JPH04325870A - Parallel operation current controller - Google Patents

Abstract

PURPOSE:To simultaneously conduct an optimum equilibrium regulation of output currents of a plurality of switching power sources and a regulation of overcurrent detecting characteristic for drooping an output when the plurality of power sources are operated in parallel. CONSTITUTION:A current at a primary side of a transformer in a main power source is detected by a current detector 6 to obtain a detected voltage. This voltage is mixed with an error voltage for originally controlling to stabilize, and input to a stabilizing controller 4. The detected voltage is also input to an overcurrent detector for controlling to droop an output voltage to protect against an overcurrent. An optimum value of an output current equilibrium control signal and an overcurrent control signal can be regulated at once by regulating a level of the detected voltage by a variable resistor 9. (Captions)

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a parallel operation current control device, and more particularly to control of output power supply current when a plurality of switching power supplies are operated in parallel for a common load.

0002

2. Description of the Related Art When a plurality of power supplies are operated in parallel to supply power to a common load, a configuration as shown in FIG. 3 is used. That is, the outputs of power supplies #1 to #N (N is an integer of 2 or more) are connected in parallel to commonly supply power to a load (not shown).

[0003] As each of these power supplies #1 to #N, a switching power supply shown in FIG. 2 may be used. The input DC voltage IN is switched in the main power supply circuit section 5 and once converted into AC power, and then rectified and smoothed to be converted back into desired DC power, which becomes the output OUT. This DC output voltage is compared with a predetermined reference voltage in the voltage comparator 2 to generate an error voltage.

This error voltage is transmitted by a photocoupler (consisting of a diode 3A and a transistor 3B),
The signal is derived from the emitter resistor 1 of this transistor 3B and supplied to the stabilization control section 4. This stabilization control section 4 generates a switching pulse having a duty according to this error voltage, controls the on time of the switching element, and controls the on/off of the input voltage to the primary side of the transformer in the main power supply circuit section 5. It is supposed to be done.

[0005] A switching power supply having such a configuration has the drawback that it is necessary to separately adjust the optimum current balancing of each power supply and adjust the output overcurrent detection point, which is complicated.

[0006]

[Object of the Invention] An object of the present invention is to provide a parallel operation current control device that can simultaneously adjust the optimum current balancing of each power source and the optimum output overcurrent detection point. be.

[0007]

According to the present invention, there are provided means for detecting an output voltage and generating an error voltage with respect to a predetermined reference voltage, means for controlling the on-time of a switching element according to the error voltage, and means for controlling an on-time of a switching element according to the error voltage. A plurality of switching power supplies are connected in parallel, each of which has a power transformer that turns on and off the supply of input DC voltage to the primary side through on/off operations, and means that rectifies and smoothes the secondary output of this transformer to generate the output voltage. A parallel operation current control device that performs output current control during operation, comprising current detection means for detecting the magnitude of the output current from the primary side of the transformer and outputting it as a detected voltage, and a detected voltage by the current detection means. means for combining the detected voltage with the error voltage, means for controlling the output voltage to drop by determining that an output overcurrent occurs when the detected voltage exceeds a predetermined value, and a variable resistor for adjusting the value of the detected voltage. A parallel operation current control device is obtained, which is characterized in that it is provided in each switching power source.

[0008]

[Embodiments] Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of an embodiment of the present invention, and parts equivalent to those in FIG. 2 are designated by the same reference numerals. A current detection section 6 is provided to detect a current flowing to the primary side (more precisely, the drain side of the switching transistor) of a transformer (not shown) in the main power supply circuit section 5 . This current detection section 6 includes a current transformer 61 and a rectification and smoothing section 62 that rectifies and smoothes the output of this transformer 61.

This rectified and smoothed current detection output is injected into the emitter side of the photocoupler transistor 3B via a voltage follower 7 consisting of an operational amplifier and a resistor 8, and mixed with an error voltage.

The current detection output becomes an input to a voltage follower 7 via an adjustment resistor 9, and is also input to a rectifying and smoothing circuit comprising a diode 10 and a capacitor 11. This smoothed output is input to the overcurrent drooping terminal of the stabilization control section 4, and when this input voltage exceeds a predetermined value (that is, when the output becomes overcurrent), it operates to droop the output voltage.

Since the other configuration is the same as that of FIG. 2,
The explanation will be omitted.

In this configuration, when the load current increases, a voltage proportional to the power supply output current is generated from the current detection circuit 6, and this is output as a current by the current conversion resistor 8 via the voltage follower 7. This becomes a correction current, mixed with the error voltage, and input to the stabilizing circuit 4. This compensates for a decrease in output voltage due to an increase in load current. Further, the opposite correction is also possible, and the output current can be balanced.

When the output current becomes an overcurrent and exceeds the set value, the smoothed voltage by the capacitor 11 exceeds the set value, and the well-known droop control function provided in the stabilization control circuit 4 operates, causing the output to decrease. Drooping voltage.

By adjusting the variable resistor 9, the current detection circuit 6
Since it is possible to control the detected voltage level from the resistor 9, it is possible to balance the output current and set the overcurrent at the same time by adjusting only this resistor 9.

[0016]

[Effects of the Invention] According to the present invention, when a plurality of switching power supplies are operated in parallel, the optimum input signal level of the output current balancing circuit and the overcurrent control circuit can be adjusted at the same time. This has the effect of improving simplification and reliability.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention.

FIG. 2 is a circuit diagram of a conventional switching power supply.

FIG. 3 is a diagram showing a configuration when power supplies are operated in parallel.

[Explanation of symbols]

2 Voltage comparison section 4 Stabilization control section 5 Main power circuit section 6 Current detection section 9 Variable resistor 10 Rectifier diode 11 Smoothing capacitor 61 Current transformer

Claims (1)

[Claims] 1. Means for detecting an output voltage to generate an error voltage with respect to a predetermined reference voltage, means for controlling the on-time of a switching element according to the error voltage, and controlling the input DC voltage by on/off operation of the switching element. Output current control when operating a plurality of switching power supplies in parallel, each having a power transformer that turns on and off the supply to the primary side, and means for rectifying and smoothing the secondary side output of this transformer to generate the output voltage. A parallel operation current control device comprising: current detection means for detecting the magnitude of the output current from the primary side of the transformer and outputting it as a detected voltage; and combining the detected voltage by the current detection means with the error voltage. Each switching power supply is provided with means for controlling the output voltage to drop when the detected voltage exceeds a predetermined value, determining that an output overcurrent has occurred, and a variable resistor for adjusting the value of the detected voltage. A parallel operation current control device characterized by: