70W 适配器设计实例

Power Integrations Inc 5245 Hellyer Avenue, San Jose, CA 95138 USA. Tel: +1 408 414 9200 Fax: +1 408 414 9201 www: http://www.powerint.com Title Engineering Prototype Report - 70 W (19 V 3.66A) Universal Input Adapter (EP11) Target Applications Laptop Adapters, LCD Monitors, Audio, High Power Adapters Author Power Integrations Applications Dept. Doc Num EPR-00011 Date 22-January-2001 Revision 1.4 Features • Very compact design: (4.1” × 2.25” × 1.06”) • High power density - 7 W / inch³ • Full output power (70 W) in sealed enclosure at 40°C ambient • High efficiency: 84% (85 VAC), 89% (230 VAC) • Low no-load consumption: 350 mW (115 VAC), 500 mW (230 VAC) • Low value input capacitor: 74% DCMAX and line feed forward allows 2 µF/W • Power limited during overload: overload output current less than 5 A at 19 V • Primary side soft-start: minimizes component stresses during start-up • Low EMI due to frequency jittering: meets CISPR22B with output cap. earthed • Line under voltage sense: no output glitches on power up or power down • Line over voltage shutdown: extended line surge protection • Hysteretic thermal shutdown: supply automatically recovers when fault is removed • Low component count: simple circuit and design • Single sided PC board: no plated through holes • No surface mount components required EPR-00011 - 70 W Adapter 22-Jan-01 Page 2 of 46 Power Integrations Inc Tel: +1 408 414 9200 Fax: +1 408 414 9201 www: http://www.powerint.com Table of Contents 1 Introduction..................................................................................................................4 2 Power Supply Specification .........................................................................................6 3 Schematic ....................................................................................................................7 3.1 Description ...............................................................................................................7 4 PCB Layout................................................................................................................10 5 Bill of Materials ..........................................................................................................11 6 Transformer Documentation ......................................................................................12 6.1 Transformer Sources .............................................................................................14 7 Transformer Spreadsheet..........................................................................................15 8 Performance Data......................................................................................................17 8.1 Efficiency................................................................................................................17 8.2 No-load input power...............................................................................................18 8.3 Regulation / Power Limiting ...................................................................................18 9 Thermal Performance ................................................................................................20 10 Waveform Scope Plots ..............................................................................................24 10.1 Drain Voltage and Current During Normal Operation.........................................24 10.2 Output Voltage During Power-up........................................................................25 10.3 Output Voltage During Power-down ...................................................................26 10.4 Drain Voltage and Current during Power-Up (265 VAC)......................................26 10.5 DRAIN Current During Power-Up and Power-Down...........................................27 10.6 Load Transient response (15 to 100% load change) .........................................28 10.6.1 15 to 100% load change, 85 VAC.....................................................................28 10.7 Load Transient response (0 to 50% load change) .............................................29 10.7.1 0 to 50% load change, 85 VAC.........................................................................29 10.7.2 0 to 50% load change, 130 VAC.......................................................................29 10.7.3 0 to 50% load change, 130 VAC.......................................................................30 10.8 Ripple Measurements.........................................................................................30 10.8.1 DC Ripple Measurement Technique...............................................................30 10.8.2 Ripple Measurement Results..........................................................................31 11 Control Loop Characteristics .....................................................................................32 11.1 Gain Phase Results............................................................................................33 12 Conducted EMI Scans ...............................................................................................36 Important Note: Although the EP11 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 22-Jan-01 EPR-00011 - 70 W Adapter Page 3 of 46 Power Integrations Inc Tel: +1 408 414 9200 Fax: +1 408 414 9201 www: http://www.powerint.com 13 Appendix A - Thermal considerations: ...................................................................... 37 13.1 Efficiency: .......................................................................................................... 38 13.2 Heat Sinking: ..................................................................................................... 38 13.3 Heat Spreading and Enclosure Surface Temperature: ...................................... 39 13.4 Component Temperature: .................................................................................. 39 13.5 Conclusion: ........................................................................................................ 40 14 Appendix B - Custom Component Documentation:................................................... 41 14.1 Toroid Filter Inductor (L2): ................................................................................. 41 14.2 Output Inductor (L1)........................................................................................... 42 14.3 Heat sink #1 (TOPSwitch-GX and Input Bridge)................................................ 43 14.4 Heat sink #2 (Output Diodes) ............................................................................ 43 15 Revision History ........................................................................................................ 44 EPR-00011 - 70 W Adapter 22-Jan-01 Page 4 of 46 Power Integrations Inc Tel: +1 408 414 9200 Fax: +1 408 414 9201 www: http://www.powerint.com 1 Introduction This document is an engineering report that describes a universal input power supply that utilises a TOP249Y. This supply is an off-line flyback converter that operates in continuous mode. Below is a list of notable features: • Very compact design: (4.1”×2.25”×1.06” internal box dimensions) • High power density - 7 W / inch³ • Full output power in sealed enclosure at 40°C ambient • High efficiency: 84% (85 VAC), 89% (230 VAC) • Low no-load consumption: 350mW (115 VAC), 500 mW (230 VAC) • Low value input capacitor: extended maximum duty cycle allows 2µF/W • Power limited during overload: overload output current < 5 A at 19 V • Primary side soft-start: minimizes component stresses during start-up • Low EMI due to frequency jittering: meets CISPR22 B / EN55022 B with output earthed • Line under voltage sense: no output glitches on power up or power down • Line over voltage shutdown: extended line surge protection • Hysteretic thermal shutdown: supply automatically recovers when fault is removed • Low component count: simple circuit and design • Single sided PC board: no plated through holes • No surface mount components required This board demonstrates the basic performance features and the increased power capability of the new TOPSwitch-GX family. It was designed to allow testing within the enclosure of a commercial laptop power adapter. This enclosure was used for the thermal testing in section 9. This document contains the power supply specification, schematic, bill of materials and transformer documentation. Typical operating characteristics are presented at the rear of the report and consist of performance curves and scope waveforms 22-Jan-01 EPR-00011 - 70 W Adapter Page 5 of 46 Power Integrations Inc Tel: +1 408 414 9200 Fax: +1 408 414 9201 www: http://www.powerint.com Figure 1 - EP11 Inside Commercial Laptop Enclosure (4.25 x 2.5 x 1.2" / 108 x 64 x 30mm – external diemonsions) 4.1” / 104.1mm Figure 2 - EP11 Populated Circuit Board (dimensions include heat spreader not shown) 2.25” / 57mm Height=1.06” / 26.9 mm EPR-00011 - 70 W Adapter 22-Jan-01 Page 6 of 46 Power Integrations Inc Tel: +1 408 414 9200 Fax: +1 408 414 9201 www: http://www.powerint.com 2 Power Supply Specification Description Symbol Min Typ Max Units Comment Input Input Voltage VIN 85 115/230 265 VAC Input Frequency f 47 50/60 64 Hz No-load Input Power (115 VAC) 370 mW See fig 7 No-load Input Power (230 VAC) 520 mW See fig 7 Output Output Voltage VOUT 18.7 19.2 19.7 VDC† At output terminals Output Ripple Voltage VRIPPLE 120 mVp-p 20 MHz BW Output Current IOUT 0 3.66 ADC Continuous Output Power POUT 0 70 W Total Regulation ‡ -2 +2 % 0 – 100% load,85 – 265 VAC Efficiency (85 VAC) Efficiency (230 VAC) ηηηη 84 89 % At full load Environmental Conducted EMI Meets CISPR22 B Safety Designed to meet IEC950 External Ambient Temperature TAMB 0 25 40 oC In enclosure with naturalconvection (see section 9) † Output voltage tolerance may be improved through choice of feedback components. ‡ Nominal output voltage for purposes of determining regulation limits is measured at 115 VAC input and 3.66 A output current. Table 1 - Power supply specification EPR-00011 - 70 W Adapter 22-Jan-01 Page 7 of 46 Power Integrations Inc Tel: +1 408 523 9200 Fax: +1 408 523 9300 www: http://www.powerint.com 3 Schematic Figure 3 - 70W TOP249Y Power Supply Schematic 3.1 Description The EP11 is a low-cost flyback switching power supply using the TOP249Y integrated circuit from the TOPSwitch-GX family. The circuit shown in Figure 3 details a 19 V, 70 W supply that operates from an input range of 85 to 265 VAC, suitable for applications requiring either an open frame supply or an enclosed adapter. AC power is rectified and filtered by BR1 and C7 to create the high voltage DC bus applied to the primary winding of transformer (T1). Only a 150µF capacitor is required (2.1 µF/W) due to the wider DCMAX of TOPSwitch-GX and the line feed forward function provided by the LINE SENSE Pin. The other side of the primary is driven by the integrated high-voltage MOSFET within the TOP249Y. Diodes, D4 and D2 clamp the DRAIN voltage spike caused by transformer leakage inductance to a safe value below the 700 V maximum. Capacitor C6 is added in parallel with D2 to reduce zener clamp dissipation. The TOPSwitch-GX family provides new operating features and extended specifications. The EP11 power supply is designed using several of these features. Resistors R14 and R15 connected to the LINE SENSE pin (L) of TOPSwitch-GX (U1) are used to implement EPR-00011 - 70 W Adapter 22-Jan-01 Page 8 of 46 Power Integrations Inc Tel: +1 408 414 9200 Fax: +1 408 414 9201 www: http://www.powerint.com an under-voltage detect (100V), over-voltage shutdown (450V) and line feed forward with DCMAX reduction features. Two resistors are used in series to allow low cost ¼ W resistors which have a lower voltage rating. The under-voltage detect ensures that the output is glitch free at start-up and shutdown. With the combined value of R14 and R15 as shown, the power supply does not start operating until the DC rail voltage reaches 100 VDC. On removal of the AC input the UV sense prevents the output glitching as C7 discharges turning off the TOPSwitch-GX when output regulation is lost or when the input voltage falls to 40 V, whichever occurs first. The over-voltage feature shuts down the supply if the rectified input voltage exceeds approximately 450V. If exceeded this protects the TOPSwitch-GX from excessive drain voltages providing an extended AC surge withstand to 700 VDC (BVDSS rating), ideal for countries with poor power quality. Finally the line feed forward feature reduces output line frequency ripple by modulating the control loop with the line frequency ripple on the DC rail, ideal when using a relatively small input capacitor. Resistors R5, R6, and R12 connect to the EXTERNAL CURRENT LIMIT pin (X) and are used to externally program the current limit level of the device to just above the operating peak current at full load and low line. This allows use of a smaller transformer core and / or higher transformer primary inductance for a given output power. Reducing transformer size and TOPSwitch-GX power dissipation, while at the same time avoiding transformer core saturation during start-up or output load transient. This resistor network also reduces the current limit with increasing line voltage. This limits the maximum available power during overload conditions at high line (see Figure 10) removing the need for any protection circuitry on the secondary. The secondary windings are rectified and filtered by D1, D5, C1, and create the 19 V output voltage. Two windings are used, with separate dual rectifiers (for equal current sharing), to lower winding losses and maximise efficiency. Inductor L1 provided additional filtering in conjunction with C4 and C14. The 19 V output is directly sensed by the series combination of R4 and R13 that form a divider with R10. These resistors together with the reference node voltage of U3 set the output voltage. Other output voltages are also possible by adjusting the transformer turns ratios and value of R4 and R13. Resistor R2 sets the overall DC gain of the control loop and R7 provides bias for voltage reference U3. Capacitor C11 is the main compensation capacitor and together with R11, C9, R8 and C10 ensure stability of the control loop. The TOPSwitch-GX control circuit allows the switching frequency to reduce at light or zero load conditions, eliminating the need for a pre-load resistor to control the output EPR-00011 - 70 W adapter 22-Jan-01 Page 9 of 46 Power Integrations Inc Tel: +1 408 523 9200 Fax: +1 408 523 9300 www: http://www.powerint.com voltage at zero load. By lowering the switching frequency, no-load power consumption is also greatly reduced. The bias winding is rectified and filtered by D3, R3 and C8 to create a bias voltage to power the TOP249Y. A 1µF capacitor is required for C8 to maintain sufficient voltage during zero to full load transients. Resistor R8 provides leakage inductance filtering to prevent peak charging. A ceramic capacitor is shown for C8 however for lower cost an electrolytic type can be used. Common mode choke L3 and capacitor C12 attenuate common-mode emission currents caused by high-voltage switching waveforms on the drain side of the primary winding and the primary to secondary capacitance. Inductor L2 in conjunction with C5, C15 and C16 attenuate differential-mode emission currents caused by the fundamental and harmonics of the primary current waveform. Capacitor C16 provides a high frequency bypass of C7 which shortens the loop formed by these high frequencies passing through the transformer primary and thus reduces both the differential and common mode conducted noise. Frequency jitter is employed by the TOPSwitch-GX family to reduce the conducted noise as measured for both the CISPR and EN standards (see section 12) Capacitor C17 filters internal MOSFET gate-drive charge current spikes on the CONTROL pin and together with R11 and C11 determines the auto-restart frequency. EPR-00011 - 70 W Adapter 22-Jan-01 Page 10 of 46 Power Integrations Inc Tel: +1 408 414 9200 Fax: +1 408 414 9201 www: http://www.powerint.com 4 PCB Layout Figure 4 - PCB layout (not to scale) EPR-00011 - 70 W adapter 22-Jan-01 Page 11 of 46 Power Integrations Inc Tel: +1 408 523 9200 Fax: +1 408 523 9300 www: http://www.powerint.com 5 Bill of Materials EP11 - 19.2V, 3.66A Universal Input Flyback Item Qty. Reference Part Comment 1 1 BR1 RS805 2 3 C1, C2, C4 820uF 25V 3 1 C5 0.1uF X2 Safety 250VAC 4 1 C6 0.01uF 400V 5 1 C7 150uF 400V 6 1 C8 1.0uF 50V 7 1 C9 0.0047uF 50V 8 3 C10, C14, C17 0.1uF 50V 9 1 C11 47uF 16V 10 1 C12 .0022uF Y1 Safety 250VAC 11 1 C15 0.33uF 400V 12 1 C16 0.02uF 500V 13 2 D5, D1 MBR20100 14 1 D2 P6KE200A 15 1 D3 1N4148 16 1 D4 UF4006 17 1 F1 3.15A, 250V 18 1 J1 Molex Header 19 1 J2 Molex Header 20 1 L1 200uH (custom –see appendix) 21 1 L2 75uH (custom –see appendix) 22 1 L3 CM Choke 820uH 2.0A 23 1 RT1 10 Ohm 1.7A In-rush limiter (Keystone CL 120) 24 1 R2 270 1/8W 25 1 R3 4.7 1/8W 26 1 R4 31.6K 1/8W 1% 27 1 R5 7.5M 1/4W 28 1 R6 5.6M 1/4W 29 1 R7 1.0K 1/8W 30 1 R8 56K 1/8W 31 1 R10 4.75K 1/8W 1% 32 1 R11 6.8 1/8W 33 1 R12 20.5K 1/8W 34 1 R13 562 1/8W 1% 35 2 R14, R15 1M 1/4W 36 1 T1 PQ26/20 Core Transformer - revision F (custom – see appendix) 37 1 U1 TOP249Y 38 1 U2 PC817A 39 1 U3 TL431CLP 40 1 HS1 Copper Heat Sink EP11-HS1D 41 1 HS2 Copper Heat Sink EP11-HS2D EPR-00011 - 70 W Adapter 22-Jan-01 Page 12 of 46 Power Integrations Inc Tel: +1 408 414 9200 Fax: +1 408 414 9201 www: http://www.powerint.com 6 Transformer Documentation Transformer, T1 (rev. F) 2 1 SHIELD 9T # 26AWG x 2 12 9 3T# 26AWG x 3 T.I. 3 9T # 26AWG x 2 5 6 2 TURNS OF FOIL WDG #2 WDG #4 WDG #5 11 8 WDG #3 3T# 26AWG x 3 T.I. WDG #1 1 TURN OF FOIL CORE CONTACT ELECTRICAL SPECIFICATIONS: Electrical strength 60 Hz 1 minute, from Pins 2-6 to Pins 8-12 3000 VAC Primary Inductance Pins 1-3; all windings open. Measure at 130kHz 273µH +/-10% Resonant Frequency Pins 1-3; all windings open. 1.3 MHz (Min.) Primary leakage inductance Pins 1-3; Pins 8,9,11, 12 shorted. Measure at 130kHz. 3µH (Max) MATERIALS: Item Description [1] Core: FPQ26/20-A, TDK PC40 (or equivalent); gapped for ALG=843nH/T2 Lower loss ferrite can be substituted to obtain lower core temperatures. [2] Bobbin: TDK BPQ26/20-1112CP (or equivalent) [3] Magnet Wire: # 26 AWG Solderable Double Coated [4] Triple Insulated Wire: # 26AWG [5] Copper foil; 8mm wide Thickness=0.051mm (.002”) [6] Copper foil tape; 3M 1181 (or equivalent) 11mm wide [7] Tape: 3M 74 Polyester Film (or equivalent) 12mm wide [8] Tape: 3M 74 Polyester Film (or equivalent) 9.2mm wide [9] Varnish [10] Tape: 3M 1298 Polyester Film (or equivalent) 19.5mm wide EPR-00011 - 70 W adapter 22-Jan-01 Page 13 of 46 Power Integrations Inc Tel: +1 408 523 9200 Fax: +1 408 523 9300 www: http://www.powerint.com TRANSFORMER DIAGRAM: Pin Side Secondary [4] 1/2 Primary [3] Bias [5] Tape [6] Tape [6] Shield [5] 1 2 1 11 12 11 8 3 2 9 6 5 Tape [3] 1/2 Primary [3] SHIELD and BIAS Winding PREPARATION: (Top View before folding tape) (Cross Section) Copper Tape 12.0 65 for Shield and 120 for Bias Winding A 8.0 20.0 Copper Foil Tape 2.0 4.0 #26 copper wire (only one required for shield) (Top View after folding tape) Figure 1-A Figure 1-B Figure 1-C B EPR-00011 - 70 W Adapter 22-Jan-01 Page 14 of 46 Power Integrations Inc Tel: +1 408 414 9200 Fax: +1 408 4