Dynamic over-temperature protection circuit of switching power supply and switching power supply

Abstract

The invention provides a dynamic over-temperature protection circuit of a switching power supply, which is characterized in that a first junction transistor is arranged near a power tube, and a second junction transistor is arranged in a controller; detecting voltage variation generated when different currents respectively flow through the first junction transistor to obtain first voltage variation; detecting the voltage variation generated when different currents respectively flow through the second junction transistor to obtain a second voltage variation, wherein the obtaining time sequences of the first voltage variation and the second voltage variation are the same; and comparing a difference value between the first voltage variation and the second voltage variation with an over-temperature protection threshold value to obtain a dynamic over-temperature detection signal, and when the difference value is greater than the over-temperature protection threshold value, the dynamic over-temperature detection signal is effective, and triggering the switching power supply to perform dynamic over-temperature protection. The method is low in correlation with process errors, high in accuracy of dynamic over-temperature detection and low in cost.

Description

Technical Field

[0001] This invention relates to the field of power electronics, and in particular to a dynamic over-temperature protection circuit for a switching power supply and the switching power supply itself. Background Technology

[0002] Switching power supplies integrate power devices and control chips and are widely used in various fields. For reliable switching power supply design, the effect of temperature must be considered because the SOA (Safe Operating Area) limit of power switching transistors changes significantly with junction temperature. When the junction temperature reaches the critical temperature, the power device may drop below the zero temperature coefficient point. At this point, its impedance is inversely proportional to temperature, which may trigger thermal runaway and cause permanent damage to the device. Therefore, switching power supplies generally integrate temperature protection circuits.

[0003] For power modules where power devices and control chips are packaged together, in certain application scenarios, the power of the power devices may suddenly increase. Due to the characteristics of heat transfer, localized heat accumulation may occur in the power devices, causing their temperature to be much higher than that of the control chip. Therefore, it is necessary to monitor the temperature difference between the power devices and the control chip to detect sudden power changes. This type of over-temperature protection, achieved by monitoring the temperature difference between the power devices and the control chip, is called dynamic over-temperature protection.

[0004] Existing dynamic over-temperature protection technology mainly detects the voltage Vbe of the forward bias PN junction of the power device and the control chip respectively. It utilizes the temperature characteristics of the PN junction and converts the temperature information into a current signal through voltage-to-current conversion. Over-temperature protection is then achieved using a current comparator. Existing dynamic over-temperature protection technologies have the following drawbacks: First, both the temperature detection circuits of the power devices and the control chips introduce offset voltage and gain errors, requiring additional calibration. Second, voltage-to-current circuits typically use resistors for conversion, and resistors also have a temperature coefficient, which can cause the slope of the negative temperature coefficient Vbe voltage to change after conversion, requiring further calibration. Third, due to the different manufacturing processes used in the power devices and control chips, the PN junction voltage Vbe characteristics of the diodes used to detect the power device temperature may differ from those of the diodes / transistors used to detect the control chip temperature. In actual production, temperature scanning of the diodes in both the power devices and the control circuit is required to adjust their Vbe characteristics to be consistent. This places high demands on the testing environment and the number of efuses needed for adjustment, increasing cost and complexity. Summary of the Invention

[0005] The purpose of this invention is to provide a dynamic over-temperature protection circuit for a switching power supply and a switching power supply in general. The solution of this invention has low correlation with process errors, high accuracy in dynamic over-temperature detection, and low cost.

[0006] The present invention also provides a dynamic over-temperature protection circuit for a switching power supply, the switching power supply including a power transistor and a controller, the controller being connected to the control terminal of the power transistor and used to control the switching state of the power transistor, including:

[0007] A first junction transistor and a second junction transistor, wherein the first junction transistor is located near the power transistor and the second junction transistor is located within the controller;

[0008] The first detection module detects the voltage change generated when different currents flow through the first junction transistor to obtain the first voltage change.

[0009] The second detection module detects the voltage change generated when different currents flow through the second junction transistor to obtain the second voltage change.

[0010] The comparator compares the difference between the first voltage change and the second voltage change with an over-temperature protection threshold to obtain a dynamic over-temperature detection signal. When the difference is greater than the over-temperature protection threshold, the dynamic over-temperature detection signal is valid and triggers the switching power supply to perform dynamic over-temperature protection.

[0011] Optionally, the first junction transistor or the second junction transistor is one of a crystal diode or a crystal triode.

[0012] Optionally, the second detection module has the same detection timing as the first detection module.

[0013] Optionally, the over-temperature protection threshold is adjustable, and the dynamic over-temperature protection point of the switching power supply can be adjusted by adjusting the over-temperature protection threshold.

[0014] Optionally, the over-temperature protection threshold is greater than or equal to zero.

[0015] Optionally, the first detection module provides a first current flowing through the first junction transistor to generate a first voltage during a first time period, and provides a second current flowing through the first junction transistor to generate a second voltage during a second time period. The change in the first voltage is obtained based on the difference between the second voltage and the first voltage, where the second current is equal to n times the first current, and n>0.

[0016] Optionally, the second detection module provides a third current flowing through the second junction transistor to generate a third voltage during a first time period, and provides a fourth current flowing through the second junction transistor to generate a fourth voltage during a second time period. The second voltage change is obtained based on the difference between the fourth voltage and the third voltage, and the fourth current is equal to n times the third current.

[0017] Optionally, the non-inverting input of the comparator receives the superposition of a first voltage change and a first bias voltage, and the inverting input of the comparator receives the superposition of a second voltage change and a second bias voltage. The comparator outputs the dynamic over-temperature detection signal.

[0018] The over-temperature protection threshold is associated with the first bias voltage and the second bias voltage.

[0019] Optionally, the first detection module includes a first capacitor, a second capacitor, and a third capacitor. In a first time period, the first capacitor and the first junction transistor are connected in parallel, the first terminal of the third capacitor receives the voltage of the first capacitor, and the second terminal of the third capacitor receives a first bias voltage. In a second time period, the second capacitor and the first junction transistor are connected in parallel, the first terminal of the third capacitor receives the voltage of the second capacitor, and the second terminal of the third capacitor receives the sum of the first voltage change and the first bias voltage.

[0020] Optionally, the second detection module includes a fourth capacitor, a fifth capacitor, and a sixth capacitor. In a first time period, the fourth capacitor and the second junction transistor are connected in parallel. The first terminal of the sixth capacitor receives the voltage of the fourth capacitor, and the second terminal of the sixth capacitor receives a second bias voltage. In a second time period, the fifth capacitor and the second junction transistor are connected in parallel. The first terminal of the sixth capacitor receives the voltage of the fifth capacitor, and the second terminal of the third capacitor receives the sum of the second voltage change and the second bias voltage.

[0021] Optionally, the first bias voltage and / or the second bias voltage can be adjusted.

[0022] The present invention also provides a switching power supply, including a power transistor and a controller, wherein the controller is connected to the control terminal of the power transistor and is used to control the switching state of the power transistor, and further includes any of the above-described dynamic over-temperature protection circuits, wherein the power transistor, the controller and the dynamic over-temperature protection circuit are packaged together.

[0023] Compared with existing technologies, this invention has the following advantages: This invention places a first junction transistor (JT) near the power transistor and a second JT inside the controller. It detects the voltage changes generated when different currents flow through the first JT and the second JT. The difference between these two changes is compared with an over-temperature protection threshold to determine whether dynamic over-temperature protection should be implemented. This invention's dynamic over-temperature detection scheme has low correlation with process errors, avoiding the need for additional adjustments to the PN junction voltage Vbe of the corresponding JT for the power device and control chip, thus reducing costs and improving accuracy. Furthermore, this invention directly acquires and compares the junction voltage of the JT, eliminating the need for a voltage-to-current converter circuit, avoiding the influence of resistance temperature coefficient errors, and further contributing to improved accuracy. Attached Figure Description

[0024] Figure 1 This is a block diagram of the dynamic over-temperature detection circuit of the present invention;

[0025] Figure 2 This is a schematic diagram of an embodiment of the dynamic over-temperature detection circuit of the present invention;

[0026] Figure 3 This is the switching timing diagram of the dynamic over-temperature detection circuit of the present invention. Detailed Implementation

[0027] The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings, but the present invention is not limited to these embodiments. The present invention covers any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of the present invention.

[0028] To provide the public with a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the invention, but those skilled in the art can fully understand the invention without these details.

[0029] The invention is described more specifically in the following paragraphs by way of example with reference to the accompanying drawings. It should be noted that the drawings are in a simplified form and use non-precise proportions, in order to facilitate and clearly illustrate the purpose of the embodiments of the invention.

[0030] In the switching power supply of the present invention, the power transistor and its controller / control chip are packaged together (integrated in one package). In some application scenarios, the power of the switching power supply may suddenly increase. Due to the characteristics of heat transfer, the power transistor will experience local heat accumulation. At this time, the temperature of the power transistor will be much higher than the temperature of the controller. Therefore, it is necessary to monitor the temperature difference between the power transistor and the controller to achieve the purpose of monitoring power sudden changes.

[0031] like Figure 1 The diagram illustrates a block diagram of the dynamic over-temperature detection circuit for the switching power supply of the present invention. It includes a first junction transistor (JT) and a second JT. The first JT is placed near a power transistor, which is used to control, amplify, or reduce the voltage, current, or power of the switching power supply. For example, a MOSFET used for voltage reduction in a buck circuit or for voltage increase in a boost circuit is a power transistor. Since heat from the power transistor is transferred to the first JT, the temperature of the first JT is close to or equal to the temperature of the power transistor. Based on the process and device characteristics of the power transistor, a crystal diode (diode D1 in the diagram) is used for the first JT to facilitate its placement near the power transistor. The temperature of the power transistor is obtained based on the characteristics of the diode's PN junction voltage (i.e., diode voltage) versus temperature. Alternatively, a bipolar junction transistor (BJT) (with two PN junctions, equivalent to two diodes connected together) can also be used. The second JT is located within a controller, which is typically integrated into a chip. This chip is a control chip, and the temperature of the second JT is equal to the temperature of the controller. The second JT can be either a BJT or a crystal diode. Figure 1 The diagram uses transistor Q1 as an example. The controller's temperature is determined based on the characteristic of the transistor's PN junction voltage (i.e., the voltage Vbe between the base / collector and emitter) versus temperature. (Refer to...) Figure 1 In the dynamic over-temperature detection circuit, except for the first junction transistor, the other components and circuits are integrated into the controller.

[0032] This invention provides different magnitudes of current, such as I1 and n*I1 (n > zero), flowing through diode D1. These different currents generate different junction voltages across the diode, such as a first voltage V1 and a second voltage V2. The change in the first voltage ΔV is obtained based on the difference between the first and second voltages. BE _mos = V1 - V2; This invention also provides different magnitudes of current, such as I2 and n*I2, flowing through transistor Q1. These different currents generate different junction voltages on the transistor, such as a third voltage V3 and a fourth voltage V4. The difference between the third and fourth voltages is used to obtain the second voltage change ΔV. BE _ic = V3 - V4. Given the junction voltage V of the three electrodes... BE With collector current I C The relationship is:

[0033]

[0034] Where k is the Boltzmann constant, Ic is the forward current (conduction current), Is is the reverse saturation current, q is the junction charge, and T is the junction temperature. Assuming I1 = I3 = (n+1)*I, I2 = I4 = I, and n > 0, then:

[0035]

[0036] Set an over-temperature protection threshold Vth, and set ΔV BE _mos and ΔV BE The difference in _ic is compared with the threshold Vth, when When the temperature difference between the power transistor (T1) and the controller (T2) reaches the set threshold (q), *Vth / k * ln ( n+1 ) When Vth is set to zero, a dynamic over-temperature signal is generated. BE _mos is greater than ΔV BE When _ic is displayed, it indicates that the temperature T1 of the power transistor is greater than the temperature T2 of the controller. By setting the over-temperature protection threshold, an over-temperature protection point is set. That is, when the difference between the power transistor temperature and the controller temperature reaches the set temperature, it indicates that the input / output power suddenly increases to a certain value, and dynamic over-temperature protection, i.e., over-power protection, is required.

[0037] Based on the dynamic over-temperature protection concept described above, the dynamic over-temperature protection block diagram of this invention is shown below. Figure 1 It includes a first junction transistor D1, a second junction transistor Q1, a first current source module, a second current source module, a first detection module, a second detection module, and a comparator U1. The first current source module generates currents I1 and n*I1 that flow through the first junction transistor. The first detection module detects the voltage across the first junction transistor and obtains the voltage difference ΔV. BE _mos, the first detection module can detect this voltage difference ΔV BE _mos _ By superimposing a bias voltage Vn, we obtain ΔV. BE The second current source module generates currents I2 and n*I2, which flow through the second junction transistor. The second detection module detects the voltage across the second junction transistor and obtains the voltage difference ΔV. BE _ic, the first detection module can detect this voltage difference ΔV BE A bias voltage Vp is superimposed on _ic to obtain ΔV BE _ic+Vp. Comparator U1 will convert the voltage ΔV BE _mos+Vn and voltage ΔV BE The comparison is performed by _ic+Vp, and the output comparison signal VT is generated when ΔV... BE _mos+Vn>ΔV BE When _ic+Vp, that is, ΔV BE _mos-ΔV BE_ic>Vp-Vn, Vp-Vn=Vth, the comparison signal VT changes from low level invalid to high level valid. According to the above analysis, this indicates that the difference between the power transistor temperature and the controller temperature has reached the set threshold, that is, the system is dynamically over-temperature, triggering dynamic over-temperature protection, such as turning off the power transistor for a period of time.

[0038] like Figure 2 The diagram shown illustrates the schematic of the dynamic over-temperature detection circuit of the present invention. Figure 1 Based on the schematic block diagram, the given embodiment circuit diagram shows that the first current source module includes a first current source and a second current source. The positive terminal of diode D1 is connected to the first current source and the second current source via switch S1. The first current source outputs a current I1, and the second current source outputs a current n*I1, where n>0. The first detection module detects the voltage V1 generated by the current (n+1)*I1 flowing through diode D1 and the voltage V2 generated by the current I1 flowing through diode D1, and obtains the difference between V1-V2-Vn, where Vn is the set first bias voltage. Specifically, the first detection module includes capacitors C1, C2, and C3, and a first voltage source. The first voltage source outputs a voltage Vn. Capacitor C1 is connected to the anode of diode D1 via switch S6 and to the first terminal of capacitor C3 via switch S7. Capacitor C2 is connected to the anode of diode D1 via switch S3 and to the first terminal of capacitor C3 via switch S4. The second terminal of capacitor C3 is connected to the first voltage source via switch S5, and the output voltage of the second terminal of capacitor C3 is V4. The second current source module includes a third current source and a fourth current source. The base and collector of transistor Q1 are connected. The collector of transistor Q1 is connected to the third current source and to the fourth current source via switch S2. The output current of the third current source is I2, and the output current of the fourth current source is n*I2. The ratio n of the output current of the fourth current source to the output current of the third current source is the same as the ratio n of the output current of the second current source to the output current of the first current source. Optionally, I2 = I1. The second detection module detects the voltage V5 generated by the current (n+1)*I2 flowing through transistor Q1 and the voltage V6 generated by the current I2 flowing through transistor Q1, and obtains the difference V5-V6-Vp, where Vp is the set second bias voltage. Specifically, the second detection module includes capacitors C4, C5, and C6, and a second voltage source. The second voltage source outputs a voltage of Vp. Capacitor C4 is connected to the collector of transistor Q1 via switch S11 and to the first terminal of capacitor C6 via switch S12. Capacitor C5 is connected to the collector of transistor Q1 via switch S8 and to the first terminal of capacitor C6 via switch S9. The second terminal of capacitor C6 is connected to the second voltage source via switch S10, and the output voltage of the second terminal of capacitor C6 is V8. Comparator U1 compares voltage V4 with voltage V8 to determine whether the temperature difference between the power transistor and the controller reaches the set temperature threshold.

[0039] Combination Figure 3The waveform diagram of the switch signal is shown below. Analysis. Figure 1 The circuit operation mode, Figure 2 In the circuit, a high-level signal is valid, and the corresponding switch is turned on; a low-level signal is invalid, and the corresponding switch is turned off. Switches S1, S2, S6, S7, S11, and S12 are simultaneously turned on and off, as are switches S3, S4, S5, S8, S9, and S10. This ensures that the timing sequence of the power transistor temperature detection circuit and the controller temperature detection circuit is exactly the same, so that the temperatures of the power transistor and the controller can be detected at the same time. For the temperature detection process of the power transistor: When switch S1 is off, the current flowing through diode D1 is I1. At this time, switches S3, S4, and S5 are on, and switches S6 and S7 are off. The voltage V2 of capacitor C2 and the voltage V3 at the first terminal of capacitor C3 are equal to the voltage of diode D1. The voltage at the second terminal of capacitor C3 is the output voltage Vn of the first voltage source. The charge on capacitor C3 is Q1 = (V2 - Vn) * C3. When switch S1 is on, the current flowing through diode D1 is (n+1) * I1. At this time, switches S6 and S7 are on, and switches S3, S4, and S5 are off. The voltage V1 of capacitor C1 and the voltage V3 at the first terminal of capacitor C3 are equal to the voltage of diode D1. The voltage at the second terminal of capacitor C3 is V4. The charge on capacitor C3 is Q2 = (V1 - V4) * C3. According to the law of conservation of charge, Q1 = Q2, so V4 = V1 - V2 + Vn, that is, V4 = ΔV BE Given _mos+Vn, and combining the above principle, we get V1-V2=k*T1*ln(n+1) / q, therefore V4=k*T1*ln(n+1) / q+Vn. Thus, V4 can characterize the magnitude of the power transistor temperature T1. For the controller's temperature detection process: When switch S2 is off, the current flowing through transistor Q1 is I2. At this time, switches S8, S9, and S10 are on, and switches S11 and S12 are off. The voltage V6 of capacitor C5 and the voltage V7 at the first terminal of capacitor C6 are equal to the transistor's collector-emitter voltage Vbe. The voltage at the second terminal of capacitor C6 is the output voltage Vp of the second voltage source. The charge on capacitor C6 is Q3=(V6-Vp)*C6. When switch S2 is on, the current flowing through... The current of transistor Q1 is (n+1)*I2. At this time, switches S11 and S12 are open, and switches S8, S9, and S10 are closed. The voltage V5 across capacitor C4 and the voltage V7 across the first terminal of capacitor C6 are equal to the collector-emitter voltage of transistor Q1. The voltage across the second terminal of capacitor C6 is V8. The charge on capacitor C6 is Q4 = (V5 - V8)*C6. According to the law of conservation of charge, Q3 = Q4, therefore V8 = V5 - V6 + Vp, which means V8 = ΔV BE_ic+Vp, combining the above principles, we get V5-V6=k*T2*ln(n+1) / q, therefore V4=k*T2*ln(n+1) / q+Vp, and thus V8 can characterize the magnitude of the controller temperature T2. Furthermore, we have... Comparator U1 compares voltages V4 and V8. When V4 is greater than V8, the comparator output signal is valid, indicating that... This indicates that when the temperature difference between the power transistor and the controller exceeds a set temperature threshold, dynamic over-temperature protection of the switching power supply is triggered. When both Vp and Vn are positive, the magnitude of Vp and Vn (the value of the Vp-Vn difference) sets the temperature threshold Vth. When Vn is positive and Vp is negative, the magnitude of Vp and Vn (the value of the Vp-Vn sum) sets the temperature threshold Vth. Figure 1 In the illustrated embodiment, only the second voltage source can be set without setting the first voltage source, which is equivalent to Vn = 0. The over-temperature protection threshold can also be set by only setting the value of Vp. When neither the first nor the second voltage source is set, V4 is greater than V8, which indicates that the power transistor temperature is greater than the controller temperature. However, an over-temperature threshold is generally set. Dynamic over-temperature protection, i.e., over-power protection, is only triggered when the power transistor temperature is greater than the controller temperature and the temperature difference reaches a certain threshold, i.e., when the change in input power / output power exceeds a certain amount.

[0040] This invention primarily utilizes the temperature characteristics of PN junction voltage changes for over-temperature protection circuit design. This approach has low sensitivity to process errors, essentially depending only on the ratio (n) of the two current sources. The impact can be minimized through layout matching. Therefore, this approach has low correlation with process errors, avoiding the need for additional calibration of the power transistor and controller junction voltages required in traditional solutions. This reduces costs and improves accuracy. Furthermore, this invention directly acquires and compares voltages, eliminating the need for a voltage-to-current converter, thus avoiding the influence of resistance temperature coefficient errors and further contributing to improved accuracy.

[0041] Although the embodiments are described and illustrated separately above, some common technologies are involved. Those skilled in the art can replace and integrate them between the embodiments. If there is any content not explicitly described in one embodiment, then another embodiment that is described can be referred to.

[0042] The embodiments described above do not constitute a limitation on the scope of protection of this technical solution. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the above embodiments should be included within the scope of protection of this technical solution.

Claims

1. A dynamic over-temperature protection circuit for a switching power supply, the switching power supply comprising a power transistor and a controller, the controller being connected to the control terminal of the power transistor for controlling the switching state of the power transistor, characterized in that, include: A first junction transistor and a second junction transistor, wherein the first junction transistor is located near the power transistor and the second junction transistor is located within the controller; The first detection module detects the voltage change generated when different currents flow through the first junction transistor to obtain the first voltage change. The second detection module detects the voltage change generated when different currents flow through the second junction transistor to obtain the second voltage change. The comparator compares the difference between the first voltage change and the second voltage change with an over-temperature protection threshold to obtain a dynamic over-temperature detection signal. When the difference is greater than the over-temperature protection threshold, the dynamic over-temperature detection signal is valid and triggers the switching power supply to perform dynamic over-temperature protection.

2. The dynamic over-temperature protection circuit according to claim 1, characterized in that: The first junction transistor or the second junction transistor is one of a crystal diode or a crystal triode.

3. The dynamic over-temperature protection circuit according to claim 1, characterized in that: The second detection module has the same detection timing as the first detection module.

4. The dynamic over-temperature protection circuit according to claim 1, characterized in that: The over-temperature protection threshold is adjustable, and by adjusting the over-temperature protection threshold, the dynamic over-temperature protection point of the switching power supply can be adjusted.

5. The dynamic over-temperature protection circuit according to claim 4, characterized in that: The over-temperature protection threshold is greater than or equal to zero.

6. The dynamic over-temperature protection circuit according to claim 3, characterized in that: The first detection module provides a first current flowing through the first junction transistor to generate a first voltage during a first time period, and provides a second current flowing through the first junction transistor to generate a second voltage during a second time period. The change in the first voltage is obtained based on the difference between the second voltage and the first voltage. The second current is equal to n times the first current, where n>0.

7. The dynamic over-temperature protection circuit according to claim 6, characterized in that: The second detection module provides a third current to flow through the second junction transistor in a first time period to generate a third voltage, and provides a fourth current to flow through the second junction transistor in a second time period to generate a fourth voltage. The change in the second voltage is obtained based on the difference between the fourth voltage and the third voltage, and the fourth current is equal to n times the third current.

8. The dynamic over-temperature protection circuit according to claim 3, characterized in that: The comparator's non-inverting input receives the sum of a first voltage change and a first bias voltage, and its inverting input receives the sum of a second voltage change and a second bias voltage. The comparator outputs the dynamic over-temperature detection signal. The over-temperature protection threshold is associated with the first bias voltage and the second bias voltage.

9. The dynamic over-temperature protection circuit according to claim 6, characterized in that: The first detection module includes a first capacitor, a second capacitor, and a third capacitor. In a first time period, the first capacitor and the first junction transistor are connected in parallel. The first terminal of the third capacitor receives the voltage of the first capacitor, and the second terminal of the third capacitor receives a first bias voltage. In a second time period, the second capacitor and the first junction transistor are connected in parallel. The first terminal of the third capacitor receives the voltage of the second capacitor, and the second terminal of the third capacitor receives the sum of the first voltage change and the first bias voltage.

10. The dynamic over-temperature protection circuit according to claim 7, characterized in that: The second detection module includes a fourth capacitor, a fifth capacitor, and a sixth capacitor. In a first time period, the fourth capacitor and the second junction transistor are connected in parallel. The first terminal of the sixth capacitor receives the voltage of the fourth capacitor, and the second terminal of the sixth capacitor receives a second bias voltage. In a second time period, the fifth capacitor and the second junction transistor are connected in parallel. The first terminal of the sixth capacitor receives the voltage of the fifth capacitor, and the second terminal of the third capacitor receives the sum of the second voltage change and the second bias voltage.

11. The dynamic over-temperature protection circuit according to claim 8, characterized in that: The first bias voltage and / or the second bias voltage are adjustable.

12. A switching power supply, comprising a power transistor and a controller, wherein the controller is connected to the control terminal of the power transistor and is used to control the switching state of the power transistor, characterized in that: It also includes the dynamic over-temperature protection circuit according to any one of claims 1-11, wherein the power transistor, the controller and the dynamic over-temperature protection circuit are packaged together.

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