JP2009142028A - Parallel power supply system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a parallel power supply system which prevents harmful effects on other normal power supply units when the output voltage of a power supply unit is abnormal or the output stops. <P>SOLUTION: The parallel power supply system comprises a switching circuit 9 for converting an input AC power supply into a DC power supply, an output current detection circuit 19 for outputting a voltage signal in response to detection of an output current, an output voltage detection circuit 17, a current balance circuit 22 for superimposing the voltage signal on a voltage of a current bus 31 and detecting the difference between a power supply and other power supply from the average current value of the current bus 31 and the voltage signal, a PWM control section 21 for controlling the switching circuit 9 such that the current to a common load is balanced among a plurality of power supply units based on the difference, an FET 25 provided between a current balance terminal CB and the current balance circuit 22, and a disconnection control section 23 for disconnecting the FET 25 when a determination is made that the output voltage is abnormal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a parallel power supply system in which outputs of a plurality of power supply devices are connected in parallel to a common load, and in particular, a parallel power supply that balances output voltages by mutually connecting current balance terminals provided in a plurality of power supply devices. About the system.

  Conventionally, a plurality of power supply devices connected in parallel to a common load and current balance terminals of the plurality of power supply devices are connected, and an average current value (intermediate value) of output currents of the plurality of power supply devices is converted into a voltage. A parallel power supply system having a current bus for transmitting the signal has been proposed. In a parallel power supply system having such a configuration, in general, a voltage signal corresponding to the output current of its own device is superimposed on the voltage on the current bus, and an average current value (intermediate value) flowing in the current bus and the voltage signal are The current balance circuit detects the difference between the output voltage of the own power supply device and the output voltage of the other power supply device. And this current balance circuit makes the said difference act on a switching circuit, and balances the output voltage of each power supply device (for example, refer patent document 1).

JP 2004-166437 A

  However, according to the above-described conventional current balance control, when a malfunction occurs in one of the plurality of power supply devices, for example, the output voltage becomes abnormal or the output is stopped, the operation of the current balance circuit Becomes unstable and disturbs the average current value (intermediate value) flowing through the current bus, causing the output voltage of other normal power supply devices to fluctuate inappropriately. Specifically, for example, when any one of the power supply devices fails, the average current value flowing through the current bus decreases, so that the other power supply devices decrease the output voltage in an attempt to balance. That is, according to the conventional current balance control, for example, when any one power supply device fails, the current balance circuit of the failed power supply device may adversely affect the operation of other normal power supply devices. Improvement was desired.

  The present invention has been made in view of the above, and when any one of the plurality of power supply devices has an output voltage abnormality or output stop, the current balance circuit has another normal power supply. It is an object of the present invention to provide a parallel power supply system that can maintain stable normal operation without adversely affecting the operation of the apparatus.

  In order to solve the above-described problems and achieve the object, a parallel power supply system of the present invention connects a plurality of power supply devices connected in parallel to a common load and current balance terminals of the plurality of power supply devices to each other. And a current bus that transmits the average current value of the output currents of the plurality of power supply devices by voltage, and the power supply device converts the input AC power source to a predetermined DC power source and outputs it to a common load. Output current detection means for detecting an output current output toward the common load and outputting a voltage signal corresponding to the output current; output voltage detection means for detecting an output voltage output toward the common load And the voltage signal output from the output current detection means is superimposed on the voltage on the current bus, and from the average current value flowing through the current bus and the voltage signal detected by the output current detection means, A current balance circuit that detects the difference between the output voltage and the output voltage of another power supply device, and a switching circuit control unit that controls the switching circuit so that the current flowing through the common load is balanced among the plurality of power supply devices based on this difference The output voltage control unit having the above, the disconnection circuit provided between the current balance terminal and the current balance circuit, and the output voltage detected by the output voltage detection means are monitored, and it is determined that the output voltage is abnormal. And a cutting control unit for cutting the cutting circuit.

  According to the present invention, the disconnection circuit is provided between the current balance terminal and the current balance circuit, and the disconnection control unit for operating the disconnection circuit is further provided. The disconnection control unit monitors the output voltage output from the own power supply device. However, since the disconnect circuit is disconnected when it is determined that there is an abnormality in the output voltage, the current balance is maintained even when one of the multiple power supply units has an abnormal output voltage or the output is stopped. There is an effect that the circuit is disconnected from the current bus and the current balance circuit does not adversely affect the operation of other normal power supply devices.

  Embodiments of a parallel power supply system according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a schematic functional block diagram of Embodiment 1 of a parallel power supply system according to the present invention. In FIG. 1, a parallel power supply system 100 according to the present embodiment includes three power supply devices: a first power supply device 50A, a second power supply device 50B, and a third power supply device 50C. The output terminals of the three power supply devices 50A, 50B, and 50C are connected to the load 60 in parallel. In addition, the current balance terminals CB of the three power supply devices 50A, 50B, and 50C are connected to each other by a current bus 31. The three power supply devices 50A, 50B, and 50C have the same configuration. Hereinafter, the configuration of the first power supply device 50A will be described as a representative, and the first power supply device 50A will be described as its own device, and the second power supply device 50B and the third power supply device 50C will be described as other devices.

  The first power supply device (hereinafter simply referred to as power supply device) 50 </ b> A is a switching power supply that generates a stable DC power supply from the AC commercial power supply 3 and supplies it to the load 60. That is, the power supply device 50A converts the commercial AC power supply 3 into a predetermined DC power supply and applies it to the load 60 connected to the output terminal.

  As shown in FIG. 1, an input rectifier circuit 5, an input smoothing capacitor 7, and a switching circuit 9 are provided in this order from the AC commercial power supply 3 side on the primary side of the transformer 11. On the other hand, on the secondary side of the transformer 11, an output rectifier circuit 13, an output smoothing capacitor 15, an output voltage detection circuit 17, and an output current detection circuit 19 are provided from the transformer 11 toward the load 60 side.

  The output voltage control unit 20 is provided so that the current flowing through the load 60 is balanced between the power supply devices 50A, 50B, and 50C. The output voltage control unit 20 performs PWM control unit (switching circuit control unit) 21 that performs feedback control of the switching circuit 9, and detects the difference between the output voltage of the own power supply device and the output voltage of the other power supply device to perform current balance control. And a current balance circuit 22. The feedback control of the switching circuit 9 performed by the PWM control unit 21 is a well-known technique in which the switching operation of the switching circuit 9 is controlled by PWM (Pulse Wide Modulation) and the output voltage becomes variable. The output voltage of the switching circuit 9 is detected by the output voltage detection circuit 17 (output voltage detection means), and the detection signal is input to the PWM control unit 21. The PWM control unit 21 feedback-controls the switching circuit 9 so that the current flowing through the load 60 is balanced between the power supply devices 50A, 50B, and 50C based on a detection signal from the output voltage detection circuit 17 and a deviation described later. The output voltage detected by the output voltage detection circuit 17 is also input to the cutting control unit (MPU) 23 at the same time.

  The output current detection circuit (output current detection means) 19 generates a voltage signal corresponding to the current value flowing from the switching circuit 9 to the load 60. The output of the output current detection circuit 19 is input to the current balance circuit 22. The current balance circuit 22 includes a resistor 22a and a deviation detection circuit 22b. The current balance circuit 22 outputs the voltage signal output from the output current detection circuit 19 to the current balance terminal CB via the resistor 22a. As a result, the voltage signal output from the output current detection circuit 19 is superimposed on the voltage on the current bus 31. The voltage on the current bus 31 is a voltage indicating an average current value (intermediate value) that is an average of the respective output currents based on voltage signals output from the power supply devices 50A, 50B, and 50C.

  The current balance circuit 22 also detects the difference between the output voltage of the own power supply device and the output voltage of the other power supply device from the average current value applied to the current bus 31 and the voltage signal detected by the output current detection circuit 19. Then, this difference is output to the PWM control unit 21 to act on the switching circuit 9.

  An FET 25 that functions as a cutting means is provided between the current balance circuit 22 and the current balance terminal CB. The FET 25 is switched between a conductive state (on) and a cut state (off) by the cutting control unit 23. The cutting control unit 23 is configured by an MPU (Micro Processing Unit), and is capable of making a complicated process determination based on a stored program.

  The parallel power supply system 100 performs the following operation of the parallel operation power supply. As described above, the current balance terminals CB of the three power supply devices 50A, 50B, and 50C are connected to each other by the common current bus 31. As a result, the outputs of the output current detection circuits 19 of the power supply devices 50A, 50B, and 50C are abutted on the current bus 31 via the resistors 22a, respectively, and three output current detections are detected on the current bus 31. An intermediate value of the voltage signal output from the circuit 19 is generated. A voltage difference between the voltage output from the output current detection circuit 19 and the voltage on the current bus 31 is generated at both ends of the resistor 22a. The difference voltage is detected by the deviation detection circuit 22b and appropriately amplified, and a deviation signal output from the deviation detection circuit 22b is input to the PWM control unit 21. This deviation signal is the output of the power supply device 50A in comparison between the current value that the power supply device 50A supplies to the load 60 and the average current value that the other power supply devices 50B and 50C supply to the load 60. Indicates whether the current is large or small. The PWM control unit 21 controls the switching circuit 9 based on the signal from the current balance circuit 22, and appropriately increases the output voltage of the switching circuit 9 so as to decrease if the output current of the PWM control unit 21 increases. Thus, the output voltage is appropriately reduced.

  Next, the operation of the cutting function will be described. The disconnection control unit 23 monitors the output of the output voltage detection circuit 17 and turns off the FET 25 when an abnormality occurs in the output voltage of its own device (power supply device 50A). When the output voltage output from the output voltage detection circuit 17 is equal to or higher than a predetermined threshold value, the disconnection control unit 23 turns on the FET 25 (ON) and when the output voltage is lower than the threshold value. The FET 25 is turned off (OFF). When the FET 25 is disconnected, the current balance circuit 22 is disconnected from the current bus 31, and the current balance circuit 22 does not disturb the average current signal (intermediate value) on the current bus 31. Thereby, for example, even when any one of the power supply devices fails, the output voltage of the other power supply device does not decrease.

Embodiment 2. FIG.
The cutting control unit 23 according to the second embodiment is configured by an MPU as in the first embodiment, and is capable of making a complicated process determination using a stored program. The cutting control unit 23 according to the present embodiment monitors the output voltage output from the output voltage detection circuit 17 and puts the cutting circuit into a cutting state when the output voltage decreases by a predetermined amount at a predetermined change rate. Other configurations are the same as those of the first embodiment.

  In the power supply devices 50A, 50B, and 50C, for example, when the switching circuit breaks down and the output is stopped, the output voltage gradually decreases at a predetermined rate of change. That is, in the present embodiment, this change is remembered by the disconnection control unit 23, and the FET 25 is disconnected only when the change occurs. With such a configuration, it is possible to prevent the disconnection control unit 23 from being operated by a simple voltage change that is not a failure, and a highly reliable system can be obtained. The determination by the cutting control unit 23 may be performed in combination with the threshold value according to the first embodiment.

  In the present embodiment, the FET 25 is disconnected when the output voltage gradually decreases at a predetermined rate of change. However, the FET 25 is not limited to this change mode, and any change can be made. At this time, it may be cut off.

  In the first and second embodiments, the FET is used as the disconnection circuit. However, the disconnection circuit is not limited to the FET, and may be composed of other switches.

  As described above, the parallel power supply system according to the present invention is useful for a parallel power supply system in which outputs of a plurality of power supply devices are connected in parallel to a load. In particular, current balance terminals provided in a plurality of power supply devices are interconnected. It is suitable for a parallel power supply system that balances output voltage.

1 is a schematic functional block diagram of a first embodiment of a parallel power supply system according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Commercial AC power source 5 Input rectifier circuit 7 Input smoothing capacitor 9 Switching circuit 11 Transformer 13 Output rectifier circuit 15 Output smoothing capacitor 17 Output voltage detection circuit (output voltage detection means)
19 Output current detection circuit (output current detection means)
20 Output voltage controller 21 PWM controller (switching circuit controller)
22 current balance circuit 22a resistance 22b deviation detection circuit 23 cutting control unit 25 FET (cutting circuit)
31 Current bus 50A First power supply 50B Second power supply 50C Third power supply 60 Load 100 Parallel power supply system CB Current balance terminal

Claims (3)

A plurality of power supply devices connected in parallel to a common load and current balance terminals of the plurality of power supply devices are connected to each other and an average current value of output currents of the plurality of power supply devices is transmitted as a voltage. Equipped with a bus
The power supply device
A switching circuit that converts an input AC power source into a predetermined DC power source and outputs the same toward the common load;
Output current detection means for detecting an output current output toward the common load and outputting a voltage signal corresponding to the output current;
An output voltage detecting means for detecting an output voltage output toward the common load;
The voltage signal output from the output current detection means is superimposed on the voltage on the current bus, and the output voltage of the power supply apparatus is determined from the average current value flowing through the current bus and the voltage signal detected by the output current detection means. Balance circuit for detecting the difference between the output voltage of the power supply device and the other power supply device, and switching circuit control for controlling the switching circuit based on the difference so that the current flowing through the common load is balanced among the plurality of power supply devices An output voltage control unit having a unit,
A cutting circuit provided between the current balance terminal and the current balance circuit;
A parallel power supply system comprising: a disconnect control unit that monitors the output voltage detected by the output voltage detection means and disconnects the disconnect circuit when it is determined that the output voltage is abnormal. The disconnection control unit monitors the output voltage detected by the output voltage detection unit, and when the output voltage is equal to or higher than a predetermined threshold, the disconnection circuit is turned on, and the output voltage is the threshold value. The parallel power supply system according to claim 1, wherein the disconnection circuit is in a disconnected state when the value is less than the value. The disconnection control unit monitors an output voltage detected by the output voltage detection unit, and puts the disconnection circuit into a disconnected state when the output voltage decreases by a predetermined amount at a predetermined change rate. The parallel power supply system according to 1.

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