AC–DC Flyback Dimmable LED Driver with Low-Frequency Current Ripple Reduced and Power Dissipation in BJT Linearly Proportional to LED Current

Yeu-Torng Yau, Kuo-Ing Hwu and Kun-Jie Liu
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Yeu-Torng Yau: Department of Ph.D. Program, Prospective Technology of Electrical Engineering and Computer Science, and Department of Electrical Engineering, National Chin-Yi University of Technology, No.57, Section 2, Zhongshan Rd., Taiping District, Taichung 41170, Taiwan
Kuo-Ing Hwu: Department of Electrical Engineering, National Taipei University of Technology, 1, Section 3, Zhongxiao E. Rd., Taipei 10608, Taiwan
Kun-Jie Liu: Chicony Power Technology Co., Ltd., Sanchong, New Taipei City 24158, Taiwan

Energies, 2020, vol. 13, issue 16, 1-18

Abstract: In this paper, a dimmable light-emitting diode (LED) driver, along with the low-frequency current ripple decreased and the bipolar junction transistor (BJT) power dissipation reduced, is developed. This driver is designed based on a single-stage flyback converter. On the one hand, the low-frequency output current ripple reduction is based on the physical behavior of the linear current regulator. On the other hand, when the voltage across the LED string is decreased/increased due to dimming or temperature, the output voltage of the flyback converter will be automatically regulated down/up, thereby making the power dissipation in the BJT linearly proportional to the LED current. By doing so, not only the power loss in the linear current regulator will be decreased as the LED current is decreased or the LED temperature rises, but also the output current ripple can be reduced. Furthermore, the corresponding power factor (PF) is almost not changed, and the total harmonic distortion (THD) is improved slightly. In addition, the LED dimming is based on voltage division. Eventually, a 30 W LED driver, with an input voltage range from 85 to 295 V rms and with 24 LEDs in series used as a load, is developed, and accordingly, the feasibility of the proposed LED driver is validated by experimental results.

Keywords: bipolar junction transistor (BJT); current ripple; light-emitting diode (LED); dimmable; linear current regulator; output voltage automatic regulator; power factor (PF); single-stage AC–DC flyback converter; total harmonic distortion (THD) (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2020
References: View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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