A High-Power-Factor Dimmable LED Driver with Integrated Boost Converter and Half-Bridge-Topology Converter

Abstract

This paper proposes a dimmable light-emitting diode (LED) driver featuring a high power factor and zero-voltage switching on (ZVS). The circuit is obtained by integrating a boost converter and a dc-dc converter with half-bridge topology. The high power factor is achieved by operating the boost converter in discontinuous current mode (DCM). The LEDs are dimmed by the control scheme of asymmetrical pulse-width modulation (ASPWM). The developed circuit eliminates the inherited dc-offset current of the transformer in a conventional asymmetrical half-bridge converter by introducing a balance capacitor. Both active switches can operate at ZVS by freewheeling the boost inductor current and the transformer magnetizing current to discharge the energy stored in their parasitic capacitance. The circuit operation is analyzed in detailed, and mathematical equations are derived. Finally, a 115-W prototype circuit for driving high brightness LEDs was built and tested. The experimental results verify the feasibility of the proposed LED driver with satisfactory performance. It can achieve a high power factor and ZVS operation.

An Influence of Parameters of the Control Signal of Power LEDs on Their Junction Temperature and Emitted Light

“…All the presented E(I AVG ) dependences are monotonically increasing functions. An increase in the frequency causes a decrease in the value of E. This phenomenon is associated with the phenomenon of self-heating and a decrease in the illuminance value with an increase in the junction temperature of the LED [19]. For the MCE series LED, at f = 200 kHz and I AVG = 0.7 A, the illuminance has 5% lower values compared with the values measured with the DC power supply.…”

“…Papers [17][18][19][20] describe techniques and systems using full-bridge power converters with soft switching techniques as control systems for single power LEDs or LED modules in order to improve the power quality characterized by the total harmonic distortion (THD) of the supply current. These systems are prepared to be supplied from the power grid or from photovoltaic systems with the use of the dedicated DC energy accumulators, for off-grid operation when supplying highways lighting lamps.…”