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

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

LED Based Track Lighting System System Configuration 120 WATT SWITCHING FLYBACK CONVERTER –INPUT: 120VAC, 60Hz –OUTPUT: Capable of 120 Watts, 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

LED Based Track Lighting System System Configuration 2 LED Heads 9 LEDs per Head Approximately 800 Lumens/Head 120 Watt Flyback AC to DC Converter Track Voltage 5 Amps 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

LED Based Track Lighting System System 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

LED Based Track Lighting System Transformer Design SECTIONSTARTSTOP ½ PrimaryPin 3Pin 2 SecondaryPin 6Pin 5 SecondaryPin 11, 12Pin 8, 9 ½ PrimaryPin 2Pin 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 PRIMARYSECONDARY 10 Turns 4 Turns Pin 12 Pin 8 Pin 1 Pin 2 (Not used) Pin 3 Pin 11 Pin 9 Pin 6 Pin 5 2 Turns

LED Based Track Lighting System Transformer Design Primary #1 Primary #2 Split Secondary 1 Layer of Kapton 2 Layers of Kapton Sense Layer 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

Converter Performance

LED Based Track Lighting System LED 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

Lamp Performance Lumen Efficiency LEDs vs. Halogen Min Led Flux Fixture Total Typ Led Flux Fixture Total Philips 45W PAR  Flood X2 Philips 60W PAR  Flood X2 Lumens Lumens/Watt

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