MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) thermal protection method based on current-time integration

Abstract

The invention discloses an MOSFET thermal protection method based on current-time integration, and the method comprises the following steps: 1, obtaining a group of relation tables of current and time through an offline calibration mode; step 2, constructing an I2T counter, and performing interpolation table look-up to obtain a current target current; 3, through a formula power P = I2R, the current I is a phase current effective value, R is a pure resistor, # imgabs0 # J represents heat generated in the action time t of the power P, the formula is equivalent to a counter, and a target sustainable working current is obtained; and 4, comparing the target current with the actual current, when the actual current is greater than the target current, progressively decreasing the torque according to a preset gradient until the torque is 0, and when the actual current is smaller than the target current, progressively increasing the torque according to the preset gradient until the torque is equal to the torque instruction. By applying the method, complex operation can be avoided, and the estimation precision is high.

Description

Technical Field

[0001] The present invention relates to a method for MOSFET thermal protection, and particularly to a method for MOSFET thermal protection based on current-time integration. Background Art

[0002] Generally, the overheat protection of MOSFET mainly uses junction temperature estimation, which is estimated by calculating the MOSFET loss and the tau model. The main disadvantage is that the loss calculation is relatively complex and requires considering many factors. Especially in the case of combining multiple modulation modes, if the loss calculation is inaccurate, it will have a great impact on the accuracy of junction temperature estimation. In addition, the complexity of the algorithm will also increase the load rate of the MCU execution cycle, and it is more difficult to implement on some low-end MCUs. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for MOSFET thermal protection based on current-time integration to overcome the deficiencies of the prior art, and solve the problems of complex loss calculation, easy inaccurate calculation, and affecting the accuracy of junction temperature estimation.

[0004] To achieve the above object, the technical solution adopted by the present invention is: a method for MOSFET thermal protection based on current-time integration, including the following steps. Step 1, obtain a relationship table of current and time through off-line calibration.

[0005] Step 2, construct a counter for I2T, and interpolate and look up the table to obtain the current target current.

[0006] Step 3, through the formula power P = I 2 R

[0007] where the current I is the effective value of the phase current, and R is a pure resistor.

[0008]

[0009] J represents the heat generated within the action time t of the power P. Equivalent the above formula to a counter, the coefficient in front is the square of the current, dynamically adjust the step size of the counter, and use this counter as the look-up table input in Step 2 to obtain the target sustainable working current.

[0010] Step 4, compare the target current with the actual current. When the actual current is greater than the target current, the torque decreases in a preset gradient until the torque is 0. When the actual current is less than the target current, the torque increases in a preset gradient until it equals the torque command.

[0011] Further, the power levels are divided into maximum torque, peak torque, short-time power, and rated power. According to the power levels, the working current that meets the duration is calibrated and recorded in a two-dimensional array.

[0012] Further, when in the locked-rotor condition at peak torque, a smaller output current is required. At this time, an additional working current with a correction factor time is added and recorded in a two-dimensional array.

[0013] The present invention adopts the above structure to achieve the following beneficial effects: A method for MOSFET thermal protection based on current-time integration provided by the present invention has a simple implementation method, avoids complex operations, reduces the load rate of the MCU execution cycle, does not require simulation, and is completely completed by bench calibration data, with a relatively high estimation accuracy, effectively preventing MOSFET damage. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The technical solution of the present invention will be further described below with reference to the drawings:

[0015] Figure 1 is a flowchart of the method for MOSFET thermal protection based on current-time integration according to the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] In order to enable those skilled in the art to better understand the solution of this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of this application.

[0017] The designer of the present invention innovatively proposed a method for MOSFET thermal protection based on current-time integration to meet the requirements of MOSFET thermal protection, which can avoid complex operations and has a high estimation accuracy.

[0018] As Figure 1 shown, a method for MOSFET thermal protection based on current-time integration includes the following steps. Step 1, obtain a relationship table of current and time through off-line calibration;

[0019] Step 2, construct a counter for I2T and interpolate the table to obtain the current target current;

[0020] Step 3, through the formula power P = I 2 R

[0021] where the current I is the effective value of the phase current and R is the pure resistance,

[0022]

[0023] J represents the heat generated within the action time t of the power P. In fact, in the formula, an integration of the power P is performed, and the essence of integration is accumulation. The above formula is equivalent to a counter, with the coefficient in front being the square of the current. Dynamically adjust the step size of the counter, and use this counter as the look-up table input in step two to obtain the target sustainable working current;

[0024] Step four, compare the target current with the actual current. When the actual current is greater than the target current, the torque decreases in a preset gradient until the torque is 0. When the actual current is less than the target current, the torque increases in a preset gradient until it equals the torque command.

[0025] The power levels include the maximum torque, peak torque, short-time power, and rated power. The maximum torque is for a 10-second load reduction, the peak torque is for a 30-second load reduction, the short-time power is for a 2-minute load reduction, and the rated power is for a 60-minute load reduction. According to the power levels, calibrate the working current that meets the duration and record it in a two-dimensional array.

[0026] In the case of a locked-rotor condition under peak torque, a working current with a correction factor time is required to obtain a smaller output current, and it is recorded in a two-dimensional array.

[0027] The present invention adopts the above structure and has the following beneficial effects: A method for MOSFET thermal protection based on current-time integration provided by the present invention has a simple implementation method, avoids complex operations, reduces the load rate of the MCU execution cycle, does not require simulation, and is completely completed by bench calibration data, with relatively high estimation accuracy and effectively preventing MOSFET damage.

[0028] As mentioned above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for MOSFET thermal protection based on current-time integration, characterized in that: The method comprises the following steps: step 1, obtaining a set of current and time relationship tables by offline calibration; Step 2: construct an I2T counter and interpolate the table to obtain the current target current; Step 3: Use the formula power P = I 2 R The current I is the effective value of the phase current, and R is the pure resistance. J represents the heat generated by the power P within the time t. The above formula is equivalent to a counter. The coefficient in front is the square of the current. The step size of the counter is dynamically adjusted. The counter is used as the table input of step 2 to obtain the target sustainable working current. Step 4: compare the target current with the actual current. When the actual current is greater than the target current, the torque decreases according to the preset gradient until the torque is 0. When the actual current is less than the target current, the torque increases according to the preset gradient until it is equal to the torque command.

2. The method for MOSFET thermal protection based on current-time integration as claimed in claim 1, characterized in that: The power levels are divided into maximum torque, peak torque, short-time power and rated power. According to the power level, the working current that meets the duration is calibrated and recorded in a two-dimensional array.

3. The method for MOSFET thermal protection based on current-time integration as claimed in claim 2, characterized in that: When the stall condition occurs at peak torque, a smaller output current is required. In this case, a correction coefficient is added to the working current and recorded in a two-dimensional array.

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