Use ADuM4136 isolated gate driver and LT3999 DC/DC converter to drive 1200 V SiC power module

The success of Power development technologies such as electric vehicles, renewable energy and energy storage systems depends on the effective implementation of power conversion schemes. The core of power Electronic converters includes dedicated semiconductor devices and strategies to control the on and off of these new semiconductor devices through gate drivers.

Authors: Juan Carlos Rodriguez and Martin Murnane, Analog Devices

Introduction

The success of power development technologies such as electric vehicles, renewable energy and energy storage systems depends on the effective implementation of power conversion schemes. The core of power electronic converters includes dedicated semiconductor devices and strategies to control the on and off of these new semiconductor devices through gate drivers.

The most advanced broadband devices, such as silicon carbide (SiC) and gallium nitride (GaN) semiconductors, have higher performance, such as high voltage ratings of 600 V to 2000 V, low channel impedance, and fast switching up to the MHz range speed. These increase the performance requirements of the gate driver, for example, through desaturation to get shorter transmission delay and improved short-circuit protection.

This application note demonstrates the advantages of the ADuM4136 gate driver. This single-channel device has an output drive capability of up to 4 A, a maximum common-mode transient immunity (CMTI) of 150 kV/μs, and a fast speed including desaturation protection. Fault management function.

Developed in collaboration with Stercom Power Solutions GmbH, the gate drive unit (GDU) for SiC power devices demonstrates the performance of ADuM4136 (see Figure 1). The circuit board is powered by a bipolar isolated power supply, which is based on a push-pull converter constructed using the LT3999 power driver.This monolithic high-voltage, high-frequency, DC/DC conversion driver includes a 1 A dual switch with a programmable current limit function, provides a synchronization frequency of up to 1 MHz, has a wide operating range from 2.7 V to 36 V, and a shutdown current

Use ADuM4136 isolated gate driver and LT3999 DC/DC converter to drive 1200 V SiC power module
Figure 1. GDU

Test setup

The complete setup for the report test is shown in Figure 2. Provide high-voltage DC input power (V1) at both ends of the power module. Add a 1.2 mF, decoupling foil capacitor bank (C1) at the input. The output stage is a 38 μH Inductor (L1), which can be connected to the high-side or low-side of the power module during the desaturation protection test. Table 1 summarizes the test setup power devices.

Use ADuM4136 isolated gate driver and LT3999 DC/DC converter to drive 1200 V SiC power module
Figure 2. Schematic diagram of test setup

Table 1. Test setup power device

Device

value

V1

0 V to 1000 V

C1

1.2 mF

SiC power module (FF23MR12W1M1_B11)

1200 V, 23 mΩ

L1

38 μH

The GDU shown in Figure 4 receives the switching signal from the pulse wave generator. These signals are sent to the dead time generating circuit, which is implemented by the LT1720 ultra-fast, dual-channel comparator, and the output of the comparator is fed into two ADuM4136 devices. The ADuM4136 gate driver sends an isolation signal to the gate terminal and receives the isolation signal from the drain terminal of the two SiC MOSFETs in the power module. The output stage of the gate driver is provided with isolated power by a push-pull converter, which uses an LT3999 DC/DC driver powered by an external 5 V DC power supply. The temperature measurement of the SiC module uses the ADuM4190 high-precision isolation amplifier. The ADuM4190 is powered by the LT3080 low dropout (LDO) linear regulator.

Figure 3 shows the experimental connection setup, and Table 2 describes the equipment used in the desaturation protection test.

Table 2. Test setup equipment

equipment

Manufacturers

Product number

Oscilloscope

Rohde & Schwarz

HMO3004, 500 MHz

DC power supply

Komerci

QJE3005EIII

Gate drive unit (GDU)

Stercom

SC18025.1

Pulse wave generator

IB Billmann

PMG02A

Digital Multimeter (DMM)

FLUKE

Fluke 175

High voltage differential probe

Testec

TT-SI 9010

AC Rogowski current probe

PEM

CWT mini

Use ADuM4136 isolated gate driver and LT3999 DC/DC converter to drive 1200 V SiC power module
Figure 3. Connection diagram of test equipment

Test Results

Dead time and transmission delay

The hardware dead time is introduced by the GDU to avoid short circuits in the half-bridge power module, which may occur when the high-side and low-side SiC MOSFETs are turned on or off (see Figure 4). Please note that the delayed signal is represented in this article as.

In the transmission delay test, the dead time is measured on the signal chain of the bottom driver, which is excited by the (effective low level) input of the GDU signal. The dead time is generated by using a resistive capacitor (RC) filter and the LT1720 ultra-fast comparator. Figures 5 to 8 show the results of the transmission delay test. Table 3 describes the signals shown in Figures 5 to 8.

Table 3. Oscilloscope signal description (low-end driver)

symbol

Signal function

Channel number

VGS_B

MOSFET gate

2

After the comparator

3

GDU input

4

When the input signal is pulled low, the comparator changes its delayed output state from high to low, and the dead time is determined by the RC circuit (~160 ns, see Figure 5).

When the SiC MOSFET is turned off and the input signal is pulled high, the delay time is negligible (~20 ns) compared with the delay time measured when the SiC MOSFET is turned on, as shown in Figure 6.

Figure 7 and Figure 8 show the delay time measured after the dead time is generated and the VGS_B signal is switched during turn-on and turn-off. These delay times are relatively short, 66 ns and 68 ns, respectively, by ADuM4136. The delay introduced.

The total transmission delay time (dead time plus transmission delay) at turn-on is approximately 226 ns, and the total transmission delay time at turn-off is approximately 90 ns. Table 4 summarizes the results of the transmission delay time.

Use ADuM4136 isolated gate driver and LT3999 DC/DC converter to drive 1200 V SiC power module
Figure 4. GDU signal chain

Table 4. Propagation delay test results

event

Switching signal, high-low

Switch signal, low-high

Dead time (ns)

Driver delay time (ns)

Total transmission delay time (ns)

Device on

Gate signal

160

66

226

Device shutdown

Gate signal

twenty two

68

90

Use ADuM4136 isolated gate driver and LT3999 DC/DC converter to drive 1200 V SiC power module
Figure 5. Dead time measurement, device on

Use ADuM4136 isolated gate driver and LT3999 DC/DC converter to drive 1200 V SiC power module
Figure 6. Dead time measurement, device shut down

Use ADuM4136 isolated gate driver and LT3999 DC/DC converter to drive 1200 V SiC power module
Figure 7. Delay time measurement with the device turned on

Use ADuM4136 isolated gate driver and LT3999 DC/DC converter to drive 1200 V SiC power module
Figure 8. Delay time measurement, device shutdown

Desaturation protection

The desaturation protection function to avoid high voltage short circuit of the drive switch is integrated on the ADuM4136 IC.

In this application, each gate driver indirectly monitors the voltage from the drain to source pin of the MOSFET (VDS), check and confirm the voltage of its DESAT pin (VDESAT) Does not exceed the reference desaturation voltage level VDESAT_REF (VDESAT_REF = 9.2 V, typical value) between 8.66 V and 9.57 V. In addition, VDESATThe value of depends on the MOSFET operation and external circuitry: two high-voltage protection diodes and one Zener diode (see Table 6 and the schematic section).

VDESATThe value of can be calculated by the following equation:

VDESAT = VZ + 2 ×VDIODE_DROP + VDS

in:

VZIs the breakdown voltage of the Zener diode.

VDIODE_DROPIs the forward voltage drop of each protection diode.

During the shutdown period, the DESAT pin is pulled low internally, and no saturation event has occurred. In addition, the MOSFET voltage (VMOSFET) Is high, and the two diodes are reverse biased to protect the DESAT pin.

During the turn-on period, the DESAT pin is released after an internal blanking time of 300 ns, the two protection diodes are forward biased, and the Zener diode fails. Here, VDESATWhether the voltage exceeds the VDESAT_REF value depends on VDSValue.

In normal operation, VDSAnd VDESATThe voltage has been very low. When high current flows through the MOSFET, VDSThe voltage increases, resulting in VDESATThe voltage level rises above VDESAT_REF.

In this case, the ADuM4136 gate driver output pin (VOUT) Become a low level within 200 ns and desaturate the MOSFET, and at the same time generate the value of the delay DS, and can be selected to have a breakdown voltage VZThe appropriate Zener diode is set to any level. Conversely, according to the VDSTo estimate the MOSFET current used for desaturation (ID).

The high-side and low-side MOSFETs were subjected to two desaturation protection tests with gate pulses. By choosing different Zener diodes, different fault currents were tested in each test. The measured current value is shown in Table 4, assuming that the maximum VDESAT_REF = 9.57 V (maximum), the nominal VDIODE_DROP = 0.6 V.

Low-side testing

The low-side desaturation protection test was performed by changing the input voltage (V1) from 100 V to 800 V at room temperature of 25°C (see Figure 9).

Use ADuM4136 isolated gate driver and LT3999 DC/DC converter to drive 1200 V SiC power module
Figure 9. Low-side desaturation protection test

Figure 10 to Figure 17 show the results of the low-side desaturation protection test. Table 5 illustrates the signals shown in Figures 10-17.

Table 5. Oscilloscope signal description (low-side test)

Channel number

Signal name

1

FAULT

2

VDS

3

ID

4

VGS

In Figure 16 and Figure 17, the desaturation protection is triggered for a current of ~125 A at 25°C, and the fault state pin is triggered low after a delay of about 1.34 µs.

A similar test was performed on the high side of the power module, where the desaturation protection was triggered to a current of ~160 A at 25°C, and the fault state pin was triggered to be low after 1.32 µs.

The low-side and high-side test results show that the gate drive solution can be used in

test

Zener breakdown voltage, VZ (V)

Detection voltage level, VDS (V)

Detection current level, ID , 25°C (A)

Detection current level, ID , 125°C (A)

Low side

5.1

3.27

116

95

High side

4.3

4.07

140

110

Use ADuM4136 isolated gate driver and LT3999 DC/DC converter to drive 1200 V SiC power module
Figure 10. Low-side test, V1 = 100 V, no fault

Use ADuM4136 isolated gate driver and LT3999 DC/DC converter to drive 1200 V SiC power module
Figure 11. Low-side test, V1 = 200 V, no fault

Use ADuM4136 isolated gate driver and LT3999 DC/DC converter to drive 1200 V SiC power module
Figure 12. Low-side test, V1 = 300 V, no fault

Use ADuM4136 isolated gate driver and LT3999 DC/DC converter to drive 1200 V SiC power module
Figure 13. Low-side test, V1 = 400 V, no fault

Use ADuM4136 isolated gate driver and LT3999 DC/DC converter to drive 1200 V SiC power module
Figure 14. Low-side test, V1 = 500 V, no fault
Use ADuM4136 isolated gate driver and LT3999 DC/DC converter to drive 1200 V SiC power module
Figure 15. Low-side test, V1 = 600 V, no fault
Use ADuM4136 isolated gate driver and LT3999 DC/DC converter to drive 1200 V SiC power module
Figure 16. Low-side test, V1 = 800 V, fault detected

Use ADuM4136 isolated gate driver and LT3999 DC/DC converter to drive 1200 V SiC power module
Figure 17. Low-side test, V1 = 800 V, fault detected (zoom in)

Schematic
Figure 18 to Figure 20 show the principle of the ADuM4136 gate driver board

Use ADuM4136 isolated gate driver and LT3999 DC/DC converter to drive 1200 V SiC power module
Figure 18. Schematic diagram of ADuM4136 gate driver board (primary side)

Use ADuM4136 isolated gate driver and LT3999 DC/DC converter to drive 1200 V SiC power module
Figure 19. Schematic diagram of ADuM4136 gate driver board (isolated power supply and high-side gate signal)

Use ADuM4136 isolated gate driver and LT3999 DC/DC converter to drive 1200 V SiC power module
Figure 20. Schematic diagram of ADuM4136 gate driver board (isolated power supply and low-side gate signal)

in conclusion

The ADuM4136 gate driver can report short propagation delay and fast overcurrent faults through desaturation protection. These advantages, combined with appropriate external circuit design, can meet the stringent requirements of applications using advanced wide-bandgap semiconductor devices such as SiC and GaN.

The test results in this application note are the data of the full gate drive solution driving the SiC MOSFET module at high voltage, and provide ultra-fast response and corresponding fault management through the desaturation protection function. This gate drive solution is powered by a compact, low-noise power converter constructed by LT3999, which provides an isolated power supply with an appropriate voltage level as well as low shutdown current and soft-start functions.

The Links:   LB104S01-TL01 APT2X101D100J