A Li-Ion Battery Input Highly Integrated LED Driver With 96.8% Peak Efficiency and Dual-Color Mixing Capability

This article presents an efficient and highly integrated light-emitting diode (LED) driver powered by a Li-ion battery with dual-color mixing capability. In terms of efficiency, the power stage of the proposed driver utilizes only two on-chip NMOS power transistors and can operate at a lower switching frequency, effectively reducing conduction loss and switching loss. Additionally, the inductor-first topology and the floating output voltage enable the elimination of the off-chip capacitors, making a single inductor the only off-chip component. The proposed LED driver chip, fabricated in a 0.18-
$\mu \text{m}$
BCD process, can provide a total LED current ranging from 270 to 550 mA within the voltage range of a Li-ion battery (2.7–4.2 V) with 96.8% peak efficiency. Measurement results demonstrate that the proposed driver can adjust the ratio of a white LED and a phosphor-converted (PC) amber LED to achieve tunable correlated color temperature (CCT) over a wide range. In addition to average current regulation, the driver also supports pulsewidth modulation (PWM) dimming with a duty ratio ranging from 0.5% to 99.5%.