A dimmable LED driver using resistive DAC feedback control for adaptive voltage regulation

Abstract

This paper proposes a dimmable, energy-efficient LED driver for applications in interior lighting. High efficiency is achieved by an adaptive voltage regulation, which minimizes power losses in the linear current regulator. A digital control mechanism employing a resistive DAC for feeding the analog feedback input of a DC-DC converter is introduced. It is shown that the digital control methodology gives maximum design flexibility and enhances control over regulation speed and stability. In an experimental setup the proposed concept is verified and evaluated. Operating at an input voltage of 24 V the LED driver provides a relatively wide output voltage range of 3.5 V to 38 V. Output current is regulated to 700 mA with a steady-state precision of more than 98.8 %, while PWM dimming with a frequency of 1 kHz and shortest on-time of 4 μs is employed. A peak efficiency of the complete system of 93.9 % is achieved.