NEW DIRECT DRIVE CCFL CONTROLLER FROM SOLID STATE SUPPLIES

By limiting VDDP to 5.5V and using advanced processing, the die size and package pin count is decreased while improving dimming precision. Designers can select normal or reverse polarity dimming and program minimum and maximum lamp currents with high levels of precision by using resistors. Operating directly from a single Li-Ion cell, the device provides high Nits/Watt efficiency.

The direct drive architecture used in the device works with system voltages from 3 volts to more than 50 volts and is limited only by the external power FETs which drive the high voltage transformer. The fault shutdown feature used in the LX1691 is enhanced to include regulation and shutdown for overvoltage and over current conditions.

The LX1691 features a strike method which allows significant efficiency gains while guaranteeing strong striking power at all operating temperatures. This method sweeps the strike frequency smoothly up to the unloaded resonant frequency of the lamp and high voltage transformer. This, coupled with the component’s active high output voltage regulation, produces just enough strike voltage without generating unpredictable high voltage spikes which cause arcing and component failure.

Solid State Supplies also offer the LX1691B which is similar but has a guaranteed minimum lamp strike interval of 1 second to meet notebook and monitor panel manufacturers’ specifications. This version also adds feed forward input voltage sensing to enhance transient response when used in inverters which derive lamp power from unregulated input supplies and batteries.

Inverter modules designed using either components can be designed for virtually any CCFL appliance from digital cameras, PDA’s to big screen monitors and driver viewable automotive displays.