Abstract: A solid state power switching circuit for alternating current loads, in which operating power for the circuit is diverted from the switched current during power stealing intervals self-synchronized with the alternating current waveform. During periods in which current to the load is commanded, a load current switch is maintained in a low impedance state except for the duration of a short power stealing interval each half-cycle of the supplied alternating current. Self-synchronization is achieved with a current detector which senses whether or not the magnitude of the current diverted during each power stealing interval exceeds a current threshold, and pulse generator logic which shifts the power stealing intervals in time relative to the alternating current waveform in response to the previously sensed current magnitude.

Abstract: In the present invention, fault containment module signals are assigned to the pins so that a band of guard pins connected to ground exists between the signal pins belonging to each fault containment module. Thus, a bent pin or foreign contaminant can only cause a short to ground or to another pin assigned to the same fault containment module, thereby diminishing the chance that bent pins and foreign contaminants will cause interference between the signals from different fault containment modules.