Single-switch LED Driver with the Function of Power

Factor Correction

Geun-Yong Park and Gang-Youl Jeong*

Department of Electronic Information Engineering, Soonchunhyang University

22 Soonchunhyang-Ro, Shinchang-Myun, Asan-Si, Choongnam, South Korea

*gangyoul@sch.ac.kr

Abstract.This paper proposes asingle-switch LED driver with the function of

power factor correction (PFC). The proposed driver uses a single-switch power

conversion circuit topology which are the boost converter and the flyback

converter into. The proposed converter can be more simplified than the

conventional LED drivers. An operation principle is explained, briefly, and

exprimental results are shown to verify the performance of the proposed

converter.

Keywords: Single-switch LED driver, boost converter, fly back converter.

1 Introduction

The conventional lamps have many environmental problems such as much lead and

mercury, a lot of power consumption, and short lifetimes. However, because light-

emitting diodes (LEDs) have many advantages such as small size, high luminous

efficiency, long lifetime, fast response, and excellent color rendering, they have been

widely used in many lighting applications. LEDs are environmentally friendly devices

compared with conventional fluorescent lamps that require mercury and may produce

pollution. Therefore, in pursuit of energy-saving and pollution free light sources,

LEDs have gradually replaced fluorescent lamps and have become increasingly and

more widely used [1-8]. Therefore this paper presents a simple single-switch LED

driver with the function of PFC, which can operate LED-lighting device, effectively.

2 Operational principles

Figure 1 shows the main power circuit of the proposed driver. The proposed driver is

composed of a power circuit and a control circuit. Figure 2 shows the theoretical

waveforms of the key parts of the proposed driver.

The proposed driver operates in critical conduction mode (CCM). This is different

from the conventional single-switch LED drivers that operate in either continuous

conduction mode or discontinuous conduction mode. The proposed driver operating

with the CCM has an advantage in that it can achieve zero-voltage switching without

any additional active snubber circuit. Other advantages include a lower THD of the

Advanced Science and Technology Letters Vol.51 (CES-CUBE 2014), pp.20-23

http://dx.doi.org/10.14257/astl.2014.51.05

ISSN: 2287-1233 ASTL Copyright © 2014 SERSC

line current, lower turn-off switching losses, and lower conduction losses due to a

smaller peak inductor current when compared with conventional single-stage LED

converters [6].

Fig. 1. The main power circuit of the proposed single-switch LED driver.

Fig.2. The theoretical waveforms of the key parts of the proposed converter.

D o

S

R

C o

L m

v p v s

iD o

im

V o

v A C V inC inE M I

F ilte r

iA C

I o

ip

v d s

D C -D C B o o s t C o n v e r te rF ly b a c k C o n v e r te r

v A C

V in

iA C

i p

t

T s

v s ,

v g s

tto n t o ff

t

v p

V in

t

-V o /n

v d s

I oV o ,

im

t

I p , p e a k= k V D C = k |v A C |

t

v A C

iA C

V in

i p

t

I p = I p , p e a k2

1

T

i p n iD o

Advanced Science and Technology Letters Vol.51 (CES-CUBE 2014)

Copyright © 2014 SERSC 21

Figure 3 shows the operation modes of the proposed single-switch LED driver in a

positive half cycle of the AC input source, where the bold line represents the

conduction line and the dotted line represents the no conduction line.

(a) Mode A (b) Mode B

Fig.3. The operation modes of the proposed single-stage LED converter.

If the AC input voltage is in a negative half cycle, the rectified DC input voltage

Vin is the same as when the AC input voltage is at a positive half cycle due to the

operation of the FB diode rectifier (Vin=|vAC|). Therefore, the operations of the driver

at a negative half cycle are also the same as in modes A and B. Thus, the f of the

proposed driver in a negative half cycle of the AC input voltage is omitted.

3 Experimental results

Fig.4. The experimental waveforms of the AC input voltage and current, and the DC output

voltage and current of the proposed LED converter.

Fig.5. The experimental waveforms of the key parts of the proposed converter at a line

frequency scale.

C o

D o

V o

C in

v sv p

R:V in

L m

N p N S

v A C

ip

iA C

v d sS

im

iD o I o

C o

D o

V o

C in

v sv p

R:V in

L m

N p N S

v A C

ip

iA C

v d sS

im

iD o I o

Advanced Science and Technology Letters Vol.51 (CES-CUBE 2014)

22 Copyright © 2014 SERSC

Fig.6. The experimental waveforms of the key parts of the proposed converter at a switching

frequency scale.

To validate the feasibility of the proposed LED converter, a prototype converter

was constructed and tested. Figures 4~6 show the experimental waveforms of the key

parts of the proposed driver. These show the good performance of the proposed driver.

4 Concluding remarks

In this paper, a single-switch LED driver with the function of PFC has been proposed,

and the operational principle and the experimental result have been described, briefly,

and shown to verify the feasibility of the proposed driver, respectively. The proposed

driver has good performance as an LED driver.

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Advanced Science and Technology Letters Vol.51 (CES-CUBE 2014)

Copyright © 2014 SERSC 23