Renesas Electronics has introduced the PS9402 optocoupler that features an integrated IGBT (insulated gate bipolar transistor) protection function. The optocoupler comprises a GaAlAs LED as the light emitting element, a photodetector IC, and an IGBT protection circuit. The company claims that the use of the optocoupler facilitates the design of IGBT peripheral circuits and enables IGBT direct drive up to the 1,200 and 100A class. The optocoupler is housed in a 16pin small outline package and isolates the input and output sides electrically by using light for signal transfer. It is designed for use with IGBTs or MOSFETs to electrically isolate the two circuit blocks. An IGBT drive coupler is used for the drive control of an IGBT, but a protection circuit is also needed to safeguard the IGBT. When the IGBT connected to the optocoupler turns off, current flow to the collector-gate capacitance can generate a gate voltage that can cause a malfunction. The active Miller clamp circuit built into the optocoupler absorbs the Miller current, and averts malfunctions by preventing the gate voltage from rising. The company's BiCMOS process is employed for the light receiving IC that results in reduced parasitic capacitance, short delay time, and reduced circuit drive current consumption.
