CN117691546A

CN117691546A - Over-temperature protection circuit and power supply device applicable to same

Info

Publication number: CN117691546A
Application number: CN202211073706.1A
Authority: CN
Inventors: 马克华; 张海涛; 许道飞
Original assignee: Delta Electronics Shanghai Co Ltd
Current assignee: Delta Electronics Shanghai Co Ltd
Priority date: 2022-09-02
Filing date: 2022-09-02
Publication date: 2024-03-12

Abstract

The invention provides an over-temperature protection circuit and a power supply device applicable to the over-temperature protection circuit, wherein the over-temperature protection circuit is applicable to the power supply device comprising a PFC stage and comprises a constant current source, a thermistor, a voltage compensation module and a comparator. The first end of the thermistor is electrically connected to the first node, and the thermistor is a negative temperature coefficient thermistor. The voltage compensation module generates corresponding compensation voltage according to a switch driving signal of the PFC stage and an average duty ratio, wherein the average duty ratio is in linear relation with the input voltage of the power supply device, and the compensation voltage is in linear relation with the average duty ratio. The comparator is used for comparing the voltage on the non-inverting input end with the over-temperature protection voltage set value, and outputting a signal to trigger the over-temperature protection function when the voltage on the non-inverting input end is lower than the over-temperature protection voltage set value.

Description

Over-temperature protection circuit and power supply device applicable to same

Technical Field

The present invention relates to an over-temperature protection circuit and a power supply device suitable for the same, and more particularly, to an over-temperature protection circuit capable of improving reliability of an over-temperature protection function and a power supply device suitable for the same.

Background

In the existing consumer electronic power supply, the input voltage range is generally defined between 90 and 264Vac to adapt to the power grid requirements of different countries and regions, and a PFC (power factor correction) circuit is required to be additionally arranged for the power supply with the power more than 75W. Generally, PFC circuits generally employ boost PFC (Boost PFC), which is characterized by a low efficiency at low voltage inputs and a high efficiency at high voltage inputs. At the same output power, this feature will result in a higher part temperature at low pressure inputs than at high pressure inputs.

Conventionally, an over-temperature protection function is realized by using a thermistor, and when over-temperature protection is triggered, the resistance of the thermistor is mostly a fixed value, that is, the protection temperature is fixed. Taking a power supply with the power of 230W as an example, the temperature of the whole part at the input of 90Vac is about 10 ℃ higher than the temperature of the whole part at the input of 264Vac in the steady state operation, and the protection temperature is about 10 ℃ higher than the temperature at the steady state operation of the system for the existing over-temperature protection function. If the protection temperature is set based on the 90Vac input, the protection temperature will be about 20 ℃ higher than the overall part temperature at 264Vac input, resulting in the possibility that the over-temperature protection function may not be triggered when the part is overheated. If the protection temperature is set based on 264Vac input, the protection temperature is approximately equal to the temperature of the whole part at 90Vac input, which causes false triggering of the over-temperature protection function and cannot substantially play a role in over-temperature protection. As can be seen from this, in the conventional method, the over-temperature protection function cannot be applied to different input voltage conditions at the same time, resulting in a decrease in the reliability of the over-temperature protection function.

Therefore, it is an urgent need to design an over-temperature protection circuit and a power supply device suitable for the over-temperature protection circuit, which can improve the prior art.

Disclosure of Invention

The invention aims to provide an over-temperature protection circuit and a power supply device applicable to the over-temperature protection circuit, so that the over-temperature protection function has different trigger temperatures under different input voltages. Therefore, the over-temperature protection function is suitable for different input voltage conditions, so that the reliability of the over-temperature protection function is improved.

In order to achieve the above object, the present invention provides an over-temperature protection circuit suitable for a power supply device including a 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 is used for providing reference current to the first node. The first end of the thermistor is electrically connected to the first node, and the thermistor is a negative temperature coefficient thermistor. The voltage compensation module generates corresponding compensation voltage according to a switch driving signal of the PFC stage and an average duty ratio, wherein the average duty ratio is in linear relation with the input voltage of the power supply device, and the compensation voltage is in linear relation with the average duty ratio. The comparator comprises a normal phase input end, an opposite phase input end and an output end, wherein the normal phase input end is electrically coupled to the first node, the opposite phase input end is electrically coupled to an over-temperature protection voltage set value, and when the voltage of the normal phase input end is lower than the over-temperature protection voltage set value, the output end outputs a control signal so as to trigger the over-temperature protection function of the power supply device.

In order to achieve the above objective, 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 an input terminal of the DC/DC conversion stage is electrically coupled to an 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 is used for providing reference current to the first node. The first end of the thermistor is electrically connected to the first node, and the thermistor is a negative temperature coefficient thermistor. The voltage compensation module generates corresponding compensation voltage according to a switch driving signal of the PFC stage and an average duty ratio, wherein the average duty ratio is in linear relation with the input voltage of the power supply device, and the compensation voltage is in linear relation with the average duty ratio. The comparator comprises a normal phase input end, an opposite phase input end and an output end, wherein the normal phase input end is electrically coupled to the first node, the opposite phase input end is electrically coupled to an over-temperature protection voltage set value, and when the voltage of the normal phase input end is lower than the over-temperature protection voltage set value, the output end outputs a control signal so as to trigger the over-temperature protection function of the power supply device.

In order to achieve the above objective, the present invention further provides an over-temperature protection circuit suitable for a power supply device including a 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 is used for providing reference current to the first node. The first end of the thermistor is electrically connected to the first node, and the thermistor is a negative temperature coefficient thermistor. The voltage compensation module generates corresponding compensation voltage according to a switch driving signal of the PFC stage and an average duty ratio, wherein the average duty ratio is in linear relation with the input voltage of the power supply device, and the compensation voltage is in linear relation with the average duty ratio. The comparator comprises a first normal phase input end, a second normal phase input end, an opposite phase input end and an output end, wherein the first normal phase input end is electrically coupled to the first node, the second normal phase input end is electrically coupled to the output end of the voltage compensation module, the opposite phase input end is electrically coupled to an over-temperature protection voltage set value, and when the sum of the voltage of the first normal phase input end and the voltage of the second normal phase input end is lower than the over-temperature protection voltage set value, the output end outputs a control signal to trigger the over-temperature protection function of the power supply device.

In order to achieve the above objective, 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 an input terminal of the DC/DC conversion stage is electrically coupled to an 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 is used for providing reference current to the first node. The first end of the thermistor is electrically connected to the first node, and the thermistor is a negative temperature coefficient thermistor. The voltage compensation module generates corresponding compensation voltage according to a switch driving signal of the PFC stage and an average duty ratio, wherein the average duty ratio is in linear relation with the input voltage of the power supply device, and the compensation voltage is in linear relation with the average duty ratio. The comparator comprises a first normal phase input end, a second normal phase input end, an opposite phase input end and an output end, wherein the first normal phase input end is electrically coupled to the first node, the second normal phase input end is electrically coupled to the output end of the voltage compensation module, the opposite phase input end is electrically coupled to an over-temperature protection voltage set value, and when the sum of the voltage of the first normal phase input end and the voltage of the second normal phase input end is lower than the over-temperature protection voltage set value, the output end outputs a control signal to trigger the over-temperature protection function of the power supply device.

Drawings

FIG. 1A is a schematic diagram of an over-temperature protection circuit according to an embodiment of the present invention;

fig. 1B is a schematic circuit diagram of a variation of the over-temperature protection circuit of fig. 1A;

fig. 2 is a schematic circuit diagram of PFC stage and DC/DC conversion stage of a power supply device according to an embodiment of the present invention;

FIG. 3 illustrates a circuit configuration of one embodiment of the voltage compensation module of FIG. 1B;

fig. 4 and 5A illustrate two embodiments when a PFC IC of a PFC stage of a power supply device performs part of the functions in an over-temperature protection circuit;

FIG. 5B illustrates a variation of FIG. 5A;

fig. 6 illustrates one embodiment of the voltage compensation module of fig. 5A and 5B.

[ symbolic description ]

1: over-temperature protection circuit

2: power supply device

11: constant current source

R1: first resistor

A: first node

NTC: thermistor with high temperature resistance

12. 12a: voltage compensation module

121: average sampling module

122: compensation coefficient generation module

Vc: compensation voltage

13. 13a: comparator with a comparator circuit

Iref: reference current

21: PFC stage

Vgs: switch driving signal

Vin: input voltage

Votp: over-temperature protection voltage set point

22: DC/DC conversion stage

Q1: switch tube

R2: second resistor

R3: third resistor

C1: capacitance device

211：PFC IC

R4, R5, R6, R7: resistor

Detailed Description

Some exemplary embodiments embodying features and advantages of the present invention will be described in detail in the following description. It will be understood that the invention is capable of modification in various other forms without departing from the scope of the invention, and that the description and illustrations herein are intended to be exemplary in nature and not to be limiting.

Fig. 1A is a schematic circuit diagram of an over-temperature protection circuit according to an embodiment of the present invention, and fig. 2 is a schematic circuit diagram 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 fig. 1A and 2, the over-temperature protection circuit 1 is applicable to the power supply device 2, and in some embodiments, the over-temperature protection circuit 1 may also be included in the power supply device. The over-temperature protection circuit 1 includes a constant current source 11, a thermistor NTC, a voltage compensation module 12, and a comparator 13. The constant current source 11 is used to provide a reference current Iref to the first node a. The 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 the switch driving signal Vgs and the average duty ratio of the PFC stage 21 in the power supply device 2, wherein the average duty ratio is in a linear relationship with the 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 cycle is in a linear relationship with the input voltage Vin of the power device 2, and the compensation voltage Vc is proportional to the average duty cycle, but not limited thereto. In some embodiments, the voltage compensation module 12 obtains the average duty cycle by sampling the switch drive signal Vgs, and the compensation voltage Vc is equal to the product of the high level voltage value of the switch drive signal Vgs and the average duty cycle and the compensation coefficient. The comparator 13 is configured to compare the voltage sum of the voltage on the thermistor NTC and the compensation voltage Vc with the over-temperature protection voltage set value Votp, and output a control signal when the voltage sum is lower than the over-temperature protection voltage set value Votp (i.e. when vc+iref is equal to Rntc < Votp), so as to trigger the over-temperature protection function of the power supply device 2, where Rntc is the resistance value of the thermistor NTC.

Therefore, under the same load, if the input voltage Vin is different, the switch driving signal Vgs and the average duty ratio will be changed accordingly, so that the compensation voltage Vc generated by the voltage compensation module 12 is changed. Because the compensation voltage Vc changes, the resistance value of the thermistor NTC and the corresponding temperature are also different when the over-temperature protection function is triggered. For example, when the average duty ratio is in a linear relationship with the input voltage Vin of the power supply device 2 and the compensation voltage Vc is in direct proportion to the average duty ratio, if the input voltage Vin changes from high voltage to low voltage, the average duty ratio and the compensation voltage Vc rise, so that the resistance of the thermistor NTC decreases and the corresponding temperature rises when the overheat protection function is triggered. Therefore, when the steady-state operation temperature of the heating element in the power supply device 2 increases as the input voltage Vin decreases, the temperature of the thermistor NTC at the time of triggering the over-temperature protection function correspondingly increases, so that the over-temperature protection function can still function. From this, it can be seen that the over-temperature protection circuit 1 of the present invention is suitable for different input voltage conditions, thereby improving the reliability of the over-temperature protection function. On the other hand, the invention realizes the over-temperature protection function suitable for a wide AC input voltage range. In some embodiments, as shown in fig. 1B, the over-temperature protection circuit 1 further includes a first resistor R1, a first end of the first resistor R1 is electrically connected to the first node a, and a first end of the thermistor NTC is electrically connected to a second end of the first resistor R1. By setting the first resistor R1, the resistance value of the thermistor NTC can be adjusted more easily to realize 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 the over-temperature protection voltage set value Votp, and output a control signal when the sum of the voltages is lower than the over-temperature protection voltage set value Votp (i.e. when vc+iref (r1+rntc) < Votp) to trigger the over-temperature protection function of the power supply device 2

In some embodiments, as shown in fig. 2, the power supply device 2 further includes a DC/DC conversion stage 22, wherein an input terminal of the DC/DC conversion stage 22 is electrically coupled to an output terminal of the PFC stage 21. In the embodiment shown in fig. 2, the switch driving signal Vgs of the PFC stage 21 and the gate driving signal of the switching transistor Q1 of the PFC stage 21 have the average duty ratio. In addition, the circuit structure of the power supply device 2 shown in fig. 2 is only an example, and the power supply device of the present invention is not limited thereto. The PFC stage of the power supply device includes, but is not limited to, a Boost PFC, a totem pole PFC, a Dual Boost PFC, or a three-phase PFC, and the DC/DC conversion stage of the power supply device includes, but is not limited to, a flyback circuit, an LLC circuit, an asymmetric half-bridge circuit, a forward circuit, an active clamp flyback circuit, or a buck circuit. 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.

As shown in fig. 1A and fig. 2, in some embodiments, the temperature corresponding to the resistance value of the thermistor NTC is the desired protection temperature of the power device 2, and the magnitude of the compensation voltage Vc is dependent on the steady-state operation temperature of the heating element in the power device 2 corresponding to the desired protection temperature under different input voltages Vin, wherein the heating element includes the magnetic components and the switching tube of each of the PFC stage 21 and the DC/DC conversion stage 22.

In some embodiments, the input voltage Vin has an upper limit and a lower limit. When the input voltage Vin is equal to the upper limit value, the heating element in the power supply device 2 corresponds to a first steady-state operation temperature; when the input voltage Vin is equal to the lower limit value, the heating element in the power 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 is dependent 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 ℃.

It should be noted that the compensation voltage Vc is zero when no load is applied, and the desired protection temperature is higher than the steady-state operation temperature at any input voltage Vin when no load is applied.

Fig. 3 illustrates a circuit configuration of one embodiment of the voltage compensation module 12 of fig. 1B. In some embodiments, as shown in fig. 3, two ends of the voltage compensation module 12 are electrically connected to a second end of the thermistor NTC and a ground end, respectively, and include a second resistor R2, a third resistor R3, and a capacitor C1. The second end of the thermistor NTC is electrically connected to the first end of the second resistor R2, the first end of the third resistor R3 and the first end of the capacitor C1, the second end of the second resistor R2 and the second end of the capacitor C1 are grounded, and the second end of the third resistor R3 receives the switch driving signal Vgs. In this embodiment, the compensation voltage Vc is equal to the product of the high level voltage value of the switch driving signal Vgs and the average duty cycle and the compensation coefficient, and the compensation coefficient depends on the resistance of the second resistor R2, the resistance of the third resistor R3 and the capacitance of the capacitor C1. It should be noted that the embodiment of the voltage compensation module 12 of the present invention is not limited to the embodiment shown in fig. 3, and only needs to generate the appropriate compensation voltage Vc corresponding to different switch driving signals Vgs and average duty ratios. In addition, in this embodiment, the comparator 13 includes a non-inverting input terminal electrically coupled to the first node a, an inverting input terminal electrically coupled to the over-temperature protection voltage set-point Votp, and an output terminal. When the voltage at the non-inverting input terminal is lower than the over-temperature protection voltage set value Votp, the output terminal outputs a control signal to trigger the over-temperature protection function of the power supply device 2.

In general, in the power device 2, the heating element has a steady-state operation temperature corresponding to the upper and lower limit values of the input voltage Vin, and the invention can set a desired protection temperature corresponding to the steady-state operation temperature, and look up a table to obtain the resistance value of the corresponding thermistor NTC, thereby designing each parameter in the over-temperature protection circuit 1. Specific design flows are illustrated in fig. 2 and 3.

Assuming that the upper limit value and the lower limit value of the input voltage Vin are 264Vac and 90Vac, respectively, the expected protection temperatures when the input voltage Vin is 264Vac and 90Vac are set according to the circuit topology of the power supply device 2 are 103 ℃ and 113 ℃, respectively, the resistance values of the thermistor NTC corresponding to 103 ℃ and 113 ℃ are obtained after table 1 is checked to be 4.71kΩ and 3.43kΩ respectively (the corresponding relation between the resistance value and the temperature can be checked by the specification of the thermistor).

TABLE 1

Temperature (. Degree. C.)	Rmax.(kΩ)	Rnor.(kΩ)	Rmin.(kΩ)
				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

The PFC stage 21 of fig. 2 has the following relationship in terms of volt-second balance:

Vin*D＝(Vout-Vin)(1-D) (1)

Vin＝Vout(1-D) (2)

where Vin is denoted as the instantaneous value of the input voltage, vout is denoted as the output voltage of the PFC stage 21, and D is the duty cycle when the input voltage is instantaneous. The average value of the two sides of the equation (2) can be obtained:

Vin_avg＝Vout(1-Davg) (3)

where vin_avg represents the average value of the input voltage and Davg represents the average duty cycle.

According to the circuit topologies of fig. 2 and 3, the following equations (4) and (5) are satisfied for the parameter design in the circuit:

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

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

where vgs_h is a high level voltage value of the switch driving signal Vgs, davg_90Vac and davg_264Vac are average duty ratios when the input voltage Vin is 90Vac and 264Vac, respectively, and k is a compensation coefficient.

According to the equations (4) and (5), iref and Votp are designed and k and R1 are calculated, so that the over-temperature protection circuit 1 is applicable to the input voltage range of 90 Vac-264 Vac, and the over-temperature protection function can be performed under the extreme condition of the input voltage Vin (i.e. equal to 90Vac or 264 Vac), so that the reliability of the over-temperature protection circuit 1 is improved. For example, in the case where vgs_h= V, davg _90 vac=0.8 and davg_264 vac=0.4, iref=200ua and votp=2v can be designed and k=0.0625 and r1=4.05kΩ can be obtained by calculation according to the foregoing equations (4) and (5).

In addition, in some embodiments, as shown in fig. 2 and 4, the PFC stage 21 in the power supply device 2 further includes a PFC IC 211, and the PFC IC 211 is configured to perform functions of the constant current source 11 and the 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 the reference current Iref. Furthermore, the PFC IC 211 receives the sum of the voltage on the first resistor R1, the voltage on the thermistor NTC, and the compensation voltage Vc through its OTP pin, and determines whether to trigger the over-temperature protection function according to the magnitude relation between the sum of the voltages and the over-temperature protection voltage set value Votp.

In other embodiments, as shown in fig. 2 and 5A, the PFC IC 211 of the PFC stage 21 in the power supply device 2 is configured to perform the functions of the constant current source 11, the voltage compensation module 12a, and the comparator 13a in the over-temperature protection circuit 1. The PFC IC 211 is electrically connected to the first end of the thermistor NTC through its OTP pin, and outputs a reference current Iref, thereby receiving the voltage on the thermistor NTC. Further, the PFC IC 211 samples the switching drive signal Vgs and counts the average duty ratio thereof, thereby generating the compensation voltage Vc. Further, the PFC IC 211 obtains the sum of the voltages on the thermistor NTC and the compensation voltage Vc, and determines whether to trigger the over-temperature protection function according to the magnitude relation between the sum of the voltages and the over-temperature protection voltage set value volp.

In some embodiments, as shown in fig. 5B, the over-temperature protection circuit 1 further includes a first resistor R1, and the first resistor R1 is electrically connected between the OTP pin of the PFC IC 211 and a first end of the first resistor R1. By setting the first resistor R1, the resistance value of the thermistor NTC can be adjusted more easily to realize over-temperature protection. In this case, the OTP pin of the PFC IC 211 receives the voltage on the first resistor R1 and the voltage on the thermistor NTC, and the PFC IC 211 determines whether to trigger the over-temperature protection function according to the magnitude relation between the voltage on the first resistor R1, the voltage on the thermistor NTC, the voltage of the compensation voltage Vc, and the over-temperature protection voltage set value Votp.

In the embodiment shown in fig. 5A and 5B, the comparator 13a includes a first positive input terminal electrically coupled to the first node a, a second positive input terminal electrically coupled to the output terminal of the voltage compensation module 12, an inverting input terminal electrically coupled to the over-temperature protection voltage set-point volp, and an output terminal. When the sum of the voltage of the first non-inverting input terminal and the voltage of the second non-inverting input terminal is lower than the over-temperature protection voltage set value Votp, the output terminal outputs a control signal to trigger the over-temperature protection function of the power supply device 2. In addition, in the embodiment shown in fig. 5, the voltage compensation module 12a includes an average value sampling module 121 and a compensation coefficient generating module 122. The average sampling module 121 performs average sampling of the switch driving 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 the compensation coefficient k generated thereby to generate and output the compensation voltage Vc.

Fig. 6 illustrates an embodiment of the voltage compensation module 12a in fig. 5A and 5B, and it should be noted that the specific embodiment of the voltage compensation module 12a is not limited thereto. As shown in fig. 6, the average sampling module 121 is implemented by a low-pass filter, where the cut-off frequency of the low-pass filter is less than 0.5fc, where fc is the input voltage power frequency. The compensation coefficient generation module 122 is implemented by a homodromous proportional operational amplifier circuit, and the compensation coefficient k can be adjusted by adjusting the resistance values of the resistors R4, R5, R6 and R7 in the homodromous proportional operational amplifier circuit. In the embodiment shown in fig. 6, k=r5 (r6+r7)/[ r6 (r4+r5) ].

In summary, the present invention provides an over-temperature protection circuit and a power supply device thereof, which enable the over-temperature protection function to have different trigger temperatures under different input voltages. Therefore, the over-temperature protection function is suitable for different input voltage conditions, so that the reliability of the over-temperature protection function is improved.

It should be noted that the above-mentioned preferred embodiments are only presented for illustrating the invention, and that the invention is not limited to the described embodiments, the scope of which is defined by the appended claims. And the invention may be modified in various ways by those skilled in the art without departing from the scope of the invention as set forth in the appended claims.

Claims

1. An over-temperature protection circuit, suitable for a power supply device, wherein the power supply device comprises a PFC stage, the over-temperature protection circuit comprising:

a constant current source for providing a reference current to a first node;

a thermistor, wherein a first end 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 according to a switch driving signal and an average duty ratio of the PFC stage, wherein the average duty ratio is in a linear relation with an input voltage of the power supply device, and the compensation voltage is in a linear relation with the average duty ratio; and

the comparator comprises a normal phase input end, an opposite phase input end and an output end, wherein the normal phase input end is electrically coupled to the first node, the opposite phase input end is electrically coupled to an over-temperature protection voltage set value, and when the voltage of the normal phase input end is lower than the over-temperature protection voltage set value, the output end outputs a control signal to trigger an over-temperature protection function of the power supply device.

2. The over-temperature protection circuit of claim 1, further comprising a first resistor, wherein the first resistor is electrically connected between the first node and the first end of the thermistor.

3. The overheat protection circuit of claim 1, wherein the voltage compensation module is electrically connected to the second terminal of the thermistor and to the ground terminal.

4. The overheat protection circuit of claim 3, wherein the voltage compensation module comprises a second resistor, a third resistor and a capacitor, wherein the second end of the thermistor is electrically connected to the first end of the second resistor, the first end of the third resistor and the first end of the capacitor, the second end of the second resistor and the second end of the capacitor are grounded, and the second end of the third resistor receives the switch driving signal.

5. The over-temperature protection circuit of claim 4, wherein the compensation voltage is equal to a product of a high voltage value of the switch driving signal and the average duty cycle and a compensation coefficient.

6. The over-temperature protection circuit of claim 5, wherein the voltage compensation module obtains the average duty cycle by sampling the switch drive signal.

7. The over-temperature protection circuit of claim 5, wherein the compensation factor is dependent on the resistance of the second resistor and the resistance of the third resistor and the capacitance of the capacitor.

8. The over-temperature protection circuit of claim 1, wherein the resistance of the thermistor corresponds to a desired protection temperature of the power device, and the magnitude of the compensation voltage is dependent on a steady-state operating temperature of a heating element in the power device corresponding to the desired protection temperature at different input voltages.

9. The over-temperature protection circuit of claim 8, wherein the input voltage has an upper limit and a lower limit, and the heating element in the power supply device corresponds to a first steady-state operating temperature when the input voltage is equal to the upper limit; when the input voltage is equal to the lower limit value, the heating element in the power supply device corresponds to a second steady-state operation temperature, and the first steady-state operation temperature and the second steady-state operation temperature have a temperature difference value; at any of the input voltages, the difference between the desired protection temperature and the steady-state operating temperature is within a target temperature range, the target temperature range being dependent on the temperature difference.

10. The over-temperature protection circuit of claim 9, wherein the target temperature range is 5-15 ℃.

11. The over-temperature protection circuit of claim 8, wherein the compensation voltage is zero when idle and the desired protection temperature is higher than the steady-state operating temperature at any one of the input voltages when idle.

12. The overheat protection circuit of claim 8, wherein the power supply device further comprises a DC/DC conversion stage, an input terminal of the DC/DC conversion stage is electrically coupled to an output terminal of the PFC stage, and the heating element comprises magnetic pieces and switching tubes of the PFC stage and the DC/DC conversion stage, respectively.

13. A power supply device, comprising:

a PFC stage and a DC/DC conversion stage, wherein an input end of the DC/DC conversion stage is electrically coupled to an output end of the PFC stage; and

an over-temperature protection circuit comprising:

a constant current source for providing a reference current to a first node;

14. The power supply device of claim 13, wherein the over-temperature protection circuit further comprises a first resistor electrically connected between the first node and the first end of the thermistor.

15. The power device of claim 14, wherein the voltage compensation module is electrically connected to the second terminal of the thermistor and to ground.

16. An over-temperature protection circuit, suitable for a power supply device, wherein the power supply device comprises a PFC stage, the over-temperature protection circuit comprising:

a constant current source for providing a reference current to a first node;

the comparator comprises a first normal phase input end, a second normal phase input end, an opposite phase input end and an output end, wherein the first normal phase input end is electrically coupled to the first node, the second normal phase input end is electrically coupled to the output end of the voltage compensation module, the opposite phase input end is electrically coupled to an over-temperature protection voltage set value, and when the sum of the voltage of the first normal phase input end and the voltage of the second normal phase input end is lower than the over-temperature protection voltage set value, the output end outputs a control signal to trigger an over-temperature protection function of the power supply device.

17. The overheat protection circuit of claim 16, further comprising 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 of claim 16, wherein the second terminal of the thermistor is grounded.

19. The over-temperature protection circuit of claim 16, wherein the voltage compensation module receives the switch driving signal and outputs the compensation voltage corresponding to the switch driving signal.

20. The over-temperature protection circuit of claim 16, wherein the resistance of the thermistor corresponds to a desired protection temperature of the power device, and the magnitude of the compensation voltage is dependent on a steady-state operating temperature of a heating element in the power device corresponding to the desired protection temperature at different input voltages.

21. The overheat protection circuit of claim 20, wherein the input voltage has an upper limit value and a lower limit value, and the heating element in the power supply device corresponds to a first steady-state operating temperature when the input voltage is equal to the upper limit value; when the input voltage is equal to the lower limit value, the heating element in the power supply device corresponds to a second steady-state operation temperature, and the first steady-state operation temperature and the second steady-state operation temperature have a temperature difference value; at any of the input voltages, the difference between the desired protection temperature and the steady-state operating temperature is within a target temperature range, the target temperature range being dependent on the temperature difference.

22. The over-temperature protection circuit of claim 21, wherein the target temperature range is 5-15 ℃.

23. The over-temperature protection circuit of claim 20, wherein the compensation voltage is zero when idle and the desired protection temperature is higher than the steady-state operating temperature at any one of the input voltages when idle.

24. The overheat protection circuit of claim 20 wherein the power supply device further comprises a DC/DC conversion stage, the input of the DC/DC conversion stage being electrically coupled to the output of the PFC stage, the heating element comprising respective magnetic elements and switching tubes of the PFC stage and the DC/DC conversion stage.

25. A power supply device, comprising:

an over-temperature protection circuit comprising:

a constant current source for providing a reference current to a first node;

26. The power supply device of claim 25, wherein the over-temperature protection circuit further comprises a first resistor, wherein the first resistor is electrically connected between the first node and the first end of the thermistor.

27. The power supply of claim 25 wherein the second end of the thermistor is grounded.