A white LED boost IC for backlight of TFTLCD based on a current-limited pulse-width modulation

This paper presents a boost DC-to-DC switching converter which is implemented with current-limited pulse width modulation (PWM) to drive various white LEDs in the backlight of TFTLCD. The proposed white LED boost IC consists of the bandgap reference, error amplifier, hysteresis comparator, linear ramp generator, voltage-to-current converter and driving buffer which are designed and implemented with a standard 0.35-μm 2P4M CMOS technology. Notify that the proposed bandgap reference can provide a reference voltage and a reference current, simultaneously. Besides, the white LED boost IC can eliminate sub-harmonic oscillation using a slope-compensation technique. Simulation results show that the output voltage, output current, output voltage ripple and output current ripple are 18 V, 20 mA, 5.98 mV and 41.8 μA, respectively, at a power supply of 3.3 V. The proposed white LED boost IC can drive five white LEDs with a power efficiency of 85% and a chip area of 0.89×0.92 mm².