WEBENCH LED Tools Jeff Perry WEBENCH Manager 1

WEBENCH LED Tools Jeff Perry WEBENCH Manager 1

Objectives WEBENCH Update LED selection parameters How to Use WEBENCH® LED Architect for LED and LED Driver Selection Hands on examples 2

LED Drivers in WEBENCH Buck Integrated Buck Controller Boost/Buck-Boost AC • LM 3402/4(HV) • LM 3401 • LM 3410 X/Y • LM 3444 • LM 3405(A) • LM 3409(HV) • LM 3421/23 • LM 3445 • LM 3406 (HV) • LM 3433 • LM 3424 • LM 3464 • LM 3407 • LM 3434 • LM 3429 • LM 3464 A • LM 3414(HV) • LM 3431 (multiple) 3

LED Selection Parameters

Explosion of Applications for LEDs General Illumination: • • • Automotive: Architectural Residential Industrial Portable Consumer Outdoor Area Projectors & Copiers Entertainment Lighting Retail Display Medical Emergency/Safety Lighting Signs and Channel Lettering • • Headlights RCL CHMSL Interior Lighting Instrument Panel Infotainment Backlighting Aviation, Marine, and Rail • Crash Avoidance • Instrument Panel • Interior Lighting Backlighting & Projection: Mobile Devices: • • • Display backlighting • Camera flash 5 Infotainment Large format TV displays Laptops Pocket & Data Projectors

Quantifying Light From LEDs Luminous Flux (Lumens) Luminosity Function 6

LED Color – Dominant Wavelength Sampling of color LEDs Blue Cyan Orange Green Yellow/ Amber 7 Red

White LEDs – Color Temperature Sampling of white LEDs Incandescent Bulb Daylight Red Tint Blue Tint Warm White 8 Cool White

Luminous Flux – Comparison Chart Application Brightness (lumens) 40 W tungsten bulb 500 100 W tungsten bulb 1, 500 25 W compact fluorescent 1, 500 55 W halogen auto headlight 1, 500 35 W high intensity discharge auto headlight 3, 250 150 W halogen projector bulb 5, 000 150 W high pressure sodium bulb 16, 000 9

Luminous Efficacy • Measure of the efficiency of the lighting source (lumens/watt) • Can be for the LED only or LED + Driver (system luminous efficacy • Increasing efficacy = lower cost 10

Luminous Flux for LEDs Sampling of. 35 A cool white LEDs: Most efficient 140 100 Lumens Flux 0 Power 11 1. 2

WEBENCH® LED Architect Overview of the NEW Webench tool

A Groundbreaking New Tool • First of it’s kind on the market • System level approach • Saves time in LED lighting system design 13

WEBENCH® LED Architect Overview 1. Select LED & Driver 2. Analyze & Optimize 3. Simulate 4. Build It 14

How to Access WEBENCH® LED Architect • Use the entry panel on www. osram. national. com 15

Behavior of LEDs Is Dynamic • Light output increases vs current • Light output decreases vs temperature • Efficacy decreases vs current • Vf increases vs current • Need to model these behaviors to give true light output • Tradeoffs: – High current = more light = fewer LEDs – High current = higher temperature = less light/shorter lifetime = bigger heat sink – High current = lower efficacy = no Energy Star approval 16

Can You Drive a. 35 A LED At. 5 A? And Why? • LED datasheets typically rate LEDs at a nominal current – Luminous Flux – Efficacy • 1 W LED is usually. 35 A nominal current – Lower current = higher efficacy • The LED can be driven at a higher current which increases the light output per LED – Fewer LEDs may be required • But: – Temperature goes up – Efficacy goes down 17

Luminous Flux Increases With Current 125% 100% . 35 A Nominal LED can be driven at. 5 A to get 25% more luminous flux. This reduces the number of LEDs required 18

Luminous Flux Decreases With Temperature 92% 70% 50 C 125 C Luminous flux reduces to 70% of nominal at 125 C. This means big heat sinks are needed 19

Heat Sinks Are Required • LEDs generate a lot of heat • Total luminous efficiency of LEDs is only 4% to 22% – Total visible light/input power Thermal vias 15% of power converted to light LED Heat sink 85% converted to heat 20

Efficacy Decreases With Current Theoretical maximum efficacy for neutral white is 336 lumens/watt Decreased efficacy = no Energy Star certification 21

Initial Input Panel Enter parameters here 22

Enter LED Requirements Enter: 1) Input voltage 2) Ambient temperature 3) Desired light output 4) LED color Advanced inputs 23

Advanced inputs Max Vout Parallel strings on 1 driver Max heat sink dimensions Manufacturer Max junction temperature 24

Step 1: Choose The Ideal LED Solution LEDs and heat sink required to give the desired light output 25

Detailed LED Performance • Click on the details button to get LED performance • Why does the flux go down with increasing current? 26

Footprint of HS (cm 2) Visualize the LED choices What is best for the goals? 100 Bubble size = cost 70 64 78 Efficacy (lumens/watt) 27

Optimize the LED Solution Optimization knob 1 = Smallest footprint 2 = Lowest cost 3 = Balanced 4 = Higher efficacy 5 = Highest efficacy 28

Example Range of LED Options for 1300 Lumens Optimization Heat Sink Size Efficacy Cost Temp 77 L/W $44. 45 115 C 1 12 LEDs 25 cm 2 5. 2 C/W 2 8 LEDs 58 cm 2 3. 1 C/W 63 L/W $30. 55 114 C 5 13 LEDs 1144 cm 2. 69 C/W 97 L/W $74. 16 Osram Oslon LUW CP 7 PKTLP 5 C 8 E 29 48 C

Hands On Exercise Design Problem: Goals: Source: 24 – 32 V Light output: 2000 lumens Neutral white LED Maximum string voltage: 60 V No parallel LEDs on a single driver allowed What is the LED and heat sink combination with the: Smallest footprint Highest luminous efficacy Lowest cost Note the following: 1) LED manufacturer 2) LED part number 3) # LEDs 4) Heat sink theta. SA 5) LED current 30

LED Arrays – Parallel vs Serial • In order to get the desired amount of light, LEDs must be combined. – Parallel: • Keeps total Vf low – good for buck driver topology • But Vf of each LED may not be the same, so some LEDs may get higher current/brightness/temperature – Series: • No problem with differences in current and thus brightness/ • But, Vf adds up. If exceeds Vin. Min, then need to use Boost topology driver 31

Driving The LED – Switching Regulator Topology • Buck (Step Down): – Simple – Lowest current requirements – Requires high input voltage (Vin. Min > Vled) • Boost (Step Up): – Well known topology – Requires high current (Vin*In = Vout*Iout/Efficiency) • Ex: Vin: 5 V, Vout: 14 V, Iout: . 35 A, Eff: 90%, – Requires Iin of 1. 1 A • Buck/Boost – More complicated/expensive but needed if Vin. Min < Vout < Vin. Max (Battery) 32

Step 2: View LED + Driver Solutions Complete solutions including: LED array Heat sink Driver(s) 33

Example Range of Driver Topology Options for 1300 Lumens, Vin = 14 -22 V Topology #LEDs Driver+Array Total Size Total Efficacy Total Cost Boost 1 x 9 88 cm 2 69 L/W $37. 14 Buck 3 x 3 91 cm 2 67 L/W $41. 62 Buck/ Boost 2 x 5 60 L/W $43. 79 94 cm 2 Osram Oslon LUW CP 7 PKTLP 5 C 8 E 34

Footprint of HS+driver (cm 2) LED System tradeoffs 106 Buck Boost 86 Buck. Boost 59 System efficacy (lumens/watt) 35 69

LEDs Dominate the Design Footprint 9 LEDs + HS Driver Size Cost 82 cm 2 $34. 24 6 cm 2 $2. 90 1300 Lumens, Optimization 3, Boost Driver 36

Create and View Design • Design Dashboard: – LED System summary – LED array – LED / heat sink display – Charts – Optimization Graphs – Bill of Materials Graphs – Simulation – Custom Design Report – Prototyping 37

Hands On Exercise Design Problem: Goals: Source: 24 – 32 V Light output: 2000 lumens Neutral white LED Maximum string voltage: 60 V No parallel LEDs on a single driver allowed What is the system (including the LEDs, heat sink and driver) with the: Smallest footprint Highest luminous efficacy Lowest cost (Note the LED array and driver topology used) 38

Creating A Custom LED Array Click on custom LED button 39

Custom LED Array Configuration • Manually change the array, heat sink, LED current • This will change the calculated light output 40

Custom LED Array Footprint • Increasing current will increase light output, but require heat sink 3) 1 A – 1435 lu 2) Lower Theta. SA – 1099 lu 1). 6 A - 1000 lu Efficacy © 2011 National Semiconductor Corporation. Confidential. 41 41

Hands On Exercise Design Problem: Goals: Customer wants more light: Source: 24 – 32 V Light output: 2000 lumens Neutral white LED Maximum string voltage: 60 V No parallel LEDs on a single driver allowed Use the custom LED array to increase the light output to 2500 lumens What is the LED and heat sink combination? Note the following: 1) Footprint 2) Luminous efficacy 3) Cost 4) LED manufacturer 5) LED part number 6) # LEDs 7) Heat sink theta. SA 8) LED current 42

Optimization – Efficiency vs Footprint Left side: Higher frequency Smaller footprint Right side: Lower frequency Lower resistance 43 43

Optimization – Power Dissipation FET Pdiss improves As freq is decreased: L Pdiss may get worse Higher L is required to maintain Vout. PP Lower frequency L = V*dt/di 44

Optimization Summary • To get high efficiency – Decrease frequency to reduce AC losses – Choose components with low resistance • To get small footprint – Increase frequency to reduce inductor size – Choose components with small footprint • Cost • These parameters are at odds with each other and need to be balanced for a designer’s needs • Tools are available to visualize tradeoffs and make it easier to get to the best solution for your design requirements 45

Why Do Electrical Simulation? • Design has already been configured for stable operation, but: • May want to verify operation under dynamic conditions • May want to further optimize the design for your requirements: – Improve transient response – Minimize output ripple – Improve loop stability 47

Simulation Controls Select sim type and start sim After sim is complete Select waveforms here Waveform viewer 48

Simulation Waveform Viewer Advanced controls Right click to delete a waveform Click and drag to zoom 49

Model Verification: Sim vs Bench LED Current Switch Voltage • Spice model verification involves taking bench data at various operating points and comparing to simulation Inductor Current 50

Example: Effect of Output Cap • Vin: 24 -32 V • Light output: 650 lumens • LED: 5 x Cree MX 6 AWT-A 1 -0000 -000 D 51 • ILED: 0. 497 A (target) • LM 3402 • What are the advantages/disadvantages of having: • 1) Standard output cap? • 2) No output cap? • 3) Smaller value output cap? • Use the WEBENCH Advanced Options to check this 51

LM 3402 with Cout Low Ripple Target Cout 52

LM 3402 with No Cout Larger L 1 No Cout 53

LM 3402 with Small Cout - 30% Ripple Target Smaller Cout 54

Compare Output Cap Options With output cap: 18 m. A ripple $1. 61, 381 mm 2, 92% 55

Compare Output Cap Options With output cap: 18 m. A ripple $1. 61, 381 mm 2, 92% No output cap: 53 m. A ripple $1. 64, 375 mm 2, 91% 56

Compare Output Cap Options With output cap: 18 m. A ripple $1. 61, 381 mm 2, 92% No output cap: 53 m. A ripple $1. 64, 375 mm 2, 91% Small output cap: 65 m. A ripple $1. 62, 362 mm 2, 92% 57

Example: Effect of PWM Dimming Frequency • Vin: 24 -32 V • Light output: 650 lumens • LED: 5 x Cree MX 6 AWT-A 1 -0000 -000 D 51 • ILED: . 497 A (target) • LM 3402 • Compare default 2 k. Hz dimming frequency to 4 k. Hz • How will this affect the circuit behavior? 58

PWM Dimming Simulation 59

PWM Dimming oscillator voltage LED Current 2 k. Hz dimming frequency 60

PWM Dimming Simulation Click on Dimming Oscillator 61

Change PWM Dimming Frequency Change pulse width Change pulse period 62

PWM Dimming Simulation 2 k. Hz dimming frequency 4 k. Hz dimming frequency 63

Hands On Exercise Design Problem: Goals: Create a design using the following: Source Voltage: 24 – 32 V Light output: 650 lumens Cool White Optimization 3 LED: 5 x Cree MX 6 AWT-A 10000 -000 D 51 LM 3402 Run a line transient simulation 1) Using the default input transient range of 24 V – 32 V, what is the LED current overshoot and undershoot? 2) Change the input transient to 26 V to 30 V. What is the LED curent overshoot and undershoot? 64

Summary LED parameters are dynamic: Environment must be taken into account WEBENCH LED Architect: Considers LED and heat sink properties Computes LED Array Provides driver configuration/topology based on size, cost, efficiency WEBENCH Design Tools save you time 65

Thank You! Try WEBENCH® LED Architect yourself : http: //www. national. com/led_architect Also FPGA Power Architect: http: //www. national. com/fpga_power_architect