This document describes the application of zero voltage crossing optically isolated triac drivers in interface applications. These drivers are low-cost, simple and effective solutions for interfacing between low current DC control circuits such as logic gates and microprocessors and AC power loads (120, 240 or 380 volt, single or 3-phase). They provide sufficient gate trigger current for high current, high voltage thyristors, while providing a guaranteed 7.5 kV dielectric withstand voltage between the line and the control circuitry. An integrated, zero-crossing switch on the detector chip eliminates current surges and the resulting electromagnetic interference (EMI) and reliability problems for many applications. The high transient immunity of 5000 V/µs, combined with the features of low coupling capacitance, high isolation resistance and up to 800 volt specified V DRM ratings qualify this triac driver family as the ideal link between sensitive control circuitry and the AC power system environment. Optically isolated triac drivers are not intended for stand-alone service as are such devices as solid state relays. However, they will replace costly and space demanding discrete drive circuitry having high component count consisting of standard transistor optoisolators, support components including a full wave rectifier bridge, discrete transistor, trigger SCRs and various resistors and...
