Design Example Report Title 75 W Single Output, Power-factor Corrected LED Driver Using TOP250YN Specification 208 VAC – 277 VAC Input 24 V, 3.1 A Output Application LED Driver Author Power Integrations Applications Department Document Number DER-136 Date April 1, 2008 Revision 1.6 Summary and Features • Single stage PFC based constant voltage, constant current output power supply • 208 to 277 VAC input range. • Average efficiency (over input range) at full load >85% • Meets ENERGY STAR minimum PF requirement of 0.9 for commercial environment (0.9 worst case at 277 VAC) • Meets harmonic content limits as specified in IEC 61000-3-2 for Class C • Meets EN55015 B conducted EMI limits with >10 dBµV margin • Fully fault protected • Auto-restart withstands shorted output indefinitely • Integrated thermal shutdown protects the entire supply • Operates with no-load indefinitely • Full load: 6 rows of 4 diodes part# LW W5SG/GYHY-5K8L-Z The products and applications illustrated herein (including circuits external to the products and transformer construction) 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 5245 Hellyer Avenue, San Jose, CA 95138 USA. Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-136 75 W Single Output, LED Driver – TOP250YN 1-Apr-2008 Table of Contents 1 2 3 4 5 Introduction.................................................................................................................4 Power Supply Specification ........................................................................................5 Schematic...................................................................................................................6 PCB Layout ................................................................................................................7 Circuit Description ......................................................................................................8 5.1 Input EMI Filtering ...............................................................................................8 5.2 TOPSwitch Primary .............................................................................................8 5.3 Output Rectification .............................................................................................9 5.4 Output Feedback.................................................................................................9 5.4.1 Constant-Voltage Operation.........................................................................9 5.4.2 Constant-Current Operation .......................................................................10 5.5 Soft-Start ...........................................................................................................10 5.6 Post Filter ..........................................................................................................11 6 Bill of Materials .........................................................................................................12 7 Transformer Specification.........................................................................................14 7.1 Electrical Diagram .............................................................................................14 7.2 Electrical Specifications.....................................................................................14 7.3 Materials............................................................................................................14 7.4 Transformer Build Diagram ...............................................................................15 7.5 Transformer Construction..................................................................................16 8 Transformer Spreadsheets .......................................................................................17 9 Specifications For Common Mode Inductor L1.........................................................19 9.1 Electrical Diagram. ............................................................................................19 9.2 Inductance.........................................................................................................19 9.3 Material..............................................................................................................19 9.4 Winding Instructions. .........................................................................................19 10 Performance Data.................................................................................................21 10.1 Efficiency ...........................................................................................................21 10.2 Output Characteristic.........................................................................................22 10.3 Harmonic Content .............................................................................................23 10.4 Harmonic Content in Percentage of Fundamental.............................................23 10.5 Power Factor Vs Line Voltage at Full Load .......................................................24 11 Thermal Performance ...........................................................................................25 12 Waveforms............................................................................................................26 12.1 Drain Voltage and Current, Normal Operation...................................................26 12.2 Output Voltage Start-up Profile..........................................................................27 12.3 Drain Voltage and Current Start-up Profile ........................................................27 12.4 Output Ripple Measurements............................................................................28 12.4.1 Ripple Measurement Technique ................................................................28 12.4.2 Measurement Results ................................................................................29 13 Control Loop Analysis ...........................................................................................30 14 Surge Test ............................................................................................................32 14.1 Surge Test Results with 1.2/50µs Waveform ....................................................32 14.2 Surge Test Results with 0.5µs-100 kHz Ring-Waveform...................................32 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Page 2 of 36 1-Apr-2008 15 16 DER-136 75 W Single Output, LED Driver – TOP250YN Conducted EMI .....................................................................................................33 Revision History ....................................................................................................34 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. Page 3 of 36 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-136 75 W Single Output, LED Driver – TOP250YN 1-Apr-2008 1 Introduction The document presents a power supply design for LED Lighting applications. The design input voltage range is 208 to 277 VAC. The supply employs a single stage power-factor corrected circuit to generate a 24 V, 3 A output and meets the Energy Star minimum pf requirement of 0.9 for commercial applications with a high efficiency of 84%. This document contains the power supply specification, schematic, bill of materials, transformer documentation, printed circuit layout, and performance data for this design. Figure 1 – Populated Circuit Board Photograph. Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Page 4 of 36 1-Apr-2008 DER-136 75 W Single Output, LED Driver – TOP250YN 2 Power Supply Specification Description Symbol Min Typ Max Units Comment Input Voltage Frequency VIN fLINE 208 47 277 64 VAC Hz 2 Wire – no P.E. 50/60 Output Output Voltage 1 VOUT1 24 28 V 20 MHz Bandwidth Output Current 1 Total Output Power Continuous Output Power IOUT1 3.1 POUT A 75 W Environmental Conducted EMI Meets EN55015B Designed to meet IEC950, UL1950 Class II Safety Surge 1 kV Surge 0.5 kV Ring-wave 2.5 kV Ambient Temperature Page 5 of 36 TAMB 0 50 o C 1.2/50 µs Surge, IEC 61000-4-5, Series Impedance: Common Mode: 12 Ω 1.2/50 µs Surge, IEC 61000-4-5, Series Impedance: Differential Mode: 2 Ω 0.5 µs-100KHz Ring-wave IEEE C.62.41-1991, Class A, Differential and Common Mode Free Convection, Sea Level Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-136 75 W Single Output, LED Driver – TOP250YN 1-Apr-2008 3 Schematic Figure 2 – Schematic. Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Page 6 of 36 1-Apr-2008 DER-136 75 W Single Output, LED Driver – TOP250YN 4 PCB Layout Figure 3 – PCB Layout. Page 7 of 36 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-136 75 W Single Output, LED Driver – TOP250YN 1-Apr-2008 5 Circuit Description This design uses a discontinuous mode flyback power supply configuration, fed with minimum capacitance at the input. Using a fixed duty-cycle over an AC line cycle allows the peak drain current envelope, and therefore the input current, to follow the input AC voltage waveform to give high power factor and low harmonic content. Although this simple configuration gives both output regulation and power factor correction in a single stage converter, it does require higher peak drain currents compared to a standard power supply with substantiation input capacitance. Detailed descriptions of each functional block are given below. 5.1 Input EMI Filtering In addition to the standard filtering (X capacitors C1 and C2 and common-mode inductor L2), L3 and L4 were added to provide increased differential-mode filtering and surge immunity. This was required due to the small value of input capacitance (C3) and the associated increase in switching currents seen by the AC input. Resistors R1 and R2 reduce high-frequency conducted and radiated EMI. Common-mode inductor L1 filters very high frequency common-mode noise. Common-mode filtering is provided by L1, L2 and Y-capacitor C9. Together with transformer E-Shields (that reduce the source of common mode EMI currents), this allows the design to pass EN55015 B limits with greater than 10 dB of margin. 5.2 TOPSwitch Primary On application of the AC input, the combination of the in-rush current to charge C1, C2 and C3, together with the parasitic inductance in the AC line, causes a voltage spike that appears across C3. In a design with a large input capacitance, this voltage rise is negligible; however, in this case the voltage spike on C3 is sufficiently large to exceed the BVDSS rating of the MOSFET within TOP250YN (U1). To prevent this, capacitor C4 and diode D5 limit the maximum voltage across the DC bus while R3 is the bleeder to discharge capacitor C4 on AC removal. The discontinuous mode of operation needed for high power factor increases the primary RMS current for a given output power. Selecting a larger TOPSwitch device (TOP250YN) than needed for power delivery offsets increases in RMS current (due to DCM operation) by reducing the RDSON related conduction losses thereby giving higher efficiency and reduced dissipation. As the DC input voltage across C3 falls to zero during normal operation, D6 was added in series with the drain to prevent the DRAIN ringing below SOURCE and reverse biasing the device. As reverse biasing of the device is not permitted, this diode must be used. Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Page 8 of 36 1-Apr-2008 DER-136 75 W Single Output, LED Driver – TOP250YN To provide a high power factor using a single-stage flyback converter, the MOSFET’s duty cycle must be kept constant over a single AC line cycle (low bandwidth). In the TOPSwitch-GX the operating duty cycle is a function of the control pin current. This requires that the current into the C pin be held constant to achieve power factor correction. The simplest way to achieve this would be to use a very large value for the CONTROL pin capacitance (C5). However, a large value of C5 causes a large startup time and a large startup overshoot. To overcome this difficulty, an emitter follower (Q1) was used as an impedance transformer with a capacitor C10 in its base. Looking into the emitter of Q1, C10 appears to be larger (C10 x Q1hfe), and R6 appears to be smaller (R6 / Q1hfe). Capacitor C10, together with R6, sets the dominant pole of the circuit at approximately 0.02 Hz. Resistor R7 provides loop compensation, creating a zero at approximately 200 Hz, which gives additional phase starting at 20 Hz to improve phase margin at gain crossover. Gain crossover occurred in this design at approximately 35 – 40 Hz. Higher bandwidth is undesirable as this degrades power factor by increasing the third harmonic content in the input current waveform. Diode D8 prevents reverse current through Q1 during startup. Feedback is provided from the secondary via optocoupler U2B, which in turn modulates the base voltage of Q1 and changes the current into the CONTROL pin. The primary clamp circuit is formed by D7, R4, R5, C6, and VR1. During normal operation R5 and C6 set the clamping voltage. Zener VR1 sets a defined upper clamping voltage and conducts only during startup and load transients. A fast recovery (250 ns) blocking diode, D7, was used to recover some of the leakage energy, thereby improving efficiency. Resistor R4 dampens high frequency ringing and improves EMI performance. 5.3 Output Rectification To reduce power dissipation and increase efficiency, two output diodes were used (D10 and D11). These are connected to separate secondary windings to improve current sharing between the two diodes. Filtering is provided by C11 and C12. Relatively large values are necessary to reduce line frequency ripple present in the output due to the low loop bandwidth required to achieve a high power factor. These values may be reduced depending on the acceptable current ripple through the LED load. 5.4 Output Feedback The output feedback is split into two functional blocks: constant-voltage (CV) operation and constant-current (CC) operation. 5.4.1 Constant-Voltage Operation Voltage feedback is provided by VR2 and optocoupler U2A. Once the output exceeds the voltage defined by the forward drop of U2A, VR2 and R16, current flows through the optocoupler and provides feedback to the primary. As the line and load change, the Page 9 of 36 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-136 75 W Single Output, LED Driver – TOP250YN 1-Apr-2008 magnitude of current changes to reduce or increase the MOSFET duty cycle which maintains output regulation. Resistor R16 sets the loop gain in the constant-voltage region. The nominal output voltage regulation is set at 28 V, which is above the expected LED load voltage (when operated at its rated current). Under normal operation, the supply operates in constant-current mode, and voltage feedback is used only when the output is unloaded. 5.4.2 Constant-Current Operation Transistor Q3 and the forward drop of the LED in U2A are used to create a bias voltage on the base on Q2. The additional drop across R11, R12, and R13 needed to turn on Q2 is equal to the difference between the bias voltage and the VBE of Q2 (~0.5 V). Once Q2 begins to conduct, Q4 also conducts, supplying current through U2A and providing feedback. Resistor R9 limits the base current from Q4, and R14 sets the gain of the CC loop. Resistor R10 keeps Q4 off until Q2 is on, while C13 provides loop compensation. This arrangement gave an average output current in CC operation of 3.1 A. 5.5 Soft-Start The very low loop bandwidth presents a problem at startup. Once the loop closes and feedback is provided via U2A, it takes significant time for the loop to respond and therefore allows significant output overshoot. This is because C10 must charge above 5.8 V before current is supplied into the CONTROL pin of U1. The standard solution to output overshoot is to provide a soft-finish circuit. Typically this consists of a capacitor that allows current to flow in the feedback loop before the output has reached regulation. Here such a passive approach is not practical because of the capacitor size required. To overcome this, the circuit formed around transistor Q5 is used to overdrive the feedback loop during startup. Using an element with gain (Q5) allows enough feedback current to pre-charge C10 before the output reaches regulation. A separate auxiliary supply is created by D12 and C15 so that the voltage across C15 rises faster than the main output across C11 and C12. While C16 charges, Q5 is on, supplying current to charge C10 via the optocoupler, with resistor R21 limiting the maximum current. Once the voltage across C16 reaches VO-VBE (Q5), Q5 turns off and the circuit becomes inactive. At power down, C16 is discharged via R18, resetting the circuit for the next power-up. The time constant of C16 and R18 appears very long; however, in practice, C10 also takes a significant time to discharge on power down, and even momentary AC drop outs do not result in any output overshoot. Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Page 10 of 36 1-Apr-2008 DER-136 75 W Single Output, LED Driver – TOP250YN 5.6 Post Filter A post filter consisting of L5 and C17 was added to reduce switching frequency ripple on the output. This also improves noise immunity and improves the reliability of the CC setpoint. Page 11 of 36 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-136 75 W Single Output, LED Driver – TOP250YN 1-Apr-2008 6 Bill of Materials Item Qty 1 2 2 3 1 1 Part Ref. C1 C2 C3 C4 Description Mfg Part Number Mfg 100 nF, 305 VAC, X2 B32922A2104M Epcos 220 nF, 630 V, Film 15 µF, 450 V, Electrolytic, (12.5 x 25) ECQ-E6224KF EKXG451ELL150MK25S Panasonic Nippon Chemi-Con 4 1 C5 22 µF, 16 V, Electrolytic, Gen. Purpose, (5 x 11) ECA-1CM220 Panasonic 5 1 C6 2.2 nF, 1 kV, Disc Ceramic NCD222K1KVY5FF NIC Components Corp 6 1 C7 330 µF, 25 V, Electrolytic, Very Low ESR, 53 m, (10 x 12.5) EKZE250ELL331MJC5S Nippon Chemi-Con 7 8 1 1 C9 C10 2.2 nF, Ceramic, Y1 33 µF, 16 V, Electrolytic, Gen. Purpose, (5 x 11) 440LD22-R ECA-1CM330 Vishay Panasonic 9 2 C11 C12 1800 uF, 35 V, Electrolytic, Very Low ESR, 16 mΩ, (16 x 25) EKZE350ELL182ML25S Nippon Chemi-Con 10 11 12 1 1 2 C13 C14 C15 C16 10 nF, 50 V, Ceramic, Z5U 100 nF, 50 V, Ceramic, Z5U 47 µF, 35 V, Electrolytic, Gen. Purpose, (5 x 11) B37982N5103M000 SR205E104MAR EKMG350ELL470ME11D Epcos AVX Corp Nippon Chemi-Con 13 1 C17 150 µF, 35 V, Electrolytic, Very Low ESR, 72 Ω, (8 x 11.5) EKZE350ELL151MHB5D Nippon Chemi-Con 14 4 1000 V, 2 A, Rectifier, DO-15 RL207 Rectron 15 16 1 1 D1 D2 D3 D4 D5 D6 1000 V, 1 A, Rectifier, DO-41 400 V, 9 A, Ultrafast Recovery, 60 ns, TO-220AC 1N4007-E3/54 BYV29-400 Vishay NXP Semiconductors 17 1 D7 600 V, 3 A, Fast Recovery Diode, DO-201AD FR305-T Diodes Inc. 18 19 1 2 75 V, 300 mA, Fast Switching, DO-35 200 V, 1 A, Rectifier, DO-41 1N4148 1N4003RLG Vishay OnSemi 20 2 D8 D9 D12 D10 D11 150 V, 20 A, Schottky, TO-220AB DSSK 20-015A IXYS 21 22 1 2 F1 HS1 HS2 5 A, 250V, Slow, TR5 HEATSINK, Alum, TO-220 2 hole, 2 mtg pins 3721500041 Wickman Custom 23 2 J1 J2 2 Position (1 x 2) header, 0.156 pitch, Vertical 26-48-1021 Molex 24 1 L1 42 uH, Common Mode Inductor, 4 Pins, Toroid 5943000201 Fair-Rite Toroid 25 26 27 28 1 2 1 3 L2 L3 L4 L5 Q1 Q2 Q3 19 mH, 0.5 A, Common Mode Choke 330 uH, 0.55 A, 9 x 11.5 mm 2.2 uH, 6.0 A NPN, Small Signal BJT, 40 V, 0.2 A, TO-92 ELF15N005A SBC3-331-551 RFB0807-2R2L 2N3904RLRAG Panasonic Tokin Coilcraft On Semiconductor 29 2 Q4 Q5 PNP, Small Signal BJT, 40 V, 0.2 A, TO-92 2N3906 Fairchild Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Page 12 of 36 1-Apr-2008 DER-136 75 W Single Output, LED Driver – TOP250YN 30 2 R1 R2 5.1 kΩ, 5%, 1/4 W, Carbon Film CFR-25JB-5K1 Yageo 31 32 33 34 35 36 37 38 39 40 1 1 1 1 1 1 1 1 1 2 150 kΩ, 5%, 1/2 W, Carbon Film 22 Ω, 5%, 1 W, Metal Oxide 100 kΩ, 5%, 2 W, Metal Oxide 300 kΩ, 5%, 1/8 W, Carbon Film 24 Ω, 5%, 1/8 W, Carbon Film 22 Ω, 5%, 1/8 W, Carbon Film 150 Ω, 5%, 1/8 W, Carbon Film 10 kΩ, 5%, 1/8 W, Carbon Film 0.13 Ω, 1%, 3 W 1 Ω, 5%, 1/4 W, Carbon Film CFR-50JB-150K RSF100JB-22R RSF200JB-100K CFR-12JB-300K CFR-12JB-24R CFR-12JB-22R CFR-12JB-150R CFR-12JB-10K ALSR-3F-.13-1% CFR-25JB-1R0 Yageo Yageo Yageo Yageo Yageo Yageo Yageo Yageo Huntington Electric Yageo 41 42 1 2 470 Ω, 5%, 1/8 W, Carbon Film 1 kΩ, 5%, 1/8 W, Carbon Film CFR-12JB-470R CFR-12JB-1K0 Yageo Yageo 43 2 200 Ω, 5%, 1/8 W, Carbon Film CFR-12JB-200R Yageo 44 45 46 47 48 49 50 51 1 1 1 1 1 1 1 1 R3 R4 R5 R6 R7 R8 R9 R10 R11 R12 R13 R14 R15 R22 R16 R20 R17 R18 R19 R21 R23 RV1 T1 U1 CFR-12JB-1K6 CFR-12JB-100K CFR-12JB-10R CFR-12JB-300R MFR-25FBF-10K2 V320LA10 BEER-28-111-CP TOP250YN Yageo Yageo Yageo Yageo Yageo Littlefuse TDK Power Integrations 52 1 U2 LTV-817A Liteon 53 1 VR1 1.6 kΩ, 5%, 1/8 W, Carbon Film 100 kΩ, 5%, 1/8 W, Carbon Film 10 Ω, 5%, 1/8 W, Carbon Film 300 Ω, 5%, 1/8 W, Carbon Film 10.2 kΩ, 1%, 1/4 W, Metal Film 320 V, 48 J, 10 mm, RADIAL Bobbin, EER28, Vertical, 10 pins TOPSwitch-GX, TOP250YN, TO2207C Opto coupler, 35 V, CTR 80-160%, 4-DIP 200 V, 5 W, 5%, TVS, DO204AC (DO-15) P6KE200ARLG OnSemi 54 1 VR2 27 V, 5%, 500 mW, DO-35 1N5254B Microsemi All parts are RoHS compliant. Page 13 of 36 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-136 75 W Single Output, LED Driver – TOP250YN 1-Apr-2008 7 Transformer Specification 7.1 Electrical Diagram WD4 WD6 Shield Shield WD1 Core Cancellation 1 2nd WD7 half Primary 8 10 WD5 Secondary 3 WD2 1st half Primary 6 7 2 4 WD3 Bias 5 Figure 4 – Transformer Electrical Diagram. 7.2 Electrical Specifications Electrical Strength Primary Inductance Resonant Frequency Primary Leakage Inductance 7.3 60 second, 60 Hz, from Pins 1-5 to Pins 6-10. Pins 1-2, all other windings open, measured at 100 kHz. Pins 1-2, all other windings open. Pins 1-2, with Pins 6-7-8-9-10 shorted, measured at 100 kHz. 3000 VAC 171 µH, -0/+10% 1290 kHz (Min.) 3 µH (Max.) Materials Item [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] Description Core: EER28 PC40 or equivalent gapped for 248 nH/T2 Bobbin: Vertical EER28 10 pins, safety rated Magnet Wire: 26AWG Magnet Wire: 25AWG Magnet Wire: 28AWG Copper foil: 14 mm wide Triple Insulated Wire: 28AWG Tape: 14.7 mm Tape: 16.7mm Varnish 2 mm Polyester web tape Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Page 14 of 36 1-Apr-2008 7.4 DER-136 75 W Single Output, LED Driver – TOP250YN Transformer Build Diagram Pins Side WD7: 1 3 13T x 2 _ #25 AWG WD6: 1 1T Copper Foil 6 7 8 WD5: 10 WD4: WD3: WD2: 6T x 4 _ #28 TIW 1T Copper Foil (reversed winding) 1 4 3T x 4 _ #28 AWG 5 3 (scattered) 13T x 2 _ #25 AWG 2 9T x 3 _ #26 AWG WD1: 1 2mm margin tape Figure 5 – Transformer Build Diagram. Copper Foil Wrapped in Tape Finish Side Starting Lead Connected to Pin 1 Figure 6 – Copper Tape Preparation for Winding 4. Copper Foil Wrapped in Tape Starting Side Finish Lead Connected to Pin 1 Figure 7 – Copper Tape Preparation for Winding 6. Page 15 of 36 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-136 75 W Single Output, LED Driver – TOP250YN 7.5 1-Apr-2008 Transformer Construction Bobbin Preparation WD1 Core Cancellation Tape WD2 First Half Primary Tape WD3 Bias Tape WD4 Shield Tape WD5 Secondary Tape WD6 Shield Tape WD7 Second Half Primary Tape Final Assembly Place bobbin, item [2], on the winding machine with pins side oriented to the left hand side. Use 2 mm Polyester web tape [11] on left hand side to meet safety creepage distances. Start at pin 1, wind from left to right 9 trifilar turns of item [3] in a uniform, tightly wound layer. Cut finish lead at the end of the winding. Use 1 layer of tape, item [8], to hold the winding. Start at pin 2, wind from left to right 13 bifilar turns of item [4] in a uniform, tightly wound layer. Finish at pin 3. Use 1 layer of tape, item [8], to hold the winding. Start at pin 5, wind 3 quad-filar turns of item [5] from left to right in a single scattered layer. Finish at pin 4. Use 1 layer of tape, item [8], to hold the winding. Prepare copper tape, item [6], as shown in figure 6. Connect starting lead to pin 1. Wind 1 turn in reverse winding direction. The finish lead is left unconnected. Use 1 layer of tape, item [8], to hold the winding. Start at pins 10 and 8, Wind from left to right 6 turns of 4 wires in parallel, item [7], in a uniform layer. Finish on pins 7 and 6. Use 1 layer of tape, item [8], to hold the winding. Prepare copper tape, item [6], as shown in figure 7. Starting lead is left unconnected. Wind 1 turn and connect finish lead to pin 1. Use 1 layer of tape, item [8], to hold the winding. Start at pin 3, wind from left to right 13 bifilar turns of item [4] in a uniform, tightly wound layer. Finish at pin 1. Use 3 layers item, [9] as insulation. Assemble and secure core halves with bobbin. Varnish impregnate item [10]. Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Page 16 of 36 1-Apr-2008 DER-136 75 W Single Output, LED Driver – TOP250YN 8 Transformer Spreadsheets The standard flyback transformer design approach was modified due to the minimal input capacitance for high power-factor (PF). A very high capacitance value was entered for CIN so the design uses the transformer at the peak of the AC line voltage (at low line). The output power entered was increased from the 75 W specified to 119 W. This was to compensate for the under-delivery of output power when the AC input voltage waveform is low. ACDC_TOPSwitchGX_ INPUT 043007; Rev.2.15; Copyright Power Integrations 2007 ENTER APPLICATION VARIABLES VACMIN 208 INFO OUTPUT UNIT TOP_GX_FX_043007: TOPSwitch-GX/FX Continuous/Discontinuous Flyback Transformer Design Spreadsheet Volts LED DRIVER XFR Minimum AC Input Voltage Maximum AC Input Voltage VACMAX 277 Volts fL 50 Hertz AC Mains Frequency VO 26.00 Volts Output Voltage (main) PO 119.00 Watts Output Power n 0.78 Z 0.50 VB 12 tC 3.00 CIN Efficiency Estimate Loss Allocation Factor Volts 99999.00 ENTER TOPSWITCH-GX VARIABLES TOP-GX TOP250 Chosen Device KI TOP250 Power Out uFarads Input Filter Capacitor Universal 115 Doubled/230V 210W 290W 3.969 Amps External Ilimit reduction factor (KI=1.0 for default ILIMIT, KI <1.0 for lower ILIMIT) Use 1% resistor in setting external ILIMIT 4.851 Amps 0.70 ILIMITMIN ILIMITMAX Frequency (F)=132kHz, (H)=66kHz fS Bias Voltage mSeconds Bridge Rectifier Conduction Time Estimate F Use 1% resistor in setting external ILIMIT Full (F) frequency option – 132kHz 132000 Hertz fSmin 124000 Hertz TOPSwitch-GX Switching Frequency: Choose between 132 kHz and 66 kHz TOPSwitch-GX Minimum Switching Frequency fSmax 140000 Hertz TOPSwitch-GX Maximum Switching Frequency VOR 116.00 Volts Reflected Output Voltage VDS 10.00 Volts TOPSwitch on-state Drain to Source Voltage VD 0.50 Volts Output Winding Diode Forward Voltage Drop VDB 0.70 Volts KP 1.00 Bias Winding Diode Forward Voltage Drop Ripple to Peak Current Ratio (0.4 < KRP < 1.0 : 1.0< KDP<6.0) ENTER TRANSFORMER CORE/CONSTRUCTION VARIABLES Core Type EER28 Core Bobbin AE Page 17 of 36 EER28 P/N: PC40EER28-Z EER28_BO BBIN P/N: BEER-28-1112CPH cm^2 Core Effective Cross Sectional Area 0.821 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-136 75 W Single Output, LED Driver – TOP250YN 1-Apr-2008 LE 6.4 cm AL 2870 nH/T^2 BW 16.7 mm Bobbin Physical Winding Width mm Safety Margin Width (Half the Primary to Secondary Creepage Distance) Number of Primary Layers M 1.50 L 2.00 NS 6 Core Effective Path Length Ungapped Core Effective Inductance Number of Secondary Turns DC INPUT VOLTAGE PARAMETERS VMIN 294 Volts Minimum DC Input Voltage VMAX 392 Volts Maximum DC Input Voltage CURRENT WAVEFORM SHAPE PARAMETERS DMAX 0.29 IAVG 0.52 Amps Average Primary Current IP 3.58 Amps Peak Primary Current Maximum Duty Cycle IR 3.58 Amps Primary Ripple Current IRMS 1.11 Amps Primary RMS Current TRANSFORMER PRIMARY DESIGN PARAMETERS LP 171 NP NB uHenries 26 Primary Inductance Primary Winding Number of Turns 3 Bias Winding Number of Turns ALG 248 nH/T^2 Gapped Core Effective Inductance BM 2838 Gauss Maximum Flux Density at PO, VMIN (BM<3000) BP 3848 Gauss Peak Flux Density (BP<4200) BAC 1419 Gauss ur 1780 AC Flux Density for Core Loss Curves (0.5 X Peak to Peak) Relative Permeability of Ungapped Core LG 0.38 mm Gap Length (Lg > 0.1 mm) BWE 27.4 mm Effective Bobbin Width OD 1.04 mm Maximum Primary Wire Diameter including insulation INS 0.08 mm DIA 0.96 mm Estimated Total Insulation Thickness (= 2 * film thickness) Bare conductor diameter 19 AWG AWG CM 1290 CMA 1160 Cmils Primary Wire Gauge (Rounded to next smaller standard AWG value) Bare conductor effective area in circular mils Cmils/Amp !!! DECREASE CMA (200 < CMA < 500) Decrease L(primary layers),increase NS,smaller Core TRANSFORMER SECONDARY DESIGN PARAMETERS (SINGLE OUTPUT EQUIVALENT) Lumped parameters ISP 15.66 Amps ISRMS 7.62 Amps Secondary RMS Current IO 4.58 Amps Power Supply Output Current IRIPPLE 6.09 Amps Output Capacitor RMS Ripple Current CMS 1524 Cmils Secondary Bare Conductor minimum circular mils Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Peak Secondary Current Page 18 of 36 1-Apr-2008 DER-136 75 W Single Output, LED Driver – TOP250YN AWGS 18 AWG Secondary Wire Gauge (Rounded up to next larger standard AWG value) Secondary Minimum Bare Conductor Diameter DIAS 1.03 mm ODS 2.28 mm INSS 0.63 mm VOLTAGE STRESS PARAMETERS VDRAIN 655 Volts PIVS 115 Volts Maximum Drain Voltage Estimate (Includes Effect of Leakage Inductance) Output Rectifier Maximum Peak Inverse Voltage PIVB 55 Volts Bias Rectifier Maximum Peak Inverse Voltage Secondary Maximum Outside Diameter for Triple Insulated Wire Maximum Secondary Insulation Wall Thickness 9 Specifications For Common Mode Inductor L1 3 4 1 Electrical Diagram 2 9.1 Figure 8 – L1 Electrical Diagram. 9.2 Inductance Inductance 9.3 42 uH Material Item 1 2 3 Description Fair-Rite Toroid 5943000201 Magnetic wire 26AWG Triple Insulated wire 26AWG 9.4 Winding Instructions Wind 12 parallel turns using item [2] and item [3]. Wind tightly and uniformly as shown in figure 9. Page 19 of 36 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-136 75 W Single Output, LED Driver – TOP250YN 1-Apr-2008 Figure 9 – Picture of L1. Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Page 20 of 36 1-Apr-2008 DER-136 75 W Single Output, LED Driver – TOP250YN 10 Performance Data All measurements performed at room temperature, 60 Hz input frequency. 10.1 Efficiency 90 Output Efficiency (%) 80 70 60 50 40 30 20 200 210 220 230 240 250 260 270 Line Voltage (AC) Figure 10 – Efficiency vs Input Voltage. Full Load, Room Temperature, 60 Hz. INPUT VOLTAGE (AC) 208 215 230 240 265 277 OUTPUT EFFICIENCY (%) 86.01 85.64 85.39 85.51 85.62 85.32 Table 1: Measurements of Efficiency vs Line Voltage at Full Load. Page 21 of 36 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com 280 DER-136 75 W Single Output, LED Driver – TOP250YN 1-Apr-2008 10.2 Output Characteristic 30 Output Voltage (DC) 25 20 277 VAC 15 208 VAC Lower Current Limit 10 Upper Current Limit 5 0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Output Current (DC) Figure 11 – Output Characteristic Showing Line and Load Regulation, Room Temperature. Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Page 22 of 36 1-Apr-2008 DER-136 75 W Single Output, LED Driver – TOP250YN 10.3 Harmonic Content 400 350 Input Current (mA) 300 250 200 150 100 50 0 1 2 3 4 5 6 7 8 9 10 Harmonic Figure 12 – Input Current Harmonic Content. Full Load, VIN = 230 VAC. 10.4 Harmonic Content in Percentage of Fundamental Harmonic Iin(mA) At 230VAC 1 2 3 4 5 6 7 8 9 10 385 2.4 15.6 2.3 10.5 1 8.6 0.5 6.5 0.4 % of Maximum % Allowed By IEC Fundamental 61000-3-2. Class C 0.62 4.05 0.60 2.73 0.26 2.23 0.13 1.69 0.10 2.0 29.7 10.0 7.0 5.0 Table 2: Harmonic Content in Percentage of Fundamental and IEC 61000-3-2 Limits for C Class Equipment. NOTE: Third Harmonic Spec Follows the Formula: 30* PFC. (Power Factor at 230 VAC). Page 23 of 36 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-136 75 W Single Output, LED Driver – TOP250YN 1-Apr-2008 10.5 Power Factor Vs Line Voltage at Full Load 1.00 Power Factor 0.99 0.98 0.97 0.96 0.95 200 220 240 260 280 Input Voltage (AC) Figure 13 – Power Factor (PF) vs Input Line Voltage (VAC). INPUT VOLTAGE (AC) 208 215 230 240 265 277 POWER FACTOR 0.992 0.992 0.990 0.988 0.982 0.978 Table 3: Power Factor Measurements at Full Load. Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Page 24 of 36 1-Apr-2008 DER-136 75 W Single Output, LED Driver – TOP250YN 11 Thermal Performance Two sets of data were taken on the UUT. One set was taken with the unit inside a closed cardboard box at room temperature. The second set of data was taken with the UUT in a metal box encapsulated with thermal-conductive Epoxy. Results are shown below. Temperature (°°C) UUT Open Frame Item Ambient TOPSwitch (U1) Transformer (T1) Output Rectifiers (D10, D11) 208 VAC 277 VAC 25 25 77 78 77 79 70 69 UUT Encapsulated with thermal epoxy in a metal case. 208 VAC 277 VAC 25 25 63 59 66 63 62 57 Table 4: Temperatures of Critical Components in the Power Supply. 208 VAC, 75 W load, 25 ºC Ambient Figure 14 – Infrared Thermograph of Open Frame Operation at Room Temperature. Page 25 of 36 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-136 75 W Single Output, LED Driver – TOP250YN 1-Apr-2008 12 Waveforms All waveforms are shown with LEDs used as load. 12.1 Drain Voltage and Current, Normal Operation Figure 15 – 208 VAC, Full Load. Upper: ID 2.0 A / Div. Lower: VDRAIN 200 V / Div. Figure 16 – 277 VAC, Full Load. Upper: ID 2.0 A / Div. Lower: VDRAIN 200 V / Div. Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Page 26 of 36 1-Apr-2008 DER-136 75 W Single Output, LED Driver – TOP250YN 12.2 Output Voltage Start-up Profile Figure 17 – Start-up Profile, 208 VAC. 5 V, 50 ms / div. Figure 18 – Start-up Profile, 277 VAC. 5 V, 50 ms / div. 12.3 Drain Voltage and Current Start-up Profile Figure 19 – 208 VAC Input and Maximum Load. Upper: IDRAIN, 2.0 A / div. Lower: VDRAIN, 200 V / div. Page 27 of 36 Figure 20 – 277 VAC Input and Maximum Load. Upper: IDRAIN, 2.0 A / div. Lower: VDRAIN, 200 V / div. Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-136 75 W Single Output, LED Driver – TOP250YN 1-Apr-2008 12.4 Output Ripple Measurements 12.4.1 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 the figures below. Tie two capacitors in parallel across the probe tip of a 4987BA probe adapter. The capacitors include one (1) 0.1 µF/50 V ceramic type and one (1) 1.0 µF/50 V aluminum electrolytic. The aluminum-electrolytic capacitor is polarized, so always maintain proper polarity across DC outputs (see Figure 21 and Figure 22). Probe Ground Probe Tip Figure 21 – Oscilloscope Probe Prepared for Ripple Measurement. (End Cap and Ground Lead Removed). Figure 22 – Oscilloscope Probe with Probe Master (www.probemaster.com) 4987A BNC Adapter. (Modified with wires for ripple measurement, and two parallel decoupling capacitors added). Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Page 28 of 36 1-Apr-2008 DER-136 75 W Single Output, LED Driver – TOP250YN 12.4.2 Measurement Results Figure 23 – Output Ripple 208 VAC, Full Load. Upper: VOUT, 5 V / div. Lower: IOUT, 1 A/ div V, 5 ms / div. Figure 24 – Output Ripple 230 VAC, Full Load. Upper: VOUT, 5 V / div. Lower: IOUT, 1 A/ div V, 5 ms / div. Figure 25 – Output Ripple 277 VAC, Full Load. Upper: VOUT, 5 V / div. Lower: IOUT, 1 A/ div V, 5 ms / div. Page 29 of 36 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-136 75 W Single Output, LED Driver – TOP250YN 1-Apr-2008 13 Control Loop Analysis Following are the loop plots measured at 208 VAC and 277 VAC. Since it is a single stage PFC power supply, the loop bandwidth is necessarily low and in this case crossover occurs at approximately 35 – 40 Hz. Figure 26 – Bode Plot Measured at 208 VAC and Full Load. Crossover Occurs at Approximately 38 Hz With a Phase Margin of Approximately 50 Degrees. Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Page 30 of 36 1-Apr-2008 DER-136 75 W Single Output, LED Driver – TOP250YN Figure 27 – Bode Plot Measured at 277 VAC and Full Load. Crossover Occurs at Approximately 40 Hz With a Phase Margin of Approximately 45 Degrees. Page 31 of 36 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-136 75 W Single Output, LED Driver – TOP250YN 1-Apr-2008 14 Surge Test 14.1 Surge Test Results with 1.2/50 µs Waveform Surge Level (V) +500 -500 +1000 -1000 Input Voltage (VAC) 230 230 230 230 Injection Location Injection Phase (°) Number Of Surges Test Result (Pass/Fail) L to N L to N L and N to G L and N to G 90 90 90 90 10 10 10 10 Pass Pass Pass Pass 14.2 Surge Test Results with 0.5 µs-100 kHz Ring-Waveform Surge Level (V) +2500 -2500 +2500 -2500 Input Voltage (VAC) 230 230 230 230 Injection Location Injection Phase (°) Number Of Surges Test Result (Pass/Fail) L to N L to N L and N to G L and N to G 90 90 90 90 10 10 10 10 Pass Pass Pass Pass Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Page 32 of 36 1-Apr-2008 DER-136 75 W Single Output, LED Driver – TOP250YN 15 Conducted EMI Figure 28 – Conducted EMI, 230 VAC Full Load, UUT Placed on a Grounded Metal Plate. Page 33 of 36 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-136 75 W Single Output, LED Driver – TOP250YN 1-Apr-2008 16 Revision History Date 01-Apr-08 Author KM Revision 1.6 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Description & changes Added redrawn schematic Reviewed Page 34 of 36 1-Apr-2008 DER-136 75 W Single Output, LED Driver – TOP250YN Notes Page 35 of 36 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-136 75 W Single Output, LED Driver – TOP250YN 1-Apr-2008 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. 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