JP2016127645A - Multi-output switching power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-output switching power supply device in which inputs of a plurality of switching power supplies are connected in series and an input voltage is regulated in such a manner that the input voltage does not exceed an input voltage specification of each of the switching power supplies.SOLUTION: A multi-output switching power supply device comprises: a first DC-DC converter which outputs a first DC voltage and a second DC-DC converter which outputs a second DC voltage, inputs of the first and second DC/DC converters being connected to a DC power supply in series and outputs thereof being connected to a load in series; and a third DC-DC converter of which the input is connected to the input of the second DC-DC converter in parallel and which outputs a third DC voltage. The multi-output switching power supply device also comprises a control circuit by which input voltages of the DC-DC converters are detected to generate an average value, the first and second DC-DC converters are controlled in accordance with a difference between the input voltages and the average value and output voltages and the third DC-DC converter is controlled in accordance with the third DC voltage.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a switching power supply that can be used even at a high input voltage.

  For example, a factory has a high input voltage power system such as AC480V. However, many parts for general power supply devices are made on the assumption that they are used at a maximum of AC 300 V or less, and there are few parts corresponding to AC 480 V, or they are very expensive. Therefore, a means for connecting power supply devices in series can be considered. However, there is a possibility that the input or output will be unbalanced and the power supply cannot be used efficiently or a dangerous state will occur.

  In the case of the power supply voltage AC480V, it is conceivable to connect the switching power supplies with the input maximum voltage AC240V input in series. In this case, it is necessary to limit the input voltage of each switching power supply. Therefore, a plurality of switching power supplies, the input is connected in series and the output is connected in parallel, the average value of the input voltage of each switching power supply is obtained, the difference signal between the average value and the input voltage of the switching power supply, Feedback is provided to the sense input of the output voltage of the switching power supply. As a result, the output voltage of each switching power supply becomes equal, and the value of the input voltage is controlled to be equal to the average value of the input voltage. For this reason, the input voltage of each switching power supply becomes equal, as a result, the output current becomes equal, and both the input voltage and the output current are balanced (prior art 1).

JP-A-11-004579

  Prior art 1 is effective for balancing input and output. However, since a plurality of switching power supplies are connected in series and outputs are connected in parallel, each switching power supply has a variation in characteristics of the switching power supply. Input voltage and output current are not equal. It is necessary to prevent the input voltage from exceeding the input voltage standard of each switching power supply due to variations. In addition, an electronic device as a load often requires a plurality of DC voltages. Therefore, we propose a multi-output switching power supply that is more effective for adjusting the input voltage.

  In order to solve the problem, the present invention provides a first DC-DC converter and a second DC voltage that output a first DC voltage, the input of which is connected in series to a DC power source and the output of the DC power supply is connected in series. And a second DC-DC converter that outputs a third DC-DC converter that has an input connected in parallel to the input of the second DC-DC converter and outputs a third DC voltage. This is a multi-output switching power supply device that supplies a voltage to a load. Further, an average value detecting unit for detecting an input voltage of the first converter and an input voltage of the second or third DC-DC converter and outputting an average value is provided, and the input voltage and the average value of the first converter are calculated. The first DC-DC converter is controlled according to the difference and the first DC voltage, and the difference between the input voltage and the average value of the second or third DC-DC converter and the second DC voltage are controlled. A control circuit is provided that controls the second DC-DC converter and controls the third DC-DC converter according to the third DC voltage.

  Using a DC-DC converter with a low input voltage, power conversion of a high-voltage DC power supply is possible.

The block diagram which shows Example 1 of this invention The block diagram which shows Example 2 of this invention

FIG. 1 shows a block diagram of Embodiment 1 of the present invention. The present invention will be described with reference to FIG.
DC power supply 1, capacitor C1, and capacitor C2 are connected in series. The input of the DC-DC converter 2 is connected in parallel with the capacitor C1, and the input of the DC-DC converter 3 is connected in parallel with the capacitor C2. The input of the DC-DC converter 2 is connected to the primary winding of the transformer T1 and the switching element Q1 in series. The secondary winding of the transformer T1 is connected to a rectifying / smoothing circuit including a diode D1 and a capacitor C4. Output. The DC-DC converter 3 has an input in which a primary winding of the transformer T2 and a switching element Q2 are connected in series. A secondary winding of the transformer T2 is connected to a rectifying / smoothing circuit including a diode D2 and a capacitor C5. Output. Outputs of the respective DC-DC converters are connected in series, and a voltage Vo obtained by adding the DC voltage Vo1 and the DC voltage Vo2 is generated between the terminal +1 and the terminal −1 and supplied to a load (not shown). Further, the input of the DC-DC converter 4 is connected to the capacitor C2. The input of the DC-DC converter 4 is connected to the primary winding of the transformer T3 and the switching element Q3 in series. The secondary winding of the transformer T3 is connected to a rectifying / smoothing circuit including a diode D3 and a capacitor C6. Output.

  The average value detection circuit 6 receives a DC voltage V1 of the DC power supply 1 and a DC voltage V2 at a connection point between the input of the DC-DC converter 2 and the input of the DC-DC converter 3, and the DC voltage V1 and the DC voltage V2 are converted into DC. The average value Vav of the input voltage of the DC converter 2, that is, the voltage Vc1 of the capacitor C1, and the input voltage of the DC-DC converter 3 and the DC-DC converter 4, that is, the voltage Vc2 of the capacitor C2, is output to the difference generation circuit 7. The difference generation circuit 7 generates a voltage Vc1 of the capacitor C1 and a voltage Vc2 of the capacitor C2 from the DC voltage V1 and the DC voltage V2, and a difference Vdef1 between the average value Vav from the average value detection circuit 6 and the voltage Vc1 of the capacitor C1; A difference Vdef2 between the average value Vav and the voltage Vc2 of the capacitor C2 is output to the control circuit 5.

  The control circuit 5 receives the voltage Va at the terminal +1, the voltage Vb at the connection point between the output of the DC-DC converter 2 and the DC-DC converter 3, and the DC voltage Vc that is the output voltage Vo3 of the DC-DC converter 4. Then, signals corresponding to the output voltages Vo1, Vo2 and Vo3 are generated. The control circuit 5 generates a PWM signal G1 corresponding to the difference Vdef1 input from the difference generation circuit 7 and the output voltage Vo1, and drives the switching element Q1 of the DC-DC converter 2 on and off. Further, the control circuit 5 generates a PWM signal G2 corresponding to the difference Vdef2 and the output voltage Vo2 input from the difference generation circuit 7, and drives the switching element Q2 of the DC-DC converter 3 on and off. Furthermore, the control circuit 5 generates a PWM signal G3 corresponding to the output voltage Vo3, and drives the switching element Q3 of the DC-DC converter 4 on and off.

Since the capacitor C1 and the capacitor C2 are connected in series, the charging current is the same. For this reason, the voltage Vc1 of the capacitor C1 and the voltage Vc2 of the capacitor C2 are determined by the discharge current. In the multi-output switching power supply device of the present invention, a DC-DC converter 3 and a DC-DC converter 4 are connected in parallel to a capacitor C2. Therefore, in order to balance the voltage Vc1 of the capacitor C1 and the voltage Vc2 of the capacitor C2, the power output from the DC-DC converter 2 and the DC-DC converter 3 that generate the DC voltage Vo supplied to the load can be made the same. However, in the multi-output switching power supply device of the present invention, the DC-DC converter 2 is controlled according to the voltage Vc1 and the output voltage Vo1 of the capacitor C1, and the DC-DC converter 3 is set to the voltage Vc2 and the output voltage Vo2 of the capacitor C2. Accordingly, the discharge currents of the capacitor C1 and the capacitor C2 are substantially the same, and Vc1 and Vc2 are balanced.
For example, when the load of the DC-DC converter 4 increases, the input current of the DC-DC converter 4, that is, the discharge current of the capacitor C2 increases. Then, the voltage Vc2 of the capacitor C2 decreases and the voltage Vc1 of the capacitor C1 increases. However, in the present invention, when the voltage Vc2 of the capacitor C2 decreases, the output voltage Vo2 of the DC-DC converter 3 decreases. Furthermore, since the voltage of the capacitor C1 increases, the output voltage Vo1 of the DC-DC converter 2 is increased. For this reason, the voltage Vc1 of the capacitor C1 and the voltage of the capacitor C2 are balanced. At this time, the voltage values of the output voltage Vo1 and the output voltage Vo2 change, but the voltage Vo is not changed because the voltage Vo obtained by adding the output voltage Vo1 and the output voltage Vo2 is supplied to the load.
Since it operates as described above, the voltage Vc1 of the capacitor C1 and the voltage of the capacitor C2 are balanced and the output voltage can be stabilized.

FIG. 2 shows a block diagram of Embodiment 2 of the present invention. The present invention will be described with reference to FIG.
The difference from the first embodiment is that the output current detection circuit 8 is provided in the DC-DC converter 4. The output current detection circuit 8 detects the output current of the DC-DC converter 4 and outputs it to the control circuit 5. The control circuit 5 generates a PWM signal according to the current signal from the output current detection circuit 8, the difference Vdef2, and the output voltage Vo2, and controls the switching element Q2 of the DC-DC converter 3 to be turned on / off. That is, the DC-DC converter 3 reduces the output voltage Vo2 when the voltage Vc2 of the capacitor C2 decreases, and decreases the output voltage Vo2 of the DC-DC converter 3 when the output current of the DC-DC converter 4 increases. For this reason, since the discharge current of the capacitor C2 can be reduced by the current output from the DC-DC converter, it is easy to balance the voltage Vc1 of the capacitor C1 and the voltage Vc2 of the capacitor C2.

  Ideal for multi-output power supplies used in facilities where high voltage is distributed.

DESCRIPTION OF SYMBOLS 1 DC power supply 2, 3, 4 DC-DC converter 5 Control circuit 6 Average value detection circuit 7 Difference generation circuit 8 Current detection circuit T1, T2, T3 Transformer Q1, Q2, Q3 Switching element D1, D2, D3 Diode C1, C2 , C4, C5, C6 capacitors

Claims (2)

A multi-output switching power supply device that supplies a plurality of DC voltages to a load,
A first DC-DC converter for outputting a first DC voltage and a second DC voltage for outputting a second DC voltage are connected to a DC power source in series with the DC power source and an output is connected in series to the load. A DC-DC converter;
A third DC-DC converter having an input connected in parallel to the input of the second DC-DC converter and supplying a third DC voltage to the load;
An average value detection unit for detecting an input voltage of the first converter and an input voltage of the second or third DC-DC converter and outputting an average value;
The first DC-DC converter is controlled in accordance with the difference between the input voltage of the first converter and the average value and the first DC voltage, and the input of the second or third DC-DC converter The second DC-DC converter is controlled according to the difference between the voltage and the average value and the second DC voltage, and the third DC-DC converter is controlled according to the third DC voltage. A control circuit;
A multi-output switching power supply device comprising:   2. The multi-output switching power supply device according to claim 1, wherein the control circuit controls each DC-DC converter so that a discharge current of a capacitor connected to an input of each DC-DC converter becomes the same. 3. .

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