Detection circuit and parameter determination method for power switching transistors

Abstract

The application discloses a detection circuit and a parameter determination method of a power switch tube, and improves the influence of temperature change on the DESAT detection performance. The power switch tube, a resistance module and n negative temperature coefficient diodes are connected in series between a DESAT pin of constant current output and the ground. The method comprises the following steps: determining the size of each constant in functions f1(b3, n) and f2(b3, n), b3 is a zero offset of the resistance module, the two functions are a first term coefficient and a constant term in the functions with temperature as the independent variable and the deviation between the DESAT pin voltage and the reference voltage as the dependent variable, and the DESAT pin voltage is a calculated value; solving b3 and n when f1 2 (b3, n) + f2 2 (b3, n) takes a minimum value; and when the solving result exceeds the allowed range, the solving result is modified to a value within the allowed range and not more than a preset distance from the current value.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and more specifically, to a detection circuit and parameter determination method for power switching transistors. Background Technology

[0002] The desaturation phenomenon in power switches typically occurs when the power switch is short-circuited. See also... Figure 1 The DESAT detection circuit for power switch Q2 (hereinafter referred to as the detection circuit) includes: the driver chip for power switch Q2, and the resistor module R around the driver chip. S and n (n≥0) diodes D with negative temperature coefficients DST The output of the constant current source inside the driver chip is connected to the DESAT pin of the driver chip; power switch Q2, resistor module R S and n diodes with negative temperature coefficients D DST It is connected in series between the DESAT pin and ground (GND). The driver chip compares the voltage of the DESAT pin to ground with the reference voltage output from the internal reference voltage source of the driver chip. When the voltage of the DESAT pin to ground is greater than the reference voltage, it is determined that the saturation voltage drop of the power switch Q2 exceeds its own allowable safe range. At this time, the power switch Q2 is turned off in time to realize the short circuit protection of the power switch Q2.

[0003] The above constant current source, reference voltage source, and resistor module R S Power switch Q2 and diode D DST Different degrees of temperature drift exist (i.e., the output current I of the constant current source). DESAT Reference voltage, resistor module R S The resistance value, the saturation voltage drop of the power switch Q2, and the diode D DST The voltage drop across the transistors will drift with temperature, resulting in different optimal reference voltage values ​​required at different temperatures. Consequently, the actual reference voltage may be too high or too low under different temperature conditions. When the actual reference voltage is too high, the power switch Q2 cannot be turned off effectively and in a timely manner; when the actual reference voltage is too low, false protection is likely to occur. Therefore, the temperature drift problem of this detection circuit leads to unstable DESAT detection performance. Summary of the Invention

[0004] In view of this, the present invention provides a detection circuit and parameter determination method for power switching transistors to improve the impact of temperature condition changes on DESAT detection performance.

[0005] A method for determining circuit parameters, wherein the circuit refers to a detection circuit for a power switch transistor, the circuit comprising: a driver chip for the power switch transistor, a resistor module surrounding the driver chip, and n negative temperature coefficient diodes; the driver chip has a desaturation DESAT pin that outputs a constant current, and the power switch transistor, the resistor module, and the n negative temperature coefficient diodes are connected in series between the DESAT pin and ground; the driver chip is used to control the power switch transistor to turn off when the voltage of the DESAT pin to ground exceeds a reference voltage, wherein the method includes:

[0006] Determine the magnitudes of the constants in two linear functions f1(b3,n) and f2(b3,n), where b3 is the zero-degree offset of the resistor module, and f1(b3,n) and f2(b3,n) are the coefficients of the first term and the constant term of a quadratic function with temperature as the independent variable and the deviation between the DESAT pin voltage to ground and the reference voltage as the dependent variable, respectively. The DESAT pin voltage to ground is calculated based on the saturation voltage drop of the power switch, the voltage across the resistor module, the output current of the DESAT pin, and the total voltage drop of the n negative temperature coefficient diodes.

[0007] Without considering the constraints imposed on the values ​​of b3 and n by the allowable ranges of b3 and n, find f1. 2 (b3, n) + f2 2 The values ​​of b3 and n when (b3, n) takes a local minimum;

[0008] When the solution result exceeds the allowed range, the solution result will be modified to a value that is no more than a preset distance from the current value and is within the allowed range; the allowed range includes: 0 ≤ n ≤ V DESAT_th / V DST V DESAT_th V is the reference voltage. DST Let n be the voltage drop across a single diode, where n is an integer and b3 ≥ 0.

[0009] In one embodiment, modifying the solution result to a value that is no more than a preset distance from the current value and is within the allowed range includes: modifying the solution result to a value that is closest to the current value and is within the allowed range.

[0010] In one embodiment, modifying the solution result to a value that is closest to the current value and falls within the allowed range includes:

[0011] When the solution result exceeds the allowable range because n and b3 are decimals, determine the smallest integer n1 greater than or equal to n, the largest integer n2 less than or equal to n, and the smallest integer b3 greater than or equal to b3. 31 The largest integer b less than or equal to n32 Based on this, four sets of solutions are derived: (b) 31 ,n1) (b 31 n2), (b 32 (n1) and (b) 32 Substitute these four solutions into f1 respectively. 2 (b3, n) + f2 2 (b3,n), take f1 2 (b3, n) + f2 2 The set of b3 and n values ​​corresponding to the minimum value of (b3, n) is used as the corrected solution result.

[0012] In one embodiment, the calculation of f1 2 (b3, n) + f2 2 The values ​​of b3 and n when (b3, n) takes a local minimum include:

[0013] By analyzing f1 2 (b3, n) + f2 2 Taking the partial derivative of (b3, n), we get f1. 2 (b3, n) + f2 2 The values ​​of b3 and n when (b3, n) takes a minimum value.

[0014] In one embodiment, the calculation of f1 2 (b3, n) + f2 2 The values ​​of b3 and n when (b3, n) takes a minimum value are replaced with: finding the range of values ​​of b3 and n when both f1(b3, n) and f2(b3, n) are less than the preset value;

[0015] Correspondingly, when the solution result exceeds the allowed range, the solution result is modified to a value that is no more than a preset distance from the current value and is within the allowed range, and replaced by: selecting a set of b3 and n values ​​that are within the allowed range from the value range of b3 and n.

[0016] In one embodiment, f1(b3, n) = a1b3 - a2 + a3b1 + a4 + na5.

[0017] f2(b3,n)=b1b3-b2+b4+nb5,

[0018] The meanings of the constants in f1(b3,n) and f2(b3,n) are as follows:

[0019] a1 is the temperature-dependent coefficient of the DESAT pin output current, a2 is the temperature-dependent coefficient of the reference voltage, a3 is the temperature-dependent coefficient of the resistance of the resistor module, b1 is the zero-degree offset of the DESAT pin output current, a4 is the temperature-dependent coefficient of the saturation voltage drop of the power switch, a5 is the temperature-dependent coefficient of the total voltage drop of the n negative temperature coefficient diodes, b2 is the zero-degree offset of the reference voltage, b4 is the zero-degree offset of the saturation voltage drop of the power switch, and b5 is the zero-degree offset of the n negative temperature coefficient diodes.

[0020] In one embodiment, the allowable range further includes: b3 conforming to a standard resistor value table.

[0021] Another method for determining circuit parameters, wherein the circuit refers to a detection circuit for a power switch, the circuit comprising: a driver chip for the power switch, and n negative temperature coefficient diodes surrounding the driver chip; a constant current output from the desaturation DESAT pin of the driver chip, the power switch and the n negative temperature coefficient diodes connected in series between the DESAT pin and ground; the driver chip is used to control the power switch to turn off when the voltage of the DESAT pin to ground exceeds a reference voltage, wherein the method includes:

[0022] Determine the magnitudes of the constants in two linear functions with n as the variable, f4(n) and f5(n); where f4(n) and f5(n) are the coefficient of the first term and the constant term, respectively, of the linear function with temperature as the independent variable and the deviation between the DESAT pin voltage to ground and the reference voltage as the dependent variable; the DESAT pin voltage to ground is calculated based on the saturation voltage drop of the power switch and the total voltage drop of the n negative temperature coefficient diodes;

[0023] Find f4 without considering the constraints on the value of n based on its allowable range. 2 (n)+ f5 2 (n) is the value of n when it takes its minimum value;

[0024] When the solution result exceeds the allowed range, the solution result will be modified to a value that is no more than a preset distance from the current value and is within the allowed range, where the allowed range includes: 0 ≤ n ≤ V. DESAT_th / V DST V DESAT_th V is the reference voltage. DST Let n be the voltage drop across a single diode, where n is an integer.

[0025] A detection circuit for a power switch includes: a driver chip for the power switch, a resistor module surrounding the driver chip, and n negative temperature coefficient diodes; the driver chip has a desaturation DESAT pin that outputs a constant current, and the power switch, the resistor module, and the n negative temperature coefficient diodes are connected in series between the DESAT pin and ground; the driver chip is used to control the power switch to turn off when the voltage of the DESAT pin to ground exceeds a reference voltage, wherein the zero-degree offset b3 and the values ​​of n of the resistor module are calculated using the corresponding circuit parameter determination method described above.

[0026] Another desaturation DESAT detection circuit for a power switch includes: a driver chip for the power switch, and n negative temperature coefficient diodes surrounding the driver chip; the driver chip has a constant current output on its desaturation DESAT pin, and the power switch and the n negative temperature coefficient diodes are connected in series between the DESAT pin and ground; the driver chip is used to control the power switch to turn off when the voltage of the DESAT pin to ground exceeds a reference voltage, wherein the value of n is calculated using the aforementioned circuit parameter determination method.

[0027] As can be seen from the above technical solution, the present invention achieves this by reasonably setting the resistor module R. S The zero-degree offset and the number n of series-connected negative temperature coefficient diodes ensure that the deviation between the DESAT pin voltage to ground and the reference voltage always approaches 0 with temperature changes. At this time, the true value of the reference voltage provided under different temperature conditions always approaches the optimal value, and the impact of temperature changes on DESAT detection performance is minimized, thus improving the impact of temperature changes on DESAT detection performance. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 A schematic diagram of a detection circuit structure for a power switch transistor disclosed in the prior art;

[0030] Figure 2 This is a flowchart of a circuit parameter determination method disclosed in an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of a detection circuit for another type of power switch transistor;

[0032] Figure 4 This is a flowchart of another method for determining circuit parameters disclosed in an embodiment of the present invention. Detailed Implementation

[0033] For the sake of clarity and reference, the technical terms, abbreviations, or acronyms used below are summarized as follows:

[0034] DESAT: Desaturation;

[0035] MOSFET: Metal-Oxide-Semiconductor Field-Effect Transistor;

[0036] IGBT: Insulated Gate Bipolar Transistor.

[0037] 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.

[0038] This invention discloses a method for determining circuit parameters to improve the impact of temperature changes on DESAT detection performance.

[0039] This circuit refers to the detection circuit for the power switching transistor; its schematic diagram can still be found in [reference needed]. Figure 1 The power switch is denoted by Q2, specifically:

[0040] The power switch Q2 can be either an IGBT or a MOSFET; it is not limited to either. Figure 1 This example uses IGBT with power switch Q2 as the only example; other power switches may or may not be connected in parallel with power switch Q2. Figure 1 The example only uses power switch Q2 without any other power switches connected in parallel.

[0041] The detection circuit includes a driver chip for the power switch Q2, and a resistor module R around the driver chip. S and n diodes with negative temperature coefficients D DST ;

[0042] The driver chip has a built-in constant current source, the output of which is connected to the DESAT pin of the driver chip. The output current of the constant current source is expressed as I. DESAT express;

[0043] Power switch Q2, resistor module RS and n diodes with negative temperature coefficients D DST Connected in series between the DESAT pin and ground (GND); Resistor module R S It can be a single resistive element, or it can be a combination of multiple resistive elements in series, parallel, or series-parallel configurations. Figure 1 The middle only uses resistor module R S This is an example of a standalone resistive element;

[0044] The driver chip also incorporates a comparator circuit and a reference voltage source; one input of the comparator circuit is connected to the DESAT pin, and the other input is connected to the output of the reference voltage source; this comparator circuit is used to measure the voltage V between the DESAT pin and ground. DESAT Exceeding the protection threshold, i.e., the reference voltage V output by the reference voltage source. DESAT_th At this time, the control power switch Q2 is turned off (e.g.) Figure 1 The driver chip's shutdown pin OUTL is set to a low level, thereby turning off the power switch Q2.

[0045] Since the power switch Q2 is a device with a positive temperature coefficient, a diode D with a negative temperature coefficient is connected in series with it. DST This can offset some of the temperature drift; by adjusting the series-connected diode D DST The number n can adjust the protection threshold V DESAT_th The size, and due to the single diode D DST The voltage drop across the diode is fixed, so adjusting diode D alone... DST The number of elements n can only be used to coarsely adjust the protection threshold V. DESAT And resistor module R S A high-precision resistor module R that can be finely adjusted via series resistance. S It can achieve fine-tuning of the protection threshold V DESAT_th .

[0046] In one embodiment, see still Figure 1 The detection circuit may further include a turn-off resistor R. GL and turn-on resistor R GH ; Turn-off resistor R GL Connected between the turn-off pin OUTL of the driver chip and the control electrode of the power switch Q2, the turn-off resistor R is adjusted. GL The resistance value can adjust the turn-off speed of Q2; the turn-on resistor R GH Connected between the turn-on pin OUTH of the driver chip and the control electrode of the power switch Q2, the turn-on resistor R is adjusted. GH The resistance value can adjust the turn-on speed of Q2.

[0047] In one embodiment, see still Figure 1The detection circuit may further include a blanking capacitor C1 and a clamping diode D2; the blanking capacitor C1 is used to prevent the power switch Q2 from falsely protecting itself during the turn-on process; the clamping diode D2 is used to prevent negative voltage from appearing on the DESAT pin of the driver chip.

[0048] See Figure 2 Any of the parameter determination methods disclosed above includes:

[0049] Step S01: Determine the magnitudes of the constants in the two linear functions f1(b3,n) and f2(b3,n), which are bivariate linear functions with b3 and n as variables;

[0050] Where b3 is the resistor module R S The zero-degree offset; f1(b3,n) and f2(b3,n) are the zero-degree offsets with temperature as the independent variable and the voltage between the DESAT pin and ground as the reference voltage V, respectively. DESAT_th The deviation is the coefficient of the linear term and the constant term in the quadratic function of the dependent variable; the voltage to ground of the DESAT pin is based on the saturation voltage drop V of the power switch Q2. CE Resistor module R S Voltage across terminals, DESAT pin output current I DESAT And the n diodes D with negative temperature coefficients DST Total pipe pressure drop V D Calculated.

[0051] Step S02: Without considering the constraints imposed by the allowable ranges of b3 and n on the values ​​of b3 and n, calculate f1. 2 (b3,n)+f2 2 The values ​​of b3 and n when (b3, n) takes a minimum value.

[0052] Specifically, parameters in the detection circuit that drift with temperature T include: the output current I of the DESAT pin. DESAT Protection threshold V DESAT_th Resistor module R S The resistance value, the saturation voltage drop V of the power switch Q2 CE and diode D DST The pipe pressure drop.

[0053] Among them, the DESAT pin outputs current I DESAT It can be approximated as:

[0054] I DESAT =a1×T+b1 (Equation 1)

[0055] In equation (1), a1 is the output current I of the DESAT pin. DESAT The influence coefficient of temperature T, b1 is I DESATThe zero-degree offset.

[0056] Protection threshold V DESAT_th It can be approximated as:

[0057] V DESAT_th =a²×T+b² (Equation 2)

[0058] In equation (2), a2 is the protection threshold V DESAT_th The influence coefficient of temperature T, b2 is the protection threshold V DESAT_th The zero-degree offset.

[0059] Resistor module R S The resistance value can be approximated as:

[0060] R S =a3×T+b3Formula (3)

[0061] In equation (3), a3 is the resistor module R S The resistance value is affected by the temperature T coefficient, and b3 is the resistance module R. S The zero-degree offset of the resistance value.

[0062] The saturation voltage drop V of power switch Q2 CE It can be approximated as:

[0063] V CE =a4×T+b4 (Equation 4)

[0064] In equation (4), a4 is the saturation voltage drop V of the power switch Q2. CE The influence coefficient of temperature T, b4 is V CE The zero-degree offset.

[0065] n diodes D DST Total pipe pressure drop V D It can be approximated as:

[0066] V D =n×(a5×T+b5) Equation (5)

[0067] In equation (5), a5 represents n diodes D DST Total pipe pressure drop V D The influence coefficient of temperature T, b5 is V D The zero-degree offset.

[0068] DESAT pin voltage to ground V DESAT The result calculated based on equations (1), (3), (4), and (5) is as follows:

[0069] V DESAT=(a3×T+b3)×(a1×T+b1)+(a4×T+b4)+n×(a5×T+b5) Equation (6)

[0070] Define the function ƒ(T) = V DESAT - Protection threshold V DESAT_th Then, according to equations (6) and (2), we can obtain:

[0071] ƒ(T) = a1a3T 2 +(a1b3-a2+a3b1+a4+na5)×T+b1b3-b2+b4+nb5 Formula (7)

[0072] When the protection threshold V DESAT_th It always approaches V as the temperature changes. DESAT At that time, the protection threshold V provided under different temperature conditions DESAT_th The true value always approaches the optimal value, and the impact of temperature changes on DESAAT detection performance is minimized. Based on this, the design goal of this invention is to ensure that the function ƒ(T) always approaches 0 with changes in temperature.

[0073] To achieve this design goal, the coefficients of the quadratic term a1a3, the linear term a1b3-a2+a3b1+a4+na5, and the constant term b1b3-b2+b4+nb5 of the function ƒ(T) need to be close to 0, which means the following objective needs to be achieved:

[0074] Equation (8)

[0075] a1, a2, a3, a4, a5, b1, b2, b3, b4, and b5 are all determined by the device's own parameters, with b3 and n being adjustable. Furthermore, due to the resistor module R... S The resistance value is affected by temperature, and the coefficient a3 is relatively small, so a1a3 approaches 0. Therefore, equation (8) can be simplified to:

[0076] Equation (9)

[0077] Let b3 and n be variables, and let the functions f1(b3, n) and f2(b3, n) be defined as follows:

[0078] f1(b3,n)= a1b3-a2+a3b1+a4+na5

[0079] f2(b3,n)=b1b3-b2+b4+nb5

[0080] Therefore, in this embodiment of the invention, the functions f1(b3,n) and f2(b3,n) must always be close to 0, that is, f1 2 (b3,n)+f2 2(b3, n) always approaches 0. Let the function be f3(b3, n) = f1. 2 (b3, n) + f2 2 If f(b3, n) is a function f3(b3, n), then the embodiment of the present invention requires that the function f3(b3, n) take the minimum value.

[0081] By taking the partial derivative of the function f3(b3, n), we obtain the following system of two linear equations in two variables:

[0082] Equation (10)

[0083] The values ​​of n and b3 obtained by solving equation (10) are the values ​​of b3 and n corresponding to the minimum value of function f3(b3, n).

[0084] Step S03: When the solution result exceeds the allowed range, modify the solution result to a value that is no more than a preset distance from the current value and is within the allowed range.

[0085] Specifically, b3 and n are parameters in the detection circuit, so n and b3 themselves have the property that "0 ≤ n ≤ V". DESAT_th / V DST V DST For a single diode D DST The tube voltage drop, n is an integer, b3≥0, and b3 conforms to the standard resistance value table (b3 conforming to the standard resistance value table is an optional condition) is the constraint condition, which is also the allowable range. However, the solution result (b3, n) obtained by solving equation (10) may not meet the constraint condition. At this time, it is necessary to correct the solution result (b3, n) to modify the solution result to a value that is no more than a preset distance from the current value and is within the allowable range. Since the closer the distance between (b3, n) before correction and (b3, n) after correction is, the better the effect of suppressing temperature drift, the best correction is to the value that is closest to the current value and meets the constraint condition.

[0086] For example, when the solution does not meet the constraint because n and b3 are decimals, the correction method could be: determine the smallest integer n1 greater than or equal to n, the largest integer n2 less than or equal to n, and the smallest integer b3 greater than or equal to b3. 31 The largest integer b less than or equal to n 32 Based on this, four solutions are derived that are closest to the solution obtained from equation (10) (b3, n): 31 ,n1) (b 31 n2), (b 32 (n1) and (b) 32 Substitute these four solutions into the function f3(b3, n), and take the solution result of (b3, n) that corresponds to the minimum value of the function f3(b3, n) after correction as the optimal solution.

[0087] Alternatively, to ensure that functions f1(b3,n) and f2(b3,n) always approach 0, steps S02-S03 can be replaced by: calculating the range of values ​​for b3 and n when both f1(b3,n) and f2(b3,n) are less than preset values, and then selecting a set of b3 and n values ​​that satisfy the constraint from the range of values ​​for b3 and n. This alternative scheme can suppress the temperature drift problem to some extent, but the randomly selected set of b3 and n may not be the optimal solution, or it may require a slightly longer calculation to select the optimal solution.

[0088] Furthermore, as described above, regarding the protection threshold V... DESAT In applications requiring high adjustment precision, diode D can be introduced simultaneously. DST and resistor module R S (For example Figure 1 As shown), while the protection threshold V DESAT In applications where lower adjustment precision is required, the resistor module R may not be necessary. S (For example Figure 3 (As shown). Referring to the parameter determination method introduced earlier, similarly, it can be obtained that without introducing a resistor module R... S Methods for determining parameters at time, such as Figure 4 As shown, it includes:

[0089] Step S11: Determine the magnitudes of the constants in the two linear functions f4(n) and f5(n), where f4(n) and f5(n) are linear functions with temperature as the independent variable and the voltage between the DESAT pin and ground and the reference voltage V, respectively. DESAT_th The deviation is the coefficient of the linear term and the constant term in the linear function of the dependent variable; the voltage to ground of the DESAT pin is based on the saturation voltage drop V of the power switch Q2. CE And the n diodes D with negative temperature coefficients DST Total pipe pressure drop V D Calculated;

[0090] The linear function is: the voltage of the DESAT pin to ground and the reference voltage V. DESAT_th The difference = (a4 + na5 - a2) × T - b2 + b4 + nb5;

[0091] Step S12: Without considering the constraints on the value of n based on its allowable range, calculate f4. 2 (n)+ f5 2 (n) is the value of n when it takes its minimum value;

[0092] Step S13: When the solution result exceeds the allowed range, modify the solution result to a value that is no more than a preset distance from the current value and is within the allowed range.

[0093] In one embodiment, modifying the solution result to a value that is no more than a preset distance from the current value and is within the allowed range includes: modifying the solution result to a value that is closest to the current value and is within the allowed range.

[0094] Corresponding to the above method embodiments, this invention also discloses a detection circuit for a power switch, comprising: a driver chip for the power switch, a resistor module surrounding the driver chip, and n negative temperature coefficient diodes; the driver chip has a constant current output on its DESAT pin, and the power switch, the resistor module, and the n negative temperature coefficient diodes are connected in series between the DESAT pin and ground; the driver chip is used to control the power switch to turn off when the voltage of the DESAT pin to ground exceeds a reference voltage; wherein, the zero-degree offset b3 and n of the resistor module are calculated using the corresponding circuit parameter determination method described above.

[0095] Another detection circuit for a power switch includes: a driver chip for the power switch, and n negative temperature coefficient diodes surrounding the driver chip; the driver chip has a constant current output on its DESAT pin, and the power switch and the n negative temperature coefficient diodes are connected in series between the DESAT pin and ground; the driver chip is used to control the power switch to turn off when the voltage of the DESAT pin to ground exceeds a reference voltage; wherein the value of n is calculated using the corresponding circuit parameter determination method described above.

[0096] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. Regarding the DESAT detection circuit disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0097] The terminology in the specification, claims, and accompanying drawings of this invention “ First" The terms "second," "comprising," and "including" are used to distinguish between similar but different objects, and are not necessarily used to describe a specific order or sequence. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one" does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0098] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the embodiments of the invention. Therefore, the embodiments of the invention are not to be limited to the embodiments shown herein, but are to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method of determining a parameter of a circuit, the circuit being a detection circuit of a power switch, the circuit comprising: The drive chip of the power switch tube, and a resistance module and n negative temperature coefficient diodes outside the drive chip; The drive chip is used for controlling the power switch tube to be turned off when the voltage of the DESAT pin to ground exceeds the reference voltage, characterized in that the method comprises: Determining the sizes of the constants in the two binary first-order functions f1(b3, n) and f2(b3, n) with b3 and n as variables, wherein f1(b3, n) = a1b3-a2+a3b1+a4+na5, f2(b3, n) = b1b3-b2+b4+nb5, and the meanings of the constants in f1(b3, n) and f2(b3, n) are as follows: a1 is the temperature influence coefficient of the DESAT pin output current, a2 is the temperature influence coefficient of the reference voltage, a3 is the temperature influence coefficient of the resistance value of the resistance module, b1 is the zero-degree offset of the DESAT pin output current, a4 is the temperature influence coefficient of the saturation tube voltage drop of the power switch tube, a5 is the temperature influence coefficient of the total tube voltage drop of the n negative temperature coefficient diodes, b2 is the zero-degree offset of the reference voltage, b4 is the zero-degree offset of the saturation tube voltage drop of the power switch tube, b5 is the zero-degree offset of the n negative temperature coefficient diodes, b3 is the zero-degree offset of the resistance module, f1(b3, n) and f2(b3, n) are respectively a first-order coefficient and a constant term in a univariate quadratic function with temperature as an independent variable and the deviation of the voltage of the DESAT pin to ground from the reference voltage as a dependent variable, and the voltage of the DESAT pin to ground is calculated according to the saturation tube voltage drop of the power switch tube, the voltage across the resistance module, the DESAT pin output current and the total tube voltage drop of the n negative temperature coefficient diodes; f1(b3, n) is found without taking into account the constraints on the values of b3 and n imposed by the allowed range of b3 and n 2 (b3, n) + f2(b3, n) is found 2 the values of b3 and n at which f1(b3, n) takes a minimum value When the solving result exceeds the allowed range, the solving result is modified to a value which is not more than a preset distance from the current value and is within the allowed range; the allowed range includes: 0≤n≤V DESAT_th / V DST , V DESAT_th is the reference voltage, V DST is the voltage drop of a single diode, n is an integer, and b3≥0.

2. The circuit parameter determination method according to claim 1, characterized by, The modification of the solving result to a value closest to the current value and within the allowable range comprises:

3. The circuit parameter determination method according to claim 2, characterized by, The modification of the solving result to a value closest to the current value and within the allowable range comprises: When the solution result exceeds the allowed range due to n and b3 being decimals, the minimum integer n1 greater than or equal to n, the maximum integer n2 less than or equal to n, the minimum integer b 31 greater than or equal to b3, and the maximum integer b 32 less than or equal to b3 are determined, and four groups of solutions are combined according to (b 31 , n1), (b 31 , n2), (b 32 , n1) and (b 32 , n2); the four groups of solutions are substituted into f1 2 (b3, n) + f2 2 (b3, n) respectively, and the group of b3 and n corresponding to the minimum value of f1 2 (b3, n) + f2 2 (b3, n) is taken as the corrected solution result.

4. The circuit parameter determination method according to claim 1, 2 or 3, characterized by, said f1 2 (b3, n) + f2 2 the values of b3 and n at which (b3, n) takes a minimum value, comprising: By taking the partial derivative of f1 2 (b3, n) + f2 2 (b3, n) + f2 2 (b3, n) + f2 2 (b3, n) + f2 5. The circuit parameter determination method according to claim 1, characterized by, The f1 2 (b3, n) + f2 2 (b3, n) is replaced by: the value range of b3 and n when f1(b3, n) and f2(b3, n) are both less than a preset value; Correspondingly, the modification of the solving result to a value closest to the current value and within the allowable range is replaced by: selecting a set of values of b3 and n within the allowable range from the value range of b3 and n.

6. The circuit parameter determination method according to claim 1, characterized by, The allowable range further comprises: b3 conforms to a standard resistance value table.

7. A method of determining parameters of a circuit, the circuit being a detection circuit of a power switch, the circuit comprising: The drive chip of the power switch tube, and n negative temperature coefficient diodes outside the drive chip; The drive chip has a constant current output of a desaturation DESAT pin, the power switch tube and the n negative temperature coefficient diodes are connected in series between the DESAT pin and the ground; the drive chip is used to control the power switch tube to be turned off when the voltage between the DESAT pin and the ground exceeds a reference voltage, characterized in that the method comprises: The values of the constants in the two monomial first order functions f4(n) and f5(n) with n as the variable are determined; wherein f4(n)=a4+na5-a2, f5(n)=-b2+b4+nb5; a2 is the temperature influence coefficient of the reference voltage, a4 is the temperature influence coefficient of the saturation tube voltage drop of the power switch tube, a5 is the temperature influence coefficient of the total tube voltage drop of the n negative temperature coefficient diodes, b2 is the zero offset of the reference voltage, b4 is the zero offset of the saturation tube voltage drop of the power switch tube, and b5 is the zero offset of the n negative temperature coefficient diodes; f4(n) and f5(n) are the first order coefficient and the constant term in the monomial first order function with temperature as the independent variable and the deviation of the voltage between the DESAT pin and the ground from the reference voltage as the dependent variable; the voltage between the DESAT pin and the ground is calculated according to the saturation tube voltage drop of the power switch tube and the total tube voltage drop of the n negative temperature coefficient diodes; f4 is solved without considering the constraint on the value of n in terms of the allowed range of n 2 (n) + f5 2 the value of n at which f4 (n) takes a minimum When the solving result exceeds the allowed range, the solving result is modified to a value which is not more than a preset distance from the current value and is within the allowed range, the allowed range comprising: 0≤n≤V DESAT_th / V DST , V DESAT_th is the reference voltage, V DST is the voltage drop of a single diode, and n is an integer.

8. A detection circuit for a power switch tube, comprising: The drive chip of the power switch tube, and the resistance module and the n negative temperature coefficient diodes outside the drive chip; The drive chip has a constant current output of a desaturation DESAT pin, the power switch tube, the resistance module and the n negative temperature coefficient diodes are connected in series between the DESAT pin and the ground; the drive chip is used to control the power switch tube to be turned off when the voltage between the DESAT pin and the ground exceeds a reference voltage, characterized in that the zero offset b3 of the resistance module and the value of n are calculated by the circuit parameter determination method in any one of claims 1-6.

9. A detection circuit for a power switch tube, comprising: The drive chip of the power switch tube, and the n negative temperature coefficient diodes outside the drive chip; The drive chip has a constant current output of a desaturation DESAT pin, the power switch tube and the n negative temperature coefficient diodes are connected in series between the DESAT pin and the ground; the drive chip is used to control the power switch tube to be turned off when the voltage between the DESAT pin and the ground exceeds a reference voltage, characterized in that the value of n is calculated by the circuit parameter determination method in claim 7.

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