Frequency shift inverter for variable power control

摘要

A variable frequency AC power source drives a gas discharge lamp which is connected in parallel with the capacitance of a series resonant circuit. The polarity of the voltage applied to the resonant circuit is commutated at such times as the rate-of-change of current flow in the resonant circuit is below an adjustable threshold value. The setting of a threshold adjusting circuit determines the brightness of the lamp. The polarity is also commutated at such times as the current flow from the source reaches a predetermined level. Lamp current is thus independently and variably controlled in the variable power mode.