GRD Journals- Global Research and Development Journal for Engineering | Volume 2 | Issue 4 | March 2017 ISSN: 2455-5703
AC-DC Flyback Converter For Outdoor Led Lighting Swati S. Kunkolkar M.E Student Department of Electrical and Electronics Engineering Goa College of Engineering, Farmagudi
Dr. V.N Shet Professor Department of Electrical and Electronics Engineering Goa College of Engineering, Farmagudi
Abstract An AC-DC flyback converter for outdoor LED lighting is proposed. In the proposed converter is designed to be operated in the discontinuous-conduction mode (DCM) to achieve a high power factor. A DC-DC flyback module is designed to provide inputoutput electrical isolation. This improves safety. In addition to this, a low-voltage-rating capacitor can be used as the DC-bus. PSIM based simulations are carried out. This paper addresses a novel approach for designing and modeling of the isolated flyback converter. A detailed analysis and simulation are conferred for flyback converter in discontinuous conduction mode (DCM). Keywords- LED (light emitting diode), interleaved flyback, PFC (power factor correction), THD (Total harmonic distortion), Design, Analysis and result
I. INTRODUCTION LEDs are widely used in wide range of applications (Street lights, beacon lights, flood lights etc…). These applications require around 10W- 200W power. An interleaved flyback (Fig.2) converter is designed for 170Vac, 50Hz input to get 90V, 81W output. Fly-back converter is the most commonly used SMPS circuit for low output power applications where the output voltage needs to be isolated from the input main supply. The output power of fly-back type SMPS circuits may vary from few watts to less than 100 watts. The overall circuit topology of this converter is considerably simpler than other SMPS circuits. Input to the circuit is generally unregulated dc voltage obtained by rectifying the utility ac voltage followed by a simple capacitor filter. The circuit can offer single or multiple isolated output voltages and can operate over wide range of input voltage variation. In respect of energy-efficiency, fly-back power supplies are inferior to many other SMPS circuits but it’s simple topology and low cost makes it popular in low output power range. A.
Advantages of Interleaved Flyback Converter Reduced transformer and semiconductor peak currents Reduced transformer and semiconductor RMS currents Reduced input and output capacitor RMS currents Reduction of EMI energy due to lower peak currents Distribution of heat generating elements
B.
Disadvantages of Interleaved Flyback Converter Increased component count Possible increase in component area Control complexity of interleaved drive signals for Dmax greater than 50%
II. PROPOSED SYSTEM The single phase AC supply is fed to the EMI filter. EMI filter filters out the noises. The output of EMI filter is fed to the rectifier. Rectifier converts it to DC. The rectifier output is then fed to the interleaved flyback converter. The flyback converter is controlled by pulse width modulation. The regulated dc output is then fed to the LED string. Fig. 1 shows the block diagram
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AC-DC Flyback Converter For Outdoor Led Lighting (GRDJE/ Volume 2 / Issue 4 / 014)
Fig. 1: Block diagram of proposed system
III. PROPOSED CONTROL METHOD In proposed method discontinuous mode of operation is adopted. This means there will be time delay between turn ON and turning OFF of the switching devices as a result the stress on switching devices will be less and hence efficiency will be more. The sinusoidal pulse width modulation technique is used to control the MOSFET in the flyback converter. In sinusoidal pulse width modulation, triangular wave is the carrier signal and the sine wave is the reference signal. The gating pulses are generated by comparing the reference signal with the carrier wave. This method reduces the power loss in switching device. Fig. 3 shows the PWM signals that are fed to the MOSFET switches Q1 and Q2
Fig. 2: Interleaved Flyback converter
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AC-DC Flyback Converter For Outdoor Led Lighting (GRDJE/ Volume 2 / Issue 4 / 014)
IV. OPERATING PRINCIPLE Following assumptions are made for designing an interleaved flyback converter (Fig. 2). A. Assumptions 1) Transformer leakage inductances are negligible. 2) EMI filter is larger than input capacitance. 3) The magnetizing inductances Lm1 and Lm2 are identical. 4) There is 180deg phase shift between the two switches. There are 6 modes of operation. 1) Mode 1 In mode 1 Q1 is ON and Q2 OFF. Energy is built into the magnetizing inductor Lm1. The energy stored in the inductor Lm2 is transferred to the output through the Diode D6. The diode current ID6 decreases. 2) Mode 2 When diode current ID6 decreases to zero this mode begins. Q1 is ON, the diodes D1 and D4 conduct. The output capacitor Co discharges and the load gets power. 3) Mode 3 When Q1 Is turned OFF, this mode begins. Energy stored in Lm1 is transferred to output Via D5 which is forward biased at that time. This modes ends when ID5 decreases to zero. Other three modes of operation are same as the first three modes.
Fig. 3: (A) Input waveforms for interleaved flyback converter, (B) Q1 power switch ON and OFF times, (C) Q2 switch ON and OFF times
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AC-DC Flyback Converter For Outdoor Led Lighting (GRDJE/ Volume 2 / Issue 4 / 014)
V. DESIGN Table 1: Design requirement Symbols Values minimum input voltage Vimin 170Vac maximum input voltage Vimax 270Vac maximum output voltage maximum output current window utilization switching frequency converter efficiency
Vomax Iomax Ku Fs n
90 0.9A 0.29 25KHz 90%
maximum duty ratio
Dmax
0.5
Dwell time duty ratio
Dw
0.1
regulation
Îą
1.0 %
operating flux density
Bm
0.25
Diode voltage
Vd
1.0
VI. SIMULATION
Fig. 4: Psim model of AC-DC flyback converter
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AC-DC Flyback Converter For Outdoor Led Lighting (GRDJE/ Volume 2 / Issue 4 / 014)
Fig. 5: PWM signals fed to MOSFET switches
Fig. 6: Output current and Voltages
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AC-DC Flyback Converter For Outdoor Led Lighting (GRDJE/ Volume 2 / Issue 4 / 014)
Table 2: Simulation parameters Parameters Values Vin 170-270Vac Vo 90Vdc Io 0.9A Cin 230µF Co 910 µF Magnetisin inductance Lm1=Lm2 510mH Output resistance 100Ω THD 2% PF 0.62
VII. CONCLUSION An LED driver is presented. This proposed converter provides regulated output with very low ripple content. In closed loop we get 2% THD and 0.62 power factor. Hence an interleaved single-stage flyback ac-dc converter operating in the DCM mode is an appropriate choice for wide output range LED applications.
ACKNOWLEDGEMENT The author would like to thank her guide Prof. V.N. Shet for his support and insights in the subject.
REFERENCES [1] [2] [3] [4] [5] [6] [7]
G. S. Sandhya. K, "An Interleaved Single-Stage Fly Back AC-DC converter for outdoor LED lighting," International Journal of Engineering Research & Technology, vol. 3, no. 3, pp. 1679-1683, March 2014. S.-W. L. a. H.-L. Do, "A Single-Switch AC-DC LED Driver Based on a Boost-Flyback PFC Converter with Lossless Snubber," IEEE transaction on power electronics, vol. 32, no. 2, pp. 1375-1384, 2017. A. A. Saliva, "Design Guide for Off-line Fixed Frequeny DCM Flyback Converter," january 2013. G.-B. K. G.-W. M. SangCheol Moon, "An Interleaved Single-Stage Flyback AC-DC Converter with Wide Output Power Range for Outdoor LED Lighting System," in Applied Power Electronics conference and exposition,2012 Twenty-seventh Annual IEEE, 2012. www.fairchildsemi.com C.W.T. McLyman, Tarnsformer and inductor Design Handbook. Brian Shaffer, Interleaving Contributes Unique Benefits to Forward Converters.
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