Enabling Universal-Input Operation in Electrolytic Capacitor-less LED Drivers Based on Harmonics Injection

Abstract

LED lighting has been introduced as an energy efficient and reliable lighting source since several decades. Not only energy efficiency; the long lifetime of LEDs is another significant feature compared to the conventional florescent lamps. Unfortunately, employing electrolytic capacitors (E-Cap) in the AC-DC drivers deteriorates the actual lifetime of the whole LED lamp since an E-Cap has a shorter lifetime compared to the lifetime of the LED chip itself. Thus, a new family of capacitor-less drivers has been evolved by allowing pulsating output current which helps in replacing the E-Cap by long lifetime capacitors such as film or ceramic. In order to revoke the LEDs failure due to the successive current peak stress, techniques such as harmonics injection have been adopted in order to alleviate the current peaks by injecting selected values of harmonics to reduce it. In this paper, a universal-input electrolytic capacitor-less LED driver based on harmonic injection technique is presented. The proposed driver, employing a flyback topology, operates at wide input voltage range ( $\mathrm{85V}_{\mathrm{AC}}$ to $\mathrm{265V}_{\mathrm{AC}}$ ) while maintaining high power factor (PF) and low peak-to-average-ratio (PTAR) values. The design procedures of the proposed driver are discussed, simulated, and verified experimentally by means of 4.2 W flyback prototype. The control simplicity has been taken into consideration which guarantees the solution is compatible with Integrated Circuits (ICs) technology.