Methodology for reducing the filtering capacitor in low-flicker LED drivers

Abstract

The amount of light flicker in an AC–DC light-emitting diode (LED) driver is dependent on the size of filter capacitors. In this study, a study is conducted on reducing the size of filter capacitor in an AC–DC buck–boost/flyback LED driver using flicker index and per cent flicker light measures. Using this approach, a procedure for minimising the filter capacitance is presented. It is then concluded that relatively small filter capacitors such as film or ceramic capacitors can be chosen while meeting light flicker requirements. Hence, an LED drive with a longer lifetime can be achieved when compared with a driver using electrolytic capacitors. Experimental studies are presented for a 20 W AC–DC buck–boost/flyback LED driver prototype which utilises ceramic capacitors for driving Cree CR22-32L and XLamp XP-G LED strings.

Keywords

• driver circuits
• AC-DC power convertors
• ceramic capacitors
• electrolytic capacitors
• flicker noise
• filtering capacitor
• low-flicker LED drivers
• light flicker
• AC–DC light-emitting diode driver
• AC–DC buck–boost
• flyback LED driver
• flicker index
• filter capacitance
• ceramic capacitors
• film capacitor
• electrolytic capacitors
• Cree CR22-32L
• XLamp XP-G LED strings
• power 20 W