, an output current and an output power output from the output rectifier circuit is larger than a desired value. Decreasing the amplitude of the control signal and increasing the amplitude of the control signal in response to being less than a desired value.

In a further preferred aspect of the present invention, the control means includes a comparison means for comparing the current detected by the current detection means with the control signal supplied from the sine wave generation means, The switching of the switch means is controlled at least in response to a result of the comparison by the comparison means.

In a further preferred aspect of the present invention, the control means keeps at least one of an output voltage, an output current and an output power output from the output rectifier circuit substantially constant, and The waveform of the input current supplied therefrom is sinusoidal.

In a further preferred aspect of the present invention, the control means includes an oscillator for generating an oscillation signal and one of the states in response to the oscillation signal, and the other in response to a comparison result by the comparison means. And a switching circuit for controlling the switching means based on the state of the latch circuit.

[0021]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a circuit diagram showing a power supply device according to a preferred embodiment of the present invention.

As shown in FIG. 1, the power supply device according to this embodiment includes a first input rectifier circuit 10, a second input rectifier circuit 20, a booster circuit 30, a switch circuit 40
, An output rectifier circuit 50, and a control unit 60.

The first input rectifier circuit 10 is composed of four diodes 11 to 14,
The cathodes of 1 and 12 are commonly connected and connected to a signal line X1, and the anodes of the diodes 13 and 14 are commonly connected and connected to a signal line X2. An anode of the diode 11 and a cathode of the diode 13 are commonly connected to an input terminal IN1 to which one end of the AC power supply 1 is connected via an input filter 2, and an anode of the diode 12 and a cathode of the diode 14 are connected to the input filter. 2 is commonly connected to an input terminal IN2 to which the other end of the AC power supply 1 is connected. The AC power supply 1 connected between the input terminals IN1 and IN2 is a power supply that supplies an input voltage Vin and an input current Iin to the power supply device according to the present embodiment, and is, for example, a commercial power supply. The first input rectifier circuit 10 having such a configuration receives the input voltage Vin supplied from the AC power supply 1 via the input filter 2, and performs full-wave rectification of the input voltage Vin.

The second input rectifier circuit 20 is composed of two diodes 21 and 22, and the cathodes of the diodes 21 and 22 are commonly connected and connected to a signal line X3. The anode of the diode 21 is
The input terminal IN2 is connected via the input filter 2, and the anode of the diode 22 is connected via the input filter 2 to the input terminal IN1. The second input rectifier circuit 20 having such a configuration receives the input voltage Vin supplied from the AC power supply 1 via the input filter 2, and performs full-wave rectification of the input voltage Vin.

The booster circuit 30 includes an inductor 31, a switch element 32 composed of a field effect transistor, a diode 33, a capacitor 34, and a current detection element 35. One end of the inductor 31 is connected to the signal line X3, and the other end is connected to the anode of the diode 33. The cathode of the diode 33 is connected to the signal line X.
1 connected. The switch element 32 has one end connected to a node between the inductor 31 and the anode of the diode 33, and the other end connected to the signal line X2. Further, the capacitor 34 is connected between the cathode of the diode 33 and the signal line X2. Since the capacitor 34 is used as a high frequency filter, its capacitance value may be small. For this reason, the capacitor 34 does not have a sufficient smoothing action in the frequency band of the commercial power supply. Further, the current detection element 35 is connected to the switch element 3 of the signal line X2.
2 is connected between the other end of the second and the common anode of the diodes 13 and 14 included in the first input rectifier circuit 10, and detects a current Ia flowing therethrough. The booster circuit 30 having such a configuration receives the pulsating current supplied from the signal line X3, which is the output signal line of the second input rectifying circuit 20, and boosts the pulsating flow, thereby increasing the first input rectifying circuit 10 The voltage of the signal line X1 which is the output signal line is increased.

The switch circuit 40 includes a high-frequency transformer 41
And a switch element 44 comprising a field effect transistor
And a current detection element 45. The high frequency transformer 41 includes a primary winding 42 having a turn ratio of 1: n.
And one end of the primary winding 42 is connected to the signal line X1 and the other end is connected to one end of the switch element 44. The other end of the switch element 44 is connected to the signal line X2. Further, the current detection element 45
Of the signal line X2, a current I connected between the other end of the switch element 44 and the other end of the switch element 32 and flowing therethrough.
c is detected. Switch circuit 4 having such a configuration
0 sets the power waveform appearing on the signal line X1 as a pulse waveform by switching the switch element 44.

The output rectifier circuit 50 includes two diodes 5
1 and 52, an inductor 53, a capacitor 54,
The current detecting element 55 is included. The diode 51 has an anode connected to the secondary winding 4 of the high-frequency transformer 41.
3, and the cathode is connected to one end of the inductor 53. The diode 52 has an anode connected to the other end of the secondary winding 43 of the high-frequency transformer 41 and a cathode connected to one end of the inductor 53. The capacitor 54 has one end connected to the other end of the inductor 53,
The other end is connected to the anode of the diode 52. One end of the capacitor 54 is connected to an output terminal OUT1 to which one end of the load 3 is connected, and the other end of the capacitor 54 is connected to an output terminal OUT2 to which the other end of the load 3 is connected. Further, the current detection element 55 is connected to the output terminal OUT
2 and the other end of the capacitor 54, and detects a current Iout flowing therethrough. The output rectifier circuit 50 having such a configuration smoothes the pulse waveform of the output from the switch circuit 40 and converts the pulse waveform into a direct current.

The control unit 60 includes three control circuits 61 to 63
, A pulse transformer 64, and a zero-cross detection circuit 65. The control circuit 61 has input terminals a, b
, C and an output terminal d, an input terminal a is supplied with a voltage Va appearing on the signal line X3, an input terminal b is supplied with information indicating a current Ia detected by the current detection element 35,
The input terminal c is supplied with a voltage Vb appearing on the signal line X1. Further, a control signal for controlling the switching of the switch element 32 is output from the output terminal d. Control circuit 62
Has input terminals e, f, and g and an output terminal h. The input terminal e is supplied with information indicating the current Iout detected by the current detecting element 55, and the input terminal f has a voltage appearing on the output terminal OUT1. Vout is supplied, and an output signal output from an output terminal o of the zero-cross detection circuit 65 is supplied to an input terminal g. Also, from the output terminal h, the control signal cntl
Is output. The control circuit 63 has input terminals i and j and an output terminal k. A control signal cntl is supplied to the input terminal i, and information indicating the current Ic detected by the current detecting element 45 is supplied to the input terminal j. You. Further, a control signal for controlling the switching of the switch element 44 is output from the output terminal k via the pulse transformer 64. The zero-cross detection circuit 65 has input terminals l and m and an output terminal o. The input terminal l is connected via an input filter 2 to an input terminal IN1 to which one end of the AC power supply 1 is connected. The input terminal m is similarly connected to an input terminal IN2 to which the other end of the AC power supply 1 is connected via an input filter 2. Further, a zero-cross detection signal zero is output from the output terminal o every time the input voltage Vin supplied from the AC power supply 1 connected between the input terminals IN1 and IN2 crosses the zero voltage, and as described above, the control circuit 62 is supplied to an input terminal g. The control unit 60 having such a configuration controls the operation of the entire power supply device according to the present embodiment, and controls the output voltage V
Out is stabilized and the current waveform of the input current Iin is shaped into a sine wave to improve the power factor.

FIG. 2 is a block diagram showing a circuit configuration of the control circuit 61.

As shown in FIG. 2, the control circuit 61
Multiplier 71, comparator 72, oscillator 73, R
An S latch circuit 74 is included.

The oscillator 73 has a predetermined frequency, for example, 10
A circuit for generating a triangular wave having a frequency of 0 kHz to 200 kHz.
4 set input terminal (S). Multiplier 71
Receives the voltage Va supplied from the input terminal a and the voltage Vb supplied from the input terminal c, performs necessary operations on these, and supplies the result to the inverting input terminal (-) of the comparator 72. The information indicating the current Ia supplied from the input terminal b is input to the non-inverting input terminal (+) of the comparator 72. The comparator 72 compares the operation result of the multiplier 71 with information indicating the current Ia, and
Is supplied to the reset input terminal (R) of the RS latch circuit 74 in response to the fact that the information indicating the value exceeds the operation result of the multiplier 71. RS latch circuit 74
Sets the level of the signal output from the output terminal (Q) to low level in response to the signal supplied to the reset input terminal (R) being high level, and is supplied to the set input terminal (S). The level of the signal output from the output terminal (Q) in response to the high level of the signal is set to the high level.

The control circuit 61 having such a configuration is
The voltage Vb appearing on the signal line X1 is changed to the output voltage Vout / n.
(N: turns ratio of the primary winding 42 and the secondary winding 43 of the high-frequency transformer 41) and the voltage waveform of the voltage Va appearing on the signal line X3 and the current detected by the current detecting element 35 So that the current waveform of Ia is similar
In addition, conduction / non-conduction of the switch element 32 in the booster circuit 30 is controlled so that the voltage across the capacitor 34 is maintained substantially constant.

That is, the turns ratio of the primary winding 42 and the secondary winding 43 of the high-frequency transformer 41 is 1: n, and the voltage Vs generated between the secondary windings 43 of the high-frequency transformer 41 is 1
When the voltage Vs generated between the secondary windings 43 is lower than the output voltage Vout supplied to the load 3, the secondary winding becomes n times the voltage Vb generated between the secondary windings 42. 43
Current does not flow from the load 3 to the load 3. Since no current flows to the load 3 means that the input current Iin does not flow, the input current Iin does not flow when the voltage Vb is lower than the voltage Vout / n. If the period during which the input current Iin does not flow becomes longer, the harmonic components of the input current increase. For this reason, the control circuit 61 outputs the voltage V appearing on the signal line X1 via the input terminal c.
b, and in a region where the first input rectifier circuit 10 cannot maintain the voltage Vb at the voltage Vout / n or more, a pulse-like control signal is supplied to the switch element 32 through the output terminal d to switch the switch element 32. Is switched, and thereby the boosting by the boosting circuit 30 is started.

More specifically, the first input rectifier circuit 10
In a region where the voltage Vb cannot be maintained at or above the output voltage Vout / n, the RS latch circuit 74 is set when the level of the triangular wave supplied from the oscillator 73 reaches a predetermined level, and sets its output to a high level. As a result, the switch element 32 becomes conductive. After that, the RS latch circuit 74 calculates the result of the operation by the multiplier 71 and the current Ia.
Reset at a predetermined timing based on the information indicating
The output is set to low level. As a result, the switch element 32 is turned off. Here, the “predetermined timing” is an element that determines the duty of the output waveform from the output terminal d. That is, the duty of the output waveform from the output terminal d is determined by the timing at which the output of the comparator 72 becomes high after the switch element 32 is turned on. As a result of the switching by the switch element 32, the duty is the waveform of the voltage Va supplied to the input terminal a and the current I supplied to the input terminal b.
a and the capacitor 34
Is determined so that the voltage across the terminal is maintained substantially constant.

On the other hand, in a region where the voltage Vb can be maintained at the output voltage Vout / n or more by the first input rectifier circuit 10, the comparator 72 keeps its output at a high level. The reset state is maintained irrespective of the input from 73 to the set input terminal (S). Therefore, the output from the output terminal d is maintained at a low level (duty = 0), and the switch element 32 is turned off. Thereby, the boosting operation by the booster circuit 30 is stopped.

As described above, the control circuit 61 controls the switch element 32 so that the voltage Vb does not drop below the output voltage Vout / n.
When the input current Iin is equal to or higher than the output voltage Vout / n, the input current Iin flows directly into the switch circuit 40 via the first input rectifier circuit 10, and when the input voltage Vin is equal to or lower than the output voltage Vout / n. Since the output voltage Vout / n or more is maintained, the input current Iin cannot flow into the switch circuit 40 via the first input rectifier circuit 10, and the second input rectifier circuit 20 and the booster circuit 30 Through the switch circuit 40.

The control circuit 61 having such a function includes, for example, a power control IC: U manufactured by UNITRODE.
C3854B.

FIG. 3 is a block diagram showing a circuit configuration of the control circuit 62.

As shown in FIG. 3, the control circuit 62
A multiplexer 81, an A / D converter 82, an interrupt controller 83, a processor core 84,
It includes an OM 85, a timer 86, a RAM 87, and an I / O controller 88.

The multiplexer 81 receives the output current Iout supplied from the input terminal e and the output voltage Vout supplied from the input terminal f, and supplies one of them to the A / D converter 82. The A / D converter 82 converts the output current Iout or the output voltage Vout supplied via the multiplexer 81 into digital information. The interrupt controller 83 receives the zero-cross detection signal zero supplied from the input terminal g, and issues an interrupt to the processor core 84 every time this signal is activated. The processor core 84 is a control unit that controls the entire operation of the control circuit 62. The ROM 85 stores the processor core 84
Stores a program indicating a processing procedure to be performed and basic data obtained by dividing a waveform of a half cycle of a sine wave having an amplitude of 1 (half sine wave waveform) into 128 in the time axis direction.
Of the basic data, data stored at the head address is read from the processor core 84 in response to an interrupt signal issued from the interrupt controller 83. After the interrupt signal is issued from the interrupt controller 83, the timer 86 generates an interrupt signal at a period of 78 μsec (when the AC power supply 1 is a commercial power supply of 50 Hz).
Among the basic data stored in the ROM 85, the data stored at the next address is read. RAM87
Is a work area used for calculation by the processor core 84. The I / O controller 88 includes a processor
This is an interface circuit for outputting data obtained by the calculation by the core 84 from the output terminal h as a control signal cntl.

The control circuit 62 having such a configuration is
In this embodiment, the output voltage Vout is monitored,
The control signal cntl is controlled so that it has a constant voltage value.
Generate

Specifically, first, the output voltage Vout converted into digital information by the A / D converter 82 via the multiplexer 81 is converted into predetermined parameters under the control of the processor core 84. on the other hand,
As described above, every time the zero-cross detection signal zero supplied from the input terminal g is activated, the data stored in the head address among the basic data stored in the ROM 85 is read out by the processor core 84. , The processor core 84 compares the obtained parameter with a parameter indicating a reference value of the output voltage Vout. As a result of the comparison, if the obtained parameter is larger than the parameter indicating the reference value, it means that the output voltage Vout supplied between the output terminals OUT1 and OUT2 is larger than the reference value. Is reduced and output from the output terminal h via the I / O controller 88. Conversely, if the obtained parameter is smaller than the parameter indicating the reference value, it means that the output voltage Vout supplied between the output terminals OUT1 and OUT2 is smaller than the reference value. Increase the value of the I / O
The signal is output from the output terminal h via the controller 88.

Next, 78 μsec after the interrupt signal is issued from the interrupt controller 83, the timer 86
In response to this, the processor core 84 reads the data stored at the next address among the basic data stored in the ROM 85 in response to the interrupt signal. The data read in this manner is also reduced or increased based on the result of the comparison between the parameters by the processor core 84 and output from the output terminal h.

Such processing is performed successively each time an interrupt signal is generated by the timer 86. As a result, a control signal cntl having a waveform corresponding to the output voltage Vout supplied between the output terminals OUT1 and OUT2 is output from the output terminal h, and this is output to the control circuit 63 as described above.
Is supplied to the input terminal i.

As the control circuit 62 having such a function, for example, an NEC microcontroller: μP
D78324.

FIG. 4 is a block diagram showing a circuit configuration of the control circuit 63.

As shown in FIG. 4, the control circuit 63
Comparator 91, oscillator 92, RS latch circuit 9
3 is included.

The comparator 91 receives the control signal cntr1 supplied from the input terminal i from the inverting input terminal (-), and receives the information indicating the current Ic supplied from the input terminal j from the non-inverting input terminal (+). These are compared and the current Ic
Is supplied to the reset input terminal (R) of the RS latch circuit 93 in response to the information indicating the control signal exceeding the control signal cntl. The oscillator 92 is a circuit that generates a triangular wave having a predetermined frequency, for example, a frequency of 100 kHz to 200 kHz.
It is supplied to the set input terminal (S) of the S latch circuit 93. The RS latch circuit 93 changes the level of the signal output from the output terminal (Q) to low level in response to the signal supplied to the reset input terminal (R) being high level, and sets the signal to the set input terminal (S). The level of the signal output from the output terminal (Q) in response to the high level of the signal supplied to the terminal is set to the high level.

The control circuit 63 having such a configuration is
The pulse current Ic detected by the current detecting element 45 is monitored, and the switching element is switched via the pulse transformer 64 via the pulse transformer 64 so that the current waveform of the pulse current Ic matches the waveform of the control signal cntl supplied from the control circuit 62. 44 is controlled. Specifically, the drive signal of the switch element 44 output from the output terminal k becomes high level in response to the triangular wave supplied from the oscillator 92 becoming high level and the RS latch circuit 93 being set, and thereafter,
It goes low in response to the information indicating the current Ic becoming larger than the control signal cntl. This allows
The waveform of the current Ic has a peak limited by the control signal cntl.

The control circuit 63 having such a function is, for example, a power control IC: U manufactured by UNITRODE.
C3825.

Next, the operation of the power supply device according to the preferred embodiment of the present invention will be described.

FIG. 5 shows voltage waveforms and current waveforms showing the operation of the power supply device according to the preferred embodiment of the present invention.

As shown in FIG. 5, the waveform of the input voltage Vin of the AC power supply 1 is sinusoidal, and the voltage Va after full-wave rectification of the input voltage Vin by the second input rectifier circuit 20 becomes a pulsating flow. Although the voltage Vb after the input voltage Vin of the AC power supply 1 is full-wave rectified by the first input rectifier circuit 10 also tends to form a pulsating flow, as described above, the voltage Vout / n (n: high-frequency transformer 4
(1 turns ratio of the primary winding 42 and the secondary winding 43), and as a result, a waveform as shown in FIG. 5 is obtained.

More specifically, at time t0 when the input voltage Vin crosses the zero voltage, the signal line X1 is boosted by the booster circuit 30, and the voltage Vb on the signal line X1 becomes V
out / n or more, the input current Iin
Cannot flow directly into the capacitor 34, but flows into the capacitor 34 via the booster circuit 30. At this time, as described above, the control circuit 61 maintains the voltage between both ends of the capacitor 34 substantially constant, and also controls the input voltage V
The switching of the switch element 32 is controlled so that the waveform of the input current Iin and the waveform of the input current Iin are substantially similar.

This operation is performed until time t1 when the instantaneous value of the input voltage Vin becomes higher than the output voltage of the booster circuit 30. When the instantaneous value of the input voltage Vin becomes higher than the output voltage of the booster circuit 30, the control circuit 61 stops the switching of the switch element 32, as described above, so that the boosting by the booster circuit 30 is stopped. As a result, the input current Iin flows directly into the capacitor 34 without passing through the booster circuit 30. As described above, the capacitor 3
Since the capacity of 4 is small and has substantially no smoothing action,
The voltage Vb across the capacitor 34 is substantially equal to the input voltage Vin, and the voltage Vb is equal to the input voltage Vi.
It changes following the change of n.

Thereafter, when the instantaneous value of the input voltage Vin becomes lower than the output voltage of the booster circuit 30 again at time t2, the control circuit 61 restarts switching by the switch element 32 again and performs the boosting operation by the booster circuit 30. To maintain the voltage Vb at Vout / n or more. This operation is performed until time t3 when the instantaneous value of the input voltage Vin becomes higher than the output voltage of the booster circuit 30.

As described above, in the power supply according to the preferred embodiment of the present invention, the instantaneous value of the input voltage Vin is Vou.
When the voltage is higher than t / n, the boosting by the booster circuit 30 is not performed, and the input current Iin flows into the switch circuit 40 without passing through the booster circuit 30.
, The reduction in conversion efficiency due to the presence of the metal oxide is minimized. The instantaneous value of the input voltage Vin is Vout / n.
When the voltage is lower than Vout, the voltage is boosted by the booster circuit 30 and the voltage Vb is maintained at Vout / n or more, so that the input current Iin can always flow, and as a result, the input current Iin
It is possible to make the waveform of in coincide with the waveform of the input voltage Vin. Thereby, the power factor can be improved.

Since the capacitance of the capacitor 34 is small, the input current Iin follows a change in the current Ic flowing through the primary winding 42 of the high-frequency transformer 41 of the switch circuit 40. Therefore, the waveform of the input current Iin is changed to the input voltage Vi.
The current Ic flowing through the primary winding 42 of the high-frequency transformer 41 needs to be sinusoidal in order to make the same sinusoidal waveform as the waveform n and to bring the power factor close to one.

FIG. 6 is a waveform diagram showing the operation of control circuit 63.

As shown in FIG. 6, when the drive signal of the switch element 44 output from the output terminal k goes high, the switch element 44 becomes conductive and the current Ic increases, but the amount of the current Ic decreases. When the value reaches the value indicated by the control signal cntl, the output of the comparator 91 goes high, the RS latch circuit 93 is reset, and the switch element 44 is turned off. After that, the oscillator 9
The level of the triangular wave supplied from 2 becomes high level,
When the RS latch circuit 93 is set again, the switch element 44 becomes conductive, and the current Ic starts increasing again. As described above, since the frequency of the triangular wave supplied from the RS latch circuit 93 is, for example, 100 kHz to 200 kHz, the above operation is repeatedly performed at the frequency.

The peak of the current Ic corresponds to the control signal cn.
Since it is limited by trl, when the control signal cntr1 changes, the peak of the current Ic also changes accordingly. For example, as shown in FIG.
When the level of 1 becomes low (control signal cntl ′), the peak of the current Ic is also suppressed accordingly. As described above, the control signal cnt generated by the control circuit 62
rl decreases if the output voltage Vout supplied between the output terminals OUT1 and OUT2 is excessive,
If the output voltage Vout supplied between the output terminals OUT1 and OUT2 is excessively small, the current Ic increases. Therefore, the peak of the current Ic also decreases if the output voltage Vout supplied between the output terminals OUT1 and OUT2 is excessively large. , The output voltage V supplied between the output terminals OUT1 and OUT2
If out is too small, it rises. Thus, in the power supply device according to the preferred embodiment of the present invention, the output terminal OU
Output voltage Vout supplied between T1 and OUT2
Is stabilized, and the current Ic flowing through the primary winding 42 of the high-frequency transformer 41 becomes sinusoidal.

In order to make the waveform of the input current Iin closer to a sine wave, the amount of the current Ic is reduced by the capacitor 34 during the period in which the boosting circuit 30 is boosting (for example, from time t2 to time t3). During a period in which the boosting circuit 30 does not perform boosting (for example, from time t1 to time t2), the input current I
It is desirable to control the switching of the switch element 44 so that the waveform of in becomes similar to the waveform of the input voltage Vin. The reason will be described below.

FIG. 7 is a circuit diagram showing a state where the AC power supply 1 is connected to the input side of the booster circuit 30 and the load 3 is connected to the output side. FIG. 8 is a diagram showing current waveforms of the input current Iin ₃₀ and the current Icin.

As shown in FIG. 7, when the AC power supply 1 is connected to the input side of the booster circuit 30, the input voltage Vin ₃₀
Since the waveform of the input current Iin ₃₀ is a sine wave, the envelope of the current Icin flowing into the capacitor 34 when the switch element 32 is in a non-conductive state is, as shown in FIG. _The current waveform has a frequency component twice as large as ₃₀ .

Because the current Icin flowing into the capacitor 34 is

[0067]

(Equation 1) Since the waveforms of the input voltage Vin ₃₀ and the input current Iin ₃₀ are both sine waves,

[0068]

(Equation 2) Thus, the current Icin flowing into the capacitor 34 has a current waveform having a frequency component twice as high as that of the input current Iin ₃₀ .

On the other hand, in order for the voltage Vb to be constant, the current Icin flowing into the capacitor 34 and the capacitor 34
Must be equal to the current Iout flowing out of the circuit.

Therefore, in order to make the waveform of the input current Iin closer to a sine wave, the amount of the current Ic is reduced by the capacitor during the period in which the boosting circuit 30 is boosting (for example, from time t2 to time t3). In the period during which the boosting circuit 30 does not perform boosting (for example, from time t1 to time t2), the waveform of the input current Iin is similar to the waveform of the input voltage Vin. It is desirable to control the switching of the switch element 44.

In other words, the control signal cntl generated by the control circuit 62 has a current waveform having a frequency component twice as high as the input current Iin during the period in which the booster circuit 30 operates. If the waveform is similar to the waveform of the input voltage Vin during the non-period, the input current Ii
The waveform of n will be closer to a sine wave.

As described above, according to the power supply device of the present embodiment, the power factor is improved and the harmonic components contained in the input current are effectively removed while minimizing the decrease in the conversion efficiency. It is possible to provide a power supply device that can perform the operation.

According to the power supply device of this embodiment, a power factor of 0.99 and a harmonic current distortion factor (THD) of the input current Iin of 5.85% can be obtained.
The standard value of 61000-3-2 classA could be satisfied.

The present invention is not limited to the above embodiments, and various changes can be made within the scope of the invention described in the claims, and they are also included in the scope of the present invention. It goes without saying that it is a thing.

For example, in the above embodiment, the control unit 60 is constituted by three control circuits consisting of the control circuits 61 to 63, but the control unit 60 is provided by only one control circuit having all the functions of these three control circuits. May be configured.

In the above embodiment, the control circuit 62 compares the parameter generated based on the output voltage Vout with the parameter indicating the reference value of the output voltage Vout, and stores the parameter in the ROM 85 based on the comparison. The control signal cntrl is generated by decreasing or increasing the value of the basic data, thereby stabilizing the output voltage Vout. However, the present invention is not limited to this, and stabilization of the output current Iout, Output power (Vout × Io
ut) may be configured to be stabilized. To stabilize the output current Iout, a parameter generated based on the output current Iout is compared with a parameter indicating a reference value of the output current Iout, and based on the comparison,
The control signal cntl may be generated by decreasing or increasing the value of the basic data stored in the output data 85, and when stabilizing the output power (Vout × Iout), the output signal Iout and the output voltage Vout may be adjusted. The parameter generated based on the output power is compared with a parameter indicating a reference value of the output power Vout × Iout.
The control signal cntl may be generated by decreasing or increasing the value of the basic data stored in 5.

Further, in the above embodiment, the control circuit 62 compares a parameter generated based on the output voltage Vout with a parameter indicating a reference value of the output voltage Vout, and based on the comparison, the parameter stored in the ROM 85 is stored. The control signal cntrl is generated by decreasing or increasing the value of the basic data, thereby matching the waveform of the input current Iin with the waveform of the input voltage Vin, and removing a harmonic component included in the input current. However, in the period t2 to t3 during which the boosting circuit 30 boosts the basic data stored in the ROM 85, the current amount of the current Ic matches the current amount flowing into the capacitor 34, and the boosting circuit 3
In a period from t1 to t2 in which the boosting by 0 is not performed, a harmonic component such that the waveform of the input current Iin and the waveform of the input voltage Vin match is included, whereby the harmonic component included in the input current is more effective. You may be comprised so that it may be removed.

In the present invention, the means does not necessarily mean physical means, but also includes a case where the function of each means is realized by software. Further, the function of one unit may be realized by two or more physical units, or the function of two or more units may be realized by one physical unit.

[0079]

As described above, according to the present invention,
The power factor is improved while minimizing the decrease in conversion efficiency,
A power supply device in which harmonic components included in an input current are effectively removed can be provided.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a power supply device according to a preferred embodiment of the present invention.

FIG. 2 is a block diagram illustrating a circuit configuration of a control circuit 61;

FIG. 3 is a block diagram illustrating a circuit configuration of a control circuit 62;

FIG. 4 is a block diagram illustrating a circuit configuration of a control circuit 63;

FIG. 5 is a voltage waveform and a current waveform showing an operation of the power supply device according to the preferred embodiment of the present invention.

FIG. 6 is a waveform chart showing an operation of the control circuit 63;

FIG. 7 is a circuit diagram showing a state in which the AC power supply 1 is connected to the input side of the booster circuit 30 and the load 3 is connected to the output side.

FIG. 8 shows an input current Iin ₃₀ and a current Icin;
FIG. 4 is a diagram showing a current waveform of FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 AC power supply 2 Input filter 3 Load 10 First input rectifier circuit 11 to 14 Diode 20 Second input rectifier circuit 21, 22 Diode 30 Boost circuit 31 Inductor 32 Switch element 33 Diode 34 Capacitor 35 Current detection element 40 Switch circuit 41 High frequency transformer 42 Primary winding 43 Secondary winding 44 Switch element 45 Current detection element 50 Output rectification circuit 51, 52 Diode 53 Inductor 54 Capacitor 55 Current detection element 60 Control unit 61-63 Control circuit 64 Pulse transformer 65 Zero cross detection circuit 71 Multiplier 72 Comparator 73 Oscillator 74 RS Latch Circuit 81 Multiplexer 82 A / D Converter 83 Interrupt Controller 84 Processor Core 85 ROM 86 Timer 87 RAM 88 I / O Controller 91 Comparator 92 Oscillator 93 RS latch circuit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Wataru Nakabori 1-13-1 Nihombashi, Chuo-ku, Tokyo TDC Corporation F-term (reference) 5H006 AA02 CA02 CB01 CB08 CB09 CC04 CC08 DB07 DC02 DC05 5H730 AA18 AS01 BB14 BB23 BB57 CC04 CC07 DD04 EE02 EE08 EE10 EE59 FD01 FD31 FD41 FF02 FG05

Claims (9)

[Claims] 1. A first input rectifier for rectifying an input voltage supplied from an AC power supply, a transformer receiving an output from the first input rectifier on a primary winding, and a secondary winding of the transformer. An output rectifier circuit for smoothing an output from a line, and in response to an instantaneous value of the input voltage supplied from the AC power supply becoming equal to or less than a predetermined voltage, changing a voltage of the primary winding of the transformer. A power supply device comprising: a step-up means for stepping up a voltage. 2. The transformer according to claim 1, wherein a turn ratio of the primary winding to the secondary winding is 1: n, and the predetermined voltage is obtained by dividing an output voltage output from the output rectifier circuit by n. The power supply device according to claim 1, wherein the power supply device is defined by the applied voltage. 3. The boosting means boosts an output from the second input rectifying means, which rectifies the input voltage, and supplies the boosted output to the primary winding of the transformer. The power supply device according to claim 1, further comprising a booster circuit. 4. The power supply device according to claim 1, further comprising switch means for setting a voltage waveform of said primary winding of said transformer to a pulse waveform. 5. A sine wave generating means for generating a control signal having a sine wave waveform synchronized with a phase of the AC power supply based on at least one of an output voltage and an output current output from the output rectifier circuit, Current detection means for detecting a current flowing through the primary winding of the transformer, and a current waveform of the current detected by the current detection means coincides with a waveform of the control signal generated by the sine wave generation means. The power supply device according to claim 4, further comprising control means for controlling switching of the switch means. 6. The power supply device according to claim 5, wherein a harmonic component is included in a sine wave waveform of the control signal generated by the sine wave generation unit. 7. The sine wave generator decreases an amplitude of the control signal in response to at least one of an output voltage, an output current, and an output power output from the output rectifier circuit being larger than a desired value. 7. The power supply according to claim 5, wherein the amplitude of the control signal is increased in response to being smaller than a desired value. 8. The control means includes comparison means for comparing the current detected by the current detection means with the control signal supplied from the sine wave generation means, and at least a result of the comparison by the comparison means. The power supply device according to any one of claims 5 to 7, wherein switching of the switch means is controlled in response to the control signal. 9. The control means keeps at least one of an output voltage, an output current and an output power output from the output rectifier circuit substantially constant, and a waveform of an input current supplied from the AC power supply. The power supply device according to any one of claims 5 to 8, wherein the power supply device has a sinusoidal shape.