On design of polarized solid-state relays with electromagnetic coupling

The authors describe an approach to the design of bipolar solid-state relays with electromagnetic coupling. The relay includes a RL-multivibrator with a nonlinear transformer, a duty-cycle detector and an output stage. The input DC current applied to the transformer primary results in a magnetic field which modifies the core saturation condition. The multivibrator oscillation duty cycle changes. This is detected by the duty cycle detector where the polarity of the output voltage changes with the input DC current polarity. The output stages represent the circuits designed to correspond to required relay characteristics