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Article

A Single-Stage High-Power-Factor Light-Emitting Diode (LED) Driver with Coupled Inductors for Streetlight Applications

Department of Electrical Engineering, I-Shou University, Dashu District, Kaohsiung City 84001, Taiwan
*
Author to whom correspondence should be addressed.
Appl. Sci. 2017, 7(2), 167; https://doi.org/10.3390/app7020167
Submission received: 31 October 2016 / Revised: 23 January 2017 / Accepted: 3 February 2017 / Published: 10 February 2017

Abstract

:
This paper presents and implements a single-stage high-power-factor light-emitting diode (LED) driver with coupled inductors, suitable for streetlight applications. The presented LED driver integrates an interleaved buck-boost power factor correction (PFC) converter with coupled inductors and a half-bridge-type series-resonant converter cascaded with a full-bridge rectifier into a single-stage power conversion circuit. Coupled inductors inside the interleaved buck-boost PFC converter sub-circuit are designed to operate in discontinuous conduction mode (DCM) for achieving input-current shaping, and the half-bridge-type series resonant converter cascaded with a full-bridge rectifier is designed for obtaining zero-voltage switching (ZVS) on two power switches to reduce their switching losses. Analysis of operational modes and design equations for the presented LED driver are described and included. In addition, the presented driver features a high power factor, low total harmonic distortion (THD) of input current, and soft switching. Finally, a prototype driver is developed and implemented to supply a 165-W-rated LED streetlight module with utility-line input voltages ranging from 210 to 230 V. Experimental results demonstrate that high power factor (>0.99), low utility-line current THD (<7%), low-output voltage ripples (<1%), low-output current ripples (<10%), and high circuit efficiency (>90%) are obtained in the presented single-stage driver for LED streetlight applications.

1. Introduction

Instead of incandescent bulbs with poor lighting efficiency, light-emitting diode (LED) light sources offer high luminous efficacy, long lamp-life, and are mercury-free alternatives for indoor and outdoor lighting applications [1,2,3]. Consequently, LEDs has been widely utilized in our daily lives such as streetlights, flashlights, backlight sources, displays, decorative lighting, automotive lighting, and so on [4,5,6,7,8,9,10,11,12,13,14,15,16].
Streetlights, which illuminate a road, aim to provide a safe environment during the night-time for motorcycle/bicycle drivers and pedestrians [3,17,18]. Traditional lighting sources for streetlight applications have been high-pressure mercury lamps because of their low-cost. However, high-pressure mercury lamps are not energy efficient. In addition, the discharge tube containing mercury vapors is harmful in terms of polluting our environment when the lamp runs out. Therefore, LEDs have begun to replace the conventional high-pressure mercury streetlight. The conventional two-stage LED driver supplying a rated lamp power of greater than 70 W for streetlight applications, shown in Figure 1, consists of an input low-pass filter (Lf and Cf) connected with a full-bridge rectifier (D1, D2, D3 and D4), an interleaved boost power factor correction (PFC) converter (including two capacitors Cin1 and Cin2, two diodes DB1 and DB2, two inductors L1 and L2, two power switches S1 and S2, and a DC-linked capacitor CB), and a half-bridge-type LLC resonant converter (including a Direct-Current (DC)-linked capacitor CB, two power switches S3 and S4, a resonant capacitor Cr, a resonant inductor Lr, a center-tapped transformer T1 with two output windings, two output diodes D5 and D6 and an output capacitor Co), along with a LED [19]. Due to two-stage power conversions, the circuit efficiency is limited and more power switches and components are required in the conventional driver.
In response to these challenges, this paper presents and implements a single-stage LED driver with coupled inductors and high power factor for streetlight applications. Descriptions and analysis of operational modes, and design equations of key components in the presented LED driver, and experimental results obtained from a prototype circuit are demonstrated.

2. Descriptions and Operational Modes Analysis of the Presented Single-Stage LED Driver

Figure 2a shows the original two-stage driver circuit suitable for supplying an LED streetlight module, which consists of two buck-boost PFC converters with interleaved operation and a half-bridge-type series resonant converter cascaded with a full-bridge rectifier. The two coupled inductors are employed instead of single-winding inductors in order to accomplish buck-boost conversion. Figure 2b shows the presented LED driver with coupled inductors and interleaved PFC feature by utilizing the synchronous switch technique to simplify power switches and integrate the two-stage configuration into single-stage one. Figure 2b shows the presented LED driver for streetlight applications, which combines an interleaved buck-boost PFC converter with a half-bridge-type series resonant converter cascaded with a full-bridge rectifier into a single-stage power conversion. The interleaved buck-boost PFC converter sub-circuit consists of two capacitors (Cin1 and Cin2), two coupled inductors (LB11 and LB12; LB21 and LB22), four diodes (DB11, DB12, DB21, and DB22), two power switches (S1 and S2), and a DC bus capacitor (CDC). The half-bridge-type series resonant converter cascaded with a full-bridge rectifier sub-circuit includes a DC bus capacitor (CDC), two switches (S1 and S2), a resonant capacitor (Cr), a resonant inductor (Lr), four diodes (Do1, Do2, Do3 and Do4), and a capacitor (Co) along with the LED streetlight module. In addition, coupled inductors (LB11 and LB12; LB21 and LB22) are designed to be operated in discontinuous conduction mode (DCM) in order to naturally achieve input-current shaping. In addition, the diodes DB12 and DB21 are used to block the current going from the utility-line voltage source into the inductors LB12 and LB21. Besides, the diodes DB11 and DB22 are capable of preventing the inductor currents going back to the input capacitors Cin1 and Cin2. Since the input voltage of each buck-boost PFC converter (the voltage on the capacitor Cin1 or Cin2) is half of the utility-line voltage, the peak current of each coupled inductor and the DC bus voltage will also be half. Because the DC bus voltage is reduced, the presented LED driver is suitable for the applications with high utility-line voltage. Additionally, the input-current harmonics can be reduced by the interleaved operation, so that the size of the input low-pass filter can be miniaturized [20].
Figure 3 shows the utilized control circuit diagram of the presented single-stage LED driver for streetlight applications. With using a constant-voltage/constant-current controller (IC1 SEA05) for regulating the LED streetlight module’s output voltage and current, the output LED voltage Vo can be sensed through resistors Rvs1, VR1 and Rvs2, and the output LED current can be sensed through resistor R3. The sensed output signal from pin 5 of the IC1 feeds into the high-voltage resonant controller (IC3 ST L6599) through a photo-coupler (IC2 PC817). Two gate-driving signals vGS1 and vGS2 are generated from pin 15 and pin 11, respectively, of the IC3, to carry out regulation of the LED streetlight module’s output voltage and current.
Figure 4 presents the simplified circuit of the presented single-stage LED driver for streetlight applications, obtained while analyzing the operational modes. In order to analyze the operations of the presented LED driver, the following assumptions are made.
(a)
Since the switching frequencies of the two switches S1 and S2 are much higher than those of the utility-line voltage vAC, the sinusoidal utility-line voltage can be considered as a constant value for each high-frequency switching period.
(b)
VREC1 and VREC2, respectively, represent the rectified input voltage sources for the capacitors Cin1 and Cin2.
(c)
Power switches are complementarily operated, and their inherent body diodes and drain-source capacitors (CDS1 and CDS2) are considered.
(d)
The conducting voltage drops of diodes DB11, DB12, DB21, DB22, Do1, Do2, Do3 and Do4 are neglected.
(e)
Coupled inductors (including LB11 and LB12; LB21 and LB22) are designed to be operated in DCM for naturally achieving PFC.
The operating modes and the key waveform of the presented LED driver for streetlight applications are shown in Figure 5 and Figure 6, respectively, and the analyses of operations are described in detail in the following.
Mode 1 (t0t < t1; in Figure 5a): The body diode of switch S1 is forward-biased at time t0, and this mode begins. The resonant capacitor Cr provides energy to the inductor Lr, capacitors CDS2 and Co and to the LED through diodes Do2 and Do3. The diode DB21 is forward-biased and coupled inductors LB21 and LB22 provide energy to capacitor CDS2 through diode DB21. At time t1, the drain-source voltage vDS1 of power switch S1 is zero and S1 turns on with zero-voltage switching (ZVS); then this mode ends.
Mode 2 (t1t < t2; in Figure 5b): When switch S1 achieves ZVS turn-on at t1, this mode starts. The rectified input voltage source VREC1 provides energy to coupled inductor LB11 through diode DB11 and switch S1, and diode DB12 is reverse-biased during this mode. The inductor current iLB11 linearly increases from zero, and can be expressed as:
i L B 11 ( t ) = | 2 v A C r m s sin ( 2 π f A C t ) | 2 L B 11 ( t t 1 ) ,
where vAC-rms is the root-mean-square (rms) value of input utility-line voltage, and fAC is the utility-line frequency.
The DC bus capacitor CDC and resonant inductor Lr provide energy to capacitors CDS2, Cr and Co and to the LED through diodes Do1 and Do4. Coupled inductors LB21 and LB22 continue providing energy to capacitor CDS2 through diode DB21. This mode ends when current iLB22 decreases to zero at t2.
Mode 3 (t2t < t3; in Figure 5c): Voltage source VREC1 continues providing energy to coupled inductor LB11 through diode DB11 and switch S1. Capacitors CDC and CDS2, along with resonant inductor Lr provide energy to capacitors Cr and Co and to the LED through diodes Do1 and Do4. At t3, the coupled-inductor current reaches its peak value, defined as iLB11-pk(t), and is given by:
i L B 11 p k ( t ) = | 2 v A C r m s sin ( 2 π f A C t ) | 2 L B 11 D T S ,
where D and TS are the duty cycle and period of the power switch, respectively.
This mode ends when diode DB12 becomes forward-biased at t3.
Mode 4 (t3t < t4; in Figure 5d): This mode begins when power switch S1 turns off at t3. The diode DB12 is forward-biased and coupled inductors LB11 and LB12 provide energy to capacitor CDS1. The coupled-inductor current iLB11 linearly decreases from its peak level, and can be given by:
i L B 11 ( t ) = V D C 2 L B 11 ( t t 3 ) ,
where VDC is the voltage of the DC bus capacitor CDC.
Capacitors CDC and CDS2 and resonant inductor Lr continue providing energy to capacitors CDS1, Cr and Co and to the LED through diodes Do1 and Do4. When the drain-source voltage vDS2 of S2 decreases to zero at t4, this mode ends.
Mode 5 (t4t < t5; in Figure 5e): The body diode of switch S2 is forward-biased at time t4, and this mode begins. The resonant inductor Lr provides energy to capacitors CDS2, Cr and Co and to the LED through the body diode of power switch S2 and diodes Do1 and Do4. The diode DB12 is forward-biased and coupled inductors LB11 and LB12 provide energy to capacitor CDS1 through diode DB12. At time t5, the drain-source voltage vDS2 of power switch S2 is zero and S2 turns on with ZVS; then this mode ends.
Mode 6 (t5t < t6; in Figure 5f): When switch S2 achieves ZVS turn-on at t5, this mode starts. The rectified input voltage source VREC2 provides energy to coupled inductor LB22 through diode DB22 and switch S2, and diode DB21 is reverse-biased during this mode. The DC bus capacitor CDC and resonant capacitor Cr provide energy to inductor Lr, capacitors CDS1 and Co and to the LED through diodes Do2 and Do3. Coupled inductors LB11 and LB12 continue providing energy to capacitor CDS1 through diode DB12. This mode ends when current iLB11 decreases to zero at t6.
Mode 7 (t6t < t7; in Figure 5g): Voltage source VREC2 continues providing energy to coupled inductor LB22 through diode DB22 and switch S2. The resonant capacitor Cr provides energy to resonant inductor Lr, output capacitor Co and the LED through diodes Do2 and Do3. This mode ends when diode DB21 is forward-biased at t7.
Mode 8 (t7t < t8; in Figure 5h): This mode begins when power switch S2 turns off at t7. The diode DB21 is forward-biased and coupled inductors LB21 and LB22 provide energy to capacitor CDS2. The resonant capacitor Cr continues providing energy to resonant inductor Lr, capacitors CDS2 and Co and to the LED through diodes Do2 and Do3. When the drain-source voltage vDS1 of S1 decreases to zero at t8, this mode ends. Then Mode 1 begins for the next high-frequency switching period.

3. Design Equations of Key Circuit Components in the Presented LED Driver

3.1. Design of Coupled Inductors LB11, LB12, LB21 and LB22

The coupled inductors (LB11 and LB12; LB21 and LB22) are designed to be operated in DCM for naturally achieving PFC, and the design equation of them can be expressed as follows [12,20]:
L B 11 = L B 12 = L B 21 = L B 22 = η v a c p k 2 D 2 4 f s P o ,
where Vac-pk is the peak value of utility-line voltage; η is the estimated efficiency; D is the duty cycle of the power switches; fs is the switching frequency; and Po is the output rated power.
In reference to Equation (4) with a η of 0.85, a Vac-pk of 220 2 V, a D of 0.45, a Po of 165 W and an fs of 50 kHz, the coupled inductors LB11, LB12, LB21 and LB22 are given by:
L B 11 = L B 12 = L B 21 = L B 22 = 0.85 ( 220 2 ) 2 0.45 2 4 50 k 165 = 505 μ H

3.2. Design of Resonant Inductor Lr and Resonant Capacitor Cr

In reference to Figure 2b, the resonant frequency fr is given by:
f r = 1 2 π L r C r .
The switching frequency fs is designed to be larger than the resonant frequency fr so that the resonant tank resembles an inductive network in order to obtain ZVS on for the two power switches [21]. The relationship between the switching frequency fs and the resonant frequency fr is selected as:
f s = 4 f r .
The quality factor Qr is defined as:
Q r = L r R a C r ,
where Ra is the equivalent output resistor referring to the left side of the full-bridge rectifier, and could be expressed by the following equation:
R a = 8 V o π 2 I o .
Combining Equation (2) with Equations (3)–(5), the design equations of resonant capacitor Cr and inductor Lr are given by:
C r = 2 R a Q L f s ,
and
L r = 4 π 2 f s 2 C r .
According to Equation (8), with a Vo of 235 V and an Io of 700 mA, the equivalent resistor Ra is given by:
R a = 8 235 π 2 700 m = 272.1 Ω .
In reference to Equation (9), with an Ra of 272.1Ω, the relationship between the resonant capacitor Cr and the switching frequency under different levels of quality factor Qr is shown in Figure 7. With a Qr of 0.15 and a switching frequency fs of 50 kHz, the capacitor Cr is selected to be 1.22 μF according to Figure 7.
In reference to Equation (10), with a Cr of 1.22 μF, the resonant inductor Lr is given by:
L r = 4 π 2 ( 50 k ) 2 1.22 μ = 133 μ H .

3.3. Design of Input Low-Pass Filter

The input low-pass filter is composed of an inductor Lf and a capacitor Cf, and the cut-off frequency of the input low-pass filter is given by:
f c u t o f f = 1 2 π L f C f .
The design consideration of the cut-off frequency in the input low-pass filter is determined to be one-tenth of the switching frequency (which is 5 kHz) in order to filter the high-frequency switching noises. The design equation of the inductor Lf is represented by:
L f = 1 4 π 2 f c u t o f f 2 C f .
On choosing a capacitor Cf of 2 μF (two capacitors of 1 μF in parallel connection), the inductor Lf is given by:
L f = 1 4 π 2 f c u t o f f 2 C f = 1 4 π 2 ( 5 k H z ) 2 2 μ F = 2.5 m H .

4. Experimental Results

A prototype driver has been successfully implemented and tested for powering a 165 W-rated LED streetlight module (LMD003 from AcBel Polytech Inc., New Taipei City, Taiwan) with input utility-line voltages of 220 V ± 5% (from 210 to 230 V). Table 1 and Table 2 show the specifications and key components utilized in the presented single-stage LED driver for streetlight applications, respectively.
The measured waveforms of coupled inductor currents iLB11 and iLB22 are shown in Figure 8; both of which have interleaved features and operate in DCM. Figure 9 shows the measured switch voltage vDS1 and current iDS1; Figure 10 presents the measured switch voltage vDS2 and current iDS2; thus, ZVS occurred on both switches for lowering the switching losses.
Figure 11 presents the measured switch voltage vDS2 and resonant inductor current iLr. The current iLr lags with respect to voltage vDS2 so that the series resonant tank resembles an inductive load. Figure 12 depicts the measured output voltage VO and current IO; their average values are approximately 235 V and 0.7 A, respectively. Figure 13 shows measured voltages on the diodes DB11 and DB22. The voltage spikes on DB11 and DB22 are approximately 360 V. In addition, the voltage rating of the diode (C3D10060) is 600 V. Therefore, the utilized diodes are capable of sustaining these voltage spikes. The measured waveforms of input utility-line voltage vAC and current iAC are shown in Figure 14, and the input current is in phase with utility-line voltage, which results in high power factor. In addition, experimental waveforms from Figure 8 to Figure 14 are measured at a utility-line voltage of 220 V.
Figure 15 shows the measured input utility-line current harmonics comparing with the International Electrotechnical Commission (IEC) 61000-3-2 Class C standards at input utility-line voltages ranging from 210 to 230 V, and all current harmonics meet the requirements. Table 3 shows the measured output voltage ripple and current ripple of the presented LED streetlight driver among input voltages ranging from 210 to 230 V; additionally, the output voltage (current) ripple is obtained by the peak-to-peak level divided by the average value of output voltage (current). According to this table, the measured output voltage ripples and current ripples are smaller than 1% and 10%, respectively, during the tested input voltages.
Figure 16 presents the measured power factor and current total-harmonics distortion (THD) of the presented LED driver under utility-line voltages ranging from 210 to 230 V. At a utility-line rms voltage of 220 V, the measured power factor and current THD are 0.992 and 6.55%, respectively. In addition, the measured highest power factor and lowest current THD are 0.993 and 6.5%; these occurred at a utility-line rms voltage of 230 and 210 V, respectively. Figure 17 shows the measured circuit efficiency of the presented LED driver under utility-line voltages ranging from 210 to 230 V; additionally, the measured maximum circuit efficiency is 91.23%, at a utility-line rms voltage of 210 V. In addition, the efficiency which drops with the increase utility-line voltages is related to the voltage gain of the LC series resonant tank. For providing rated output power (voltage/current), the voltage gain of the LC series resonant tank will decrease when the utility-line voltages increase, resulting in an increase in the switching frequency of the power switches. Thus, the switching losses of power switches and conduction losses of power diodes will increase, resulting in lowered circuit efficiency. Figure 18 presents a photograph of supply of the experimental LED streetlight module using the presented driver at a utility-line voltage of 220 V.
Besides, Table 4 shows some measurements of the relationship between output voltage, efficiency and output load current under an input utility-line voltage of 220 V by altering the equivalent load resistor to represent the specific load current. In addition, the measured minimum efficiency is 86.51%, in a minimum load current of 0.3 A. Moreover, Table 5 shows comparisons between the existing single-stage LED driver for streetlight applications in [18] and the proposed one. From Table 5, it can be seen that the proposed LED streetlight driver has better current THD and efficiency than the existing one.

5. Conclusions

This paper has presented and implemented a single-stage LED driver with a high power factor which is suitable for streetlight applications and integrates an interleaved buck-boost PFC converter with coupled inductors and a half-bridge-type series-resonant converter cascaded with a full-bridge rectifier into a single power conversion stage. A 165-W prototype LED driver has been developed and tested with input utility-line voltages ranging from 210 to 230 V. The experimental results of the presented LED driver display low-output voltage ripple (<1%) and output current ripple (<10%), high power factor (>0.99), low total harmonic distortion of input utility-line current (<7%), zero-voltage switching on power switches, and high circuit efficiency (>90%); thus the functionality of the presented LED streetlight driver is demonstrated.

Acknowledgments

The authors would like to convey their appreciation for grant support from the Ministry of Science and Technology (MOST) of Taiwan under its grant with reference number MOST 104-2221-E-214-012.

Author Contributions

Chun-An Cheng and Chien-Hsuan Chang conceived and designed the circuit; Hung-Liang Cheng performed circuit simulations; Ching-Hsien Tseng and Tsung-Yuan Chung carried out the prototype driver, and measured as well as analyzed experimental results with the guidance from Chun-An Cheng; Hung-Liang Cheng revised the manuscript for submission.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. The conventional two-stage light-emitting diode (LED) driver for streetlighting applications, PFC: power factor correction.
Figure 1. The conventional two-stage light-emitting diode (LED) driver for streetlighting applications, PFC: power factor correction.
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Figure 2. (a) Original two-stage LED driver circuit; (b) the presented single-stage LED driver with coupled inductors and interleaved PFC for streetlight applications.
Figure 2. (a) Original two-stage LED driver circuit; (b) the presented single-stage LED driver with coupled inductors and interleaved PFC for streetlight applications.
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Figure 3. The utilized control circuit of the presented single-stage LED driver for streetlight applications.
Figure 3. The utilized control circuit of the presented single-stage LED driver for streetlight applications.
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Figure 4. Simplified circuit of the presented single-stage LED driver for streetlight applications.
Figure 4. Simplified circuit of the presented single-stage LED driver for streetlight applications.
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Figure 5. Operation modes of the presented LED driver; (a) Model 1; (b) Model 2; (c) Model 3; (d) Model 4; (e) Model 5; (f) Model 6; (g) Model 7; (h) Model 8.
Figure 5. Operation modes of the presented LED driver; (a) Model 1; (b) Model 2; (c) Model 3; (d) Model 4; (e) Model 5; (f) Model 6; (g) Model 7; (h) Model 8.
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Figure 6. Key waveforms of the presented LED driver for streetlight applications.
Figure 6. Key waveforms of the presented LED driver for streetlight applications.
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Figure 7. Resonant capacitor Cr versus the switching frequency fs under different levels of quality factor Qr.
Figure 7. Resonant capacitor Cr versus the switching frequency fs under different levels of quality factor Qr.
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Figure 8. Measured coupled inductor currents iLB11 (2 A/div) and iLB22 (2 A/div); time scale: 5 μs/div.
Figure 8. Measured coupled inductor currents iLB11 (2 A/div) and iLB22 (2 A/div); time scale: 5 μs/div.
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Figure 9. Measured switch voltage vDS1 (200 V/div) and current iDS1 (2 A/div); time scale: 5 μs/div.
Figure 9. Measured switch voltage vDS1 (200 V/div) and current iDS1 (2 A/div); time scale: 5 μs/div.
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Figure 10. Measured switch voltage vDS2 (200 V/div) and current iDS2 (2 A/div); time scale: 5 μs/div.
Figure 10. Measured switch voltage vDS2 (200 V/div) and current iDS2 (2 A/div); time scale: 5 μs/div.
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Figure 11. Measured switch voltage vDS2 (200 V/div) and resonant inducotr current iLr (2 A/div); time scale: 5 μs/div.
Figure 11. Measured switch voltage vDS2 (200 V/div) and resonant inducotr current iLr (2 A/div); time scale: 5 μs/div.
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Figure 12. Measured output current IO (0.5 A/div) and voltage VO (100 V/div); time scale: 2 ms/div.
Figure 12. Measured output current IO (0.5 A/div) and voltage VO (100 V/div); time scale: 2 ms/div.
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Figure 13. Measured voltages on the diodes DB11 and DB22. Voltage scale: 200 V/div; time scale: 5 μs/div.
Figure 13. Measured voltages on the diodes DB11 and DB22. Voltage scale: 200 V/div; time scale: 5 μs/div.
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Figure 14. Measured input utility-line voltage vAC (200 V/div) and current iAC (2 A/div); time scale: 5 ms/div.
Figure 14. Measured input utility-line voltage vAC (200 V/div) and current iAC (2 A/div); time scale: 5 ms/div.
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Figure 15. Measured input current harmonics compared with the IEC 61000-3-2 Class C standards.
Figure 15. Measured input current harmonics compared with the IEC 61000-3-2 Class C standards.
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Figure 16. Measured power factor and current total harmonic distortion (THD) under utility-line voltages ranging from 210 to 230 V.
Figure 16. Measured power factor and current total harmonic distortion (THD) under utility-line voltages ranging from 210 to 230 V.
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Figure 17. Measured circuit efficiency under utility-line voltages ranging from 210 to 230 V.
Figure 17. Measured circuit efficiency under utility-line voltages ranging from 210 to 230 V.
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Figure 18. Photograph of supply of the experimental LED streetlight module using the presented driver at a utility-line voltage of 220 V, AC: Alternating-Current.
Figure 18. Photograph of supply of the experimental LED streetlight module using the presented driver at a utility-line voltage of 220 V, AC: Alternating-Current.
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Table 1. Specifications of the presented single-stage LED driver.
Table 1. Specifications of the presented single-stage LED driver.
ParameterValue
Input Utility-Line Voltage vAC220 V ± 5% (rms)
Output Rated Power PO165 W
Output Rated Voltage VO235 V
Output Rated Current IO700 mA
Table 2. Key components utilized in the presented LED driver.
Table 2. Key components utilized in the presented LED driver.
ComponentValue
Capacitors Cin1, Cin2330 nF Component
Inductors LB11, LB12, LB21, LB22505 μH
Diodes DB11, DB12, DB21, DB22C3D10060
Power Switches S1, S2STP20NM60
DC-Linked Capacitor CDC100 μF/450 V
Resonant Inductor Lr133 μH
Resonant Capacitor Cr1.22 μF
Diodes Do1, Do2, D03, D04MUR460
Output Capacitor Co220 μF/400 V
Filter Inductor Lf2.5 mH
Filter Capacitor Cf2 μF
Table 3. Measured output voltage ripple and current ripple in the presented LED streetlight driver.
Table 3. Measured output voltage ripple and current ripple in the presented LED streetlight driver.
Input Voltage (rms)Voltage Ripple (%)Current Ripple (%)
210 V0.759.14
215 V0.759.73
220 V0.799.28
225 V0.759
230 V0.838.99
Table 4. Measured output voltage and efficiency versus output load current under an input utility-line voltage of 220 V.
Table 4. Measured output voltage and efficiency versus output load current under an input utility-line voltage of 220 V.
Output Load Current0.7 A0.6 A0.5 A0.4 A0.3 A
Equivalent Load Resistor336 Ω392 Ω470 Ω588 Ω783 Ω
Measured Output Voltage235.31 V234.91 V235.31 V234.86 V235.34 V
Measured Efficiency90.22%89.39%87.82%86.59%86.51%
Table 5. Comparisons between the existing single-stage LED driver for streetlight applications in [18] and the proposed one.
Table 5. Comparisons between the existing single-stage LED driver for streetlight applications in [18] and the proposed one.
ItemPresented LED Driver in [18]Proposed LED Driver
Circuit topologySingle-stage (integrating a interleaved boost PFC converter with a half-bridge LLC resonant converter)Single-stage (integrating a interleaved buck-boost PFC converter with coupled inductors and a half-bridge-type series-resonant converter cascaded with a full-bridge rectifier)
Operating in Utility-Line Voltage Range90~130 V210~230 V
Output Rated Power144 W (36 V/4 A)165 W (235 V/0.7 A)
Power Switches2 (S1, S2)2 (S1, S2)
Diodes8 (D1~D6, DB1, DB2)12 (Dr1~Dr4, DB11~DB22, Do1~Do4)
Capacitors6 (Cf, Cin1, Cin2, CB, Cr, Co)6 (Cf, Cin1, Cin2, CDC, Cr, Co)
Inductors4 (Lf, LB1, LB2, Lr)4 (Lf, LB11 and LB12, LB21 and LB22, Lr)
Transformer1 (with a magnetic inductor Lm)0
Measured power factor0.99 (at 110 V)0.992 (at 220 V)
Measured current THD10% (at 110 V)6.55% (at 220 V)
Measured efficiency88% (at 110 V)90.22% (at 220 V)

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MDPI and ACS Style

Cheng, C.-A.; Chang, C.-H.; Cheng, H.-L.; Tseng, C.-H.; Chung, T.-Y. A Single-Stage High-Power-Factor Light-Emitting Diode (LED) Driver with Coupled Inductors for Streetlight Applications. Appl. Sci. 2017, 7, 167. https://doi.org/10.3390/app7020167

AMA Style

Cheng C-A, Chang C-H, Cheng H-L, Tseng C-H, Chung T-Y. A Single-Stage High-Power-Factor Light-Emitting Diode (LED) Driver with Coupled Inductors for Streetlight Applications. Applied Sciences. 2017; 7(2):167. https://doi.org/10.3390/app7020167

Chicago/Turabian Style

Cheng, Chun-An, Chien-Hsuan Chang, Hung-Liang Cheng, Ching-Hsien Tseng, and Tsung-Yuan Chung. 2017. "A Single-Stage High-Power-Factor Light-Emitting Diode (LED) Driver with Coupled Inductors for Streetlight Applications" Applied Sciences 7, no. 2: 167. https://doi.org/10.3390/app7020167

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