National Semiconductor Corporation

Jeffrey Doyle Mullin

Yan Yin

A circuit for EL panel DC offset correction is provided. The circuit includes components such as an EL panel driver, an error circuit, a pulse width modulation circuit, and a low-pass filter. The low-pass filter performs low-pass filtering on the voltage across the EL panel to provide a low-pass filter output signal. Further, the error circuit receives the low-pass filter output signal and a reference signal, and provides an error signal. The DC bias across the EL panel is adjusted based, at least in part, on the error signal. In this way, DC offset correction is provided based on the negative feedback.

DC offset correction for an electroluminescent panel

A driver circuit for an electroluminescent (EL) lamp that consumes less power and reduces electromagnetic interference (EMI). Electrical charge is stored during a discharge cycle of an AC signal employed to illuminate an EL lamp, and subsequently reused during the AC signal's charging cycle. The reuse of electrical charge enables the driver circuitry to illuminate the EL lamp while drawing the least amount of power from a power supply, such as a battery. Also, multiple charge pumps can be sequentially/serially turned off during the discharge cycles of the AC signal driving the EL Lamp. By sequentially discharging the EL lamp, a waveform for the AC signal can be synthesized that more closely resembles a relatively symmetrical sinusoidal shape. The relatively symmetrical shape of the synthesized AC waveform serves at least in part to reduce spurious emissions of electromagnetic interference (EMI), audio noise, and improve the efficiency of the driver circuitry.

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Wellington, CO, United States of America

Jeffrey Doyle Mullin