Method for calculating temperature of IGBT in PFC circuit of air conditioner

Abstract

The application provides a kind of IGBT temperature calculation method in air conditioner PFC circuit, it is related to air conditioning technical field, including obtaining the shell temperature of insulated gate bipolar transistor (IGBT) and the current of IGBT;Combining the fixed switching frequency of IGBT, and the IGBT data manual is obtained, is calculated using formula IGBT temperature.The application does not change the existing hardware circuit, does not increase the cost, only through calculation obtains IGBT temperature;When the temperature exceeds a certain limit, the temperature is reduced by controlling IGBT switch, and it is protected.Further reduce the device failure rate, improve product quality.

Description

Technical Field

[0001] This invention relates to the field of air conditioner technology, and more particularly to the field of air conditioner electronic device control technology. Specifically, it relates to a method for calculating the temperature of IGBTs in an air conditioner PFC circuit. Background Technology

[0002] In current single-phase inverter air conditioners, BOOST PFC (a circuit for power factor correction) is commonly used to improve harmonics, such as... Figure 1 As shown, L1 is a PFC (Power Factor Correction) inductor; V1 is an IGBT (Insulated Gate Bipolar Transistor); VD1 is a rectifier diode (FRD: Fast Recovery Diode); C1 is a bus capacitor; R1 is a bus current sensing resistor; LR1 is the compressor load; R2 is the compressor current sensing resistor; LR2 is the fan load; and R3 is the fan current sensing resistor. Among these components, the compressor and fan modules have internal thermocouples to detect the output temperature. IGBTs and FRDs are passive power devices, with IGBTs generating significant heat. Market feedback indicates numerous failures. Aside from occasional short circuits due to foreign objects or improper installation, most failures are related to abnormal market voltage fluctuations and sudden abnormal heating of the IGBT. Currently, there is no feasible method for calculating IGBT temperature. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a method for calculating IGBT temperature in an air conditioner PFC circuit. Without altering the hardware circuitry, the IGBT temperature is calculated, enabling real-time switching control based on the IGBT temperature to reduce IGBT temperature. This solves the problem of IGBT failure caused by abnormal instantaneous overheating due to abnormal market voltage fluctuations.

[0004] A method for calculating the IGBT temperature in an air conditioner PFC circuit includes:

[0005] Obtain the case temperature of an insulated gate bipolar transistor (IGBT). and IGBT current ;

[0006] Calculate IGBT temperature using formula :

[0007] ;

[0008] in, This refers to the heat dissipation power of the IGBT; The thermal resistance from the IGBT junction to the case; This refers to the collector-emitter voltage of the IGBT. For the IGBT's switching loss; For IGBT turn-off losses; For the fixed switching frequency of IGBT, , , , , Obtained from the IGBT datasheet.

[0009] As a further improvement of the present invention, the case temperature of the IGBT The temperature is obtained by measuring the casing temperature of the compressor drive module IPM.

[0010] As a further improvement of the present invention, when the IGBT type is insulated, =Case temperature of the compressor drive module IPM; when the IGBT type is non-insulated. = Case temperature of compressor drive module IPM + ΔT; ΔT is the temperature difference between the two sides of the IGBT with added insulating gasket.

[0011] As a further improvement of the present invention, the temperature difference ΔT between the two sides of the insulating pad is:

[0012] ;

[0013] in, ; This refers to the thickness of the insulating pad; The thermal conductivity of the insulating gasket; This represents the contact area between the IGBT and the insulating gasket.

[0014] As a further improvement of the present invention, the current of the IGBT... :

[0015] ;

[0016] in, Bus current; This refers to the compressor current. This represents the fan current.

[0017] As a further improvement of the present invention, it also includes correcting the calculated IGBT temperature based on the difference between the casing temperature of the compressor drive module IPM calculated from the output temperature of the compressor IPM module, the temperature difference between the two sides of the insulating gasket, the calculated value of the IGBT temperature and the actual test value of the pre-embedded thermocouple.

[0018] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0019] This invention does not change existing hardware circuitry or increase costs; it simply calculates the IGBT temperature. When the temperature exceeds a certain limit, the IGBT switch is controlled to lower the temperature and protect it. This further reduces device failure rate and improves product quality. Attached Figure Description

[0020] Figure 1 This is a circuit diagram for power factor correction in existing single-phase air conditioner inverter products.

[0021] Figure 2 This is a schematic diagram illustrating the method for calculating IGBT current in an embodiment of the present invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] This embodiment provides a method for calculating the IGBT temperature in an air conditioner PFC circuit. The present invention designs an IGBT temperature calculation formula:

[0024] (1)

[0025] The parameter definitions are shown in Table 1.

[0026] Table 1 Parameter Definitions

[0027]

[0028] In formula (1), , , , All values ​​are given in the IGBT datasheet. To maintain a fixed switching frequency, it is only necessary to know the IGBT current. and shell temperature This allows you to calculate the internal junction temperature of the IGBT.

[0029] Since the bridge rectifier, IGBT, FRD, and compressor drive module (IPM) are all on the same heatsink, which is generally made of aluminum, measurements show that the temperatures of these four components are not significantly different. The IPM has a built-in temperature output, and the case temperature (i.e., the temperature on the heatsink) can be calculated based on its current thermal resistance. IGBTs come in insulated and non-insulated types; non-insulated IGBTs require additional insulating pads.

[0030] For insulated IGBTs, (Case temperature) is comparable to that of the IPM;

[0031] For non-insulated IGBTs, the case temperature needs to be the IPM case temperature plus the temperature difference ΔT across the insulating gasket:

[0032] ;

[0033] , ;

[0034] t refers to the thickness of the gasket;

[0035] λ is the thermal conductivity of the gasket;

[0036] S is the contact area.

[0037] IGBT current Calculations, such as Figure 2 As shown, the circuit includes a bus current sampling resistor R1, a compressor module current sampling resistor R2, and a fan module current sampling resistor R3, corresponding to the current... It can be calculated; the current in capacitor C1 is very small and can be ignored.

[0038] Therefore, we obtain, ;

[0039] in, Bus current; This refers to the compressor current. This represents the fan current.

[0040] It is worth noting that the IGBT temperature obtained in practical applications can be tested and corrected based on the following actual conditions:

[0041] (1) The radiator temperature calculated from the output temperature of the compressor IPM module;

[0042] (2) Temperature difference of insulating gaskets;

[0043] (3) The difference between the calculated heat generation of IGBT and the actual pre-embedded thermocouple.

[0044] This application requires no changes to existing hardware circuitry and incurs no additional cost. It simply calculates the IGBT temperature; when the temperature exceeds a certain limit, it controls the IGBT switch to lower the temperature and protect it. This reduces device failure rate and improves product quality.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for calculating the IGBT temperature in an air conditioner PFC circuit, characterized in that, include: Obtain the case temperature of an insulated gate bipolar transistor (IGBT). and IGBT current ; Calculate IGBT temperature using formula : ； in, This refers to the heat dissipation power of the IGBT; The thermal resistance from the IGBT junction to the case; This refers to the collector-emitter voltage of the IGBT. For the IGBT's switching loss; For IGBT turn-off losses; For the fixed switching frequency of IGBT, , , , , Obtained from the IGBT datasheet.

2. The method for calculating IGBT temperature in an air conditioner PFC circuit according to claim 1, characterized in that, The case temperature of the IGBT The temperature is obtained by measuring the casing temperature of the compressor drive module IPM.

3. The method for calculating IGBT temperature in an air conditioner PFC circuit according to claim 2, characterized in that, When the IGBT type is insulated. =Case temperature of the compressor drive module IPM; when the IGBT type is non-insulated. = Case temperature of compressor drive module IPM + ΔT; ΔT is the temperature difference between the two sides of the IGBT with added insulating gasket.

4. The method for calculating IGBT temperature in an air conditioner PFC circuit according to claim 3, characterized in that, The temperature difference ΔT between the two sides of the insulating pad: ； in, ; This refers to the thickness of the insulating pad; The thermal conductivity of the insulating gasket; This represents the contact area between the IGBT and the insulating gasket.

5. The method for calculating IGBT temperature in an air conditioner PFC circuit according to claim 1, characterized in that, The current of the IGBT : ； in, Bus current; This refers to the compressor current. This represents the fan current.

6. A method for calculating IGBT temperature in an air conditioner PFC circuit according to any one of claims 1-5, characterized in that, It also includes correcting the calculated IGBT temperature based on the compressor drive module IPM shell temperature calculated from the compressor IPM module output temperature, the temperature difference between the two sides of the insulating gasket, the difference between the calculated IGBT temperature value and the actual pre-embedded thermocouple test value.

Images