JPS60117315A - Fault voltage protecting circuit - Google Patents

Abstract

PURPOSE:To avoid completely the impression of the fault voltage to an electronic device and thd thus to protect assuredly this electronic device, by supplying the electric power to be applied to a fault voltage detecting circuit from the side of a power supply device of a power supply line switch via the 2nd switch. CONSTITUTION:A relay switch RL is put between a battery BT and a power supply input terminal of an electronic device 1, and the electric power to be applied to a fault voltage detecting circuit 2 is supplied from the battery BT of the switch RL via a power supply switch SW. At the same time, the output of the circuit 2 is connected to a relay driver 11 via a time constant circuit 9 to control the switch RL. In such a constitution, the power is supplied to the circuit 2 for the first time after the switch SW is closed. Here the presence or absence of a power supply fault is detected, and the signal of an output terminal is supplied to the driver 11 via the circuit 9. Then the switch RL is closed only in case no fault is detected, and the supply of electric power is possible to the device 1.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. The present invention relates to an abnormal voltage protection circuit, particularly to an abnormal voltage protection circuit used in a vehicle-mounted electronic device.

Conventionally, for example, radio communication equipment mounted on vehicles, etc., has been equipped with an abnormal voltage protection circuit to protect them from high voltages generated when operating the engine switch or driving at high speed. In particular, for those used in radio equipment, etc., measures should also be taken such as cutting off the power supplied to the radio equipment, etc. even if the voltage is so low that the quality of the emitted radio waves deteriorates below the specified value. ing.

As shown in Fig. 1, this method uses an on-vehicle batch IJ-B.
A power line switch such as relay switches R and L is installed between the anode terminal of T and the power terminal of the electronic device etc. 1, and an abnormal voltage detection circuit is added to detect abnormal voltage of the battery BT and supplied thereto. Generally, power is supplied directly from the battery BT, or power is supplied to the abnormal voltage detection circuit from the electronic device side via the relay switches R and L as shown in FIG. Detecting a voltage abnormality, the 2- relay switches R, L1F! : By controlling, the battery, BT, and the electronic device, etc., are disconnected and protected.

However, in the method shown in FIG. 1, power is supplied directly from the battery to the abnormal voltage detection circuit, and dark current is constantly consumed. Therefore, when the battery BT is not used for a long period of time, the capacity of the battery BT is extremely consumed, and the vehicle engine Although dark current does not flow in the circuit shown in Figure 2, the power switch POW@sw may interfere with startup.
f. The abnormality is detected only when power is supplied to both the abnormal voltage detection circuit and the electronic device 1, and the relay switches R and Li are turned off. Therefore, the abnormal voltage is instantly supplied to the device, and during that time, the communication device is damaged. There was a flaw in that it gave .

The present invention has been made in order to eliminate the defects in the conventional abnormal voltage protection circuit as described above. An object of the present invention is to provide an abnormal voltage protection circuit configured to supply power obtained from the terminal via the switch @2 to an abnormal voltage detection circuit, and to control the power line switch after passing the output through a time constant circuit. .

The present invention will be described in detail below based on embodiments shown in the drawings.

FIG. 3 is a block diagram showing one embodiment of the present invention.

In this figure, BT is a battery for a vehicle, etc., which is charged by a dynamo (not shown), and a relay switch R is connected between this and the power input terminal of the electronic device 1 to be protected.
Li is inserted and connected to supply power to the abnormal voltage detection circuit from the batch 17-BT side of the relay switches R and L through the power switch 8W6 and also through the output time constant circuit Ii of the abnormal voltage detection circuit. It is connected to a relay driver, and the output is used to control the relay switches R and L.

In the abnormal voltage protection circuit configured in this manner, power is supplied to the abnormal voltage detection circuit for the first time when the power switch SW is connected, and after detecting whether or not there is an abnormality in the power supply voltage, the output terminal is switched on according to the result. The generated signal is input to the relay driver via a time constant circuit, and the relay switches R and L are connected to supply power to the electronic device 1 only when there is no abnormality in the power supply voltage.

In addition, during the process 1 described above, power is supplied to the electronic device 1, etc., and it is possible to prevent instantaneous abnormal voltages that occur due to transient phenomena when performing operations such as turning on headlights or sounding the horn. The time constant circuit (2) absorbs this and turns off the relay switches R and L only in response to an abnormal voltage that continues for a predetermined period of time or more without responding to it, thereby protecting electronic equipment, etc. from this.

The present invention can be modified as follows.

That is, FIG. 4 is a block diagram showing another embodiment of the present invention, in which the power switch 5Wt is replaced with the vehicle's ignition switch IG-8W, thereby saving the power switch SW. be able to.

Furthermore, to help understand the present invention, the abnormal voltage detection circuit and time constant circuit I will be explained in detail. FIG. 5 shows the abnormal voltage detection circuit in one embodiment of the present invention shown in FIG. and a specific circuit diagram of the time constant circuit I.

In this figure, 2 is an abnormal voltage detection circuit block, which is connected to the resistor R from the battery BT via the power switch 8W6.
・Connect the respective voltage dividing points 3 and 4 to the reference voltage input terminals 5 and 6 of the comparators COMPI and COMP2. At the same time, the power switch 8Wy is connected to the comparison signal input terminals 7 and 8 from the batch IJ-BT.
The voltage obtained through z is divided by resistors R.3 and B and 4 and inputted.

Further, the two outputs of the comparators COMF* and COMP* are input to the inverter circuit INV via the logical sum circuit OR, and the output thereof is configured by a resistor R, 5 reset speed-up diode D1, and capacitor C+. Transistor T for relay driver via time constant circuit
The emitter E of this transistor Tr is connected to the base B of the transistor Tr, and the collector C is connected to the relay switch R, L.
One end of the drive coil L and the other end of the coil L are respectively connected to the output end of the batch IJ-BT.

In the circuit configured as above, the Zener diodes Z1 and Z2 determine the highest reference potential and the lowest reference potential, and the power supply voltage obtained from the battery applied to the other input terminals 7 and 8. If it deviates from this, it is regarded as an abnormal voltage and the logical sum circuit O
Further, the H1 potential is applied to the output terminal of R, and this is made into the opposite LO potential in the inverter circuit INV of the next stage, and the relay driver transistor Trl=i is turned OFF, and the electronic device 1 and the battery BT are disconnected and protected. do.

The power relays R and L are not limited to this, and may be, for example, semiconductor switches.

Since the present invention is constructed as described above, power consumption is low by adding an extremely simple circuit, and since no abnormal voltage is applied to the electronic device even if it is instantaneous, the electronic device etc. can be reliably protected from abnormal voltage. It is very effective in doing so.

[Brief explanation of drawings]

1 and 2 are block diagrams showing a conventional abnormal voltage detection circuit, FIG. 3 is a block diagram showing one embodiment of the present invention, and FIG. 4 is a block diagram showing another embodiment of the present invention. figure,
FIG. 5 is a circuit diagram showing an example of the specific circuit shown in FIG. 3. 1...Electronic equipment to be protected, 2...
...Abnormal voltage detection circuit, 9...Time constant circuit. 11...Relay driver circuit, BT
・・・・・・・・・-Batch IJ-, R, L・・・・・・
...Relay switch, SW...Mountain...Power switch Patent applicant Toyo Tsushinki Co., Ltd.

Claims (1)

[Scope of Claims] 1. A power line switch is provided between a power supply device and an electronic device to be protected from abnormal voltages generated by the power supply device or mixed therein, and a power line switch is provided between the power supply device and an electronic device to be protected from abnormal voltages generated by the power supply device or mixed therein. In an abnormal voltage protection circuit configured to open and close the power line switch using the output of an abnormal voltage detection circuit that detects all abnormal voltages, the power to be applied to the abnormal voltage detection circuit is supplied to the power supply device side of the power line switch. from the second
An abnormal voltage protection circuit characterized in that the voltage is supplied through a switch. 2. The abnormal voltage protection circuit according to claim 1, wherein the second switch is replaced by an ignition switch in a vehicle or the like.