LED Based Track Lighting System San Jose State University Senior Project

1. LED Based Track Lighting SystemSan Jose State University Senior Project Senior Design Project Team John Kmiec John Pipitone Project Advisor Dr. Lili He

2. Acknowledgements • iWatt Corporation • Technical assistance • Converter Evaluation Boards • Components, Lab Space, and Test Equipment • Lumileds Lighting Incorporated • Technical assistance • LEDs

3. LED Based Track Lighting SystemSystem Configuration • 120 WATT SWITCHING FLYBACK CONVERTER • INPUT: 120VAC, 60Hz • OUTPUT: Capable of 120 Watts, +24VDC @ 5 Amps • Switching frequency is approximately 100KHz • 2 LED HEADS • INPUT: +24VDC, approximately 2.1 Amps per LED Head • OUTPUT: Approximately 800 Lumens per LED Head 1600 Lumens total • 9 LEDs per head • Each head has a copper heat sink, and is fan cooled • DESIGN MARGIN • Approximately 20 Watts margin • Approximately 1 Amp margin

4. COMPARISION OF LIGHTING SYSTEMS Halogen Lighting System 2 Lamp, 2 Head system, 120 Watts required, with 2320 Lumen output 90 Watts required, with 1060 Lumen output Flyback Converter with 2 LED Heads 110 Watts required, with 1600 Lumen minimum output Track Voltage +24VDC @ 5 Amps 120 Watt Flyback AC to DC Converter 2 LED Heads 9 LEDs per Head Approximately 800 Lumens/Head LED Based Track Lighting SystemSystem Configuration

5. LED Based Track Lighting SystemSystem Design • 120 WATT FLYBACK SWITCHING CONVERTER • Copper-plane prototype failed. (parasitic losses) • iWatt 70 Watt evaluation PCB, redesigned for 120Watts • Transformer design • Split Primary, Dual secondary, sense for the PWM circuit • Ferrites, bobbin, wire type and gauge, number of turns • Switcher design • Efficiency • Component losses • Voltage and current ratings • PWM scaling • LED HEADS • Buck-Boost Converter was not required • Op-Amps drive 3 LEDs in series (9 LEDs per head) • Copper heat-sink • Fan Cooled

6. PRIMARY SECONDARY Pin 1 Pin 12 4 Turns 10 Turns Pin 2 (Not used) Pin 9 Pin 11 10 Turns 4 Turns Pin 3 Pin 8 Pin 5 2 Turns Pin 6 LED Based Track Lighting SystemTransformer Design • SECTION START STOP ½ Primary Pin 3 Pin 2 Secondary Pin 6 Pin 5 Secondary Pin 11, 12 Pin 8, 9 ½ Primary Pin 2 Pin 1 • WIRE CRITERIA Primary = 1.4A average current Aux = 7mA 0.5 turns But for practical functionality, it should be 2 turns minimum. So, make each split-secondary 4 turns, and the Primary 20 turns total. Secondary #1 = 2.5A average Secondary #2 = 2.5A average

7. Primary #2 2 Layers of Kapton Split Secondary 2 Layers of Kapton Sense Layer 1 Layer of Kapton Primary #1 LED Based Track Lighting SystemTransformer Design • BOBBIN and WIRE GAUGE • BOBBIN • Approximately 85% full of wire, so it grabs the Ferrite Core surrounding • Approximately 10% filled with Kapton tape, copper Sense turns • WIRE GAUGE • Based on Bobbin fill and Current requirements • 20AWG Solid Magnet Wire for both halves of the Split-Primary • 120/38 SPN (AWG/Number of Strands) of Litz Wire for the Dual Secondary

8. Converter Performance

9. LED Based Track Lighting SystemLED Head Design • SINGLE LED HEAD • 9 LEDs per head • LEDs Require Electrical Isolation • JC = 8 C/Watt • Max slug temperature is 95C • Light Flux Density Values Based on Data Sheet • LED Driver is Constant Current • Amplifier is thermally protected

10. Lamp Performance Lumen Efficiency LEDs vs. Halogen

11. Summary • 2320 Lumens for 120W Halogen system, 1060 for 90W system • 1573 Lumens Minimum LED flux, 2160 Lumens Typical • For Halogen systems • 11.77 Lumens/Watt for 90W system • 19.33 Lumens/Watt for 120W system • For LED system • 11.9 Lumens/Watt Based on Minimum Flux Spec • 16.36 Lumens/Watt Based on Typical Flux Spec • Converter efficiency and lamp design losses considered • By using a newer converter controller chip and redesigning the lamp to use one driver amplifier per lamp the Halogen system efficiency can be easily beat