Efficient and Power Saving Driving Methods for High Power LEDs in General Lighting Applications

Transcription

1 Efficient and Power Saving Driving Methods for High Power LEDs in General Lighting Applications Conference Electronic Displays 2011 March 2-3 Nürnberg Georg Machon RoodMicrotec Stuttgart Based on essential technical advantages the entrance of High Power LEDs in general lighting market is now and in the future one of the main goals of the LED industry. By providing the suitable driver electronics, controls and LED types, the qualitative and quantitative aspects of the light produced can be nearly fully controlled. In many of todays applications different drivers, power converters, power conditioning and controllers are in most instances absolute necessary components of an LED Light System and are very important for the light quality, the life time behaviour and for failure / degradation aspects. High Power LEDs offers a high luminous efficiency, a big color variety and beside the large standard LED product spectrum nearly unlimited possibilities for customized solutions in different l ranges of lighting applications and new more intelligent products. In comparison with conventional light sources the use of High Power LEDs makes possible energy reduction up to 80% and an extension of life time by factor Stable optical characteristics and a long life time of a LED Light source requires a application dependent driver electronic in order to fulfill the customer product requirements electrically and optically. The operating conditions are to be considered, in particular the temperature influence for luminous intensity, lifetime- and color behaviour. In order to investigate the LED Driver Electronic`s Quality and to guarantee the product performance related to the product requirements additional tests are strongly recommended. Valid safety- and EMI Standards / Requirements have to be taken into account. It is shown here, how an energy efficient power saving and flexible electronic drive was realized for LED based lighting application. Overview : 1. The High Power LED Market / Efficiency Light Sources 2. Driver Requirements for a LED Lamp Lighting Application 3. Basic Arrangement LEDs in Lamp Applications 4. Important specification details used 1 W Power LED white 5. PFC and Constant Current Driver Electronics 6. Layout PCB Board LED Driver / assembled PCB 7. Functional test results 8. LED Lamp / Driver Qualification / Evaulation Tests / Energy Star 1

2 1. The High Power LED Market Strong Growth in the High Power LED market Source: Veeco Investment Relations Presentation Segment dependent growth LED Market Source: Strategies Unlimited August

3 Incandescent Bulb Compact Fluorescent Lamp HP Cree LED Comparison dimensions incandescent bulb / compact fluorescent lamp / Cree HP LED Source: Big Stock Photo and Cree Comparison efficiency traditional light sources / LED light sources Source Department of Energy (DOE) 3

4 2. Driver Requirements for a LED Lamp Lighting Application Number of 1 W LEDs white variable ( 10 LEDs in series configuration ) Parameter Value Input voltage range variable V AC Power Factor 0.90 min. Output voltage V Output current 350mA ± 3 % max Output power 40W max ( 40 LEDs ) 2 independent constant current outputs / each 20LEDs max. Load regulation <3% Life time 30000h Output short / open circuit protection Dimensions 235 x 26 x 25 mm max Operating Temperature Range -20 C + 50 C Storage Temperature Range -30 C. +70 C Consideration of Safety / EMI Standards Essential criteria for choice of suitable electronic components Technical requirements Availability Cost factor Under these points of view related to the key components the market analysis led to the following results: PFC Controller L6562 A ST Microelectronics Constant Current Driver HV 9961 Supertex The used and realized electronic schematic regarding this task is based on helpful support / application notes from Supertrex, Retronic and. ST Microelectronic. 4

5 3. Basic Arrangement LEDs in Lamp Applications Source Invertronics Series Configuration Parallel ( series ) String Configuration Matrix Configuration Multi Channel Configuration 5

6 Bypass Circuit with additional zener diode to avoid a complete failure using series configuration ( if led failure open circuit ) 6

7 4. Important specification details used 1 W Power LED white Source Data Sheet Avago ASMT-MYK9-NKM00 Absolute Maximum Ratings DC Forward Current 500 ma Power Dissipation 2100 mw LED Junction Temperature 125 C Operating Range at 350 ma - 40 to C Storage Temperature Range -40 to +120 C Electrical Characteristic at 350 ma (T J = 25 C) Forward Voltage: V F (Volts) Min. Typ. Max: Thermal Resistance R.j-b ( C/W) : 14 Optical Characteristics at 350 ma (T J = 25 C) Correlated Color Temperature,CCT (Kelvin) : Viewing Angle deg : 110 Luminous Effciency (lm/w) : 80 Min Forward voltage vs. forward current Relative luminous flux vs. forward current Chromaticity coordinate shift vs. forward current (Warm White) Relative light output vs. junction temperature 7

8 Forward voltage shift vs. junction temperature Maximum forward current vs. ambient temperature Recommended soldering profile ( Critical ) 8

9 5. PFC and Constant Current Driver Electronics The power factor is defined as the ratio of the real power flowing to the load to the apparent power in the circuit. PF = Real Power (W ) / Apparent Power ( VA ) Real Power is the average over the cycle the product of current and voltage Apparent Power is the RMS Value and the RMS Value of Voltage If current and voltage are sinusoidal and in phase, the Power Factor is 1.0. If current and voltage are sinusoidal and not in phase, the PF is the cosine of the phase angle Data Source Diagrams ON Semiconductor Switched Mode Power Supply without PFC Typical Power Supply PF 0,4-0,6 Harmonic Content Typical Power Supply Optimized PFC Switched Mode Power Supply PF 0,9-1.0 Harmonic Content with optimized PFC 9

10 Schematic / Short form description used PFC Circuit STM L6562A Data Source ST Microelectronics 10

11 Schematic / Short form description used Constant Current Driver Supertex HV 9961 Data Source Supertex 2 Constant Current Driver Supertex HV 9961 are used 11

12 6. Layout PCB Board LED Driver / assembled PCB The layout requires the consideration of the aspects concerning electrical safety, functionally as well as thermal and EMI requirements. PCB Board LED Driver Layer 1 PCB Board LED Driver Layer 2 PCB Board LED Driver Layer 3 PCB Board LED Driver Layer 4 12

13 Assembled PCB Top View PCB Bottom View PCB Temperature Distribution functional Temperature Scale: green : 30 C orange : 40 C red : 50 C Temperature Distribution Driver Top View at max Load 50W / Tamb = 25 C 13

14 7. Functional Test results Measured with Yokogawa Power Analyzer WT 3000 LED Driver circuit / output 1 = 10 LEDs in series Configuration : output 1 = 10 LEDs Input Voltage : Uin = 80V AC Power Factor : PF = 0,99 Configuration : output 1 = 10 LEDs Input Voltage : Uin = 240V AC Power Factor : PF = 0,89 14

15 LED Driver circuit / output 1 = 20 LEDs in series Configuration : output 1 = 20 LEDs Input Voltage : Uin = 80V AC Power Factor : PF = 0,99 Configuration : output 1 = 20 LEDs Input Voltage : Uin = 240V AC Power Factor : PF = 0,93 15

16 LED Driver circuit / output 1 = 20 LEDs / output 2= 10 LEDs in series Configuration : output 1 = 20 LEDs / output 2= 10 LEDs Input Voltage : Uin = 80 V AC Power Factor : PF = 0,99 Configuration : output 1 = 20 LEDs / output 2= 10 LEDs Input Voltage : Uin = 240 V AC Power Factor : PF = 0,95 16

17 LED Driver circuit / output 1 = 20 LEDs / output 2= 20 LEDs in series Configuration : output 1 = 20 LEDs / output 2= 20 LEDs Input Voltage : Uin = 80 V AC Power Factor : PF = 1,00 Configuration : output 1 = 20 LEDs / output 2= 20 LEDs Input Voltage : Uin = 240 V AC Power Factor : PF = 0,97 17

18 8. LED Lamp / Driver Qualification / Evaulation Test / Energy Star Data Source: Energy Star Detail Coordination with the customer required Example Requirements for INITIAL ENERGY STAR qualification: Data for LED package(s), array(s), or module(s) used in the integral LED lamp Temperature Measurement Point (TMP) temperature verification of LED in thel LED lamp Lamp Base Efficiency Rapid-Cycle Stress Test 3,000-hour lumen maintenance Color Rendering (CRI) Correlated Color Temperature (CCT) / Chromaticity measurements for each sample Power Factor Transient Protection Operating Frequency Electromagnetic Interference Example additional recommended Test Procedures Life Test Operating / Tamb max / Storage Test Tamb min / max Humidity operating / non operating Mechanical Shock / altitude Vibration Emissions Conformity Safety Standards 18