To obtain sufficient luminance and achieve higher reliability, light-emitting diodes (LEDs) are usually arranged in parallel strings in many high-power applications. Since current imbalance should be avoided among the parallel LED strings, a multi-channel constant current LED driver based on high-frequency AC bus is proposed in this study. The proposed driver is composed of one resonant inverter followed by passive resonant rectifiers according to the number of LED strings. The amplitude of the high-frequency AC bus voltage is regulated by the resonant inverter and each LED string is individually powered with constant current by its corresponding passive resonant rectifier. The proposed driver is characterised by low cost and high efficiency. Finally, a prototype is built to verify the performance of the proposed driver.

Analysis and design of a multi-channel constant current light-emitting diode driver based on high-frequency AC bus

Prognostics for lithium-ion batteries using a two-phase gamma degradation process model

Reliability study of LED driver – a case study of black box testing

This paper introduces a megahertz-frequency resonant dc-dc converter that inherently achieves a load-independent output current while maintaining high efficiency across a wide output voltage range. These properties make the proposed converter well-suited for automotive LED driver applications, where a varying number of LEDs need to be driven with a constant current. The proposed converter achieves load-independent output current by utilizing an LCL-T resonant network, and achieves high efficiency by operating at a fixed switching frequency with optimized magnetics. This LCL-T resonant converter is also capable of regulating its output current at any desired value by utilizing phase-shift control. The performance of the LCL-T resonant converter is theoretically and experimentally compared with the recently proposed LC3L resonant converter. For the experimental comparison, the prototypes of the LCL-T and the LC3L resonant converters are designed for 2-MHz operation across an output voltage range of 3 V to 50 V (corresponding to a string of 1 to 15 LEDs) while supplying a constant 0.5 A output current to the LEDs. The LCL-T resonant converter prototype achieves a peak power stage efficiency of 94.5%, which is 1% higher than the peak efficiency of the LC3L converter prototype. Furthermore, the LCL-T converter prototype maintains 1.5% higher average efficiency over its output voltage range relative to the LC3L converter prototype.

High-Performance Megahertz-Frequency Resonant DC-DC Converter for Automotive LED Driver Applications

This paper introduces a megahertz-frequency resonant dc–dc converter that inherently achieves a load-independent output current while maintaining high efficiency across a wide output voltage range. These properties make the proposed converter well-suited for automotive light-emitting diode (LED) driver applications, where a varying number of LEDs need to be driven with a constant current. The proposed converter achieves load-independent output current by utilizing an LCL -T resonant network, and achieves high efficiency using a comprehensive design optimization methodology. This LCL -T resonant converter is also capable of regulating its output current at any desired value by utilizing phase-shift control. The performance of the LCL -T resonant converter is theoretically and experimentally compared with an LC 3 L and an LCLC resonant converter. For the experimental comparison, prototypes LCL -T, LC 3 L , and LCLC resonant converters are designed to operate at 2 MHz and across an output voltage range of 3.3–49.5 V while supplying a constant 0.5 A output current to the LEDs. The LCL -T resonant converter prototype achieves a peak efficiency of 91.1%, which is 0.6% and 1.8% higher than the peak efficiency of the LC 3 L and the LCLC converter prototypes, respectively. Furthermore, the LCL -T converter prototype maintains 0.8% and 1.6% higher average efficiency over its 15:1 output voltage range relative to the LC 3 L and the LCLC converter prototypes, respectively.

High-Performance Megahertz-Frequency Resonant DC–DC Converter for Automotive LED Driver Applications

LED is generally driven by constant current because the color and brightness of LED are directly related to their forward current. The current accuracy is a very important index for a high performance LED driver. In this paper, a constant current source applied in LED driver is proposed to improve the accuracy of the LED current. The constant current source consists of a reference current generator, a current mirror and a current regulator. An accurate current mirror with high impedance is utilized which eliminates the channel length modulation effect of the MOSFETs. A new current regulator in which MOSFET operates in linear region instead of saturation region is proposed to improve the current accuracy and the driver's efficiency. The proposed circuit is based on chartered 0.35μm 3.3/5 V process and has been simulated by Cadence spectre. The output current is 150 mA. Simulation results show that current accuracy of +/-0.5% for a wide output voltage range from 0.35 V to 13 V is obtained.

Li Geng

Papers

A High Precision Constant Current Source Applied in LED Driver