Desaturation short circuit protection circuit, power device short circuit protection circuit and test circuit

Abstract

The present invention provides a desaturated short-circuit protection circuit, a power device short-circuit protection circuit and a test circuit for protecting power devices, comprising a comparator, a time unit, a short-circuit detection unit and a processing unit; the comparator outputs a comparison result of a detection voltage and a reference voltage, the input end of the time unit is connected to the output end of the comparator, and the time when the detection voltage is less than the reference voltage in the switching cycle of the comparator is converted into a digital signal for setting a blanking time; when the blanking time of the previous switching cycle is reached, the short-circuit detection unit performs short-circuit detection on the power device based on the comparison result to obtain a detection result; the input end of the processing unit is connected to the output end of the short-circuit detection unit; the processing unit performs short-circuit protection on the power device based on the detection result. The short-circuit protection of the present invention has rapidity and reliability.

Description

Technical Field

[0001] The present invention relates to an integrated circuit technology, and in particular to a desaturation short-circuit protection circuit, a power device short-circuit protection circuit and a test circuit. Background Art

[0002] In the field of high-voltage and high-power power electronics, the switching speed, switching loss and other parameters of silicon-based IGBT (insulated gate bipolar transistor) devices have reached bottlenecks due to the material properties of silicon and cannot be further improved. As the third-generation wide-bandgap power semiconductor device that is currently developing rapidly, SiC MOSFET (silicon carbide metal oxide semiconductor field effect transistor) has the advantages of high breakdown voltage, fast switching speed, and high power density. It is a strong competitor of IGBT in the field of high-voltage power conversion and has a trend of gradually replacing IGBT in many applications such as electric vehicle inverters. However, in the application process of SiC MOSFET, there are still some issues that cannot be ignored, one of which is the short-circuit protection of SiC MOSFET devices.

[0003] Compared with IGBT, SiC MOSFET devices have a high power density, and their short-circuit current does not have a clear saturation value, but will continue to increase as the voltage of the device increases. These factors make the short-circuit tolerance of SiC MOSFET worse than that of IGBT. At the same time, the faster switching speed of SiC MOSFET requires a faster short-circuit protection circuit, but the current short-circuit protection circuits of SiCMOSFET are all developed from IGBT short-circuit protection circuits, and the detection speed of these protection circuits is slow for SiC MOSFET. Therefore, in order to quickly and effectively protect SiC MOSFET from short circuits, it is necessary to explore faster and more reliable short-circuit protection methods based on existing protection circuits.

[0004] The desaturation (DESAT) short-circuit protection circuit is widely used in the field of short-circuit protection of high-power switching devices. It has a relatively simple structure and high reliability, and is widely used in the short-circuit protection of IGBTs.

[0005] Figure 1 This is a traditional desaturation protection circuit diagram. It detects the collector-emitter voltage of the IGBT (MOSFET) each time it is turned on. V CE (Drain-Source Voltage V DS ) drops to the on-state voltage to determine whether the device is turned on normally, otherwise a short circuit may occur. V CE ( V DS) takes a while to drop to the on-state voltage drop, so a detection delay needs to be set. This delay to prevent the detection circuit from triggering by mistake is called blanking time. The traditional desaturation protection circuit sets the blanking time by charging the blanking capacitor. ,in is the blanking capacitor value, To protect the threshold reference voltage, The current value for charging the blanking capacitor. Since the charging current, threshold voltage and capacitance value are generally fixed, the blanking time is also fixed. Usually a slightly longer blanking time is set to avoid false triggering of the detection circuit.

[0006] The current short-circuit protection of SiC MOSFET power modules also widely uses desaturation protection circuits, but due to the fast switching speed of SiC MOSFET and the long fixed blanking time of the desaturation protection circuit, the detection circuit cannot quickly detect the short-circuit condition. As a result, the desaturation protection circuit cannot quickly and effectively protect the SiC MOSFET from short circuits. The contradiction between the faster switching speed of SiC MOSFET and the long fixed blanking time of the desaturation circuit needs to be resolved. Summary of the invention

[0007] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a desaturated short-circuit protection circuit, a power device short-circuit protection circuit and a test circuit, so as to solve the problem that the prior art cannot quickly detect and perform effective short-circuit protection.

[0008] To achieve the above-mentioned object and other related objects, the present invention provides a desaturation short-circuit protection circuit for protecting a power device, comprising a comparator, a time unit, a short-circuit detection unit and a processing unit;

[0009] The first input terminal of the comparator is connected to a detection voltage, which is the output voltage of the power device; the second input terminal of the comparator is connected to a reference voltage, which is the on-voltage of the power device; the comparator outputs a comparison result between the detection voltage and the reference voltage;

[0010] The input end of the time unit is connected to the output end of the comparator; the time unit converts the time when the detection voltage is less than the reference voltage in the switching cycle of the comparator into a digital signal, and the digital signal is used to set the blanking time;

[0011] The short-circuit detection unit is connected to the time unit and the output end of the comparator; when the blanking time of the previous switching cycle is reached, the short-circuit detection unit performs short-circuit detection on the power device based on the comparison result to obtain a detection result;

[0012] The input end of the processing unit is connected to the output end of the short-circuit detection unit; the processing unit performs short-circuit protection on the power device based on the detection result.

[0013] Preferably, the time unit includes a clock generation module and a storage setting module;

[0014] The input end of the clock generating module is connected to the driving signal, and is used to generate a continuous pulse signal of a certain period according to the driving signal;

[0015] The storage setting module is connected to the output ends of the comparator and the clock generating module; it is used to convert the time when the detection voltage is less than the reference voltage in the switching cycle of the comparator into a digital signal under the action of the continuous pulse signal, and set the blanking time based on the digital signal.

[0016] Preferably, the storage setting module includes an inverter, a first register and a second register;

[0017] The input end of the first register is connected to the output end of the comparator and the clock generation module, and is used for converting the time when the detection voltage is less than the reference voltage in the switching cycle of the comparator into a digital signal under the action of the continuous pulse signal;

[0018] The input end of the second register is connected to the output end of the first register, the enable end of the second register is connected to the output end of the inverter, and the input end of the inverter is connected to the input end of the clock generation module; the digital signal is copied to the second register at the rising edge of the switching cycle.

[0019] Preferably, the short circuit detection unit comprises a controller and a first logic AND gate;

[0020] The controller receives the driving signal and is connected to the output end of the time unit; it is used to output an enable signal after reaching the blanking time of the previous switching cycle;

[0021] The first input end of the first logic AND gate is connected to the output end of the controller, and the second input end of the first logic AND gate is connected to the output end of the comparator; when the enable signal is valid, the output signal of the comparator is output.

[0022] Preferably, the short circuit detection unit further includes a delay device, a trigger module and a second logic AND gate;

[0023] The input end of the delay device is connected to the output end of the first logic AND gate; and is used to set the delay time;

[0024] The clock end of the trigger module is connected to the output end of the delay device, and the signal input end of the trigger module is connected to the output end of the comparator; after the delay time is reached, the trigger module outputs the current output signal of the comparator;

[0025] The input ends of the second logic AND gate are respectively connected to the output ends of the first logic AND gate and the trigger module; an AND operation is performed on the output signals of the first logic AND gate and the trigger module to obtain the detection result.

[0026] Preferably, the trigger module includes three triggers, namely a first trigger, a second trigger and a third trigger;

[0027] The first trigger is connected to the output end of the delay device and the comparator, and is triggered after reaching the first set delay time, and the first trigger outputs the current output signal of the comparator;

[0028] The second trigger is connected to the output end of the delay device and the comparator, and is triggered after reaching the second set delay time, and the second trigger outputs the current output signal of the comparator;

[0029] The third trigger is connected to the output ends of the delay device and the comparator, and is triggered after a third set delay time is reached. The third trigger outputs a current output signal of the comparator.

[0030] Preferably, the processing unit comprises a logic processing module, a level shifting module and an output driving module;

[0031] The input end of the logic processing module receives the driving signal and is connected to the output end of the short circuit detection unit; it is used to process the detection result to obtain a logic level signal;

[0032] The level shift module is connected to the output end of the logic processing module and is used to process the logic level signal to obtain a driving level signal;

[0033] The input end of the output driving module is connected to the output end of the level shifting module, and the output end of the output driving module is used to connect the control end of the power device; it is used to convert the driving level signal to obtain a driving voltage signal, and the driving voltage signal can perform short-circuit protection on the power device.

[0034] In order to achieve the above-mentioned object and other related objects, the present invention also provides a power device short-circuit protection circuit, including a short-circuit protection circuit and a power device;

[0035] The input end of the short-circuit protection circuit is connected to the output end of the power device; the output end of the short-circuit protection circuit is connected to the control end of the power device;

[0036] The short-circuit protection circuit is the above-mentioned desaturation short-circuit protection circuit.

[0037] Preferably, the power device is a silicon carbide MOSFET.

[0038] To achieve the above-mentioned object and other related objects, the present invention also provides a test circuit for short-circuit protection of a power device, the test circuit comprising a short-circuit protection circuit and a peripheral test component circuit; the peripheral test component circuit comprises a power device;

[0039] The input end of the short-circuit protection circuit is connected to the output end of the power device; the output end of the short-circuit protection circuit is connected to the input end of the power device through a resistor;

[0040] The short-circuit protection circuit is the above-mentioned desaturation short-circuit protection circuit; the power device is a silicon carbide MOSFET.

[0041] Preferably, the peripheral test component further includes an isolation diode, a freewheeling diode and a load inductor;

[0042] The anode of the isolation diode is connected to the first end of the comparator, and the cathode of the isolation diode is connected to the drain of the silicon carbide MOSFET;

[0043] One end of the load inductor is connected to the cathode of the isolation diode, and the other end is connected to the power supply;

[0044] The freewheeling diode is connected in parallel with the load inductor, the anode of the freewheeling diode is connected to the cathode of the isolation diode, and the cathode of the freewheeling diode is connected to the power supply.

[0045] As described above, the desaturation short-circuit protection circuit, the power device short-circuit protection circuit and the test circuit of the present invention have the following beneficial effects:

[0046] The desaturated short-circuit protection circuit of the present invention is used to protect power devices, and includes a comparator, a time unit, a short-circuit detection unit and a processing unit; the blanking time set by the time unit is variable, and each time the short-circuit detection unit performs short-circuit detection, the short-circuit detection is performed after the blanking time of the previous switching cycle is reached, which can improve the rapidity of short-circuit detection and effectively avoid time waste caused by fixed blanking time and reduce the efficiency of short-circuit detection and short-circuit protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a schematic diagram of a desaturation protection circuit in the prior art.

[0048] Figure 2 Shown is a schematic diagram of a desaturation short-circuit protection circuit in the present invention.

[0049] Figure 3 Shown is a schematic diagram of a desaturation short-circuit protection circuit in the present invention.

[0050] Figure 4 Shown is a schematic diagram of a test circuit for short-circuit protection of a power device in an embodiment of the present invention.

[0051] Figure 5 Shown is a schematic diagram of the voltage drop time during the conduction process of the power device in the short-circuit protection test of the power device in an embodiment of the present invention.

[0052] Figure 6 Shown is a schematic diagram of the waveform changes of various signals during the short-circuit protection process in an embodiment of the present invention.

[0053] Component number description DETAILED DESCRIPTION

[0054] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0055] See also Figure 2-6 It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0056] In order to solve the contradiction between the faster switching speed of power devices and the longer fixed blanking time in the prior art, the present invention proposes a desaturation short-circuit protection circuit, the principle of which is as follows: Figure 2 As shown, mainly by adding a time unit with a variable blanking time, short circuit detection can be quickly performed after the power device is turned on and effective short circuit protection can be implemented, that is, on the basis of ensuring the reliability of short circuit protection of the power device, the efficiency of short circuit protection is improved. Based on the above technical concept, the present invention provides the following technical solutions: Example

[0057] Figure 3 The schematic diagram of the desaturation short circuit protection circuit of the present invention is shown below in combination with Figure 3 The technical concept of the present invention is introduced in detail. The present invention is a desaturation short-circuit protection circuit for protecting a power device, comprising a comparator 100, a time unit 200, a short-circuit detection unit 300 and a processing unit 400;

[0058] The first input terminal (positive input terminal) of the comparator 100 is connected to a detection voltage, which is the output voltage of the power device; the second input terminal (inverting input terminal) of the comparator 100 is connected to a reference voltage, which is the on-voltage of the power device; the comparator 100 outputs a comparison result between the detection voltage and the reference voltage;

[0059] The input end of the time unit 200 is connected to the output end of the comparator 100; the time unit 200 converts the time when the detection voltage is less than the reference voltage in the switching cycle of the comparator into a digital signal, and the digital signal is used to set the blanking time;

[0060] The short-circuit detection unit 300 is connected to the output end of the time unit 200 and the comparator 100; when the blanking time of the previous switching cycle is reached, the short-circuit detection unit 300 performs short-circuit detection on the power device based on the comparison result to obtain a detection result;

[0061] The input end of the processing unit 400 is connected to the output end of the short-circuit detection unit; the processing unit 400 performs short-circuit protection on the power device based on the detection result.

[0062] The desaturated short-circuit protection circuit of the present invention is used to protect power devices, and includes a comparator 100, a time unit 200, a short-circuit detection unit 300 and a processing unit 400; the comparator 100 outputs a comparison result between an output voltage of the power device and a reference voltage, and the time unit 200 converts the time when the detection voltage is less than the reference voltage in the switching cycle of the comparator 100 into a digital signal for setting a blanking time; at the same time, after reaching the blanking time of the previous switching cycle, the short-circuit detection unit 300 performs a short-circuit detection based on the comparison result to obtain a detection result, and finally the processing unit 400 performs short-circuit protection on the power device based on the detection result. Since the blanking time in the present invention is set according to the time when the detection voltage is less than the reference voltage in the switching cycle of the comparator 100, the blanking time is variable, and each time a short-circuit detection is performed, the short-circuit detection is started after reaching the blanking time of the previous switching cycle, which can improve the rapidity of the short-circuit detection and effectively avoid the time waste caused by the fixed blanking time and reduce the efficiency of short-circuit detection and short-circuit protection.

[0063] In the present invention, the detection voltage is the voltage dividing point of the voltage dividing branch, the voltage dividing branch includes a first resistor R1 and a second resistor R2, one end of the first resistor R1 is connected to the power supply VCC, and the other end is grounded through the second resistor R2, and the connection point between the first resistor R1 and the second resistor R2 is recorded as the voltage dividing point, that is, the detection voltage connected to the non-inverting input terminal of the comparator 100.

[0064] In the embodiment of the invention, taking the power device as a silicon carbide MOSFET as an example, the output voltage of the power device is the source-drain voltage of . The desaturation short-circuit protection circuit is described below.

[0065] The comparator 100 of the present invention sets the common mode level by using a resistor voltage divider, so that the SiC MOSFET withstands a higher source-drain voltage V before being turned on. DS , when SiC MOSFET is turned on, the detection voltage V DESAT is pulled down to the reference voltage V REF Below, the comparator output voltage V COMP V COMP The switching time reflects the SiC MOSFET source-drain voltage V DS Therefore, the present invention is based on the comparator output voltage V COMP The flip time is used for setting the blanking time in subsequent time units.

[0066] In an embodiment of the present invention, the time unit 200 includes a clock generation module Clk_gen and a storage setting module; the input end of the clock generation module Clk_gen is connected to the drive signal, and is used to generate a continuous pulse signal of a certain period according to the drive signal; the input end of the storage setting module is connected to the output end of the comparator 100, and the enable end of the storage setting module is connected to the output end of the clock generation module Clk_gen; it is used to convert the time when the detection voltage is less than the reference voltage in the switching cycle of the comparator 100 into a digital signal under the action of the continuous pulse signal, and set the blanking time based on the digital signal.

[0067] Specifically, the storage setting module includes an inverter, a first register Flag1 and a second register Flag2; the input end of the first register Flag1 is connected to the output ends of the comparator and the clock generation module, and is used to convert the time when the detection voltage is less than the reference voltage in the switching cycle of the comparator into a digital signal under the action of the continuous pulse signal; the input end of the second register Flag2 is connected to the output end of the first register Flag1, the enable end of the second register Flag2 is connected to the output end of the inverter, and the input end of the inverter is connected to the input end of the clock generation module Clk_gen; the digital signal is copied to the second register Flag2 at the rising edge of the switching cycle.

[0068] The time unit of the present invention, its time generating module Clk_gen generates a certain period T under the action of the driving signal CLKThe first register Flag1 of the storage setting module records the time when the detection voltage is less than the reference voltage in the switching cycle of the comparator 100 under the action of the continuous pulse signal output by the time generation module Clk_gen, and converts it into a digital signal data1 for storage; then the first register Flag1 is set to the source-drain voltage V DS At the rising edge, the digital signal data1 is copied to the second register Flag2 for setting the blanking time in the next switching cycle, that is, the digital signal Data2 in the second register Flag2 determines the start time of the short circuit detection unit. It should be noted that for the first switching cycle when the system is first powered on, the initial value of the digital signal data2 in the second register Flag2 is all 1, corresponding to the longest blanking time.

[0069] In the embodiment of the present invention, the first register Flag1 and the second register Flag2 are both 8 bits. As another implementation, the first register Flag1, the second register Flag2 and the period T CLK Set according to actual application requirements.

[0070] In the present invention, the short circuit detection unit 300 includes a controller Ctrl and a first logic AND gate AND1;

[0071] The controller Ctrl receives the driving signal and is connected to the output end of the time unit; it is used to output an enable signal after the blanking time of the previous switching cycle is reached;

[0072] The first input end of the first logic AND gate AND1 is connected to the output end of the controller Ctrl, and the second input end of the first logic AND gate AND1 is connected to the output end of the comparator 100; when the enable signal is valid, the output signal of the comparator 100 is output.

[0073] In the process of short-circuit protection during the conduction process of SiC MOSFET, under the action of the driving signal, when the blanking time of the previous switching cycle is reached, the controller Ctrl controls the first logic AND gate AND1 of the short-circuit detection unit to perform short-circuit detection on the power device SiC MOSFET based on the comparison result between the detection voltage output by the comparator 100 and the reference voltage. After the short-circuit detection unit is turned on, the controller Ctrl outputs a level V S1 Pull high and output an enable signal to the first logic AND gate AND1. When the enable signal is valid, the first logic AND gate AND1 outputs the output signal V of the comparator 100. S2 , the first logic AND gate AND1 outputs a signal V S2 It is essentially the output voltage V of the comparator 100 COMP; If the source-drain voltage of SiC MOSFET V DS If there is no normal decline, then V COMP is high level, then V S2 is high level, that is, the output result of the first logic AND gate AND1 is high level, then the detection result Fault output by the short circuit detection unit is high level. When the detection result Fault is high level, it means that after the short circuit detection by the short circuit detection unit, it is determined that the SiC MOSFET is short-circuited.

[0074] Since the source-drain voltage V DS Switch oscillation can easily lead to false triggering of the short-circuit detection unit. Therefore, as a preferred implementation of the present invention, the detection unit also includes a delayer, a trigger module and a second logic AND gate AND2; the input end of the delayer is connected to the output end of the first logic AND gate; it is used to set the delay time; the clock end of the trigger module is connected to the output end of the delayer, and the signal input end of the trigger module is connected to the output end of the comparator 100; after the delay time is reached, the trigger module outputs the current output signal of the comparator 100; the input end of the second logic AND gate is respectively connected to the output end of the first logic AND gate and the trigger module; the output signals of the first logic AND gate and the trigger module are ANDed to obtain the detection result.

[0075] The trigger module of the present invention includes at least one trigger. In an embodiment of the present invention, the trigger module includes three triggers, namely a first trigger, a second trigger and a third trigger; the first trigger DFF1 is connected to the output end of the delay device and the comparator 100, and is triggered after the first set delay time is reached, and the first trigger DFF1 outputs the current output signal of the comparator; the second trigger DFF2 is connected to the output end of the delay device and the comparator 100, and is triggered after the second set delay time is reached, and the second trigger DFF2 outputs the current output signal of the comparator; the third trigger DFF3 is connected to the output end of the delay device and the comparator 100, and is triggered after the third set delay time is reached, and the third trigger DFF3 outputs the current output signal of the comparator.

[0076] Specifically, after the short-circuit detection unit is turned on, the controller Ctrl outputs a level V S1 Pull high, the first logic AND gate AND1 output level V S2 It is essentially the output voltage V of the comparator 100 COMP ; If the source-drain voltage of SiC MOSFET V DSIf there is no normal decline, then V COMP is high level, then V S2 is high level, that is, the output result of the first logic AND gate AND1 is high level, and then every fixed delay time, the input voltage V S3 , the input voltage V of the second trigger DFF2 S4 and the input voltage V of the third flip-flop DFF3 S3 The output voltages of the first trigger DFF1, the second trigger DFF2 and the third trigger DFF3 are pulled up in sequence; finally, the second logic AND gate AND2 obtains the detection result of the short-circuit detection unit Fault as a high level according to the output signal of the first logic AND gate AND1D and the current output signal of the trigger module. When the detection result is Fault as a high level, it means that after the short-circuit detection of the short-circuit detection unit, it is judged that the SiC MOSFET has a short circuit.

[0077] In a preferred embodiment of the present invention, the SiC MOSFET source-drain voltage can be prevented from V DS Switch oscillation causes false triggering of the short-circuit detection unit, thereby improving the anti-interference ability; in addition, although the judgment unit will increase the short-circuit detection and short-circuit protection time, compared with the traditional technical methods in the prior art, the delay reduced by the blanking time is greater than the delay increased by the judgment unit. Therefore, while increasing the anti-interference ability, the rapidity of the short-circuit protection can also be guaranteed.

[0078] Based on the high-level signal of the short-circuit detection result Fault, in order to ensure the safety of the device and its circuit, the power device SiC MOSFET needs to be short-circuited. The present invention performs short-circuit protection on the power device SiC MOSFET based on the high-level signal of the detection result Fault by the processing unit.

[0079] Specifically, the processing unit includes a logic processing module, a level shifting module and an output driving module; the input end of the logic processing module receives a driving signal and is connected to the output end of the short-circuit detection unit; and is used to process the detection result to obtain a logic level signal; the level shifting module is connected to the output end of the logic processing module; and is used to process the logic level signal to obtain a driving level signal; the input end of the output driving module is connected to the output end of the level shifting module, and the output end of the output driving module is used to connect to the control end of the power device; and is used to convert and process the driving level signal to obtain a driving voltage signal, and the driving voltage signal can perform short-circuit protection on the power device.

[0080] Once the processing unit of the present invention detects the result of the Fault signal and pulls it high, the driving voltage signal V OUT Specifically, the logic processing module is responsible for processing the detection result Fault output by the short-circuit detection unit and processing the detection result Fault to obtain a logic level signal, and then the level shift module processes the logic level signal to obtain a drive level signal, and finally the output drive module converts the drive level signal to obtain a drive voltage signal. OUT Provide short-circuit protection for power device SiC MOSFET. Example

[0081] The present invention also provides a power device short-circuit protection circuit, comprising a short-circuit protection circuit and a power device; the input end of the short-circuit protection circuit is connected to the output end of the power device; the output end of the short-circuit protection circuit is connected to the control end of the power device; the short-circuit protection circuit is the above-mentioned desaturation short-circuit protection circuit. The specific structure and principle of the desaturation short-circuit protection circuit have been introduced in detail in the first embodiment, and will not be described in detail here.

[0082] In an embodiment of the present invention, the power device is a silicon carbide MOSFET. Example

[0083] The present invention also provides a Figure 5 The test circuit for short-circuit protection of a power device shown in the figure comprises a short-circuit protection circuit and a peripheral test component circuit, wherein the peripheral test component circuit comprises a power device; the input end of the short-circuit protection circuit is connected to the output end of the power device; the output end of the short-circuit protection circuit is connected to the input end of the power device through a resistor; the short-circuit protection circuit is the above-mentioned desaturation short-circuit protection circuit; and the power device is a silicon carbide MOSFET. The specific structure and principle of the desaturation short-circuit protection circuit have been introduced in detail in the first embodiment, and will not be described in detail here.

[0084] The peripheral test component circuit also includes an isolation diode DS, a freewheeling diode DL and a load inductor L; the anode of the isolation diode DS is connected to the voltage dividing point of the voltage dividing branch, the cathode of the isolation diode DS is connected to the drain of the silicon carbide MOSFET, one end of the load inductor L is connected to the cathode of the isolation diode DS, and the other end is connected to the power supply V BUS , the freewheeling diode DL is connected in parallel with the load inductor L, that is, the anode of the freewheeling diode DL is connected to the cathode of the isolation diode DS, and the cathode of the freewheeling diode DS is connected to the power supply V BUS .

[0085] Figure 5This is a schematic diagram of the voltage drop time during the power device conduction process in the power device short-circuit protection test. Figure 6 The waveform change diagram of each signal during the short-circuit protection process is shown below. The source-drain voltage V of SiC MOSFET is measured during the short-circuit protection test process. DS Analyze the decline and other signal changes:

[0086] In the embodiment of the present invention, the DESAT input terminal of the comparator uses a resistor voltage divider to set the common mode level. The SiC MOSFET is subjected to a higher source-drain voltage before being turned on, and the common mode level is lower than the SiC MOSFET source-drain voltage V DS , at this time, the isolation diode DS is in reverse biased off state; after the SiC MOSFET is turned on, when the source-drain voltage V DS When the common-mode voltage is lower than the set level, the isolation diode DS is forward-conducted and the detection voltage V DESAT is pulled down to the threshold reference voltage V REF Below, the comparator output voltage V COMP The first register Flag1 of the time unit records the output voltage V of the comparator 100. COMP The time when the flip occurs is recorded as the digital signal Data1, and then copied to the second register Flag2 for setting the blanking time in the next switching cycle; after the short-circuit detection unit reaches the blanking time of the previous switching cycle, the controller Ctrl turns on and controls the first logic AND gate AND1 to perform short-circuit detection on the power device based on the comparison result to obtain an output result, and then obtains a judgment result under the delayed judgment of the judgment unit, and finally the second logic AND gate AND2 obtains the detection result Fault of the short-circuit detection unit according to the output result of the first logic AND gate AND1D inputted therein and the judgment result of the trigger module. If the detection result Fault is a high level, the driving voltage signal V output after being processed by the processing unit is OUT It will be pulled low, thereby turning off the SiC MOSFET and achieving the purpose of short-circuit protection.

[0087] In summary, since the blanking time in the present invention is set according to the time when the detection voltage is less than the reference voltage in the switching cycle of the comparator 100, the blanking time is variable, and each time a short-circuit detection is performed, the short-circuit detection is started after the blanking time of the previous switching cycle is reached, which can improve the rapidity of short-circuit detection and effectively avoid the time waste caused by the fixed blanking time and reduce the efficiency of short-circuit detection and short-circuit protection. In addition, the judgment unit added to the short-circuit detection unit will increase the short-circuit detection and short-circuit protection time, but compared with the traditional technical method in the prior art, the delay reduced by the blanking time is greater than the delay increased by the judgment unit. Therefore, while increasing the anti-interference ability, the rapidity of short-circuit protection can also be guaranteed. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has a high industrial utilization value.

[0088] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A desaturation short-circuit protection circuit for protecting a power device, characterized in that: It includes a comparator, a time unit, a short circuit detection unit and a processing unit; The first input terminal of the comparator is connected to a detection voltage, which is the output voltage of the power device; the second input terminal of the comparator is connected to a reference voltage, which is the on-voltage of the power device; the comparator outputs a comparison result between the detection voltage and the reference voltage; The input end of the time unit is connected to the output end of the comparator; the time unit converts the time when the detection voltage is less than the reference voltage in the switching cycle of the comparator into a digital signal, and the digital signal is used to set the blanking time; The short-circuit detection unit is connected to the time unit and the output end of the comparator; when the blanking time of the previous switching cycle is reached, the short-circuit detection unit performs short-circuit detection on the power device based on the comparison result to obtain a detection result; The input end of the processing unit is connected to the output end of the short-circuit detection unit; the processing unit performs short-circuit protection on the power device based on the detection result.

2. The desaturation short-circuit protection circuit according to claim 1, characterized in that: The time unit includes a clock generation module and a storage setting module; The input end of the clock generating module is connected to the driving signal, and is used to generate a continuous pulse signal of a certain period according to the driving signal; The storage setting module is connected to the comparator and the output end of the clock generating module; It is used to convert the time when the detection voltage is less than the reference voltage in the switching period of the comparator into a digital signal under the action of the continuous pulse signal, and set the blanking time based on the digital signal.

3. The desaturation short-circuit protection circuit according to claim 2, characterized in that: The storage setting module includes an inverter, a first register and a second register; The input end of the first register is connected to the output end of the comparator and the clock generation module, and is used for converting the time when the detection voltage is less than the reference voltage in the switching cycle of the comparator into a digital signal under the action of the continuous pulse signal; The input end of the second register is connected to the output end of the first register, the enable end of the second register is connected to the output end of the inverter, and the input end of the inverter is connected to the input end of the clock generation module; the digital signal is copied to the second register at the rising edge of the switching cycle.

4. The desaturation short-circuit protection circuit according to claim 1, characterized in that: The short circuit detection unit includes a controller and a first logic AND gate; The controller receives the driving signal and is connected to the output end of the time unit; it is used to output an enable signal after reaching the blanking time of the previous switching cycle; The first input end of the first logic AND gate is connected to the output end of the controller, and the second input end of the first logic AND gate is connected to the output end of the comparator; when the enable signal is valid, the output signal of the comparator is output.

5. The desaturation short-circuit protection circuit according to claim 4, characterized in that: The short circuit detection unit also includes a delay device, a trigger module and a second logic AND gate; The input end of the delay device is connected to the output end of the first logic AND gate; and is used to set the delay time; The clock end of the trigger module is connected to the output end of the delay device, and the signal input end of the trigger module is connected to the output end of the comparator; after the delay time is reached, the trigger module outputs the current output signal of the comparator; The input ends of the second logic AND gate are respectively connected to the output ends of the first logic AND gate and the trigger module; an AND operation is performed on the output signals of the first logic AND gate and the trigger module to obtain the detection result.

6. The desaturation short-circuit protection circuit according to claim 5, characterized in that: The trigger module includes three triggers, namely a first trigger, a second trigger and a third trigger; The first trigger is connected to the output end of the delay device and the comparator, and is triggered after reaching the first set delay time, and the first trigger outputs the current output signal of the comparator; The second trigger is connected to the output end of the delay device and the comparator, and is triggered after reaching the second set delay time, and the second trigger outputs the current output signal of the comparator; The third trigger is connected to the output ends of the delay device and the comparator, and is triggered after a third set delay time is reached. The third trigger outputs a current output signal of the comparator.

7. The desaturation short-circuit protection circuit according to claim 1, characterized in that: The processing unit includes a logic processing module, a level shifting module and an output driving module; The input end of the logic processing module receives the driving signal and is connected to the output end of the short circuit detection unit; it is used to process the detection result to obtain a logic level signal; The level shift module is connected to the output end of the logic processing module; Used to process the logic level signal to obtain a driving level signal; The input end of the output driving module is connected to the output end of the level shifting module, and the output end of the output driving module is used to connect to the control end of the power device; The driving level signal is converted and processed to obtain a driving voltage signal, and the driving voltage signal can perform short-circuit protection on the power device.

8. A power device short-circuit protection circuit, characterized in that: Including short circuit protection circuit and power devices; The input end of the short-circuit protection circuit is connected to the output end of the power device; the output end of the short-circuit protection circuit is connected to the control end of the power device; The short-circuit protection circuit is the desaturated short-circuit protection circuit according to any one of claims 1 to 7. 9 . The power device short-circuit protection circuit according to claim 8 , wherein the power device is a silicon carbide MOSFET.

10. A test circuit for short-circuit protection of a power device, characterized in that: The test circuit includes a short circuit protection circuit and a peripheral test component circuit; the peripheral test component circuit includes a power device; The input end of the short-circuit protection circuit is connected to the output end of the power device; the output end of the short-circuit protection circuit is connected to the input end of the power device through a resistor; The short-circuit protection circuit is the desaturated short-circuit protection circuit according to any one of claims 1 to 7; and the power device is a silicon carbide MOSFET.

11. The test circuit for short-circuit protection of a power device according to claim 10, wherein the peripheral test component further comprises an isolation diode, a freewheeling diode and a load inductor; The anode of the isolation diode is connected to the first end of the comparator, and the cathode of the isolation diode is connected to the drain of the silicon carbide MOSFET; One end of the load inductor is connected to the cathode of the isolation diode, and the other end is connected to the power supply; The freewheeling diode is connected in parallel with the load inductor, the anode of the freewheeling diode is connected to the cathode of the isolation diode, and the cathode of the freewheeling diode is connected to the power supply.

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