DESIGN EXAMPLE REPORT Title 4.2 W Non-Isolated LED Driver LNK605DG Specification 85 – 265 VAC Input; 12 V, 350 mA Output Application LED Driver Author Applications Engineering Department Document Number DER-186 Date September 10, 2008 Revision 1.1 Summary and Features • • • Accurate primary-side constant voltage, constant current (CV/CC) controller eliminates optocoupler and all secondary side CV/CC control circuitry • ±5% output voltage and ±10% output current accuracy including line, load, temperature, and component tolerances • No current-sense resistors for maximized efficiency • Low part-count solution for lower cost Auto-restart for output short circuit and open-loop protection EcoSmart® – Easily meets all existing and proposed international energy efficiency standards – China (CECP) / CEC / EPA / European Commission • ON/OFF control provides constant efficiency to very light loads • No-load consumption <200 mW at 265 VAC • Ultra-low leakage current: <5 µA at 265 VAC input (no Y capacitor required) • Easy compliance to EN550015 and CISPR-22 Class B EMI • Meets ENERGY STAR requirements for Solid State Lighting (SSL) luminaries • Green package: halogen free and RoHS compliant PATENT INFORMATION The products and applications illustrated herein (including transformer construction and circuits external to the products) may be covered by one or more U.S. and foreign patents, or potentially by pending U.S. and foreign patent applications assigned to Power Integrations. A complete list of Power Integrations' patents may be found at www.powerint.com. Power Integrations grants its customers a license under certain patent rights as set forth at <http://www.powerint.com/ip.htm>. Power Integrations 5245 Hellyer Avenue, San Jose, CA 95138 USA. Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-186 – 12 V, 350 mA LED Driver 10-Sep-08 Table of Contents 1 2 3 4 5 Introduction.................................................................................................................3 Prototype Photo..........................................................................................................4 Power Supply Specification ........................................................................................5 Schematic...................................................................................................................6 Circuit Description ......................................................................................................7 5.1 LNK605DG Operation .........................................................................................7 5.2 Input Filter ...........................................................................................................7 5.3 Tapped Buck Operation ......................................................................................7 5.4 Output Regulation ...............................................................................................8 6 PCB Layout ..............................................................................................................10 7 Bill of Materials .........................................................................................................11 8 Tapped-inductor Specifications ................................................................................12 8.1 Electrical Diagram .............................................................................................12 8.2 Electrical Specifications.....................................................................................12 8.3 Materials............................................................................................................12 8.4 Tapped Inductor Build Diagram.........................................................................13 8.5 Winding Instruction............................................................................................13 9 Design Spreadsheet .................................................................................................14 10 Performance Data.................................................................................................16 10.1 Efficiency with LED Load – Full Load ................................................................16 10.2 No-load Input Power..........................................................................................17 10.3 Output Characteristics .......................................................................................18 10.4 Thermal Performance........................................................................................18 10.5 Output Ripple Measurements............................................................................19 10.5.1 Ripple Measurement Technique ................................................................19 10.5.2 Measurement Results ................................................................................20 11 Output Current Ripple ...........................................................................................21 11.1 Load Current Ripple ..........................................................................................21 11.2 Inductor Current ................................................................................................22 12 Waveforms............................................................................................................24 12.1 Output Voltage Startup Profile...........................................................................24 12.2 Output Current Startup Profile ...........................................................................25 12.3 Drain Voltage and Current.................................................................................26 13 Transient Protection..............................................................................................28 14 Conducted EMI .....................................................................................................29 15 Revision History ....................................................................................................31 Important Note: Although this board is designed to satisfy safety isolation requirements, the engineering prototype has not been agency approved. Therefore, all testing should be performed using an isolation transformer to provide the AC input to the prototype board. Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Page 2 of 32 10-Sep-08 DER-186 – 12 V, 350 mA LED Driver 1 Introduction This engineering report describes the design for a non-isolated, universal input, 12 V, 350 mA constant voltage/constant current (CV/CC) power supply for LED driver applications, utilizing a LNK605DG device from the LinkSwitch-II family in a tappedinductor buck configuration. A tapped buck topology is ideal for converters with a high ratio of voltage input to voltage output. This topology provides current multiplication on the output, making it possible to use smaller devices, or to lower dissipation losses in the MOSFET. The tapped buck, non-isolated topology used in this design lends itself to advantages such as smaller PCB size, a smaller transformer, and greater efficiency than in the flyback topologies described in DER-184 and DER-185 (also using LinkSwitch-II devices.) The worst-case full load efficiency for this design is 80%, which is an improvement over the 74% efficiency of the previous two DER solutions. The EMI filtering is simpler in this buck topology, since there is far less common-mode noise, and lends itself to using fewer components. This design operates primarily in CC mode; CV mode only occurs when the load is disconnected, allowing the supply to operate in a safe mode, indefinitely, with the LED load disconnected. This document contains the power supply design’s specifications, schematic, bill of materials, inductor specifications, and typical performance characteristics. Page 3 of 32 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-186 – 12 V, 350 mA LED Driver 10-Sep-08 2 Prototype Photo Figure 1 – Prototype Top View. Figure 2 – Prototype Bottom View. Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Page 4 of 32 10-Sep-08 DER-186 – 12 V, 350 mA LED Driver 3 Power Supply Specification Description Input Voltage Frequency No-load Input Power (230 VAC) Output Output Voltage 1 Output Ripple Voltage 1 Output Current 1 Total Output Power Continuous Output Power Efficiency Full Load Symbol Min Typ Max Units Comment VIN fLINE 85 47 265 64 300 VAC Hz mW 2 Wire – no P.E. 50/60 Measured at the output capacitor VOUT1 VRIPPLE1 IOUT1 12 300 350 V mV mA POUT 4.2 W η 80 % 20 MHz bandwidth Environmental Conducted EMI Meets CISPR22B / EN55022B Designed to meet IEC950, UL1950 Class II Safety Surge Ambient Temperature Page 5 of 32 2 TAMB -5 kV 50 o C 1.2/50 µs surge, IEC 1000-4-5, Series Impedance: Differential Mode: 2 Ω Common Mode: 12 Ω Free convection, sea level Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-186 – 12 V, 350 mA LED Driver 10-Sep-08 4 Schematic Figure 3 – Circuit Schematic. Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Page 6 of 32 10-Sep-08 DER-186 – 12 V, 350 mA LED Driver 5 Circuit Description This circuit uses the LinkSwitch-II family product LNK605DG in a non-isolated tapped buck power-supply configuration. The LNK605DG device (U1) incorporates a power switching device, an oscillator, a CV/CC control engine, and startup and protection functions all in one IC. The integrated 700 V MOSFET allows sufficient voltage margin for universal input AC applications. The power supply delivers full output current during the maximum forward voltage drop of the LED. The LNK605DG’s IC package provides extended distance between high and low voltage pins (both at the package and the PCB), which is required in very humid or highly polluted environments to prevent arcing and to further improve reliability. 5.1 LNK605DG Operation The LNK605DG monolithically integrates a 700 V power MOSFET switch and ON/OFF control. The constant voltage (CV) regulation provides ±5% accuracy. The CV function is not needed during normal operation in this application. The CV feature provides inherent output over-voltage protection in case any LEDs fail open circuit or if the load becomes disconnected. Beyond the maximum power point, the switching frequency is reduced to provide a constant output current at an accuracy of ±10%. This makes the LNK605DG ideal for driving LEDs, which require a constant current level for consistent light output and long life operation. In addition, internal compensation allows the ±5% voltage and ±10% current accuracies to be met across component tolerances, device tolerances, temperature, and line input voltage variations. The LNK605DG also provides a sophisticated range of protection features such as autorestart and thermal shutdown. Auto-restart is triggered by fault conditions which include an open feedback loop or a shorted output. Accurate hysteretic thermal shutdown ensures safe average PCB temperatures under all conditions. 5.2 Input Filter Diodes D3, D4, D5, and D6 rectify the AC input. The resulting DC is filtered by the bulk storage capacitors, C4 and C5. Inductor L1 and capacitors C4 and C5 form a pi (π) filter, which attenuates conducted differential-mode EMI noise. This configuration enables easy compliance to EMI standard EN55015 class B, with 10 dB of margin. Fusible, flameproof resistor RF1 acts as a fuse and should be rated to withstand the instantaneous dissipation when the supply is first connected to the AC. Wire-wound or oversized metalfilm resistors work well for this purpose. 5.3 Tapped Buck Operation Figure 3 shows the schematic for a tapped buck converter, based on the LNK605DG. A power supply using a tapped buck topology operates in a way very similar to one with a buck topology. When the switch turns on (closes), current ramps up and flows through Page 7 of 32 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-186 – 12 V, 350 mA LED Driver 10-Sep-08 the complete inductor (pin 7 to pin 4), and through the load (the LEDs). The load current is filtered by C1 to remove the switching component from the current waveform. Diode D1 is reverse-biased and so does not conduct during this time. The current continues to ramp up until it reaches the current limit value, which causes the switch to turn off (open). When the switch turns off, the energy in the input section of inductor (T1) couples through to the output section (pin 7 to pin 8). The peak current in the output winding steps up by a factor of 4.6 (equal to the ratio of total inductor turns to the output section turns), keeping the total ampere-turns constant. This stepped (magnified) current flows out of the output winding, through free-wheeling diode D1, and back through the load. (See Figure 16 though Figure 19.) Due to non-ideal coupling between the tapped windings, some of the stored energy does not couple to the output winding. The leakage energy in the input section of T1 (pin 4 to pin 1) causes a voltage spike at turn off. This spike is limited by the intra-winding capacitance of T1. This parasitic capacitance is sufficient to keep the voltage spike from exceeding the BVDSS (700 V) of the MOSFET internal to U1. The voltage stress on the switch in this design is equal to that in a Flyback converter using a transformer with the same turns ratio. The chosen turns ratio ensures the circuit operates in discontinuous mode (DCM) at low line (85 VAC). This ratio (the inductor ratio) can be calculated as Inductor Ratio = Total Inductor turns 124 = = 4.6 Output Winding Turns 27 5.4 Output Regulation The LNK605DG regulates output using ON/OFF control for CV regulation, and frequency control for constant current (CC) regulation. Feedback resistors R1 and R2 have 1% tolerance values to assist accurately centering both the nominal output voltage and the CC regulation threshold. The CV feature provides output over-voltage protection (OVP) in case any LEDs have open-circuit failures. This design operates primarily in CC mode, but it goes into CV mode below full load, or when the load is disconnected. A feedback winding tracks and regulates the output. This winding must be closely coupled to the tapped section (the section of winding between pin 7 and pin 8) of T1. Traversing from no load to full load, the controller within the LNK605DG first operates in CV mode. Upon detecting the maximum power point, the controller enters CC mode. While the LNK605DG operates in the CV region, it regulates the output voltage by adjusting the ratio of enabled cycles to disabled switching cycles. This also optimizes the efficiency of the converter over the entire load range. As the load current increases, the current limit is increased and fewer and fewer cycles are skipped. Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Page 8 of 32 10-Sep-08 DER-186 – 12 V, 350 mA LED Driver At the point where no switching cycles are skipped (concurrent to the maximum power point) the controller within the LinkSwitch-II transitions into CC mode. A further increase in the demand for load current causes the output voltage to drop. This drop in output voltage is reflected on the FB pin voltage. In response to the voltage reduction on the FB pin, the switching frequency is reduced to achieve constant output current. Page 9 of 32 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-186 – 12 V, 350 mA LED Driver 6 10-Sep-08 PCB Layout Figure 4 – PCB Layout (43mm x 23mm). . Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Page 10 of 32 10-Sep-08 DER-186 – 12 V, 350 mA LED Driver 7 Bill of Materials Item Qty Ref Des 1 2 1 1 C1 C3 3 4 2 1 5 6 4 1 C4 C5 D1 D3 D4 D5 D6 L1 7 1 R1 8 9 10 1 1 1 R2 R4 RF1 11 12 1 2 13 1 14 1 15 1 Description Mfg 330 µF, 16 V, Electrolytic, Very Low ESR, 72 mOhm, (8 x 11.5) 1 µF, 25 V, Ceramic, X7R, 0805 4.7 µF, 400 V, Electrolytic, (8 x 11.5) 100 V, 1 A, Schottky, DO-41 1000 V, 1 A, Rectifier, DO-41 470 µH, 0.3 A, 5.5 x 10.5 mm 49.9 kΩ, 1%, 1/16 W, Metal Film, 0603 8.25 kΩ, 1%, 1/16 W, Metal Film, 0603 3 kΩ, 5%, 1/8 W, Metal Film, 0805 8.2 Ω, 2 W, Fusible/Flame Proof Nippon Chemi-Con Panasonic Taicon Corporation Vishay TAQ2G4R7MK0811MLL3 SB1100 Vishay Tokin 1N4007-E3/54 SBC1-471-301 Panasonic ERJ-3EKF4992V Panasonic Panasonic Vitrohm Hical Magnetics Keystone ERJ-3EKF8251V ERJ-6GEYJ302V CRF253-4 5T 8R2 T1 Bobbin, EE10, Vertical, 8 pins TP1 TP4 Test Point, BLK,THRU-HOLE MOUNT Test Point, WHT,THRU-HOLE TP2 MOUNT Keystone Test Point, RED,THRU-HOLE TP3 MOUNT Keystone LinkSwitch-II, LNK605DG, CV/CC, Power SO-8C Integrations U1 Page 11 of 32 Mfg Part Number EKZE160ELL331MHB5D ECJ-2FB1E105K 101 5011 5012 5010 LNK605DG Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-186 – 12 V, 350 mA LED Driver 10-Sep-08 8 Tapped-inductor Specifications 8.1 Electrical Diagram Figure 5 – Transformer Electrical Diagram. 8.2 Electrical Specifications Electrical Strength Main Inductance Resonant Frequency Primary Leakage Inductance 8.3 1 second, 60 Hz, from Primary to Secondary Pins 4 - 7, short Pin 1 and Pin 8 together, measured at 80 kHz, 0.4 VRMS Pins 4 - 7, Pin 1 and Pin 8 are shorted together with all other windings open Pin 4 to pin 1, Pin 7 and Pin 8 are shorted together N/A 1.32 mH, ±10% 1.1 MHz 18 µH Materials Item [1] [2] [3] [4] [5] [6] [7] Description 2 Core: PC44, gapped for AL of 86.3 nH/t Bobbin: Horizontal 8 pin, EE10 Magnet Wire: #34 AWG Magnet Wire: #27 AWG Magnet Wire: #33 AWG Tape, 3M 1298 Polyester Film, 2.0 Mils thick, 7.0 mm wide Varnish Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Page 12 of 32 10-Sep-08 8.4 DER-186 – 12 V, 350 mA LED Driver Tapped Inductor Build Diagram Figure 6 – Transformer Build Diagram. 8.5 Winding Instruction WD1 Main Winding Insulation WD #2 Tap Winding Insulation WD #3 Feedback Winding Insulation Core Assembly Varnish Page 13 of 32 Primary Pin side of the bobbin oriented to right hand side. Start at pin 4. Wind 97 turns of item [3] in three layers. Wind with tight tension across bobbin evenly. End at pin 1. 1 Layer of tape [6] for insulation. Start at pin 8. Wind 27 turns of item [4] in two layers. Terminate on pin 7. Wind with tight tension and spread turns across bobbin evenly. 1 layer of tape [6] for basic insulation. Starting at pin 6, wind 27 turns of item [5] in one layer. Finish on pin 5. Wind with tight tension and spread turns across bobbin evenly. 2 layers of tape [6] for basic insulation. Gap core and assemble and secure core halves. Dip varnish assembly with item [7]. Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-186 – 12 V, 350 mA LED Driver 10-Sep-08 9 Design Spreadsheet ACDC_LinkSwitchINPUT II_Tapped Buck_051308; Rev.0.3; Copyright Power Integrations 2008 ENTER APPLICATION VARIABLES VACMIN 85 VACMAX 265 fL 50 VO 12 IO 0.35 Power n 0.8 Z INFO OUTPUT 4.20 0.80 UNIT V V Hz V A W 0.50 tC CIN 3.50 ms uF 87.32 374.77 V V 10 DC INPUT VOLTAGE PARAMETERS VMIN VMAX ENTER LinkSwitch-II VARIABLES LNK Chosen Device 605 DG Package ILIMITMIN ILIMITTYP ILIMITMAX LNK605 A A A 80.00 kHz VDS VD 10.00 0.50 V V DESIGN PARAMETERS DCON TON 7.46 4.71 us us TDEAD 0.32 us 80 ENTER INDUCTOR CORE/CONSTRUCTION VARIABLES Core Type EE10 Core EE10 Bobbin EE10_BOBBIN AE 12.10 mm^2 LE 26.10 mm^2 AL 850.00 nH/turn^ 2 BW 6.60 mm INDUCTOR DESIGN PARAMETERS LPMIN 1263.81 uH LPTYP 1327.01 uH LP_TOLERANCE NL_TOTAL ALG 5 5.00 124.00 86.30 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Minimum Input DC bus voltage Maximum Input DC bus voltage Chosen LinkSwitch-II device DG 0.30 0.31 0.35 FS ACDC_LinkSwitch-II_Tapped Buck_051308_Rev0-3.xls; LinkSwitch-II Discontinuous Tapped Buck Design Spreadsheet Customer Minimum AC Input Voltage Maximum AC Input Voltage AC Mains Frequency Output Voltage of LED strings Output Current driving LED strings Continuous Output Power Efficiency Estimate at output terminals. Under 0.7 if no better data available Z Factor. Ratio of secondary side losses to the total losses in the power supply. Use 0.5 if no better data available Bridge Rectifier Conduction Time Estimate Input Capacitance nH/turn^ Select package (PG, GG or DG) Minimum Current Limit Typical Current Limit Maximum Current Limit Typical Device Switching Frequency at maximum power LinkSwitch-II on-state Drain to Source Voltage Output Winding Diode Forward Voltage Drop Output diode conduction time LinkSwitch-II On-time (calculated at minimum inductance) LinkSwitch-II dead time when both the switch and diode are NOT conducting (calculated at minimum inductance) Enter Transformer Core Generic EE10_BOBBIN Core Effective Cross Sectional Area Core Effective Path Length Ungapped Core Effective Inductance Bobbin Physical Winding Width Minimum Inductance (Includes inductance of input and output winding) Typical inductance (Includes inductance of input and output winding) Tolerance in inductance Total number of turns (Includes input and output winding turns). To adjust Total number of turns change BM_TARGET Gapped Core Effective Inductance Page 14 of 32 10-Sep-08 DER-186 – 12 V, 350 mA LED Driver 2750.00 2741.75 2 Gauss Gauss BP 3217.79 Gauss BAC 1370.87 Gauss ur LG INDUCTOR_RATIO mm 0.215 145.90 0.17 0.22 31 31.00 BM_TARGET BM 2750 Input Section NL_INPUT AWG L CMA Info 3.92 850.79 Output Section NL_OUTPUT AWG_OUTPUT 27.00 32 L_OUTPUT CMA_OUTPUT 32.00 Info 0.99 100.76 CURRENT WAVEFORM SHAPE PARAMETERS DMAX IAVG IP ID_PK ISW_RMS ID_RMS IL_RMS IL_TAP_RMS IR 0.38 0.06 0.30 1.59 0.09 0.64 0.09 0.64 0.30 A A A A A A A A FEEDBACK WINDING PARAMETERS NFB VFLY VFOR 27.00 12.00 16.40 V V RUPPER RLOWER 49.03 9.81 k-ohm k-ohm VOLTAGE STRESS PARAMETERS VDRAIN 529.88 V PIVS 81.60 V Page 15 of 32 Target Flux Density Maximum Operating Flux Density (calculated at nominal inductance), BM < 3000 is recommended Peak Operating Flux Density (calculated at maximum inductance and max current limit), BP < 3300 is recommended AC Flux Density for Core Loss Curves (0.5 X Peak to Peak) Relative Permeability of Ungapped Core Gap Length (LG > 0.1 mm) Ratio of Output windng turns to Total inductor turns. Adjust ratio to ensure discontinuous operation Section of winding that conducts only during ON time of the LINKSwitch-II Number of turns in Input section. Primary Wire Gauge (Rounded to next smaller standard AWG value) Number of Layers (Input section) !!! Info. CMA is on the higher side of recommendation but design will work. Consider increasing AWG Section of winding that conducts both when the Linkswitch-II is ON and OFF. Number of Turns in Output winding. To adjust number of turns change INDUCTOR_RATIO Output Winding Wire Gauge (Rounded to next smaller standard AWG value) Number of Layers (Output winding) !!! Info. CMA is less than 200 and may cause overheating of the primary winding. This maybe acceptable if number of turns is low. Reduce AWG_OUTPUT Maximum duty cycle measured at VMIN Input Average current Peak primary current Switch RMS current Freewheeling Diode RMS current Inductor - Input section RMS current Inductor - Output winding section RMS current Primary ripple current Feedback winding turns Voltage across diode at turn off Voltage across Output winding of inductor when switch is on. Upper resistor in Feedback resistor divider Lower resistor in resistor divider Maximum Drain Voltage Estimate (Assumes 100 V leakage spike) Output Rectifier Maximum Peak Inverse Voltage Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-186 – 12 V, 350 mA LED Driver 10-Sep-08 10 Performance Data All measurements performed at room temperature, 60 Hz input frequency. 10.1 Efficiency with LED Load – Full Load This data was taken using three 350 mA, 3.5 V LEDs connected in a series string. Full Load Efficiency 85 80 Efficiency (%) 75 70 65 60 55 50 85 115 145 175 205 235 265 Input Voltage (Vac) Figure 7 – Full-load Efficiency vs Input Voltage. Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Page 16 of 32 10-Sep-08 DER-186 – 12 V, 350 mA LED Driver 10.2 No-load Input Power 200 Input Power (mW) 160 120 80 40 0 85 115 145 175 205 235 Input Voltage (VAC) Figure 8 – No-load Power Consumption. Page 17 of 32 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com 265 DER-186 – 12 V, 350 mA LED Driver 10-Sep-08 10.3 Output Characteristics The output voltage and current were measured at the board. This data was taken at room temperature. 14 Output Voltage (VDC) 12 10 8 115 VAC 230 VAC 6 4 2 0 0 50 100 150 200 250 300 350 400 Output Current (mA) Figure 9 – Output Characteristic. 10.4 Thermal Performance Thermal performance was measured by putting the power supply inside a plastic enclosure. The enclosure was placed inside a box, protected from air flow. An ambient thermal probe was placed about 1 inch away from the enclosure, not touching anything. A thermocouple was soldered to U1 at the Source Pin, and another was soldered to D1. A third thermocouple was taped to T1. Results: Input Voltage Ambient U1 T1 D1 85 VAC 50.5 °C 86.8 °C 72.3 °C 74.8 °C Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com 265 VAC 50.5 °C 91.9 °C 74.2 °C 73.9 °C Page 18 of 32 10-Sep-08 DER-186 – 12 V, 350 mA LED Driver 10.5 Output Ripple Measurements 10.5.1 Ripple Measurement Technique For DC output ripple measurements, use a modified oscilloscope test probe to reduce spurious signals. Details of the probe modification are provided in figures below. Tie two capacitors in parallel across the probe tip of the 4987BA probe adapter. Use a 0.1 µF/50 V ceramic capacitor and a 1.0 µF/50 V aluminum-electrolytic capacitor. The aluminum-electrolytic capacitor is polarized, so always maintain proper polarity across DC outputs. Probe Ground Probe Tip Figure 10 – Oscilloscope Probe Prepared for Ripple Measurement. (End Cap and Ground Lead Removed) Figure 11 – Oscilloscope Probe with Probe Master 4987BA BNC Adapter. (Modified with wires for probe ground for ripple measurement, and two parallel decoupling capacitors added) Page 19 of 32 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-186 – 12 V, 350 mA LED Driver 10-Sep-08 10.5.2 Measurement Results Figure 12 – Output Ripple and Noise at 115 VAC Input with LED Load. Figure 13 – Output Ripple and Noise at 230 VAC Input with LED Load. Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Page 20 of 32 10-Sep-08 DER-186 – 12 V, 350 mA LED Driver 11 Output Current Ripple 11.1 Load Current Ripple The following oscillograms show the AC component in the load current. LEDs were used as the load. Figure 14 – Output Current Ripple at 115 VAC Input. Current: 10 mA/div, 10 µs/div. Figure 15 – Output Current Ripple at 230 VAC. Current: 10 mA/div, 10 µs/div. Page 21 of 32 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-186 – 12 V, 350 mA LED Driver 10-Sep-08 11.2 Inductor Current The inductor current over the entire switching cycle is shown in the following four oscillograms. 3 series-connected LEDs were used as the load. At turn off the current in the inductor increases by a factor of 4.6 (corresponding to the turns ratio). Figure 16 – Inductor Current at 85 VAC. 0.5 A/div. Figure 17 – Inductor Current at 85 VAC. 0.5 A/div. Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Page 22 of 32 10-Sep-08 DER-186 – 12 V, 350 mA LED Driver Figure 18 – Inductor Current at 265 VAC. 0.5 A/div. Figure 19 – Inductor Current at 265 VAC. 0.5 A/div. Page 23 of 32 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-186 – 12 V, 350 mA LED Driver 10-Sep-08 12 Waveforms 12.1 Output Voltage Startup Profile Figure 20 – Output Voltage at Startup (115 VAC Input), Full Load. 2 V/div and 10 ms/div. Figure 21 – Output Voltage at Startup (230 VAC Input), Full Load. 2 V/div and 10 ms/div. Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Page 24 of 32 10-Sep-08 DER-186 – 12 V, 350 mA LED Driver 12.2 Output Current Startup Profile Figure 22 – LED Current at Startup (115 VAC), Full Load. 100 mA/div and 10 ms/div. Figure 23 – LED Current at Startup (230 VAC), Full Load. 100 mA/div and 10 ms/div. Page 25 of 32 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-186 – 12 V, 350 mA LED Driver 10-Sep-08 12.3 Drain Voltage and Current Figure 24 – Drain Voltage at 85 VAC Input. Current: 0.2 A/div. Figure 25 – Drain Voltage at 265 VAC Input. Current: 0.2 A/div. Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Page 26 of 32 10-Sep-08 DER-186 – 12 V, 350 mA LED Driver Figure 26 – Drain Voltage During Startup at 265 VAC. 100 V/div and 10 ms/div. Page 27 of 32 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-186 – 12 V, 350 mA LED Driver 10-Sep-08 13 Transient Protection Energy Star line-transient protection requires immunity to 7 strikes of a 100 kHz ring wave, 2.5 kV level, for both common mode and differential mode. The following tests were performed at 230 VAC input, at both 90 ° and 270 ° phase. Differential Mode Phase Voltage Current Results 90 Degree 2.5 kV 500 A Pass 270 Degree 2.5 kV 500 A Pass Phase Voltage Current Results 90 Degree 2.5 kV 500 A Pass 270 Degree 2.5 kV 500 A Pass Common Mode Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Page 28 of 32 10-Sep-08 DER-186 – 12 V, 350 mA LED Driver 14 Conducted EMI Figure 27 – Conducted EMI at 115 VAC, Output Floating. EN55015B Limits. Page 29 of 32 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-186 – 12 V, 350 mA LED Driver 10-Sep-08 Figure 28 – Conducted EMI at 230 VAC, Output Floating. EN55015B Limits. Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Page 30 of 32 10-Sep-08 DER-186 – 12 V, 350 mA LED Driver 15 Revision History Date 15-May-08 10-Sep-08 Page 31 of 32 Author SGK SGK Revision 1.0 1.1 Description & changes Initial Release Updated Schematic Reviewed JD KM Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-186 – 12 V, 350 mA LED Driver 10-Sep-08 For the latest updates, visit our website: www.powerint.com Power Integrations reserves the right to make changes to its products at any time to improve reliability or manufacturability. Power Integrations does not assume any liability arising from the use of any device or circuit described herein. POWER INTEGRATIONS MAKES NO WARRANTY HEREIN AND SPECIFICALLY DISCLAIMS ALL WARRANTIES INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, AND NON-INFRINGEMENT OF THIRD PARTY RIGHTS. PATENT INFORMATION The products and applications illustrated herein (including transformer construction and circuits external to the products) may be covered by one or more U.S. and foreign patents, or potentially by pending U.S. and foreign patent applications assigned to Power Integrations. A complete list of Power Integrations’ patents may be found at www.powerint.com. Power Integrations grants its customers a license under certain patent rights as set forth at http://www.powerint.com/ip.htm. The PI Logo, TOPSwitch, TinySwitch, LinkSwitch, DPA-Switch, PeakSwitch, EcoSmart, Clampless, E-Shield, Filterfuse, StackFET, PI Expert and PI FACTS are trademarks of Power Integrations, Inc. Other trademarks are property of their respective companies. ©Copyright 2008 Power Integrations, Inc. Power Integrations Worldwide Sales Support Locations WORLD HEADQUARTERS 5245 Hellyer Avenue San Jose, CA 95138, USA. Main: +1-408-414-9200 Customer Service: Phone: +1-408-414-9665 Fax: +1-408-414-9765 e-mail: [email protected] GERMANY Rueckertstrasse 3 D-80336, Munich Germany Phone: +49-89-5527-3911 Fax: +49-89-5527-3920 e-mail: [email protected] JAPAN Kosei Dai-3 Bldg., 2-12-11, Shin-Yokohama, Kohoku-ku, Yokohama-shi, Kanagawa 222-0033 Phone: +81-45-471-1021 Fax: +81-45-471-3717 e-mail: [email protected] TAIWAN 5F, No. 318, Nei Hu Rd., Sec. 1 Nei Hu Dist. Taipei, Taiwan 114, R.O.C. Phone: +886-2-2659-4570 Fax: +886-2-2659-4550 e-mail: [email protected] CHINA (SHANGHAI) Rm 1601/1610, Tower 1, Kerry Everbright City No. 218 Tianmu Road West, Shanghai, P.R.C. 200070 Phone: +86-21-6354-6323 Fax: +86-21-6354-6325 e-mail: [email protected] INDIA #1, 14th Main Road Vasanthanagar Bangalore-560052 India Phone: +91-80-41138020 Fax: +91-80-41138023 e-mail: [email protected] KOREA RM 602, 6FL Korea City Air Terminal B/D, 159-6 Samsung-Dong, KangnamGu, Seoul, 135-728, Korea Phone: +82-2-2016-6610 Fax: +82-2-2016-6630 e-mail: [email protected] UNITED KINGDOM 1st Floor, St. James’s House East Street, Farnham Surrey, GU9 7TJ United Kingdom Phone: +44 (0) 1252-730-141 Fax: +44 (0) 1252-727-689 e-mail: [email protected] CHINA (SHENZHEN) Rm A, B & C 4th Floor, Block C, Electronics Science and Technology Building, 2070 Shennan Zhong Rd, Shenzhen, Guangdong, China, 518031 Phone: +86-755-8379-3243 Fax: +86-755-8379-5828 e-mail: [email protected] ITALY Via De Amicis 2 20091 Bresso MI – Italy Phone: +39-028-928-6000 Fax: +39-028-928-6009 e-mail: [email protected] SINGAPORE 51 Newton Road, #15-08/10 Goldhill Plaza, Singapore, 308900 Phone: +65-6358-2160 Fax: +65-6358-2015 e-mail: [email protected] APPLICATIONS HOTLINE World Wide +1-408-414-9660 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com APPLICATIONS FAX World Wide +1-408-414-9760 Page 32 of 32