CCFL Controller Reduces LCD Backlighting Costs

Promising to lower the BOM of LCD backlighting designs, the DS3991 single-channel controller for CCFLs supports both push-pull and half-bridge drive schemes. The device converts 5 to 24 Vdc to 300 to 1,400 Vac using a minimal number of external components. Additionally, the push-pull drive scheme provides efficient dc/ac conversion and produces near-sinusoidal waveforms. Supporting both single- and multiple-lamp configurations, the device drives two logic-level, n-channel MOSFETs that appear between a step-up transformer and ground. The transformer has a center tap on the primary side that connects to the dc supply. The DS3991 alternately turns on the two MOSFETs to create the ac waveform on the secondary side. Varying the duration of the MOSFET turn-on times, the controller is able to reliably control the amount of current flowing through the CCFL lamp. Available in a 16-pin SO package, price starts at $0.45 each/1,000. MAXIM INTEGRATED PRODUCTS, Sunnyvale, CA. (800) 998-8800.