A peak current mode controlled sepic led driver design considering power factor and flicker

Abstract

In this paper, a peak current mode controlled single ended primary inductor converter (SEPIC) LED driver is proposed to control the brightness of the LED. One string of 37 series connected LEDs is adopted as output of the circuit. The proposed control strategy is based on measuring MOSFET peak current value using a shunt resistor. When this voltage reaches peak threshold value, controller turns off MOSFET. The output current is adjusted to desired levels by changing this peak threshold value. The power factor in the AC power supply side is low because of the full wave bridge rectifier with capacitor filter at the input of the converter. The proposed control strategy is applied with power factor correction (PFC) circuit where input voltage is multiplied by control voltage to achieve high power factor. In PFC circuit, although the line current waveform is slightly distorted due to voltage limitations in integrated circuit (IC) chip used for the proposed control strategy, power factor is kept above 0.9 for operation region between 100mA-300mA. In addition, flicker on LED string is measured for operating current region and flicker limits are revealed. Adjustable output current levels, low flicker on LED string, MOSFET peak current control at each cycle, fast output dynamics, and high power factor are acquired by the proposed control strategy.