JPH0964706A - Failure detection method for semiconductor switch for AC power supply switching - Google Patents

Abstract

(57) Abstract: A method for detecting a failure of a semiconductor switch for AC power supply switching, which can particularly utilize a voltage detector for detecting the ON / OFF state of the semiconductor switch even in a synchronized two-system power supply switching system. It is a thing. In a failure detection method for a semiconductor switch for alternating-current power supply, which obtains a failure signal from a logical product of a voltage signal detecting an on / off state of the semiconductor switch and an on command signal of the semiconductor switch, a semiconductor switch is connected in series to a switch unit. By including a diode section and a series circuit of a resistor and a capacitor between the connection point of the switch section and the diode section, and detecting the discharge current of the capacitor,
The semiconductor switch is configured to obtain a detection signal of an on / off state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC power supply switching system for switching a plurality of power supply systems, such as a commercial power supply and an uninterruptible power supply (UPS), and more particularly to a failure detection method for a semiconductor switch that performs AC power supply switching. It is a thing.

[0002]

2. Description of the Related Art First, an AC power supply switching system is as shown in FIG. FIG. 3 is a view for explaining the power supply switching system. Reference numerals 11 and 12 are, for example, UPS and commercial power supply, and are two-system AC power supply system, 2 is load, 3 is semiconductor switch, and 4 is mechanical switch. is there. That is, in the synchronized power supply switching system of the alternating-current power supply systems 11 and 12, the mechanical switch 4 is turned off and the mechanical switch 4 is turned on when the semiconductor switch 3 for supplying power to the load is turned on. During this time, the semiconductor switch 3 performs an operation of turning off, and power is supplied to the load 2 from whichever power source.
Here, it is known that the semiconductor switch is generally bidirectional and is particularly useful for supplying the UPS 11 instantaneously. Instead of the mechanical switch 12, a semiconductor switch similar to the semiconductor switch 11 may be adopted.

Next, a method of detecting a failure of a semiconductor switch used in such a power supply switching system is as shown in FIG. FIG. 4 is shown for explaining the prior art example, 51 is a voltage detector, 52 is an inverter, 53 is a logical product, Sg is an ON command signal to the switch parts 31 and 32 of the semiconductor switch 3, Sf is a failure signal. Here, the voltage detector 51 can detect the voltage when the voltage of the semiconductor switch 3 is in the plus and minus directions and has a voltage equal to or higher than the ON voltage of the semiconductor switch.

In FIG. 4, the semiconductor switch 3 is turned on,
AC power supply system 11 when mechanical switch 4 is off
To the load 2 via the semiconductor switch 3.
At that time, a voltage corresponding to the ON resistance of the semiconductor switch appears at both ends of the semiconductor switch 3, but the output of the voltage detector 51 is not generated, and therefore the logical product 53 does not output the failure signal Sf. When the semiconductor switch 3 is turned off with the ON command signal Sg to the switch parts 31 and 32 of the semiconductor switch 3, almost the power supply voltage appears at both ends of the semiconductor switch 3,
This can be detected by the voltage detector 51, and the logical product of the resultant output of the voltage detector 51 and the inversion signal of the ON command signal Sg via the inverter 52 causes the logical product 53 to be the failure signal Sf.
Can be generated.

[0005]

However, the prior art of this kind has the following problems. That is, the AC power supply systems 11 and 12 are completely synchronized and the voltages are the same,
When the mechanical switch 4 is supplying power to the load 2, no voltage appears at both ends of the semiconductor switch 3 regardless of the ON / OFF command of the semiconductor switch 3. Therefore, the voltage detector 51 cannot generate a signal and cannot judge this signal as the ON / OFF state of the semiconductor switch, so that the open failure at the ON command of the semiconductor switch and the short circuit failure at the OFF command are not detected. Will end up. Therefore, if the AC power supply systems 11 and 12 are out of sync with each other, an excessive cross current may flow in each power supply, and the power may be shut down.

However, the object of the present invention is to
It is another object of the present invention to provide a failure detection method that can effectively use a voltage detector that detects the on / off state of a semiconductor switch even in a synchronized two-system power supply switching system.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and a solution method thereof is configured as follows. That is, in the failure detection method for a semiconductor switch for AC power supply switching, which obtains a failure signal from the logical product of the ON command signal state of the semiconductor switch and the voltage signal for detecting the ON / OFF state of the semiconductor switch, the semiconductor switch is connected in series to the switch section. A diode section and a series circuit of a resistor and a capacitor are provided between the connection point of the switch section and the diode section, and the current on the discharge side of the capacitor is detected to obtain a detection signal of the on / off state of the semiconductor switch. It was done like this.

With such a solution, even in the synchronized two-system power supply switching system, the on / off state of the semiconductor switch can be reliably detected by the power supply detector as described later.

[0009]

More specifically, a diode is provided on the power supply side of a switch portion of a semiconductor switch to be detected, and a series connection of a resistor and a capacitor provided between the switch portion and the diode and a phase different from the connection point. Since the current flowing in the resistor in the circuit is flowing to the discharge side, the ON state of the semiconductor switch is detected by the voltage detector, and by the logical product of the result and the inversion signal of the ON command of the semiconductor switch, It outputs a failure signal of the semiconductor switch. Further, the present invention will be described in detail with reference to the drawings.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the essential structure of an embodiment to which the present invention shown in FIG. 4 is applied. 3'is a semiconductor switch, 51 'is a voltage detector, 61, 62 is resistance, 71, 72
Is a capacitor. In FIG. 1, the semiconductor switch 3'is composed of a series circuit of switch portions 31 'and 32' and diode portions 33 'and 34' as shown in the figure. Also,
Between the connection point of the switch section and the diode section and another phase,
A series circuit composed of resistors 61 'and 62' and capacitors 71 'and 72', respectively, is connected. Furthermore, the voltage detector 51 'receives an input from the connection point of the switch section 31 and the diode 33', and outputs a signal as one input of the logical product 53. Therefore, the voltage detector 51 'captures only the voltage generated in the resistor 62 when the current of the capacitor 72 is flowing to the discharge side.

Now, when the mechanical switch 4 is turned off and the on command signal Sg of the semiconductor switch 3'is given, when the forward current of the diode portion 33 'flows from the AC power supply system 11, it is limited by the resistor 62. The capacitor 72 is charged by the generated current. Further, when the current in the reverse direction of the diode 33 'is flowing, the charge charged in the capacitor 72 flows as a discharge current to the load 2 through the switch portion 31'. In this way, the on / off state of the semiconductor switch 3'can be discriminated by the presence or absence of this discharge current, which is voltage converted by the resistor 62 and can be detected by the voltage detector 51 '.

Therefore, the ON / OFF state of the semiconductor switch is output by the voltage detector 51 ', the output of the voltage detector 51' is given as one input of the logical product 53, and the ON command signal Sg is inverted as the other input. The result of the logical product 53 is given as the fault signal Sf. Since it is detected whether or not a current can be passed through the semiconductor switch in this manner, it goes without saying that it can be detected regardless of the state of the mechanical switch.

FIG. 2 shows the structure of the essential part of another embodiment to which the present invention is applied.
1 "is a voltage detector, 61 ', 62' are resistors, 71 ', 72' are capacitors. That is, the semiconductor switch 3" is composed of switch parts 31 ", 32" and diode parts 33 ", 34",
The resistors 61 'and 62' and the capacitors 71 'and 72' form a series circuit. The voltage detector 51 "consists of a switch 31" and a diode 3
It is configured so as to obtain an input from a 3 ″ connection point. It goes without saying that such a configuration example also has the same function as in FIG.

[0014]

As described above, according to the present invention, the failure detection of the semiconductor switch for switching the synchronized two-system power supply is ensured and the adverse effect due to failure detection is avoided. It is possible to provide a method capable of switching the AC power supply.

[Brief description of drawings]

FIG. 1 is a system diagram showing one embodiment to which the present invention is applied.

FIG. 2 is a system diagram showing another embodiment to which the present invention is applied.

FIG. 3 is a schematic system diagram shown for explaining a power supply switching system.

FIG. 4 is a system diagram shown for explaining the conventional technique.

[Explanation of symbols]

 11 AC power supply system 12 AC power supply system 2 Load 3 Semiconductor switch 3'Semiconductor switch 31 'Switch part 32' Switch part 33 'Diode part 34' Diode part 4 Mechanical switch 51 Voltage detector 51 'Voltage detector 51 "Voltage detector 52 Inverter 53 Logical product 61 Resistor 61 ′ Resistor 62 Resistor 62 ′ Resistor 71 Capacitor 71 ′ Capacitor 72 Capacitor 72 ′ Capacitor Sg ON command signal Sf Fault signal

Claims (1)

[Claims] 1. A bidirectional semiconductor switch provided for supplying power to a load from one of a plurality of AC power supply systems, and an ON command signal state of the semiconductor switch and a voltage signal detecting the ON / OFF state of the semiconductor switch. In a failure detection method for an AC power supply switching semiconductor switch that obtains a failure signal from a logical product, a diode section connected in series to the switch section of the semiconductor switch, and a resistor and a capacitor between the connection point of the switch section and the diode section are provided. A method of detecting a failure of a semiconductor switch for alternating-current power supply, comprising a series circuit, and detecting a current on a discharge side of the capacitor to obtain a detection signal of an on / off state of the semiconductor switch. .