US Patent 7307645 Dimmer function for EL displays

A control circuit to vary the intensity of an electro luminescent display. The circuit is connected between a power source and a display and comprises a pair of conductors to be connected to the display for applying a voltage from a voltage generator. A switch controls application of the voltage from the generator to the conductors. A gating circuit connects selectively one or other of the conductors to the voltage source. A controller operates upon the switch to vary the duty cycle and upon the gating circuit to alternate periodically the relative polarity of the conductors. The voltage source includes an inductor and the switch controls current flow through said inductor.