JP2000166239A - Variable voltage converter and air conditioner using the converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the power consumption of a variable voltage converter by mounting the resistor for detecting current of the variable voltage converter at a position through which current flows intermittently, and providing a digital current detecting part for detecting the current. SOLUTION: The resistor 28 for detecting current of a variable voltage converter 27 is mounted on the downstream side of a switching element 9 through which current flows intermittently, and the current indicated by an arrow 16 of the current flowing through a reactor 8 is supplied to the resistor 28 for detecting current through the switching element 9. The current flowing through the resistor 28 for detecting current is detected by the reference waveform outputting part 32 of a digital current detecting part 29 according to the timing of an outputted signal. As a result, prescribed voltage can be obtained at a position across a smoothing capacitor 11. The current will not flow all the time, thus it is possible to suppress the electric power consumption of the variable voltage converter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to current detection for detecting a current value necessary for controlling a variable voltage converter.

[0002]

2. Description of the Related Art A conventional variable voltage converter will be described with reference to FIG. 8, and an air conditioner as an example of equipment using the variable voltage converter will be described with reference to FIG.

In FIG. 9, 1 is a commercial power supply, 2 is a rectifier circuit (diode bridge), 3 is a variable voltage converter, 4 is an inverter, 5 is a motor (compressor), and 6 is a control unit.

A commercial power supply 1 rectifies an input AC voltage by a rectifier circuit 2, converts the AC voltage into a predetermined DC voltage by a variable voltage converter 3, and then applies the DC voltage to an inverter 4. The DC voltage applied to the inverter 4 is a pseudo AC voltage that rotates the motor 5 at a predetermined frequency because the inverter 4 performs a switching operation according to the control signal output from the INV control unit 7.

The operation of the variable voltage converter 3 will be described in detail with reference to FIG. In FIG. 8, 8 is a reactor, 9
Is a switching element, 10 is a rectifying element (flywheel diode), 11 is a smoothing capacitor, 12 is a current detecting resistor, 13 is an analog current detecting unit, 14 is a first power line, and 15 is a second power line.

At the time of boosting the output voltage higher than the input voltage, the current rectified by the rectifier circuit 2 flows through the reactor 8 provided on the first power line. Then, when the switching element 9 is on, a current flows in the direction of arrow 16,
Energy is stored in the reactor 8. Next, when the switching element 9 is turned off, the energy stored in the reactor 8 flows in the direction of the arrow 17 as a current.

[0007] This current is stored as charge in the smoothing capacitor 11 and is boosted to a predetermined DC voltage.

The currents divided by the arrows 16 and 17 flow through devices such as the inverter 4 and the motor 5,
It merges again and flows through the current detection resistor 12 provided on the second power line 15 (arrow 18). At this time, the voltage at both ends of the current detection resistor 12 is detected by the analog current detection unit 13 and the value of the flowing current is converted into a voltage and calculated.

[0009] As shown in FIG. 9, the switching element 9 is turned on and off based on the current value calculated by the analog current detection unit 13 and the voltage value detected by the voltage detection unit 19.
The control signal to be operated is calculated by the CONV control unit 20 and the switching element 9 is driven to obtain a predetermined voltage.

These operations will be described in detail with reference to FIG. The timing chart shown in FIG. 10 includes, in order from the top, a current (a) flowing through the reactor 8, a current (b) indicated by an arrow 17, a current (c) indicated by an arrow 16, and the comparison unit 2
5 shows the comparison content (d) and the output signal (e) of the CONV drive unit 26.

The current (a) flowing through the reactor 8 is indicated by an arrow 1
The current is divided into a current (b) indicated by 7 and a current (c) indicated by an arrow 18. These currents again flow as indicated by an arrow 18 on the power line 15 and are detected by the analog current detection unit 13 as the same waveform as in FIG.

The calculated value 22 calculated by the current / voltage calculator 21 based on the result detected by the analog current detector 13 and the result detected by the voltage detector 19, and output from the reference waveform output unit 23 The comparison with the reference waveform 24 is performed by the comparison unit 25. The content of this comparison is (d). The drive signal of the switching element 9 obtained from the comparison result is output as the output signal (e) of the CONV drive unit 26.

[0013]

However, the above-mentioned conventional configuration has a problem that the current always flows through the current detecting resistor 12, so that power is always consumed and the efficiency of the variable voltage converter 3 is reduced. Was.

In particular, when the variable voltage converter 3 is used in an air conditioner, there is a problem that the COP (coefficient of performance) of the air conditioner is lowered. In an air conditioner in which intense competition for energy saving has been developed, reduction of power consumption of equipment has been a major issue.

The present invention has been made to solve such a conventional problem, and has as its object to reduce the power consumption of a variable voltage converter.

Further, by using this variable voltage converter in an air conditioner, an air conditioner with low power consumption is provided.

[0017]

According to the present invention, a current detecting resistor of a variable voltage converter is provided at a position where current flows intermittently. In addition, a digital current detection unit for detecting this current at regular intervals is provided.

With the above configuration, a predetermined voltage can be obtained while reducing power consumption.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to solve the above-mentioned problems, the present invention is to provide a current detecting resistor in series with a switching element provided between first and second power lines.

Further, according to the present invention, a current detecting resistor for detecting a current flowing through the rectifying element is provided between a connection point between the switching element and the second power line and a connection point between the smoothing capacitor and the second power line. It is.

Further, according to the present invention, there is provided a digital current detecting section for detecting a voltage between both ends of the current detecting resistor.

In the digital current detecting section, the timing for detecting the voltage between both ends of the current detecting resistor is set at a constant interval.

Further, the present invention uses the above-structured variable voltage converter as a converter for converting AC to DC in an air conditioner.

By providing the current detecting resistor intermittently at the position where the current flows, it is possible to detect the current flowing through the variable voltage converter while suppressing power consumption.

In addition, since the digital current detector detects a value obtained by converting the current flowing through the variable voltage converter into the voltage at regular intervals, a predetermined voltage can be obtained without constantly detecting the current.

Further, since the above-described variable voltage converter is used, the power consumption of the air conditioner can be reduced.

[0027]

Embodiments of the present invention will be described below with reference to the drawings.

The components having the same functions as those of the prior art are denoted by the same reference numerals, and description thereof is omitted.

(Embodiment 1) In FIGS. 1 and 2, 27 is a variable voltage converter, 28 is a current detecting resistor, 29 is a digital current detecting unit, 30 is a CONV control unit, and 31 is a current
A voltage calculation unit, 32 is a reference waveform output unit, and 34 is an on-state of the switching element 9 based on the result of the current / voltage calculation unit 31.
An operation unit for calculating the timing of turning off the control unit 35 is a CONV drive unit for outputting a signal for driving the switching element 9.

As shown in the figure, the current detecting resistor 28 is provided downstream of the switching element 9 through which a current flows intermittently.

In the above configuration, at the time of non-step-up, the switching element 9 remains open, so that the current 16 does not flow through the current detecting resistor 28 and no power loss occurs.

Next, the operation at the time of boosting will be described in detail with reference to FIG. The timing chart shown in FIG. 3 shows, in order from the top, a current (a) flowing through the reactor 8, a current (b) indicated by an arrow 17, a current (c) indicated by an arrow 16, and an output signal (d) of the CONV driver 35. , The output signal (e) of the reference waveform output unit 32.

The current (a) flowing through the reactor 8 is indicated by an arrow 1
The current is divided into a current (b) indicated by 7 and a current (c) indicated by an arrow 16. Among these currents, the current (c) indicated by arrow 16 is
The current flows through the switching element 9 to the current detection resistor 28. The digital current detector 29 detects the current detection resistor 2 at timing 33 in accordance with the signal output from the reference waveform output unit 32.
8 is detected.

The current value obtained at this time and the voltage detection unit 36
The switching element 9 is turned on-o based on the voltage value detected by
The timing of ff is calculated by the calculation unit 34, and an output signal (d) for driving the switching element 9 is output from the CONV drive unit 35 based on the calculation result.

As a result, a predetermined voltage can be obtained at both ends of the smoothing capacitor 11. That is, by detecting the intermittently flowing current (arrow 16) and controlling the switching element 9, it is possible to obtain a predetermined voltage while suppressing the power consumption of the variable voltage converter 27.

FIG. 5 shows another embodiment. Even if the current detection resistor 28 is provided between the first power line 14 and the switching element 9, the same effect as described above can be expected.

(Embodiment 2) FIG.
Current detecting resistor 2 for detecting a current 17 flowing through the rectifying element 10 between a connection point between the second power line 15 and the connection point between the smoothing capacitor 11 and the second power line 15.
8 is another embodiment in which 8 is provided.

In this embodiment, the variable voltage converter 42 is controlled by detecting the current indicated by the arrow 17.

According to this configuration, in addition to the effect of the first embodiment, when the smoothing capacitor 11 is short-circuited, the value of the current flowing through the current detecting resistor 28 increases, so that the short-circuit can be detected.

(Embodiment 3) FIG. 6 shows another embodiment in which an overcurrent detection section 37 and a protection section 38 are provided.

For example, the overcurrent detecting section 37 is constituted by a comparator or the like, and if the reference voltage is exceeded, it is determined that an overcurrent has occurred. At this time, by activating the protection unit 38 such as a relay, damage to the device can be prevented.

(Embodiment 4) FIG. 7 shows an embodiment in which the present invention is applied to another variable voltage converter.

This circuit comprises a second switching element 40
And a step-up / step-down converter 39 that performs a step-down operation by the second rectifying element 41 and the reactor 8.

As shown in this circuit, if the current detecting resistor 28 is provided at a position where a current flows intermittently, the same effect of obtaining a predetermined voltage while suppressing power consumption can be obtained in other types of converters. Obtainable.

Further, even if a variable voltage converter having any of the above-mentioned configurations is used as the variable voltage converter 27 of the air conditioner shown in FIG. 2, the power consumption of the converter can be reduced, thereby improving the COP as the air conditioner. be able to.

[0046]

As is clear from the above embodiment, according to the first aspect of the present invention, the current detecting resistor is provided in series with the switching element provided between the first and second power lines. Since no current always flows, power consumption of the variable voltage converter can be suppressed.

According to the second aspect of the present invention, a current detecting device for detecting a current flowing through the rectifying element between a connection point between the switching element and the second power line and a connection point between the smoothing capacitor and the second power line. Since the resistor is provided, a short circuit of the smoothing capacitor can be detected in addition to the first aspect of the present invention.

According to the third and fourth aspects of the present invention, the digital current detecting section for detecting the voltage between both ends of the current detecting resistor is provided, and the timing for detecting the voltage between both ends is set to a constant interval. Thus, the current necessary for controlling the variable voltage converter can be detected without constantly detecting the current, so that a predetermined voltage can be obtained while suppressing the power consumption of the variable current converter.

According to the fifth aspect of the present invention, the variable voltage converter according to any one of the first to fourth aspects is used as a converter for converting AC to DC in the air conditioner. , Power consumption of the air conditioner can be reduced. Therefore, the COP of the air conditioner is improved.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram of a variable voltage converter showing one embodiment of the present invention.

FIG. 2 is a block diagram of the air conditioner using FIG. 1;

FIG. 3 is a timing chart of a current and an output signal showing one embodiment of the present invention.

FIG. 4 is an electric circuit diagram of a variable voltage converter showing another embodiment.

FIG. 5 is an electric circuit diagram of a variable voltage converter showing another embodiment.

FIG. 6 is an electric circuit diagram of a variable voltage converter showing another embodiment.

FIG. 7 is an electric circuit diagram of a variable voltage converter showing another embodiment.

FIG. 8 is an electric circuit diagram of a conventional variable voltage converter.

9 is a block diagram of the air conditioner using FIG.

FIG. 10 is a timing chart of a conventional current and output signal.

[Explanation of symbols]

 Reference Signs List 8 reactor 9 switching element 10 rectifying element 11 smoothing capacitor 14 first power line 15 second power line 28 current detection resistor 29 digital current detection unit

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Okui 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. F-term (reference) 5H006 AA00 BB05 CA01 CB01 CB03 CC02 DA02 DA04 DB01 DC02 DC05 FA02

Claims (5)

[Claims] 1. A first and a second power line through which a main current flows, a reactor through which a half-wave or full-wave rectified current flows through the first power line, and a rectifying element for preventing backflow downstream of the reactor. A switching element having one end connected to the upstream side of the rectifying element and the other end connected to the second power line to adjust the flow rate of a current flowing in the reactor by performing on-off, and A smoothing capacitor connected in parallel to the first and second power lines on the downstream side of the element and for smoothing a voltage between the first and second power lines; A variable voltage converter comprising a current detecting resistor for detecting a flowing current. 2. A first and a second power line through which a main current flows, a reactor through which a half-wave or full-wave rectified current flows through the first power line, and a rectifying element for preventing a backflow downstream of the reactor. A switching element having one end connected to the upstream side of the rectifying element and the other end connected to the second power line to adjust the flow rate of a current flowing in the reactor by performing on-off, and A smoothing capacitor connected in parallel to the first and second power lines on the downstream side of the element to smooth a voltage between the first and second power lines; A variable current detecting resistor for detecting a current flowing through the rectifying element between a connection point and a connection point between the smoothing capacitor and the second power line. Pressure converter. 3. A digital current detector for detecting a voltage between both ends of a current detection resistor.
Or the variable voltage converter according to 2. 4. The variable voltage converter according to claim 3, further comprising a digital current detection unit that sets a timing of detecting a voltage between both ends of the current detection resistor at a predetermined interval. 5. A rectifier circuit for half-wave or full-wave rectification of AC input from a commercial power supply, a variable voltage converter for converting DC to AC, and a pseudo-AC for driving a motor built in the compressor. An air conditioner comprising an inverter for converting the voltage into a variable voltage, and using the variable voltage converter according to any one of claims 1 to 4 as the variable voltage converter.