BI-POLAR TRIAC SHORT DETECTION AND SAFETY CIRCUIT

摘要

A safety circuit to disrupt power to a heating element of an appliance to be powered through a solid state switch (Tri-ac Q1), typically a triac, from an AC power source (V1) having a positive half cycle and a negative half cycle delivering power. A low resistance condition is sensed by detecting either the current through or voltage across the solid state switch during the positive half cycle and the negative half cycle of the AC power line, when the solid state AC switch is not actuated. A fault signal is generated to interrupt power to the heating element, preferably by a crowbar circuit opening a fuse, whenever the low resistance condition is detected.

主权项

1. A safety circuit for use in disrupting power to a heating element of an appliance to be powered through a solid state switch from an AC power source having a positive half cycle and a negative half cycle delivering power, including detection circuitry for detecting a low resistance condition in said solid state switch during the positive half cycle of the AC power through said solid state switch and detecting a low resistance condition in said solid state switch during the negative half cycle of the AC power through said solid state switch to generate a fault signal to interrupt power to said heating element whenever said low resistance condition is detected while said solid state switch is not activated.