Capacitance Reduction With An Optimized Converter Connection Applied to LED Drivers

Abstract

This paper presents a new control method and a detailed project methodology for the optimized connection method of two converters, aiming to reduce the redundant power processing, in order to supply high power LEDs with reduced capacitance and high efficiency, directly from the AC line. This connection method allows dealing with two major issues related to the LED driver: capacitance reduction and efficiency increasing. The first converter provides Power Factor Correction (PFC), while the second converter controls the current through the LED. The basic idea consists in making the second converter to process only the low frequency ripple of the first converter, thus smoothing the LED current. In this way, the low frequency ripple is managed by the second stage so that the capacitance of the first stage can be significantly reduced. The proposed control method can achieve better results for the low frequency compensation. Besides that, a high power factor and a low harmonic content are obtained, fulfilling the IEC 61000-3-2 class C requirements. A laboratory prototype with a rated power of 75 W and an input voltage of 220 Vrms/60 Hz was built in order to show the feasibility of the idea. The measured overall efficiency of the converter was 91% and electrolytic capacitors were avoided.

An E-capless AC-DC CRM Flyback LED Driver with Variable On-time Control

“…The second type is working on the control loop of the converters in order to lower the output current ripple without the need for increasing the capacitor size [10], [11]. The third type is using a relatively new approach in which the majority of the input power reaches the LEDs through one stage of conversion while the rest of the power is processed in some other stages after passing the first stage toward the LEDs [12].…”

Analysis of a Resonant AC‐AC LED Driver

“…It is well known that many electronic converters are using an input rectifier and a high-electrolytic filtering capacitance [1,2]. In high frequency commutations, this electrolytic capacitors have reliability issues, and this fact is limiting the lifetime of the overall LED system [3][4][5][6][7]. In addition, the use of high capacitance electrolytic capacitors remains a problem in achieving high power density and high power factor.…”

A Dual Voltage Control Strategy for Single-Phase PWM Converters With Power Decoupling Function

“…Depending on their circuit configurations, they can generally be classified into two categories, i.e., shunt compensation circuits [16][17][18][19][20][21][22][23][24][25] and series compensation circuits [26,27]. For the shunt compensation circuits, they can be further divided into two subgroups with one group using inductors as the energy storage element, and the other one using film capacitors instead.…”