Patent ID: 7307645

Claim:
A control circuit to vary the intensity of an electro luminescent display, said circuit being connected between a power source and a display, said circuit comprising a pair of conductors to be connected to said display for applying a voltage thereto, an inductor connected to said power source, a switch to control selectively energize said inductor, a gating circuit to selectively connect one or the other of said conductors to said inductor, and a controller operating upon said switch to vary the duty cycle of said switch to thereby vary energy stored in said inductor and operating upon said gating circuit to alternate periodically the relative polarity of said conductors, wherein said gating circuit includes a selectively operable switch for each conductor providing a discharge path for a respective one of said conductors, each said discharge path including a current limiting element in series with a respective switch between said conductor and said switch; and said inductor energizes said conductors through said gating circuit according to operation of said controller.