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Jeff Perry WEBENCH Manager

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Presentation on theme: "Jeff Perry WEBENCH Manager"— Presentation transcript:

1 Jeff Perry WEBENCH Manager
WEBENCH LED Tools Jeff Perry WEBENCH Manager

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

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

4 LED Selection Parameters

5 Explosion of Applications for LEDs
General Illumination: Architectural Residential Industrial Portable Consumer Outdoor Area Projectors & Copiers Entertainment Lighting Retail Display Medical Emergency/Safety Lighting Signs and Channel Lettering Automotive: Headlights RCL CHMSL Interior Lighting Instrument Panel Infotainment Backlighting Aviation, Marine, and Rail Crash Avoidance The increasing cost of energy and concern about climate change is driving the LED market. LEDs can be used in a broad array of applications. At the same time, LED technology is undergoing rapid change and innovation. Thus there is a need to stay current with the latest developments. Mobile Devices: Display backlighting Camera flash Backlighting & Projection: Infotainment Large format TV displays Laptops Pocket & Data Projectors

6 Quantifying Light From LEDs
The luminosity function defines wavelengths of light which human eye is sensitive to. This is used as a metric for measuring the usable light output of light sources such as incandescent bulbs, compact fluorescent lamps and LEDs. Luminous flux is a measure of the radiation of the luminosity function from a light source. Units are in lumens. Luminous Flux (Lumens) Luminosity Function 6 6

7 LED Color – Dominant Wavelength
Sampling of color LEDs The dominant wavelength (LambdaD) of an LED is the parameter used to specify the color. Taking a sampling of LEDs on the market, there is some variation among the color description. Sampling of LEDs in the webench library – Definition of “red” can vary Orange Blue Cyan Green Red Yellow/ Amber 7 7

8 White LEDs – Color Temperature
Sampling of white LEDs Incandescent Bulb Daylight White LEDs come in a variety of color temperatures. The color temperature correlates to what the human eye perceives from a light source as compared to an ideal black body radiator at a certain surface temperature. This slide shows how WEBENCH LED Designer categorizes them Red Tint Blue Tint Warm White White Cool White 8 8

9 Luminous Flux – Comparison Chart
Application Brightness (lumens) 40W tungsten bulb 500 100W tungsten bulb 1,500 25W compact fluorescent 55W halogen auto headlight 35W high intensity discharge auto headlight 3,250 150W halogen projector bulb 5,000 150W high pressure sodium bulb 16,000 The high pressure sodium street lamp retails for $51.30 and has a lifetime of 30,000 hours. It contains mercury. The luminous efficacy is 107 lumens/watt. 9 9

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 Luminous Flux for LEDs Most efficient
Sampling of .35A cool white LEDs: Most efficient 140 100 Lumens Flux The luminous flux/watt is shown for a sampling of .35A LEDs. There are some LEDs with over 100 lumens output. At 25C, it would take about 5 of these to be equivalent to a 40W tungsten filament light bulb and about 15 to be equivalent to a 100W tungsten bulb. 1.2 Power 11 11

12 WEBENCH® LED Architect
Overview of the NEW Webench tool 12

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

14 WEBENCH® LED Architect Overview
Select LED & Driver Analyze & Optimize Simulate Build It WEBENCH LED Designer has 4 main steps 14 14

15 How to Access WEBENCH® LED Architect
Use the entry panel on To access WEBENCH LED Designer go to 15 15 15

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

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

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

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

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

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

22 Initial Input Panel Enter parameters here

23 Enter LED Requirements
1) Input voltage 2) Ambient temperature 3) Desired light output 4) LED color The basic requirements are shown on the LED Requirement panel Advanced inputs

24 Advanced inputs Max Vout Parallel strings on 1 driver
Max heat sink dimensions Manufacturer Max junction temperature If the user clicks on the advanced inputs link, the user can place limits on critical parameters. This includes the maximum Vout voltage which may be desired to be limited in order to pass safety specifications (60V is typical max). Here the user can also allow for parallel strings on one driver. This can lead to problems with current sharing and brightness between strings, however. The maximum heat sink size can be specified along with the maximum allowed junction temperature. In addition, the manufacturer and distributor can be selected.

25 Step 1: Choose The Ideal LED Solution
LEDs and heat sink required to give the desired light output The user is presented with a variety of LED + heat sink choices. These are all configured to meet the user’s light output requirement. Based on the optimization knob setting, the software calculates the number of LEDs required at the optimal LED current, and then selects a heat sink. The cost of the heat sink and LEDs, luminous efficacy and heat sink footprint are calculated and displayed in a table and graph. In addition, a thumbnail view of the LEDs arrayed on the heat sink is provided.

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

27 Visualize the LED choices What is best for the goals?
100 Bubble size = cost Footprint of HS (cm2) A graph is provided which shows the heat sink footprint vs luminous efficacy. The bubble size is the cost of the LEDs and heat sink. In this way, the user can quickly visualize the best solution. The user can click and drag the mouse to zoom in and get more details. The best results are in the lower right corner with small bubble size. 70 64 78 Efficacy (lumens/watt)

28 Optimize the LED Solution
Optimization knob 1 = Smallest footprint 2 = Lowest cost 3 = Balanced 4 = Higher efficacy 5 = Highest efficacy By turning the optimization knob, the user can change the design goals from a balanced design (3), low cost (2), small footprint (1) and high efficiency/luminous efficacy (4, 5). For each knob setting the software calculates different LED and heat sink solutions to best achieve the design goals.

29 Example Range of LED Options for 1300 Lumens
25cm2 5.2C/W 77L/W $44.45 Heat Sink Size Efficacy Cost Optimization 12 LEDs 2 58cm2 3.1C/W 63L/W $30.55 8 LEDs 5 1144cm2 .69C/W 97L/W $74.16 13LEDs Temp 115C 114C 48C Here are several options for a system of 1300 lumens at different optimization knob settings. This includes the LEDs and heat sink but not the driver. The first option is at knob setting 1 which targets low footprint. This has the lowest footprint, but also the relatively low efficacy high temperature and high price. Knob setting 2 gives the lowest price, but the efficacy drops and the size goes up. The temperature remains high. Option 5 has the highest luminous efficacy and the lowest temperature which will lead to better reliability, but also has the highest cost and the largest footprint. Thus we can see there are tradeoffs to be made for each important parameter. Note: The costs are for low volumes and should be used for relative comparisons. Osram Oslon LUW CP7PKTLP5C8E 29

30 Hands On Exercise Source: 24 – 32V Light output: 2000 lumens
Design Problem: Goals: Source: 24 – 32V Light output: 2000 lumens Neutral white LED Maximum string voltage: 60V 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: LED manufacturer LED part number # LEDs Heat sink thetaSA LED current 30 30 30

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 Since multiple LEDs are normally required to get the desired amount of light, the LED array must be determined. There are advantages and disadvantages in both parallel and series arrangement of the LEDs. 31 31

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) LEDs are DC devices and require an LED driver to maintain constant current. When using a switching regulator, which topology can be used depends on the input voltage and LED array voltage and current. WEBENCH shows different topologies and the tradeoffs that each one brings. 32 32

33 Step 2: View LED + Driver Solutions
Complete solutions including: LED array Heat sink Driver(s) On the select driver page, the user is presented with a listing of suitable LED driver solutions for the selected LED array. These include different arrangements of the LEDs in series and parallel strings. As a result, there may be several different topologies each with different numbers of drivers. For example, let’s take a case where the input voltage is 24V with 10 LEDs each having 3V forward voltage drop and a drive current of .5A. To drive 10 of these LEDs, they can be put in a single series string of 10 which would result in a total of 30V and .5A, which might require a boost topology. Or they could be arranged into 2 parallel strings of 5 which gives at total of 15V which would enable a buck topology. But this would require 2 drivers if parallel strings on a driver were not desired (this is the default case in WEBENCH and it can be modified in the advanced inputs panel).

34 Example Range of Driver Topology Options for 1300 Lumens, Vin = 14-22V
Boost 88cm2 69L/W $37.14 Driver+Array Total Size Efficacy Cost Topology Buck 91cm2 67L/W $41.62 Buck/ 94cm2 60L/W $43.79 #LEDs 1 x 9 3 x 3 2 x 5 Osram Oslon LUW CP7PKTLP5C8E Here are several options for a system of 1300 lumens using a DC input of 14-22V. This highlights the differences between the three topologies. The numbers are for the entire system including the LEDs, heat sink and driver. Thus we can see there are tradeoffs to be made for each important parameter. The costs are for low volumes and should be used for relative comparisons. 34

35 LED System tradeoffs 106 Footprint of HS+driver (cm2) Buck Boost
The user is presented with a graph of the footprint, efficacy and price for various LED/heat sink/driver options. In this case, the boost drivers tend to be the most efficient and have the smallest footprint. The buck options require more drivers and so they end up being more expensive than the single boost driver. In other applications, the result may be different. 86 59 69 System efficacy (lumens/watt)

36 LEDs Dominate the Design
Footprint Size Cost 9 LEDs + HS 82cm2 $34.24 Driver Here is a closer look at one of the LED/heat sink/driver combinations. The LED and heat sink dominate the numbers. 6cm2 $2.90 1300 Lumens, Optimization 3, Boost Driver

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 The user can utilize the full capabilities of WEBENCH Designer. In addition, on the left side of the WEBENCH page is a listing of system level parameters, a block diagram schematic of the LED and driver array and a representation of the LEDs on the heat sink. If there are multiple drivers of the same type, changing the design in WEBENCH Designer for one driver will automatically change it for all the drivers.

38 Hands On Exercise Source: 24 – 32V Light output: 2000 lumens
Design Problem: Goals: Source: 24 – 32V Light output: 2000 lumens Neutral white LED Maximum string voltage: 60V 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 38 38

39 Creating A Custom LED Array
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

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

42 Hands On Exercise Customer wants more light: Source: 24 – 32V
Design Problem: Goals: 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 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 42 42 42

43 Optimization – Efficiency vs Footprint
Left side: Higher frequency Smaller footprint Right side: Lower frequency Lower resistance Here is a summary of optimizations done on a buck controller design. In general, at a high optimization number, the frequency is lower, which causes lower AC switching losses. However, it also requires more inductance to limit the ripple current. This results in a larger inductor due to the higher number of turns required and larger overall footprint. At the lower optimization settings, the opposite is true. Higher frequency requires less inductance and thus, results in smaller inductors and lower overall footprint. There are additional factors being weighted in the selection process including parasitic resistance (ESR, DCR), component cost and availability. 43

44 Optimization – Power Dissipation
As freq is decreased: FET Pdiss improves L Pdiss may get worse Higher L is required to maintain VoutPP L = V*dt/di At the higher optimization numbers with lower frequency, the AC switching losses decrease so the power dissipation of the M1 and M2 FETs decreases dramatically. However the requirement for larger inductance to keep the Vout ripple low usually results in higher inductor power dissipation due to more turns/more wire/higher DCR. This partially offsets the effect of lower switching losses. Lower frequency

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 designer’s needs Tools are available to visualize tradeoffs and make it easier to get to the best solution for your design requirements

46 Hands On Exercise Source: 14-22V -Light output: 2500 lumens
Design Problem: Goals: 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 See if you can find a FET that costs less. For the original FET and the replacement FET, what is the: FET cost FET temperature Pdiss Gate charge RdsOn Overall design efficiency 46 46 46

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

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

50 Model Verification: Sim vs Bench
LED Current Switch Voltage When creating Spice models, it is very important to verify the results against bench data. This can be a time consuming process. Spice model verification involves taking bench data at various operating points and comparing to simulation Inductor Current

51 Example: Effect of Output Cap
Vin: 24-32V Light output: 650 lumens LED: 5 x Cree MX6AWT-A D51 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

52 LM3402 with Cout Low Ripple Target

53 LM3402 with No Cout Larger L1 No Cout

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

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

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

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

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

59 PWM Dimming Simulation

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

61 PWM Dimming Simulation
Click on Dimming Oscillator

62 Change PWM Dimming Frequency
Change pulse width Change pulse period

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

64 Hands On Exercise Create a design using the following:
Design Problem: Goals: Create a design using the following: Source Voltage: 24 – 32V Light output: 650 lumens Cool White Optimization 3 LED: 5 x Cree MX6AWT-A D51 LM3402 Run a line transient simulation 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? 64 64 64

65 Summary WEBENCH LED Architect: Considers LED and heat sink properties
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

66 Also FPGA Power Architect:
Thank You! Try WEBENCH® LED Architect yourself : Also FPGA Power Architect: 66

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