A power semiconductor switching device overcurrent and short circuit protection circuit

Abstract

The application discloses a kind of power semiconductor switching device overcurrent and short circuit protection circuit, comprising: including the drive circuit of power semiconductor switching device, the drive circuit current output when working;With the overcurrent and short circuit protection isolation detection circuit of drive circuit connection, isolation detection circuit is used to detect the current output by drive circuit;First charging circuit and second charging circuit, first charging circuit is connected with drive circuit and overcurrent and short circuit protection isolation detection circuit respectively, and second charging circuit is connected with first charging circuit;Comparison flip circuit, comparison flip circuit is connected with second charging circuit;Digital isolation circuit, digital isolation circuit is connected with comparison flip circuit, and digital isolation circuit is used to output fault signal from comparison flip circuit to the external MCU for controlling drive circuit shutdown.This application has the characteristics that protection function is stable and reliable and not prone to false triggering.

Description

Technical Field

[0001] This invention relates to the field of power switching device protection technology, specifically to an overcurrent and short-circuit protection circuit for power semiconductor switching devices. Background Technology

[0002] In power semiconductor switching device drive circuit systems, power semiconductor switching devices have relatively weak overcurrent and short-circuit withstand capabilities. Existing overcurrent and short-circuit protection technologies mainly include the following two types:

[0003] The first method involves adding a current source circuit to the drive circuit. By controlling the charging and discharging of the capacitor, the current source circuit is compared with a set reference voltage. The comparison output is fed back to the MCU to turn off the drive signal and achieve the protection function. The main disadvantages of this method are slow response speed, easy to trigger falsely, and complex circuit.

[0004] The second method is to use a dedicated driver chip, which integrates overcurrent and short-circuit protection circuits. However, this method has disadvantages such as high cost and difficulty in procuring dedicated chips. Summary of the Invention

[0005] This invention provides an overcurrent and short-circuit protection circuit for power semiconductor switching devices. This invention features stable and reliable protection functions and is not easily triggered by false triggering.

[0006] The technical solutions to the above technical problems are as follows:

[0007] An overcurrent and short-circuit protection circuit for a power semiconductor switching device includes:

[0008] A drive circuit that includes power semiconductor switching devices, which outputs current when it is in operation;

[0009] The overcurrent and short-circuit protection isolation detection circuit is connected to the drive circuit. The isolation detection circuit is used to detect the current output by the drive circuit. When the drive circuit experiences overcurrent or short circuit, the isolation detection circuit is used to block the detection current from flowing to the switching devices in the drive circuit.

[0010] A first charging circuit and a second charging circuit, wherein the first charging circuit is connected to the drive circuit and the overcurrent and short circuit protection isolation detection circuit respectively, and the second charging circuit is connected to the first charging circuit.

[0011] The comparison switching circuit is connected to the second charging circuit. When the drive circuit experiences overcurrent or short circuit, and the first charging circuit and the second charging circuit charge beyond the set reference voltage, the comparison switching circuit outputs a fault signal.

[0012] The digital isolation circuit is connected to the comparator toggle circuit. The digital isolation circuit is used to output the fault signal from the comparator toggle circuit to the external MCU used to control the shutdown of the drive circuit.

[0013] Furthermore, the driving circuit includes: an isolation driving chip, a driving resistor, a switching device, and an eleventh pull-up resistor. One end of the driving resistor is connected to the driving output pin of the isolation driving chip, and the other end of the driving resistor is connected to the gate of the switching device. The eleventh pull-up resistor is connected to the enable pin of the isolation driving chip, and the pulse width modulation pin of the isolation driving chip is used to connect to an external MCU.

[0014] Furthermore, the overcurrent and short-circuit protection isolation detection circuit includes a first diode, the anode of which is connected to the first charging circuit, and the cathode of which is connected to the drain of the switching device.

[0015] Furthermore, the first charging circuit includes a fifth resistor, a seventh resistor, an eighth resistor, and a sixth capacitor. One end of the fifth resistor and the eighth resistor are respectively connected to the overcurrent and short-circuit protection isolation detection circuit. The other end of the eighth resistor is connected to the other end of the driving resistor. The other end of the fifth resistor is connected to one end of the seventh resistor and the sixth capacitor. The other ends of the seventh resistor and the sixth capacitor are connected to system ground.

[0016] The second charging circuit includes a sixth resistor and a fifth capacitor. One end of the sixth resistor is connected to the other end of the fifth resistor. The other end of the sixth resistor is connected to one end of the fifth capacitor and the input terminal of the comparison switching circuit. The other end of the fifth capacitor is connected to system ground.

[0017] Furthermore, it also includes a second diode and a tenth resistor. The anode of the second diode is connected to the other end of the fifth resistor and one end of the sixth resistor. The cathode of the second diode is connected to one end of the tenth resistor, and the other end of the tenth resistor is connected to one end of the driving resistor.

[0018] The fifth capacitor, together with the sixth resistor, the second diode, and the tenth resistor, constitute the first discharge circuit.

[0019] The sixth capacitor, together with the second diode, the tenth resistor, the driving resistor, the eighth resistor, the fifth resistor, and the seventh resistor, constitute the second discharge circuit.

[0020] Furthermore, the comparison switching circuit includes a comparator, a third input resistor, a ninth feedback resistor, and a second output pull-up resistor. One end of the third input resistor is connected to the second pin of the comparator, and the other end of the third input resistor is used to connect to an external input reference voltage source. One end of the ninth feedback resistor is connected to the first pin of the comparator, and the other end of the ninth feedback resistor is connected to the third pin of the comparator. The third pin of the comparator is also connected to the second charging circuit. One end of the second output pull-up resistor is connected to the eighth pin of the comparator, and the other end of the second output pull-up resistor is connected to the first pin of the comparator.

[0021] Furthermore, the digital isolation circuit includes a digital isolation chip, a fourth input current-limiting resistor, and a first output pull-up resistor. One end of the fourth input current-limiting resistor is connected to the comparator switching circuit, and the other end of the fourth input current-limiting resistor is connected to the input pin of the digital isolation chip. One end of the first output pull-up resistor is connected to the output power supply pin of the digital isolation chip, and the other end of the first output pull-up resistor is connected to the output pin of the digital isolation chip. The output pin of the digital isolation chip is used to output a fault signal to an external MCU.

[0022] As can be seen from the above description of the invention, the isolated driver chip output of this invention not only serves as the gate drive input of the switching device, but also as the voltage source for the charging circuit composed of resistors and capacitors. The charging circuit output is compared with the reference voltage source and then fed back to the MCU through isolation to determine whether to turn off the drive signal, thus protecting the power semiconductor switching device. It cleverly achieves the function of protection only when the drive signal is on, and not when it is off. Although an RC circuit is added to the gate of the switching device, the charging resistance in this circuit is much larger than the driving resistance, and its impact on the turn-on time of the switching device is negligible. Moreover, the added RC circuit also has a certain suppression effect on the oscillation of the drive signal. A discharge circuit with a second diode and a resistor is connected in parallel in the charging circuit loop. The unidirectional conductivity of the second diode cleverly achieves the function of rapid release of charge on the charging capacitor after the drive signal is turned off, achieving the purpose of stable and reliable protection function that is not easily triggered falsely. This circuit can be matched with different RC circuits according to different reference voltage sources and different short-circuit withstand times of power semiconductor switching devices, making it flexible in use and widely applicable. Attached Figure Description

[0023] Figure 1 This is the circuit schematic diagram of the present invention. Detailed Implementation

[0024] The embodiments of the present invention are described in detail below, and examples of these embodiments are provided in the appendix. Figure 1As shown, the same or similar reference numerals throughout denote the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the invention, and should not be construed as limiting the invention.

[0025] like Figure 1 As shown, an overcurrent and short-circuit protection circuit for a power semiconductor switching device according to the present invention includes a drive circuit, an overcurrent and short-circuit protection isolation detection circuit, a first charging circuit, a second charging circuit, a comparison and switching circuit, and a digital isolation circuit. The structure of each part is described in detail below:

[0026] The drive circuit includes power semiconductor switching devices and outputs current when the drive circuit is working. The drive circuit includes an isolation drive chip U3, a drive resistor R12, a switching device Q1, a seventh filter capacitor C7, an eighth filter capacitor C8, and an eleventh pull-up resistor R11. One end of the drive resistor R12 is connected to the drive output pin OUT of the isolation drive chip U3, and the other end of the drive resistor R12 is connected to the gate G of the switching device Q1. One end of the seventh filter capacitor C7 is connected to the input power supply pin VDDI of the isolation drive chip U3. The input power supply pin VDDI of the isolation drive chip U3 is also connected to a +5V power supply. The other end of the seventh filter capacitor C7 is grounded to GND1. The isolation drive chip U3... The input-side ground pin GND1 is connected to ground GND1. The eleventh pull-up resistor R11 is connected to the enable pin DIS of the isolation driver chip U3. The pulse width modulation pin PWM of the isolation driver chip U3 is used to connect to an external MCU. One end of the eighth filter capacitor C8 is connected to the output-side power supply pin VCC of the isolation driver chip U3, and the other end of the eighth filter capacitor C8 is connected to the drive system ground GND2. The drain D of the switching device Q1 is connected to the positive terminal HV+ of the high-voltage bus, and the source S of the switching device Q1 is connected to the negative terminal HV- of the high-voltage bus. The negative terminal HV- of the high-voltage bus is connected to the system ground GND2. The output-side ground pin GND2 of the isolation driver chip U3 is connected to the system ground GND2.

[0027] The overcurrent and short-circuit protection isolation detection circuit is connected to the drive circuit. The isolation detection circuit detects the current output by the drive circuit, and when an overcurrent or short circuit occurs in the drive circuit, it blocks the flow of the detected current to the switching device Q1 in the drive circuit. The overcurrent and short-circuit protection isolation detection circuit includes a first diode D1. The anode of the first diode D1 is connected to the first charging circuit, and the cathode of the first diode D1 is connected to the drain D of the switching device Q1.

[0028] The first charging circuit and the second charging circuit are connected to the drive circuit and the overcurrent and short circuit protection isolation detection circuit, respectively. The second charging circuit is connected to the first charging circuit.

[0029] The first charging circuit includes a fifth resistor R5, a seventh resistor R7, an eighth resistor R8, and a sixth capacitor C6. One end of the fifth resistor R5 and the eighth resistor R8 are respectively connected to the overcurrent and short circuit protection isolation detection circuit. The other end of the eighth resistor R8 is connected to the other end of the drive resistor R12. The other end of the fifth resistor R5 is connected to one end of the seventh resistor R7 and the sixth capacitor C6. The other ends of the seventh resistor R7 and the sixth capacitor C6 are connected to the system ground GND2.

[0030] The second charging circuit includes a sixth resistor R6 and a fifth capacitor C5. One end of the sixth resistor R6 is connected to the other end of the fifth resistor R5. The other end of the sixth resistor R6 is connected to one end of the fifth capacitor C5 and the input terminal of the comparator switching circuit. The other end of the fifth capacitor C5 is connected to system ground GND2.

[0031] It also includes a second diode D2 and a tenth resistor R10. The anode of the second diode D2 is connected to the other end of the fifth resistor C5 and one end of the sixth resistor R6. The cathode of the second diode D2 is connected to one end of the tenth resistor R10, and the other end of the tenth resistor R10 is connected to one end of the driving resistor R12. The fifth capacitor C5, the sixth resistor R6, the second diode D2, and the tenth resistor R10 constitute the first discharge circuit. The sixth capacitor C6, the second diode D2, the tenth resistor R10, the driving resistor R12, the eighth resistor R8, the fifth resistor R5, and the seventh resistor R7 constitute the second discharge circuit.

[0032] The comparison switching circuit is connected to the second charging circuit. When the drive circuit experiences overcurrent or short circuit, and the first charging circuit and the second charging circuit charge beyond the set reference voltage, the comparison switching circuit outputs a fault signal.

[0033] The comparator switching circuit includes comparator U2A, third input resistor R3, ninth feedback resistor R9, second output pull-up resistor R2, third filter capacitor C3, and fourth filter capacitor C4. One end of the third input resistor R3 is connected to pin 2 of comparator U2A, and the other end is used to connect to an external input reference voltage source. One end of the ninth feedback resistor R9 is connected to pin 1 of comparator U2A, and the other end is connected to pin 3 of comparator U2A. Pin 3 of comparator U2A is also connected to the second charging circuit. The second output... One end of the pull-up resistor R2 is connected to pin 8 of comparator U2A, and the other end of the second output pull-up resistor R2 is connected to pin 1 of comparator U2A. One end of the third filter capacitor C3 is connected to pin 8 of comparator U2A. Pin 8 of U2A is also connected to power supply VCC. The other end of the third filter capacitor C3 is connected to system ground GND2. One end of the fourth filter capacitor C4 is connected to pin 2 of comparator U2A. The other end of the fourth filter capacitor C4 is connected to system ground GND2. Pin 4 of comparator U2A is connected to system ground GND2.

[0034] The digital isolation circuit is connected to the comparator toggle circuit. The digital isolation circuit is used to output the fault signal from the comparator toggle circuit to the external MCU used to control the shutdown of the drive circuit.

[0035] The digital isolation circuit includes a digital isolation chip U1, a fourth input current-limiting resistor R4, a first output pull-up resistor R1, a first filter capacitor C1, and a second filter capacitor C2. One end of the fourth input current-limiting resistor R4 is connected to the comparator circuit, and the other end is connected to the input pin IN2 of the digital isolation chip U1. One end of the second filter capacitor C2 is connected to the power input pin VDD2 of the digital isolation chip U1, which is connected to the power supply VCC. The input-side ground pin GND2 of the digital isolation chip U1 is connected to system ground GND2, and the other end of the second filter capacitor C2 is also connected to system ground GND2. The output power supply pin VDD1 of the digital isolation chip U1 is connected to one end of the first filter capacitor C1. The output power supply pin VDD1 of the digital isolation chip U1 is also connected to the +5V power supply. The output side ground pin GND1 of the digital isolation chip U1 is grounded. The other end of the first filter capacitor C1 is grounded. One end of the first output pull-up resistor R1 is connected to the output power supply pin VDD1 of the digital isolation chip U1. The other end of the first output pull-up resistor R1 is connected to the output pin OUT1 of the digital isolation chip U1. The output pin OUT1 of the digital isolation chip U1 is used to output a fault signal to the external MCU. The MCU determines whether the power semiconductor switching device Q1 has experienced an overcurrent or short circuit.

[0036] In this invention, when the PWM drive signal of the drive circuit is on, the output current of the isolation drive chip U3, in addition to driving the gate of the switching device Q1, also has a small portion of current flowing to the overcurrent and short-circuit protection isolation detection circuit through the eighth resistor R8 to form the isolation detection circuit. When the switching device Q1 is in normal working condition, the switching device Q1 is in saturated conduction state, and the detection current flows through the first diode D1 and the switching device Q1 back to ground. The first diode D1 plays the role of decoupling high voltage. When the switching device Q1 experiences overcurrent or short circuit, the switching device Q1 will exit the saturation state, causing the Uds voltage to rise rapidly. The overcurrent and short-circuit protection isolation detection circuit will block the detection current from flowing through, so the current flows to the first charging circuit and the second charging circuit to the comparator switching circuit. When the voltage is charged to exceed the set reference voltage, the comparator switching circuit flips and outputs a low fault signal. This signal is transmitted to the MCU through the digital isolation circuit, and then controls the drive circuit to quickly turn off to achieve the purpose of protecting the power semiconductor switching device and its circuit.

[0037] Based on the above-mentioned overcurrent and short-circuit protection circuit for power semiconductor switching devices, the circuit parameter design steps are as follows:

[0038] Step 1: Connect the third input resistor R3 to the reference voltage source V ref Connect and set the voltage value of the reference voltage source to V. ref Connect the pulse width modulation pin (PWM) of the isolation driver chip U3 to the MCU that outputs the PWM drive signal. Set the period of the PWM drive signal to T, the on-time to Ton, and the off-time to Toff. Connect the output pin (OUT) of the digital isolation chip U1 to the MCU as a fault feedback signal.

[0039] Step 2: Set the resistance value of the driving resistor R12 in the driving circuit to R 12 The voltage value of the power supply VCC on the output side of the isolation driver chip U3 is V. CC The voltage drop of the internal transistor of the driver chip is V. q If the resistance of the eighth resistor R8 in the first charging circuit is R8, the resistance of the fifth resistor R5 is R5, the resistance of the seventh resistor R7 is R7, and the capacitance of the sixth capacitor C6 is C6, then the following calculation formula applies:

[0040] The isolated driver chip U3 outputs a drive voltage value U during the Ton period. c =V CC -V q .

[0041] First charging time constant tr1=((R 12 +R8+R5) / / R7)×C6.

[0042] ((R 12+R8+R5) / / R7 represents the calculation: R 12 The resistance value of the sum of R8 and R5, and then connected in parallel with R7.

[0043] The output voltage of the first charging circuit at time t

[0044] Step 3: Set the resistance of the sixth resistor R6 in the second charging circuit to R6 and the capacitance of the fifth capacitor C5 to C5. Set the output voltage of the second charging circuit to V at time t. ref Then the following calculation formula exists:

[0045] The second charging time constant tr2 = R6 × C5.

[0046] At time t

[0047] Step 4: Set the short-circuit withstand time of switching device Q1 to Ts. To allow sufficient margin, set the time coefficient for the isolation drive circuit protection turn-off to K (K can be 0.1 to 0.5 depending on the actual situation), set the turn-off delay time of the drive chip to Tq, and the signal transmission delay time of the digital isolation chip to Tg. Then, the following calculation formula is given:

[0048] t≤K×Ts-Tq-Tg.

[0049] Based on the above formulas, the parameter values ​​of each charging resistor and each charging capacitor in the appropriate charging circuit can be determined.

[0050] Step 5: Set the resistance value of the tenth resistor R10 to R 10 The capacitance of the fifth capacitor C5 is C5. Therefore, the second discharge time constant can be calculated using the following formula:

[0051] The first discharge time constant tf1 = (R6 + R) 10 )×C5.

[0052] Step 6: Set the resistance value of the twelfth resistor R12 in the second discharge circuit to R 12 The resistance of the eighth resistor R8 is R8, the resistance of the fifth resistor R5 is R5, the resistance of the seventh resistor R7 is R7, and the resistance of the tenth resistor R10 is R. 10 The capacitance of the sixth capacitor C6 is C6. Therefore, the second discharge time constant can be calculated using the following formula:

[0053] The second discharge time constant tf2=(R 10 / / R7 / / (R5+R8+R 12 ))×C6;

[0054] (R 10 / / R7 / / (R5+R8+R 12 () indicates calculation: R7 and R 10 After the parallel resistors are connected, then they are connected to R5, R8, and R... 12 The sum of the resistance values ​​of the parallel circuit.

[0055] According to the above calculation formula, in order to make the discharge time short enough, within the power derating range of the tenth resistor R10, the value of the tenth resistor R10 only needs to be small enough. For example, the resistance value of the tenth resistor R10 is preferably 20Ω.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications made to the present invention by those skilled in the art without departing from the spirit of the present invention shall fall under the protection of the present invention.

Claims

1. An overcurrent and short-circuit protection circuit for a power semiconductor switching device, characterized in that, include: A drive circuit that includes power semiconductor switching devices, which outputs current when it is in operation; The overcurrent and short-circuit protection isolation detection circuit is connected to the drive circuit. The isolation detection circuit is used to detect the current output by the drive circuit. When the drive circuit experiences overcurrent or short circuit, the isolation detection circuit is used to block the detection current from flowing to the switching devices in the drive circuit. A first charging circuit and a second charging circuit, wherein the first charging circuit is connected to the drive circuit and the overcurrent and short circuit protection isolation detection circuit respectively, and the second charging circuit is connected to the first charging circuit. The first charging circuit includes a fifth resistor (R5), a seventh resistor (R7), an eighth resistor (R8), and a sixth capacitor (C6). One end of the fifth resistor (R5) and the eighth resistor (R8) are respectively connected to the overcurrent and short-circuit protection isolation detection circuit. The other end of the eighth resistor (R8) is connected to the other end of the drive resistor (R12). The other end of the fifth resistor (R5) is connected to one end of the seventh resistor (R7) and the sixth capacitor (C6). The other ends of the seventh resistor (R7) and the sixth capacitor (C6) are connected to system ground (GND2). The second charging circuit includes a sixth resistor (R6) and a fifth capacitor (C5). One end of the sixth resistor (R6) is connected to the other end of the fifth resistor (R5). The other end of the sixth resistor (R6) is connected to one end of the fifth capacitor (C5) and the input terminal of the comparator switching circuit. The other end of the fifth capacitor (C5) is connected to system ground (GND2). The comparison switching circuit is connected to the second charging circuit. When the drive circuit experiences overcurrent or short circuit, and the first charging circuit and the second charging circuit charge beyond the set reference voltage, the comparison switching circuit outputs a fault signal. The digital isolation circuit is connected to the comparator toggle circuit. The digital isolation circuit is used to output the fault signal from the comparator toggle circuit to the external MCU used to control the shutdown of the drive circuit.

2. The overcurrent and short-circuit protection circuit for a power semiconductor switching device according to claim 1, characterized in that, The driving circuit includes: an isolation driving chip (U3), a driving resistor (R12), a switching device (Q1), and an eleventh pull-up resistor (R11). One end of the driving resistor (R12) is connected to the driving output pin (OUT) of the isolation driving chip (U3), and the other end of the driving resistor (R12) is connected to the gate (G) of the switching device (Q1). The eleventh pull-up resistor (R11) is connected to the enable pin (DIS) of the isolation driving chip (U3). The pulse width modulation pin (PWM) of the isolation driving chip (U3) is used to connect to an external MCU.

3. The overcurrent and short-circuit protection circuit for a power semiconductor switching device according to claim 2, characterized in that, The overcurrent and short-circuit protection isolation detection circuit includes a first diode (D1), the anode of the first diode (D1) is connected to the first charging circuit, and the cathode of the first diode (D1) is connected to the drain (D) of the switching device (Q1).

4. The overcurrent and short-circuit protection circuit for a power semiconductor switching device according to claim 1, characterized in that, It also includes a second diode (D2) and a tenth resistor (R10). The anode of the second diode (D2) is connected to the other end of the fifth resistor (R5) and one end of the sixth resistor (R6). The cathode of the second diode (D2) is connected to one end of the tenth resistor (R10). The other end of the tenth resistor (R10) is connected to one end of the driving resistor (R12). The fifth capacitor (C5), the sixth resistor (R6), the second diode (D2), and the tenth resistor (R10) constitute the first discharge circuit; The sixth capacitor (C6), together with the second diode (D2), the tenth resistor (R10), the driving resistor (R12), the eighth resistor (R8), the fifth resistor (R5), and the seventh resistor (R7), constitute the second discharge circuit.

5. The overcurrent and short-circuit protection circuit for a power semiconductor switching device according to claim 1, characterized in that, The comparison switching circuit includes a comparator (U2A), a third input resistor (R3), a ninth feedback resistor (R9), and a second output pull-up resistor (R2). One end of the third input resistor (R3) is connected to the second pin (2) of the comparator (U2A), and the other end of the third input resistor (R3) is used to connect to an external input reference voltage source. One end of the ninth feedback resistor (R9) is connected to the first pin (1) of the comparator (U2A), and the other end of the ninth feedback resistor (R9) is connected to the third pin (3) of the comparator (U2A). The third pin (3) of the comparator (U2A) is also connected to the second charging circuit. One end of the second output pull-up resistor (R2) is connected to the eighth pin (8) of the comparator (U2A), and the other end of the second output pull-up resistor (R2) is connected to the first pin (1) of the comparator (U2A).

6. The overcurrent and short-circuit protection circuit for a power semiconductor switching device according to claim 1, characterized in that, The digital isolation circuit includes a digital isolation chip (U1), a fourth input current-limiting resistor (R4), and a first output pull-up resistor (R1). One end of the fourth input current-limiting resistor (R4) is connected to the comparator switching circuit, and the other end of the fourth input current-limiting resistor (R4) is connected to the input pin (IN2) of the digital isolation chip (U1). One end of the first output pull-up resistor (R1) is connected to the output power supply pin (VDD1) of the digital isolation chip (U1), and the other end of the first output pull-up resistor (R1) is connected to the output pin (OUT1) of the digital isolation chip (U1). The output pin (OUT1) of the digital isolation chip (U1) is used to output a fault signal to an external MCU.

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