Over-temperature protection circuit and switching power supply

Abstract

The utility model provides an over-temperature protection circuit and a switching power supply. The over-temperature protection circuit comprises a compensation module and an over-temperature protection module. The input end of the compensation module is connected with a rectifying circuit of the switching power supply; the input end of the over-temperature protection module is connected with the output end of the compensation module, and the output end of the over-temperature protection module is connected with a control circuit of the switching power supply; wherein the compensation module is used for providing over-temperature compensation voltage for the over-temperature protection module. The over-temperature protection point does not change along with the change of the input voltage, so that the switch power supply is prevented from being burnt down.

Description

Technical Field

[0001] The utility model relates to the technical field of switching power supplies, in particular to an over-temperature protection circuit and a switching power supply. Background Art

[0002] A switching power supply is usually equipped with an over-temperature protection circuit to protect the switching power supply from over-temperature. Depending on the application scenarios, the input voltage span of the switching power supply is usually large, causing the over-temperature protection point to change with the input voltage. For example, when the input voltage is low, the over-temperature protection point is low, and when the input voltage is high, the over-temperature protection point is high. A high over-temperature protection point can easily cause the switching power supply to burn out. Utility Model Content

[0003] The utility model provides an over-temperature protection circuit and a switching power supply, aiming to solve the problem that the over-temperature protection point of the current switching power supply changes with the change of input voltage.

[0004] In the first aspect, the utility model provides an over-temperature protection circuit, which includes a compensation module and an over-temperature protection module; the input end of the compensation module is connected to the rectifier circuit of the switching power supply; the input end of the over-temperature protection module is connected to the output end of the compensation module, and the output end of the over-temperature protection module is connected to the control circuit of the switching power supply; wherein the compensation module is used to provide an over-temperature compensation voltage for the over-temperature protection module.

[0005] Furthermore, the compensation module includes a compensation voltage setting circuit and a first switching circuit; the input end of the compensation voltage setting circuit is respectively connected to the rectifier circuit and the power supply end, the output end of the compensation voltage setting circuit is connected to the input end of the first switching circuit, and the output end of the first switching circuit is connected to the over-temperature protection module.

[0006] Furthermore, the compensation voltage setting circuit includes a first resistor, a second resistor and a third resistor; one end of the first resistor is connected to the rectifier circuit, the other end of the first resistor is respectively connected to one end of the second resistor and the first switch circuit, the other end of the second resistor is connected to the rectifier circuit, one end of the third resistor is connected to the power supply end, and the other end of the third resistor is connected to the first switch circuit.

[0007] Furthermore, the first switch circuit includes a first switch tube, a controlled end of the first switch tube is connected to the first resistor, a first electrode of the first switch tube is connected to the third resistor, and a second electrode of the first switch tube is connected to the over-temperature protection module.

[0008] Furthermore, the compensation voltage setting circuit also includes a first capacitor, one end of the first capacitor is connected to the first resistor, and the other end of the first capacitor is connected to the rectifier circuit.

[0009] Furthermore, the over-temperature protection module includes a thermistor, a first diode and a second switching circuit; one end of the thermistor and one end of the second switching circuit are both connected to the first switching circuit, the other end of the thermistor is connected to the second switching circuit, the other end of the second switching circuit is connected to the positive electrode of the first diode, and the negative electrode of the first diode is connected to the control circuit.

[0010] Furthermore, the second switching circuit includes a second switching tube and a third switching tube; the controlled end and the first pole of the second switching tube are both connected to the first switching circuit, and the second pole of the second switching tube is connected to the positive pole of the first diode; the controlled end of the third switching tube is connected to the thermistor, the first pole of the third switching tube is connected to the first switching circuit, and the second pole of the third switching tube is grounded.

[0011] Furthermore, the second switch circuit also includes a fourth resistor, a fifth resistor, a sixth resistor and a seventh resistor; one end of the fourth resistor and one end of the fifth resistor are both connected to the first switch circuit, the other end of the fourth resistor is respectively connected to one end of the sixth resistor and the controlled end of the second switch tube, the other end of the fifth resistor is connected to the first pole of the second switch tube, the other end of the sixth resistor is connected to the first pole of the third switch tube, one end of the seventh resistor is connected to the second pole of the second switch tube, and the other end of the seventh resistor is grounded.

[0012] Furthermore, the second switching circuit also includes an eighth resistor, a ninth resistor and a second capacitor; one end of the eighth resistor is connected to the first switching circuit, the other end of the eighth resistor is connected to the thermistor, one end of the ninth resistor and one end of the second capacitor are both connected to the thermistor, and the other end of the ninth resistor and the other end of the second capacitor are both grounded.

[0013] In a second aspect, the utility model further provides a switching power supply, which includes a rectifier circuit, a control circuit and any of the over-temperature protection circuits described above.

[0014] The switching power supply disclosed in the utility model includes a rectifier circuit, a control circuit and an over-temperature protection circuit. The over-temperature protection circuit includes a compensation module and an over-temperature protection module. The compensation module is connected to the rectifier circuit and the over-temperature protection module, and is used to increase the compensation voltage for the over-temperature protection module to adjust the input voltage of the over-temperature protection module, so as to avoid the over-temperature protection point of the over-temperature protection module changing with the change of the input voltage of the rectifier circuit, thereby avoiding burning of the switching power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the utility model, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 It is a block diagram of an over-temperature protection circuit provided by an embodiment of the utility model;

[0017] Figure 2 The utility model provides an over-temperature protection circuit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0019] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, operations, elements, components and / or groups thereof.

[0020] It should also be understood that the terms used in this utility model specification are only for the purpose of describing specific embodiments and are not intended to limit the utility model. As used in the utility model specification and the appended claims, the singular forms of "a", "an" and "the" are intended to include plural forms unless the context clearly indicates otherwise. It should also be further understood that the term "and / or" used in the utility model specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0021] In addition, the directional terms mentioned in the present invention, such as "upper", "lower", "front", "back", "left", "right", "inner", "outer", "side", etc., are only for reference to the directions of the attached drawings and the use status of the product. Therefore, the directional terms used are used to illustrate and understand the present invention, but not to limit the present invention. In addition, in the drawings, structures with similar or identical structures are represented by the same reference numerals.

[0022] See also Figure 1 to Figure 2 , Figure 1 1 is a block diagram of an over-temperature protection circuit 100 provided in one embodiment of the present utility model; Figure 2 FIG. 1 is a circuit diagram of an over-temperature protection circuit 100 provided in an embodiment of the present invention. Figure 1 As shown, the over-temperature protection circuit 100 includes a compensation module 10 and an over-temperature protection module 20; the input end of the compensation module 10 is connected to the rectifier circuit 200 of the switching power supply; the input end of the over-temperature protection module 20 is connected to the output end of the compensation module 10, and the output end of the over-temperature protection module 20 is connected to the control circuit 300 of the switching power supply; wherein the compensation module 10 is used to provide an over-temperature compensation voltage for the over-temperature protection module 20.

[0023] Specifically, the switching power supply includes a rectifier circuit 200, a control circuit 300 and an over-temperature protection circuit 100. The over-temperature protection circuit 100 includes a compensation module 10 and an over-temperature protection module 20. The compensation module 10 is connected to the rectifier circuit 200. The rectifier circuit 200 may include a rectifier bridge for rectifying the input alternating current and outputting the rectified voltage to the compensation module 10. The output end of the compensation module 10 is connected to the over-temperature protection module 20 to provide a compensation voltage to prevent the over-temperature protection point from changing with the input voltage.

[0024] The output end of the over-temperature protection module 20 is connected to the control circuit 300 to provide over-temperature protection for the switching power supply. The control circuit 300 determines whether to perform over-temperature protection according to the output signal of the over-temperature protection module 20 to prevent the switching power supply from burning.

[0025] For example, if the AC input voltage is 90V, the input voltage is relatively low, the voltage compensated by the compensation module 10 is relatively low, and the over-temperature protection module 20 requires a relatively high temperature to trigger the over-temperature protection. If the AC input voltage is 264V, the input voltage is relatively high, the voltage compensated by the compensation module 10 is relatively high, and the over-temperature protection module 20 can trigger the over-temperature protection at a relatively low temperature.

[0026] As a further embodiment, the compensation module 10 includes a compensation voltage setting circuit 11 and a first switching circuit 12; the input end of the compensation voltage setting circuit 11 is respectively connected to the rectifier circuit 200 and the power supply end, the output end of the compensation voltage setting circuit 11 is connected to the input end of the first switching circuit 12, and the output end of the first switching circuit 12 is connected to the over-temperature protection module 20.

[0027] Among them, the compensation voltage setting circuit 11 is used to adjust the compensation voltage. According to different switching power supplies, the compensation voltage can be adjusted by the compensation voltage setting circuit 11. The compensation voltage setting circuit 11 is connected to the first switching circuit 12, and the first switching circuit 12 is connected to the over-temperature compensation module 10.

[0028] As a further embodiment, the compensation voltage setting circuit 11 includes a first resistor R1, a second resistor R2 and a third resistor R3; one end of the first resistor R1 is connected to the rectifier circuit 200, the other end of the first resistor R1 is respectively connected to one end of the second resistor R2 and the first switch circuit 12, the other end of the second resistor R2 is connected to the rectifier circuit 200, one end of the third resistor R3 is connected to the power supply end, and the other end of the third resistor R3 is connected to the first switch circuit 12. Further, the first switch circuit 12 includes a first switch tube Q1, the controlled end of the first switch tube Q1 is connected to the first resistor R1, the first electrode of the first switch tube Q1 is connected to the third resistor R3, and the second electrode of the first switch tube Q1 is connected to the over-temperature protection module 20. Further, the compensation voltage setting circuit 11 also includes a first capacitor C1, one end of the first capacitor C1 is connected to the first resistor R1, and the other end of the first capacitor C1 is connected to the rectifier circuit 200.

[0029] The compensation voltage setting circuit 11 includes a first resistor R1, a second resistor R2 and a third resistor R3, wherein the second resistor R2 and the third resistor R3 can be used to adjust the compensation voltage, and the compensation voltage can be adjusted by changing the resistance values ​​of the second resistor R2 and the third resistor R3. The third resistor R3 is connected to the power supply end and the first switch tube Q1 respectively. When the input voltage is low, the voltage of the controlled end of the first switch tube Q1 is low, and the voltage provided by the power supply end is low, so that the over-temperature protection module 20 requires a higher temperature to trigger the over-temperature protection. When the input voltage is high, the voltage of the controlled end of the first switch tube Q1 is high, and the voltage provided by the power supply end is high, so that the over-temperature protection module 20 can trigger the over-temperature protection at a lower temperature.

[0030] The first switch tube Q1 may be a triode, and the base of the first switch tube Q1 is connected to the first resistor R1 , the collector of the first switch tube Q1 is connected to the third resistor R3 , and the emitter of the first switch tube Q1 is connected to the over-temperature protection module 20 .

[0031] As a further embodiment, the over-temperature protection module 20 includes a thermistor NTC, a first diode D1 and a second switch circuit 21; one end of the thermistor NTC and one end of the second switch circuit 21 are both connected to the first switch circuit 12, the other end of the thermistor NTC is connected to the second switch circuit 21, the other end of the second switch circuit 21 is connected to the positive electrode of the first diode D1, and the negative electrode of the first diode D1 is connected to the control circuit 300. Further, the second switch circuit 21 includes a second switch tube Q2 and a third switch tube Q3; the controlled end and the first electrode of the second switch tube Q2 are both connected to the first switch circuit 12, the second electrode of the second switch tube Q2 is connected to the positive electrode of the first diode D1; the controlled end of the third switch tube Q3 is connected to the thermistor NTC, the first electrode of the third switch tube Q3 is connected to the first switch circuit 12, and the second electrode of the third switch tube Q3 is grounded. Further, the second switch circuit 21 further includes a fourth resistor R4, a fifth resistor R5, a sixth resistor R6 and a seventh resistor R7; one end of the fourth resistor R4 and one end of the fifth resistor R5 are both connected to the first switch circuit 12, the other end of the fourth resistor R4 is respectively connected to one end of the sixth resistor R6 and the controlled end of the second switch tube Q2, the other end of the fifth resistor R5 is connected to the first electrode of the second switch tube Q2, the other end of the sixth resistor R6 is connected to the first electrode of the third switch tube Q3, one end of the seventh resistor R7 is connected to the second electrode of the second switch tube Q2, and the other end of the seventh resistor R7 is grounded. Further, the second switch circuit 21 further includes an eighth resistor R8, a ninth resistor R9 and a second capacitor C2; one end of the eighth resistor R8 is connected to the first switch circuit 12, the other end of the eighth resistor R8 is connected to the thermistor NTC, one end of the ninth resistor R9 and one end of the second capacitor C2 are both connected to the thermistor NTC, and the other end of the ninth resistor R9 and the other end of the second capacitor C2 are both grounded.

[0032] Among them, when the input voltage is low, the thermistor NTC needs a higher temperature to turn on the third switch tube Q3, and then turn on the first diode D1 to trigger the over-temperature protection. When the input voltage is high, the thermistor NTC can turn on the third switch tube Q3 at a lower temperature, and then turn on the first diode D1 to trigger the over-temperature protection, thereby avoiding the over-temperature protection point changing with the change of the input voltage.

[0033] The utility model also provides a switching power supply, which includes a rectifier circuit 200, a control circuit 300 and an over-temperature protection circuit 100 as described in any one of the above embodiments; the over-temperature protection circuit 100 includes a compensation module 10 and an over-temperature protection module 20; the input end of the compensation module 10 is connected to the rectifier circuit 200 of the switching power supply; the input end of the over-temperature protection module 20 is connected to the output end of the compensation module 10, and the output end of the over-temperature protection module 20 is connected to the control circuit 300 of the switching power supply; wherein the compensation module 10 is used to provide an over-temperature compensation voltage for the over-temperature protection module 20.

[0034] Specifically, the switching power supply includes a rectifier circuit 200, a control circuit 300 and an over-temperature protection circuit 100. The over-temperature protection circuit 100 includes a compensation module 10 and an over-temperature protection module 20. The compensation module 10 is connected to the rectifier circuit 200. The rectifier circuit 200 may include a rectifier bridge for rectifying the input alternating current and outputting the rectified voltage to the compensation module 10. The output end of the compensation module 10 is connected to the over-temperature protection module 20 to provide a compensation voltage to prevent the over-temperature protection point from changing with the input voltage.

[0035] The output end of the over-temperature protection module 20 is connected to the control circuit 300 to provide over-temperature protection for the switching power supply. The control circuit 300 determines whether to perform over-temperature protection according to the output signal of the over-temperature protection module 20 to prevent the switching power supply from burning.

[0036] For example, if the AC input voltage is 90V, the input voltage is relatively low, the voltage compensated by the compensation module 10 is relatively low, and the over-temperature protection module 20 requires a relatively high temperature to trigger the over-temperature protection. If the AC input voltage is 264V, the input voltage is relatively high, the voltage compensated by the compensation module 10 is relatively high, and the over-temperature protection module 20 can trigger the over-temperature protection at a relatively low temperature.

[0037] The over-temperature protection circuit and the switching power supply disclosed by the utility model can compensate the input voltage of the over-temperature protection circuit by providing a compensation module, so as to avoid the over-temperature protection point changing with the change of the input voltage.

[0038] The above is only a specific implementation of the utility model, but the protection scope of the utility model is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the utility model, and these modifications or replacements should be included in the protection scope of the utility model. Therefore, the protection scope of the utility model should be based on the protection scope of the claims.

Claims

1. An over-temperature protection circuit, characterized in that: Applied to switching power supplies, including: A compensation module, wherein an input end of the compensation module is connected to a rectifier circuit of the switching power supply; An over-temperature protection module, wherein an input end of the over-temperature protection module is connected to an output end of the compensation module, and an output end of the over-temperature protection module is connected to a control circuit of the switching power supply; Wherein, the compensation module is used to provide an over-temperature compensation voltage for the over-temperature protection module.

2. The over-temperature protection circuit according to claim 1, characterized in that: The compensation module includes a compensation voltage setting circuit and a first switch circuit; The input end of the compensation voltage setting circuit is connected to the rectifier circuit and the power supply end respectively, the output end of the compensation voltage setting circuit is connected to the input end of the first switch circuit, and the output end of the first switch circuit is connected to the over-temperature protection module.

3. The over-temperature protection circuit according to claim 2, characterized in that: The compensation voltage setting circuit includes a first resistor, a second resistor and a third resistor; One end of the first resistor is connected to the rectifier circuit, the other end of the first resistor is respectively connected to one end of the second resistor and the first switch circuit, the other end of the second resistor is connected to the rectifier circuit, one end of the third resistor is connected to the power supply end, and the other end of the third resistor is connected to the first switch circuit.

4. The over-temperature protection circuit according to claim 3, characterized in that: The first switch circuit includes a first switch tube, a controlled end of the first switch tube is connected to the first resistor, a first electrode of the first switch tube is connected to the third resistor, and a second electrode of the first switch tube is connected to the over-temperature protection module.

5. The over-temperature protection circuit according to claim 3, characterized in that: The compensation voltage setting circuit further includes a first capacitor, one end of the first capacitor is connected to the first resistor, and the other end of the first capacitor is connected to the rectifier circuit.

6. The over-temperature protection circuit according to claim 2, characterized in that: The over-temperature protection module includes a thermistor, a first diode and a second switch circuit; One end of the thermistor and one end of the second switch circuit are both connected to the first switch circuit, the other end of the thermistor is connected to the second switch circuit, the other end of the second switch circuit is connected to the anode of the first diode, and the cathode of the first diode is connected to the control circuit.

7. The over-temperature protection circuit according to claim 6, characterized in that: The second switch circuit includes a second switch tube and a third switch tube; The controlled end and the first electrode of the second switch tube are both connected to the first switch circuit, and the second electrode of the second switch tube is connected to the positive electrode of the first diode; The controlled end of the third switch tube is connected to the thermistor, the first electrode of the third switch tube is connected to the first switch circuit, and the second electrode of the third switch tube is grounded.

8. The over-temperature protection circuit according to claim 7, characterized in that: The second switch circuit further includes a fourth resistor, a fifth resistor, a sixth resistor and a seventh resistor; One end of the fourth resistor and one end of the fifth resistor are both connected to the first switch circuit, the other end of the fourth resistor is respectively connected to one end of the sixth resistor and the controlled end of the second switch tube, the other end of the fifth resistor is connected to the first electrode of the second switch tube, the other end of the sixth resistor is connected to the first electrode of the third switch tube, one end of the seventh resistor is connected to the second electrode of the second switch tube, and the other end of the seventh resistor is grounded.

9. The over-temperature protection circuit according to claim 7, characterized in that: The second switch circuit further includes an eighth resistor, a ninth resistor and a second capacitor; One end of the eighth resistor is connected to the first switching circuit, the other end of the eighth resistor is connected to the thermistor, one end of the ninth resistor and one end of the second capacitor are both connected to the thermistor, and the other end of the ninth resistor and the other end of the second capacitor are both grounded.

10. A switching power supply, characterized in that: It comprises a rectifier circuit, a control circuit and an over-temperature protection circuit as described in any one of claims 1 to 9.

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