CN212380934U - Overheat protection control circuit for power supply - Google Patents
Overheat protection control circuit for power supply Download PDFInfo
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- CN212380934U CN212380934U CN202020947080.2U CN202020947080U CN212380934U CN 212380934 U CN212380934 U CN 212380934U CN 202020947080 U CN202020947080 U CN 202020947080U CN 212380934 U CN212380934 U CN 212380934U
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- resistor
- pulse width
- width modulator
- power supply
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Abstract
The utility model provides an overheat protection control circuit for power, it can be when switching power supply circuit generates heat, the automatic circuit that opens and shuts, and convenient to use, simple structure, with low costs simultaneously. The pulse width modulator comprises a pulse width modulator, a VCC voltage pin of the pulse width modulator is connected with a negative electrode of a diode D2 and one end of an electrolytic capacitor CD1, the other end of the electrolytic capacitor CD1 is grounded, an anode of the diode D2 is connected with one end of a resistor R5, one end of a resistor R1 and one end of a resistor R6, the other end of the resistor R5 is sequentially connected with a resistor R4, a resistor R3 and a resistor R2 which are connected with an input power Vin, the other end of the resistor R1 is sequentially connected with a transformer winding of the diode D1 and grounded, the other end of the resistor R6 is connected with a base of a triode Q1 and one end of a thermal protector SW, an emitter of the triode Q1 is connected with the other end of the thermal protector SW and grounded, a collector of the triode Q1 is connected with an FB pin.
Description
Technical Field
The utility model relates to a switching power supply technical field specifically is an overheat protection control circuit for power.
Background
The switching power supply circuit generates heat in the operation process, and the components with the largest heat generation amount in the switching power supply circuit are a power switching tube and a transformer. If the heat that produces in this switching power supply circuit can't be timely effectual effluvium, then can make components and parts burnt out thereby lead to switching power supply circuit to operate unusually, perhaps lead to causing the problem of conflagration more seriously. The conventional circuit heat dissipation method is to select a heat dissipation mode of cooling by a heat sink or natural cooling. However, the space of the switching power supply circuit is limited, and a radiator cannot be installed for heat dissipation, so that a natural cooling mode needs to be adopted, and meanwhile, personnel are needed to turn off and turn on the switching power supply circuit at regular time, and the use is inconvenient.
SUMMERY OF THE UTILITY MODEL
Need artifical timing turn-offs, the problem of opening when radiating to current switching power supply circuit, the utility model provides an overheat protection control circuit for power, it can be when switching power supply circuit generates heat, the automatic circuit that opens and shuts, and is convenient to use, simple structure, with low costs simultaneously.
The technical scheme is as follows: an overheat protection control circuit for a power supply, comprising a pulse width modulator, characterized in that: a VCC voltage pin of the pulse width modulator is connected with a cathode of a diode D2 and an anode of an electrolytic capacitor CD1, a cathode of the electrolytic capacitor CD1 is grounded, an anode of the diode D2 is connected with one end of a resistor R5, one end of a resistor R1 and one end of a resistor R6, the other end of the resistor R5 is connected with one end of a resistor R4, the other end of the resistor R4 is connected with one end of a resistor R3, the other end of the resistor R3 is connected with one end of a resistor R2, the other end of the resistor R2 is connected with an input power Vin, the other end of the resistor R1 is connected with a cathode of a diode D1, an anode of the diode D1 is connected with a synonym end of a transformer winding, a synonym end of the transformer winding is grounded, the other end of the resistor R6 is connected with a base of a triode Q1 and one end of a thermal protector SW, an emitter of the triode Q1 is connected with the, the temperature sensing body of the thermal protector SW is arranged on a transformer or a power switch tube of a switch power supply circuit;
it is further characterized in that: the pulse width modulator adopts a UC2842 pulse width modulator, the triode Q1 adopts an MMBT2222A triode, and the thermal protector SW adopts a KSD 9700 thermal protector.
After the structure is adopted, because the utility model discloses an among the overheat protection control circuit for power, pulse width modulator has been set up, through external power Vin in order through resistance R2, R3, R4, R5 reachs partial pressure point A and supplies power for this pulse width modulator, partial pressure point A again passes through triode Q1 and connects this pulse width modulator's FB pin, simultaneously triode Q1's base and the pin of projecting pole connect a thermal protector SW in parallel, thermal protector SW's temperature sensing body is installed on the transformer or the power switch pipe that need the heat dissipation in the external switch power supply circuit, when the temperature does not reach thermal protector SW temperature threshold, thermal protector SW is normally closed, the FB end of pulse width modulator is high level normal work this moment; when the temperature exceeds the temperature threshold of the thermal protector SW, the thermal protector SW is opened, the FB terminal of the pulse width modulator is at a low level, the cycle-by-cycle hiccup type protection of the pulse width modulator is caused, until the temperature is reduced to be below the temperature threshold, the thermal protector SW is quickly reset to be normally closed, the transistor Q1 releases the clamping on the FB terminal, and the FB terminal voltage returns to be normal. Therefore, the automatic switching circuit is realized when the switching power supply circuit is overheated, the use is convenient, the number of components is small, and the cost is low.
Drawings
Fig. 1 is a schematic circuit diagram of the present invention.
Detailed Description
As shown in fig. 1, an overheat protection control circuit for a power supply includes a pulse width modulator (pwm) that uses UC2842, a VCC voltage pin of the UC2842 pwm is connected to a cathode of a diode D2 and an anode of an electrolytic capacitor CD1, a cathode of an electrolytic capacitor CD1 is grounded, an anode of a diode D2 is connected to one end of a resistor R5, one end of a resistor R1 and one end of a resistor R6, the other end of the resistor R5 is connected to one end of a resistor R4, the other end of the resistor R4 is connected to one end of a resistor R3, the other end of the resistor R3 is connected to one end of a resistor R2, the other end of a resistor R2 is connected to an input power source Vin, the other end of the resistor R1 is connected to a cathode of a diode D1, an anode of the diode D1 is connectedThe name end is grounded, the other end of the resistor R6 is connected with the base of the triode Q1 and one end of the thermal protector SW, the emitter of the triode Q1 is connected with the other end of the thermal protector SW and is grounded, and the collector of the triode Q1 is connected with the FB pin of the UC2842 pulse width modulator. Wherein, the transistor Q1 adopts an MMBT2222A transistor, the MMBT2222A transistor works in a saturation region, namely, the emitter junction and the collector junction of the transistor are both in positive bias,U ce≤0.3V，U beabout 0.7V. The KSD 9700 thermal protector is used as a thermal protector SW, the square thermal bimetallic strip is used as a temperature sensing body of the KSD 9700 thermal protector, when the temperature rises to a certain value, the square strip jumps suddenly, the transmission contact rapidly acts, and a circuit is disconnected.
The working principle of the utility model is as follows:
when the pulse width modulator is started, the input voltage Vin is divided by the resistors R2, R3, R4 and R5, so that the voltage at the point A is greater than the sum of the starting threshold voltage of the pulse width modulator with the UC2842 and the forward conduction voltage drop of the diode D2. The voltage at point a is supplied to the VCC power supply terminal of the UC2842 pwm through the diode D2 and reaches the turn-on threshold voltage of the chip, the UC2842 pwm starts to operate, and the transformer winding starts to store energy. The transformer winding is rectified by a diode D1, and a resistor R1 divides voltage and limits current to charge an electrolytic capacitor CD1 at a VCC power supply end of the pulse width modulator, so that the voltage at the VCC power supply end of the UC2842 pulse width modulator is always kept in a stable electric range for the UC2842 pulse width modulator to work in the whole period from energy storage to energy release of the transformer winding.
The temperature sensing body of the thermal protector SW is arranged on a transformer or a power switch tube of a switching power supply circuit which needs heat dissipation from the outside, when the temperature does not reach the temperature threshold of the thermal protector SW, the thermal protector SW is normally closed, the thermal protector SW is in a short-circuit state at the moment, namely the two ends of the base electrode and the emitter electrode of the triode Q1 are short-circuited, and the FB end of the UC2842 pulse width modulator is at a high level and can normally work; when the temperature exceeds the temperature threshold of the thermal protector SW, the thermal protector SW is opened, and the transistor Q1 is switched onU ceIs very small, directly pulls down the FB voltage to a low level close to 0V, and causes the cycle-by-cycle hiccup type protection of the UC2842 pulse width modulator until the temperature is reduced to the temperatureBelow the threshold, the thermal protector SW is quickly reset to be normally closed, the triode Q1 releases the clamp on the FB terminal of the UC2842 pulse width modulator, and the voltage of the FB terminal of the UC2842 pulse width modulator returns to normal. Therefore, the automatic switching circuit is realized when the switching power supply circuit is overheated, and the switching circuit has the advantages of small number of components, small occupied space and low cost; meanwhile, the control design is safe and reliable, the FB end is pulled down to protect the chip, and the typical small current controls the large current; and the response speed is high, the chip can be quickly turned off by overheating, and the chip can work normally after the temperature is reduced.
The above description is only for the preferred embodiment of the present invention, but the protection scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (2)
1. An overheat protection control circuit for a power supply, comprising a pulse width modulator, characterized in that: a VCC voltage pin of the pulse width modulator is connected with a cathode of a diode D2 and an anode of an electrolytic capacitor CD1, a cathode of the electrolytic capacitor CD1 is grounded, an anode of the diode D2 is connected with one end of a resistor R5, one end of a resistor R1 and one end of a resistor R6, the other end of the resistor R5 is connected with one end of a resistor R4, the other end of the resistor R4 is connected with one end of a resistor R3, the other end of the resistor R3 is connected with one end of a resistor R2, the other end of the resistor R2 is connected with an input power Vin, the other end of the resistor R1 is connected with a cathode of a diode D1, an anode of the diode D1 is connected with a synonym end of a transformer winding, a synonym end of the transformer winding is grounded, the other end of the resistor R6 is connected with a base of a triode Q1 and one end of a thermal protector SW, an emitter of the triode Q1 is connected with the, the temperature sensing body of the thermal protector SW is arranged on a transformer or a power switch tube of the switching power supply circuit.
2. The overheat protection control circuit for a power supply according to claim 1, wherein: the pulse width modulator adopts a UC2842 pulse width modulator, the triode Q1 adopts an MMBT2222A triode, and the thermal protector SW adopts a KSD 9700 thermal protector.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202020947080.2U CN212380934U (en) | 2020-05-29 | 2020-05-29 | Overheat protection control circuit for power supply |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202020947080.2U CN212380934U (en) | 2020-05-29 | 2020-05-29 | Overheat protection control circuit for power supply |
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| Publication Number | Publication Date |
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| CN212380934U true CN212380934U (en) | 2021-01-19 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202020947080.2U Active CN212380934U (en) | 2020-05-29 | 2020-05-29 | Overheat protection control circuit for power supply |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113285426A (en) * | 2021-05-28 | 2021-08-20 | 深圳市微源半导体股份有限公司 | Overcurrent protection circuit and device |
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2020
- 2020-05-29 CN CN202020947080.2U patent/CN212380934U/en active Active
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113285426A (en) * | 2021-05-28 | 2021-08-20 | 深圳市微源半导体股份有限公司 | Overcurrent protection circuit and device |
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