JP2001286143A - Power-source unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To exactly protect a power-source unit from an overvoltage only when the power-source unit is in an abnormal state of an overvoltage. SOLUTION: A plurality of power-source units A1, A2 is connected in parallel to a load 9. A state of an overvoltage of one power-source unit A1 is determined thus by observing a state that an output current Io2 of the power-source unit A2 drops lower than the average of output currents Io1, Io2 of all power-source units A1, A2 in a current circuit 31 of the unit. Based on the result of the determination, only the abnormal power-source unit A1 is exactly protected from an overvoltage if a specified value A2 (OVP) by which an overvoltage protection operates is raised higher than a specified value A1 (OVP) by use of a set-value variable circuit 54.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device in which a plurality of power supply units operate in parallel.

[0002]

Generally, in a power supply device that requires high reliability, (N + 1) power supply units are connected in parallel to a load corresponding to N power supply units. Even when one power supply unit fails, parallel redundant operation is performed in which the remaining N power supply units supply the output current and keep the function.

FIG. 3 shows a schematic configuration of a conventional power supply unit. In FIG. 3, focusing on one power supply unit A1, + Vi and -Vi denote input terminals to which a DC input voltage Vin is supplied, and 1 denotes a switching terminal. The DC input voltage Vin is intermittently applied to the primary winding 3A of the transformer 3 by switching the switching element 2 with an inverter composed of the element 2 and the transformer 3, and the secondary winding 3B
More voltage is induced. This voltage is rectified and smoothed by diodes 5 and 6 constituting a rectifying and smoothing circuit, a choke coil 7 and a smoothing capacitor 8, and a DC output voltage Vout1 (another power supply unit) is applied between output terminals + Vo and -Vo for connecting a load 9. In A2 and A3, they are output as Vout2 and Vout3).

On the other hand, as an output voltage stabilization control detection circuit 10 for stabilizing the DC output voltage Vout1, an output voltage detection circuit 11 for detecting a change in the DC output voltage Vout1 is used.
A voltage control amplifier 13 for comparing a voltage detection signal of the voltage detection circuit 11 with a reference voltage VREF1 supplied to the other input terminal by the reference power supply 12; and a comparison result of the voltage control amplifier 13, the switching element 2 and a pulse width control circuit 14 for controlling the pulse conduction width. Among them, the output voltage detection circuit 11 has sensing terminals + S, -S for detecting a voltage between both ends of the load 9 and a voltage dividing terminal between the sensing terminals + S, -S. The resistors 15 and 16 are connected, and a voltage detection signal is supplied to one input terminal of the voltage control amplifier 13 from the connection point of the resistors 15 and 16. In particular, the output terminals + Vo,
If the voltage drop of the wire from −Vo to the load 9 cannot be ignored, if the sensing terminals + S and −S are connected between both ends of the load 9, the output voltage detection circuit 11 depends on the voltage between both ends of the load 9. The voltage detection signal can be output to the voltage control amplifier 13. When the DC output voltage Vout1 rises and the voltage level of the voltage detection signal from the output voltage detection circuit 11 rises, the voltage level of the output terminal of the voltage control amplifier 13 rises, so that the pulse width control circuit 14 The pulse conduction width of the switching element 2 is reduced, and the DC output voltage V
lower out1. Conversely, when the DC output voltage Vout1 decreases and the voltage level of the voltage detection signal from the output voltage detection circuit 11 decreases, the voltage level of the output terminal of the voltage control amplifier 13 decreases, so that the pulse width control circuit 14 The pulse conduction width of the switching element 2 is increased, and the DC output voltage V
raise out1.

Further, the output voltage stabilization control detection circuit 10
In addition, the output current of each of the power supply units A1 to A3 during the parallel operation in which the respective output terminals + Vo, -Vo of the plurality of independent power supply units A1 to A3 are connected in parallel to the common load 9 A current sharing circuit 21 for equally sharing Io1 to Io3 is provided. The current sharing circuit 21 amplifies a voltage generated between both ends of the current detection resistor 22 as a current detector inserted into the output voltage line 7 on the minus side and the output current Io1. Amplification amplifier that outputs detection signal of ~ Io3
23, the output current Io1 of the own power supply unit A1, and the output current Io of all the power supply units A1 to A3 operating in parallel.
Current balance control amplifier that compares the average value of 1 to Io3
24, and the output current Io1 of all power supply units A1 to A3 is determined based on the comparison result of the current balance control amplifier 24.
ＩIo3 are equalized by using the voltage control amplifier 13 and the pulse width control circuit 14,
The pulse conduction width of the switching element 2 is controlled for each of 1 to A3. In particular, the output terminal of the voltage amplifier 23 is
Is connected to one input terminal of a current balance control amplifier 24 via a resistor 26, and is connected to a current sharing terminal PC via a resistor 26. A connection point between the resistor 26 and the current sharing terminal PC is 24 and connected to the other input terminal of each power supply unit A1-
The current sharing terminals P of the power supply units A1 to A3 so that the average values of the output currents Io1 to Io3 of A3 can be monitored with each other.
C are connected to each other. A series circuit consisting of a diode 27 and voltage dividing resistors 28 and 29 is connected between the output terminal of the current balance control amplifier 24 and the reference power supply 12, and the connection point of the resistors 28 and 29 is connected to the voltage control amplifier. 13, the reference voltage REF1 applied to the other input terminal of the voltage control amplifier 13 fluctuates according to the comparison result of the current balance control amplifier 24, and the power supply unit A1 Output current Io1 is equal to all power supply units A1
If the output currents Io1 to Io3 are larger than the average value of the output currents Io1 to Io3, the pulse width control circuit 14 narrows the pulse conduction width of the switching element 2 so that the output current Io1 decreases. When the output current Io1 is smaller than the average value of the output currents Io1 to Io3 of all the power supply units A1 to A3, the pulse width control circuit 14 widens the pulse conduction width of the switching element 2 so that the output current Io1 increases. , The output current I of all power supply units A1 to A3
o1 to Io3 are equally shared.

Reference numeral 31 denotes an overvoltage protection circuit for protecting the load 9 when an overvoltage occurs. The overvoltage protection circuit 31 includes an overvoltage detection terminal + OVP, -OVP connected between the output terminals + Vo, -Vo, and an overvoltage detection terminal + OVP.
Voltage dividing resistors 32 and 33 connected between OVP and -OVP
And the reference voltage VREF2 from the reference power supply 34, and compares the DC output voltages Vout1 to Vou.
When t3 reaches or exceeds the set value determined by the reference voltage VREF2, the supply of the drive signal to the switching element 2 via the control terminal S / D of the pulse width control circuit 14 is cut off, and the load 9
And an overvoltage protection detection amplifier 35 that protects the circuit from overvoltage.

FIGS. 4 to 7 schematically show the configuration of the power supply apparatus shown in FIG. 3 particularly relating to the output voltage stabilization control detection circuit 10 and the overvoltage protection circuit 31. FIG. In addition,
Here, for convenience of explanation, two power supply units A1, A2
, And the voltage drop of the output voltage line is ignored.

FIG. 4 shows a configuration in which both output terminals + Vo, -Vo and overvoltage detection terminals + OVP, -OVP are directly connected to a load. The overvoltage protection set value (the level of the load voltage Vout at which the overvoltage protection operates) of each of the power supply units A1 and A2 differs depending on the characteristic variation of each of the power supply units A1 and A2. Assuming that the overvoltage protection set value A1 (OVP) of the power supply unit A1 is higher than the overvoltage protection set value A2 (OVP) of the power supply unit A2 as shown in FIG. 8, the power supply unit A1 fails at time t1. When an overvoltage condition occurs, the DC output voltage Vout1 and thus the load voltage Vout across the load 9 and the DC output voltage Vout2
Rises. At this time, the overvoltage protection set value A2 (OVP) of the normal power supply unit A2 is lower than the overvoltage protection set value A1 (OVP) of the power supply unit A1 in which the abnormality has occurred. The overvoltage protection is activated, and the output voltage Vout1 from the power supply unit A2 is
Supply is interrupted, and then at time t3, the power supply unit A
The overvoltage protection of 1 operates to cut off the supply of the output voltage Vout2 from the power supply unit A1. Therefore, in this case, the supply of the output voltage Vout is cut off in the entire power supply device, and the redundancy is lost.

On the other hand, in a line common to one of the output terminals + Vo and the overvoltage detection terminal + OVP of each of the power supply units A1 and A2, an OR diode is provided between the connection points of the power supply units A1 and A2.
41 (see FIG. 5), and each power supply unit A1, A2
In the case where the OR diode 41 is provided between one output terminal + Vo and the line connected to the overvoltage detection terminals + OVP of the same power supply units A1 and A2 (see FIG. 6), the power supply unit A1 fails. Occurs, the overvoltage protection circuit 31 of the power supply unit A2 of the other device is not affected by the overvoltage of the power supply unit A1 due to the OR diode 41. However, each of the power supply units A1 and A2 controls the current balance by the built-in current sharing circuit 21, and the normal power supply unit A2
Output voltage Vout2 rises in order to balance the output currents Io1 and Io2 between the power supply units A1 and A2. For this reason, in some cases, the normal power supply unit A2 performs the overvoltage protection operation earlier than the abnormal power supply unit A1, and the supply of the output voltage Vout is cut off in the entire power supply device.
Redundancy may be lost. Further, in each of the power supply units A1 and A2, when the voltage drop of the OR diode 41 changes, the load voltage Vout at which the overvoltage protection circuit 31 operates is changed.
There is also a problem that the level of the change.

Further, as shown in FIG. 7, in each of the power supply units A1 and A2, the OR is connected between the overvoltage detection terminal + OVP and the line connected to one output terminal + Vo of the same power supply unit A1 and A2. Diode 41
It is also conceivable to provide However, in this case, the power supply unit A1 fails and enters an overvoltage state, and the load 9
When the load voltage Vout between both ends increases, the overvoltage protection of the normal power supply unit A2 operates first, and then the overvoltage protection of the abnormal power supply unit A1 operates. Output voltage V
out supply is cut off, and redundancy is lost.

As described above, in the conventional power supply device, when a plurality of power supply units A1 and A2 are operated in parallel, not only the overvoltage protection of the abnormal power supply unit A1 in the overvoltage state does not always operate, but the normal operation. There is a case where the overvoltage protection of the power supply unit A2 is activated first, and in this case, there is a problem that the entire power supply unit goes down and the redundancy is lost.

Therefore, the present invention solves the above problems,
It is an object of the present invention to provide a power supply device capable of reliably performing an overvoltage protection operation only on an abnormal power supply unit in an overvoltage state.

[0013]

According to a first aspect of the present invention, there is provided a power supply device comprising: a plurality of power supply units connected in parallel to a load;
By comparing the output current of its own power supply unit with the average value of the output currents of all the power supply units, a current sharing circuit that evenly shares the output current of each power supply unit and a change in output voltage are detected. An output voltage stabilization control detection circuit that compares a voltage detection signal with a reference voltage to stabilize the output voltage, and an overvoltage protection circuit that cuts off the supply of the output voltage when the output voltage reaches a set value or more. In the power supply device, when the output current of the power supply unit of its own becomes lower than the average value of the output currents of all the power supply units by the current sharing circuit, a set value variable circuit that increases the set value of the overvoltage protection circuit It has.

According to the first aspect of the present invention, the current sharing circuit originally provided for equally sharing the output current of each power supply unit is provided with means for monitoring whether or not another power supply unit is in an overvoltage state. Used as That is, during a parallel operation in which a plurality of power supply units are connected in parallel to a load, if a certain power supply unit fails and enters an overvoltage state, the output voltage of the failed power supply unit increases and the output current increases. At this time, the current sharing circuit of the normal power supply unit detects that the output current of its own power supply unit is smaller than the average value of the output currents of all the power supply units, and outputs the output of its own power supply unit. Current balance control is performed so that a large amount of current flows. In other words, the overvoltage state of the other power supply units can be determined by the output current of the power supply unit of the own device being lower than the average value of the output currents of all the power supply units in the current sharing circuit. If the set value at which protection operates is raised by the set value variable circuit, even if the other power supply unit is in overvoltage status, the normal power supply unit will not operate overvoltage protection and the abnormal power supply unit will be in overvoltage status , And the redundant operation can be continued with the remaining power supply unit.

The power supply according to claim 2 of the present invention is characterized by claim 1
In addition to the configuration, from the time when the output current of the power supply unit of its own device is lower than the average value of the output currents of all the power supply units outside the upper limit range of the parallel operation in each of the normal power supply units, The set value variable circuit is configured to increase a set value of the overvoltage protection circuit.

With this configuration, even when the output current decreases during the parallel operation of each of the normal power supply units, the set value of the overvoltage protection circuit does not fluctuate and the other power supply unit becomes overvoltage. Only in this case, the set value of the overvoltage protection circuit can be effectively increased.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the power supply device according to the present invention will be described below with reference to the accompanying drawings. The same parts as those in the conventional example are denoted by the same reference numerals, and the description of the common parts will be omitted because they are duplicated. In FIG. 1 showing the overall configuration of the power supply device, in this embodiment, the anode of a diode 51 is connected to the output terminal of the current balance control amplifier 24,
The voltage dividing resistors 52 and 53 are connected between the cathode of the diode 51 and the reference power supply 34, and the connection point of the resistors 52 and 53 is connected to the other input terminal of the overvoltage protection detection amplifier 35. You. That is, as an example, the power supply unit A1
When the current sharing circuit 21 considers the output current Io1 of the own power supply unit A1 and the average value of the output currents Io1 to Io3 of all the power supply units, the power supply unit A2 Alternatively, if it is determined that A3 has caused an overvoltage condition, the overvoltage protection circuit 31
The set value variable circuit 54 for increasing the set value of
51 and resistors 52 and 53 are added. The other configuration is the same as the conventional example in FIG.

Next, the operation of the above configuration will be described with reference to the waveform diagram of FIG. Hereinafter, it is assumed that two power supply units A1 and A2 are operated in parallel for convenience of explanation. In FIG. 2, A1 (OVP)
Is the overvoltage protection set value of the power supply unit A1, A2 (OVP)
Is the overvoltage protection set value of the power supply unit A2, Vout1 is the DC output voltage of the power supply unit A1, and Vout2 is the power supply unit A
2, DC1 indicates the output terminal voltage of the current balance control amplifier 24 of the power supply unit A1 (see FIG. 1), and VA2 indicates the output terminal voltage of the current balance control amplifier 24 of the power supply unit A2. The overvoltage protection set values A1 (OVP) and A2 (OVP) of the power supply units A1 and A2 differ depending on the characteristic variations of the individual power supply units A1 and A2, and here, as shown in FIG. The overvoltage protection set value A1 (OVP) of the unit A1 is lower than the overvoltage protection set value A2 (OVP) of the power supply unit A2.

When the power supply unit A1 fails and enters an overvoltage state, the DC output voltage Vout1 and, consequently, the load voltage Vout between both ends of the load 9 increase (), and the output current Io1 of the failed power supply unit A1 increases. The output current Io2 of the normal power supply unit A2 decreases.
(). At this time, in the power supply unit A2, since the output current Io2 of the power supply unit A2 of the own device is smaller than the average value of the output currents Io1 and Io2 of all the power supply units A1 and A2, the power supply unit A2 is applied via the resistor 25. The voltage level of one input terminal of the current balance control amplifier 24 is lower than the voltage level of the other input terminal of the current balance control amplifier 24 applied via the current sharing terminal PC, and the current balance control amplifier 24 Output terminal voltage VA2 rises. Conversely, the power supply unit A1 is configured such that the voltage level of one input terminal of the current balance control amplifier 24 applied via the resistor 25 is changed to the other input terminal of the current balance control amplifier 24 applied via the current sharing terminal PC. , And the output terminal voltage VA2 of the current balance control amplifier 24 drops rapidly (). Thus, the power supply unit A
2. The pulse width control circuit 14 switches the switching element so that the reference voltage VREF1 applied to the other input terminal of the voltage control amplifier 13 increases by the current balance control by the current sharing circuit 21 and the output current Io1 increases. 2, the pulse conduction width is increased. As a result, the DC output voltage Vout2 of the power supply unit A2 becomes the DC output voltage Vou of the power supply unit A1.
The slope rises following t1 ().

Thereafter, in the normal power supply unit A2, the output terminal voltage VA2 of the current balance control amplifier 24 is further increased by the power supply unit A1 in the overvoltage state.
Then, when the rise of the output terminal voltage VA2 deviates from the upper limit range during the parallel operation in the normal power supply units A1 and A2, the diode 51 becomes conductive and the other input terminal of the overvoltage protection detection amplifier 35 is connected to the diode 51. The applied reference voltage VREF2 starts to rise, and from this, the set value A2 (OVP) of the DC output voltage Vout2 at which the overvoltage protection operates is increased in proportion to the output terminal voltage VA2 (). The set value A2 (OVP) of the power supply unit A2 exceeds the set value A1 (OVP) of the power supply unit A1 as the output terminal voltage VA2 of the current balance control amplifier 24 increases.

On the other hand, in the failed power supply unit A1, as the DC output voltage Vout1 increases, the detection voltage applied to one input terminal of the overvoltage protection detection amplifier 35 becomes the reference voltage VREF2 applied to the other input terminal. (The reference voltage VREF2 here is the output terminal voltage V of the current balance control amplifier 24.
When A2 drops and the diode 51 is in a non-conducting state and hardly changes, that is, when the DC output voltage Vout1 reaches the set value A1 (OVP) or more, the control of the pulse width control circuit 14 is performed. The supply of the drive signal to the switching element 2 via the terminal S / D is interrupted (). At this moment, the failed power supply unit A1 is disconnected from the other power supply unit A2, and the overvoltage state for the load 9 is released. The DC output voltage Vout1 of the power supply unit A1 is sloped down and finally becomes 0V. At the same time, the DC output voltage Vout1 of the power supply unit A2 also decreases with a slope, and the set value A
2 (OVP) also returns to the original state, but in this series of operations, the normal power supply unit A2 does not operate the overvoltage protection, and thereafter supplies the predetermined output voltage Vout2 to the load 9 to continue the operation ( ).

As described above, in this embodiment, a plurality of power supply units A1 and A2 are connected in parallel to the load 9, and each of the power supply units A1 and A2 is connected to the output current Io2 of its own power supply unit A2 and all the power supplies. By comparing the average value of the output currents Io1 and Io2 of the units A1 and A2, the current sharing circuit 21 equally shares the output currents Io1 and Io2 of the power supply units A1 and A2, and the DC output voltage Vout1 as the output voltage. , Vout2, and compares this voltage detection signal with a reference voltage VREF2 to determine the DC output voltages Vout1, Vou.
The output voltage stabilization control detection circuit 10 for stabilizing t2 and the DC output voltages Vout1 and Vout2 are set to A1 (OVP) and A2
(OVP) or more, DC output voltage Vout1, Vout2
In the power supply device provided with the overvoltage protection circuit 31 for interrupting the supply of power, all the power supply units A
When the output current Io2 of the power supply unit A2 of the own device becomes lower than the average value of the output currents Io1 and Io2 of the own device A2, the set value variable circuit 54 for increasing the set value A2 (OVP) of the overvoltage protection circuit 31 of the own device. It has.

Here, each power supply unit A1, A2
It is characterized in that a current sharing circuit 21 provided to equally share the output currents Io1 and Io2 is used as means for monitoring whether or not another power supply unit A1 is in an overvoltage state. That is, in a parallel operation in which a plurality of power supply units A1 and A2 are connected in parallel to the load 9, when a certain power supply unit A1 fails and enters an overvoltage state, the DC output voltage Vou of the failed power supply unit A1
As t1 increases, the output current Io1 increases. At this time,
The current sharing circuit 21 of the normal power supply unit A2 detects that the output current Io2 of its own power supply unit A2 is smaller than the average value of the output currents Io1 and Io2 of all the power supply units A1 and A2, Current balance control is performed so that a large output current of the power supply unit A2 of the own device flows. That is, in the overvoltage state of the other power supply unit A1, the output current Io2 of the power supply unit A2 of the own device is lower than the average value of the output currents Io1 and Io2 of all the power supply units A1 and A2 in the current sharing circuit 31 of the own device. The set value A2 (OVP) at which the overvoltage protection is activated is set by the set value variable circuit 54 to the set value A1 (O
VP), if the other power supply unit A1 is in an overvoltage state, the normal power supply unit A2 does not operate the overvoltage protection, and only the abnormal power supply unit A1 in the overvoltage state is reliably assured. By performing the overvoltage protection operation, the remaining power supply unit A2 can continue the redundant operation.

In the circuit of FIG. 6 shown in the conventional example, in the current balance function, the output side of the current balance control amplifier 24 is controlled so as not to raise the DC output voltage Vout2 to the set value A2 (OVP) at which the overvoltage protection operates. Although it is conceivable to provide a limiting circuit for the power supply unit (see FIG. 93), since the normal power supply unit A2 is stopped by the voltage control, the recovery after the failed power supply unit A1 is stopped by the overvoltage protection is delayed. In this regard, in the present embodiment, when the failed power supply unit A1 stops due to overvoltage protection, the normal power supply unit A2 is operating, and the remaining power supply units A1
2 enables quick voltage recovery.

In this embodiment, all the power supply units A
From the point in time when the output current Io2 of the power supply unit A2 of its own device falls below the average upper limit of the parallel operation in the normal power supply units A1 and A2 with respect to the average value of the output currents Io1 and Io2 of A1 and A2. , Set value A of the overvoltage protection circuit 31
The set value variable circuit 54 is configured to increase 1 (OVP) and A2 (OVP).

In this manner, the output current Io2 of the own power unit during the parallel operation in each of the normal power supply units A1 and A2.
Even if the power supply unit A1 is in an overvoltage state, the set value of the overvoltage protection circuit 31 of the own device is effectively changed only when the other power supply unit A1 is in an overvoltage state.
2 (OVP) can be increased.

Further, the set value variable circuit 54 in the present embodiment.
Is a resistor that divides a comparison value between the output current Io2 of its own power supply unit A2 and the average value of the output currents Io1 and Io2 of all the power supply units A1 and A2, and adds it to the reference voltage VREF2 of the overvoltage protection circuit 31. A series circuit of 52 and 53 and a diode 51 which becomes conductive when the comparison value falls below the upper limit range of the ordinary power supply units A1 and A2 during parallel operation becomes low.

As described above, the set value variable circuit 54 is composed of the series circuit of the voltage dividing resistors 52 and 53 and the diode 51, and only by adding a simple configuration, it is possible to remove only the abnormal power supply unit which has become in the overvoltage state. The overvoltage protection operation can be reliably performed.

The set value A1 (OVP), at which the overvoltage protection is activated by lowering the voltage of the load 9 such as an LSI, for example.
The margin of A2 (OVP) is reduced. In this case, the power supply units A1 and A2 are connected as shown in FIG.
The voltage on the cathode side (the load 9 side) of the OR diode 41 may be monitored to activate the overvoltage protection.

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the present invention.

[0031]

According to the power supply device of the present invention, a plurality of power supply units are connected in parallel to a load, and each power supply unit has an output current of its own power supply unit and an output current of all power supply units. A current sharing circuit that evenly shares the output current of each power supply unit by comparing with an average value, detects a change in output voltage, and compares this voltage detection signal with a reference voltage to stabilize the output voltage. And an overvoltage protection circuit that shuts off the supply of the output voltage when the output voltage reaches or exceeds a set value, wherein all of the power supply units are controlled by the current sharing circuit. When the output current of the power supply unit of the own device becomes lower than the average value of the output current, a set value variable circuit for increasing the set value of the overvoltage protection circuit is provided. Only abnormal power units can provide a possible power supply reliably be overvoltage protection operation.

The power supply according to claim 2 of the present invention is based on claim 1
In addition to the configuration described in the above, the output current of the power supply unit of its own became lower than the average value of the output currents of all the power supply units, deviating from the upper limit range at the time of parallel operation in each normal power supply unit. From the time point, the set value variable circuit is configured to increase the set value of the overvoltage protection circuit, and only when another power supply unit is in an overvoltage state, the set value of the overvoltage protection circuit is effectively changed. Can be raised.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of an entire power supply device according to an embodiment of the present invention.

FIG. 2 is a waveform chart showing the operation of each unit of the above.

FIG. 3 is a circuit diagram showing a configuration of an entire power supply device showing a conventional example.

FIG. 4 is a schematic circuit diagram showing a conventional example, particularly showing a connection state of a power supply unit.

FIG. 5 is a schematic circuit diagram showing a conventional example, particularly showing another connection state of a power supply unit.

FIG. 6 is a schematic circuit diagram showing a conventional example, particularly showing still another connection state of a power supply unit.

FIG. 7 is a schematic circuit diagram showing a conventional example, particularly showing still another connection state of a power supply unit.

FIG. 8 is a waveform diagram showing the operation of each section showing a conventional example.

FIG. 9 is a waveform diagram showing the operation of each section showing a conventional example.

[Explanation of symbols]

 A1 to A3 power supply unit 9 load 10 output voltage stabilization control detection circuit 21 current sharing circuit 31 overvoltage protection circuit 54 set value variable circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5G065 BA01 DA01 DA07 EA01 HA04 HA07 JA01 LA01 LA02 MA09 MA10 5H730 AA20 AS01 BB23 BB57 BB84 FD01 FD31 FG05 XX04 XX12 XX23 XX32

Claims (2)

[Claims] A plurality of power supply units are connected in parallel to a load, and each power supply unit compares the output current of its own power supply unit with the average value of the output currents of all power supply units to determine whether each power supply unit has an output current. A current sharing circuit that evenly shares the output current, and an output voltage stabilization control detection circuit that detects fluctuations in the output voltage, compares this voltage detection signal with a reference voltage, and stabilizes the output voltage, When the output voltage reaches or exceeds a set value, in a power supply device provided with an overvoltage protection circuit that cuts off the supply of the output voltage, the current sharing circuit uses the power supply of its own device with respect to the average value of the output currents of all power supply units. When the output current of the unit decreases,
A power supply device comprising a set value variable circuit for increasing a set value of the overvoltage protection circuit. 2. From the point in time when the output current of the power supply unit of its own device falls below the upper limit range of the ordinary parallel operation in each power supply unit with respect to the average value of the output currents of all power supply units, The power supply device according to claim 1, wherein the set value variable circuit is configured to increase a set value of the overvoltage protection circuit.