Display Dimming IC Saves Power And Space In Portables

The LX1686 is a next-generation controller IC for backlight inverter modules that is said to greatly extend dimming capabilities for LCDs and other applications lit by cold-cathode fluorescent lamps. The chip is based on a patent-pending architecture that uses direct-drive digital dimming. Direct-drive topology uses a fixed-frequency PWM control circuit that's connected directly to a high-voltage transformer primary by means of a pair of N-channel FETs. This scheme eliminates the inductor and resonant capacitors required in conventional Royer oscillator-based dimming inverters. In addition, transformers can be smaller when using this IC, resulting in smaller designs and improved efficiency. The chip also incorporates the company's RangeMax lamp current duty-cycle control that enables a 100:1 brightness adjustment ratio.