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Optoelectronics/Displays  

Isolated gate drivers offer IGBT protection

Posted: 28 Jul 2010     Print Version  Bookmark and Share

Keywords:optocoupler  gate driver  power inverter 

IGBT gate drivers

Offering features like built-in Miller clamp, rail-to-rail output voltage, under-voltage lockout (UVLO) circuitry and protection against IGBT cross-conduction and current "shoot-through", Avago Technologies reveals the 2.5A peak-output drive ACPL-H342 and ACPL-K342 optically isolated IGBT gate drivers that target safe and efficient power inverter and motor control applications.

A Miller clamp allows the control of the Miller current during high dV/dt output transition. It can also eliminate the need for a negative power supply to ensure safe IGBT turn off by quickly discharging the IGBT's large gate capacitance to a low level without affecting the IGBT turn-off characteristics.

In addition, Avago's new gate drive optocouplers feature a common-mode transient immunity of 40kV/µs at a 1.5kV common mode voltage for reliable operation in noisy environments.

The UVLO function causes the output to be clamped whenever there is insufficient power supply voltage for safe operation. The under-voltage lockout protection circuitry ensures that there is sufficient gate drive voltage to switch the IGBTs completely on, therefore minimising IGBT power dissipation. Once the supply voltage exceeds the positive-going UVLO threshold, the UVLO clamp is released, allowing the device output to turn on in response to an input signal.

Their rail-to-rail output voltage swing and the low output dead time, made possible by low propagation time, minimise driver dissipation and increase efficiency.

Propagation delay is specified to prevent cross conduction of the IGBTs in the high- and low-side half-bridge IGBT configuration that is commonly used in power inverters. Propagation delay difference (tphl—tplh) between two devices is -10ns minimum to -200ns maximum. Hence, shoot through is prevented, thus eliminating a major condition that can cause IGBT damage and shorten operating life.

Other features of the ACPL-H342 and ACPL-K342 gate drivers include high peak output drive current of 2A min, 2.5A max and 15 to 30V supply voltage operation with rail-to-rail output drive.

The maximum working insulation voltage per IEC/EN/DIN EN 60747-5-5 for ACPL-H342-x60 is 891V peak; for ACPL-K342-x60 is 1140V peak. The momentary withstand voltage per UL 1577 for ACPL-H342 is 3750Vrms for 1 minute; for ACPL-K342 is 5000Vrms for 1 minute.

Devices are available in RoHS compliant, 8-lead stretched SO-8 packages that are 40 per cent smaller than conventional 8-pin DIP packages. All devices operate over a very wide temperature range of -40 to +105° C.

Avago's ACPL-H342-000E is priced at Rs.67.71 ($ 1.45) each in 10,000 piece quantities and the ACPL-K342-000E is priced at Rs.74.72 ($1.60) each in 10,000 pieces.





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