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WEBENCH LED Tools Jeff Perry WEBENCH Manager 1. 2 LED selection parameters How to Use WEBENCH® LED Architect for LED and LED Driver Selection Hands on.

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Presentation on theme: "WEBENCH LED Tools Jeff Perry WEBENCH Manager 1. 2 LED selection parameters How to Use WEBENCH® LED Architect for LED and LED Driver Selection Hands on."— Presentation transcript:

1 WEBENCH LED Tools Jeff Perry WEBENCH Manager 1

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

3 3 LED Drivers in WEBENCH LM3402/4(HV) LM3405(A) LM3406 (HV) LM3407 LM3414(HV) Buck IntegratedBuck ControllerBoost/Buck-BoostAC LM3401 LM3409(HV) LM3433 LM3434 LM3410X/Y LM3421/23 LM3424 LM3429 LM3431 (multiple) LM3444 LM3445 LM3464 LM3464A

4 LED Selection Parameters

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

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

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

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

9 9 Luminous Flux – Comparison Chart ApplicationBrightness (lumens) 40W tungsten bulb500 100W tungsten bulb1,500 25W compact fluorescent1,500 55W halogen auto headlight1,500 35W high intensity discharge auto headlight3,250 150W halogen projector bulb5,000 150W high pressure sodium bulb16,000

10 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

11 11 Luminous Flux for LEDs Sampling of.35A cool white LEDs: 100 Lumens Flux Power 0 140 1.2 Most efficient

12 WEBENCH® LED Architect Overview of the NEW Webench tool

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

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

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

16 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

17 Can You Drive a.35A LED At.5A? And Why? LED datasheets typically rate LEDs at a nominal current –Luminous Flux –Efficacy 1W LED is usually.35A 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

18 Luminous Flux Increases With Current 18.35A Nominal LED can be driven at.5A to get 25% more luminous flux. This reduces the number of LEDs required.35A.5A 100% 125%

19 Luminous Flux Decreases With Temperature 19 Luminous flux reduces to 70% of nominal at 125C. This means big heat sinks are needed 50C125C 92% 70%

20 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 20 15% of power converted to light 85% converted to heat LED Thermal vias Heat sink

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

22 Initial Input Panel 22 Enter parameters here

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

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

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

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

27 Visualize the LED choices What is best for the goals? 27 Footprint of HS (cm 2 ) Efficacy (lumens/watt) Bubble size = cost 100 70 6478

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

29 Example Range of LED Options for 1300 Lumens 1 25cm 2 5.2C/W 77L/W$44.45 Heat SinkSizeEfficacyCostOptimization 12 LEDs 2 58cm 2 3.1C/W 63L/W$30.558 LEDs 5 1144cm 2.69C/W 97L/W$74.1613LEDs Temp 115C 114C 48C Osram Oslon LUW CP7PKTLP5C8E 29

30 30 Hands On Exercise 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 thetaSA 5)LED current Source: 24 – 32V Light output: 2000 lumens Neutral white LED Maximum string voltage: 60V No parallel LEDs on a single driver allowed Design Problem:Goals:

31 31 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 VinMin, then need to use Boost topology driver

32 32 Driving The LED – Switching Regulator Topology Buck (Step Down): –Simple –Lowest current requirements –Requires high input voltage (VinMin > Vled) Boost (Step Up): –Well known topology –Requires high current (Vin*In = Vout*Iout/Efficiency) Ex: Vin: 5V, Vout: 14V, Iout:.35A, Eff: 90%, –Requires Iin of 1.1A Buck/Boost –More complicated/expensive but needed if VinMin < Vout < VinMax (Battery)

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

34 Example Range of Driver Topology Options for 1300 Lumens, Vin = 14-22V Boost 88cm 2 69L/W$37.14 Driver+Array Total Size Total Efficacy Total Cost Topology Buck 91cm 2 67L/W$41.62 Buck/ Boost 94cm 2 60L/W$43.79 #LEDs 1 x 9 3 x 3 2 x 5 Osram Oslon LUW CP7PKTLP5C8E 34

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

36 9 LEDs + HS Driver LEDs Dominate the Design 36 6cm 2 82cm 2 $34.24 $2.90 FootprintSizeCost 1300 Lumens, Optimization 3, Boost Driver

37 37 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

38 38 Hands On Exercise 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) Source: 24 – 32V Light output: 2000 lumens Neutral white LED Maximum string voltage: 60V No parallel LEDs on a single driver allowed Design Problem:Goals:

39 Creating A Custom LED Array 39 Click on custom LED button

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

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

42 42 Hands On Exercise Customer wants more light: Source: 24 – 32V Light output: 2000 lumens Neutral white LED Maximum string voltage: 60V No parallel LEDs on a single driver allowed Use the custom LED array to increase the light output to 2500 lumens Design Problem:Goals: 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 thetaSA 8) LED current

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

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

45 45 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 designers needs Tools are available to visualize tradeoffs and make it easier to get to the best solution for your design requirements

46 46 Hands On Exercise See if you can find a FET that costs less. For the original FET and the replacement FET, what is the: 1)FET cost 2)FET temperature 3)Pdiss 4)Gate charge 5)RdsOn 6)Overall design efficiency Source: 14-22V -Light output: 2500 lumens -Neutral white LED -No limit on maximum string voltage -No parallel LEDs on a single driver allowed Use an LM3429 controller Design Problem:Goals:

47 47 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

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

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

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

51 Example: Effect of Output Cap Vin: 24-32V Light output: 650 lumens LED: 5 x Cree MX6AWT-A1-0000-000D51 ILED: 0.497A (target) LM3402 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

52 LM3402 with Cout Low Ripple Target 52 Cout

53 LM3402 with No Cout 53 No Cout Larger L1

54 LM3402 with Small Cout - 30% Ripple Target 54 Smaller Cout

55 Compare Output Cap Options 55 With output cap: 18mA ripple $1.61, 381mm2, 92%

56 Compare Output Cap Options 56 With output cap: 18mA ripple $1.61, 381mm2, 92% No output cap: 53mA ripple $1.64, 375mm2, 91%

57 Compare Output Cap Options 57 With output cap: 18mA ripple $1.61, 381mm2, 92% Small output cap: 65mA ripple $1.62, 362mm2, 92% No output cap: 53mA ripple $1.64, 375mm2, 91%

58 Example: Effect of PWM Dimming Frequency Vin: 24-32V Light output: 650 lumens LED: 5 x Cree MX6AWT-A1-0000-000D51 ILED:.497A (target) LM3402 Compare default 2kHz dimming frequency to 4kHz How will this affect the circuit behavior? 58

59 PWM Dimming Simulation 59

60 PWM Dimming 60 Dimming oscillator voltage LED Current 2 kHz dimming frequency

61 PWM Dimming Simulation 61 Click on Dimming Oscillator

62 Change PWM Dimming Frequency 62 Change pulse width Change pulse period

63 PWM Dimming Simulation 63 2 kHz dimming frequency 4 kHz dimming frequency

64 64 Hands On Exercise 1) Using the default input transient range of 24V – 32V, what is the LED current overshoot and undershoot? 2) Change the input transient to 26V to 30V. What is the LED curent overshoot and undershoot? Create a design using the following: Source Voltage: 24 – 32V Light output: 650 lumens Cool White Optimization 3 LED: 5 x Cree MX6AWT-A1- 0000-000D51 LM3402 Run a line transient simulation Design Problem:Goals:

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

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


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