JPH0318432B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a DC power supply device that generates a stable DC voltage from a commercial AC voltage and supplies it to a load.

[Conventional technology]

FIG. 5 is a block diagram showing a conventional example of such a DC power supply device.

As seen in the figure, the conventional DC power supply device directly rectifies AC voltage from a commercial AC power supply 1 in a rectifier 2, then smoothes it in an input filter unit 3 to obtain a DC voltage, and then performs switching. In section 4, the DC voltage is intermittent at high frequency and then input to transformer 5.
The high-frequency AC voltage obtained from the next side is rectified by the rectifier 6 and converted into a DC voltage, and further smoothed by the output filter 7 and supplied to the load 8 as a DC voltage. When the switching section 4 fluctuates, the control circuit 9 detects the fluctuation amount and controls the on/off ratio (the width of the conduction period of the switching transistors constituting the switching section 4) in the switching section 4 so as to cancel out the fluctuation amount.
PWM (pulse width modulation) control was performed to supply a stable DC voltage to the load 8.

Such a conventional DC power supply device adopts a method in which the AC voltage from the commercial AC power supply 1 is first converted to DC voltage and then converted to high-frequency AC voltage by the switching unit 4. Therefore, the loss caused by the input rectifier unit 2 and the loss caused by the switching unit are reduced. A loss due to 4 occurs, and therefore,
The drawback was that the conversion efficiency from AC voltage to DC voltage was low.

Furthermore, it is necessary to increase the size of the cooling fins for cooling the input rectifying section 2, which makes it difficult to reduce the size and weight of the DC power supply device.

Furthermore, it is necessary to insert a reactor or provide an inrush current prevention circuit to prevent the inrush current for charging the capacitor in the input filter section 3 from flowing when commercial power is applied and thereby destroying the diode in the rectifier section 2. Another drawback was that the circuit configuration became complicated, leading to higher costs.

[Problem that the invention seeks to solve]

Therefore, the problems to be solved by the present invention are to reduce loss and increase conversion efficiency in a DC power supply device, to make the device smaller and lighter, and to reduce cost by simplifying the circuit configuration. It can be said that there is something to be done.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a DC power supply device that has high conversion efficiency, is small and lightweight, has a simple circuit configuration, and is inexpensive.

[Means and actions for solving problems]

In order to solve the above problems, in the DC power supply device according to the present invention, one end of the primary winding of the transformer and one end of the secondary winding are connected, and the other end of the primary winding is connected to the other end of the secondary winding. A first semiconductor switch and a second semiconductor switch having reverse breakdown voltage are connected in series with different polarities between the connection point of the primary winding and the secondary winding and the first semiconductor switch. An AC power supply is connected between the connection point of the semiconductor switch and the second semiconductor switch, and the first semiconductor switch and the second semiconductor switch are alternately turned on and off at a frequency higher than the frequency of the AC power supply. In the DC power supply device, the control circuit rectifies the output obtained from the tertiary winding of the transformer and supplies it to the load as a DC voltage. The DC voltage is detected, and the width of the period in which the first or second semiconductor switch is turned on is controlled according to the magnitude of the DC voltage. Furthermore, the polarity of the AC power source is monitored, and each time the polarity is reversed, the a first semiconductor switch and a second semiconductor switch;
The semiconductor switch is characterized in that the on and off periods of the semiconductor switch are reversed.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a circuit diagram showing an embodiment of the present invention.

In the figure, 1 is a commercial AC power supply, 5 is a high-frequency transformer, 6 is an output rectifier, 7 is an output filter, 8 is a load, 10 is a switching unit, 11 is a control circuit, 13 and 14 are semiconductor switches, respectively.
50 is a phase detector for AC voltage from the AC power supply 1;
60 is a synchronous oscillator that operates in synchronization with the phase of the AC voltage; 70 is a triangular wave generation circuit that generates a triangular wave in synchronization with the oscillation output from the synchronous oscillator 60; 8;
0 is a staircase wave generation circuit that also generates a staircase wave in synchronization, and 90 and 91 are comparators, respectively.

The alternating current voltage from the commercial alternating current power supply 1 is switched at a frequency higher than the frequency of the commercial alternating current by the switching unit 10 and inputted to the high frequency transformer 5, and a high frequency alternating current voltage is generated on the output side of the transformer 5. The AC output from the high frequency transformer 5 is rectified by an output rectifier 6, smoothed by an output filter 7, and supplied to a load 8 as a DC output.

The control circuit 11 detects the polarity of the AC input from the AC power supply 1 and the smoothed DC voltage supplied to the load 8, and controls a semiconductor switch having reverse breakdown voltage in the switching unit 10 so that the DC voltage is constant. In order to turn on and off switches 13 and 14 at high frequency, the pulse width of the gate pulses supplied to the gate electrodes of these switches 13 and 14 is controlled.

FIG. 2 is a waveform diagram showing operating waveforms of each part in the control circuit 11 of FIG. 1.

In the figure, an AC voltage waveform a from a commercial AC power supply 1 is shown. a is a sine wave voltage that switches between positive and negative every half cycle. During the period when a is positive, the semiconductor switch 13 in the switching unit 10 is turned on and off at high frequency to generate a high frequency AC voltage on the output side of the high frequency transformer 5, which is rectified and
Smooth and generate output voltage.

In order to keep this output voltage constant, it is necessary to control the pulse width of the gate pulse (FIG. 2f) applied to the gate electrode of the semiconductor switch 13 in accordance with the magnitude of the AC input voltage. When the AC input voltage is high, the pulse width is narrowed, and when the AC input voltage is low, the pulse width is controlled to be widened.

When the AC input voltage is positive, power cannot be supplied to the load 8 via the high frequency transformer 5 even if the semiconductor switch 14 in the switching section 10 is turned on. After the semiconductor switch 13 turns off the excitation energy stored in the switch 14
By turning on, it can be returned to the power supply side.

During the period when a is negative, the semiconductor switch 14 supplies power to the load 8, and a gate pulse is applied to the gate electrode of the semiconductor switch 14 to keep the DC output voltage supplied to the load 8 constant. (Figure 2g) Pulse width control is performed. At this time, the semiconductor switch 13 is operated to feed back the excitation energy stored in the high frequency transformer 5 to the power supply side while the switch 14 is on.

The circuit operation will be explained in more detail with reference to FIGS. 1 and 2.

As already partially explained, a is the commercial AC voltage waveform, b is the output signal waveform of the synchronous oscillator 60, c is the signal waveform output by the synchronous oscillator 60 every half cycle of the commercial AC voltage, and d is the triangular wave generation. The output signal waveform of the circuit 70, e is the staircase wave generation circuit 80
f is the output signal waveform of the comparator 90 that drives the semiconductor switch 13 (gate pulse)
The waveform g is the output signal (gate pulse) waveform of the comparator 91 that drives the semiconductor switch 14.

The synchronous oscillator 60 has a means for counting the number of output pulses b, and outputs a pulse signal shown in c every time it detects from the count result that the commercial AC voltage a exceeds a half cycle, and this pulse signal Therefore, the comparators 90 and 91 invert each output signal (gate pulse) every half cycle of the commercial AC voltage and output gate pulses f and g whose width is inversely proportional to the magnitude of the commercial AC voltage. The DC voltage supplied to 8 is kept approximately constant.

However, if the load 8 increases and the load current increases, the output voltage will decrease due to the internal impedance of the DC power supply. The pulse widths of the gate pulses f and g are controlled so as to lower the overall level of the staircase wave from the wave generating circuit 80, lengthen the conduction period of the semiconductor switch, and increase the output voltage.

In the embodiment described above with reference to FIGS. 1 and 2, when the frequency of the AC voltage from the commercial AC power source 1 changes, the frequency of the output signal of the synchronous oscillator 60 changes, and at the same time, the frequency of the AC voltage from the commercial AC power source 1 changes. When the magnitude changes, it is necessary to change the level of the staircase wave e, which complicates the control method and increases the number of parts used.

Furthermore, in order to make the transformer 5 and the output filter 7 smaller and lighter, it is necessary to increase the oscillation frequency of the synchronous oscillator 60 and improve the accuracy of the triangular wave generation circuit 70. Furthermore, a staircase wave generation circuit 80
The output voltage supplied to the load 8 is controlled by the waveform of the staircase waveform e generated by the step waveform e, and the pulse width of the gate pulse is controlled by detecting the output voltage and changing the overall level of the staircase waveform e. There was also a concern that the effect of the staircase waveform itself could not be fully utilized because of this.

FIG. 3 is a circuit diagram showing the main part (control circuit) of the second embodiment of the present invention, which makes it possible to eliminate the above-mentioned problems.

In the figure, 111 is a control circuit, 120 is an oscillator, 121 is a control IC, 130 is an AND circuit,
140 and 141 are OR circuits, 150 and 1 respectively
51 are drive circuits, respectively.

FIG. 4 is a waveform diagram showing operating waveforms of each part in the circuit shown in FIG. 3.

Please refer to FIGS. 3 and 4. An oscillator 120 in the control circuit 111 generates a pulse P and its inverted pulse during a positive period and a negative period of the commercial AC voltage a, respectively. The control IC 121 detects the output voltage U supplied to the load 8, compares it with a reference voltage (not shown), and generates a high-frequency pulse train Q having a pulse width proportional to the difference voltage and its inverted pulse.

Output P of oscillator 120 and control IC 121
Based on the output Q of Signal (P・+・
Q) respectively.

In order to drive semiconductor switches 13 and 14 as gate pulses, the M and N signals are amplified and insulated via drive circuits 150 and 151, and then supplied to the gate electrodes of semiconductor switches 13 and 14, respectively.

In Figure 4, M, N during a half cycle of commercial power supply
Although the number of pulses of the signal is shown to be small, it is technically easy to increase the number of pulses to a large extent, thereby making it possible to significantly downsize the high frequency transformer 5 and the output filter 7.

〔Effect of the invention〕

As explained above, according to the present invention, in a DC power supply device, it is possible not only to improve the conversion efficiency, reduce the size and weight of the device, and reduce the cost, but also to further stabilize the DC output supplied to the load. It has the advantage of being able to

In other words, regardless of the magnitude of the commercial AC voltage on the input side, the voltage of the DC output supplied to the load side is detected and the conduction period of the semiconductor switch is changed to control the output voltage. This has the advantage that the DC output can be stably controlled even if the frequency of the current changes rapidly. Moreover, especially according to the second embodiment, the control circuit can be configured very easily and reliability is improved. Furthermore, according to the present invention, there is also the advantage that higher frequencies can be easily achieved.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing one embodiment of the present invention, Figure 2 is a circuit diagram showing an embodiment of the present invention.
The figure is a waveform diagram showing the operating waveforms of each part in the circuit shown in Fig. 1, Fig. 3 is a circuit diagram showing the main parts of another embodiment of the present invention, and Fig. 4 is a waveform diagram showing the operating waveforms of each part in the circuit shown in Fig. 3. FIG. 5 is a waveform diagram showing operating waveforms of each part, and FIG. 5 is a block diagram showing a conventional example of a DC power supply device. Description of symbols, 1... AC power supply, 5... High frequency transformer, 6... Output rectifier, 7... Output filter part, 8... Load, 10... Switching part, 11
...Control circuit, 13,14...Semiconductor switch,
50... Phase detector, 60... Synchronous oscillator, 70
...Triangular wave generation circuit, 80...Staircase wave generation circuit,
90, 91... Comparator, 111... Control circuit, 1
20... Oscillator, 121... Control IC, 130
...AND circuit, 140,141 ...OR circuit, 1
50,151...Drive circuit.

Claims (1)

[Claims] 1. One end of a primary winding and one end of a secondary winding of a transformer are connected, and a reverse withstand voltage is connected between the other end of the primary winding and the other end of the secondary winding. A first semiconductor switch and a second semiconductor switch having different polarities are connected in series, and a connection point between the primary winding and the secondary winding and the first semiconductor switch and the second semiconductor switch are connected in series. By comprising a control circuit that connects an AC power supply between the connection point of the AC power supply and turns the first semiconductor switch and the second semiconductor switch on and off alternately at a frequency higher than the frequency of the AC power supply, In the DC power supply device in which the output obtained from the tertiary winding of the transformer is rectified and supplied to the load as a DC voltage, the control circuit detects the DC voltage supplied to the load and determines the magnitude of the DC voltage. Accordingly, the width of the period in which the first or second semiconductor switch is turned on is controlled, and the polarity of the AC power source is monitored, and each time the polarity is reversed, the first semiconductor switch and the second semiconductor switch are switched on.
A DC power supply device characterized in that the on and off periods of the semiconductor switches are mutually inverted. 2. In the DC power supply device according to claim 1, the control circuit includes a first circuit that generates a staircase wave in synchronization with the cycle of the AC power supply, and a second circuit that generates a triangular wave in synchronization with the cycle of the AC power supply. A first comparison step in which a first gate pulse is generated and supplied to the first semiconductor switch by comparing the levels of the step wave from the first circuit and the triangular wave from the second circuit. a second comparator that similarly generates a second gate pulse and supplies it to the second semiconductor switch; and a second comparator that generates a second gate pulse and supplies it to the second semiconductor switch; means for controlling the first and second comparators to mutually invert the phases of the gate pulses; and means for controlling the generation level of the staircase wave according to the magnitude of the DC voltage supplied to the load. A DC power supply device comprising: means for controlling the first circuit. 3. In the DC power supply device according to claim 1, the control circuit includes an oscillator that outputs a pulse train P and its inverted pulse train according to the polarity of the input voltage from the AC power supply, and an oscillator that is supplied to a load. A control IC that compares the DC voltage and a reference voltage and outputs a pulse train Q having a pulse width proportional to the difference voltage and its inverted pulse train, and determines the polarity of the AC input voltage from the pulse trains P and Q. the first semiconductor switch and the second semiconductor switch according to the
The first inverts each conduction period of the semiconductor switch.
and a second gate pulse for each of the first and second gate pulses.
and a logic circuit that supplies gate electrodes of each of the second semiconductor switches.