JPH0634577B2 - Power supply - Google Patents

Description

TECHNICAL FIELD The present invention relates to a power supply device including an inverter for frequency conversion or electrical insulation.

[Prior Art] A DC power supply for an inverter is generally composed of a rectifier circuit. When this rectifier circuit is connected to a commercial AC power supply, the input voltage is a sine wave, but the input current is not necessarily a sine wave and the power factor is not 1.

In order to approximate the input current waveform of the rectifier circuit to a sine wave and bring the power factor close to 1, connect a reactor to the input or output power supply line of the rectifier circuit, and short the power supply line with a switch at a stage subsequent to this reactor. Controlling the input current waveform by, for example, the Institute of Electrical Engineers of Japan, B, Vol. 105, No. 2
It is known for "Improving the input current waveform of a single-phase rectifier circuit" by Isao Takahashi et al.

[Problems to be Solved by the Invention] However, in the conventional current waveform improving method, the power supply device inevitably has a high cost because the short-circuit switch has to be independently provided and controlled.

Therefore, an object of the present invention is to easily improve the input current waveform of a power supply device including an inverter.

[Means for Solving the Problems] The present invention for achieving the above object includes an AC power supply terminal,
A rectifier circuit connected to the AC power supply terminal, a plurality of switches for exchanging DC into AC, and an inverter connected to the rectifier circuit, between the AC power supply terminal and the rectifier circuit, or A reactor connected in series to a power supply line between the rectifier circuit and the inverter, and between the pair of DC input lines of the inverter so that the current flowing through the AC power supply terminal approximates a sine wave. The present invention relates to a power supply device including a circuit for intermittently short-circuiting with a switch and controlling a switch of the inverter so that an AC output voltage is obtained from the inverter.

[Operation] In the above invention, when the input line is short-circuited by the switch of the inverter, the output voltage cannot be obtained from the inverter, but the voltage is applied to the reactor and the energy is accumulated in the reactor. When the inverter switch is controlled so that the inverter switch short circuit is removed and the inverter load is supplied with voltage, normal inverter operation is achieved. By controlling the time width during which the input power supply lines are short-circuited by the switch of the inverter, it is possible to control the amplitude of the AC input current, that is, the waveform.

[Embodiment] Next, a power supply device according to an embodiment of the present invention will be described with reference to FIGS. 1 to 4. Commercial AC power supply terminal 1 in FIG.
A harmonic component removing filter circuit 5 including a reactor 3 and a capacitor 4 is connected to 2. The reactor 7 connected to the output line 6 of the filter circuit 5 is used for current control. A pair of AC input terminals of the rectifier circuit 12 composed of four diodes 8, 9, 10, 11 connected in a bridge are connected to power supply terminals 1 and 2 via a current control reactor 7 and a filter circuit 5. Rectifier circuit 1
A pair of DC lines 13 connected to the DC output terminals of 2;
Between 14 are the first, second, third and fourth switches Q.
Inverter 1 with bridge connection of 1, Q2, Q3, Q4
5 is connected. Switches Q1, Q2, Q3, Q
4 is composed of a FET, and a diode D1,
D2, D3 and D4 are connected. Although not shown, a parallel circuit of a varistor and a capacitor is connected between the pair of DC lines 13 and 14 via a diode in order to absorb a feedback current. The inverter 15 includes an output transformer 16, and one of the transformers 16
One end of the next winding wire 17 has first and second switches Q1, Q
2 and the other end is a third and a fourth switch Q.
It is connected between 3 and Q4. An output rectifying circuit 23 including diodes 19, 20, 21, 22 is connected to the secondary winding 18. A smoothing capacitor 24 is connected between the pair of output lines of the output rectifying circuit 23. A load circuit such as an inverter is connected between the DC output terminals 25 and 26.

First to fourth switches Q1 to Q in the inverter 15
4 is driven by an inverter and is short-circuit controlled.
Short circuit control is performed by the first switch Q1 and the second switch Q2.
Turning on and at the same time, and the third switch Q
This is done by turning on the third and fourth switches Q4 at the same time.

In order to perform both the inverter control of the inverter 15 and the short-circuit control, the current detector 27 for detecting the current i2 on the output side of the capacitor 6 has a filter circuit 5 and a rectifier circuit 1.
It is provided between the two. An input voltage detection circuit 28 is connected to the commercial AC power supply terminals 1 and 2 in order to obtain a reference sine wave for comparison with the detected current i2. In order to detect the DC output voltage corresponding to the output voltage of the inverter 15, the output voltage detection circuit 3 is connected to the DC output terminals 25 and 26.
1 is connected.

The current detector 27 is connected to one input terminal (inverting input terminal) of the first error amplifier 35 via the absolute value circuit 34. The output line of the input voltage detection circuit 28 is connected to the other input terminal (non-inverting input terminal) of the first error amplifier 35 via an absolute value circuit 36 and a coefficient circuit, that is, a multiplication circuit 37. The first error amplifier 35 generates an output corresponding to the difference between the current i2 including the ripple component and the sine wave voltage.

In order to control the inverter 15 so as to keep the output voltage constant, the output line of the output voltage detection circuit 31 is connected to one input terminal (inverting input) of the second error amplifier 38, and the other of the error amplifier 38 is connected. Input terminal (reverse input)
A reference voltage source 39 is connected to. The second error amplifier 38 generates an output voltage corresponding to the difference between the detected voltage and the reference voltage and sends it to the multiplier 37. The multiplier 37 multiplies a value obtained by multiplying the amplitude of the reference sine wave waveform given from the absolute value circuit 36 by the output of the second error amplitude unit 38, and outputs the value of the first error amplitude unit 35.
Input to the non-inverting input terminal of.

One input terminal (inverting input) of the voltage comparator 40 is connected to the output terminal of the first error amplifier 35 via the low pass filter 43, and the other input terminal (non-inverting input) is connected to the sawtooth wave generation circuit 41. Has been done. The comparator 40 outputs the comparison output of both inputs in a binary format.

The switch control signal forming circuit 42 connected to the output terminal of the comparator 40 switches the switch Q based on the output of the comparator 40.
1 to Q4 control signals are formed. Although not shown, the output line of the control signal forming circuit 42 is connected to the control terminals (gates) of the switches Q1 to Q4.

(Operation) Next, the operation of the circuit shown in FIG. 1 will be described with reference to FIGS. The frequency of the sawtooth wave generated by the sawtooth wave generation circuit 41 for frequency conversion by the inverter 15 is set sufficiently higher than the frequency of the alternating current supplied from the alternating-current power supply terminals 1 and 2. Therefore, the current i2 in FIG. 1 has a waveform including ripples of high frequency as shown in FIG. 4 corresponding to ON / OFF control of the switches Q1 to Q4 of the inverter 15. However, the filter circuit 5
, The harmonic component is removed, and the input current i1 becomes an approximate sine wave as shown in FIG.

When the circuit of FIG. 1 is operated, the sawtooth wave generation circuit 41 causes the sawtooth wave A2 shown in FIG.
The control signal of the first switch Q1 shown in FIG. 2B and the control signal of the third switch Q3 shown in FIG. 2C are fixedly generated in synchronization with each other. In a typical inverter,
A phase inversion signal of the control signal of the first switch Q1 shown in FIG. 2B is applied to the second switch Q2, and a fourth switch Q4 is provided with a third switch Q3 of the third switch Q3 shown in FIG. 2C. A phase inversion signal of the control signal is added, but in the inverter 15 according to the present invention, as shown in FIGS. 2D and 2E, a phase difference larger than 180 degrees is generated with respect to the first and third switches Q1 and Q3. A control signal having a second and a fourth switch Q
2, add to Q4.

The control signals of FIGS. 2D and 2E are the same as those of the first error amplifier 3
5 and the comparator 40. Error amplifier 3
The current detection signal F1 including the ripple shown in FIG. 2 (F) is input to one input terminal of the multiplier 5, and the multiplier 3 is input to the other input terminal.
When the reference sine wave F2 shown in FIG. 2 (F) is input from 7 to the output stage of the low pass filter 43 connected to the output terminal of the error amplifier 35, a signal including the information of the input current i2 and the information of the output voltage. A1 is obtained. As shown in FIG. 2 (A), when the signal A1 and the sawtooth wave A2 of FIG. 2 (A) obtained from the sawtooth wave generation circuit 41 are compared by the comparator 40, the sawtooth wave A2 crosses the signal A1. The output of the comparator 40 changes every time. That is, the output of the comparator 40 becomes high level during the period of t1 to t2, t3 to t4, etc. when the sawtooth wave A2 is higher than the signal A1. The control signal forming circuit 42, based on the output of the comparator 40, is shown in FIG.
The control signals for the second and fourth switches Q2 and Q4 shown in (E) are formed. That is, in response to the output of the comparator 40 being inverted at t1, the control signal of the second switch Q2 is returned to the low level, and conversely, the control signal of the fourth switch Q4 is inverted to the high level. When the output of the comparator 40 changes to the high level again at time t3, the control signal of the second switch Q2 is changed to the high level and the control signal of the fourth switch Q4 is changed to the low level. Sawtooth wave A2 is signal A1
Across the level of t2, t from higher to lower
Time points such as 4 are independent of the control signals of the second and fourth switches Q2, Q4. Therefore, the control signals of the second and fourth switches Q2 and Q4 in FIGS.
It is formed by flip-flops triggered at t3 and t5.

During the periods of t0 to t1 and t4 to t5, the first and second switches Q1 and Q2 are both turned on, so that the DC lines 13 and 14 are short-circuited by the switch Q1Q2. As a result, the current i2 flowing through the reactor increases as indicated by t1 to t2 in FIG. In the period from t1 to t2, the second switch Q2 is turned off, so that the short circuit is released and the first switch Q1 and the output transformer 16
Since the circuit composed of the secondary winding 17 and the fourth transistor Q4 is formed, the current i2 decreases. At this time,
The sum of the AC power supply voltage and the voltage of the reactor 7 is the rectifier circuit 1
Enter 2.

At t2 to t3, the third switch Q3 and the fourth switch Q4
When and are simultaneously turned on, a short circuit is formed again, and the current i2 increases again. However, when the fourth switch Q4 is turned off at t3, a circuit including the third switch Q3, the primary winding 17 and the second switch Q2 is formed, and the current i2 decreases again. The AC power supply voltage changes with a sine wave, and since this is given to the error amplifier 35 as a reference, the current i2 also changes along the sine wave voltage. The inverter 15 does not generate an output voltage t0 to t1, t2
Up to t3, t4 to t5, etc., the switch Q1
Since a short circuit is formed at ~ Q4, the reactor 7
An electric current flows through it. Therefore, the waveform of the input current i2 can be approximated to a sine wave.

When the detection value of the DC output voltage detection circuit 31 changes, the second
The output level of the error amplifier 38 changes, the output level of the multiplier 37, that is, the amplification of the reference sine wave changes, the output level of the first error amplifier 35 changes, and the short circuit time width α, that is, the output voltage of the inverter. The width changes and the voltage is adjusted.

[Modification] The present invention is not limited to the above-described embodiments, and the following modifications are possible, for example.

(1) As shown in FIG. 1, the reactor 7 may be moved to the output side of the rectifier circuit 12.

(2) As shown in FIG. 6, it is also applicable to a case where a pair of switches Q1 and Q2 are connected to both ends of the primary winding 17 of the transformer 16 and the rectifier circuit 12 is connected to the center tap.

[Advantages of the Invention] According to the present invention, both the improvement of the waveform of the input current of the rectifier circuit as the DC power source of the inverter and the control of the inverter can be achieved with a simple circuit configuration.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a power supply device according to an embodiment of the present invention, FIG. 2 is a waveform diagram showing the voltage of each part of FIG. 1, FIG. 3 is a waveform diagram of the input current of FIG. FIG. 5 is a waveform diagram showing a current at a stage subsequent to the filter circuit of FIG. 1, FIG. 5 is a circuit diagram showing a part of a power supply device of a modification, and FIG. 6 is a part of a power supply device of another modification. It is a circuit diagram shown. 1, 2 ... Power supply terminal, 7 ... Reactor, 12 ... Rectifier circuit, 13, 14 ... DC line, Q1-Q4 ... Switch, 15 ... Inverter.

Claims (1)

[Claims] 1. An AC power supply terminal, a rectifier circuit connected to the AC power supply terminal, an inverter including a plurality of switches for exchanging DC to AC, and an AC power supply connected to the rectifier circuit. A reactor connected in series to a power supply line between a terminal and the rectifier circuit or between the rectifier circuit and the inverter, and a current of the inverter that approximates a sine wave to the current flowing through the AC power supply terminal. A power supply device comprising: a circuit for intermittently short-circuiting a pair of DC input lines by a switch of the inverter and controlling a switch of the inverter so that an AC output voltage is obtained from the inverter.