A fast-switching current-pulse driver for LED backlight

In this paper, a fast-switching current-pulse driver for light emitting diodes (LED) backlight is proposed. It uses a regulated drain current mirror (RD-CM) and a high-voltage NMOS transistor (HV-NMOS). It achieves the fast-response current-pulse switching by using a dynamic gain-boosting amplifier (DGB-AMP). The DGB-AMP does not discharge the large HV-NMOS gate capacitance of the RD-CM when the output current switch turns off. Therefore, it does not need to charge the HV-NMOS gate capacitance when the switch turns on. The proposed current-pulse driver achieves the fast current switching by removing the repetitive gate discharging and charging. Simulation results were verified with measurements performed on a fabricated chip using a 5 V/40 V 0.5 mum BCD process. It reduces the switching delay to 360 ns from 700 ns of the conventional current-pulse driver.