This paper presents a single-stage flyback power factor- correction (PFC) front-end for high-brightness light emitting- diode (HB LED) applications. The proposed PFC front-end circuit combines the PFC stage and the dc/dc stage into a single stage. Experimental results obtained on a 78-W (24- V/ 3.25-A) prototype circuit show that at VIN = 110 Vac, the proposed PFC front-end for HB LED applications can achieve an efficiency of 87.5%, a power factor of 0.98, and a total harmonic distortion (THD) of 14% with line-currents harmonics that meet the IEC 61000-3-2 Class C standard.
- high-brightness light emitting diodes (HB LEDs)
- power factor correction (PFC)
Fig. 1. Proposed PFC front-end for HB LED application
EXPECTED SIMULATION RESULTS:
(a) LB = 83 μH
(b) LB = 166 μH
Fig. 2. Measured line current and voltage waveforms at VIN = 110 V AC with N1 = N2 = 12 turns, (a) LB = 83 μH;
(a) LB = 83 μH
(b) LB = 166 μH
Fig. 3. Measured current and voltage waveforms, (a) LB = 83 μH; (b) LB = 166 μH. CH1: Current of primary winding N2, CH4: Current of inductor LB; CH3: Drain-to-source voltage of switch Q1. Voltage scale: 200 V/div., current scale: 2 A/div., time scale: 4
Fig. 4. Measured line voltage and current waveforms at VIN = 110 V AC with N1/N2 = 4/26, LB = 166 μH, and LM = 645 μH
Fig. 5. Measured line voltage and current waveforms at VIN = 274 V AC with N1/N2 = 4/26, LB = 415 μH, and LM = 645 μH
A single-stage flyback power-factor-correction front-end for HB LED application is presented in this paper. With the integration of the PFC stage and dc/dc stage, significant reduction of component count, size, and cost can be achieved. Experimental results obtained on a prototype show that at VIN = 110 V AC, VO = 24 V, and IO = 3.25 A, the proposed PFC front-end for LED driver has achieved an efficiency of around 87.50%, a power factor of 0.98 and a total harmonic distortion (THD) of 14% for the line current with harmonic contents meeting IEC 61000-3-2 Class C standard. Experimental results have also been obtained at high line when the inductance of the input current shaping inductor is increased. Measured output voltage ripple with an actual LED load at VO = 24 V, IO = 3.8 A is less than 20 mV. Therefore, LED strings can be directly driven without a post regulator, improving the efficiency, lowering the cost, and reducing the size.
 J. Y. Tsao, “Solid-state lighting: lamps, chips, and materials for tomorrow,” IEEE Circuits and Devices Magazine, vol. 20, no. 3, pp. 28 – 37, May-June 2004.
 N. Narendran and Y. Gu, “Life of LED-based white light sources,” Journal of Display Technology, vol. 1, no. 1, pp. 167 – 171, Sept. 2005.
 T. Komine and M. Nakagawa, “Fundamental analysis for visible-light communication system using LED lights,” IEEE Transactions on Consumer Electronics, vol. 50, no. 1, pp. 100 – 107, Feb. 2004.
 Electromagnetic Compatibility (EMC), Part 3-2: Limits – Limits for harmonic current emissions (equipment input current ≤ 16 A per phase), International Standard IEC 61000-3-2, 2001.
 ON Semiconductor, “90 W, universal input, single stage, PFC converter,” www.onsemi.com/pub_link/Collateral/ AND8124-D.PDF, Dec. 2003.