CN208571577U - Thermal-shutdown circuit - Google Patents
Thermal-shutdown circuit Download PDFInfo
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- CN208571577U CN208571577U CN201820638055.9U CN201820638055U CN208571577U CN 208571577 U CN208571577 U CN 208571577U CN 201820638055 U CN201820638055 U CN 201820638055U CN 208571577 U CN208571577 U CN 208571577U
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Abstract
The utility model discloses a kind of thermal-shutdown circuits; including temperature sensing circuit and control circuit; the input of the output connection control circuit of the temperature sensing circuit; the temperature sensing circuit be resistor voltage divider circuit, resistor voltage divider circuit include detect temperature NTC thermistor RT and with the concatenated resistance R4 of NTC thermistor RT.The utility model detects the variation of temperature by thermistor; the detection of temperature change is realized using resistor voltage divider circuit; and then it is compared using the 2.5V reference voltage inside controllable accurate source of stable pressure TL431 with control terminal input voltage; to control the on-off of triode; it realizes to by the defencive function of protection circuit; the resistance R4 control circuit self- recoverage temperature spot of control circuit is utilized simultaneously, and circuit structure is simple, reliable and stable.
Description
Technical field
The utility model belongs to electronic circuit technology field, and in particular to a kind of thermal-shutdown circuit.
Background technique
Currently, many electronic products are at work, due to overload, over-voltage or certain component damages, cause entirely to produce
The core circuit device failure of product, although being typically provided with overload protection and overvoltage protection in circuit, if overvoltage protection or
Person's overload protecting circuit breaks down, and cannot play a protective role, at this point, just can avoid such ask using overheat protector
Topic, but the thermal-shutdown circuit that generallys use or too simple cannot play a very good protection or excessively complicated need
Want the devices such as temperature dependent sensor.
Utility model content
The utility model technical issues that need to address are to provide a kind of simple excess temperature with self-recovering function of structure and protect
Protection circuit.
To solve the above problems, technical solution adopted in the utility model is:
A kind of thermal-shutdown circuit, including temperature sensing circuit and control circuit, the output of the temperature sensing circuit
The input of control circuit is connected, the temperature sensing circuit is resistor voltage divider circuit, and resistor voltage divider circuit includes detection temperature
NTC thermistor RT and with the concatenated resistance R4 of NTC thermistor RT.
Further, the control circuit includes resistance R1-R3, control chip Q1, triode Q2, Q3, diode D1,
In, control chip Q1 is TL431, resistance R4 and NTC thermistor in the control terminal connection resistor voltage divider circuit of control chip Q1
The connecting node of RT, while the collector through resistance R3 connecting triode Q2 control the plus earth of chip Q1, control chip Q1
Cathode successively meet power supply VCC through resistance R2, resistance R1, the base stage of the connecting node connecting triode Q2 of resistance R1, R2, three
The transmitting of pole pipe Q2 connects power supply VCC, the base stage of the quiet diode D1 connecting triode Q3 of the collector of triode Q2, triode
Q3 is for controlling by the on-off of protection circuit.
The beneficial effects of adopting the technical scheme are that
The utility model detects the variation of temperature by thermistor, realizes temperature change using resistor voltage divider circuit
Detection, and then be compared using the 2.5V reference voltage inside controllable accurate source of stable pressure TL431 with control terminal input voltage,
To control the on-off of triode, realizes and control by the defencive function of protection circuit, while using the resistance R4 of control circuit
Circuit self- recoverage temperature spot, circuit structure is simple, reliable and stable.
Detailed description of the invention
Fig. 1 is the utility model circuit diagram；
TL431 control terminal partial pressure equivalent schematic diagram when Fig. 2 is Fig. 1 triode Q2 conducting.
Specific embodiment
Utility model is described in further detail with reference to the accompanying drawing:
As shown in Figure 1, the utility model includes temperature sensing circuit and control circuit, the temperature sensing circuit it is defeated
The input of control circuit is connected out, and the temperature sensing circuit is resistor voltage divider circuit, and resistor voltage divider circuit includes detection temperature
NTC thermistor RT and connect and be followed by with resistance R4 with the concatenated resistance R4 of NTC thermistor RT, NTC thermistor RT
Between power supply VCC and ground.
The control circuit includes resistance R1-R3, controls chip Q1, triode Q2, Q3, diode D1, wherein control core
Piece Q1 is TL431, the connection section of resistance R4 and NTC thermistor RT in the control terminal connection resistor voltage divider circuit of control chip Q1
Point, while the collector through resistance R3 connecting triode Q2, control chip Q1 plus earth, control chip Q1 cathode according to
It is secondary to connect power supply VCC, the base stage of the connecting node connecting triode Q2 of resistance R1, R2, the hair of triode Q2 through resistance R2, resistance R1
Connection power supply VCC is penetrated, the base stage of the quiet diode D1 connecting triode Q3 of the collector of triode Q2, triode Q3 is for controlling quilt
Protect the on-off of circuit.
Working principle
When temperature is not up to overheat protector point, resistance R4 both ends power supply is lower than 2.5V in resistor voltage divider circuit, controls core
It is not turned between the anode and cathode of piece TL431, biasing resistor R1 makes triode Q2 base stage high level, and triode Q2 is not led
Logical, then triode Q3 is not turned on, and is worked normally by the circuit of Q3 protection.
As the temperature rises, thermistor RT resistance value reduces, and resistance R4 both end voltage increases, when resistance R4 both end voltage
When higher than 2.5V, control chip TL431 conducting, resistance R1, R2 are connected internal resistance with control chip TL431 and constitute bleeder circuit, from
And drag down triode Q2 base voltage, triode Q2 conducting, triode Q3 conducting, starting protection is protected circuit not work.
The setting of temperature protection point:
V*R4/ (R4+RT)=2.5V
R4 can any value, after determining RT resistance value, look into thermistor RT parameter list, determine overheat protector point.
Thermal-shutdown circuit has defencive function, and when the temperature is excessively high, circuit operation should be able to be automatic extensive when temperature reduces
Normal operating conditions is answered, the resistance R3 in figure is the device for setting its temperature spot of resuming work.
When triode Q2 conducting, TL431 control terminal divides equivalent schematic diagram as shown in Fig. 2, resistance R3 and thermistor
RT is at parallel relationship, at this time, it is desirable to which excess temperature circuit does not work, i.e., resistance R4 both end voltage is less than 2.5V, therefore the both ends resistance R4
Voltage=V*R4/ (R4+R3*RT/ (R3+RT)).
Specific overheat protector temperature spot and self- recoverage temperature spot calculation formula are as follows:
Overheat protector temperature spot: V*R4/ (R4+RT1)=2.5V, RT1 are the thermistor resistance after the setting of overheat protector point
Value.Self- recoverage temperature spot: thermistor resistance value when V*R4/ (R4+RT2*R3/ (RT2+R3))=2.5V, RT2 are self- recoverage.
Claims (2)
1. a kind of thermal-shutdown circuit, it is characterised in that: including temperature sensing circuit and control circuit, the temperature detection electricity
The input of the output connection control circuit on road, the temperature sensing circuit are resistor voltage divider circuit, and resistor voltage divider circuit includes inspection
The NTC thermistor RT of testing temperature and with the concatenated resistance R4 of NTC thermistor RT.
2. thermal-shutdown circuit according to claim 1, it is characterised in that: the control circuit includes resistance R1-R3, control
Coremaking piece Q1, triode Q2, Q3, diode D1, wherein control chip Q1 is TL431, and the control terminal of control chip Q1 connects electricity
The connecting node of resistance R4 and NTC thermistor RT in bleeder circuit, while the collector through resistance R3 connecting triode Q2 are hindered,
The plus earth of chip Q1 is controlled, the cathode of control chip Q1 successively meets power supply VCC through resistance R2, resistance R1, resistance R1, R2's
The transmitting of the base stage of connecting node connecting triode Q2, triode Q2 connects power supply VCC, the quiet diode of the collector of triode Q2
The base stage of D1 connecting triode Q3, triode Q3 is for controlling by the on-off of protection circuit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201820638055.9U CN208571577U (en) | 2018-04-28 | 2018-04-28 | Thermal-shutdown circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201820638055.9U CN208571577U (en) | 2018-04-28 | 2018-04-28 | Thermal-shutdown circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN208571577U true CN208571577U (en) | 2019-03-01 |
Family
ID=65480068
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201820638055.9U Active CN208571577U (en) | 2018-04-28 | 2018-04-28 | Thermal-shutdown circuit |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN208571577U (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112462841A (en) * | 2020-10-29 | 2021-03-09 | 国网山东省电力公司东营市东营区供电公司 | Automatic gear shifting device for real-time monitoring transformer |
-
2018
- 2018-04-28 CN CN201820638055.9U patent/CN208571577U/en active Active
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112462841A (en) * | 2020-10-29 | 2021-03-09 | 国网山东省电力公司东营市东营区供电公司 | Automatic gear shifting device for real-time monitoring transformer |
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