KR900000827Y1 - Overvoltage protective circuit - Google Patents

Abstract

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Description

Overvoltage and overheat protection circuit

1 is a schematic block diagram of an overvoltage and overheat protection circuit according to the present invention.

2 is a circuit diagram of the present invention.

* Explanation of symbols for main parts of the drawings

1: overvoltage detection part 2: power cutoff part

3: display device and buzzer drive unit 4: temperature sensing unit

REQ: Regulator RY: Relay

SW1, SW2: Switch TR1 to TR3: Transistor

BU: Buzzer LED1, LED2: Light Emitting Diode

D ₁ , D ₂ : Diode IC: Microprocessor for Overheat / Overvoltage Detection

OP: Comparator TH: Dummyster

VR: Variable resistor

[Industrial use]

The present invention provides overvoltage and overheating to protect electronic devices from overvoltage caused by external voltage fluctuation caused by external voltage fluctuation in precision measuring instrument or home electronics requiring precision. It relates to a prevention circuit.

[Traditional Technology and Problems]

In general, the operating power for operating precision measuring instruments or household electronics is supplied to each circuit through regulators that output constant voltage and current regardless of input voltage or output load change. If the old regulator malfunctions due to various reasons (i.e. overvoltage or short circuit). If an overvoltage or unstable voltage (overvoltage) is output higher than the specified voltage, and this abnormal voltage is applied to a device such as a precision instrument that requires precision, the device is not only fixed or broken, There was a disadvantage that it could not be measured.

[Purpose of designation]

The present invention is designed to solve the above problems, and when an abnormal voltage is output from the regulator due to an overvoltage or a short circuit, such an abnormal voltage is detected to cut off the input power so that unstable power is not applied to the device. It prevents damage to the device and detects the overheating condition and cuts off the input power even when the main components of the device are overheated, and operates the light emitting diode and the buzzer to inform the status of the overvoltage and overheat protection circuit. The purpose is to provide.

[Composition of design]

The present invention for achieving the above object is an overvoltage detector (1) consisting of a resistor (R1 to R3), a capacitor (C1) and a microprocessor (IC) for overheating and overvoltage detection, a transistor (TRl) and a diode (Dl) ), A power cut-off unit (2) which is composed of contact switches (SW1, SW2) of the relay (RY) and cuts off the input power when an overheat / overvoltage detection signal is output from the microprocessor (LC) for overheating and overvoltage detection; Light emitting diodes (LED1, LED1) and buzzer (BU). The display device comprising the resistors R4 to R6 and the transistors TR2 and TR3 to indicate whether an abnormal state is present, and the auxiliary driving unit 3, the resistors R7 to R9, the variable resistor VRl, and the negative temperature characteristics. It consists of a bridge circuit of the MR TH, a diode D2 and a comparator OP, and a temperature sensing section 4 which detects overheating of the main elements.

(Action)

The present invention configured as described above is an overheating in the overvoltage detector (1) when the operating voltage is output from the regulator (REQ) or the temperature voltage is output from the dummy (TH). When the overvoltage detection microprocessor IC detects the voltage output from the regulator REQ and the overheat status signal from the temperature sensing unit 4 and determines that the signal is in a normal state, the low level signal is returned to an abnormal state. When it is determined, the high level signal is output to the power cutoff unit 2, respectively. That is, in an abnormal state, a high level signal is applied from the overvoltage detector 1 to the power cutoff unit 2 so that the contact switch SW1 of the relay RY of the power cutoff unit 2 is turned off while the switch SW2 is turned off. ) Is turned on so that the input power becomes full.

Then, the display device and the buzzer driver 3 are in an abnormal state. By operating the light-emitting diode LED2 and the unit BU indicating that abnormal power is applied by the high level signal output from the output terminal VOP of the IC, the user can detect the abnormal state and take further action. It is supposed to be.

(Example)

Below. One embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Figure 2 illustrates in detail the overvoltage and overheat protection circuit according to the present invention. When a normal voltage is applied from the voltage input terminal Vin, a stable voltage is output from the output side of the regulator REQ. Therefore, the overvoltage input device Vi of the microprocessor IC for overheating and overvoltage detection in the overvoltage detection unit 1 is provided. When the rated voltage signal is applied and the heat generation phenomenon due to the abnormal voltage is not detected in the temperature sensing unit 4 installed near the main element, the resistance value of the dummyster TH in the temperature sensing unit 4 is detected. Since the signal is kept high, a low level signal is output from the comparator OP, and the overheat detection signal input terminal Vit of the overheat and overvoltage detection microprocessor IC is connected via the resistor R9 and the diode D2. ) Is entered.

Then, the overheat / overvoltage detection microprocessor IC determines the current state as a normal state and outputs a low level signal from its output terminal OUT. The low level signal output from the overvoltage detection microprocessor IC is applied to the base of the transistor TR1 in the power interrupting unit 2 through the resistor Rl. Accordingly, since the transistor TR1 is turned on by a low level signal applied to the base terminal, the relay RY connected to the collector side is not driven so that the contact switch SW1 of the relay RY is turned off. Will be maintained. Therefore, the normal input terminal Vin is sequentially measured through the switch SW1 and the regulator REQ.

Not supplied). In addition, in the display device and the buzzer driver 3, when the low state signal is output to the output side OUT of the microprocessor LC for overheating and overvoltage detection, the low state of the control terminal Vo is output. By the level signal, for example, a light emitting diode LEDl emitting blue color is emitted to indicate that a normal voltage is not applied.

Meanwhile. When an abnormal power supply is supplied due to various reasons and an unstable power supply (or overvoltage) is output from the regulator (REQ), overheating and overvoltage detection in the overvoltage detection section (I) is caused by the overvoltage output from the regulator (REQ). The abnormal voltage signal is inputted to the overvoltage input terminal Vin of the microprocessor IC for use, while the temperature sensing unit 4 mounted near the main element causes the resistor R7 ( R8) and the resistance of the dummyster TH formed in the bridge form with the variable resistor VR1 are gradually reduced to increase the voltage input to the non-inverting terminal (+) of the comparator OP. therefore. The high level signal is output from the comparator OP through the resistor R9 and the diode D2 to the overheat detection signal input terminal Vi of the microprocessor LC for overheating and overvoltage detection.

Accordingly, when the microprocessor IC receives a high level signal at the overheat detection signal input terminal Vi, a high level signal is output to the output terminal out, and the microprocessor IC outputs a high level signal to the power supply terminal 2 through the resistor R1. The transistor TRl is turned on because it is input to the base terminal of the transistor TRl. Then, the coil of the relay RY is magnetized so that the contact switch SW1 is turned off, while the switch SW2 is connected, so that the abnormal power input, which is input only to the voltage input Vin, is cut off.

At this time. The state of the display device and the buzzer driver 3 is as follows.

The microprocessor IC for overheating and overvoltage detection is configured to output a low level signal, which is the same as the high level signal of the output terminal OUT, to the control terminal Vo, whereby the transistor TR2 is turned on. As a result, the light emitting diode LED2 emitting red color emits light, so that the base terminal of the transistor TR3 becomes low level. The transistor TR3 is turned on and the buzzer BU is operated. In other words. As well as the abnormal power is automatically cut off, the user can know that the abnormal power is applied by the light emission of the red light emitting diode LED2 and the buzzer BU.

Meanwhile. Even when the regulator (REQ) is outputting a normal power source, the main element may generate heat due to a short circuit or an abnormality in the circuit. In this case, the microprocessor for the fibrillation and overvoltage detection in the overvoltage detection unit 1 ( The low voltage signal is input to the overvoltage input terminal Vin of lC, but is further connected in a bridge form with the resistors R7.R8 and the variable resistor VRl in the temperature sensing unit 4 provided near the main element. Since the resistance of the MR TH is reduced so that the voltage applied to the non-inverting terminal (+) of the comparator OP is higher than the voltage applied to the inverting terminal (-), the comparator OP outputs a high level signal. The high level signal is inputted to the overheat detection signal input terminal Vi of the microprocessor IC for overheating and overvoltage detection through the diode D2. therefore. When a high level signal is input to either one of the overvoltage input terminal Vi and the overheat detection signal input terminal Vi, the overtemperature and overvoltage detection outputs a high level signal from the output terminal OUT. A microprocessor (LC) senses a high level signal input to the overheat detection signal input terminal (Vit), detects a high level signal at its output terminal (OUT), and a high level signal at its output terminal (OUT). Therefore, as described above, the transistor TRl is turned on, the relay RY is magnetized, and the contact switch SW1 operating in interlocking operation is turned off, and the contact switch SW2 is turned on. Vin) is cut off. At the same time, in the display device and the buzzer moving part 3, the light emitting diode RED2 emitting red light is emitted and the buzzer BU is raised as described above to inform the user of an abnormal state.

[Effect of design]

As described above, the present invention automatically cuts off the power supply when the main device is overheated due to various causes such as when overvoltage is applied to the regulator or short circuit inside the circuit. As it informs the user by the buzzer sound, it can not only protect the main precision device from overvoltage but also improve the precision of the precision device by always outputting only the rated voltage.

Claims (1)

An overvoltage detection section I, a transistor TR1, and a diode Dl comprising resistors R1 to R3, a capacitor C1, and a microprocessor IC for overheating and overvoltage detection. Power switch (2) Light-emitting diode which consists of contact switch (SW1.SW2) of relay RY and cuts off input power when signal for overheat and overvoltage detection is supplied from microprocessor 1C for overheat and overvoltage detection. (LED1, LED2) and buzzer (BU). Resistors R4 to R6 and transistor {TR1. TR3) and a display device for indicating an abnormal state and a bridge circuit and diode (D2) comprising a resistor (R7 to R9), a variable magnet (VR1), and a dummyster (TH) of negative temperature characteristics. ) And a comparator (OP) consisting of a temperature sensing unit (4) for detecting overheating of the main element.