JP3388216B2 - Power supply for current balanced parallel power supply system - Google Patents

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 for a current-balanced parallel power supply system, which is suitable for use in parallel operation by connecting a plurality of power supply devices to a common load.
In particular, it relates to a technical improvement for suppressing inappropriate operation of the current balance mechanism.

[0002]

2. Description of the Related Art Japanese Utility Model Registration No. 2571942 discloses the following configurations of a power supply device for a current-balanced parallel power supply system. A switching power supply circuit for converting an input power supply into a predetermined DC power supply and outputting the same to the common load, and a voltage control means for controlling the switching power supply circuit so as to keep the output voltage of the circuit at a predetermined value. A current comparison bus connection terminal is provided, and this terminal is connected to the same current comparison bus connection terminal of another power supply device operated in parallel by the current comparison bus. Output current detection means for detecting a current value output to the common load, voltage superposition means for superposing the output voltage of the output current detection means on the voltage on the current comparison bus, and via the voltage superposition means. The output voltage of the output current detection means and a current deviation detection means for detecting a deviation between the voltages on the current comparison bus, and the output of the current deviation detection means is applied to the voltage control means to eliminate the deviation. Thus, the output voltage of the switching power supply circuit is controlled. A cutoff circuit is provided for disconnecting the voltage superposition circuit from the current comparison bus connection terminal. A means for switching the cutoff circuit from the conductive state to the cutoff state immediately when the inside of the power supply device abnormally operates is provided.

With the above configuration, when an internal abnormality occurs in a certain power supply device while a plurality of power supply devices are interconnected by the current comparison bus and are operating in parallel, In the power supply device, the cutoff circuit is immediately switched to the cutoff state and disconnected from the current comparison bus. Therefore, it is possible to prevent mischief in which the abnormal power supply device adversely affects another normal power supply device via the current balance mechanism and the voltage applied to the load fluctuates inappropriately.

[0004]

According to the research conducted by the present inventors, the current balancing mechanism for interconnecting a plurality of power supply units by the current comparison bus is one power supply unit operating in parallel as described above. Not only when the device malfunctions,
It has been found that even in the following situations, it causes inappropriate behavior.

For example, three power supply units A, B, and C are interconnected by a current comparison bus, and two of them are A and B.
Is operating to supply electric power to the common load, and the other power supply device C is out of operation. Then, for the purpose of increasing the power supply amount, the power supply device C that has been stopped is also operated, and the power supply switch of the device C is turned on. At this time, it takes a considerable amount of time for the output of the switching power supply circuit of the power supply device C to rise to the specified voltage so that the regular output can be applied to the common load.
On the other hand, the operational amplifier and the logic circuit of the control circuit system of the power supply device C start up in a very short time and start to function normally, and the current balance mechanism (the above-mentioned voltage control means, output current detection means, voltage superposition means, Current deviation detection means, etc.) also function as planned. Therefore, in this situation, since the output of the power supply device C has not reached the specified voltage, no current is supplied from the device C to the common load, and conversely, from the devices A and B to the output smoothing capacitor in the device C. In some cases, current may flow in. The current balance mechanism of the device C responds to this situation and exerts a strong control action so as to increase the output voltage of the device C. Then, the output voltage of the device C increases with time and finally reaches the specified voltage, but the output voltage of the device C exceeds the specified voltage due to the strong control action for increasing the voltage. In other words, it causes overshoot, and the whole parallel power supply system becomes unstable for a while. Also, when the power switch of one device C is turned off during parallel operation, immediately immobilizing the current balance mechanism of the device C again makes the system unstable and causes undershoot of the load voltage.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to cause an improper operation of a current balance mechanism when the power supply device included in the system is turned on and off. To prevent.

[0007]

SUMMARY OF THE INVENTION The present invention is a power supply device for a current-balanced parallel power supply system, which is suitable for use in which a plurality of power supply devices are connected in parallel to a common load and operated. It is provided with a switching power supply circuit for converting to a predetermined DC power supply and outputting to the common load, and a voltage control means for controlling the switching power supply circuit so as to keep the output voltage of this circuit at a predetermined value. Further, a current comparison bus connection terminal is provided, and this terminal is connected to the same current comparison bus connection terminal of another power supply device operated in parallel by the current comparison bus. Also, output current detection means for detecting a current value output to the common load, voltage superposition means for superposing the output voltage of the output current detection means on the voltage on the current comparison bus, and the voltage superposition means. A current deviation detection means for detecting a deviation between the output voltage of the output current detection means and the voltage on the current comparison bus via the output current detection means. The output of the current deviation detection means acts on the voltage control means to cause the deviation. The output voltage of the switching power supply circuit is controlled to eliminate the above. Further, a cutoff circuit for disconnecting the voltage superposition circuit from the current comparison bus connection terminal is provided. Further, it is provided with means for detecting whether or not the input power source is being applied, and means for changing the shutoff circuit from the shutoff state to the conductive state with an appropriate delay when the input power source is applied. Further, means for detecting whether or not the output voltage of the switching power supply circuit exceeds a reference value, and making the cutoff circuit conductive when the output voltage exceeds the reference value and the output voltage being the reference value. Means is provided for turning off the shutoff circuit when the value is less than a value.

In the power supply device having the above configuration, it is desirable that the cutoff state and the conduction state are switched by gradually changing the resistance value of the cutoff circuit.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the embodiment shown in FIG. 1, two power supply devices 1 having the same structure are connected to a common load 16. In the power supply device 1, when the power switch 3 is turned on, the switching power supply circuit 4 operates to convert the commercial AC power supply 2 into a predetermined DC power supply and apply it to the load 16 connected to the output terminal 5. The switching power supply circuit 4 has a well-known configuration in which a switching operation is controlled by a PWM (pulse width modulation) control circuit 8 and an output voltage is changed. The output voltage of the switching power supply circuit 4 is detected by the circuit 7, the detection signal is input to the PWM control circuit 8, and the PWM control circuit 8 feedback-controls the power supply circuit 4 so as to keep the output voltage of the power supply circuit 4 at a predetermined value. To do.

The output current detection circuit 9 generates a voltage signal corresponding to the value of the current flowing from the switching power supply circuit 4 to the load 16. The output of this detection circuit 9 is the resistance 10 and the FET 1.
It is connected to the current comparison bus connection terminal 6 via the serial circuit 1. The resistor 10 functions as the voltage superimposing means described above, and the FET 11 functions as the interruption circuit described above. F
The ET11 is controlled to be switched between a conductive state and a cutoff state by the cutoff control circuit 13. For the time being, the FET11 is used.
Will be described as being in a completely conductive state (ON).

Terminals 6 and 6 of two power supply devices 1 having the same structure are connected by a common current comparison bus 15. Outputs of the output current detection circuit 9 are on the bus 15 via resistors 10 respectively. Are butt-matched with. If the voltage signals output by the two detection circuits 9 are not equal, the intermediate value of the voltage signals occurs on the bus 15. Then, in one power supply device 1, a voltage difference between the voltage output from the output current detection circuit 9 and the voltage on the bus 15 is generated across the resistor 10. The difference voltage is detected by the deviation detection circuit 12 and appropriately amplified, and the deviation signal output from this is input to the PWM control circuit 8. This deviation signal is calculated by comparing the current value supplied to the load 16 by the self (power supply device 1) with the average current value supplied by the fellow (other power supply device 1) to the load 16. Indicates whether the output current of is large or small. PWM control circuit 8
Controls the switching power supply circuit 4 based on the signal from the deviation detection circuit 12, appropriately raises the output voltage of the power supply circuit 4 so as to decrease it if the output current of its own is large, and increases it if it is small. The output voltage is appropriately reduced so that The above is the configuration and operation of the current balance mechanism.

Next, the main part of the present invention will be described. The input voltage detection circuit 14 is a circuit that detects when the input power supply 2 is switched off and on to the switching power supply circuit 4 via the power supply switch 3. The detection signal of the input voltage detection circuit 14 and the detection signal of the output voltage detection circuit 7 are input to the cutoff control circuit 13, and the circuit 13 operates the FET 11 as the cutoff circuit based on the two input signals as follows. To control.

(A) When it is detected that the input power supply 2 is turned on to the switching power supply circuit 4 based on the signal from the input voltage detection circuit 14, the FET 11 is turned off from the on state after a delay of an appropriately set time. Invert. (B) If it is detected that the supply of the input power supply 2 to the switching power supply circuit 4 has been interrupted based on the signal from the input voltage detection circuit 14, then F is delayed by an appropriately set time.
Invert ET11 from on to off. (C) The FET 11 is turned on when the output voltage of the switching power supply circuit 4 exceeds the reference value based on the signal from the output voltage detection circuit 7, and the FET 11 is turned off when the output voltage is less than the reference voltage. .

For example, three power supply units A, B and C are interconnected by a current comparison bus 15, and two of them are A.
And B are operating to supply power to the common load 16, and the other power supply device C is not operating. Then, for the purpose of increasing the power supply amount, the power supply device C that has been stopped is also operated, and the power switch 3 of the device C is turned on. As described above, it takes a relatively long time for the output voltage of the switching circuit 4 of the device C to rise to the specified value. In the present invention, since the FET 11 is turned on with a proper delay after the input power supply 2 is turned on, the device C has not participated in the current balance control system until then. When the output voltage of the device C is sufficiently high, the FET 11 is turned on, and the device C also participates in the current balance type control system. Similarly, device C
If the output voltage of is less than the reference value, the FET 11 is turned off and the device C is disconnected from the current balance type control system. In the above embodiment, FET1
If the conduction resistance of the FET 11 is gradually increased or decreased when inverting 1 from on to off and vice versa, the fluctuation factor given to the current balance control system is extremely small. This is desirable because it can stabilize the system.

[0015]

As described in detail above, according to the present invention, it is possible to prevent the current balance mechanism from causing an inappropriate operation when the power supply devices included in the parallel operation system are turned on and off. can do.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a power supply device for a current balanced parallel operation power supply system according to an embodiment of the present invention.

[Explanation of symbols]

1 power supply 2 Input power 3 power switch 4 Switching power supply circuit 5 output terminals 6 Current comparison bus connection terminal 7 Output voltage detection circuit 8 PWM control circuit 9 Output current detection circuit 10 Resistance (voltage superposition means) 11 FET (cutoff circuit) 12 Deviation detection circuit 13 Interruption control circuit 14 Input voltage detection circuit 15 Current comparison bus 16 load

Continuation of the front page (56) References JP-A-9-331681 (JP, A) JP-A-7-39151 (JP, A) Actual Kaihei 6-36387 (JP, U) (58) Fields investigated (Int .Cl. ⁷ , DB name) H02M 7/12 H02M 3/155

Claims (2)

(57) [Claims] 1. An invention specified by the following items (1) to (7). (1) A power supply device for a current-balanced parallel power supply system, which is suitable for the purpose of operating a plurality of power supply devices in parallel with a common load. (2) A switching power supply circuit that converts an input power supply into a predetermined direct current power supply and outputs it to the common load, and a voltage control means that controls the switching power supply circuit so that the output voltage of this circuit is maintained at a predetermined value. Equipped with. (3) A current comparison bus connection terminal is provided, and this terminal is connected to the same current comparison bus connection terminal of another power supply device operated in parallel by the current comparison bus. (4) Output current detection means for detecting a current value output to the common load, voltage superposition means for superposing the output voltage of the output current detection means on the voltage on the current comparison bus, and the voltage superposition. A current deviation detecting means for detecting a deviation between the output voltage of the output current detecting means and the voltage on the current comparison bus via the means, and the output of the current deviation detecting means is caused to act on the voltage control means. The output voltage of the switching power supply circuit is controlled so as to eliminate the deviation. (5) A cutoff circuit for disconnecting the voltage superposition circuit from the current comparison bus connection terminal is provided. (6) Means for detecting whether or not the input power source is applied, and means for changing the shutoff circuit from the shutoff state to the conductive state with a suitable delay when the input power source is applied. (7) Means for detecting whether or not the output voltage of the switching power supply circuit exceeds a reference value, and making the cutoff circuit conductive when the output voltage exceeds the reference value, and A means is provided for setting the cutoff circuit in a cutoff state when the value does not reach the reference value. 2. The power supply device according to claim 1, wherein the cutoff state and the conduction state are switched by gradually changing the resistance value of the cutoff circuit.