Design Example Report Title 2.5W Adapter using LNK520P Specification Input: 90-265Vac Output: 5.5V / 450mA Application Cell Phone Charger Author Power Integrations Applications Department Document Number DER-39 Date May 13, 2004 Revision 1.0 Summary and Features • • • • • • • • No optocoupler Provides sloping output VI characteristic, making it an ideal low standby power replacement for a linear transformer Uses an EF12.6 transformer No Y1 safety capacitor required, giving very low earth leakage current Meets CISPR-22B with large margin Low component count Less than 300mW standby consumption at 230 VAC High efficiency 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-39 2.5W Adapter LNK520P May 13, 2004 Table Of Contents 1 2 3 4 Introduction.................................................................................................................3 Power Supply Specification ........................................................................................4 Schematic...................................................................................................................5 Circuit Description ......................................................................................................6 4.1 Input EMI Filtering ...............................................................................................6 4.2 LinkSwitch Operation ..........................................................................................6 4.3 Clamp and Feedback Components .....................................................................7 4.4 Output Stage .......................................................................................................8 5 PCB Layout ................................................................................................................9 6 Bill Of Materials ........................................................................................................10 7 Transformer Specification.........................................................................................11 7.1 Transformer Winding .........................................................................................11 7.2 Electrical Specifications.....................................................................................11 7.3 Transformer Construction..................................................................................12 7.4 Winding Instructions ..........................................................................................12 7.5 Materials............................................................................................................13 7.6 Design Notes.....................................................................................................13 8 Performance Data ....................................................................................................14 8.1 Efficiency ...........................................................................................................14 8.2 No-load Input Power..........................................................................................15 8.3 Line and Load Regulation..................................................................................15 9 Thermal Performance...............................................................................................17 10 Waveforms............................................................................................................18 10.1 Drain Voltage and Current, Normal Operation...................................................18 10.2 Output Ripple Measurements............................................................................19 10.2.1 Ripple Measurement Technique ................................................................19 10.2.2 Measurement Results ................................................................................20 11 Conducted EMI .....................................................................................................21 12 Revision History ....................................................................................................23 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. Design Reports contain a power supply design specification, schematic, bill of materials, and transformer documentation. Performance data and typical operation characteristics are included. Typically only a single prototype has been built. Page 2 of 23 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-39 2.5W Adapter LNK520P May 13, 2004 1 Introduction This document is an engineering report giving performance characteristics of a prototype 2.5W charger/adapter optimized to replace a linear transformer. The supply uses LinkSwitch (LNK520P) – an integrated IC combining a 700V high voltage MOSFET, PWM controller, start-up, thermal shutdown, and fault protection circuitry. Using LNK520P in the high side switching gives a sloping VI-characteristic with no optocoupler. The design used no Y-cap, but has very low EMI emissions. This document contains the power supply specification, schematic, bill of materials, transformer documentation, and performance data. Figure 1 – Populated Circuit Board Photograph Page 3 of 23 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-39 2.5W Adapter LNK520P May 13, 2004 2 Power Supply Specification Description Symbol Min Typ Max Units VIN fLINE 90 47 50/60 265 64 0.3 Vac Hz W Comment Input Voltage Frequency No-load Input Power (230Vac) Output Output Voltage 1 VOUT 5.5 V see Figure 1 Output Current 1 IOUT 0.45 A see Figure 1 Continuous Output Power POUT 2.5 W Efficiency Operating Temperature Conducted EMI η TAMB 67 -5 50 2 Wire- No protective ground % C At full load @ 230V CISP22B/EN55022B with Artificial hand connected to output return Table 1 – Typical Power Supply Specification V-I CHARACTERISTIC 10 9 HLIMIT 8 LLIMIT 7 Vout 6 5 4 3 2 1 0 0 100 200 300 400 500 600 700 800 900 1000 Iload Figure 2 - Output V-I Characteristic Envelope Specification Page 4 of 23 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-39 2.5W Adapter LNK520P May 13, 2004 3 Schematic Figure 3 – Schematic ** optional parts are not installed on the board Page 5 of 23 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-39 2.5W Adapter LNK520P May 13, 2004 4 Circuit Description The schematic shown in the Figure 3 provides a CV/CC (constant voltage and constant current) output characteristic form the universal input voltage range of 90 VAC to 265 VAC. The nominal peak power point at the transition from CC to CV is 5.5 V at 450 mA. The output envelope specification is shown is Figure 2. 4.1 Input EMI Filtering The incoming AC is rectified and filtered by D1-4, C1 and C2. Resistor RF1 is a flameproof fusible type to protect against fault conditions and is requirement to meet safety agency fault testing. This component should be a wire wound type to withstand input current surges while the input capacitors charge on application of power or during withstand line-transient testing. Metal film type resistors are not recommended, they do not have the transient dissipation capabilities required and may fail prematurely in the field. The input capacitance is split between C1 and C2 to allow an input pi filter to be formed by L1. This filters noise associated with the supply to meet EN55022B/CSPR 22 B and FCC B conducted EMC limits, even when no Y safety capacitor is used. 4.2 LinkSwitch Operation When the power is applied to the supply, high voltage DC appears at the DRAIN pin of the LINKSWITCH (U1). The CONTROL pin capacitor C3 is then charged through a switched high voltage current source connected internally between the DRAIN and CONTROL pins. When the CONTROL pin voltage reaches approximately 5.7 V relative to the SOURCE pin, the internal current source is turned off. The internal control circuitry is activated and the high voltage internal MOSFET starts to switch, using the energy in C3 to power the IC, As the current ramps in the primary of the flyback transformer T1, energy is stored. This energy is delivered to the output when the mosfet turns off each cycle. The secondary of the transformer is rectified and filtered by D6 and C5 to provide the DC output to the load. Control of the output characteristic is entirely sensed from the primary-side by monitoring the primary-side VOR (voltage output reflected). While the output diode is conducting, the voltage across the transformer primary is equal to the output voltage plus diode drop multiplied by the turns ratio of the transformer. Since the LinkSwitch is connected on the high side of the transformer, VOR can be sensed directly. Page 6 of 23 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-39 2.5W Adapter LNK520P May 13, 2004 Diode D5 and capacitor C4 form the primary clamp network. The voltage held across C4 is essentially the VOR with an error due to the parasitic leakage inductance. The LinkSwitch has three operating modes determined by the current flowing into the CONTROL pin. During start-up, as the output voltage, and therefore the reflected voltage and voltage across C4 increases, the feedback current increases from 0 to approximately 2mA through R1 in the CONTROL pin. The internal current limit is increased during this period until reaching 100%, providing an approximately constant output current. Once the output voltage reaches the regulated CV value, the output voltage is regulated through control of the duty cycle. As the current into the CONTROL pin exceeds approximately 2 mA, the duty cycle begins to reduce, reaching 30% at a CONTROL pin current of 2.3mA. If the duty cycle reaches a 3% threshold, the switching frequency is reduced, which reduces energy consumption under light or no load conditions. As the output load increases beyond the peak power point (defined by 1/2LI2f) and the output voltage and the VOR falls, the reduced CONTROL pin current will lower the internal current providing an approximately constant current characteristic. If the output load is further increased and the output voltage fall further to below a CONTROL pin current of 1mA, the CONTROL pin capacitor C3 will discharge and the supply will enter auto-restart. The transformer is designed to always be discontinuous; that is all the energy is transferred to the load during the mosfet off time. 4.3 Clamp and Feedback Components Diode D5 should either be a fast or ultra-fast type to prevent the voltage across the LinkSwitch from reversing and ringing below ground. A fast diode is preferred, being lower cost. Leakage inductance in filtered by R2. Capacitor C4 is typically fixed at 0.1uF and should be rated above the VOR and be stable with both temperature and applied voltage. Low-cost, Metallized plastic film capacitors are ideal; high value, low-cost ceramic capacitors are not recommended. Dielectrics used for these capacitors such as Z5U and Y5U are not stable and can cause output instability as their value changes with voltage and temperature. Page 7 of 23 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-39 2.5W Adapter LNK520P May 13, 2004 R1 was selected to program the peak power point to be 450mA when a transformer with a nominal inductance value was used. C3 sets the auto-restart period and also the time the output has to reach regulation before entering auto-restart from start-up. If a battery load is used then a value of 0.22uF is typical. However, if the supply is required to start into a resistive load then this should be increased to 1uF to ensure enough time during start-up to bring the output into regulation. The type of capacitor is not critical; either a small ceramic or electrolytic may be used with a voltage rating of 10V or more. 4.4 Output Stage Diode D6 should be rated for 80% of applied reverse voltage and thermally for average current multiplied by forward voltage at maximum ambient. A snubber series RC across D6 may be fitted to improved radiated EMI performance. Capacitor C5 should be rated for output voltage and ripple current. Depending on the application, the designer may choose not to derate for ripple current. If the application is battery charging of equipment such as PDA’s or cell phones, the duty cycle of operation at high ripple current is likely to be low, perhaps only 1 hour per day. In this case the capacitor temperature can be allowed to rise significantly during charging without concern for the overall lifetime. Resistor R8 acted as preload to prevent the output from exceeding the maximum output voltage limit as specified in Figure 3 at no-load and high line. Otherwise a preload is not necessary. Page 8 of 23 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-39 2.5W Adapter LNK520P May 13, 2004 5 PCB Layout Figure 4 - PCB Layout and Dimensions (0.001 inch) Page 9 of 23 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-39 2.5W Adapter LNK520P May 13, 2004 6 Bill Of Materials Item 1 2 3 4 Quantity 2 1 1 1 Reference C1, C2 C3 C4 C5 5 6 7 8 9 10 11 12 3 14 4 1 1 1 1 1 1 1 1 1 D1, D2, D3, D4 D5 D6 L1 RF1 R2 R1 R5 T1 U1 15 1 PCB Page 10 of 23 Part Description 4.7uF, 400V 0.22uF, 25V, X7R ceramic 0.1uF, 100V, X7R ceramic 330uF, 10V Low ESR E-cap Panasonic FC series 1N4005, 1A, 600V 1N4937, 1A, 600V 200nS, Fast Rectifier UG1B, 1A, 100V, 15nS Ultra Fast Rectifier 1mH Inductor- Tokin part #SBCP-47HY102B 10 ohm, 1W, Fusible- Vitrohm 253-4 Series 130 ohms, 1% 0603 SMD resistor 23.7 Kohm 1%; 1/4W resistor 56 Kohm; 0603 SMD resistor Custom EF12.6 – Core & Bobbin LINK520P- High Voltage IC; Power Integrations, Inc FR1 – 1oz copper DIM: 1.7” x 1.1”; 1.0mm thick Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-39 2.5W Adapter LNK520P May 13, 2004 7 Transformer Specification 7.1 Transformer Winding 1 5 WDG1 18T 32AWG T.I.W 6 WDG3 132T #36AWG 4 4 WDG2 13T #34AWG X3 3 Figure 5 – Transformer Schematic EF12.6 7.2 Electrical Specifications Electrical Strength Primary Inductance (Pin 1 -Pin 3 @ 42KHZ Primary Leakage Inductance @42KHZ Page 11 of 23 60Hz 1minute, from Pins 1-4 to Pins 5-6 3 kV for 1 minute All windings open 2450 uH – 2700uH LK with pins 5-6 shorted < 60 uH Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-39 7.3 2.5W Adapter LNK520P May 13, 2004 Transformer Construction 1 WDG3 4 4 3 5 6 WDG2 WDG1 Figure 6 – Transformer Cross-section EF12.6 7.4 Winding Instructions Place the bobbin on the winding machine with pins 1-4 on the right side. Winding should be in forward direction. WDG1: Secondary Winding Start at pin 4 temporarily. Wind 18 turns of item 5(#32AWG T.I.W.) from right to left with tight tension. Wind uniformly in a single layer across entire width of bobbin. Finish on pin 6. Basic Insulation Secure winding partially using item 6. WDG1: Secondary Winding Basic Insulation Change the start pin connection of secondary winding from pin 4 to pin 5. WDG2: Cancellation Winding Basic Insulation Page 12 of 23 Continue winding the tape previously placed for one layer with overlap to secure the end wire of WDG1. Start at pin 3. Wind 13 turns with trifilar of item 3 (#34AWG wire) from right to left with tight tension. Wind uniformly in a single layer across entire width of bobbin. Finish on pin 4. 1 layer of tape (Item 6) for insulation. Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-39 2.5W Adapter LNK520P May 13, 2004 WDG3: Primary winding 3 layers. Start at pin 4. Wind 132 turns of item 4 (#36AWG) from right to left in three layers across entire width of bobbin. Wind uniformly all layers with tight tension. Finish on pin 1. Outer Insulation 7 Layer of tape using item 7. Core Assembly Assemble and secure core halves with glue. Shield / Belly Place outside 1 turn of item 8 with tight contact to winding Band surface. Connect item 8 to pin 3 by item 3. Crop unused pins Remove pin 7 and 8 Varnish NO 7.5 Materials Item [1] [2] [3] [4] [5] [6] [7] [8] 7.6 Description Core: EF12.6 Bobbin: BEF12.6- Horizontal 8-PINS Magnet Wire: #34 AWG Magnet Wire: #36 AWG Triple Insulated wire: # 32 AWG Tape: 3M 1298 Polyester Film (white) 0.311 x 2 mils Tape: 3M 1298 Polyester Film (white) 0.275 x 2 mils Copper Foil: 0.01mils x 6mm Design Notes Power Integrations Device Frequency of Operation Mode Peak current Reflected Voltage (Secondary to Primary) AC Input Voltage Range Page 13 of 23 LNK501P 42KHZ Discontinuous 0.263 A 47 V 90-265VAC Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-39 2.5W Adapter LNK520P May 13, 2004 8 Performance Data All measurements performed at room temperature, 60 Hz input frequency. 8.1 Efficiency The efficiency was measured at maximum output power at room temperature. Efficiency Percent Efficiency (%) 70.0 65.0 60.0 Efficiency 55.0 50.0 45.0 40.0 85 100 115 130 145 160 175 190 205 220 235 250 265 Input (Vac) Figure 7 – Efficiency vs. Input voltage. At nominal inputs the efficiency is 67% Page 14 of 23 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-39 8.2 2.5W Adapter LNK520P May 13, 2004 No-load Input Power Input Power (mW) No-load 500 450 400 350 300 250 200 150 100 50 0 278mW at 230Vac No-load 85 100 115 130 145 160 175 190 205 220 235 250 265 Line Input (Vac) Figure 8 – Zero load input power vs. Input line voltage. The No-Load consumption at 230Vac is 278mW. 8.3 Line and Load Regulation Output Voltage (Vdc) V-I Characterisitc 10 9 8 7 6 5 4 3 2 1 0 230Vac 115Vac H-Limit L-Limit 0 100 200 300 400 500 600 700 800 900 1000 Load Current (mA) Figure 9 – Output VI Characteristic at selected input voltages (115V & 230V) Page 15 of 23 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-39 2.5W Adapter LNK520P May 13, 2004 Output Voltage (Vdc) V-I Characterisitc 10 9 8 7 6 5 4 3 2 1 0 90Vac 265Vac H-Limit L-Limit 0 100 200 300 400 500 600 700 800 900 1000 Load Current (mA) Figure 10 – Output VI Characteristic at selected input voltages (90V & 265V) Page 16 of 23 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-39 2.5W Adapter LNK520P May 13, 2004 9 Thermal Performance Measurement was taken at maximum output power inside a plastic enclosure at 90Vac; TAMBIENT =25oC with no airflow. Reference Description Temperature U1 LNK520P 67ºC T1 EF12.6 Transformer 54ºC D6 UG1B 69ºC Page 17 of 23 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-39 2.5W Adapter LNK520P May 13, 2004 10 Waveforms 10.1 Drain Voltage and Current, Normal Operation Figure 11 - 90 VAC, Full Load. Upper: VDRAIN, 200 V, 5 µs / div Lower: IDRAIN, 0.2 A / div Page 18 of 23 Figure 12 - 265 VAC, Full Load Upper: VDRAIN, 200 V, 5 µs / div Lower: IDRAIN, 0.2 A / div Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-39 2.5W Adapter LNK520P May 13, 2004 10.2 Output Ripple Measurements 10.2.1 Ripple Measurement Technique For DC output ripple measurements, a modified oscilloscope test probe must be utilized in order to reduce spurious signals due to pickup. Details of the probe modification are provided in Figure 13 and Figure 14. The 5125BA probe adapter is affixed with two capacitors tied in parallel across the probe tip. 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 type capacitor is polarized, so proper polarity across DC outputs must be maintained (see below). Probe Ground Probe Tip Figure 13 - Oscilloscope Probe Prepared for Ripple Measurement. (End Cap and Ground Lead Removed) Figure 14 - Oscilloscope Probe with Probe Master 5125BA BNC Adapter. (Modified with wires for probe ground for ripple measurement, and two parallel decoupling capacitors added) Page 19 of 23 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-39 2.5W Adapter LNK520P May 13, 2004 10.2.2 Measurement Results Figure 15 – V Ripple, 90 VAC, Full Load. 5 ms, 100 mV / div Figure 16 - V Ripple, 115 VAC, Full Load. 2 ms, 50 mV / div Figure 17 - Ripple, 230 VAC, Full Load. 5 ms, 100 mV /div Figure 18 - Ripple, 265 VAC, Full Load. 5 ms, 100 mV /div Page 20 of 23 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-39 2.5W Adapter LNK520P May 13, 2004 11 Conducted EMI Figure 19 - Conducted EMI, Maximum Steady State Load, LINE 115 VAC, 60 Hz, and EN55022 B Limits. With Artificial hand connected to Sec GND. Figure 20 - Conducted EMI, Maximum Steady State Load, LINE 115 VAC, 60 Hz, and EN55022 B Limits. Without Artificial hand connected to Sec GND. Page 21 of 23 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-39 2.5W Adapter LNK520P May 13, 2004 Figure 21 - Conducted EMI, Maximum Steady State Load, LINE 230 VAC, 60 Hz, and EN55022 B Limits. With Artificial hand connected to Sec GND. Figure 22 - Conducted EMI, Maximum Steady State Load, LINE 230 VAC, 60 Hz, and EN55022 B Limits. Without Artificial hand connected to Sec GND. Page 22 of 23 Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com DER-39 2.5W Adapter LNK520P May 13, 2004 12 Revision History Date May 13, 2004 Author ME Revision 1.0 Description & changes First Release Reviewed VC / AM For the latest updates, visit our Web site: www.powerint.com PATENT INFORMATION 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, nor does it convey any license under its patent rights or the rights of others. 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. The PI Logo, TOPSwitch, TinySwitch, LinkSwitch, and EcoSmart are registered trademarks of Power Integrations, Inc. PI Expert and DPA-Switch are trademarks of Power Integrations, Inc. © Copyright 2003, Power Integrations, Inc. WORLD HEADQUARTERS NORTH AMERICA - WEST Power Integrations, Inc. 5245 Hellyer Avenue San Jose, CA 95138 USA. 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