Light-emitting diode driver with low-frequency ripple suppressed and dimming efficiency improved

• Published in: IET power electronics Vol. 7; no. 1; pp. 105 - 113
• Main Authors: Hwu, Kuo-Ing, Tu, Wei-Cheng, Lai, Chung-Yu
• Format: Journal Article
• Language: English
• Published: Stevenage The Institution of Engineering and Technology 01.01.2014; The Institution of Engineering & Technology
• Subjects: capacitors; circuit stability; Circuits; Commands; Converters; critical mode control integrated circuit; detector circuits; Dimming; dimming circuit; double line frequency ripple converter; driver circuits; Electric potential; energy‐recycling circuit; gate voltage detecting circuit; instantaneous input power; instantaneous output power; LED; Light-emitting diodes; light‐emitting diode driver; low‐frequency voltage ripple suppression; luminance; metal oxide semiconductor field effect transistor; output capacitor; output voltage ripple reduction; power convertors; power factor correction; power MOSFET; reference circuits; Ripples; single‐stage power‐factor‐corrected flyback converter; stability; Voltage; voltage reference command; luminance; single-stage power-factor-corrected flyback converter; metal oxide semiconductor field effect transistor; instantaneous input power; detector circuits; power factor correction; energy-recycling circuit; gate voltage detecting circuit; stability; output voltage ripple reduction; instantaneous output power; power convertors; low-frequency voltage ripple suppression; output capacitor; driver circuits; power MOSFET; dimming circuit; LED; light emitting diodes; critical mode control integrated circuit; capacitors; light-emitting diode driver; voltage reference command; circuit stability; double line frequency ripple converter; reference circuits
• ISSN: 1755-4535; 1755-4543; 1755-4543
• DOI: 10.1049/iet-pel.2013.0117

In this study, a single-stage power-factor-corrected flyback converter is used as the main power stage, which is controlled by a critical mode control integrated circuit and is used to drive light-emitting diode (LED) strings. Since the output voltage of this converter possesses a double line frequency ripple, one energy-recycling circuit without any control is added to render the instantaneous output power close to the instantaneous input power, so as to reduce the energy stored/released in the output capacitor and hence to reduce the output voltage ripple of the double line frequency. Accordingly, the effect of the low-frequency voltage ripple on the colour, luminance, life and stability of the LED can be reduced. For the dimming circuit to be considered, the gate voltage detecting circuit is employed herein so as to achieve efficiency improvement in LED dimming. Based on the dimming command and the variation in gate voltage, the voltage reference command for the flyback converter is dynamically adjusted so as to make the voltage across the metal oxide semiconductor field effect transistor reduced as the LED string is dimmed up/down and hence to increase the efficiency of the overall system.