Electric lamp and discharge devices: systems – Current and/or voltage regulation – Automatic regulation
Patent
1998-03-13
1999-07-13
Shingleton, Michael B
Electric lamp and discharge devices: systems
Current and/or voltage regulation
Automatic regulation
315219, 315224, 315DIG5, H05B 3702
Patent
active
059231297
ABSTRACT:
A power conversion circuit drives a cold cathode fluorescent lamp (CCFL) while requiring minimal number of external components. The circuit includes a controller, a direct drive network responsive to control inputs from the controller and coupled to receive a power signal, and a secondary network coupled to the CCFL. The direct drive network is low Q circuit comprising a plurality of switching transistors and a primary winding of a transformer such that an impedance of the direct drive network consists essentially of an inductance of the primary winding and capacitance of the direct drive network consists essentially of parasitic capacitance reflected from the secondary winding. The Q of the direct drive network is less than about 0.5 so that a square wave voltage signal is provided across the primary winding of the transformer. However, the inductance of the transformer is sufficiently high such that the voltage across a secondary winding of the transformer is sinusoidal. The secondary network comprises the secondary winding of the transformer coupled to the CCFL through a connector to provide a sinusoidal current to the CCFL. The controller controls the current passing through the CCFL by pulse width modulating the control inputs to the direct drive network.
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Linfinity Microelectronics
Shingleton Michael B
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