| US 7,545,369 B1 | ||
| Methods and apparatus to improve efficiency in cold cathode fluorescent light controllers | ||
| Rayleigh Lan, Taipei Hsien (Taiwan); and Calum MacRae, San Francisco, Calif. (US) | ||
| Assigned to Maxim Integrated Products, Inc., Sunnyvale, Calif. (US) | ||
| Filed on May 11, 2006, as Appl. No. 11/433,189. | ||
| Int. Cl. G09G 5/00 (2006.01) | ||
| U.S. Cl. 345—204 [345/211; 345/212; 345/66; 345/92; 315/209 R; 315/224; 315/225; 315/291] | 11 Claims |
| 1. A method of operating a resonant full bridge cold cathode fluorescent light (CCFL) controller controlling first through
fourth transistors controlling current through a series connection of a capacitor and a primary of a transformer, the series
connection having first and second leads coupled to a connection between the first and second transistors and coupled to a
connection between the third and fourth transistors, respectively, the CCFL coupled across a secondary of the transformer,
comprising:
turning on the first and fourth transistors to couple the series connection between first and second power supplies with a
first polarity;
turning off the first transistor responsive to a pulse width modulator output, the pulse width modulator being responsive
to current through the CCFL, and turning on the second transistor;
when the current through the series connection is within a predetermined range of zero, initiating a time delay;
at the end of the time delay, turning off the fourth transistor and turning on the third transistor.
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