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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 Power Integrations 5245 Hellyer Avenue, San Jose, CA 95138 USA. Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com 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.
DER-39 2.5W Adapter LNK520P May 13, 2004 Table Of Contents 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 Introduct ion
This document is an engineering report giving performance char acteristics of a prototype 2.5W charger/adapter opt imized to replace a linear tr ansformer. 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 spec ification, schematic, bill of materi als, 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 Comment Input Voltage VIN 90 265 Vac 2 Wire- No protective ground Frequency fLINE 47 50/60 64 Hz No-load Input Power (230Vac) 0.3 W 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 η 67 % At full load @ 230V Operating Temperature TAMB -5 50 C Conducted EMI CISP22B/EN55022B with Artificial hand connected to output return Table 1 – Typical Power Supply Specification V-I CHARACTERISTIC 0 100 200 300 400 500 600 700 800 900 1000 Iload Vout HLIMIT LLIMIT 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 F igure 3 provi des a CV/CC (constant voltage and consta nt current) output characteristic form the uni versal input voltage range of 90 VAC to 26 5 VAC. The nominal peak power point at the trans ition 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 f ault conditions and is requirement to meet safety agency fault testing. This component should be a wire wound type t o withstand input current surges while the input capac itors charge on applic ation of power or during withstand line-transient testing. Metal film type resistors are not recommended, they do not have the transient dissipatio n capabilities required and ma y 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 associat ed with the supply to meet EN 55022B/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 a ppears at the DRAIN pin of the LINKSWITCH (U1). The CONTROL pin capacit or C3 is t hen charged through a switched high voltage current source connected interna lly between the DRAIN and CONTROL pins. When the CO NTROL 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 fl yback transformer T1, energy is s tored. 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 t he primary-side by monitoring the primary-side VOR (voltage output reflected). While t he output diode is conducting, the voltage across the transform er 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 det ermined by the c urrent flowing into the CONTROL pin. During start-up, as the output v oltage, and therefore the reflected volt age 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, t he output voltage is regulated through control of the duty cycle. As th e current into the CONTROL pin exceeds approximately 2 mA, t he duty cy cle 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 1/2LI 2f) and the output voltage and the VOR falls, the reduc ed CO NTROL pin curr ent will lower the internal current providing an appr oximately constant current c haracteristic. If the output load is further increased and the output voltage fall further to belo w a CONTROL pin current of 1mA, t he CONTROL pin capac itor C3 will discharge and the su pply will e nter auto-restart. The transformer is designed t o always be di scontinuous; 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 dio de 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 t emperature and a pplied voltage. Low-cost, Metallize d plastic film capacito rs are ideal; high valu e, low-cost ceramic capacitors are not recommended. Dielectrics used for these capacitors such as Z5U an d 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 t he 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 increas ed to 1uF to ensure enough time dur ing start-up to bring the output into regulation. The type of capacitor is not critical; either a sma ll 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 th e application, the designer may choo se not to derate for ripple curr ent. If the applic ation is battery charging of equipment such as PDA’s or cell phones, the duty cycle of operation at high ripple current is lik ely to be low, perhaps only 1 hour per day. In this case th e capacitor temperature can be allowed to rise significantly during charging without concern for the overall lifetime. Resistor R8 acted as preload to prevent t he output from exceedi ng the maximum output voltage limit as specified in F igure 3 at no-load and high line. Ot herwise 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 Quantity Reference Part Description 1 2 C1, C2 4.7uF, 400V 2 1 C3 0.22uF, 25V, X7R ceramic 3 1 C4 0.1uF, 100V, X7R ceramic 4 1 C5 330uF, 10V Low ESR E-cap Panasonic FC series 5 4 D1, D2, D3, D4 1N4005, 1A, 600V 6 1 D5 1N4937, 1A, 600V 200nS, Fast Rectifier 7 1 D6 UG1B, 1A, 100V, 15nS Ultra Fast Rectifier 8 1 L1 1mH Inductor- Tokin part #SBCP-47HY102B 9 1 RF1 10 ohm, 1W, Fusible- Vitrohm 253-4 Series 10 1 R2 130 ohms, 1% 0603 SMD resistor 11 1 R1 23.7 Kohm 1%; 1/4W resistor 12 1 R5 56 Kohm; 0603 SMD resistor 3 1 T1 Custom EF12.6 – Core & Bobbin 14 1 U1 LINK520P- High Voltage IC; Power Integrations, Inc 15 1 PCB FR1 – 1oz copper DIM: 1.7” x 1.1”; 1.0mm thick Page 10 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
7 T ransformer Specification
7.1 Transformer Winding
#36AWG WDG1 18T 32AWG T.I.W WDG2 13T #34AWG X3 Figure 5 – Transformer Schematic EF12.6
7.2 Electrical Specifications
Electrical Strength 60Hz 1minute, from Pins 1-4 to Pins 5-6 3 kV for 1 minute Primary Inductance (Pin 1 -Pin 3 @ 42KHZ All windings open 2450 uH – 2700uH Primary Leakage Inductance @42KHZ LK with pins 5-6 shorted < 60 uH Page 11 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
7.3 Transformer Construction
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 Change the start pin connection of secondary winding from pin 4 to pin 5. Basic Insulation Continue winding the tape previously placed for one layer with overlap to secure the end wire of WDG1. WDG2: Cancellation Winding 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. Basic Insulation 1 layer of tape (Item 6) for insulation. Page 12 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 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 Band Place outside 1 turn of item 8 with tight contact to winding surface. Connect item 8 to pin 3 by item 3. Crop unused pins Remove pin 7 and 8 Varnish NO
7.5 M aterials
[1] Core: EF12.6 [2] Bobbin: BEF12.6- Horizontal 8-PINS [3] Magnet Wire: #34 AWG [4] Magnet Wire: #36 AWG [5] Triple Insulated wire: # 32 AWG [6] Tape: 3M 1298 Polyester Film (white) 0.311 x 2 mils [7] Tape: 3M 1298 Polyester Film (white) 0.275 x 2 mils [8] Copper Foil: 0.01mils x 6mm
7.6 Design Notes
Power Integrations Device LNK501P Frequency of Operation 42KHZ Mode Discontinuous Peak current 0.263 A Reflected Voltage (Secondary to Primary) 47 V AC Input Voltage Range 90-265VAC Page 13 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
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 40.0 45.0 50.0 55.0 60.0 65.0 70.0 85 100 115 130 145 160 175 190 205 220 235 250 265 Input (Vac) Percent Efficiency (%) Efficiency 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 2.5W Adapter LNK520P May 13, 2004
8.2 No-load Input Power
85 100 115 130 145 160 175 190 205 220 235 250 265 Line Input (Vac) Input Power (mW) No-load 278mW at 230Vac Figure 8 – Zero load input power vs. Input line voltage. The No-Load consumption at 230Vac is 278mW.
8.3 Line and Load Regulation
0 100 200 300 400 500 600 700 800 900 1000 Load Current (mA) Output Voltage (Vdc) 230Vac 115Vac H-Limit L-Limit 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 V-I Characterisitc 0 100 200 300 400 500 600 700 800 900 1000 Load Current (mA) Output Voltage (Vdc) 90Vac 265Vac H-Limit L-Limit 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 Figure 12 - 265 VAC, Full Load Upper: VDRAIN, 200 V, 5 µs / div Lower: IDRAIN, 0.2 A / div Page 18 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 Output Ripple Measurements
10.2.1 Ripple Measurement Technique
For DC out put ripple measurements, a modifi ed oscilloscope test probe must be utiliz ed in order to reduce spurious signals due to pi ckup. Det ails of t he probe modification are provided in Figure 13 and Figure 14. The 5125BA probe adapter is affixed with two capac itors 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 alu minum 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 Date Author Revision Description & changes Reviewed May 13, 2004 ME 1.0 First Release VC / AM For the latest updates, visit our Web site: www.powerint.com PATENT INFORMATION Power Inte grations res erves the rig ht to make ch anges to its pro ducts at an y time to impr ove re liability or manufacturability. Po wer Integrati ons do es not assume an y liability ar ising from the use of an y device or circuit described herein, nor does it convey any license under its patent rights or the rights of others. The products and applications il lustrated herein (i ncluding circu its ext ernal to th e pro ducts a nd transform er construction) ma y b e cover ed b y on e or more U.S. and foreign p atents or potentia lly b y pe nding U .S. and foreig n patent applications assigned to Power Integrations. A co mplete list of Po wer 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.
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