A low-power and low-cost digitally-controlled boost LED driver IC for backlights

This paper describes an LED driver IC based on a digitally-controlled boost converter for LCD backlighting. We propose a new time-based analog-to-digital Converter (ADC) with variable quantization steps and a lowest voltage selector (LVS) based on the time-digitizing circuits to secure continuous conduction mode (CCM) operation of the boost converter. The proposed ADC and LVS can be fully implemented on a small silicon area and is suitable to low power controller for LED driver IC. The 2-channel LED driver IC fabricated on a 0.35um BCD process occupies the active area of 1.35mm² including the entire compensation filter. The maximum efficiency is measured to be 90% or more and the start-up settling time is within 800μs.