Light emitting diode constant-current driver design using by pulse-width modulation dimming control

Abstract

An LED constant-current driver was designed and presented by a pulse width modulation (PWM) dimming control circuit, a overheat protection circuit (OTP), a bandgap circuit, a current controlled oscillator and a temperature process compensation bandgap circuit (TPC). The PWM provides a duty cycle from 10% to 90%. In order to reduce the area of the layout, the TPC circuit use MOSFET to replace the traditional BJT and resister. The OTP circuit provides the negative temperature coefficient voltage to achieve the overheat protection mechanism. The propose design is implemented using TSMC 0.35 μm CMOS process and the temperature of the simulation environment ranges from 0 °C, to 150 °C. The post-layout-extracted simulation results reveal that the current channel provides 30 mA. The area of chip is 1.1 mm2 and power consumption is 0.314 mW justified by HSPICE simulations.