Asymmetrical AC trigger simulation

摘要

The present invention teaches a dimmer which incorporates an alternating current (AC) trigger which exhibits asymmetrical electrical characteristics. This eliminates the undesirable snap on hysteresis effect associated with conventional dimmers utilizing symmetrical AC triggers such as diacs and silicon bilateral switches (SBS). One embodiment of the present invention utilizes a zener diode to create the asymmetry. During one polarity of the AC source, the breakover voltage of the trigger is increased, forcing the trigger to breakover at a time later in the AC cycle than it would otherwise have with a symmetric trigger. This compensates for charge dumping of the phase control capacitor into the gate of the triac which would otherwise cause the snap on hysteresis effect.