Over-temperature protection circuit and power supply device using the same

Abstract

The application provides an over-temperature protection circuit and a power supply device using the same. The over-temperature protection circuit is used in a power supply device including a PFC stage, and includes a constant current source, a thermistor, a voltage compensation module and a comparator. The first end of the thermistor is electrically connected to a first node, and the thermistor is a negative temperature coefficient thermistor. The voltage compensation module generates a corresponding compensation voltage according to a switching driving signal of the PFC stage and an average duty cycle. The average duty cycle has a linear relationship with an input voltage of the power supply device, and the compensation voltage has a linear relationship with the average duty cycle. The comparator is used to compare the voltage on the positive input end with an over-temperature protection voltage setting value, and outputs a signal to trigger an over-temperature protection function when the voltage on the positive input end is lower than the over-temperature protection voltage setting value.

Description

Technical Field

[0001] This invention relates to an over-temperature protection circuit and a power supply device suitable for it, particularly an over-temperature protection circuit and a power supply device suitable for it that can improve the reliability of over-temperature protection function. Background Technology

[0002] In existing consumer electronics power supplies, the input voltage range is generally defined between 90 and 264Vac to adapt to the power grid requirements of different countries and regions. Power supplies with a power output greater than 75W require the addition of a PFC (power factor correction) circuit. Generally, PFC circuits often employ boost PFC, characterized by lower efficiency at low input voltage and higher efficiency at high input voltage. At the same output power, this characteristic results in higher component temperatures at low input voltage compared to high input voltage.

[0003] Traditionally, over-temperature protection is often implemented using thermistors, and the thermistor resistance is usually fixed when over-temperature protection is triggered, meaning the protection temperature is fixed. Taking a 230W power supply as an example, in steady-state operation, the overall component temperature at a 90Vac input is about 10°C higher than at a 264Vac input. For existing over-temperature protection functions, the protection temperature should be about 10°C higher than the system's steady-state operating temperature. If the protection temperature is set based on a 90Vac input, then at a 264Vac input, the protection temperature will be about 20°C higher than the overall component temperature, potentially preventing the over-temperature protection function from triggering even when components overheat. If the protection temperature is set based on a 264Vac input, then at a 90Vac input, the protection temperature will be approximately equal to the overall component temperature, leading to false triggering of the over-temperature protection function and rendering it ineffective. Therefore, in current practices, the over-temperature protection function cannot be applied to different input voltage conditions simultaneously, resulting in reduced reliability.

[0004] Therefore, designing an over-temperature protection circuit that can improve upon the above-mentioned existing technology and a suitable power supply device is an urgent need. Summary of the Invention

[0005] The purpose of this invention is to provide an over-temperature protection circuit and a suitable power supply device thereof, enabling the over-temperature protection function to have different trigger temperatures under different input voltages. This allows the over-temperature protection function to be applicable to different input voltage conditions, thereby improving the reliability of the over-temperature protection function.

[0006] To achieve the above objectives, this invention provides an over-temperature protection circuit suitable for power supply devices including a PFC stage. The over-temperature protection circuit includes a constant current source, a thermistor, a voltage compensation module, and a comparator. The constant current source provides a reference current to a first node. The first terminal of the thermistor, which is a negative temperature coefficient thermistor, is electrically connected to the first node. The voltage compensation module generates a corresponding compensation voltage based on the switching drive signal of the PFC stage and the average duty cycle, wherein the average duty cycle is linearly related to the input voltage of the power supply device, and the compensation voltage is linearly related to the average duty cycle. The comparator includes a non-inverting input terminal, an inverting input terminal, and an output terminal. The non-inverting input terminal is electrically coupled to the first node, and the inverting input terminal is electrically coupled to the over-temperature protection voltage setting value. When the voltage at the non-inverting input terminal is lower than the over-temperature protection voltage setting value, the output terminal outputs a control signal to trigger the over-temperature protection function of the power supply device.

[0007] To achieve the above objectives, the present invention further provides a power supply device comprising a PFC stage, a DC / DC conversion stage, and an over-temperature protection circuit, wherein the input terminal of the DC / DC conversion stage is electrically coupled to the output terminal of the PFC stage. The over-temperature protection circuit comprises a constant current source, a thermistor, a voltage compensation module, and a comparator. The constant current source provides a reference current to a first node. The first terminal of the thermistor is electrically connected to the first node, and the thermistor is a negative temperature coefficient thermistor. The voltage compensation module generates a corresponding compensation voltage based on the switching drive signal of the PFC stage and the average duty cycle, wherein the average duty cycle is linearly related to the input voltage of the power supply device, and the compensation voltage is linearly related to the average duty cycle. The comparator includes a non-inverting input terminal, an inverting input terminal, and an output terminal, wherein the non-inverting input terminal is electrically coupled to the first node, and the inverting input terminal is electrically coupled to an over-temperature protection voltage setting value. When the voltage at the non-inverting input terminal is lower than the over-temperature protection voltage setting value, the output terminal outputs a control signal to trigger the over-temperature protection function of the power supply device.

[0008] To achieve the above objectives, the present invention further provides an over-temperature protection circuit suitable for power supply devices including a PFC stage. The over-temperature protection circuit includes a constant current source, a thermistor, a voltage compensation module, and a comparator. The constant current source provides a reference current to a first node. The first terminal of the thermistor is electrically connected to the first node; the thermistor is a negative temperature coefficient thermistor. The voltage compensation module generates a corresponding compensation voltage based on the switching drive signal of the PFC stage and the average duty cycle, wherein the average duty cycle is linearly related to the input voltage of the power supply device, and the compensation voltage is linearly related to the average duty cycle. The comparator includes a first non-inverting input terminal, a second non-inverting input terminal, an inverting input terminal, and an output terminal. The first non-inverting input terminal is electrically coupled to the first node, the second non-inverting input terminal is electrically coupled to the output terminal of the voltage compensation module, and the inverting input terminal is electrically coupled to the over-temperature protection voltage setting value. When the sum of the voltages at the first and second non-inverting input terminals is lower than the over-temperature protection voltage setting value, the output terminal outputs a control signal to trigger the over-temperature protection function of the power supply device.

[0009] To achieve the above objectives, the present invention further provides a power supply device comprising a PFC stage, a DC / DC conversion stage, and an over-temperature protection circuit, wherein the input terminal of the DC / DC conversion stage is electrically coupled to the output terminal of the PFC stage. The over-temperature protection circuit comprises a constant current source, a thermistor, a voltage compensation module, and a comparator. The constant current source provides a reference current to a first node. The first terminal of the thermistor is electrically connected to the first node, and the thermistor is a negative temperature coefficient thermistor. The voltage compensation module generates a corresponding compensation voltage based on the switching drive signal of the PFC stage and the average duty cycle, wherein the average duty cycle is linearly related to the input voltage of the power supply device, and the compensation voltage is linearly related to the average duty cycle. The comparator includes a first non-inverting input, a second non-inverting input, an inverting input, and an output. The first non-inverting input is electrically coupled to a first node, the second non-inverting input is electrically coupled to the output of the voltage compensation module, and the inverting input is electrically coupled to the over-temperature protection voltage setting. When the sum of the voltages at the first and second non-inverting inputs is lower than the over-temperature protection voltage setting, the output outputs a control signal to trigger the over-temperature protection function of the power supply. Attached Figure Description

[0010] Figure 1A This is a schematic diagram of the circuit structure of an over-temperature protection circuit according to an embodiment of the present invention;

[0011] Figure 1B for Figure 1A A schematic diagram of the circuit structure of a variation of the over-temperature protection circuit;

[0012] Figure 2 This is a schematic diagram of the circuit structure of the PFC stage and DC / DC conversion stage of a power supply device according to an embodiment of the present invention.

[0013] Figure 3 exemplify Figure 1B The circuit structure of one implementation of the voltage compensation module;

[0014] Figure 4 and Figure 5A Two implementation methods are shown when the PFC IC of the PFC stage of the power supply device performs part of the function in the over-temperature protection circuit.

[0015] Figure 5B exemplify Figure 5A Examples of changes;

[0016] Figure 6 exemplify Figure 5A and Figure 5B One implementation of the voltage compensation module in the system.

[0017] [Symbol Explanation]

[0018] 1: Over-temperature protection circuit

[0019] 2: Power supply device

[0020] 11: Constant Current Source

[0021] R1: First resistor

[0022] A: First node

[0023] NTC: Thermistor

[0024] 12, 12a: Voltage compensation module

[0025] 121: Average value sampling module

[0026] 122: Compensation Coefficient Generation Module

[0027] Vc: Compensation voltage

[0028] 13, 13a: Comparator

[0029] Iref: Reference current

[0030] 21: PFC level

[0031] Vgs: Switch drive signal

[0032] Vin: Input voltage

[0033] Votp: Over-temperature protection voltage setting value

[0034] 22: DC / DC conversion stage

[0035] Q1: Switching transistor

[0036] R2: Second resistor

[0037] R3: the third resistor

[0038] C1: capacitor

[0039] 211: PFC IC

[0040] R4, R5, R6, R7: resistors Detailed Description of Embodiments

[0041] Some exemplary embodiments that embody the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention is capable of various modifications in different forms without departing from the scope of the present invention, and that the description and drawings herein are essentially for illustrative purposes only, and not for limiting the present invention.

[0042] Figure 1A is a schematic diagram of the circuit structure of an over-temperature protection circuit according to an embodiment of the present invention, Figure 2 is a schematic diagram of the circuit structure of a PFC stage and a DC / DC conversion stage of a power supply device according to an embodiment of the present invention. As shown in Figure 1A and Figure 2 , the over-temperature protection circuit 1 is suitable for a power supply device 2. In some embodiments, the over-temperature protection circuit 1 can also be included in the power supply device. The over-temperature protection circuit 1 comprises a constant current source 11, a thermistor NTC, a voltage compensation module 12 and a comparator 13. The constant current source 11 is configured to provide a reference current Iref to a first node A. A first end of the thermistor NTC is electrically connected to the first node A, wherein the thermistor NTC is a negative temperature coefficient thermistor. The voltage compensation module 12 generates a corresponding compensation voltage Vc according to a switching driving signal Vgs of a PFC stage 21 in the power supply device 2 and an average duty ratio, wherein the average duty ratio is in a linear relationship with an input voltage Vin of the power supply device 2, and the compensation voltage Vc is in a linear relationship with the average duty ratio. For example, the average duty ratio is linearly related to the input voltage Vin of the power supply device 2, and the compensation voltage Vc is proportional to the average duty ratio, but it is not limited thereto. In some embodiments, the voltage compensation module 12 obtains the average duty ratio by sampling the switching driving signal Vgs, and the compensation voltage Vc is equal to the product of the high-level voltage value of the switching driving signal Vgs, the average duty ratio and a compensation coefficient. The comparator 13 is configured to compare a sum of the voltage across the thermistor NTC and the compensation voltage Vc with an over-temperature protection voltage setting value Votp, and output a control signal when the voltage sum is lower than the over-temperature protection voltage setting value Votp (that is, when Vc+Iref*Rntc<Votp), so as to trigger the over-temperature protection function of the power supply device 2, wherein Rntc is the resistance value of the thermistor NTC.

[0043] Therefore, under the same load, if the input voltage Vin is different, the switch driving signal Vgs and the average duty cycle will change accordingly, which in turn changes the compensation voltage Vc generated by the voltage compensation module 12. Since the compensation voltage Vc changes, the resistance value of the thermistor NTC and its corresponding temperature are also different when the over-temperature protection function is triggered. For example, when the average duty cycle is linearly related to the input voltage Vin of the power supply device 2, and the compensation voltage Vc is proportional to the average duty cycle, if the input voltage Vin changes from high voltage to low voltage, the average duty cycle and the compensation voltage Vc increase, so that when the over-temperature protection function is triggered, the resistance value of the thermistor NTC decreases and its corresponding temperature rises. Therefore, when the steady-state operating temperature of the heating element in the power supply device 2 rises as the input voltage Vin decreases, the temperature of the thermistor NTC when triggering the over-temperature protection function also rises accordingly, enabling the over-temperature protection function to still perform its function. It can be seen that through the over-temperature protection circuit 1 of the present invention, the over-temperature protection function is applicable to different input voltage conditions, thereby improving the reliability of the over-temperature protection function. On the other hand, the present invention achieves an over-temperature protection function suitable for a wide AC input voltage range. In some embodiments, as Figure 1B shown, the over-temperature protection circuit 1 further comprises a first resistor R1, a first end of the first resistor R1 is electrically connected to a first node A, and a first end of the thermistor NTC is electrically connected to a second end of the first resistor R1. By providing the first resistor R1, it is easier to adjust the resistance value of the thermistor NTC to implement over-temperature protection. In this case, the comparator 13 is configured to compare the sum of the voltage across the first resistor R1, the voltage across the thermistor NTC and the compensation voltage Vc with an over-temperature protection voltage set value Votp, and output a control signal to trigger the over-temperature protection function of the power supply device 2 when the voltage sum is lower than the over-temperature protection voltage set value Votp (that is, when Vc+Iref*(R1+Rntc)<Votp)

[0044] In some embodiments, as Figure 2 shown, the power supply device 2 further comprises a DC / DC conversion stage 22, wherein an input end of the DC / DC conversion stage 22 is electrically coupled to an output end of the PFC stage 21. In Figure 2 illustrated embodiment, the aforementioned switch driving signal Vgs and average duty cycle of the PFC stage 21 are the gate driving signal and the average duty cycle of the switch tube Q1 of the PFC stage 21. In addition, Figure 2The circuit structure of the power supply device 2 shown is merely an example, and the power supply device of the present invention is not actually limited thereto. The PFC stage of the power supply device includes, but is not limited to, boost PFC, totem-pole PFC, dual-boost PFC, or three-phase PFC, and the DC / DC conversion stage of the power supply device includes, but is not limited to, flyback circuits, LLC circuits, asymmetrical half-bridge circuits, forward circuits, active clamp flyback circuits, or buck circuits. It should be noted that in the power supply device of the present invention, the input and output of the DC / DC conversion stage are fixed, and the efficiency of the PFC stage varies with the input voltage of the power supply device, while the efficiency of the DC / DC conversion stage does not vary with the input voltage of the power supply device.

[0045] like Figure 1A and Figure 2 As shown, in some embodiments, the temperature corresponding to the resistance value of the thermistor NTC is the desired protection temperature of the power supply device 2. Under different input voltages Vin, the magnitude of the compensation voltage Vc depends on the steady-state operating temperature of the heating element in the power supply device 2 corresponding to the desired protection temperature. The heating element includes the magnets and switching transistors of the PFC stage 21 and the DC / DC conversion stage 22, respectively.

[0046] In some embodiments, the input voltage Vin has an upper limit and a lower limit. When the input voltage Vin equals the upper limit, the heating element in the power supply device 2 corresponds to a first steady-state operating temperature; when the input voltage Vin equals the lower limit, the heating element in the power supply device 2 corresponds to a second steady-state operating temperature, wherein the first steady-state operating temperature and the second steady-state operating temperature have a temperature difference. At any input voltage Vin, the difference between the desired protection temperature and the steady-state operating temperature is within a target temperature range, wherein the target temperature range depends on the temperature difference between the first steady-state operating temperature and the second steady-state operating temperature, and the target temperature range includes, but is not limited to, 7–13°C.

[0047] It should be noted that the compensation voltage Vc is zero under no-load conditions, and the expected protection temperature under no-load conditions is higher than the steady-state operating temperature under any input voltage Vin.

[0048] Figure 3 Examples are shown Figure 1B The circuit structure of one embodiment of the voltage compensation module 12. In some embodiments, such as Figure 3As shown, the voltage compensation module 12 has its two ends electrically connected to the second terminal of the thermistor NTC and the ground terminal, respectively, and includes a second resistor R2, a third resistor R3, and a capacitor C1. The second terminal of the thermistor NTC is electrically connected to the first terminal of the second resistor R2, the first terminal of the third resistor R3, and the first terminal of the capacitor C1. The second terminals of the second resistor R2 and the second terminal of the capacitor C1 are grounded, and the second terminal of the third resistor R3 receives the switch drive signal Vgs. In this embodiment, the compensation voltage Vc is equal to the product of the high-level voltage value of the switch drive signal Vgs, the average duty cycle, and the compensation coefficient, and the compensation coefficient depends on the resistance values ​​of the second resistor R2, the third resistor R3, and the capacitance value of the capacitor C1. It should be noted that the specific implementation of the voltage compensation module 12 of the present invention is not limited to this embodiment. Figure 3 As shown, only the appropriate compensation voltage Vc needs to be generated to correspond to different switching drive signals Vgs and average duty cycles. Furthermore, in this embodiment, comparator 13 includes a non-inverting input, an inverting input, and an output. The non-inverting input is electrically coupled to the first node A, and the inverting input is electrically coupled to the over-temperature protection voltage setting value Votp. When the voltage at the non-inverting input is lower than the over-temperature protection voltage setting value Votp, the output terminal outputs a control signal to trigger the over-temperature protection function of the power supply device 2.

[0049] Generally, in the power supply device 2, the heating element has a steady-state operating temperature corresponding to the upper and lower limits of the input voltage Vin. This invention can set the desired protection temperature according to the steady-state operating temperature and obtain the resistance value of the corresponding thermistor NTC by looking up a table, thereby designing the various parameters in the over-temperature protection circuit 1. The following uses… Figure 2 and Figure 3 The specific design process is illustrated with examples.

[0050] Assuming the upper and lower limits of the input voltage Vin are 264Vac and 90Vac respectively, and based on the circuit topology of power supply device 2, the expected protection temperatures when the input voltage Vin is 264Vac and 90Vac are set to 103℃ and 113℃ respectively, after referring to Table 1, the resistance values ​​of the thermistor NTC at 103℃ and 113℃ are 4.71kΩ and 3.43kΩ respectively (the correspondence between resistance and temperature can be found in the thermistor's datasheet).

[0051] Table 1

[0052] 100 5.4072 5.1977 4.9958 101 5.2352 5.0307 4.8337 102 5.0693 4.8697 4.6775 103 4.9094 4.7146 4.5270 104 4.7552 4.5650 4.3820 105 4.6065 4.4208 4.2422 106 4.4630 4.2817 4.1074 107 4.3246 4.1476 3.9775 108 4.1910 4.0183 3.8523 109 4.0622 3.8935 3.7315 110 3.9379 3.7732 3.6150 111 3.8179 3.6571 3.5027 112 3.7021 3.5450 3.3943 113 3.5903 3.4369 3.2898 114 3.4824 3.3326 3.1890 115 3.3782 3.2319 3.0917 116 3.2777 3.1348 2.9978 117 3.1805 3.0410 2.9072 118 3.0868 2.9504 2.8198 119 2.9962 2.8630 2.7354

[0053] Figure 2 In PFC level 21, the following relationship exists based on the volt-second balance:

[0054] Vin*D=(Vout-Vin)(1-D) (1)

[0055] Vin=Vout(1-D) (2)

[0056] Where Vin represents the instantaneous value of the input voltage, Vout represents the output voltage of PFC stage 21, and D represents the duty cycle when the input voltage is the instantaneous value. Taking the average of both sides of equation (2) yields:

[0057] Vin_avg=Vout(1-Davg) (3)

[0058] Where Vin_avg represents the average value of the input voltage, and Davg represents the average duty cycle.

[0059] in accordance with Figure 2 and Figure 3 The circuit topology and the parameter design in the circuit must satisfy the following equations (4) and (5):

[0060] Vgs_H*Davg_90Vac*k+Iref*(R1+3.43kΩ)=Votp (4)

[0061] Vgs_H*Davg_264Vac*k+Iref*(R1+4.71kΩ)=Votp (5)

[0062] Wherein, Vgs_H is the high-level voltage value of the switch drive signal Vgs, Davg_90Vac and Davg_264Vac are the average duty cycles when the input voltage Vin is 90Vac and 264Vac respectively, and k is the compensation coefficient.

[0063] By designing Iref and Votp according to the aforementioned equations (4) and (5) and calculating k and R1, the over-temperature protection circuit 1 can be made suitable for an input voltage range of 90Vac to 264Vac. Furthermore, it can provide over-temperature protection even under extreme conditions of the input voltage Vin (i.e., equal to 90Vac or 264Vac), thus improving the reliability of the over-temperature protection circuit 1. For example, when Vgs_H = 10V, Davg_90Vac = 0.8, and Davg_264Vac = 0.4, Iref = 200uA and Votp = 2V can be designed, and k = 0.0625 and R1 = 4.05kΩ can be calculated according to the aforementioned equations (4) and (5).

[0064] Furthermore, in some embodiments, such as Figure 2 and Figure 4As shown, the PFC stage 21 in the power supply unit 2 also includes a PFC IC 211. The PFC IC 211 performs the functions of the constant current source 11 and comparator 13 in the over-temperature protection circuit 1. The PFC IC 211 is electrically connected to the first terminal of the first resistor R1 through its OTP pin and outputs a reference current Iref. Furthermore, the PFC IC 211 receives the sum of the voltage across the first resistor R1, the voltage across the thermistor NTC, and the compensation voltage Vc through its OTP pin, and determines whether to trigger the over-temperature protection function based on the relationship between the sum of the voltages and the over-temperature protection voltage setting value Votp.

[0065] In other embodiments, such as Figure 2 and Figure 5A As shown, the PFC IC 211 in the PFC stage 21 of the power supply unit 2 performs the functions of the constant current source 11, voltage compensation module 12a, and comparator 13a in the over-temperature protection circuit 1. The PFC IC 211 is electrically connected to the first terminal of the thermistor NTC via its OTP pin and outputs a reference current Iref, thereby receiving the voltage across the thermistor NTC. Furthermore, the PFC IC 211 samples the switch drive signal Vgs and calculates its average duty cycle to generate a compensation voltage Vc. Further, the PFC IC 211 obtains the sum of the voltage across the thermistor NTC and the compensation voltage Vc, and determines whether to trigger the over-temperature protection function based on the relationship between the sum of the voltages and the over-temperature protection voltage setting value Votp.

[0066] In some embodiments, such as Figure 5B As shown, the over-temperature protection circuit 1 also includes a first resistor R1, which is electrically connected between the OTP pin of the PFC IC 211 and its first terminal. By setting the first resistor R1, the resistance value of the thermistor NTC can be adjusted more easily to achieve over-temperature protection. In this case, the OTP pin of the PFC IC 211 receives the voltage across the first resistor R1 and the voltage across the thermistor NTC, and the PFC IC 211 determines whether to trigger the over-temperature protection function based on the relationship between the sum of the voltages across the first resistor R1, the thermistor NTC, and the compensation voltage Vc, and the over-temperature protection voltage setting value Votp.

[0067] exist Figure 5A and Figure 5BIn the illustrated embodiment, comparator 13a includes a first non-inverting input, a second non-inverting input, an inverting input, and an output. The first non-inverting input is electrically coupled to a first node A, the second non-inverting input is electrically coupled to the output of voltage compensation module 12, and the inverting input is electrically coupled to the over-temperature protection voltage setting value Votp. When the sum of the voltages at the first and second non-inverting inputs is lower than the over-temperature protection voltage setting value Votp, the output outputs a control signal to trigger the over-temperature protection function of power supply device 2. Furthermore, in the embodiment shown in FIG. 5, voltage compensation module 12a includes an average value sampling module 121 and a compensation coefficient generation module 122. The average value sampling module 121 samples the average value of the switch drive signal Vgs and outputs the sampling result to the compensation coefficient generation module 122. The compensation coefficient generation module 122 multiplies the sampling result by its generated compensation coefficient k, thereby generating and outputting the compensation voltage Vc.

[0068] Figure 6 exemplify Figure 5A and Figure 5B This is one embodiment of the voltage compensation module 12a. It should be noted that the specific implementation of the voltage compensation module 12a is not limited to this. For example... Figure 6 As shown, the average value sampling module 121 is implemented using a low-pass filter, where the cutoff frequency of the low-pass filter is less than 0.5fc, and fc is the input voltage power frequency. The compensation coefficient generation module 122 is implemented using a non-inverting proportional operational amplifier circuit. The compensation coefficient k can be adjusted by adjusting the resistance values ​​of resistors R4, R5, R6, and R7 in the non-inverting proportional operational amplifier circuit. Figure 6 In the embodiment shown, k = R5*(R6+R7) / [R6*(R4+R5)].

[0069] In summary, this invention provides an over-temperature protection circuit and a suitable power supply device, enabling the over-temperature protection function to have different trigger temperatures under different input voltages. Therefore, the over-temperature protection function is applicable to different input voltage conditions, thereby improving the reliability of the over-temperature protection function.

[0070] It should be noted that the above are merely preferred embodiments for illustrating the present invention, and the present invention is not limited to the described embodiments. The scope of the present invention is defined by the appended claims. Furthermore, the present invention may be modified in various ways by those skilled in the art, all of which shall not depart from the scope of protection sought by the appended claims.

Claims

1. An over-temperature protection circuit, characterized in that, Applicable to a power supply device, wherein the power supply device includes a PFC stage, the over-temperature protection circuit includes: A constant current source is used to provide a reference current to a first node; A thermistor, wherein the first terminal of the thermistor is electrically connected to the first node, and the thermistor is a negative temperature coefficient thermistor. A voltage compensation module generates a corresponding compensation voltage based on a switch drive signal and an average duty cycle of the PFC stage, wherein the average duty cycle is linearly related to an input voltage of the power supply device, and the compensation voltage is linearly related to the average duty cycle; and A comparator includes a non-inverting input, an inverting input, and an output. The non-inverting input is electrically coupled to the first node, and the inverting input is electrically coupled to an over-temperature protection voltage setting. When the voltage at the non-inverting input falls below the over-temperature protection voltage setting, the output sends a control signal to trigger an over-temperature protection function of the power supply. The voltage compensation module is electrically connected between the first node and a ground terminal, and the second end of the thermistor is electrically connected to the ground terminal.

2. The over-temperature protection circuit as described in claim 1, characterized in that, It also includes a first resistor, wherein the first resistor is electrically connected between the first node and the first end of the thermistor.

3. The over-temperature protection circuit as described in claim 1, characterized in that, The voltage compensation module is electrically connected between the second terminal of the thermistor and the ground terminal.

4. The over-temperature protection circuit as described in claim 3, characterized in that, The voltage compensation module includes a second resistor, a third resistor, and a capacitor. The second terminal of the thermistor is electrically connected to the first terminal of the second resistor, the first terminal of the third resistor, and the first terminal of the capacitor. The second terminal of the second resistor and the second terminal of the capacitor are grounded. The second terminal of the third resistor receives the switch drive signal.

5. The over-temperature protection circuit as described in claim 4, characterized in that, The compensation voltage is equal to the product of the high-level voltage of the switch drive signal, the average duty cycle, and a compensation coefficient.

6. The over-temperature protection circuit as described in claim 5, characterized in that, The voltage compensation module obtains the average duty cycle by sampling the switch drive signal.

7. The over-temperature protection circuit as described in claim 5, characterized in that, The compensation factor depends on the resistance of the second resistor, the resistance of the third resistor, and the capacitance of the capacitor.

8. The over-temperature protection circuit as described in claim 1, characterized in that, The resistance of the thermistor corresponds to the desired protection temperature of the power supply device. Under different input voltages, the magnitude of the compensation voltage depends on the steady-state operating temperature of the heating element in the power supply device corresponding to the desired protection temperature.

9. The over-temperature protection circuit as described in claim 8, characterized in that, The input voltage has an upper limit and a lower limit. When the input voltage is equal to the upper limit, the heating element in the power supply device corresponds to a first steady-state operating temperature. When the input voltage is equal to the lower limit, the heating element in the power supply device corresponds to a second steady-state operating temperature. The first steady-state operating temperature and the second steady-state operating temperature have a temperature difference. Under any input voltage, the difference between the desired protection temperature and the steady-state operating temperature is within a target temperature range, which depends on the temperature difference.

10. The over-temperature protection circuit as described in claim 9, characterized in that, The target temperature range is 5~15°C.

11. The over-temperature protection circuit as described in claim 8, characterized in that, The compensation voltage is zero under no-load conditions, and the desired protection temperature under no-load conditions is higher than the steady-state operating temperature at any of the input voltages.

12. The over-temperature protection circuit as described in claim 8, characterized in that, The power supply device also includes a DC / DC conversion stage, the input of which is electrically coupled to the output of the PFC stage, and the heating element includes the magnets and switching transistors of the PFC stage and the DC / DC conversion stage respectively.

13. A power supply device, characterized in that, Include: A PFC stage and a DC / DC conversion stage, wherein the input of the DC / DC conversion stage is electrically coupled to the output of the PFC stage; and An over-temperature protection circuit includes: A constant current source is used to provide a reference current to a first node; A thermistor, wherein the first terminal of the thermistor is electrically connected to the first node, and the thermistor is a negative temperature coefficient thermistor. A voltage compensation module generates a corresponding compensation voltage based on a switch drive signal and an average duty cycle of the PFC stage, wherein the average duty cycle is linearly related to an input voltage of the power supply device, and the compensation voltage is linearly related to the average duty cycle; and A comparator includes a non-inverting input, an inverting input, and an output. The non-inverting input is electrically coupled to the first node, and the inverting input is electrically coupled to an over-temperature protection voltage setting. When the voltage at the non-inverting input falls below the over-temperature protection voltage setting, the output sends a control signal to trigger an over-temperature protection function of the power supply. The voltage compensation module is electrically connected between the first node and a ground terminal, and the second end of the thermistor is electrically connected to the ground terminal.

14. The power supply device as claimed in claim 13, characterized in that, The over-temperature protection circuit also includes a first resistor, which is electrically connected between the first node and the first end of the thermistor.

15. The power supply device as claimed in claim 14, characterized in that, The voltage compensation module is electrically connected between the second terminal of the thermistor and the ground terminal.

16. An over-temperature protection circuit, characterized in that, Applicable to a power supply device, wherein the power supply device includes a PFC stage, the over-temperature protection circuit includes: A constant current source is used to provide a reference current to a first node; A thermistor, wherein the first terminal of the thermistor is electrically connected to the first node, the second terminal of the thermistor is grounded, and the thermistor is a negative temperature coefficient thermistor. A voltage compensation module generates a corresponding compensation voltage based on a switch drive signal and an average duty cycle of the PFC stage, wherein the average duty cycle is linearly related to an input voltage of the power supply device, and the compensation voltage is linearly related to the average duty cycle; and A comparator includes a first non-inverting input, a second non-inverting input, an inverting input, and an output. The first non-inverting input is electrically coupled to a first node, the second non-inverting input is electrically coupled to the output of a voltage compensation module, and the inverting input is electrically coupled to an over-temperature protection voltage setting. When the sum of the voltages at the first and second non-inverting inputs is lower than the over-temperature protection voltage setting, the output outputs a control signal to trigger an over-temperature protection function of the power supply device.

17. The over-temperature protection circuit as described in claim 16, characterized in that, It also includes a first resistor, wherein the first resistor is electrically connected between the first node and the first end of the thermistor.

18. The over-temperature protection circuit as described in claim 16, characterized in that, The voltage compensation module receives the switch drive signal and outputs the compensation voltage corresponding to the switch drive signal.

19. The over-temperature protection circuit as described in claim 16, characterized in that, The resistance of the thermistor corresponds to the desired protection temperature of the power supply device. Under different input voltages, the magnitude of the compensation voltage depends on the steady-state operating temperature of the heating element in the power supply device corresponding to the desired protection temperature.

20. The over-temperature protection circuit as described in claim 19, characterized in that, The input voltage has an upper limit and a lower limit. When the input voltage is equal to the upper limit, the heating element in the power supply device corresponds to a first steady-state operating temperature. When the input voltage is equal to the lower limit, the heating element in the power supply device corresponds to a second steady-state operating temperature. The first steady-state operating temperature and the second steady-state operating temperature have a temperature difference. Under any input voltage, the difference between the desired protection temperature and the steady-state operating temperature is within a target temperature range, which depends on the temperature difference.

21. The over-temperature protection circuit as described in claim 20, characterized in that, The target temperature range is 5~15°C.

22. The over-temperature protection circuit as described in claim 19, characterized in that, The compensation voltage is zero under no-load conditions, and the desired protection temperature under no-load conditions is higher than the steady-state operating temperature at any of the input voltages.

23. The over-temperature protection circuit as described in claim 19, characterized in that, The power supply device also includes a DC / DC conversion stage, the input of which is electrically coupled to the output of the PFC stage, and the heating element includes the magnets and switching transistors of the PFC stage and the DC / DC conversion stage respectively.

24. A power supply device, characterized in that, Include: A PFC stage and a DC / DC conversion stage, wherein the input of the DC / DC conversion stage is electrically coupled to the output of the PFC stage; and An over-temperature protection circuit includes: A constant current source is used to provide a reference current to a first node; A thermistor, wherein the first terminal of the thermistor is electrically connected to the first node, the second terminal of the thermistor is grounded, and the thermistor is a negative temperature coefficient thermistor. A voltage compensation module generates a corresponding compensation voltage based on a switch drive signal and an average duty cycle of the PFC stage, wherein the average duty cycle is linearly related to an input voltage of the power supply device, and the compensation voltage is linearly related to the average duty cycle; and A comparator includes a first non-inverting input, a second non-inverting input, an inverting input, and an output. The first non-inverting input is electrically coupled to the first node, the second non-inverting input is electrically coupled to the output of the voltage compensation module, and the inverting input is electrically coupled to an over-temperature protection voltage setting. When the sum of the voltages at the first and second non-inverting inputs is lower than the over-temperature protection voltage setting, the output outputs a control signal to trigger an over-temperature protection function of the power supply device.

25. The power supply device as claimed in claim 24, characterized in that, The over-temperature protection circuit also includes a first resistor, wherein the first resistor is electrically connected between the first node and the first end of the thermistor.

Images