JPH089552A - Parallel running dc power supply device - Google Patents

Abstract

PURPOSE:To reduce the loss of the elective breaking circuit of a parallel running DC power supply, by eliminating the voltage drop of its current sensing circuit through the direct sensing of the current flowing in a MOSFET. CONSTITUTION:Normally, in the drain-source voltage of a MOSFET, the source and drain voltages are brought respectively to a plus and a minus voltages. In this case, when the noninverting and inverting inputs of a voltage discriminator CV are connected respectively with the source and drain of the MOSFET and the sensed drain-source voltage of the MOSFET is fed to the inputs, the MOSFET is turned on by the holding of the output of the voltage discriminator CV in a high voltage. Thereby, the voltage drop of the MOSFET is reduced. Also, when a DC power supply fails, in the drain-source voltage of the MOSFET, the source and drain voltages are brought respectively into minus and plus voltages. Therefore, by the holding of the output of the voltage discriminator CV in a low voltage, the MOSFET is turned off, and thereby, the faulty DC power supply is separated from another DC power supply.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a function of automatically and rapidly disconnecting the output of a failed DC power supply from the output of a normal DC power supply when operating a plurality of DC power supplies in parallel. The present invention relates to a selective cutoff circuit with low loss.

[0002]

2. Description of the Related Art In a DC power supply system that requires high reliability, a plurality of DC power supplies are connected in parallel, and if one of them fails, the system is shut off and the remaining DC power supply continues to provide stable operation. In many cases, a redundant preliminary configuration is adopted in which electric power is supplied to a load under voltage.

When a failure such as a short circuit occurs in the output capacitor, an overcurrent tends to flow to a normal DC power source, and therefore the cutoff circuit added to each output must operate at high speed. (2) Conventionally, this circuit is composed of diodes as shown in Fig. 2 and is a simple circuit with excellent high speed and high reliability. Has the drawback of being large.

Therefore, as a means for solving the above-mentioned drawbacks,
There is a selective cutoff circuit using a MOS-FET as shown in FIG. This circuit includes a current detection circuit DI and a reference voltage V
By the voltage discriminator CV having r, the current flows in the direction shown by the solid line in the normal state, and the voltage of the current detection circuit DI becomes the reference voltage Vr.
If it is higher, the output of the voltage discriminator CV is set to a high level to turn on the MOS-FET.Tr. Further, when the current is small or when the DC power supply fails and the current is about to flow in the direction indicated by the broken line, the voltage of the current detection circuit DI becomes the reference voltage Vr or less, so that the output of the voltage discriminator CV becomes a low level. Turn off the MOS-FET / Tr.

However, even in the selective cutoff circuit shown in FIG.
Since it has a current detection circuit DI, it is a MOS-FET / Tr
It is unavoidable that a loss due to the voltage drop of the current detection circuit DI occurs in addition to the conduction loss of the above.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a selective cutoff circuit for a parallel operation DC power supply having a smaller loss.

[0007]

In the present invention, the MOS-F is used.
By directly detecting the voltage flowing through the ET / Tr, the voltage drop of the current detection circuit was eliminated, and the voltage drop of the selective cutoff circuit at the time of normal operation was significantly reduced, thereby supplying an extremely low loss circuit.

[0008]

When the current flows in the direction indicated by the solid line through the body diode of the MOS-FET / Tr in the normal state (3), the drain-source voltage of the MOS-FET / Tr is positive at the source and negative at the drain.
At that time, if the non-inverting input of the voltage discriminator CV is connected to the source and the inverting input is connected to the drain to detect the drain-source voltage of the MOS-FET Tr, the output of the voltage discriminator CV is maintained high and the MOS-FET is kept.・ Tr turns on, MOS
-The voltage drop of FET-Tr is reduced.

When the DC power supply fails and a current starts flowing in the direction shown by the broken line, the drain-source voltage of the MOS-FET Tr becomes positive and negative, and the output of the voltage discriminator CV is low. Next MOS-F
Turn off ET / Tr and disconnect the failed DC power supply.

[0010]

As described above, according to the circuit of the present invention, when a plurality of DC power supplies are operated in parallel, it has a function of automatically disconnecting the output of a failed DC power supply from a normal DC power supply at high speed. Not only that, by selecting the MOS-FET / Tr, it is possible to provide a selective cutoff circuit with extremely small loss in a normal state, which is effective in reducing the loss, downsizing and weight saving of the DC power supply device. Incidentally, FIG.
Although FIG. 2 and FIG. 3 show examples of parallel operation of two DC power supplies, it goes without saying that the same effect can be obtained by a parallel operation system composed of three or more DC power supplies.

[Brief description of drawings]

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

FIG. 2 Conventional example

FIG. 3 Another embodiment of the related art (4)

[Explanation of symbols]

 A, B DC power supply device a, b DC power supply D Selective blocking diode L load Tr MOS-FET R1, R2, R3, R4 Resistance CV Voltage discriminator DI Current detection circuit

Claims (1)

[Claims] 1. A power supply device for connecting a plurality of direct current power supplies in parallel to supply electric power to a load, wherein the drain of a MOS-FET is connected to the negative output of each direct current output,
The source of the FET is connected to the negative side of the load, and the MO
A parallel operation DC power supply device having a selective cutoff circuit, characterized in that the voltage between the drain and source of the S-FET is detected by a voltage discriminator to control the gate of the MOS-FET.