A 92.2% peak-efficiency self-resonant hybrid switched-capacitor LED driver in 0.18μm CMOS

This paper presents a LED driver IC based on a self-resonant Hybrid-Switched Capacitor Converter (H-SCC) operating in the MHz range. Capacitors and switches of the LED driver are integrated on-chip in a low-cost 5V 0.18μm bulk CMOS technology. The effective chip area is 7.5mm². A conventional SMD output capacitor and a 6.4 mm² 150nH SMD air-core inductor are enough to operate the driver in a compact PCB area. Integrated zero-current detection (ZCD) circuitry enables self-resonant operation and Zero-Current Switching independently of the output current, inductor tolerances and/or parasitics, improving the converter efficiency at light loads. A ZCD threshold control enables continuous conduction mode too, to improve efficiency at large currents. The experimental results show a peak efficiency of 92.2% and a maximum power density of 373mW/mm². The LED driver is able to control a 700mA LED down to 10% of its nominal current and can adjust to LED voltage variations, avoiding the need for LED binning.