JPH0319007A - Power unit - Google Patents

Abstract

PURPOSE:To stop the output with no fear of fuming and to improve the safety for a power unit by using an overvoltage protecting circuit and securing the serial connection between a discharge resistance and the voltage detecting resistances for detection of the output voltage. CONSTITUTION:An overvoltage protecting circuit 9 is set between an ON/OFF circuit 2 and an output terminal of a power circuit 1. At the same time, one of both terminals of the voltage detecting resistances 6 and 7 connected in series is connected between a discharge resistance 3 and a transistor TR 5. Thus the resistance 3 can detect the output voltage of the circuit 1 together with the resistances 6 and 7. Furthermore the working of the circuit 1 is stopped by the circuit 9 at abnormality. That is, the detection value of the output voltage is reduced and the output voltage rises up for an instant with occurrence of a trouble of the circuit 2 or the TR 5 for ON/OFF control of the resistance 3. Under such conditions, the circuit 9 works to stop the power supply. As a result, the resistance 3 has no fuming and the safety is improved for a power unit.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a TL power supply device.

[Conventional technology]

FIG. 2 shows a conventional example of the m jliF IW arrangement.

As shown in the figure, the TL power supply circuit is on/off controlled by the on/off circuit 2, and the discharge resistor 3 rapidly releases the charge when the capacitor 4 is off, so that the transistor 5 is turned on when the m source is off. It is set to turn on. Further, the output voltage is detected by a detection resistor 6.7, and the output is stabilized. Since this discharge resistor 3 is used only to discharge the charge of the capacitor 4, a relatively small one is sufficient.

However, when the on-off circuit 2 or the transistor 5 fails, that is, when the transistor 5 is turned on even when the ffi source circuit 1 is turned on, the t! ! Set. In this case, the discharge resistor 3 is constantly overloaded and there is a risk of burnout. 1, conventionally, a temperature fuse 8 is attached to the discharge resistor 3 1 to serve as a cutoff circuit in case of an abnormality.

[Problem to be solved by the invention]

In the above-mentioned conventional technology, although the discharge resistance does not reach a troublesome tM due to the use of a temperature fuse, there is a risk that smoke may be generated until the temperature fuse is blown. Furthermore, even if the fuse blows, the output voltage does not drop, which poses a safety problem.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a power supply device with improved safety.

[Means to solve the problem]

The above object is to provide an overvoltage protection circuit between the on/off circuit and the output terminal of the power supply circuit, and connect one terminal of the voltage detection resistor connected in series between the discharge resistor and the transistor. This is achieved by enabling the Group M resistor to detect the output voltage of the power supply circuit together with the voltage detection resistor, and by stopping the power supply circuit using an overvoltage protection circuit in the event of an abnormality.

(Function) Since the above means is provided, in the event of an abnormality, the overvoltage protection circuit can be used without using a temperature fuse as in the conventional case.
Since the circuit is now stopped, smoke from the discharge resistor no longer occurs as in the past, and safety can be improved.

In other words, failure of the on/off circuit or on/off of the discharge resistor.
When a failure occurs in the off-transistor, the detected value of the output voltage drops and the output voltage rises momentarily, but the overvoltage protection circuit operates and shuts down the power supply.

(Embodiment) The present invention will be explained below based on the illustrated embodiment. An embodiment of the present invention is shown in FIG. In this embodiment, an overvoltage protection circuit 9 is provided between the on/off circuit 2 and the output terminal of the power supply circuit 1, and one terminal of the voltage detection resistor 6.7 connected in series is connected to the discharge resistor 3. and the transistor 5, so that the discharge resistor 3 and the voltage detection resistor 6.7 can detect the output voltage of the power supply circuit 1, and in the event of an abnormality, the power supply circuit 1 is By doing this, in the event of an abnormality, the 21i source can be stopped by the overvoltage protection circuit 9 without using a temperature fuse as in the conventional case, and the 21i source can be stopped as usual. It is possible to obtain an MR device in which smoke generation from the discharge resistor 3 is eliminated and safety can be improved.

That is, to detect the output voltage, the discharge resistor 3 and the voltage detection resistor 6.7 are connected in series. Further, an overvoltage protection circuit 9 is provided which stops outputting when the voltage becomes slightly higher than the normal output voltage.

By doing this, the on/off circuit 2 or the transistor 5 will break down, and? Even when the lfa circuit 1 is on, assuming that the transistor 5 is in the on mode, the horizontal output value of the output voltage is ov,
The output voltage will rise momentarily. However, the overvoltage protection circuit 9, which is set to operate at a voltage slightly higher than the output voltage, immediately stops the output, improving safety.

As described above, according to this embodiment, the output can be stopped without the risk of smoke generation, so safety can be improved. Furthermore, since no temperature fuse is used, reliability is also improved.

〔Effect of the invention〕

As described above, the present invention improves the safety of the power supply device, thereby making it possible to obtain a power supply device with improved safety.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the power supply device of the present invention, and FIG. 2 is a circuit diagram of a conventional W1 power supply device. 1...Power supply circuit, 2...On/off circuit, 3...
Discharge resistor, 4... Capacitor, 5... Transistor, 6.7... Voltage detection resistor, 9... Overvoltage protection circuit.

Claims (1)

[Claims] 1. An on/off circuit that turns on and off the power supply circuit, a voltage detection resistor that detects the voltage between both terminals of the power supply circuit, and a capacitor connected in parallel with the voltage detection resistor between the terminals. and a discharge resistor that discharges the capacitor only when the power supply circuit is off, and a transistor connected in series with the discharge resistor and turned on and off when the power supply circuit is off, between the two terminals. In the power supply device, an overvoltage protection circuit is provided between the on/off circuit and the output terminal of the power supply circuit, and one terminal of the voltage detection resistor connected in series is connected between the discharge resistor and the transistor. , so that the discharge resistor can detect the output voltage of the power supply circuit together with the voltage detection resistor, and the overvoltage protection circuit can stop the power supply circuit in the event of an abnormality. power supply.