1、 Design Example Report Title 15 W, Multiple Output, Isolated Power Supply using TOP244P SpecificationInput: 85-265 VAC Output: 5V/0.1A, 12V/0.2A, 24V/0.5A Application Refrigerator Author Power Integrations Applications Department Document Number DER-28 Date March 30, 2004 Revision 1.0 Summary and Fe
2、atures Low cost (low component count with single sided printed circuit board) Meets EN/UL 1000-4-5 CLASS 4 (4 kV), using line overvoltage protection feature Designed to IEC60950 safety standard requirements Compact Design (L = 113 mm, W = 39 mm, H = 25 mm) High efficiency (73% at 85 VAC) Line underv
3、oltage shutdown prevents turn-off output glitches Line overvoltage shutdown provides extended line swell protection Hysteretic thermal shutdown provides automatic supply recovery after fault removal Power Integrations, Inc. 5245 Hellyer Avenue, San Jose, CA 95138 USA. Tel: +1 408 414 9200 Fax: +1 40
4、8 414 9201 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 lis
5、t of Power Integrations patents may be found at . DER-28 15 W, Multiple Output, Isolated Power Supply March 30, 2004 Table Of Contents 1 Introduction.3 2 Power Supply Specification 4 3 Schematic.5 4 Circuit Description 6 5 PCB Layout 9 6 Bill Of Materials 10 7 Transformer Specification.11 7.1 Electr
6、ical Specifications 11 7.2 Materials .11 7.3 Transformer Build Diagram.12 7.4 Transformer Construction .12 7.5 Design Notes 13 8 Transformer Spreadsheets.15 9 Performance Data 16 9.1 Efficiency.16 9.2 Regulation.17 9.2.1 Load.17 9.2.2 Line17 9.2.3 Cross-Regulation Table .18 10 Waveform Scope Plot.19
7、 11 Revision History20 Important Notes: 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 R
8、eports 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 22 Power Integrations, Inc. Tel: +1 408 414 9200 Fax: +1 4
9、08 414 9201 DER-28 15 W, Multiple Output, Isolated Power Supply March 30, 2004 1 Introduction This document is an engineering report describing a low cost, isolated converter for a appliance application. Included is the power supply specification, schematic, Bill of materials, transformer documentat
10、ion, printed circuit layout, and performance data. +24V RTN+12V RTN+5V RTN Figure 1 Populated Circuit Board (L x W x H: 113 mm x 39 mm x 25mm). 2 Input AC Page 3 of 22 Power Integrations, Inc. Tel: +1 408 414 9200 Fax: +1 408 414 9201 DER-28 15 W, Multiple Output, Isolated Power Supply March 30, 200
11、4 Power Supply Specification Description Symbol Min Typ Max Units Comment Input Voltage V IN85 265 VAC 50/60 Hz Output Output Voltage 1 V OUT14.75 5 5.25 V 5% Total Output Ripple Voltage 1 V RIPPLE175 mV Peak to Peak, 20 MHz BW Output Current 1 I OUT10.05 0.1 A Output Voltage 2 V OUT211.04 12 12.96
12、VDC 8% Total Output Ripple Voltage 2 V RIPPLE275 mV Peak to Peak, 20 MHz BW Output Current 2 I OUT20.05 0.2 A Output Voltage 3 V OUT321.1 24 26.9 VDC 12% Total Output Ripple Voltage 3 V RIPPLE3150 mV Peak to Peak, 20 MHz BW Output Current 3 I OUT30.05 0.5 A Total Output Power Continuous Output Power
13、 P OUT15 W Full Load Efficiency 73 % Full Load, 25o C, V IN(MIN)Ambient Temperature T AMB_EXT 0 25 50 o C External Ambient Range Page 4 of 22 Power Integrations, Inc. Tel: +1 408 414 9200 Fax: +1 408 414 9201 DER-28 15 W, Multiple Output, Isolated Power Supply March 30, 2004 3 Schematic D2 2 TOPSwit
14、ch-GX + C1 33 uF 400V R8 10 ohm F1 3.15A,250VAC J2-6 R2 1M J1-1 R9 100 ohm + C9 100uF R1 150k/ 1/2W 10V + C6 820 uF D6 1N4148 R11 15k 1% 3 R3 1M D7 MUR220 R12 10.0K 1% 16V D4 T1 EI25 1 2 9 7 6 10 D1 J2-4 J2-2 R6 75 16 V + C14 1uF 50V Control U1 TOP244P D S C M F J1-3 J2-1 16V + C4 470uF 50V U3 LM431
15、BCZ 1% 1N4007 X 4 5V 0.1A R4 6.8 Ohms D8 B380 C10 0.1uF U2 LTV817A 4 3 + C3 10 V 47 uF C2 1nF/1kV D9 SB540 Line L2 3.3uH 24V 0.5 A R10 100k 1% 20mH/0.4A L1 R13 12k J2-3 + C5 820uF U3 1 2 0.1 uF C11 L3 3.3uH C13 2.2nF 12V 0.2A D5 1N4007 J2-5 Neutral D3 1 R7 1k + C8 100uF 0.1UF 250VAC X-SAFETYC4 C15 5
16、 4 4 5Figure 2 Circuit Schematic. Page 5 of 22 Power Integrations, Inc. Tel: +1 408 414 9200 Fax: +1 408 414 9201 DER-28 15 W, Multiple Output, Isolated Power Supply March 30, 2004 4 Circuit Description This circuit is a low-cost multi-output Flyback switching power supply designed for appliance app
17、lications using the TOP244P integrated circuit. The circuit schematic details a 15 W, 3 output (5 VDC, 12 VDC and 24 VDC) power supply that operates from an 85 VAC to 265 VAC input. The high efficiency (73%) allows the power supply to operate within specifications at elevated ambient temperature. Th
18、e AC input is rectified and filtered by D1 to D4 and C1 to create a high voltage DC bus that is connected to transformer T1. The other side of T1 is driven by the high-voltage MOSFET of TOP244P 1(U1). Fuse F1 protects against primary-side components failures, while U1 protects against secondary comp
19、onents failures, and overloaded/shorted outputs. The combined value of the line sensing resistors R2 and R3, connected to the MULTI- FUNCTION (M) pin of U1, sets the undervoltage and overvoltage thresholds and provides a line feed forward function. On increasing line voltage, the power supply is inh
20、ibited until the undervoltage (UV) threshold is reached (100 VDC). On reducing line voltage, the UV function turns off the power supply when the line input voltage is below the UV threshold and the output goes out of regulation. This allows the power supply to continue operating at input voltages si
21、gnificantly below the UV threshold until output regulation is lost, but eliminates output glitches by preventing restart until the input voltage goes back above the UV threshold. The overvoltage function turns off the power supply if the input voltage exceeds approximately 450 V. In the off state, t
22、he power supply can withstand severe line transients or extended line swell conditions without damage. The supply resumes operation when the input voltage falls below the overvoltage threshold. The line feed forward function independently modulates the duty cycle of U1 to reject the AC line frequenc
23、y ripple component of the input voltage, reducing the line frequency ripple at the output of the supply. The output ripple specifications can be met without increased control loop gain since line feed forward operates independent of the main control loop. This simplifies the design of the power supp
24、ly control loop. A low cost RCD (R1, C2, R9 and D5) snubber circuit limits the turn-off voltage spike (caused by the leakage inductance) to a safe level on the DRAIN pin of U1. Resistor R9 is required in series with the slow recovery diode (D5) to reduce the diode reverse recovery spike and damp the
25、 subsequent oscillations which might allow the drain to ring below source at low line. 1The “P” and “G” packages allow either line sensing or external current limit programming through the M pin. “Y” and “R” packages allow both functions via the L and X pins. Reducing the current limit in this desig
26、n would allow a smaller transformer to be used, if desired. Page 6 of 22 Power Integrations, Inc. Tel: +1 408 414 9200 Fax: +1 408 414 9201 DER-28 15 W, Multiple Output, Isolated Power Supply March 30, 2004 The bias winding is rectified and filtered by D6 and C11 to power U1. Capacitor C3 is used to
27、 decouple the CONTROL pin, determine the auto-restart frequency and together with R4, forms part of the control loop compensation. The secondary winding is rectified and filtered by D7, R5, C4 (24 V) D8, C5 (12 V) and D9, C7, C8 (5 V), with additional switching frequency ripple and high frequency sp
28、ike noise filtering provided by L2, C8 (12 V) and L3, C9 (5 V) to give the DC outputs. The choice of Schottky diodes for the 5 V and 12 V outputs was driven by both voltage regulation and efficiency considerations. The snubber (C13 and R8) reduces the 10 MHz to 30 MHz conducted EMI due secondary lea
29、kage inductance. The current through the pre-load resistor R13 adds to the spec minimum load to keep the 24 V output in regulation. The 3.3 V and 5 V output voltages are determined by the voltage set at the adjust pin of U3 (shunt regulator) by the voltage divider formed by R10, R11 and R12. The cur
30、rent through R12 sets the output voltages, while the current contribution of R10 and R11 sets the regulation band for 12 V and 5 V outputs, respectively. Other output voltages are possible by adjusting the transformer turns ratios, choosing the output diodes forward voltage drops and voltage divider
31、 settings. Optocoupler U2 applies the feedback signal from U3 to the CONTROL pin of U1. Resistor R6 is used to set the overall gain of the supply control loop, while R7 provides bias current for U3. Capacitor C10 provides frequency compensation for U3 stabilizing the power supply control loop. Capac
32、itor C14 is used to close the feedback loop (bypassing U3) through optocoupler U2 during start-up, before U3 takes over the control loop. The ability to close the feedback loop in conjunction with the built-in soft- start feature of TOPSwitch-GX completely controls the start-up drain current profile
33、, preventing transformer saturation and output overshoot. The 5 V and 12 V secondary layout switching loops are minimized and, along with closely coupled transformer secondary windings, achieve low secondary leakage inductance and in turn, good cross-regulation. Optimizing the number of primary turn
34、s minimizes leakage. This also reduces the number of primary layers and improves primary to secondary coupling. The power supply meets IEC60950/UL1950 safety requirements. Primary-to-secondary isolation is assured by using parts/materials (opto/transformer insulation) with the correct level of isola
35、tion and creepage distances (opto slot/transformer bobbin). The power supply passed IEC/UL 1000-4-5, Class 4 line surge test (Class 3 only is required). All three outputs had monitor LEDs that showed no output disruption during the 90 high voltage surge pulses of Class 3. During Class 4 testing the
36、outputs were disrupted for one second (LEDs blinked indicating the operation of the overvoltage shutdown feature) when applying the 2 kV, 2 differential pulse and the 4 kV, 2 differential pulses (L1/GND, L2/GND) and were unaffected during the 4 kV, 12 common-mode pulses (L1, L2/GND). Page 7 of 22 Po
37、wer Integrations, Inc. Tel: +1 408 414 9200 Fax: +1 408 414 9201 DER-28 15 W, Multiple Output, Isolated Power Supply March 30, 2004 The switching frequency jitter of TOP244 (U1) allows the unit to meet worldwide conducted EMI standards using a low cost, common-mode inductor (L1) in combination with
38、a small value capacitor (C15). Careful transformer construction and PCB layout eliminate the need for a Y-rated capacitor between primary and secondary. Removal of the Y cap is necessary in voice applications to eliminate line frequency audio hum (“ground loops”). The common-mode inductance of L1 an
39、d the transformer construction attenuate common-mode conducted emission currents caused by the switching waveform on the DRAIN of U1, charging and discharging various stray capacitances. The differential inductance of L1 together with C15 attenuate differential-mode emission currents caused by the f
40、undamental and harmonics of the primary current waveform. Page 8 of 22 Power Integrations, Inc. Tel: +1 408 414 9200 Fax: +1 408 414 9201 DER-28 15 W, Multiple Output, Isolated Power Supply March 30, 2004 5 PCB Layout Figure 3 Printed Circuit Layout. Actual Size Board (L = 113 mm, W = 39 mm, H = 25
41、mm). Layout shown in Figure 3 is for an unmodified EP18 demo board; the secondary circuit has been modified for this prototype. For the drain-to-source voltage waveforms, connect the high voltage probe tip to TP2 and the probe ground to test point TP1. For switching current waveforms, add a wire loo
42、p in the provided holes and cut open the copper trace. Use a Tektronix A6302 current probe and AM503 current probe amplifier (with TM501 power module) or equivalent. Page 9 of 22 Power Integrations, Inc. Tel: +1 408 414 9200 Fax: +1 408 414 9201 DER-28 15 W, Multiple Output, Isolated Power Supply Ma
43、rch 30, 2004 6 Bill Of Materials Bill Of Materials Item Qty. Ref. Description Part number Manufacturer 1 1 C1 33 F, 400 V,105 C KMX400VB33 UCC 2 1 C2 1 nF, 1 kV, 6.5 mm, LS = 6.4mm Philips Centra 3 1 C3 47 F, 10 V KME10VB47RMX11LL UCC 4 1 C4 470 F, 50 V 5 2 C5-C6 820 F 16 V / 1000 F, 16 V EEU-FC1C82
44、1 / LXZ216VB102M10X20LL Panasonic UCC 6 1 C8 100 F, 16 V 7 1 C9 100 F, 10 V 8 2 C10,11 0.1 F, 50 V K104M15Z5UF5TH5 BC 9 1 C13 2200 pF, 100 V, multilayer cer. C315C222K1R5CA Kemet 10 1 C14 1 F, 50 V, ceramic Any 11 1 C15 0.1 F 250 VAC, X1 F1772-410-2000 Vishay 12 5 D1-D5 1 A, 1000 V 1N4007 General Se
45、mi. 13 1 D6 0.15 A, 75 V, 4 ns 1N4148 General Semi. 14 1 D7 2 A, 200 V, 50 ns MUR220 On Semi. 15 1 D8 3 A, 80 V, Schottky B380 General Semi. 16 1 D9 5 A, 40 V, Schottky SB540 General Semi. 17 1 F1 250 VAC, 3.15 A 19372K Wickman 18 1 J1 HEADER 3 26-48-1031 Molex 19 1 J2 HEADER 6 26-48-1061 Molex 20 1
46、 L1 20 mH, 0.4 A SS11V-05230 Tokin 21 2 L2, L3 3.3 H, 2.66 A 822MY-3R3M Toko 22 1 R1 150 k, 1/2 W Any 23 2 R2, R3 1 M, 1/4 W Any 24 1 R4 6.8 , 1/4 W Any 25 1 R8 10 , 1/4 W Any 26 1 R6 75 , 1/4 W Any 27 1 R7 1 k, 1/4 W Any 28 1 R9 100 , 1/4 W Any 29 1 R10 100 k 1%, 1/4 W Any 30 1 R11 15 k 1%, 1/4 W A
47、ny 31 1 R12 10.0 k 1%, 1/4 W Any 32 1 R13 12 k, 1/4 W Any 33 1 T1 EI25 XFMR (custom) SIL6008 Rev D HiCal 34 1 U1 TOPSwitch-GX TOP244P Power Integrations 35 1 U2 Optocoupler LTV817A Liteon 36 1 U3 Shunt Regulator, 2.5 V 1% LM431BCZ National Semiconductor Page 10 of 22 Power Integrations, Inc. Tel: +1
48、 408 414 9200 Fax: +1 408 414 9201 DER-28 15 W, Multiple Output, Isolated Power Supply March 30, 2004 7 Transformer Specification 61T #29 AWG 7T #29AWG X 3 7T #26 AWG T.I. 4T #26 AWG X3 T.I. 3T #26 AWG X 3 T.I. Figure 4 - Transformer Electrical Diagram. 7.1 Electrical Specifications Electrical Strength 1 minute, 60 Hz, from Pins 1-5 to Pins 6-10 3000 VAC Primary Inductance Pins 1-2, all windings open, 130 kHz measurement frequency 397 H +/-10% Resonant Frequency Pins 1-2, all windings open 0.5 MHz minimum Primary Leakage Inductance Pin
