High speed optocoupler has integrated IGBT protection circuit
MSC now offers the new PS9402 optocoupler from Renesas Electronics. The PS9402 comprises a gallium-aluminum-arsenide (GaAlAs) LED, a photo detector IC and an IGBT protection circuit. It is said to enable particularly space and cost-saving designs of inverters for motor control, and solar power generation systems.

The new PS9402 optocoupler enables IGBT direct drive up to the 1,200 V and 100 A, and features high speed switching of 200ns maximum. The highly integrated PS9402 is provided in a 16-pin SSOP (Shrink Small Outline Package).

When a fault (short circuit) occurs, the PS9402 has an integrated function that detects the rise in collector-emitter voltage and turns off the IGBT. It also incorporates a soft turn-off function that suppresses the generation of noise when the IGBT is turned off.

Furthermore, a fault signal is output to the MCU to indicate that an abnormal shut-off has occurred. An auto-reset function performs recovery automatically once a specified time of 5µs minimum has elapsed after the fault was detected.

When the IGBT connected to the optocoupler turns off, current flow to the collector-gate capacitance (so-called Miller current) can generate a gate voltage that causes a malfunction. The active Miller clamp circuit built into the PS9402 absorbs the Miller current, averting malfunctions by preventing the gate voltage from rising.

Renesas Electronics’ special BiCMOS process is employed for the light receiving IC. Compared to conventional standard processes, this results in reduced parasitic capacitance, shorter delay time (tPHL and tPLH <= 200ns), and reduced circuit drive current consumption (ICC ≤ 3 mA).

These measures are claimed to contribute to an increase in the precision of the inverter control circuit and at the same time reduced power consumption. They also enable greater system compactness because keeping circuit current levels low means a smaller power supply is required for the system driven by the IGBTs.