JPH02131368A - Dc power supply - Google Patents

Abstract

PURPOSE:To contrive to miniaturize and lighten an apparatus by providing a control circuit with a pulse-with correction circuit detecting the change of the primary side current of a transformer within a conversion period and controlling ON-pulse width also through the change. CONSTITUTION:A pulse-width correction circuit 220 detecting the change of the primary side current of a transformer 5 within one conversion period and controlling ON-pulse width also through the change is provided at a control circuit. That is, the ON-pulse width of respective semiconductor switches 11-16 is determined from the change of the primary side current of the transformer 5 within one conversion period and from each line voltage. Therefore, even if the peak value of a current pulse changes under the influence of inductance of a reactor used for the exciting current of the transformer 5 and an output filter 7, the change of current accompanying the change of the peak value can be corrected and an input current can be formed into a sine wave with a good accuracy. Thus, the inductance of the reactor used in the transformer 5 and output filter 7 can be designed smaller so that an apparatus can be miniaturized and lightened.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a small and lightweight DC power supply device that can convert input current into a sine wave.

``Prior art'' Figure 3 shows a conventional example of a DC power supply that aims to convert the input current into a sine wave. A commercial three-phase AC power supply 1 is connected to a power converter 10 via an input filter 3, the output side of the power converter 10 is connected to the primary side of a transformer 5, and the secondary side of the transformer 5 is connected to an output rectifier. 6, and the output side of the output rectifier 6 is connected to a load 8 via an output filter 7. In the power conversion section, semiconductor switches 11.14 are connected in series, semiconductor switches 12.15 are connected in series, semiconductor switches 13.16 are connected in series, and these three series connections are connected in parallel to form a transformer 5. The R wire is connected to the connection point of the semiconductor switch 11.14, the S wire is connected to the connection point of the semiconductor stitch 12.15, and the semiconductor switch 13.
T wires are connected to each of the 16 connection points. The commercial three-phase AC power supply 1 is connected to the input voltage detection circuit 201 of the control circuit 20 .
The output side of is connected to the comparator 202 and the switching element on order determining circuit 204, and the switching element on order determining circuit 204 is connected to the sawtooth wave generator 203, and the sawtooth wave generating circuit 2
The output side of 03 is connected to the other input side of comparator 202. The output side of the comparator 202 and the switch element ON order determining circuit 204 are connected to drive signal generation circuits 211-216, and the drive signal generation circuits 211-216 are connected to the semiconductor switches 11-16, respectively. The AC voltage from the three-phase AC power supply 1 has its noise reduced by the input filter section 3, and is further converted into a commercial three-phase voltage by the power conversion section 10.
Switching occurs at a frequency higher than the frequency of the phase AC power supply 1, and a high frequency AC voltage is generated on the output side of the transformer 5. The AC output from the 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. In the control circuit 20, each line voltage waveform e from the commercial three-phase AC power supply l detected by the input voltage detection circuit 201 is
The comparator 202 compares the sawtooth wave f' with a constant angle generated by the sawtooth wave generator 203, and obtains a pulse width signal g' proportional to the line voltage.
The on-pulse width of 6 is controlled to be proportional to each line voltage, the switching element on-order determining circuit 204 determines the on-order of each switching element, and the drive signal generating circuits 211-216 control the on-pulse width of each semiconductor switch 11-16 to be proportional to each line voltage. Sends an on signal. Figure 4 shows an example of the waveform of each part. Figure 4 shows the waveforms of voltage pulses and R-phase current pulses applied to the transformer when the order of power supply phases is from medium to high to low line voltage. One cycle of commercial input is divided into a large number of sections according to the conversion period of the power converter 10, and within each section, power is supplied in the phase order of medium->high->low line voltage. For example, section A in Figure 4
Each line voltage and sawtooth wave, and each switch element 11 ~
The relationship with the ON signal of 16 is as shown in Figure 5. That is, since the voltage between T and R is "medium" from time 1 to L2, switch 13.14 is turned on to supply power from T to R to the load side, and then from time t2 to L3, switch 1 is turned on.
3, 15, and t3 to t4, the switch 11.15 is turned on to supply power from ST (large) and R-S (small), respectively, and then the switch 12.16 is turned on to turn on the transformer 5. Returns excitation energy to the power source.
At this time, the on time of each switch is determined by comparing each line voltage with a sawtooth wave with a constant slope θ, and the on time is controlled so that it is proportional to each line voltage, that is, a sine wave. The average value of current in a certain unit time is proportional to the product of the current pulse height width and pulse width (time), so if the current pulse height value is constant, the width of the current pulse can be made proportional to the sine wave. This allows the current to be controlled in a sinusoidal manner. Therefore, in this conventional example, by performing the series of operations described above, one of the transformers 5 is
When the peak value of the current pulse flowing to the next side is kept constant, for example, the R-phase current becomes a collection of current pulses where the area of each current pulse is proportional to a sine wave, as shown in Figure 4 (b). By smoothing this current pulse with the input filter section 3, the input current can be made into a sine wave. However, when the peak value changes, the area of each 1i current pulse is not proportional to the sine wave, so the distortion rate of the input current increases. Therefore, in order to convert the input current into a sine wave, it is necessary to suppress the change in the peak value of each current pulse on the primary side of the transformer 5 to a small value. The reason why the peak value of the current pulse changes is that the excitation current and output current ripple of the transformer 5 are superimposed on the primary current of the transformer, so the excitation inductance of the transformer 5 and the output filter section If the value of the inductance of the actor used in 7 is increased, the excitation current and output current ripple can be reduced, and the change in the peak value of the current pulse can also be suppressed to a small value.

Based on the above, in conventional devices, the excitation inductance of the transformer and the value of the actor used in the output filter are designed to be large in order to reduce the change in the peak value of the current pulse and convert the input current into a sine wave. However, there was a problem in that the equipment became larger and the cost increased. "Means for Solving the Problem" According to the present invention, a control circuit is provided with a pulse width correction circuit that detects a change in the primary current of a transformer within one conversion period and controls the on-pulse width based on this change. establish. In other words, the on-pulse width of each semiconductor switch is determined from the change in the primary current of the transformer within one conversion cycle and each line voltage. In this way, a small, lightweight, and economical DC power supply device that can convert the input current into a sine wave can be obtained. ``Embodiment'' Figure 1 is a circuit diagram showing an embodiment of this invention. In this invention, a pulse width correction circuit 220 is provided. The pulse width correction circuit 220 includes a current detection circuit 221, a sample hold circuit 222, a scratchiness inversion circuit 223, and an adder 22.
Consists of 4. Other numbers that are the same as those in Figure 3 are in Figure 3.
Shows the same thing as the figure. In the embodiment of the present invention, the operation of the main circuit is the same as that of the conventional device, so a description thereof will be omitted. show.

Figure 2 shows that due to the influence of the inductance of the actor used in the transformer 5 and output filter section 7, the peak value of the R-phase current pulse is not constant, and there is a difference of Δi between the start and end points of the current pulse. In the case, the pulse width correction circuit 220
The waveforms of each part are shown. The primary side current waveform of the transformer (FIG. 2a) detected by the current detection circuit 221 is input to the sample and hold circuit 222 and the adder 224. The sample hold circuit 222 outputs the value at the rise of the current to the transformer 5.
The primary current is maintained until it becomes zero, and the waveform shown in FIG. 2b is output to the polarity inversion circuit 223.

The polarity inversion circuit 223 inverts the polarity of the waveform shown in FIG. 2B and outputs the inverted waveform shown in FIG. 2C to the adder 224. Adder 224 adds the primary current waveform of the transformer shown in FIG. 2A and the waveform shown in FIG. 2C. Therefore, the output of the adder 224 is 1 of the transformer 5 as shown in FIG. 2d.
The waveform corresponds only to the change in the primary current of the transformer, and the pulse width correction circuit 220 can detect only the change in the primary current of the transformer.

The increase Δi in the primary current of the transformer 5, which is the output of the adder 224, is input to the sawtooth generator 203, and according to the magnitude of the increase Δi, an angle θ2 larger than the sawtooth f' of the conventional example is generated.
Generates a sawtooth wave f with . The comparator 202 compares each line voltage waveform e with the sawtooth wave f, and generates a pulse width signal g whose pulse width is smaller than the conventional pulse width signal g'. Therefore, even if the peak value of the current pulse increases due to the influence of the inductance of the actor used in the transformer 5 or output filter section 7, the increase in current due to the increase Δl can be equivalently reduced by narrowing the pulse width. It is possible to make the product of the pulse width and peak value of the current pulse equal to that when the peak value of the current pulse does not change. For the reasons stated above, the transformer 5 and the output filter section 7
By designing the inductance of the actuator to be small, even if the peak value of the current pulse increases, the increase in current due to the increase in the peak value Δl of the current pulse can be suppressed by narrowing the pulse width. As a result, the input current of each phase becomes a collection of current pulses in which the area of each current pulse is proportional to a sine wave, and by smoothing this current pulse with the manual filter 3, the input current can be made into a sine wave.

In this embodiment, control is performed by detecting the primary current of the transformer, but the same results can be obtained by detecting and controlling the current of each semiconductor switch 1l to 16. Needless to say.

"Effects of the Invention" As explained above, according to the present invention, even if the peak value of the current pulse changes due to the excitation current of the transformer, the influence of the inductance of the actor used for the output filter, the current due to the change changes. It is possible to correct the variation and make the input current into a sine wave with high accuracy, so it can be used for transformers and output filters, and it can be used to reduce the inductance of the actuator.
It is possible to make the device more compact and economical.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a DC power supply device according to the present invention, FIG. 2 is a diagram showing waveforms of various parts in the pulse correction circuit 220 and input/output signals of the comparator 202, and FIG. 3 is a diagram showing a conventional DC power supply device. 4 is a diagram showing an example of the voltage applied to the transformer and the current pulse flowing to the R phase. FIG. 5 is a block diagram showing the voltage applied to the transformer and an example of the current pulse flowing to the R phase. FIG. , 14, 15, and 16. FIG. Patent applicant Nippon Telegraph and Telephone Corporation

Claims (1)

[Claims] (1) From a three-phase AC power source and a plurality of semiconductor switches that switch at a frequency higher than the frequency of the three-phase AC power source via the three-phase AC power source and an input filter to generate a high-frequency AC voltage on the output side of the transformer. a power converter, an output rectifier and an output filter that rectify and smooth the output of the transformer, and sequentially turn on the corresponding semiconductor switches with an on-pulse width proportional to each line voltage from the three-phase AC power supply. , the power is supplied to the load side from each line voltage and the excitation energy of the transformer is fed back to the three-phase AC power supply via the semiconductor switch, so that a series of operations are performed within one conversion cycle. In a DC power supply device that includes a control circuit that controls a conversion section, the control circuit detects a change in the primary current of the transformer within the conversion period, and controls the on-pulse width based on this change as well. A DC power supply device characterized by comprising a circuit.