Monolithic Power Systems, Inc.

Electronic Lighting, Inc.

John Robert Shannon

James Copland Moyer

Michael Ren Hsing

Hubertus Notohamiprodjo

Jeffrey Michael Dixon

The described DC to AC inverter efficiently controls the amount of electrical power used to drive a cold cathode fluorescent lamp (CCFL). The output is a fairly pure sine wave which is proportional to an input control voltage. The output waveform purity is ensured by driving a symmetrical rectangular waveform into a second-order, low pass filter at the resonant frequency of the filter for all conditions of line voltage and delivered power. Operating stress on the step-up transformer is minimized by placing the load (lamp) directly across the secondary side of the transformer. When configured to regulate delivered power, the secondary side may be fully floated which practically eliminates a thermometer effect on the operation of the lamp. All of the active elements, including the power switches, may be integrated into a monolithic silicon circuit.

Method and apparatus for controlling a discharge lamp in a backlighted display

Apparatus for controlling a discharge lamp in a backlighted display

The present invention is directed to a power supply circuit for controlling a load which, for example, includes both a gas-discharge lamp and an auxiliary load. The power supply circuit includes a ballast circuit for limiting current supplied to the gas discharge lamp. The auxiliary load, such as an occupancy sensor, is connected to receive an alternating current signal from a transformer winding, inductor coil, or other suitable portion of the ballast circuit. The power supply circuit includes a rectifier for rectifying the alternating current signal to provide a stable, low-voltage direct current signal to drive the auxiliary load.

Apparatus for supplying power from a ballast circuit to an auxiliary load

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Daly City, CA, United States of America

John Robert Shannon