JPS62114472A - Control circuit for power unit - Google Patents

Abstract

PURPOSE:To reduce the ripples of DC voltage and currents by correcting the reference voltage value of the voltage control of an AC-DC conversion section so that the PWM pulse width of an AC output by DC-DC conversion is equalized to pulse width being set. CONSTITUTION:With a power unit containing AC-DC-AC conversion, a three- phase AC power supply 1 is rectified by a rectifier 2, desired DC voltage V is obtained by a chopper circuit consisting of a transistor (hereinafter called Tr) 4, etc., the DC voltage is changed into a square-wave AC output by a single- phase inverter circuit composed of a Tr 8, and load 13 is supplied with DC currents I through a rectifier 10 and a smoothing circuit 11. PWM pulse width is detected from an output from a PWM control circuit 22 at that time, and voltage correction circuits 31-44 correcting the reference voltage VREF of voltage control are added in response to the pulse width. Accordingly, a voltage set value VSET is corrected and transmitted over a voltage control circuit 23, and the waveform of AC output voltage approaches to a duty ratio 1 and the ripple of DC output currents I is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a control circuit for a power supply device that improves the output waveform of the power supply device including AC-DC-AC conversion.

[Technical background of the invention and its problems]

An example of a power supply device including AC-DC-AC conversion is shown in FIG.

In FIG. 5, a commercial three-phase AC power supply 1 is rectified by a rectifier 2, and further a timipper circuit comprising a transistor 4, a diode 5, a reactor 6, and a capacitor 7 outputs a required DC voltage V.

The DC voltage V is determined by using the voltage reference VILHF set by the voltage setting device 45 as a feedback signal V of the DC voltage V.
By comparing it with FB and amplifying the deviation in the voltage control circuit 23, and further controlling the base of the transistor 4 via the base drive circuit 27, it is controlled to be equal to the voltage reference VREF.

The output voltage V of the above chigoppa is transistor 80°8V,
It is input to a single-phase inverter circuit consisting of 8X and 8Y, and its square wave AC output supplies DC current I to a load 13 via a rectifier 10 and a smoothing circuit 11.

The direct current I is detected by the current feedback signal IFBK via the current detector 12, and the current reference signal 111[
! F, and the deviation is determined by the current control circuit 21, PWM
Control circuit 22 and base drive circuit 24a.

24b through the transistor 8U, 8V, 8X, 8
Y is driven, thereby performing PWM control on the single-phase inverter, and the output current is controlled to the current reference IReF.

In this case, the DC output voltage V and the output current are controlled independently, so when the current is controlled to a smaller value than the ffi pressure V, the pulse width of the AC output of the single-phase inverter is This causes a problem in that the ripple of the DC output current becomes large.

[Purpose of the invention]

The present invention automatically corrects the voltage reference signal for DC voltage control so that the pulse width of the PWM-controlled AC output is appropriate, and thereby changes the waveform of the AC output voltage to a duty ratio of 1.
The object of the present invention is to provide a control circuit for a power supply device that reduces ripples in DC output.

[Summary of the Invention] The present invention provides control of a power supply device having an AC-DC converter unit that obtains a voltage-controlled DC output from an AC power source, and a DC-AC converter unit that obtains a pulse-width-controlled AC output from the DC output. The circuit includes a pulse width comparison calculation circuit that compares the pulse width of the AC output with a reference pulse width to calculate a pulse width deviation signal including polarity, and a pulse width comparison calculation circuit that calculates a pulse width deviation signal including polarity; It is equipped with a voltage correction circuit that corrects the voltage reference for control, thereby making it possible to control the pulse width of the AC output to a desired duty ratio, and further reducing ripples in the voltage or current of the DC output obtained by rectifying the pulse width. It is designed to reduce the

[Embodiments of the invention]

An embodiment of the present invention is shown in FIG.

FIG. 1 shows a voltage correction system in which the PWM pulse width is detected from the base drive signals noUY and BDVX output from the PWM control circuit 22, and the voltage reference VRIIF for voltage control is corrected accordingly. A circuit is added, and the rest is the same as the conventional one shown in FIG.

The operation shown in FIG. 1 will be explained below with reference to the time chart shown in FIG.

That is, the base drive signals BD, J, and B
Dvx is synchronized pulse signal BD via OR gate 31.
D flip-flops 35a and 35b forming the exclusive OR gate 34 and the falling order determining circuit 36
and is input to the single shot circuit 32.

The single shot circuit 32 synchronizes with the above signal [10 and generates a set pulse width signal P'1sET corresponding to the setting of the pulse width setter 33, and exclusive OR gate 34 performs exclusive OR of the above BD multiplied signal. PI'! 1iE
Create a pulse width difference signal EXOR with T.

On the other hand, the above BD and HaI! The r signal is input to D flip-flops 35a and 35b, which output polarity signals POLa and POLb for the pulse width difference signal EXOR.

The above signals EXOR, POLa, and POLb are input to AND gates 37a and 37b, respectively, and as shown in FIG. Outputs the pulse width difference signal B, and connects each analog switch 38
a and 38b are turned on to input +Vs or -Vs to the integrating circuit 44, which is sequentially integrated to generate a correction signal Vl according to the magnitude of the BD pulse width and the set pulse width PWSET.
:Output MPN and set voltage setting value vsIllT to VCMP
VRI corrected by N! F is used as a voltage reference for the voltage control circuit 23. This causes the synchronization pulse signal BD to change to the set pulse width PI'! ml! ? The voltage correction is repeated until the AC output voltage waveform approaches the duty ratio of 1, and the ripple of the DC output current decreases.

Another embodiment of the invention is shown in FIG. FIG. 4 is a time chart showing the operation.

FIG. 3 shows a case where a thyristor rectifier is used in place of the rectifier 2 and transistor 4 in FIG.
A phase control circuit 25 and a gate drive circuit 26 are used in place of the base drive circuit 27 in the figure. Note that 9 is a transformer.

The signals A and B are generated by determining the on-period of the synchronizing pulse signal BD as a count value Y obtained by counting the clock pulse CLK by the counter 41, and comparing it with the set pulse width data X set by the pulse width setting device 43 and the comparison circuit 42. D flip-flop 3 according to the relationship of magnitude or coincidence
Which of 5a, 35b, and 35c is activated to hold the BD double signal until the next falling edge, and AND gate 37a, 37
This is done by inputting the information to b, and the rest is the same as in FIG.

Note that a fall delay circuit 40 is provided so that the data in the counter 41 is not cleared during the comparison of pulse width data, and a counter reset signal R5T is issued after a delay time TD.

〔Effect of the invention〕

As explained above, according to the present invention, AC-DC-AC
In the control circuit of the power supply device including the conversion, the reference voltage value for voltage control of the AC-DC converter is corrected so that the PItM pulse width of the AC output by DC-AC conversion is equal to the set pulse width. The waveform of the AC output voltage can be made into a waveform with a duty ratio close to 1, and therefore the ripple of the DC voltage or DC current obtained by rectifying the AC output voltage can be reduced.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing one embodiment of the present invention, Fig. 2 is a time chart showing the operation of Fig. 1, Fig. 3 is a circuit diagram showing another embodiment of the invention, Fig. 4 3 is a time chart showing the operation of FIG. 3, and FIG. 5 is a circuit diagram showing an example of a control circuit of a conventional power supply device. l... AC power supply 2, 10... Rectifier 3...
・Thyristor rectifier 4-8U, 8V, 8X, 8Y transistor 5...
Diode 6...Reactor 7...Capacitor 9...Transformer 11...Smoothing circuit 1
2...Current detector 13...Load 21.
...Current control circuit 22...PWM control circuit 23...
・Voltage control circuits 24a, 24b, 27...Base drive circuit 25...Phase control circuit 26...Gate drive circuit (8733) Agent Patent attorney Yoshiaki Inomata (and 1 other person) m m-m m −A −−−

Claims (1)

[Claims] AC-DC that obtains voltage-controlled DC output from an AC power supply
In a control circuit of a power supply device having a conversion unit and a DC-AC conversion unit that obtains an AC output whose pulse width is controlled from the DC output, the pulse width of the AC power is compared with a reference pulse width to determine a pulse width deviation including polarity. A pulse width comparison calculation circuit that calculates the signal, and a pulse width comparison calculation circuit that calculates the signal, and the AC-
A control circuit for a power supply device, comprising a voltage correction circuit that corrects a voltage reference for voltage control of a DC converter.