Monitoring circuit and monitoring method for grid characteristics of power gallium nitride device

Abstract

According to the monitoring circuit and the monitoring method for the grid characteristics of the power gallium nitride device, a constant micro current source is monitored to charge a grid capacitor Cgss of the power gallium nitride device, and the change of the grid capacitor Cgss of the power gallium nitride device is calculated by using a charging curve of the constant micro current source, so that the reliability of the grid of the power gallium nitride device is represented; the basic circuit comprises an isolation power supply unit, a constant micro current source, a signal comparison unit and a signal operation unit. The isolated power supply unit is used for supplying power to other units; the constant micro-current source injects constant grid current into the power gallium nitride device; the signal comparison unit is used for comparing the grid voltage vgss of the power gallium nitride device with a reference preset value Vthi; and the signal operation unit is used for controlling the output of the constant micro current source and feeding back a monitoring signal to the microprocessor. Therefore, the aging state of the power gallium nitride device can be accurately evaluated.

Description

Technical Field

[0001] The present invention relates to the technical field of GaN device performance detection, and in particular to a monitoring circuit and a monitoring method for gate characteristics of a power gallium nitride device. Background Art

[0002] At present, power electronic devices are mainly based on silicon materials. After more than 60 years of development, the performance of silicon-based power electronic devices has reached its limit. In recent years, power electronic devices based on third-generation wide bandgap semiconductor materials such as silicon carbide (SiC) and gallium nitride (GaN) have developed rapidly. Among them, the hexagonal wurtzite structure of GaN crystal makes it superior to silicon materials in bandgap width, breakdown electric field strength, and electron saturation drift rate. Power gallium nitride devices are high-efficiency, high-voltage, high-switching-speed, and high-power-density devices. Its power range ranges from several million to hundreds of megawatts, and it can be used in various complex power electronic devices. Power electronic devices are the core components of power electronic devices, and are also one of the most fragile and easily damaged components in power electronic devices.

[0003] Generally, GaN devices are depletion-mode devices. Considering the safe operation of the device and the simple design of the driving circuit, users tend to choose enhancement-mode devices. While technologies such as p-GaN gate and fluorine ion implantation realize enhancement-mode GaN devices, they will also produce a series of reliability problems. The current use of GaN devices is limited, which is also caused by its reliability issues. The operation of the device depends on the driving signal. Under the condition of high-frequency driving signal and high leakage stress, the threshold voltage and gate leakage current of the GaN device will change, resulting in failure of the structure and performance of the device.

[0004] At present, the gate characteristics of GaN devices are mainly tested by electrical performance test and optical characterization test. Among them, electrical performance test is mainly achieved by measuring the IV curve of the device, while parameter acquisition relies on expensive instruments such as semiconductor analyzers and source measurement units (SMUs). Due to the large size of the instrument, the existing detection methods are mostly laboratory tests, which are difficult to apply to the online detection of device reliability in industrial sites. Optical characterization test is a non-contact measurement method that can not only perform non-destructive testing on the device, but also has spatial resolution capabilities to determine the failure location and defect type of the device. However, the use of optical detection requires that the gate or substrate of the device be made of optically transparent materials, or that the metal electrode be removed before the test. For most devices made of conventional materials, their optical detection has certain limitations. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a monitoring circuit and a monitoring method for gate characteristics of a power GaN device, which can accurately evaluate the aging state of the power GaN device.

[0006] The technical solution adopted by the present invention is:

[0007] The monitoring circuit of the gate characteristics of the power GaN device includes:

[0008] Isolation power supply unit, constant micro-current source, signal comparison unit, signal operation unit;

[0009] The isolated power supply unit is respectively connected to the constant micro-current source, the signal comparison unit, and the signal operation unit to supply power to these units;

[0010] The constant micro-current source is connected to the signal comparison unit and the power gallium nitride device respectively, and the constant micro-current source injects a constant gate current into the power gallium nitride device according to the output control signal of the signal comparison unit received;

[0011] The signal comparison unit is connected to the signal operation unit and the power GaN device respectively, and the signal comparison unit is used to compare the gate voltage v of the power GaN device. gss With the reference preset value V sthi Performing comparison and outputting the comparison result to the signal operation unit;

[0012] The signal operation unit is connected to the constant micro-current source, the signal comparison unit and the microprocessor respectively. The signal operation unit outputs a control signal to the constant micro-current source according to the received result, and feeds back a monitoring signal to the microprocessor at the same time.

[0013] The signal operation unit receives the output control signal sc of the microprocessor and performs operation processing on the result output by the signal comparison unit to obtain the output control signal ccs, which is then output to the constant micro current source; the signal operation unit processes the result output by the received signal comparison unit to obtain the feedback monitoring signal tp, and then feeds back the signal to the microprocessor;

[0014] The output end of the constant micro-current source is connected to the power GaN device. When the power GaN device is in the off state, the constant micro-current source injects a constant gate current into the power GaN device when the output control signal CCS is at a high level, thereby monitoring the gate characteristics of the power GaN device. When the output control signal CCS is at a low level, the constant micro-current source stops injecting a constant gate current into the power GaN device.

[0015] The constant micro-current source includes a single-pole double-throw switch, operational amplifiers A1 and A2, resistors R, and resistors R set , capacitor C and N-type MOSFET;

[0016] The SEL end of the single-pole double-throw switch is connected to the output end of the digital isolator Diso1, the S2 end of the single-pole double-throw switch is connected to a +1.2V voltage, and the S1 end of the single-pole double-throw switch is grounded; the fixed end of the single-pole double-throw switch is connected to the positive input end of the operational amplifier A1; the reverse input end of the operational amplifier A1 is respectively connected to one end of the resistor R and one end of the capacitor C;

[0017] The other end of the resistor R is connected to the output end of the operational amplifier A2, and the other end of the capacitor C is connected to the resistor R set One end of the amplifier is connected to the positive input terminal of the operational amplifier A2;

[0018] The resistor R set The other end is connected to the gate of the power GaN device, and the source of the power GaN device is grounded;

[0019] The output end of the operational amplifier A1 is connected to the positive input end of the operational amplifier A2, the reverse input end of the operational amplifier A2 is connected to the source of the N-type MOSFET, and the drain of the N-type MOSFET is connected to the output -v m The output interface of the voltage value is connected and grounded; the gate of the N-type MOSFET is connected to the signal operation unit output signal ccs through an inverter.

[0020] The signal comparison unit includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, and a hysteresis comparator Comp1; one end of the resistor R1 is used to connect to the gate of the power gallium nitride device, the other end of the resistor R1 is respectively connected to the reverse input end of the hysteresis comparator Comp1 and one end of the resistor R2, and the other end of the resistor R2 is respectively connected to the power isolation unit capable of outputting -v m The output interface of the voltage value is connected to the ground terminal; one end of the resistor R3 is connected to the power isolation unit to output +v cc The output interface of the voltage value is connected, the other end of the resistor R3 is connected to one end of the resistor R5, one end of the resistor R4, and the in-phase input end of the hysteresis comparator Comp1, the other end of the resistor R5 is connected to the output end of the hysteresis comparator Comp1, the other end of the resistor R4 is grounded, and the power pins of the hysteresis comparator Comp1 are respectively connected to the power isolation unit that can output +v cc Output interface connection of voltage value and ground terminal connection;

[0021] The signal comparison unit includes a resistor R6, a resistor R7, a resistor R8, a resistor R9, a resistor R10, and a hysteresis comparator Comp2; one end of the resistor R6 is used to connect to the gate of the power gallium nitride device, the other end of the resistor R6 is simultaneously connected to the reverse input end of the hysteresis comparator Comp2 and one end of the resistor R7, and the other end of the resistor R7 is respectively connected to the inverting input end of the power isolation unit that can output -v m The output interface of the voltage value is connected to the ground terminal; one end of the resistor R8 is connected to the power isolation unit that can output +v cc The output interface of the voltage value is connected, the other end of the resistor R8 is connected to one end of the resistor R10, one end of the resistor R9 and the in-phase input end of the hysteresis comparator Comp2, the other end of the resistor R10 is connected to the output end of the hysteresis comparator Comp2, the other end of the resistor R9 is grounded, and the power pins of the hysteresis comparator Comp2 are respectively connected to the power isolation unit that can output +v cc Output interface connection of voltage value and ground terminal connection.

[0022] The first part of the signal operation unit includes a NAND gate NaS, a NAND gate NaR, an AND gate AND and a digital isolator Diso1; the NAND gate NaS and the NAND gate NaR constitute an SR latch, one input end of the NAND gate NaS is connected to the microprocessor output control signal Sc, the other input end of the NAND gate NaS is connected to the output end of the NAND gate NaR, one input end of the NAND gate NaR is connected to the output end of the hysteresis comparator Comp1, the other input end of the NAND gate NaR is simultaneously connected to the output end of the NAND gate NaS and one input end of the AND gate AND, the other input end of the AND gate AND is connected to the microprocessor output control signal Sc, the output end of the AND gate AND is connected to the input end of the digital isolator Diso1, and the output end of the digital isolator Diso1 is connected to a constant micro-current source;

[0023] The second part of the signal operation unit includes a NOT gate, an AND gate AND1, and an AND gate AND2. The input end of the NOT gate is connected to the output end of the hysteresis comparator comp2, the output end of the NOT gate is connected to the input end of the AND gate AND1, the other input end of the AND gate AND1 is connected to the output end of the hysteresis comparator, the output end of the AND gate AND1 is connected to the input end of the AND gate AND2, the other input end of the AND gate AND2 is connected to the signal operation unit AND gate input signal cpo, and the output end of the AND gate AND2 is connected to the feedback monitoring signal tp.

[0024] The method for monitoring the gate characteristics of power GaN devices is to monitor the gate capacitance C of the power GaN device by a constant micro-current source. g_ss The charging curve is used to calculate the gate capacitance C of the power GaN device g_ss The change of is used to characterize the reliability of the gate of the power GaN device.

[0025] When the power GaN device is turned off, the gate voltage v gss Lower than the reference value V sthi ;

[0026] The gate voltage v of the power GaN device gss With the reference preset value V sth1 The comparison result between them is output to the signal operation unit, wherein the signal operation unit sends a control signal to the constant micro-current source so that the constant micro-current source injects a constant gate current into the power gallium nitride device. At this time, the gate voltage v gss Gradually increases, when the signal comparison unit monitors the gate voltage v of the power GaN device gss Reach the reference preset value V sth1 When the result is output to the signal operation unit, the signal operation unit sends a control signal to the constant micro-current source to stop the constant micro-current source from injecting the constant gate current into the power gallium nitride device; the gate voltage of the power gallium nitride device changes from v gss Increase to the reference preset value V sth1 During this period, it increases to V sth2 、V sth3 When the signal comparison unit outputs the comparison result to the signal operation unit, the signal operation unit processes it to obtain the feedback monitoring signal tp required by the microprocessor, that is, the gate voltage is V sth2 Increase to V sth3 time;

[0027] The microprocessor captures the feedback monitoring signal tp, and the constant micro-current source injects a constant gate current into the power GaN device to make the gate voltage change from v sth2 Increase to v sth3 The time Δt is calculated, and the charging time Δt and voltage change are calculated, Δu = V sth3 -V sth2 , the gate capacitance C of the power GaN device is characterized by the charging current i g_ss .

[0028] The present invention provides a monitoring circuit and a monitoring method for gate characteristics of a power gallium nitride device, and the technical effects are as follows:

[0029] 1) The monitoring circuit of the present invention has the potential for online monitoring. At the same time, the circuit has high integration, the monitoring method is easy to implement, and the reliability assessment of the power gallium nitride device is accurate, thereby improving the reliability of the power gallium nitride device, and has practical application value.

[0030] 2) The isolated power supply unit of the gate characteristic monitoring circuit of the present invention is composed of a power supply module with isolation function, which can meet all power supply requirements of the monitoring circuit in conjunction with a reference voltage chip and a linear regulator; at the same time, it realizes isolation between the constant micro-current source, the signal comparison and operation unit, and the microprocessor, and has the advantages of simple structure, multiple output amplitudes and high integration.

[0031] 3) The constant micro-current source of the gate characteristic monitoring circuit of the present invention is composed of a precision low-drift operational amplifier and an instrument amplifier, and has high output accuracy; the circuit structure is relatively simple and the adjustment response speed is fast; in addition, the resistor R is changed set It can realize the adjustment of the set current and has the advantages of wide output range, etc.

[0032] 4) The signal comparison unit of the gate characteristic monitoring circuit of the present invention adopts a hysteresis comparison structure, which provides noise suppression and stability enhancement functions by introducing hysteresis characteristics, can avoid flipping due to slight changes in the input signal, and has the advantage of stable and reliable comparison results.

[0033] 5) The signal operation unit of the gate characteristic monitoring circuit of the present invention is composed of a basic logic gate circuit. The SR latch constructed by the NAND gate ensures the correctness of the circuit working timing. The latch output can simultaneously meet the operation requirements of the output control signal CCS and the feedback monitoring signal TP, so that the signal operation unit has the advantages of simple structure, fast operation speed and low cost.

[0034] 6) The monitoring method of the present invention uses the gate capacitance of the gallium nitride device as a characteristic parameter, and uses a constant micro-current source to charge the gate capacitance to realize monitoring. In view of the small gate capacitance of the gallium nitride device, a constant micro-current source of tens of μA is designed to realize the charging of the gate-source capacitance. In order to avoid the device being turned on during the measurement process and affecting the overall operation of the equipment, a reasonable capacitor charging range is selected to ensure that the device operates in the off state during the measurement process. In order to eliminate the influence of the circuit adjustment process and ensure the accuracy of the measurement results, two hysteresis comparators are used to collect part of the data of the charging process to calculate the measurement results. Using a microprocessor to collect the measurement time and complete the calculation, the monitoring no longer relies on large and expensive equipment such as semiconductor parameter analyzers, and has the potential to realize online monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The structure block diagram of the monitoring circuit of the gate characteristics of the power gallium nitride device of the present invention.

[0036] Figure 2The circuit schematic diagram of the constant micro-current source in the monitoring circuit of the gate characteristics of the power gallium nitride device of the present invention.

[0037] FIG3( a ) is a circuit schematic diagram of a signal comparison unit (comparator Comp1 with hysteresis) in a monitoring circuit for gate characteristics of a power GaN device according to the present invention;

[0038] FIG3( b ) is a circuit schematic diagram of a signal comparison unit (comparator Comp2 with hysteresis) in a monitoring circuit for gate characteristics of a power GaN device according to the present invention.

[0039] FIG4( a ) is a circuit schematic diagram of the first part of the signal operation unit in the monitoring circuit of the gate characteristics of the power gallium nitride device of the present invention;

[0040] FIG4( b ) is a circuit schematic diagram of the second part of the signal operation unit in the monitoring circuit for the gate characteristics of the power gallium nitride device of the present invention.

[0041] Figure 5 The schematic diagram of the monitoring circuit for the gate characteristics of the power gallium nitride device of the present invention is shown in FIG.

[0042] Figure 6 It is a timing diagram of the method for monitoring gate characteristics of a power gallium nitride device of the present invention.

[0043] Figure 7 The figure is an experimental waveform diagram obtained by using the method for monitoring gate characteristics of a power gallium nitride device of the present invention. DETAILED DESCRIPTION

[0044] like Figure 1 to Figure 6 As shown, the monitoring circuit of the gate characteristics of the power gallium nitride device includes: an isolation power supply unit, a constant micro-current source, a signal comparison unit, and a signal operation unit;

[0045] The isolated power supply unit is used to supply power to the constant micro-current source, the signal comparison unit, and the signal operation unit;

[0046] The constant micro-current source injects a constant gate current into the power gallium nitride device according to the control signal received from the signal operation unit;

[0047] The signal comparison unit is used to compare the gate voltage v of the power gallium nitride device gss With the reference preset value V sthi Performing comparison and outputting the comparison result to the signal operation unit;

[0048] The signal operation unit outputs a control signal to the constant micro-current source according to the received result, and feeds back a monitoring signal to the microprocessor at the same time.

[0049] The working principle of the present invention is:

[0050] When the power GaN device is turned off, the gate voltage v gss Lower than the reference value V sthi ;

[0051] The gate voltage v of the power GaN device gss With the reference preset value V sth1 The comparison result between them is output to the signal operation unit, wherein the signal operation unit sends a control signal to the constant micro-current source so that the constant micro-current source injects a constant gate current into the power gallium nitride device. At this time, the gate voltage v gss Gradually increases, when the signal comparison unit monitors the gate voltage v of the power GaN device gss Reach the reference preset value V sth1 When the result is output to the signal operation unit, the signal operation unit sends a control signal to the constant micro-current source to stop the constant micro-current source from injecting the constant gate current into the power gallium nitride device; the gate voltage of the power gallium nitride device changes from v gss Increase to the reference preset value V sth1 During this period, it increases to V sth2 、V sth3 When the signal comparison unit outputs the comparison result to the signal operation unit, the signal operation unit processes the result to obtain the feedback monitoring signal tp required by the microprocessor (that is, the gate voltage is V sth2 Increase to V sth3 time);

[0052] The microprocessor captures the feedback monitoring signal tp (the constant micro-current source injects a constant gate current into the power GaN device to make the gate voltage change from V sth2 Increase to V sth3 The charging time Δt and voltage change (Δu = V sth3 -V sth2 ), the gate capacitance C is calculated by the charging current i g_ss .

[0053] In this embodiment, a microprocessor is further included, and the microprocessor outputs a control signal sc to the signal operation unit, and the signal operation unit performs operation processing on the received output control signal sc and the results cp, cp1 and cp2 output by the signal comparison unit to obtain an output control signal ccs and a feedback monitoring signal tp, wherein the output control signal ccs is output to the constant micro current source, and the feedback monitoring signal tp is output to the microprocessor;

[0054] In this embodiment, the isolated power supply unit has an input interface and multiple output interfaces, the input interface of the isolated power supply unit is used to connect to an external power supply, and the output interface of the isolated power supply unit is respectively connected to a constant micro current source, a signal comparison unit, and a signal operation unit, wherein the output interface of the isolated power supply unit and the constant micro current source can output -v m Voltage value.

[0055] In this embodiment, the constant micro current source includes a single-pole double-throw switch, operational amplifiers A1 and A2, resistors R and R set , capacitor C and N-type MOSFET. The SEL end of the single-pole double-throw switch is connected to the output end of the digital isolator Diso1, the S2 end is connected to the +1.2V voltage, the S1 end is grounded, and the other end of the single-pole double-throw switch is connected to the positive input end of the operational amplifier A1; the reverse input end of the operational amplifier A1 is connected to one end of the resistor R, and the reverse input end of the operational amplifier A1 is connected to one end of the capacitor C, the other end of the resistor R is connected to the output end of the operational amplifier A2, and the other end of the capacitor C is connected to the resistor R set One end of the resistor R set The other end is connected to the gate of the power GaN device, the source of the power GaN device is grounded, the output end of the operational amplifier A1 is connected to the positive input end of the operational amplifier A2, the reverse input end of the operational amplifier A2 is connected to the source of the N-type MOSFET, and the drain of the N-type MOSFET is connected to the output -v m The output interface of the voltage value is connected and grounded; the gate of the N-type MOSFET is connected to the output signal ccs of the signal operation unit through an inverter.

[0056] In this embodiment, the signal comparison unit includes a resistor R1 / R6, a resistor R2 / R7, a resistor R3 / R8, a resistor R4 / R9, a resistor R5 / R10, and a hysteresis comparator Comp1 / Comp2. One end of the resistor R1 / R6 is used to connect to the gate of the power gallium nitride device, and the other end of the resistor R1 / R6 is simultaneously connected to the reverse input end of the hysteresis comparator Comp1 / Comp2 and one end of the resistor R2 / R7. The other end of the resistor R2 / R7 is simultaneously connected to the power isolation unit that can output -v m The output interface of the voltage value and the grounding, one end of the resistor R3 / R8 and the power isolation unit can output +v ccThe output interface of the voltage value is connected, the other end of the resistor R3 / R8 is simultaneously connected to one end of the resistor R5 / R10, one end of the resistor R4 / R9 and the in-phase input end of the hysteresis comparator Comp1 / Comp2, the other end of the resistor R5 / R10 is simultaneously connected to the output end of the hysteresis comparator Comp1 / Comp2, the other end of the resistor R4 / R9 is grounded, and the two power pins of the hysteresis comparator Comp1 / Comp2 are respectively connected to the power isolation unit capable of outputting +v cc Output interface connection of voltage value and ground.

[0057] In this embodiment, the first part of the signal operation unit includes a NAND gate NaS, a NAND gate NaR, an AND gate AND and a digital isolator Diso1. The NAND gate NaS and the NAND gate NaR constitute an SR latch. One input end of the NAND gate NaS is connected to the microprocessor output control signal Sc, the other input end of the NAND gate NaS is connected to the output end of the NAND gate NaR, one input end of the NAND gate NaR is connected to the output end of the hysteresis comparator Comp1, the other input end of the NAND gate NaR is simultaneously connected to the output end of the NAND gate NaS and one input end of the AND gate AND, the other input end of the AND gate AND is connected to the microprocessor output control signal Sc, the output end of the AND gate AND is connected to the input end of the digital isolator Diso1, and the output end of the digital isolator Diso1 is connected to a constant micro-current source.

[0058] The second part of the signal operation unit includes a NOT gate, an AND gate AND1, and an AND gate AND2. The input end of the NOT gate is connected to the output end of the hysteresis comparator comp2, the output end of the NOT gate is connected to the input end of the AND gate AND1, the other input end of the AND gate AND1 is connected to the output end of the hysteresis comparator, the output end of the AND gate AND1 is connected to the input end of the AND gate AND2, the other input end of the AND gate AND2 is connected to the signal operation unit AND gate input signal cpo, and the output end of the AND gate AND2 is connected to the feedback monitoring signal tp.

[0059] A method for monitoring gallium nitride gate characteristics comprises the following steps:

[0060] Step 1): When the power GaN device is turned off, the gate voltage v of the GaN power device is gss Less than the preset value V sthi ;

[0061] Step 2): The signal comparison unit compares the gate voltage v of the power GaN device in step 1) gss With the reference preset value V sth1The comparison result is output to the signal operation unit, and the signal operation unit sends a control signal to the constant micro current source, so that the constant micro current source injects a constant gate current into the power GaN device. At this time, the gate voltage v gss Gradually increases, when the signal comparison unit monitors the gate voltage v of the power GaN device gss Increase to the reference preset value V sth1 When the result is output to the signal operation unit, the signal operation unit sends a control signal to the constant micro current source, so that the constant micro current source stops injecting a constant gate current into the power GaN device; the gate voltage of the power GaN device is changed from v gss Increase to the reference preset value V sth1 During the process, it increases to V sth2 and V sth3 When the signal comparison unit outputs the comparison result to the signal operation unit, the signal operation unit processes the result to obtain the feedback output signal tp required by the microprocessor, that is, the gate voltage is V sth2 Growth to V sth3 time;

[0062] Step 3): The microprocessor captures the feedback output signal tp, and the constant micro-current source injects a constant gate current into the power GaN chip to make the gate voltage change from V sth2 Increase to V sth3 The time Δt is calculated, and the charging time Δt and the voltage change Δu = V sth3 -V sth2 , calculate the gate capacitance C based on the charging current i g_ss .

[0063] In this embodiment, in step 1), the microprocessor input signal sc is at a low level, and the output control signal ccs of the signal operation unit is also at a low level, and the gate voltage v of the GaN power device is gss Less than the preset value V sth1 , the constant micro-current source stops injecting gate current into the power GaN device;

[0064] In step 2), the microprocessor sends an input control signal sc which changes from a low level to a high level. At this time, the constant micro-current source starts to inject gate current into the power GaN device, making the gate voltage v gss Gradually increases, when the signal comparison unit detects the gate voltage v of the power GaN device gss Increase to the reference preset value V sth1When the result is output to the signal operation unit, the signal operation unit performs operation processing on the result output by the signal comparison unit and the input control signal sc of the microprocessor, so that the output control signal ccs of the signal operation unit changes from a high level to a low level, and the constant micro-current source stops injecting gate current into the power gallium nitride device, and then the microprocessor changes the output control signal sc from a high level to a low level;

[0065] In step 3), the time t during which the constant micro-current source injects a constant gate current into the power GaN device is the time during which the input control signal CCS is kept at a high level.

[0066] Below, the monitoring process of simulating the gate capacitance change of the power GaN device with a capacitive load in a micro-current source circuit is as follows:

[0067] Table 1 Circuit Figure 6 Changes of the corresponding signals under the timing diagram shown

[0068]

[0069] In Table 1, 1 indicates that the MOSFET is turned on and 0 indicates that the MOSFET is turned off. CCS is the output state of the signal operation unit, CPO is the output state of the SR latch, TP is the output state of the sampling time, and CP, CP1 and CP2 are the output states of the signal comparison unit. The specific analysis is as follows:

[0070] Before t0, the microprocessor input signal is at a low level. At this time, the signal comparison unit output signals cp, cp1 and cp2 are all at a high level, the SR latch output signal cpo is also at a high level, and the signal operation unit output signal ccs is at a low level. At this time, the current source does not work.

[0071] In the t0-t1 stage, the signal comparison unit output signals cp, cp1 and cp2 and the signal operation unit output signal cpo are high level. At t0, the signal operation unit output signal ccs becomes high level, and the current source starts to work and the gate capacitor injects current. The signal comparison unit output signal cp1 becomes low level at t1. When the gate voltage v gss becomes V sth2 .

[0072] In the stage t1--t2, the output signals cpo and ccs of the signal operation unit and the output signals cp and cp2 of the signal comparison unit are high level, and the sampling time tp is also high level. At this time, the output signal cp1 of the signal comparison unit is low level, and the output signal cp2 of the signal comparison unit becomes low level at t2.

[0073] In the stage t2--t3, the output signals cpo and ccs of the signal operation unit are high, the output signal cp of the signal comparison unit is also high, the output signal cp1 of the signal comparison unit is low, the output signal cp2 of the signal comparison unit becomes low, and the sampling time tp also becomes low. At t3, the gate voltage v gss Reaching the set value V sth1 At this time, the signal comparison unit output signals cp, cp1 and cp2 are also low level, and become high level after the hysteresis time. At this time, the signal operation unit output signal ccs becomes low level.

[0074] In the stage t3-t4, the signal comparison unit outputs high-level signals cp, cp1 and cp2, and the signal operation unit outputs low-level signals ccs, cpo and tp. At t4, the microprocessor input signal sc becomes low-level, and the SR latch output signal cpo is reset to high-level, thus preparing for the next measurement.

[0075] The monitoring method proposed in the present invention is to monitor when the power gallium nitride device is turned off. The monitoring circuit of the present invention has the potential for online monitoring, and the circuit has high integration, the monitoring method is easy to implement, and the reliability assessment of the power gallium nitride device is accurate, thereby improving the reliability of the power gallium nitride device, and has practical application value.

Claims

1. The monitoring circuit of the gate characteristics of the power GaN device is characterized by include: Isolation power supply unit, constant micro-current source, signal comparison unit, signal operation unit; The isolated power supply unit is respectively connected to the constant micro-current source, the signal comparison unit, and the signal operation unit to supply power to these units; The constant micro-current source is connected to the signal comparison unit and the power gallium nitride device respectively, and the constant micro-current source injects a constant gate current into the power gallium nitride device according to the output control signal of the signal comparison unit received; The signal comparison unit is connected to the signal operation unit and the power GaN device respectively, and the signal comparison unit is used to compare the gate voltage v of the power GaN device. gss With the reference preset value V sthi Performing comparison and outputting the comparison result to the signal operation unit; The signal operation unit is connected to the constant micro-current source, the signal comparison unit and the microprocessor respectively. The signal operation unit outputs a control signal to the constant micro-current source according to the received result, and feeds back a monitoring signal to the microprocessor at the same time.

2. The monitoring circuit for gate characteristics of a power gallium nitride device according to claim 1, characterized in that: The signal operation unit receives the output control signal sc of the microprocessor and performs operation processing on the result output by the signal comparison unit to obtain the output control signal ccs, which is then output to the constant micro current source; the signal operation unit processes the result output by the received signal comparison unit to obtain the feedback monitoring signal tp, and then feeds back the signal to the microprocessor; The output end of the constant micro-current source is connected to the power GaN device. When the power GaN device is in the off state, the constant micro-current source injects a constant gate current into the power GaN device when the output control signal CCS is at a high level, thereby monitoring the gate characteristics of the power GaN device. When the output control signal CCS is at a low level, the constant micro-current source stops injecting a constant gate current into the power GaN device.

3. The monitoring circuit for gate characteristics of a power gallium nitride device according to claim 1, characterized in that: The constant micro-current source includes a single-pole double-throw switch, operational amplifiers A1 and A2, resistors R, and resistors R set , capacitor C and N-type MOSFET; The SEL end of the single-pole double-throw switch is connected to the output end of the digital isolator Diso1, the S2 end of the single-pole double-throw switch is connected to a +1.2V voltage, and the S1 end of the single-pole double-throw switch is grounded; the fixed end of the single-pole double-throw switch is connected to the positive input end of the operational amplifier A1; the reverse input end of the operational amplifier A1 is respectively connected to one end of the resistor R and one end of the capacitor C; The other end of the resistor R is connected to the output end of the operational amplifier A2, and the other end of the capacitor C is connected to the resistor R set One end of the amplifier is connected to the positive input terminal of the operational amplifier A2; The resistor R set The other end is connected to the gate of the power GaN device, and the source of the power GaN device is grounded; The output end of the operational amplifier A1 is connected to the positive input end of the operational amplifier A2, the reverse input end of the operational amplifier A2 is connected to the source of the N-type MOSFET, and the drain of the N-type MOSFET is connected to the output -v m The output interface of the voltage value is connected and grounded; the gate of the N-type MOSFET is connected to the signal operation unit output signal ccs through an inverter.

4. The monitoring circuit for gate characteristics of a power gallium nitride device according to claim 1, characterized in that: The signal comparison unit includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, and a hysteresis comparator Comp1; One end of the resistor R1 is used to connect to the gate of the power GaN device, the other end of the resistor R1 is respectively connected to the inverting input end of the hysteresis comparator Comp1 and one end of the resistor R2, and the other end of the resistor R2 is respectively connected to the power isolation unit capable of outputting -v m The output interface of the voltage value is connected to the ground terminal; one end of the resistor R3 is connected to the power isolation unit to output +v cc The output interface of the voltage value is connected, the other end of the resistor R3 is connected to one end of the resistor R5, one end of the resistor R4, and the in-phase input end of the hysteresis comparator Comp1, the other end of the resistor R5 is connected to the output end of the hysteresis comparator Comp1, the other end of the resistor R4 is grounded, and the power pins of the hysteresis comparator Comp1 are respectively connected to the power isolation unit that can output +v cc Output interface connection of voltage value and ground terminal connection; The signal comparison unit includes a resistor R6, a resistor R7, a resistor R8, a resistor R9, a resistor R10, and a hysteresis comparator Comp2; one end of the resistor R6 is used to connect to the gate of the power gallium nitride device, the other end of the resistor R6 is simultaneously connected to the reverse input end of the hysteresis comparator Comp2 and one end of the resistor R7, and the other end of the resistor R7 is respectively connected to the inverting input end of the power isolation unit that can output -v m The output interface of the voltage value is connected to the ground terminal; one end of the resistor R8 is connected to the power isolation unit that can output +v cc The output interface of the voltage value is connected, the other end of the resistor R8 is connected to one end of the resistor R10, one end of the resistor R9 and the in-phase input end of the hysteresis comparator Comp2, the other end of the resistor R10 is connected to the output end of the hysteresis comparator Comp2, the other end of the resistor R9 is grounded, and the power pins of the hysteresis comparator Comp2 are respectively connected to the power isolation unit that can output +v cc Output interface connection of voltage value and ground terminal connection.

5. The monitoring circuit for gate characteristics of a power gallium nitride device according to claim 1, characterized in that: The first part of the signal operation unit includes a NAND gate NaS, a NAND gate NaR, an AND gate AND and a digital isolator Diso1; the NAND gate NaS and the NAND gate NaR constitute an SR latch, one input end of the NAND gate NaS is connected to the microprocessor output control signal Sc, the other input end of the NAND gate NaS is connected to the output end of the NAND gate NaR, one input end of the NAND gate NaR is connected to the output end of the hysteresis comparator Comp1, the other input end of the NAND gate NaR is simultaneously connected to the output end of the NAND gate NaS and one input end of the AND gate AND, the other input end of the AND gate AND is connected to the microprocessor output control signal Sc, the output end of the AND gate AND is connected to the input end of the digital isolator Diso1, and the output end of the digital isolator Diso1 is connected to a constant micro-current source; The second part of the signal operation unit includes a NOT gate, an AND gate AND1, and an AND gate AND2. The input end of the NOT gate is connected to the output end of the hysteresis comparator comp2, the output end of the NOT gate is connected to the input end of the AND gate AND1, the other input end of the AND gate AND1 is connected to the output end of the hysteresis comparator, the output end of the AND gate AND1 is connected to the input end of the AND gate AND2, the other input end of the AND gate AND2 is connected to the signal operation unit AND gate input signal cpo, and the output end of the AND gate AND2 is connected to the feedback monitoring signal tp.

6. A method for monitoring gate characteristics of a power gallium nitride device using a monitoring circuit as claimed in any one of claims 1 to 5, characterized in that: By monitoring the constant micro-current source to power the GaN device gate capacitance C g_ss The charging curve is used to calculate the gate capacitance C of the power GaN device g_ss The change of is used to characterize the reliability of the gate of the power GaN device.

7. The method for monitoring gate characteristics of a power gallium nitride device according to claim 1, characterized in that: When the power GaN device is turned off, the gate voltage v gss Lower than the reference value V sthi ; The gate voltage v of the power GaN device gss With the reference preset value V sth1 The comparison result between them is output to the signal operation unit, wherein the signal operation unit sends a control signal to the constant micro-current source so that the constant micro-current source injects a constant gate current into the power gallium nitride device. At this time, the gate voltage v gss Gradually increases, when the signal comparison unit monitors the gate voltage v of the power GaN device gss Reach the reference preset value V sth1 When the result is output to the signal operation unit, the signal operation unit sends a control signal to the constant micro-current source to stop injecting the constant gate current into the power gallium nitride device; the gate voltage of the power gallium nitride device changes from v gss Increase to the reference preset value V sth1 During this period, it increases to V sth2 、V sth3 When the signal comparison unit outputs the comparison result to the signal operation unit, the signal operation unit processes it to obtain the feedback monitoring signal tp required by the microprocessor, that is, the gate voltage is V sth2 Increase to V sth3 time; The microprocessor captures the feedback monitoring signal tp, and the constant micro-current source injects a constant gate current into the power GaN device to make the gate voltage change from v sth2 Increase to v sth3 The time Δt is calculated, and the charging time Δt and voltage change are calculated, Δu = V sth3 -V sth2 , the gate capacitance C of the power GaN device is characterized by the charging current i g_ss .

8. A method for monitoring the characteristics of a gallium nitride gate, characterized in that The following steps are involved: Step 1): When the power GaN device is turned off, the gate voltage v of the GaN power device is gss Less than the preset value V sthi ; Step 2): The signal comparison unit compares the gate voltage v of the power GaN device in step 1) gss With the reference preset value V sth1 The comparison result is output to the signal operation unit, and the signal operation unit sends a control signal to the constant micro current source, so that the constant micro current source injects a constant gate current into the power GaN device. At this time, the gate voltage v gss Gradually increases, when the signal comparison unit monitors the gate voltage v of the power GaN device gss Increase to the reference preset value V sth1 When the result is output to the signal operation unit, the signal operation unit sends a control signal to the constant micro current source, so that the constant micro current source stops injecting a constant gate current into the power GaN device; the gate voltage of the power GaN device is changed from v gss Increase to the reference preset value V sth1 During the process, it increases to V sth2 and V sth3 When , the signal comparison unit outputs the comparison result to the signal operation unit, and the signal operation unit processes the result to obtain the feedback output signal tp required by the microprocessor; Step 3): The microprocessor captures the feedback output signal tp, and the constant micro-current source injects a constant gate current into the power GaN chip to make the gate voltage change from V sth2 Increase to V sth3 The time Δt is calculated, and the charging time Δt and the voltage change Δu = V sth3 -V sth2 , calculate the gate capacitance C based on the charging current i g_ss .

9. A method for monitoring GaN gate characteristics according to claim 8, characterized in that: In step 1), the microprocessor input signal sc is at a low level, and the output control signal ccs of the signal operation unit is also at a low level. The gate voltage v gss Less than the preset value V sth1 , the constant micro-current source stops injecting gate current into the power GaN device.

10. The method for monitoring GaN gate characteristics according to claim 8, characterized in that: In step 2), the microprocessor sends an input control signal sc which changes from a low level to a high level. At this time, the constant micro-current source starts to inject gate current into the power GaN device, making the gate voltage v gss Gradually increases, when the signal comparison unit detects the gate voltage v of the power GaN device gss Increase to the reference preset value V sth1 When the result is output to the signal operation unit, the signal operation unit operates the result output by the signal comparison unit and the input control signal sc of the microprocessor, so that the output control signal ccs of the signal operation unit changes from a high level to a low level, and the constant micro-current source stops injecting gate current into the power gallium nitride device. Subsequently, the microprocessor changes the output control signal sc from a high level to a low level.

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