A 26 W 97%-Efficiency Fast-Settling Dimmable LED Driver With Dual-nMOS-Sensing Based Glitch-Tolerant Synchronous Current Control for High-Brightness Solid-State Lighting Applications

Abstract

This paper presents an integrated buck-type dimmable synchronous LED driver for high-brightness solid-state lighting applications. A glitch-tolerant synchronous current control (GT-SCC) scheme is proposed to regulate the average LED current. The GT-SCC enables fast settling time of the LED current upon start-up or PWM dimming condition, and provides reliable operation under high dV/dt slewing during switching transitions of the LED driver. The proposed LED driver consists of a high-speed low-power HV synchronous gate driver to enable on-chip synchronous rectification with a dual-nMOS power train under different input voltages for the conduction power loss reduction. Two on-chip senseFET peak and valley current sensors are also developed to offer low-power and reliable current sensing under high input voltages. Implemented in a 0.35 m 50 V CMOS process, the proposed LED driver supports a wide input range from 5 V to 45 V, operates up to 4 MHz with a small-value inductor of 8.2 H, handles a high PWM dimming frequency of 20 kHz with a wide duty-ratio range from 0.1 to 1, and delivers an average LED current of 700 mA for driving up to 12 series-connected HB-LEDs (with the maximum output power of 26 W). The proposed LED driver achieves a peak power efficiency of 97.2% and the current deviation 3.3% of the average LED current under different conditions. The worst-case settling time achieves 3.2 s that is at least 2.7 times improvement over state-of-the-art counterparts.Index Terms-DC-DC LED drivers, dimmable LED driver, high-brightness LED lighting, high-voltage current sensing, high-voltage gate driver, PWM dimming.

Cost-Effective LED Dimming Driver With Single Chip Design for Smart Lighting System

“…This causes the lighting efficiency of PWM method is not appropriated as applied on the high-power LED system. Table 3 lists the results of comparison between the proposed chip and the state-of-the art LED drivers [29][30][31]. Liu et.…”

Design and realization of high-performance LED drivers for automotive lighting applications

“…The second trade-off is between the attributes of high power-efficiency and wide dimming range. Specifically, the wide dimming range is achieved by shortening the duration of the settling time -the time for the output LED current to settle to the predetermined value (from zero) once the dimming function is triggered [50]. The common practice [38], [51] of shortening the settling time is to increase switching frequency of the LED driver which in turn leads to power-efficiency degradation due to increased switching losses [52], [53].…”

“…Settling time is defined as the time for the output LED current to settle to the determined value (from zero) once the dimming function is triggered [50], [86]. Settling time is imperative to the dimming performance of the LED driver because a wide dimming range is often achieved by shortening the settling time.…”

“…It is a critical part of the LED driver because it not only occupies a large silicon area but also consumes a significant portion of the total power loss. For instance, in a reported LED driver [50] that drives a 26W output LED load, the output stage occupies over 60% of the active area and dissipates over 90% of the total power loss.…”

“…As delineated earlier, the accuracy of these current sensors directly ascertains the accuracy of the LED current regulation. To this end, the spikes and valleys of the sensed currents [64], [50], due to current switching in the power transistors are removed by the proposed LEB (in section 3.2.3). In short, the sensed current (iLDP=iLDPMOS/1000-Ib) of the LDPMOS current sensor is 1000 times lower (see Figure 3.13 later for the simulated accuracy) than the current (iLDPMOS) passing through the power transistor (MH1), where the bias current (Ib=5µA) is negligible compared to the sensed current iLDP (0.2mA~1.2mA).…”