A Wide-Input-Range Low-Profile Adaptive Delay Compensated Hysteretic LED Driver With Enhanced Current Accuracy

Abstract

This article presents a wide-input-range low-profile dc–dc-based LED driver. An adaptive delay compensated hysteretic control (ADCHC) is proposed to adaptively modulate both peak and valley inductor currents for minimizing their current deviations, thereby enhancing the accuracy of the average LED current under different input and output voltages. A high-voltage current sensor with passive ripple filtering scheme is also developed to ensure fast and accurate inductor current sensing in the megahertz (MHz) range. The proposed LED driver was realized using two 100-V e-mode GaN FETs as power switches together with on-chip gate drivers and controller implemented in a 0.5- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> , 120-V process. This driver supports an input voltage range from 5 to 100 V and delivers a maximum output power of 25 W. The LED current error is minimized to within ±3.2% of the nominal 350-mA LED current under different input voltages and numbers of output LEDs. Compared with the prior art, the proposed LED driver has the smallest LED current error, operates 2 times higher frequency, and uses <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5\times $ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5.5\times $ </tex-math></inline-formula> smaller inductance and inductor volume. The proposed LED driver also features competitive peak power efficiency of 91.7% at 1.8-MHz frequency and 90-V input.