CN215817500U - Over-temperature protection circuit and electric appliance - Google Patents
Over-temperature protection circuit and electric appliance Download PDFInfo
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- CN215817500U CN215817500U CN202121526340.XU CN202121526340U CN215817500U CN 215817500 U CN215817500 U CN 215817500U CN 202121526340 U CN202121526340 U CN 202121526340U CN 215817500 U CN215817500 U CN 215817500U
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Abstract
The utility model provides an over-temperature protection circuit and an electric appliance, wherein the over-temperature protection circuit comprises: the load, give the working power supply of load power supply, switch the load with the switching unit of working power supply on-off state, and give the control power supply of switching unit power supply still include: the protection circuit is arranged between the switching unit and the control power supply; when the temperature of the load is higher than a preset over-temperature protection point, the protection circuit cuts off the switching unit to enable the switching unit to cut off the load; when the temperature of the load is lower than a preset over-temperature protection point, the protection circuit conducts the switching unit to enable the switching unit to start the load. Compared with the prior art, the utility model can turn off the load when the load is over-temperature, thereby playing the over-temperature protection function, and can turn on the load again when the load is restored to normal temperature, thereby operating the electric appliance.
Description
Technical Field
The utility model belongs to the field of electric appliances, and particularly relates to an over-temperature protection circuit and an electric appliance.
Background
Along with the improvement of living standard, electronic products in home are increasing day by day, and the safety degree to life electrical apparatus is also increasing more and more simultaneously. For example, in the case of an over-temperature condition caused by improper use of a heating type load such as an auxiliary heater, the load may be damaged even if the load is operated under the over-temperature condition for a long time. Adopt the mode of fuse series connection to protect among the prior art usually, when the temperature reaches a definite value, the fuse can fuse and then turn off the load, nevertheless adopts the mode of fuse, and after the temperature of load resumes normally again, because the problem of fuse fusing, the unable operating condition that resumes of circuit can not be maintained again, just can reuse after needing to maintain.
Therefore, it is an urgent technical problem in the art to design an over-temperature protection circuit and an electrical appliance that can turn off a load to perform over-temperature protection when the load is over-temperature and can turn on the load again when the load returns to normal temperature.
SUMMERY OF THE UTILITY MODEL
The utility model provides an over-temperature protection circuit and an electric appliance, aiming at the problem that in the prior art, when the temperature of a load is recovered to be normal, the load cannot recover to work again.
The technical scheme of the utility model is that an over-temperature protection circuit is provided, which comprises: the load, give the working power supply of load power supply, switch the load with the switching unit of working power supply on-off state, and give the control power supply of switching unit power supply still include: the protection circuit is arranged between the switching unit and the control power supply;
when the temperature of the load is higher than a preset over-temperature protection point, the protection circuit cuts off the switching unit to enable the switching unit to cut off the load;
when the temperature of the load is lower than a preset over-temperature protection point, the protection circuit conducts the switching unit to enable the switching unit to start the load.
Further, the protection circuit comprises a first change-over switch connected in series between the control power supply and the switching unit, and a second change-over switch for controlling the on-off state of the first change-over switch;
when the second switch is switched on, the first switch is switched on, and the switching unit is further switched on, so that the load is started;
when the second switch is turned off, the first switch is turned off, and the switching unit is cut off, so that the load is turned off.
Further, the protection circuit further includes:
an over-temperature detection unit: monitoring whether the temperature of the load is higher than the over-temperature protection point;
an over-temperature switching unit: the second change-over switch is connected with the over-temperature detection unit and the second change-over switch, and is switched off when the over-temperature detection unit detects that the temperature of the load is higher than the over-temperature protection point; and when the over-temperature detection unit detects that the temperature of the load is lower than the over-temperature protection point, the second change-over switch is switched on.
Further, the over-temperature switching unit comprises a first over-temperature switch connected with the over-temperature detection unit and a second over-temperature switch connected with the first over-temperature switch and the second switch;
when the over-temperature detection unit detects that the temperature of the load is higher than the over-temperature protection point, the first over-temperature change-over switch is switched on, and then the second over-temperature change-over switch is switched on, so that the second change-over switch is switched off;
when the over-temperature detection unit detects that the temperature of the load is lower than the over-temperature protection point, the first over-temperature change-over switch is switched off, and then the second over-temperature change-over switch is switched off, so that the second change-over switch is switched on.
Further, the over-temperature detecting unit includes a thermistor RX and a resistor R1 connected in series between the control power supply and ground, and the over-temperature switching unit is connected between the thermistor RX and the resistor R1;
when the temperature of the load reaches the over-temperature protection point, the resistance value of the thermistor RX reaches a preset resistance value, and the over-temperature detection unit sends an over-temperature signal so as to conduct the first over-temperature change-over switch;
when the temperature of the load is lower than the over-temperature protection point, the resistance value of the thermistor RX is lower than a preset resistance value, and the over-temperature detection unit sends a normal-temperature signal so as to turn off the first over-temperature change-over switch.
Further, the over-temperature switching unit comprises a transistor Q3 and a transistor Q4;
the emitter of the triode Q3 is connected with a reference voltage, the base of the triode Q3 is connected with the over-temperature detection unit, the collector of the triode Q4 is connected with the base of the triode Q4, the collector of the triode Q4 is connected with the second change-over switch, and the emitter of the triode Q8926 is grounded;
and the base electrode of the triode Q3 is conducted when receiving an over-temperature signal and is switched off when receiving a normal-temperature signal.
Further, the second switch comprises a triode Q2, a collector of the triode Q2 is connected with the first switch, a base of the triode Q2 is connected with a high-level control signal for controlling the load to work, and an emitter of the triode Q2 is grounded.
Further, the first switch comprises a transistor Q1, an emitter of the transistor Q1 is connected with the control power supply, a collector of the transistor Q1 is connected with the switching unit, and a base of the transistor Q2 is connected with the collector of the transistor Q2.
Further, the switching unit is a relay.
The utility model also provides an electric appliance, and the electric appliance adopts the over-temperature protection circuit.
Compared with the prior art, the utility model has at least the following beneficial effects:
1. through the setting of the over-temperature protection circuit, when the temperature of the load is higher than a preset over-temperature protection point, the load is timely disconnected, and over-temperature protection is achieved.
2. Whether the over-temperature protection point is over-temperature is detected in a mode that the thermistor is connected with a resistor in series, the over-temperature protection point can be adjusted by changing the resistance value of the resistor connected with the thermistor in series, so that the over-temperature protection point of the over-temperature protection circuit can be adjusted according to the actual electric appliance requirement, and the applicability is stronger.
3. Switching control work is carried out through thermistor and triode complex mode, can break off the load when the load temperature is higher than the excess temperature protection point, plays the excess temperature protection, can also switch on the load again when the load temperature resumes normally, makes the electrical apparatus operation, has avoided the problem that needs the maintenance behind the excess temperature protection, has reduced cost of maintenance to a certain extent.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.
Fig. 1 is a schematic circuit diagram according to an embodiment of the present invention.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the utility model and are not intended to limit the utility model.
Thus, a feature indicated in this specification will serve to explain one of the features of one embodiment of the utility model, and does not imply that every embodiment of the utility model must have the stated feature. Further, it should be noted that this specification describes many features. Although some features may be combined to show a possible system design, these features may also be used in other combinations not explicitly described. Thus, the combinations illustrated are not intended to be limiting unless otherwise specified.
The principles and construction of the present invention will be described in detail below with reference to the drawings and examples.
Along with the increase of electronic products, the safety of electrical appliances is more and more important, but like heating type loads such as auxiliary heating nature, the condition takes place occasionally because of improper use takes place the excess temperature, easily damages the load, and current excess temperature protection has the mode through the series connection fuse, and when this mode is when load temperature resumes normal back, because fuse fusing load can not the rerun, can rerun after needing to overhaul, has increased subsequent maintenance time and cost. The utility model provides an over-temperature signal for the triode in a mode that the thermistor is connected with a resistor in series, so that the triode can be switched on when the load is over-temperature, and further has over-temperature protection, and is switched off at normal temperature to resume working.
Specifically, the over-temperature protection circuit provided by the utility model comprises a load, a working power supply for supplying power to the load, a switching unit for switching the on-off state of the load and the working power supply, a control power supply for supplying power to the switching unit, and a protection circuit arranged between the control power supply and the switching unit. The protection circuit is used for performing over-temperature protection, and can adjust the conduction state of the switching unit by controlling the on-off state of the protection circuit because the protection circuit is connected between the control power supply and the switching unit, wherein when the temperature of the load is higher than a preset over-temperature protection point, the protection circuit cuts off the switching unit, otherwise, when the temperature of the load is lower than the preset over-temperature protection point, the protection circuit conducts the switching unit, and further controls the running state of the load through the conduction state of the switching unit.
Preferably, the switching unit adopts the relay, and the relay is including work circuit part and switch part, and work circuit part is connected with control power, switch part and load series connection, and when the relay was electrified, the electro-magnet in the relay can attract the switch part, makes it closed to switch on the load, make load work, otherwise, when the relay outage, the electro-magnet in the relay can not continue to attract the switch, and the switch part can break off, thereby breaks off the load, plays the guard action. According to the utility model, the protection circuit is arranged between the relay and the control power supply, and when the temperature of the load reaches an over-temperature protection point, the power supply of the relay can be cut off in time, so that the switch part of the relay is disconnected, and the over-temperature protection is realized.
Compared with other switching devices, the control logic of the relay is simple, the cost is relatively low, in other embodiments of the utility model, the same control effect can be achieved by adopting other control elements, and the load can work only by meeting the condition that the change-over switch is closed when being electrified; and when the power is cut off, so that the load is cut off to play a protection role.
Further, the protection circuit comprises a first change-over switch connected between the switching unit and the control power supply in series and a second change-over switch for controlling the on-off state of the first change-over switch. The first switch is connected in series between the control power supply and the switching unit, and when the first switch is disconnected, the control power supply and the switching unit are equivalent to open circuit, so that the control power supply is disconnected to supply power to the switching unit, the switching unit is disconnected, and the load is switched off.
The second change-over switch is used for controlling the on-off state of the first change-over switch, and when the second change-over switch is switched on, the second change-over switch can switch on the first change-over switch, so that the switching unit is switched on and the load is controlled to work; on the contrary, when the second switching unit is disconnected, the second switching unit can disconnect the first switch, so that the switching unit controls the load to be switched off, and the protection effect is achieved.
Further, in order to realize the over-temperature protection function of the utility model, the protection circuit is also provided with an over-temperature detection unit and an over-temperature switching unit connected with the over-temperature detection unit and the second switch, wherein the over-temperature detection unit is used for detecting whether the temperature of the load reaches an over-temperature protection point or not, and when the temperature of the load reaches the over-temperature protection point, an over-temperature signal is sent to the over-temperature switching unit, so that the over-temperature switching unit turns off the second switch, further turns off the load, and plays a role in over-temperature protection. Meanwhile, when the temperature of the load does not reach the over-temperature protection point, the over-temperature detection unit sends a normal-temperature signal to the over-temperature switching unit, so that the over-temperature switching unit conducts the second switch, and the load works.
The over-temperature detection unit can be equipment for detecting temperature, such as a temperature detector and the like, and can send an over-temperature signal to the over-temperature switching unit when the over-temperature detection unit is over-temperature, and the over-temperature switching unit adopts a corresponding switching device, so that the second switching switch is switched off when the over-temperature fault is received, and the load is disconnected to achieve over-temperature protection.
Referring to fig. 1, in a preferred embodiment of the present invention, the over-temperature detecting unit employs a thermistor RX and a resistor R1 connected in series between the control power supply and the ground, the thermistor has a characteristic that the resistance changes with the change of the temperature, since the thermistor RX is connected in series with the resistor R1, when the resistance of the thermistor RX changes, the divided voltage of the thermistor RX changes, and the over-temperature switching unit is connected between the thermistor RX and the resistor R1, receives the voltage between the thermistor RX and the resistor R1, and uses the voltage reaching the over-temperature protection as an over-temperature signal for controlling the on-off of the second switch. If the temperature at the over-temperature is 70 ℃, the resistance of the thermistor RX is a at 70 ℃, the voltage received by the over-temperature switching unit is a at this time through the voltage division of the thermistor RX, that is, a is an over-temperature signal, the temperature at this time is 70 ℃ which is an over-temperature protection point set by the over-temperature protection circuit, and when the temperature in the load is greater than or equal to 70 ℃, it is determined that the load is over-temperature, and the load is turned off, thereby playing a role in protection. When the temperature of the load does not reach 70 ℃, the voltage received by the over-temperature switching unit is B, which is used as a normal-temperature signal, and under the condition, the over-temperature switching unit is not enough to be conducted, and the load works normally.
It should be noted that in this embodiment, by adopting a manner that the thermistor RX is connected in series with the resistor R1, the over-temperature protection point is adjustable, the over-temperature protection point is the set protection temperature, and when the over-temperature protection point is higher than the over-temperature protection point, it is determined that the load has an over-temperature problem. In this embodiment, the size of the over-temperature protection point can be adjusted by changing the size of the resistor R1, for example, when the resistance value of the resistor R1 is n1, the over-temperature signal is voltage a, when the resistance value of the thermistor RX reaches m1, the divided voltage between the thermistor RX and the resistor R1 reaches a, the temperature of the thermistor RX is Q1, that is, the over-temperature protection point is Q1 temperature; when the magnitude of the resistor R1 is changed to n2, and the over-temperature switching unit receives the voltage a due to the change of the magnitude of the resistor R1, the resistance value of the thermistor RX is changed to m2, the corresponding temperature is also different from that before, and the temperature of the thermistor RX is Q2, that is, the over-temperature protection point is Q2 temperature. Through the adjustment of the resistor R1, the size of the over-temperature protection point can be adjusted in a self-adaptive manner according to the requirements of different electrical appliances, so that the applicability of the utility model is better. After the voltage of the over-temperature signal is determined, the temperature and the change rule of the resistance are obtained only according to the type of the thermistor RX, and then the specific over-temperature protection point can be determined by setting the size of the resistor R1 according to the circuit voltage division principle.
Furthermore, the over-temperature protection unit comprises a first over-temperature change-over switch connected with the over-temperature detection unit and a second over-temperature change-over switch connected with the first over-temperature change-over switch and the second over-temperature change-over switch, the setting mode is that the first over-temperature change-over switch is switched on when receiving an over-temperature signal, the second over-temperature change-over switch is switched on, and the second change-over switch can be switched off after being switched on to lower the signal output to the second change-over switch, so that the load is disconnected.
Referring to fig. 1, in particular, the over-temperature switch includes a transistor Q3 and a transistor Q4, wherein an emitter of the transistor Q3 is connected to a reference voltage, a base is connected between the thermistor RX and the resistor R1 for receiving the over-temperature signal, a collector of the transistor Q3 is connected to a base of the transistor Q4, a collector of the transistor Q4 is connected to the second switch, and an emitter is grounded.
Through the arrangement, when the load is over-temperature, the voltage between the thermistor RX and the resistor R1 reaches a, and the thermistor RX and the resistor R1 output an over-temperature signal to the base of the transistor Q3, so that the transistor Q3 is controlled to be switched on, and the transistor Q4 is switched on, so that the level at the second switch is pulled down, the load is switched off, and the over-temperature protection function is achieved. In this embodiment, adopt triode Q3 and triode Q4 control second change over switch, because the conduction characteristic of triode, as long as voltage reaches and can switch on, after setting through the triode, when the load is too warm, can break off the load and play the guard action, simultaneously when the load disconnection back, the temperature in the load reduces, thermistor RX's partial pressure also changes thereupon, when the temperature in the load is less than the overtemperature protection point, thermistor RX's partial pressure is not enough to switch on triode Q3, triode Q3 can be shut off again this moment, make triode Q4 turn-off, and then make triode Q2 switch on again, the load resumes work. If other control modes are adopted, such as a fuse fusing mode, when the temperature reaches an over-temperature point for the first time, the fuse fuses, and then the load is turned off, and when the temperature is recovered to be normal, the fuse cannot be conducted again, so that the fuse cannot recover the working state again, and the fuse can recover the work again after being overhauled.
In the utility model, the thermistor RX adopts a PTC resistor (positive temperature coefficient resistor), the resistance value of the resistor increases with the increase of temperature, that is, when the temperature increases, the divided voltage of the thermistor RX becomes high, the voltage output to the base of the transistor Q3 decreases, and when the voltage is lower than the voltage of an emitter, the transistor Q3 is turned on; when the temperature is reduced, the resistance value of the thermistor RX is reduced, the partial voltage of the thermistor RX is reduced, the voltage output to the base electrode of the triode Q3 is increased, and when the voltage is higher than the voltage of the emitting electrode, the triode Q3 is turned off.
It should be noted that, when the temperature of the load reaches the over-temperature protection point, the voltage at the base of the transistor Q3 is a, and the over-temperature signal is only smaller than the voltage signal of a, because the resistance of the PTC resistor increases with the temperature, that is, the higher the temperature, the lower the voltage output to the base of the transistor Q3, that is, when the temperature of the load is greater than or equal to the over-temperature protection point, the voltage output to the base of the transistor Q3 is all smaller than or equal to a, and this part of voltage is used as the over-temperature signal, and can be used to turn on the transistor Q3, and further turn off the load. Accordingly, the normal temperature signal is a voltage signal higher than the voltage a, and the voltage is capable of turning off the transistor Q3, thereby turning on the load. The thermistor RX is arranged at a load, so that the thermistor RX can better sense temperature change and has a better control effect.
Further, a reference voltage is provided by a resistor R2 and a resistor R3, the resistor R2 and the resistor R3 are connected in series between a control power supply and an emitter of the triode Q3, and a reference voltage is provided for the emitter of the triode Q3, it should be noted that the conduction condition of the triode Q3 is that the triode Q3 is conducted when the voltage is lower than the reference voltage, and the change rule of the thermistor is that the resistor increases with the increase of the temperature, and the resistance value of the thermistor gradually increases with the increase of the temperature of the load, so that the voltage output to the base of the triode Q3 decreases, and the triode Q3 is further conducted, in the present invention, the way of changing the over-temperature protection point can also be realized by changing the sizes of the resistor R2 and the resistor R3, the reference voltage changes by changing the sizes of the resistor R2 and the resistor R3, that is the voltage required when the triode Q3 is conducted, and the resistance value of the thermistor RX is different when the triode Q3 is conducted under the condition that the resistance value of the resistor R1 is unchanged, that is, the temperature when the over-temperature signal is sent is different, the corresponding over-temperature protection point is also changed correspondingly, and the specific setting mode is designed according to the thermistor and the circuit voltage division principle, which is not described herein. It should be noted that, although the size of the over-temperature protection point can be changed by changing the resistance of the resistor R1, the reference voltage needs to be considered when the over-temperature protection point is adjusted by changing the resistance of the resistor R1, the voltage output to the base of the transistor Q3 needs to be lower than the reference voltage when the over-temperature protection point is reached, the setting of the resistor R1 does not need to be considered when the reference voltage is adjusted by changing the resistor R2 and the resistor R3, and the way of setting the over-temperature protection point is simpler.
Further, referring to fig. 1, the second switch is a triode Q2, a collector of the triode Q2 is connected to the first switch, a base is connected to a high level control signal for controlling the load to work, an emitter is grounded, and a resistor is connected in series to the base of the triode Q2 and then connected to a level signal for dividing voltage and limiting current. When the transistor Q4 is turned on, the high level control signal is directed to ground through the transistor Q4, so that the voltage at the base of the transistor Q2 is 0 and the transistor Q2 is turned off, thereby turning off the first switch.
The first switch is a transistor Q1, the emitter and the collector of the transistor Q1 are connected to the control power supply, the collector is connected with the switching unit, and the base is connected with the collector of the transistor Q2. As is apparent from the arrangement of the transistor Q1 in fig. 1, when the transistor Q1 is turned off, which is equivalent to an open circuit, the control unit cannot provide voltage to the switching unit, and the switching unit is powered off, which controls the load to be turned off. Through the setting of triode Q1 for the switching unit's break-make can be controlled to the excess temperature protection circuit, and then the state of control load.
Under the idea of the utility model, the triode can be replaced by a switching tube device such as an MOS tube, the same technical effect can be achieved, and compared with the MOS tube, the triode has the advantages of lower cost, simpler connection and higher practicability.
The control flow of the utility model is as follows:
when the electric appliance works, a high-level control signal is sent to the base of the triode Q2, the triode Q2 is conducted, the triode Q1 is further conducted, the power supply is controlled to supply power to the switching unit, and the load works normally;
when the load is over-temperature, because the temperature in the load reaches an over-temperature protection point, the resistance value of the thermistor RX is increased, so that the voltage output to the base electrode of the triode Q3 is a first reference voltage, the triode Q3 is conducted and enters over-temperature protection, the triode Q4 is conducted at the moment, a high-level control signal is directly conducted to the ground through the triode Q4, the triode Q2 is turned off, the triode Q1 is turned off, the control power supply cannot supply power to the switching unit, the load is disconnected and works, and the over-temperature protection is achieved;
after the over-temperature protection, the temperature in the load is gradually reduced, when the temperature is lower than an over-temperature protection point, the resistance value of the thermistor RX is reduced along with the reduction of the temperature, the voltage output to the base electrode of the triode Q3 is increased, the triode Q3 is cut off again, the triode Q4 is cut off, as the triode Q4 is cut off, a high-level control signal is normally input to the base electrode of the triode Q2, the triode Q2 is conducted, the triode Q1 is further conducted, the control power supply starts to supply power to the switching unit, the switching unit conducts the load again, and the circuit load is enabled to recover working.
The utility model also provides an electric appliance which comprises a load and an over-temperature protection circuit connected with the load, wherein the over-temperature protection circuit adopts the over-temperature protection circuit.
Compared with the prior art, the over-temperature protection circuit can timely turn off the load when the load is over-temperature, so that the load stops working, and the electric appliance is prevented from being damaged. Meanwhile, the over-temperature protection point can be adjusted by adjusting the resistor R1 or the resistor R2 and the resistor R3, so that the over-temperature protection device can be suitable for different electrical appliance requirements and is better in applicability. Furthermore, the over-temperature protection circuit can not only turn off the load to achieve over-temperature protection when the temperature is over-temperature, but also turn off the triode Q3 and the triode Q4 when the temperature is reduced, and further turn on the triode Q2 and the triode Q1, so that the switching unit is electrified again, the load is recovered to work, the circuit has a self-recovery function, the problem that the circuit can be reused after being overhauled after a fault is avoided, and the maintenance cost is reduced.
The above examples are intended only to illustrate specific embodiments of the present invention. It should be noted that, for a person skilled in the art, several modifications and variations can be made without departing from the inventive concept, and these modifications and variations shall fall within the protective scope of the present invention.
Claims (10)
1. An over-temperature protection circuit comprising: the load, give the working power supply of load power supply, switch the load with the switching unit of working power supply on-off state and give the control power supply of switching unit power supply, its characterized in that still includes: the protection circuit is arranged between the switching unit and the control power supply;
when the temperature of the load is higher than a preset over-temperature protection point, the protection circuit cuts off the switching unit to enable the switching unit to cut off the load;
when the temperature of the load is lower than a preset over-temperature protection point, the protection circuit conducts the switching unit to enable the switching unit to start the load.
2. The over-temperature protection circuit according to claim 1, wherein the protection circuit includes a first switch connected in series between the control power supply and the switching unit, and a second switch controlling an on-off state of the first switch;
when the second switch is switched on, the first switch is switched on, and the switching unit is switched on
An element, thereby turning on the load;
when the second switch is turned off, the first switch is turned off, and the switching unit is cut off, so that the load is turned off.
3. The over-temperature protection circuit according to claim 2, wherein the protection circuit further comprises:
an over-temperature detection unit: monitoring whether the temperature of the load is higher than the over-temperature protection point;
an over-temperature switching unit: is connected with the over-temperature detection unit and the second change-over switch when the over-temperature detection unit is over-temperature
When the detection unit detects that the temperature of the load is higher than the over-temperature protection point, the second change-over switch is switched off; and when the over-temperature detection unit detects that the temperature of the load is lower than the over-temperature protection point, the second change-over switch is switched on.
4. The over-temperature protection circuit according to claim 3, wherein the over-temperature switching unit includes a first over-temperature switch connected to the over-temperature detecting unit, and a second over-temperature switch connecting the first over-temperature switch and the second over-temperature switch;
when the over-temperature detection unit detects that the temperature of the load is higher than the over-temperature protection point, the second step
An over-temperature change-over switch is switched on, so that the second over-temperature change-over switch is switched on, and the second change-over switch is switched off;
when the over-temperature detection unit detects that the temperature of the load is lower than the over-temperature protection point, the first over-temperature change-over switch is switched off, and then the second over-temperature change-over switch is switched off, so that the second change-over switch is switched on.
5. The over-temperature protection circuit according to claim 4, wherein the over-temperature detection unit comprises a thermistor RX and a resistor R1 connected in series between the control power supply and ground, the over-temperature switching unit is connected between the thermistor RX and the resistor R1;
when the temperature of the load reaches the over-temperature protection point, the resistance value of the thermistor RX reaches a predetermined value
Setting a resistance value, wherein the over-temperature detection unit sends an over-temperature signal so as to conduct the first over-temperature change-over switch;
when the temperature of the load is lower than the over-temperature protection point, the resistance value of the thermistor RX is lower than a preset resistance value, and the over-temperature detection unit sends a normal-temperature signal so as to turn off the first over-temperature change-over switch.
6. The over-temperature protection circuit of claim 3, wherein the over-temperature switching unit comprises a transistor Q3 and a transistor Q4;
the emitter of the triode Q3 is connected with a reference voltage, and the base is connected with the over-temperature detection unit and the over-temperature detection unit
The electrode is connected to the base electrode of a triode Q4, the collector electrode of the triode Q4 is connected to the second switching switch, and the emitter electrode of the triode Q4 is grounded;
and the base electrode of the triode Q3 is conducted when receiving an over-temperature signal and is switched off when receiving a normal-temperature signal.
7. The over-temperature protection circuit of claim 6, wherein the second switch comprises a transistor Q2, a collector of the transistor Q2 is connected to the first switch, a base of the transistor is connected to a high-level control signal for controlling the operation of the load, and an emitter of the transistor is grounded.
8. The over-temperature protection circuit of claim 7, wherein the first switch comprises a transistor Q1, an emitter of the transistor Q1 is connected to the control power supply, a collector of the transistor Q1 is connected to the switching unit, and a base of the transistor Q2 is connected to the collector of the transistor Q2.
9. The over-temperature protection circuit according to claim 1, wherein the switching unit is a relay.
10. An electrical appliance, characterized in that the electrical appliance adopts an over-temperature protection circuit as claimed in any one of claims 1 to 9.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202121526340.XU CN215817500U (en) | 2021-07-06 | 2021-07-06 | Over-temperature protection circuit and electric appliance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202121526340.XU CN215817500U (en) | 2021-07-06 | 2021-07-06 | Over-temperature protection circuit and electric appliance |
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| Publication Number | Publication Date |
|---|---|
| CN215817500U true CN215817500U (en) | 2022-02-11 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202121526340.XU Active CN215817500U (en) | 2021-07-06 | 2021-07-06 | Over-temperature protection circuit and electric appliance |
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| CN (1) | CN215817500U (en) |
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