JP2704519B2 - DC power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a DC power supply device which has high conversion efficiency, can be reduced in size and weight, and can make a sine wave input current.

[Conventional technology]

FIG. 5 is a block diagram showing a conventional DC power supply device. As shown in FIG. 1, in the conventional DC power supply, the AC voltage from the three-phase AC power supply 1 is full-wave rectified by the input rectifier 2 and smoothed by the input filter 3 composed of a choke and a capacitor. After that, the DC voltage is turned on and off in the switching unit 4 at a high frequency, and the high-frequency AC voltage obtained from the secondary side of the transformer 5 is output to the output rectification unit 6.
And a DC voltage obtained by rectification and smoothing by an output filter 7 including a choke and a capacitor, and the DC voltage is supplied to a load 8. Further, the control circuit 9 detects the output voltage, performs pulse width modulation control for controlling the ON feedback of the switch in the switching unit 4, and stabilizes the output DC voltage.

[Problems to be solved by the invention]

However, in this conventional DC power supply, three-phase AC power supply 1
Since the AC voltage is once converted into a DC voltage and then converted into a high-frequency AC voltage by the switching unit 4, a large loss occurs in the input rectifying unit 2 and the switching unit 4, and the conversion efficiency is reduced. As a result, the size of the cooling fins increases, the number of parts increases, and the size of the device increases.
There is a problem that it becomes expensive. Further, since the three-phase AC power supply 1 is once subjected to full-wave rectification, the input current flows only during the period when the line voltage is the highest, and there is a problem that the input current includes many harmonics. Therefore, in the present invention, as one method of solving such a problem, the three-phase AC voltage is directly switched at a high frequency on the primary side of the transformer without rectification and converted to a high-frequency voltage, and the two-phase AC voltage is not changed. It is proposed that half-wave rectification be performed on the secondary side to supply DC power to the load. In this case, it is necessary to reset the transformer, so in order to reset the transformer efficiently,
The present invention proposes that the excitation energy of the transformer is fed back to the three-phase AC power supply via a pair of semiconductor switches every one conversion cycle of switching.

[Means for solving the problem]

In order to eliminate the above-mentioned drawbacks, the present invention provides a three-phase AC power supply, an input filter for reducing the noise component of the three-phase AC power supply, and switching at a frequency higher than the frequency of the three-phase AC power supply. A switching section comprising a plurality of semiconductor switches for generating a high-frequency AC voltage on the side;
An output rectifier and an output filter for rectifying and smoothing the AC output from the transformer, and the corresponding semiconductor switches are sequentially turned on with an on-pulse width proportional to the line voltage from the three-phase AC power supply. The switching unit is controlled so that a series of operations of supplying power to the load side and returning the excitation energy of the transformer to the three-phase AC power supply via the semiconductor switch in one conversion cycle are performed. A DC power supply device characterized by comprising a control circuit.

[Action]

According to such a DC power supply device, since the AC voltage from the three-phase AC power supply can be directly converted to the high-frequency AC voltage by the switching unit, the number of power conversion stages can be reduced, and the conversion efficiency is improved. In addition, since the input current can be made into a sine wave, harmonic components of the input current can be significantly reduced, and no noise or the like is exerted on devices sharing a power supply.

〔Example〕

FIG. 1 is a circuit diagram showing one embodiment of the present invention. In the figure, 1 is a three-phase AC power supply, 3 is an input filter, 5 is a 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, and 12 to 17 are semiconductors. Switch.

The AC voltage from the three-phase AC power supply 1 is switched by the switching unit 10 via the input filter 3 at a frequency higher than the frequency of the commercial three-phase AC power supply, and generates a high-frequency AC voltage on the output side of the transformer 5. This 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 each line voltage from the three-phase AC power supply 1, performs control so that the on-pulse width of the semiconductor switch inserted between each line is proportional to the line voltage, and turns on any semiconductor switch. To decide.

FIG. 2 is a block diagram showing the control circuit 11. The control method of the switching unit 10 will be described with reference to FIG.

The on-pulse width of the semiconductor switches 12 to 17 is a waveform obtained by dividing and rectifying the _RS line voltage V _RS , the _ST line voltage V _ST , and the _TR line voltage V _TR by the full-wave rectifier circuits 21 to 23. And the pulse generation circuit
The on-pulse width is determined by comparing the outputs from 24 to 26 with the comparators 27 to 29, and can be set to an on-pulse width proportional to the line voltage. More specifically, the switch determination circuit 30 converts a reference clock pulse having a frequency in which a three-phase AC voltage can be regarded as substantially constant within one cycle, for example, a frequency of 20 to 30 kHz to a phase of a maximum or second largest voltage at the time Q. It is given to the corresponding pulse generation circuit. Here, assuming circuit 24,
The pulse generating circuit 24 outputs to the comparator 27 a signal a which rapidly drops in synchronism with the reference clock pulse as shown in FIG. The comparator 27 compares the detection signal of the input voltage and the signal a, generates a pulse width signal X _1. The switch determining circuit 30 with the end pulse width signal X _1, gives a signal to the pulse generating circuit 25, the circuit 25 outputs a signal c as shown in FIG. 4 to the comparator 28,
The comparator 28 compares the detection signal and the signal c of the input voltage, generates a pulse width signal X _2. Similarly, the switch determining circuit 30 upon termination of the pulse width signal X _2, gives a signal to the pulse generating circuit 26, the circuit 26 is a signal as shown in FIG. 4 e
Outputs to the comparator 27, the comparator 29 compares the detection signal and the signal e of the input voltage, generates a pulse width signal X _3. The switch determining circuit upon termination of the pulse width signal X ₃
30 generates a pulse width signal X _4, this pulse width signal X ₄ is terminated immediately before the occurrence of the next reference clock pulses in the switch determination circuit 30. As can be seen from the above description, the reference clock pulse supplied from the switch determination circuit 30 determines one conversion period described later. Next, which semiconductor switch is turned on will be described. Comparators 31-33
By comparing the line voltage with the ground voltage, the positive / negative relationship between the line voltages is expressed by the outputs of the three comparators 31 to 33. The switch decision circuit 30 decides three sets of two semiconductor switches based on the three signals so that a current flows from the positive to the negative of the line voltage through the transformer.
Further, two semiconductor switches for returning the excitation energy of the transformer to the three-phase AC power supply are determined. For example, R
Assuming that power is supplied to the load side in the order of −S, ST, TR, and then the excitation energy is fed back to RS, at point Q in FIG. Turn on R
-S, power is supplied from the
6, Turn on the semiconductor switches 12 and 17 in sequence to switch between S-T, T-
After power is supplied to the load side from between R, the switches 13 and 15 are turned on, and power is fed back between R and S.

Here, the control operation will be described in detail with reference to FIG. 4 showing the waveforms of respective parts at the point Q in FIG. Curves b, d, and f shown in FIG. 4 represent the line voltages V _RS , V _ST , and V _TR and the pulse generation circuit.
24 to 26 are curves for explaining the intersections with the output pulses a, c, and e, and do not show the waveforms of the line voltages _VRS , _VST , and _VTR . Switch decision circuit 30 shown in FIG.
When an operation signal comes from the pulse generator 24 to the pulse generator 24, the pulse generator 24 generates one pulse a shown in FIG. 4 and compares it with the output b of the full-wave rectifier 21 shown in FIG. As a result, the ON pulse width of the semiconductor switch inserted between R and S is determined, and this ON pulse width signal is input to the switch determination circuit 30. The switch decision circuit 30 is R
Since the -S voltage is positive, the semiconductor switch 1 shown in FIG.
In order to turn on the 2,16, it sends a pulse width signal X ₁ shown in FIG. 4 to the driving circuit 34 and 38 of the semiconductor switches 12 and 16, immediately after the semiconductor switch 12, 16 is turned off, the pulse shown in FIG. 2 An operation signal is sent to the generation circuit 25. The pulse generation circuit 25 generates one pulse c shown in FIG. 4 and compares it with the output d of the full-wave rectification circuit 22 shown in FIG. The on-pulse width of the semiconductor switch is determined, and this on-pulse width signal is input to the switch determination circuit 30. Since the switch determining circuit 30 is a negative voltage across S-T, the driving circuit 36 to turn on the semiconductor switch 14, 16 shown in FIG. 1, pulse width signal X ₂ semiconductor switches 14 and 16 shown in FIG. 4 , 38, and immediately after the semiconductor switches 14, 16 are turned off, the pulse generation circuit 2 shown in FIG.
Send an operation signal to 6. The pulse generating circuit 26 generates one pulse e shown in FIG. 4 and generates a full-wave rectifier circuit shown in FIG.
The on-pulse width of the semiconductor switch inserted between T and R is determined by comparing the output f of 23 with the comparator 29, and this on-pulse width signal is input to the switch determination circuit 30. Since the switch determining circuit 30 is a negative voltage across T-R, in order to turn on the semiconductor switch 12 and 17 shown in FIG. 1, the driving circuit 34 of the fourth semiconductor switch 12, 17 the pulse width signal X ₃ shown in FIG. , 39 and semiconductor switches 12,17
Semiconductor switch but in order to turn on the semiconductor switch 13, 15 immediately after off, a pulse width signal X ₄ shown in FIG. 4
The excitation energy of the transformer is fed back to the three-phase AC power supply side. Here, pulse width signal X ₄ is terminated immediately before generation of the next reference pulse signal as described above applied from the switch determining circuit 30 as described above, the excitation of the transformer 5 within the period of the pulse width signal X ₄ The energy is fed back to the three-phase AC power supply, and the reset of the transformer 5 is completed. For the pair of semiconductor switches pulse width signal X ₄ is given, the line voltage V _RS, V _ST,
Of V _TR, by the power supply direction to the load to select the pair of semiconductor switches corresponds to a large line voltage of the most value in the opposite polarity of the voltage, thereby completing the reset of the transformer 5 in a short time And one conversion cycle can be shortened. By repeating this operation, power is supplied from each line to the load with an on-pulse width proportional to the line voltage in one conversion cycle, and the input current is removed from the switching frequency component by the input filter 3 to become a sine wave. Further, since the pulse generation circuit has a function of changing the pulse gradient depending on the output voltage, the output voltage is a stable DC voltage. For example, when the output voltage increases, the fourth
As shown in the figure, α becomes large, the slope becomes steep, and the operation is performed such that the on-pulse width is reduced while making the on-pulse width proportional to the line voltage.

〔The invention's effect〕

As described above, in the DC power supply device according to the present invention, the excitation energy of the transformer is fed back to the three-phase AC power supply via the pair of semiconductor switches for each switching cycle of the switching of the semiconductor switch, and reset. Since the transformer can be reset reliably, the energy loss can be reduced, and the switching unit has the function of directly converting the AC voltage from the three-phase AC power supply to the high-frequency AC voltage. Reduction can be achieved,
There is an advantage that conversion efficiency is improved. In addition, radiation fins for cooling the input rectifier are not required, and by increasing the switching frequency, the size and weight of the device can be reduced.
In addition, there is an advantage that cost can be reduced. Furthermore, since power is supplied from each line to the load side in one conversion cycle with an on-pulse width proportional to the line voltage, the input current can be made a sine wave. Therefore, there is an advantage that the harmonic component of the input current can be greatly reduced, and the device sharing the power supply is not affected by noise or the like.

[Brief description of the drawings]

1 to 4 are diagrams for explaining an embodiment of the present invention, and FIG. 5 is a diagram for explaining a conventional DC power supply device. DESCRIPTION OF SYMBOLS 1 ... 3-phase alternating current power supply, 2 ... Input rectification part 3 ... Input filter 4, ... Switching part 5 ... Transformer, 6 ... Output rectification part 7 ... Output filter, 8 ... Load 9 ... Control Circuit, 10 Switching section 11 Control circuit, 12 to 17 Semiconductor switch 21 to 23 Full-wave rectifier circuit, 24 to 26 Pulse generation circuit 27 to 29 Comparator, 30 Switch Decision circuits 31-33 Comparators, 34-39 Drive circuits 40-42 Inverting circuits

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Shuichi Ushiki Examiner Hiroshi Fujii, Ojijin Electric Co., Ltd. 1-18-1 Takada, Toshima-ku, Tokyo (56) References JP-A-1-202164 (JP, A )

Claims (1)

(57) [Claims] 1. A three-phase AC power supply, an input filter of the three-phase AC power supply, and a plurality of semiconductors that switch at a frequency higher than the frequency of the three-phase AC power supply and generate a high-frequency AC voltage at an output side of a transformer. A DC power supply device comprising: a switching unit composed of a switch; an output half-wave rectifying unit that rectifies and smoothes an AC output from the transformer; and an output filter, wherein an ON pulse width is proportional to each line voltage from the three-phase AC power supply. A series of operations of sequentially turning on the semiconductor switches corresponding to this, supplying power to the load side from between the lines, and returning the excitation energy of the transformer to the three-phase AC power supply via the semiconductor switches are performed as follows. A DC power supply device comprising a control circuit for controlling the switching unit so as to perform the conversion at a conversion cycle.