CN221528810U - Test circuit for special working condition of SiC MOSFET - Google Patents

Abstract

The utility model provides a test circuit aiming at special working conditions of a SiC MOSFET, which comprises a drive circuit and a soft start circuit, wherein the drive circuit is composed of a circuit controlled by an external signal source, the on time and the threshold voltage amplitude of the SiC MOSFET are controlled by the external signal source, the soft start circuit is composed of a resistor R1 and a capacitor C, and the soft start time of the circuit is controlled by changing the size of the capacitor C. The utility model can accurately control the soft start time of a circuit and the turn-on time of the SiC MOSFET based on the RC control soft start time and the turn-on time of an external signal source control triode, and the mode of resistor voltage division can lead the drive voltage of the SiC MOSFET to follow the bus voltage, thereby meeting the parameter test of different special working conditions and helping device designers to better optimize the device design and product technological parameters.

Description

Test circuit for special working condition of SiC MOSFET

Technical Field

The utility model belongs to the field of semiconductor power device testing, and particularly relates to a testing circuit aiming at special working conditions of a SiC MOSFET.

Background

With the increasing application of SiC MOSFETs to replace Si-based MOSFETs, power device manufacturers are increasingly prominently and urgently testing methods and technical problems brought about by some problems that may occur during use and some parameter limits of SiC MOSFETs to verify the performance of their own products.

The traditional power device adopts a double-pulse test method, so that main parameters in a steady state and dynamic process are obtained, the performance of the device is better estimated, the driving design is optimized, and the like. However, in some application scenarios, the use of the double pulse test results may not be satisfactory for making an assessment of device application under such conditions.

Disclosure of Invention

Aiming at the special working condition of the SiC MOSFET, the utility model provides a novel test circuit which has the characteristics of precisely controllable soft start time and MOSFET on time and adjustable threshold voltage (adjustable along with the bus voltage).

In order to achieve the above purpose, the technical scheme of the utility model is as follows:

The test circuit for special working conditions of the SiC MOSFET comprises a drive circuit and a soft start circuit, wherein the drive circuit consists of a circuit controlled by an external signal source, and realizes the control of the turn-on time and threshold voltage amplitude of the SiC MOSFET through the external signal source, and particularly comprises a load resistor RLOAD, a drain electrode (D) of a SiC MOSFET device Q1, a grid electrode (G) of the SiC MOSFET device Q1, a resistor R1 and a collector electrode of a triode Q2 which are sequentially connected in series, wherein the source electrode (S) of the SiC MOSFET device Q1 is connected with an emitter electrode (E) of the triode Q2, and further comprises a resistor RNC1 connected with the R1 in parallel, and a resistor RNC2 connected with the load resistor RLOAD and the SiC MOSFET device Q1 in parallel; the soft start circuit consists of a resistor R1 and a capacitor C of a drain electrode (D) and a grid electrode (G) of the SiC MOSFET, and the soft start time of the circuit is controlled by changing the size of the capacitor C; the device also comprises a rogowski coil and an oscilloscope which are arranged between the load resistor RLOAD and the drain electrode (D) of the SiC MOSFET device Q1; the drain electrode (D) and the source electrode (S) of the SiC MOSFET device Q1 are respectively connected with an oscilloscope, and a voltage probe is arranged between the oscilloscope and the source electrode (S); the grid electrode (G) of the SiC MOSFET device Q1 and the emitter electrode (E) of the triode Q2 are respectively connected with an oscilloscope, and a voltage probe is arranged between the oscilloscope and the grid electrode (G); the base electrode (B) of the triode Q2 is connected with the emitter electrode (E) to be grounded to the resistor R4, and the base electrode (B) of the triode Q2 is connected with the base resistor R3 to receive a control signal.

Compared with the prior art, the utility model has the beneficial effects that:

The test circuit has the characteristics of soft start time, accurate control of MOSFET (metal oxide semiconductor field effect transistor) on time and adjustable threshold voltage (adjustable along with bus voltage). The soft start time based on RC control and the conduction time of the external signal source control triode can accurately control the soft start time of a circuit, the turn-on time of the SiC MOSFET can be accurately controlled, and the driving voltage of the SiC MOSFET can follow the bus voltage through a resistor voltage division mode.

Compared with the traditional double-pulse testing method, the testing circuit can meet the SiC MOSFET parameter tests under different special working conditions besides meeting the steady-state and dynamic SiC MOSFET part parameter tests. The device design and the product process parameters can be better optimized by device designers, so that a more stable and reliable product can be obtained, and the practical application of different customers under different working conditions can be satisfied.

Drawings

Fig. 1 is a circuit diagram of a SiC MOSFET test of the present utility model.

FIG. 2 is a special operating condition demand graph.

Fig. 3 is a diagram of an example test waveform.

Detailed Description

The present utility model will be described in further detail with reference to specific examples, but embodiments of the present utility model include, but are not limited to, the scope of the following examples.

Referring to fig. 1, the utility model provides a SiC MOSFET test circuit, especially for testing under certain special conditions. Comprises a driving circuit and a soft start circuit. The driving circuit mainly comprises triodes Q2 and R1 controlled by an external signal source, RNC1 and RNC 2; the soft start circuit mainly comprises R1 and C.

The specific connection mode of the test circuit is as follows.

As shown in fig. 1, the utility model discloses a test circuit aiming at special working conditions of a SiC MOSFET, which comprises a drive circuit and a soft start circuit, wherein the drive circuit consists of a circuit controlled by an external signal source, and realizes the control of the turn-on time and threshold voltage amplitude of the SiC MOSFET through the external signal source, and specifically comprises a load resistor RLOAD, a drain electrode (D) of a SiC MOSFET device Q1, a grid electrode (G) of the SiC MOSFET device Q1, a resistor R1 and a collector electrode of a triode Q2 which are sequentially connected in series, and a source electrode (S) of the SiC MOSFET device Q1 is connected with an emitter electrode (E) of the triode Q2, and further comprises a resistor RNC1 connected in parallel with the R1 and a resistor RNC2 connected in parallel with the load resistor RLOAD and the SiC MOSFET device Q1; the soft start circuit comprises a capacitor C connected in parallel with a drain electrode (D) and a grid electrode (G) of the SiC MOSFET, and the soft start time of the circuit is controlled by changing the size of the capacitor C; the device also comprises a rogowski coil and an oscilloscope which are arranged between the load resistor RLOAD and the drain electrode (D) of the SiC MOSFET device Q1; the drain electrode (D) and the source electrode (S) of the SiC MOSFET device Q1 are respectively connected with an oscilloscope, and a voltage probe is arranged between the oscilloscope and the source electrode (S); the grid electrode (G) of the SiC MOSFET device Q1 and the emitter electrode (E) of the triode Q2 are respectively connected with an oscilloscope, and a voltage probe is arranged between the oscilloscope and the grid electrode (G); the base electrode (B) of the triode Q2 is connected with the emitter electrode (E) to be grounded to the resistor R4, and the base electrode (B) of the triode Q2 is connected with the base resistor R3 to receive a control signal. The soft start time is determined by the capacity of the capacitor C and the resistance value of the resistor R1 in FIG. 1; the MOSFET on time is controlled by an external signal source through controlling the switching time of Q2 in the circuit of figure 1; the threshold voltage follows the bus fluctuation and is controlled by the dotted line part of fig. 1 and Q2 controlled by an external signal source.

In order to test the parameter limit of the device of the SiC MOSFET under the special working condition, the load (Rload in figure 1) value is set to simulate the carrying capacity of the SiC MOSFET under the actual working condition, the external signal source is used for carrying out the same driving time or the external signal source is turned on, the resistance values of the broken line parts RNC1, RNC2 and R1 in figure 1 are set to enable the G pole driving voltage of the SiC MOSFET to synchronously fluctuate along with the bus voltage, the working state of the SiC MOSFET under the actual special working condition is simulated, the working state of the SiC MOSFET at the moment is monitored through the voltage probe 1, the voltage probe 2 and the Roche coil, the working condition of the SiC MOSFET under the working condition is tested, and the performance of the SiC MOSFET is evaluated.

Referring to fig. 1, the control logic of the driving circuit is: when the driving voltage is required to follow the fluctuation of the bus, firstly, when a special working condition is simulated, according to the actual calculated resistance values of R1, RNC1 and RNC2, RLOAD is set, then triode Q2 is opened, VIN is finally accessed, and corresponding parameters of the SiC MOSFET under the working condition are obtained through monitoring of voltage and current signals on the tested SiC MOSFET by the voltage probe 1, the voltage probe 2 and the Roche coil. When the driving voltage is not required to follow the fluctuation of the bus, and only the on time of the MOSFET is required to be accurately controlled, the RNC1 and the RNC2 do not need to be connected into a circuit, and the on time of the MOSFET is set through an external signal source.

Referring to fig. 1, the circuit soft start time is set by the magnitude of the values of R1, C. Charging time = capacitance capacity, resistance, i.e.:

t=R*C

As can be seen from the formula, if the soft start time needs to be set, only the corresponding RC parameter needs to be determined.

Referring to fig. 1, the soft start principle of the test circuit according to the present utility model is as follows:

1. When the input signal for controlling the external signal source is low level or high resistance, the base electrode of the triode Q2 is pulled down to the ground, the triode Q2 is not conducted, and then vgs=0 of the MOS transistor Q1 is not conducted. The ground resistor R4 is to fix the base of the transistor Q2 at a low level when the signal is high, and to prevent floating.

2. When the power VIN is just powered on, the input signal of the external signal source is required to be low level or high resistance, i.e. the transistor Q2 is turned off, so that the MOS transistor Q1 is turned off. Since VIN is not stable yet, siC MOSFETs cannot be turned on.

3. After the power supply VIN is powered on, both ends of the G pole and the S pole of the MOS transistor are VIN, and vgs=0.

4. At this time, if signal is set to high level (assuming that high level is 3.3V), then:

① The base of the triode Q2 is 0.7V, and the base current Ibe can be calculated as:

(3.3V-0.7V)/base resistance r3=0.26 mA

② The transistor Q2 is saturated and conducting, vce.apprxeq.0. The capacitor C1 is charged through the resistor R1, that is, the voltage at the connection terminal of the C1 and the G pole is slowly reduced from VIN to 0V, resulting in a gradual increase of Vgs voltage.

③ Vgs of the MOS transistor Q1 increases slowly, and opens slowly until it opens completely.

④ The slow opening (conduction) of the MOS tube Q1 is realized by using the charging time of the capacitor C1, and the soft start function is realized.

Examples

The circuit in fig. 1 is adopted for checking the practical application limit of a certain type of SiC MOSFET under the working condition by applying the circuit in a practical special requirement and requiring the driving voltage to follow the fluctuation of a bus (shown in fig. 2).

Test waveforms as shown in fig. 3, the circuit can test the application limit of the SiC MOSFET under the special working condition from the final test waveform. The use of the circuit of FIG. 1 to meet certain specific test conditions can help research and development personnel evaluate the limit of use parameters of the device under the corresponding conditions.

Claims (4)

1. A test circuit aiming at special working conditions of a SiC MOSFET is characterized in that:

the driving circuit consists of a circuit controlled by an external signal source, and realizes the control of the turn-on time and threshold voltage amplitude of a SiC MOSFET through the external signal source, and specifically comprises a load resistor RLOAD, a drain electrode of the SiC MOSFET device Q1, a grid electrode of the SiC MOSFET device Q1, a resistor R1 and a collector electrode of a triode Q2 which are sequentially connected in series, wherein the source electrode of the SiC MOSFET device Q1 is connected with the emitter electrode of the triode Q2, and the driving circuit further comprises a resistor RNC1 connected with the resistor R1 in parallel and a resistor RNC2 connected with the load resistor RLOAD and the SiC MOSFET device Q1 in parallel;

The soft start circuit consists of a resistor R1 of a drain electrode and a grid electrode of the SiC MOSFET and a capacitor C, and the soft start time of the circuit is controlled by changing the size of the capacitor C; the base electrode and the emitter electrode of the triode Q2 are connected with the grounding resistor R4, and the base electrode of the triode Q2 is connected with the base resistor R3 to receive control signals.

2. The test circuit for special operating conditions of a SiC MOSFET of claim 1, wherein:

The soft start circuit also includes a rogowski coil and an oscilloscope disposed between the load resistor RLOAD and the drain of the SiC MOSFET device Q1.

3. A test circuit for special operating conditions of a SiC MOSFET according to claim 2, wherein:

The soft start circuit further comprises a drain electrode and a source electrode of the SiC MOSFET device Q1 which are respectively connected with an oscilloscope, and a voltage probe is arranged between the oscilloscope and the source electrode.

4. A test circuit for special conditions of a SiC MOSFET according to claim 3, wherein:

The soft start circuit further comprises a grid electrode of the SiC MOSFET device Q1 and an emitter electrode of the triode Q2 which are respectively connected with an oscilloscope, and a voltage probe is arranged between the oscilloscope and the grid electrode.