Adjustable hysteresis difference over-temperature protection circuit and driving power supply

Abstract

The utility model provides an adjustable hysteresis difference over-temperature protection circuit which comprises a main power supply circuit and a temperature difference hysteresis circuit, and the main power supply circuit provides stable input voltage for the temperature difference hysteresis circuit. The temperature difference hysteresis circuit comprises a main control chip, a negative temperature coefficient resistor, a first resistor, a second resistor, a first electronic switch tube and a second electronic switch tube, the two ends of the negative temperature coefficient resistor are connected with the first resistor and the second resistor respectively, and the control end of the first electronic switch tube is connected with the first end of the second electronic switch tube. The control end of the second electronic switching tube is connected with the first end of the second resistor. When the temperature of the negative temperature coefficient resistor rises to trigger over-temperature protection, current passes through the first resistor and the first switch electron tube to provide bias current for the second resistor, so that the voltage is greatly increased and a temperature hysteresis difference is formed, meanwhile, the circuit structure is simple, and the use cost is reduced; in addition, the temperature hysteresis difference of the circuit can be flexibly adjusted by adjusting the resistance value of the first resistor.

Description

Technical Field

[0001] The present disclosure relates to the technical field of circuit over-temperature protection, and in particular to an over-temperature protection circuit with adjustable hysteresis and a driving power supply. Background Art

[0002] With technological advancements, the power consumption of electronic devices has increased, leading to increasingly serious overheating problems, especially in power devices and highly integrated devices. To ensure reliable and stable operation of LED drivers in high-temperature environments, an overtemperature protection circuit is often required to ensure that the LED driver operates within rated conditions. Existing technologies implement overtemperature protection by adding temperature control components to the circuit, but this suffers from low accuracy. Alternatively, operational amplifiers (op amps) can be used to implement overtemperature protection circuits, but these components are expensive and unsuitable for large-scale production applications.

[0003] For example, the comparative document CNCN202210527966.5 discloses an over-temperature protection circuit and electronic device with adjustable hysteresis. The reference voltage circuit receives a first current to generate a reference voltage; the temperature adjustment circuit receives a second current to generate a temperature adjustment voltage; a comparison circuit compares the temperature adjustment voltage with the reference voltage. When the temperature adjustment voltage reaches the reference voltage, a logic signal is generated. The logic signal is the over-temperature protection signal that shuts down the chip; the hysteresis feedback circuit controls the corresponding controllable switch tube to disconnect based on the logic signal, so that a hysteresis resistor is connected in series with the temperature adjustment circuit. When the temperature drops back to the initial over-temperature point, the logic signal output by the circuit does not recover. Only when the temperature continues to drop by a hysteresis voltage will the circuit output logic signal recover. This solution solves the problem that the integrated circuit may burn out due to overheating during use. However, this solution uses a large number of op amp components, resulting in high production costs and is not suitable for mass production applications. Utility Model Content

[0004] The purpose of the present disclosure is to overcome the deficiencies in the prior art and to provide a low-cost over-temperature protection circuit and a driving power supply with adjustable temperature hysteresis.

[0005] The purpose of this disclosure is achieved through the following technical solutions:

[0006] An adjustable hysteresis over-temperature protection circuit comprises a main power supply circuit and a temperature difference hysteresis circuit.

[0007] The main power supply circuit is used to provide a stable input voltage to the temperature difference hysteresis circuit.

[0008] The temperature difference hysteresis circuit includes a main control chip, a negative temperature coefficient resistor, a first resistor, a second resistor, a first electronic switch tube and a second electronic switch tube. The first end of the negative temperature coefficient resistor is connected to the voltage output end of the main power supply circuit, and the second end of the negative temperature coefficient resistor is grounded through the second resistor. The first end of the first resistor is connected to the first end of the negative temperature coefficient resistor, the second end of the first resistor is connected to the first end of the first electronic switch tube, and the second end of the first electronic switch tube is connected to the first end of the second resistor. The control end of the first electronic switch tube and the first end of the second electronic switch tube are both connected to the enable control end of the main control chip, the control end of the second electronic switch tube is connected to the first end of the second resistor, and the second end of the second electronic switch tube is grounded.

[0009] In one embodiment, the first resistor is an adjustable resistor.

[0010] In one embodiment, the temperature difference hysteresis circuit further includes a guide diode, wherein the positive electrode of the guide diode is connected to the control end of the first electronic switch tube, and the negative electrode of the guide diode is connected to the first end of the second electronic switch tube.

[0011] In one embodiment, the temperature difference hysteresis circuit further includes a first capacitor, a first end of the first capacitor is connected to the second end of the first electronic switch tube and the control end of the second electronic switch tube, and a second end of the first capacitor is grounded.

[0012] In one embodiment, the main power supply circuit includes a third resistor, a first end of the third resistor is connected to the power input end, and a second end of the third resistor is connected to the voltage output end of the main power supply circuit.

[0013] In one embodiment, the main power supply circuit further includes a fourth resistor, a first end of the fourth resistor is connected to the second end of the third resistor, and a second end of the fourth resistor is grounded.

[0014] In one embodiment, the main power supply circuit further includes a polar capacitor, the positive electrode of the polar capacitor is connected to the power input terminal, and the negative electrode of the polar capacitor is grounded.

[0015] In one embodiment, the main power supply circuit further includes a voltage stabilizing diode, an anode of the voltage stabilizing diode is connected to the second end of the third resistor, and a cathode of the voltage stabilizing diode is grounded.

[0016] In one embodiment, the main power supply circuit further includes a second capacitor, one end of the second capacitor is connected to the second end of the third resistor, and the other end of the second capacitor is grounded.

[0017] A driving power supply comprises any one of the above-mentioned adjustable hysteresis over-temperature protection circuits.

[0018] Compared with the prior art, the present disclosure has at least the following advantages:

[0019] 1. In the above-mentioned adjustable hysteresis over-temperature protection circuit, when the temperature of the negative temperature coefficient resistor rises and triggers the over-temperature protection, a current forms a current loop through the negative temperature coefficient resistor, the first electronic switch tube, the first resistor and the second resistor, and provides a bias current to the second resistor, causing the voltage of the second resistor connected in series with the negative temperature coefficient resistor to increase significantly. At this time, if the temperature of the negative temperature coefficient resistor fluctuates, the circuit will still be in the over-temperature protection state, thereby forming a temperature hysteresis. In addition, the adjustable hysteresis over-temperature protection circuit has a simple structure and does not use operational amplifier components, thereby making the adjustable hysteresis over-temperature protection circuit low in cost.

[0020] 2. On the other hand, since the first resistor is connected in series with the negative temperature coefficient resistor to form a voltage divider circuit, the voltage of the negative temperature coefficient resistor will be changed by adjusting the resistance value of the first resistor, so that the temperature hysteresis of the adjustable hysteresis over-temperature protection circuit can be flexibly adjusted, thereby improving the flexibility of the adjustable hysteresis over-temperature protection circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present disclosure and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0022] Figure 1 1 is a circuit diagram of an over-temperature protection circuit with adjustable hysteresis according to an embodiment;

[0023] Figure 2 It is the hysteresis curve of the voltage at point A, the voltage at point B, and the current at point A in the adjustable hysteresis over-temperature protection circuit. DETAILED DESCRIPTION

[0024] To facilitate understanding of the present disclosure, a more comprehensive description of the present disclosure will be provided below with reference to the accompanying drawings. The accompanying drawings illustrate preferred embodiments of the present disclosure. However, the present disclosure can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure.

[0025] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly attached to the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only implementation methods.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this disclosure pertains. The terms used herein in the specification of this disclosure are intended only to describe specific embodiments and are not intended to limit this disclosure. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0027] In order to better understand the technical solutions and beneficial effects of the present disclosure, the present disclosure is further described in detail below with reference to specific embodiments:

[0028] like Figure 1 As shown, an adjustable hysteresis over-temperature protection circuit 10 according to an embodiment of the present disclosure includes a main power supply circuit 100 and a temperature difference hysteresis circuit 200 .

[0029] The main power supply circuit 100 is used to provide a stable input voltage to the temperature hysteresis circuit 200 .

[0030] The temperature difference hysteresis circuit 200 includes a main control chip U1, a negative temperature coefficient resistor NTC1, a first resistor R4, a second resistor R3, a first electronic switch tube Q1, and a second electronic switch tube Q2. The first end of the negative temperature coefficient resistor NTC1 is connected to the voltage output end of the main power supply circuit 100, and the second end of the negative temperature coefficient resistor NTC1 is grounded through the second resistor R3. The first end of the first resistor R4 is connected to the first end of the negative temperature coefficient resistor NTC1, the second end of the first resistor R4 is connected to the first end of the first electronic switch tube Q1, and the second end of the first electronic switch tube Q1 is connected to the first end of the second resistor R3. The control end of the first electronic switch tube Q1 and the first end of the second electronic switch tube Q2 are both connected to the enable control end of the main control chip U1. The control end of the second electronic switch tube Q2 is connected to the first end of the second resistor R3, and the second end of the second electronic switch tube Q2 is grounded.

[0031] In this embodiment, the main power supply circuit 100 provides a stable voltage for the temperature differential hysteresis circuit 200. Current flows from the output terminal of the main power supply circuit into the first terminal of the negative temperature coefficient resistor NTC1, passes through the second resistor R3, and forms a current loop with the ground terminal. Because the resistance of the negative temperature coefficient resistor NTC1 decreases with increasing temperature, when current flows through the negative temperature coefficient resistor NTC1, its temperature gradually increases, causing the resistance of the negative temperature coefficient resistor NTC1 to gradually decrease. The second resistor R3 is connected in series with the negative temperature coefficient resistor NTC1 to form a voltage divider circuit. As the resistance of the negative temperature coefficient resistor NTC1 gradually decreases, the voltage at the first terminal of the second resistor R3 gradually increases, causing the voltage at the control terminal of the second electronic switch Q2, which is connected to the first terminal of the second resistor R3, to gradually increase.

[0032] When the voltage at the control terminal of the second electronic switch Q2 is greater than its threshold voltage, the second electronic switch Q2 is in the on state. Since the control terminal of the first electronic switch Q1 is connected to the first terminal of the second electronic switch Q2, and the enable control terminal of the main control chip U1 is connected to the first terminal of the second electronic switch Q2, when the second electronic switch Q2 is in the on state, the control terminal of the first electronic switch Q1 and the enable control terminal of the main control chip U1 are connected to the ground terminal via the second terminal of the second electronic switch Q2. This reduces the voltage at the enable control terminal of the main control chip U1, thereby causing the voltage at the control terminal of the first electronic switch Q1 to be lower than the voltage at the first terminal of the first electronic switch Q1. The first electronic switch Q1 is turned on, allowing current to flow through the first resistor R4 and the control terminal of the first electronic switch Q1, forming a current loop through the second electronic switch Q2 and the ground terminal. This causes the voltage at the enable control terminal of the main control chip U1 to decrease, and the current flowing through the negative temperature coefficient resistor NTC1 to decrease, thereby gradually cooling the negative temperature coefficient resistor NTC1.

[0033] Furthermore, since the first electronic switch tube Q1 is in the on state, the current also flows through the first resistor R4 and the first electronic switch tube Q1, and then forms another current loop with the ground terminal through the second resistor R3, so that the voltage at the control terminal of the second electronic switch tube Q2 is further increased, thereby increasing the current flowing through the second electronic switch tube Q2, and further reducing the voltage at the enable control terminal of the main control chip U1. When the voltage at the enable control terminal of the main control chip U1 drops to 0V, the main control chip U1 stops outputting the PWM signal and reduces the output power of the driving power supply; at the same time, the first resistor R4 plays a voltage dividing role on the negative temperature coefficient resistor NTC1, so that the current flowing through the negative temperature coefficient resistor NTC1 is reduced, thereby reducing the temperature of the negative temperature coefficient resistor NTC1.

[0034] Furthermore, as the temperature of the negative temperature coefficient resistor NTC1 decreases, its resistance gradually increases, causing the voltage at the control terminal of the second electronic switch tube Q2 to decrease. When the voltage at the control terminal of the second electronic switch tube Q2 falls below its threshold voltage, the second electronic switch tube Q2 is turned off, preventing current from flowing through the control terminal of the first electronic switch tube Q1 and the second electronic switch tube Q2 to form a current loop with the ground terminal. As a result, the first electronic switch tube Q1 is turned off, which in turn causes the voltage at the first terminal of the second resistor R3 to decrease. The current in the temperature hysteresis circuit then flows only through the negative temperature coefficient resistor NTC1 and the second resistor R3 to form a current loop with the ground terminal. At this time, the voltage of the negative temperature coefficient resistor NTC1 increases again.

[0035] Specifically, the resistance of the negative temperature coefficient resistor NTC1 decreases as its temperature increases, causing the voltage at the control terminal of the second electronic switch tube Q2 to increase. When the temperature of the negative temperature coefficient resistor NTC1 reaches the over-temperature protection trigger temperature, the second electronic switch tube Q2 is turned on. Since the current flowing through the negative temperature coefficient resistor NTC1 decreases, the temperature of the negative temperature coefficient resistor NTC1 decreases, causing its resistance value to increase. When the temperature of the negative temperature coefficient resistor NTC1 drops to the over-temperature protection recovery temperature, the second electronic switch tube Q2 is turned off. The difference between the over-temperature protection trigger temperature and the over-temperature protection recovery temperature is the temperature hysteresis. The corresponding temperature hysteresis curve is detailed in [1]. Figure 2 .

[0036] More specifically, when the temperature of the negative temperature coefficient resistor NTC1 is higher than the over-temperature protection trigger temperature, the temperature of the negative temperature coefficient resistor NTC1 will gradually decrease, but its temperature has not dropped to the over-temperature protection recovery temperature. At this time, if the temperature of the negative temperature coefficient resistor NTC1 rises again, the adjustable hysteresis over-temperature protection circuit 10 will still be in the over-temperature protection state; when the temperature of the negative temperature coefficient resistor NTC1 is higher than the over-temperature protection trigger temperature, and its temperature drops and is lower than the over-temperature protection recovery temperature, the adjustable hysteresis over-temperature protection circuit 10 will resume normal working state. At this time, if the temperature of the negative temperature coefficient resistor NTC1 rises again, the over-temperature protection will not be triggered, thereby forming a temperature hysteresis, thereby preventing the adjustable hysteresis over-temperature protection circuit 10 from frequently triggering the over-temperature protection.

[0037] In the aforementioned adjustable hysteresis over-temperature protection circuit 10, when the temperature of the negative temperature coefficient resistor NTC1 rises, triggering the over-temperature protection, current flows through the current loop formed by the negative temperature coefficient resistor NTC1, the first electronic switch Q1, the first resistor R4, and the second resistor R3, providing a bias current for the second resistor R3, causing the voltage of the second resistor R3 connected in series with the negative temperature coefficient resistor NTC1 to increase significantly. At this time, if the temperature of the negative temperature coefficient resistor NTC1 fluctuates, the circuit will still be in the over-temperature protection state, thereby forming a temperature hysteresis. The adjustable hysteresis over-temperature protection circuit 10 has a simple structure and does not use operational amplifier components, thereby reducing the cost of the adjustable hysteresis over-temperature protection circuit 10. Furthermore, because the first resistor R4 is connected in series with the negative temperature coefficient resistor NTC1 to form a voltage divider circuit, adjusting the resistance value of the first resistor R4 will change the voltage of the negative temperature coefficient resistor NTC1, thereby flexibly adjusting the temperature hysteresis of the adjustable hysteresis over-temperature protection circuit 10, thereby improving the flexibility of the adjustable hysteresis over-temperature protection circuit 10.

[0038] In another embodiment, the first electronic switch tube Q1 is a PNP-type triode, and the second electronic switch tube Q2 is an N-type MOS tube. The first end of the first electronic switch tube Q1 is the emitter of the PNP-type triode, the second end of the first electronic switch tube Q1 is the collector of the PNP-type triode, and the control end of the first electronic switch tube Q1 is the base of the PNP-type triode; the first end of the second electronic switch tube Q2 is the drain of the N-type MOS tube, the second end of the second electronic switch tube Q2 is the source of the N-type MOS tube, and the control end of the second electronic switch tube Q2 is the gate of the N-type MOS tube.

[0039] like Figure 1 As shown, in one embodiment, the first resistor R4 is an adjustable resistor. In this embodiment, as the temperature of the negative temperature coefficient resistor NTC1 increases, its resistance decreases, and the voltage of the second resistor R3 connected in series with the negative temperature coefficient resistor NTC1 increases. Furthermore, the control terminal of the second electronic switch Q2 is connected to the first terminal of the second resistor R3. When the control terminal of the second electronic switch Q2 exceeds its threshold voltage, the second electronic switch Q2 turns on, forming a current loop with the ground terminal. Since the control terminal of the first electronic switch Q1 is grounded through the second electronic switch Q2, the voltage of the control terminal of the first electronic switch Q1 decreases, turning it on. After the first electronic switch Q1 turns on, current flows from its second terminal, passes through the first resistor R4 and the first electronic switch Q1, and then through the second resistor R3 to form another series current loop with the ground terminal. Therefore, adjusting the resistance of the first resistor R4 will change the voltage at the first terminal of the second resistor R3. Since the voltage at the first terminal of the second resistor R3 directly affects the temperature hysteresis difference, adjusting the resistance of the first resistor R4 can flexibly adjust the temperature hysteresis difference.

[0040] like Figure 1 As shown, in one embodiment, the temperature differential hysteresis circuit 200 further includes a steering diode D1, the anode of which is connected to the control terminal of the first electronic switch Q1, and the cathode of which is connected to the first terminal of the second electronic switch Q2. In this embodiment, because the steering diode D1 has a unidirectional current conduction characteristic, current flows from the control terminal of the first electronic switch Q1 and then flows to the second terminal of the second electronic switch Q2 through the steering diode D1. When the second electronic switch Q2 is turned off, the current does not flow back to the control terminal of the first electronic switch Q1, thereby protecting the normal operation of the first electronic switch Q1.

[0041] like Figure 1 As shown, in one embodiment, the temperature hysteresis circuit 200 further includes a first capacitor C2, wherein a first end of the first capacitor C2 is connected to the second end of the first electronic switch tube Q1 and the control end of the second electronic switch tube Q2, and a second end of the first capacitor C2 is grounded. In this embodiment, because the capacitor has the characteristic of storing electrical energy, and the first capacitor C2 is also connected to the control end of the second electronic switch tube Q2, the first capacitor C2 can be used to adjust the speed of change of the control end voltage of the second electronic switch tube Q2, thereby making the rise and fall process of the control of the second electronic switch tube Q2 smoother and more controllable, thereby improving the accuracy of the adjustable hysteresis over-temperature protection circuit 10.

[0042] like Figure 1 As shown, in one embodiment, the main power supply circuit 100 includes a third resistor R1, a first end of the third resistor R1 is connected to the power input terminal, and a second end of the third resistor R1 is connected to the voltage output terminal of the main power supply circuit 100. In this embodiment, because the two ends of the third resistor R1 are respectively connected to the input terminal and the output terminal of the main power supply circuit 100, the third resistor R1 acts as a voltage divider in the main power supply circuit 100, reducing the output voltage at the output terminal of the main power supply circuit 100, thereby preventing the output of an excessively high voltage from affecting the temperature hysteresis circuit 200.

[0043] like Figure 1 As shown, in one embodiment, the main power supply circuit 100 further includes a fourth resistor R2, a first end of the fourth resistor R2 being connected to the second end of the third resistor R1, and a second end of the fourth resistor R2 being grounded. In this embodiment, the fourth resistor R2 and the third resistor R1 are connected in series to form a voltage divider circuit. The input end of the main power supply circuit 100 is grounded through the third resistor R1 and the fourth resistor R2, so that the fourth resistor R2 acts as a voltage divider on the third resistor R1, thereby further reducing the output voltage of the main power supply circuit 100, thereby preventing the output voltage of the main power supply circuit 100 from being too high and protecting the normal operation of the temperature hysteresis circuit 200.

[0044] like Figure 1 As shown, in one embodiment, the main power supply circuit 100 further includes a Zener diode ZD1, the anode of the Zener diode ZD1 being connected to the second end of the third resistor R1, and the cathode of the Zener diode ZD1 being grounded. In this embodiment, the Zener diode ZD1 has a reverse breakdown characteristic of a PN junction and is reverse biased during normal operation. When the voltage across the Zener diode ZD1 exceeds its regulated voltage value, the Zener diode ZD1 will break down and conduct, thereby limiting further voltage increases and achieving a voltage stabilization effect. When the input voltage of the main power supply circuit 100 fluctuates, the Zener diode ZD1 can respond quickly and clamp the output voltage to its regulated voltage value, thereby preventing excessive voltage from damaging the temperature differential hysteresis circuit 200.

[0045] like Figure 1 As shown, in one embodiment, the main power supply circuit 100 further includes a second capacitor C1, one end of the second capacitor C1 being connected to the second end of the third resistor R1, and the other end of the second capacitor C1 being grounded. In this embodiment, because the second capacitor C1 has the characteristic of storing electrical energy in the circuit, when the input voltage of the main power supply circuit 100 fluctuates, the second capacitor C1 can prevent the voltage fluctuation from affecting the temperature hysteresis circuit 200, thereby ensuring that the temperature hysteresis circuit 200 can maintain stable operation.

[0046] like Figure 1 As shown, in one embodiment, the main power supply circuit 100 further includes a polarized capacitor CE1, the positive electrode of which is connected to the power input terminal, and the negative electrode of which is grounded. In this embodiment, since the polarized capacitor CE1 has clear positive and negative polarity, the grounding of its negative electrode can prevent the reverse voltage generated by the power supply from damaging the capacitor, thereby protecting the stability of the circuit. The polarized capacitor CE1 can serve as a filtering element in the circuit, absorbing and releasing charge, which helps to reduce voltage fluctuations at the power input terminal, thereby making the voltage output at the power output terminal more stable.

[0047] A driving power supply includes any of the above-described adjustable hysteresis over-temperature protection circuits 10. In this embodiment, a main power supply circuit 100 provides a stable voltage for a temperature hysteresis circuit 200. Current flows from the output end of the main power supply circuit into the first end of a negative temperature coefficient resistor (NTC1), passes through a second resistor (R3), and forms a current loop with the ground end. Because the resistance of the negative temperature coefficient resistor (NTC1) decreases with increasing temperature, when current flows through the negative temperature coefficient resistor (NTC1), its temperature gradually increases, causing the resistance of the negative temperature coefficient resistor (NTC1) to gradually decrease. Furthermore, the second resistor (R3) is connected in series with the negative temperature coefficient resistor (NTC1) to form a voltage divider circuit. As the resistance of the negative temperature coefficient resistor (NTC1) gradually decreases, the voltage at the first end of the second resistor (R3) gradually increases, causing the voltage at the control end of the second electronic switch (Q2) connected to the first end of the second resistor (R3) to gradually increase. When the voltage at the control terminal of the second electronic switch Q2 is greater than its threshold voltage, the second electronic switch Q2 is in the on state. Since the control terminal of the first electronic switch Q1 is connected to the first terminal of the second electronic switch Q2, and the enable control terminal of the main control chip U1 is connected to the first terminal of the second electronic switch Q2, when the second electronic switch Q2 is in the on state, the control terminal of the first electronic switch Q1 and the enable control terminal of the main control chip U1 are connected to the ground terminal via the second terminal of the second electronic switch Q2. This reduces the voltage at the enable control terminal of the main control chip U1, thereby causing the voltage at the control terminal of the first electronic switch Q1 to be lower than the voltage at the first terminal of the first electronic switch Q1. The first electronic switch Q1 is turned on, allowing current to flow through the first resistor R4 and the control terminal of the first electronic switch Q1, forming a current loop through the second electronic switch Q2 and the ground terminal. This causes the voltage at the enable control terminal of the main control chip U1 to decrease, and the current flowing through the negative temperature coefficient resistor NTC1 to decrease, thereby gradually cooling the negative temperature coefficient resistor NTC1. Furthermore, since the first electronic switch tube Q1 is in the on state, the current also flows through the first resistor R4 and the first electronic switch tube Q1, and then forms another current loop with the ground terminal through the second resistor R3, so that the voltage at the control terminal of the second electronic switch tube Q2 is further increased, thereby increasing the current flowing through the second electronic switch tube Q2, and further reducing the voltage at the enable control terminal of the main control chip U1. When the voltage at the enable control terminal of the main control chip U1 drops to 0V, the main control chip U1 stops outputting the PWM signal and reduces the output power of the driving power supply; at the same time, the first resistor R4 plays a voltage dividing role on the negative temperature coefficient resistor NTC1, so that the current flowing through the negative temperature coefficient resistor NTC1 is reduced, thereby reducing the temperature of the negative temperature coefficient resistor NTC1.Furthermore, as the temperature of the negative temperature coefficient resistor NTC1 decreases, its resistance gradually increases, causing the voltage at the control terminal of the second electronic switch tube Q2 to decrease. When the voltage at the control terminal of the second electronic switch tube Q2 falls below its threshold voltage, the second electronic switch tube Q2 is turned off, preventing current from flowing through the control terminal of the first electronic switch tube Q1 and the second electronic switch tube Q2 to form a current loop with the ground terminal. As a result, the first electronic switch tube Q1 is turned off, which in turn causes the voltage at the first terminal of the second resistor R3 to decrease. The current in the temperature hysteresis circuit then flows only through the negative temperature coefficient resistor NTC1 and the second resistor R3 to form a current loop with the ground terminal. At this time, the voltage of the negative temperature coefficient resistor NTC1 increases again. Specifically, the resistance of the negative temperature coefficient resistor NTC1 decreases as its temperature increases, causing the voltage at the control terminal of the second electronic switch tube Q2 to increase. When the temperature of the negative temperature coefficient resistor NTC1 reaches the over-temperature protection trigger temperature, the second electronic switch tube Q2 is turned on. Since the current flowing through the negative temperature coefficient resistor NTC1 decreases, the temperature of the negative temperature coefficient resistor NTC1 decreases, causing its resistance value to increase. When the temperature of the negative temperature coefficient resistor NTC1 drops to the over-temperature protection recovery temperature, the second electronic switch tube Q2 is turned off. The difference between the over-temperature protection trigger temperature and the over-temperature protection recovery temperature is the temperature hysteresis. More specifically, when the temperature of the negative temperature coefficient resistor NTC1 is higher than the over-temperature protection trigger temperature, the temperature of the negative temperature coefficient resistor NTC1 will gradually decrease, but its temperature has not dropped to the over-temperature protection recovery temperature. At this time, if the temperature of the negative temperature coefficient resistor NTC1 rises again, the adjustable hysteresis over-temperature protection circuit 10 will still be in the over-temperature protection state; when the temperature of the negative temperature coefficient resistor NTC1 is higher than the over-temperature protection trigger temperature, its temperature drops and falls below the over-temperature protection recovery temperature, the adjustable hysteresis over-temperature protection circuit 10 will resume normal working state. At this time, if the temperature of the negative temperature coefficient resistor NTC1 rises again, the over-temperature protection will not be triggered, thereby forming a temperature hysteresis, thereby preventing the adjustable hysteresis over-temperature protection circuit 10 from frequently triggering the over-temperature protection.

[0048] Compared with the prior art, the present disclosure has at least the following advantages:

[0049] 1. In the above-mentioned adjustable hysteresis over-temperature protection circuit 10, when the temperature of the negative temperature coefficient resistor NTC1 rises and triggers the over-temperature protection, current flows through the current loop formed by the negative temperature coefficient resistor NTC1, the first electronic switch Q1, the first resistor R4, and the second resistor R3, and provides a bias current to the second resistor R3, causing the voltage of the second resistor R3 connected in series with the negative temperature coefficient resistor NTC1 to increase significantly. At this time, if the temperature of the negative temperature coefficient resistor NTC1 fluctuates, the circuit will still be in the over-temperature protection state, thereby forming a temperature hysteresis. In addition, the adjustable hysteresis over-temperature protection circuit 10 has a simple structure and does not use operational amplifier components, thereby making the adjustable hysteresis over-temperature protection circuit 10 relatively low in cost.

[0050] 2. On the other hand, since the first resistor R4 is connected in series with the negative temperature coefficient resistor NTC1 to form a voltage divider circuit, the voltage of the negative temperature coefficient resistor NTC1 will be changed by adjusting the resistance value of the first resistor R4, so that the temperature hysteresis of the adjustable hysteresis over-temperature protection circuit 10 can be flexibly adjusted, thereby improving the flexibility of the adjustable hysteresis over-temperature protection circuit 10.

[0051] The above-described embodiments merely represent several implementation methods of the present disclosure. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the disclosed patent. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the scope of the present disclosure, all of which fall within the scope of protection of the present disclosure. Therefore, the scope of protection of the disclosed patent shall be determined by the appended claims.

Claims

1. An adjustable hysteresis over-temperature protection circuit, characterized in that: Including main power supply circuit and temperature difference hysteresis circuit; The main power supply circuit is used to provide a stable input voltage to the temperature difference hysteresis circuit; The temperature difference hysteresis circuit includes a main control chip, a negative temperature coefficient resistor, a first resistor, a second resistor, a first electronic switch tube and a second electronic switch tube. The first end of the negative temperature coefficient resistor is connected to the voltage output end of the main power supply circuit, and the second end of the negative temperature coefficient resistor is grounded through the second resistor. The first end of the first resistor is connected to the first end of the negative temperature coefficient resistor, the second end of the first resistor is connected to the first end of the first electronic switch tube, and the second end of the first electronic switch tube is connected to the first end of the second resistor. The control end of the first electronic switch tube and the first end of the second electronic switch tube are both connected to the enable control end of the main control chip, the control end of the second electronic switch tube is connected to the first end of the second resistor, and the second end of the second electronic switch tube is grounded.

2. The adjustable hysteresis over-temperature protection circuit according to claim 1, characterized in that: The first resistor is an adjustable resistor.

3. The adjustable hysteresis over-temperature protection circuit according to claim 1, characterized in that: The temperature difference hysteresis circuit further includes a guide diode, wherein the positive electrode of the guide diode is connected to the control end of the first electronic switch tube, and the negative electrode of the guide diode is connected to the first end of the second electronic switch tube.

4. The adjustable hysteresis over-temperature protection circuit according to claim 3, characterized in that: The temperature difference hysteresis circuit further includes a first capacitor, a first end of the first capacitor is connected to the second end of the first electronic switch tube and the control end of the second electronic switch tube, and a second end of the first capacitor is grounded.

5. The adjustable hysteresis over-temperature protection circuit according to claim 1, characterized in that: The main power supply circuit includes a third resistor, a first end of the third resistor is connected to the power input end, and a second end of the third resistor is connected to the voltage output end of the main power supply circuit.

6. The adjustable hysteresis over-temperature protection circuit according to claim 5, characterized in that: The main power supply circuit further includes a fourth resistor, a first end of the fourth resistor is connected to the second end of the third resistor, and a second end of the fourth resistor is grounded.

7. The adjustable hysteresis over-temperature protection circuit according to claim 5, characterized in that: The main power supply circuit further includes a voltage stabilizing diode, an anode of the voltage stabilizing diode is connected to the second end of the third resistor, and a cathode of the voltage stabilizing diode is grounded.

8. The adjustable hysteresis over-temperature protection circuit according to claim 5, characterized in that: The main power supply circuit further includes a second capacitor, one end of the second capacitor is connected to the second end of the third resistor, and the other end of the second capacitor is grounded.

9. The adjustable hysteresis over-temperature protection circuit according to claim 5, characterized in that: The main power supply circuit further includes a polar capacitor, a positive electrode of the polar capacitor is connected to the power input terminal, and a negative electrode of the polar capacitor is grounded.

10. A driving power supply, characterized in that: The invention comprises the over-temperature protection circuit with adjustable hysteresis as claimed in any one of claims 1 to 9.

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