CN211428903U - Recoverable excess temperature protection circuit - Google Patents
Recoverable excess temperature protection circuit Download PDFInfo
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- CN211428903U CN211428903U CN201922278535.6U CN201922278535U CN211428903U CN 211428903 U CN211428903 U CN 211428903U CN 201922278535 U CN201922278535 U CN 201922278535U CN 211428903 U CN211428903 U CN 211428903U
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- triode
- pnp triode
- resistor
- protection circuit
- temperature protection
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Abstract
The utility model discloses a recoverable over-temperature protection circuit, which comprises a PNP triode, an NPN triode, a thermistor and a divider resistor; the emitting electrode of the PNP triode is connected with the positive electrode of the direct-current power supply, the base electrode of the PNP triode is grounded through the thermistor, and the divider resistor is connected between the emitting electrode and the base electrode of the PNP triode; the collector of the NPN triode is connected with the base of the PNP triode, and the base of the NPN triode is connected with the collector of the PNP triode. The emitter of the NPN triode is grounded; and the collector of the PNP triode is used as a control signal output end of the over-temperature protection circuit. The utility model discloses a circuit occupation space is little, and the cost is lower.
Description
[ technical field ]
The utility model relates to an excess temperature protection circuit especially relates to a recoverable excess temperature protection circuit.
[ background art ]
With the continuous development of electronic technology, the integration level of the circuit board is increased, and the problem of high power consumption inevitably occurs. The temperature rise and the ambient temperature brought by the power consumption promotion can jointly have great influence on the stability and the reliability of the circuit board. Therefore, it is very necessary to add an over-temperature protection circuit on the circuit board. The existing over-temperature protection circuit adopts a comparator or a voltage stabilizer, and the circuit occupies a large space and has higher cost.
[ summary of the invention ]
The to-be-solved technical problem of the utility model is to provide a circuit occupation space is little, the lower recoverable excess temperature protection circuit of cost.
In order to solve the technical problem, the utility model adopts the technical scheme that the recoverable over-temperature protection circuit comprises a PNP triode, an NPN triode, a thermistor and a divider resistor; the emitting electrode of the PNP triode is connected with the positive electrode of the direct-current power supply, the base electrode of the PNP triode is grounded through the thermistor, and the divider resistor is connected between the emitting electrode and the base electrode of the PNP triode; the collector of the NPN triode is connected with the base of the PNP triode, and the base of the NPN triode is connected with the collector of the PNP triode. The emitter of the NPN triode is grounded; and the collector of the PNP triode is used as a control signal output end of the over-temperature protection circuit.
The recoverable over-temperature protection circuit comprises a second resistor, a third resistor, a fourth resistor and a diode, wherein the second resistor is connected with the thermistor in series, and the base electrode of the PNP triode is grounded through the thermistor and the second resistor; the emitting electrode of the NPN triode is grounded through a third resistor, the collecting electrode of the PNP triode is connected with the anode of the diode through a fourth resistor, and the cathode of the diode is used as a control signal output end of the over-temperature protection circuit.
In the recoverable over-temperature protection circuit, the thermistor is a negative temperature coefficient thermistor.
The utility model discloses a but triode and thermistor constitute recovery excess temperature protection circuit, circuit occupation space is little, and the cost is lower.
[ description of the drawings ]
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
Fig. 1 is a schematic diagram of a recoverable over-temperature protection circuit according to an embodiment of the present invention.
[ detailed description of the invention ]
The embodiment of the utility model provides a recoverable excess temperature protection circuit can be used for the charging panel, and its structure and principle are shown as figure 1, including PNP triode Q1, NPN triode Q2, negative temperature coefficient thermistor NTC, divider resistance R1, resistance R2, resistance R3, resistance R4 and diode D1.
An emitter of the PNP triode Q1 is connected with the positive pole VREF _5V of the direct-current power supply, a base is grounded through the negative temperature coefficient thermistor NTC and the resistor R2 which are connected in series, and the divider resistor R1 is connected between the emitter and the base of the PNP triode Q1.
The collector of the NPN triode Q2 is connected with the base of the PNP triode Q1, the base of the NPN triode Q2 is connected with the collector of the PNP triode Q1, and the emitter of the NPN triode Q2 is grounded through a resistor R3.
The collector of the PNP triode Q1 IS connected with the anode of the diode D1 through the resistor R4, the cathode of the diode D1 IS connected with the control signal output end IS of the over-temperature protection circuit, and the control signal output end IS IS externally connected with the controller chip of the charging board.
The resistance value of the negative temperature coefficient thermistor NTC is 15K omega at normal temperature. The recoverable over-temperature protection circuit has three working states: the first working state IS that the NTC thermistor has low temperature and large resistance, the voltage obtained by the base of the PNP triode Q1 IS large and close to the reference voltage of 5V according to a voltage division formula, the PNP triode Q1 and the NPN triode Q2 are not conducted, the IS signal IS low level, and the controller chip control circuit works normally and outputs. In the second working state, along with the increase of the charging current of the charging plate, the temperature of the negative temperature coefficient thermistor NTC IS increased, the resistance value IS reduced, the divided voltage on the base electrode of the PNP triode Q1 IS reduced, the voltage difference value between the positive electrode VREF _5V of the direct current power supply and the base electrode of the PNP triode Q1 IS larger than VBE, the PNP triode Q1 and the NPN triode Q2 are conducted, the IS signal IS changed into 5V, the output of the controller chip IS closed at the moment, and the over-temperature protection IS realized. The third negative working state IS that after the output IS cut off, the temperature of the negative temperature coefficient thermistor NTC IS gradually reduced, the resistance value IS increased until the difference value between the base of the PNP triode Q1 and the positive pole VREF _5V of the direct current power supply IS smaller than VBE, the PNP triode Q1 and the NPN triode Q2 are cut off, the IS signal IS changed back to the low level, the controller chip works again, and the normal output IS recovered.
After the NPN triode Q2 is conducted, the resistor R3 and the resistor R2 are connected with the negative temperature coefficient thermistor NTC in parallel, the overall resistance is reduced, when the temperature is reduced, the resistance of the NTC resistor is increased, and the overall resistance is not increased greatly due to the fact that the resistor R3 is connected in parallel, and therefore the speed of temperature self-recovery can be slowed down. The resistor R4 increases the current for the base of the NPN triode Q2; the unidirectional guiding of the diode D1 can prevent the IS signal from flowing backward.
Claims (3)
1. A recoverable over-temperature protection circuit is characterized by comprising a PNP triode, an NPN triode, a thermistor and a divider resistor; the emitting electrode of the PNP triode is connected with the positive electrode of the direct-current power supply, the base electrode of the PNP triode is grounded through the thermistor, and the divider resistor is connected between the emitting electrode and the base electrode of the PNP triode; the collector of the NPN triode is connected with the base of the PNP triode, and the base of the NPN triode is connected with the collector of the PNP triode; the emitter of the NPN triode is grounded; and the collector of the PNP triode is used as a control signal output end of the over-temperature protection circuit.
2. The recoverable over-temperature protection circuit according to claim 1, comprising a second resistor, a third resistor, a fourth resistor and a diode, wherein the second resistor is connected in series with the thermistor, and the base of the PNP triode is grounded through the thermistor and the second resistor; the emitting electrode of the NPN triode is grounded through a third resistor, the collecting electrode of the PNP triode is connected with the anode of the diode through a fourth resistor, and the cathode of the diode is used as a control signal output end of the over-temperature protection circuit.
3. The recoverable over-temperature protection circuit of claim 1, wherein the thermistor is a negative temperature coefficient thermistor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201922278535.6U CN211428903U (en) | 2019-12-18 | 2019-12-18 | Recoverable excess temperature protection circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201922278535.6U CN211428903U (en) | 2019-12-18 | 2019-12-18 | Recoverable excess temperature protection circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN211428903U true CN211428903U (en) | 2020-09-04 |
Family
ID=72253425
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201922278535.6U Active CN211428903U (en) | 2019-12-18 | 2019-12-18 | Recoverable excess temperature protection circuit |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN211428903U (en) |
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2019
- 2019-12-18 CN CN201922278535.6U patent/CN211428903U/en active Active
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