Abstract
Traditional light-emitting diode (LED) drivers with pulse-width modulation (PWM)-type converters suffer the problem of hard switching, leading to low circuit efficiency and low reliability. LED drivers supplied by alternating current (AC) line source generally require using an additional power-factor correction (PFC) stage to satisfy the regulations on power factor (PF) and total current harmonic distortion (THDi). It results in more circuit losses, especially when the active switch of the PFC stage operates at hard switching. This paper presents an alternating current-to-direct current (AC/DC) converter for driving high-brightness LEDs with the features of soft switching and high PF. The proposed single-stage circuit is formed by integrating a buck–boost converter and a buck converter. By elaborately rearranging the wirings between the circuit components of both converters, the power MOSFETs can be switched on at zero voltage. The operating modes at steady-state are analyzed and the mathematical equations for deriving circuit parameters are conducted. Finally, a prototype circuit for driving 60-W LEDs was built and measured. Based on the experimental results, the feasibility and satisfactory performance of the proposed LED driver are proved.
Highlights
IntroductionOn the purpose of increasing the utilization factor of the power electric equipment and reduce the electromagnetic interference (EMI), some regulations such as IEC 61000-3-2 and IEEE 519, are enacted to restrict the power factor (PF) and total current harmonic distortion (THDi) of the alternating current-to-direct current (AC/DC) light-emitting diode (LED) drivers to a reasonable range
Nowadays, high-brightness light-emitting diodes (LEDs) are popularly used to replace incandescent and fluorescent lamps in many applications owing to their advantages of small size, high luminous efficiency, long lifespan, high reliability, and environmental friendliness [1,2,3].On the purpose of increasing the utilization factor of the power electric equipment and reduce the electromagnetic interference (EMI), some regulations such as IEC 61000-3-2 and IEEE 519, are enacted to restrict the power factor (PF) and total current harmonic distortion (THDi) of the alternating current-to-direct current (AC/DC) LED drivers to a reasonable range
In order to meet these regulations, an additional converter serving as a power-factor correction (PFC) stage is added to a DC/DC converter of which the output voltage is adjusted to drive LEDs
Summary
On the purpose of increasing the utilization factor of the power electric equipment and reduce the electromagnetic interference (EMI), some regulations such as IEC 61000-3-2 and IEEE 519, are enacted to restrict the power factor (PF) and total current harmonic distortion (THDi) of the alternating current-to-direct current (AC/DC) LED drivers to a reasonable range. In order to meet these regulations, an additional converter serving as a power-factor correction (PFC) stage is added to a DC/DC converter of which the output voltage is adjusted to drive LEDs. In order to meet these regulations, an additional converter serving as a power-factor correction (PFC) stage is added to a DC/DC converter of which the output voltage is adjusted to drive LEDs It results in a LED driver with two power-process stages. The two-stage approaches take two energy-conversion processes, and produce more losses including switching loss and conduction loss.
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