High Efficiency Adaptive Boost Converter for LED Drivers

This paper presents the design and simulation results of an 89% power efficient CMOS adaptive controlled boost (step-up) LED driver implemented in 0.25 mu m BCD (Bipolar CMOS DMOS) technology. A novel adaptive minimum frequency control provides up to 32 V from a single battery (3.6 V to 5.5 V) input supply to 10 series-connected LEDs at the output. The proposed control scheme provides an accurate load current (3-50 mA) while achieving 6% - 12% higher power efficiency than conventional fixed on-time schemes. The novel control circuitry is able to switch between PWM (Pulse width modulation) and PFM (Pulse frequency modulation) automatically by calculating the feedbacks from the inductor and LED's currents. This controller is functional from light to heavy loading situations which is critical in improvement of power efficiency and battery life-time for high-boost ratio applications in order as provide accurate LED current.