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December 2010 Doc ID 17230 Rev 1 1/31

AN3172

Application note

19 V - 90 W adapter with PFC for laptop computers

using the L6563H and L6599A

Introduction

This application note describes the performance of a 90 W, wide-range mains, power-factor-

corrected, AC-DC adapter demonstration board. Its electrical specification is tailored on a

typical hi-end portable computer power adapter.

The architecture is based on a two-stage approach; a front-end PFC pre-regulator based on

the L6563H TM PFC controller and a downstream LLC resonant half-bridge converter using

the new L6599A resonant controller. Thanks to the chipset used, the main aspects of this

design are very high efficiency, compliance with ENERGY STAR

Eligibility Criteria (EPA

rev. 2.0 EPS), and very low input consumption at no-load (<0.3 W).

Figure 1. EVL6599A-90WADP: 90 W adapter demonstration board

www.st.com

Summary of content (31 pages)

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AN3172 Application note 19 V - 90 W adapter with PFC for laptop computers using the L6563H and L6599A Introduction This application note describes the performance of a 90 W, wide-range mains, power-factorcorrected, AC-DC adapter demonstration board. Its electrical specification is tailored on a typical hi-end portable computer power adapter.
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Contents AN3172 Contents 1 2 Main characteristics and circuit description . . . . . . . . . . . . . . . . . . . . . 5 1.1 Startup sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.2 Brownout protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.3 Fast voltage feed forward . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.4 Resonant power stage . . . . . . . . . . . . . . .
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AN3172 List of figures List of figures Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Figure 7. Figure 8. Figure 9. Figure 10. Figure 11. Figure 12. Figure 13. Figure 14. Figure 15. Figure 16. Figure 17. Figure 18. Figure 19. Figure 20. Figure 21. Figure 22. Figure 23. EVL6599A-90WADP: 90 W adapter demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Electrical diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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List of tables AN3172 List of tables Table 1. Table 2. Table 3. Table 4. Table 5. Table 6. Table 7. 4/31 Overall efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Light-load efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Thermal maps reference points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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AN3172 1 Main characteristics and circuit description Main characteristics and circuit description The main features of the SMPS are: ● Universal input mains range: 90÷264 Vac - frequency 45 ÷ 65 Hz ● Output voltage: 19 V at 4.75 A continuous operation ● Mains harmonics: Acc. to EN61000-3-2 Class-D or JEITA-MITI Class-D ● Standby mains consumption: <0.
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Main characteristics and circuit description 1.1 AN3172 Startup sequence As previously indicated, the PFC acts as master and the resonant stage can operate only if the PFC output is delivering its nominal output voltage. Therefore the circuit is designed so that at startup the PFC starts first, then the downstream converter turns-on.
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AN3172 1.3 Main characteristics and circuit description Fast voltage feed forward Voltage on the L6563H VFF pin (#5) has the same value as the peak value of the voltage on the MULT pin (#3) and it is generated by the RC network (R15+R26, C12) connected to VFF, completing an internal peak-holding circuit. This signal is necessary to derive information on the RMS input voltage to compensate the loop gain which is mains voltage dependent.
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Main characteristics and circuit description 1.5 AN3172 Output voltage feedback loop The feedback loop is implemented by means of a typical circuit using a TL431 modulating the current in the optocoupler diode. On the primary side, R34 - connecting pin RFMIN (#4) to the optocoupler’s phototransistor closes the feedback loop and its value sets the maximum switching frequency at about 130 kHz. This value has been chosen to limit the switching losses at light-load operation.
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AN3172 1.8 Main characteristics and circuit description Standby power saving The board implements a burst-mode function allowing a significant power saving during light-load operation. The L6599A’s STBY pin (#5) senses the optocoupler’s collector voltage which is related to the feedback control and is proportional to the output load. This signal is compared to an internal reference (1.
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& X) 5 . 5 . 5 0 5 0 & Q ) 5 5 5 . & Q ) 5 1 0 5 0HJ & Q) - 0.'6 ' 1 0 ' 1 0 5 . & Q) 5 . & 1 0 5 1 0 ' & Q) B 5 1 0 4 1 0 5 5 1& +96 ' 1 0 5 . & X) 3:0 /$7&+ 3)& 2. 3:0 6723 7%2 =&' 581 9)) &6 *' *1' 08/7 9&& 8 / + 5 . a ' *%8 - &203 ,19 3&% 5(9 = & S) & 5 Q) .
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AN3172 Efficiency measurement EPA rev. 2.0 external power supply compliance verification. Table 1 shows the no-load consumption and the overall efficiency, measured at the nominal mains voltages. At 115 Vac the average efficiency is 89.96 %, while at 230 Vac it is 91.12 %. Both values are much higher than the minimum required by EPA rev2.0 External power supply limits (87 %). Measurements are also given in Figure 3 for reference.
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Efficiency measurement 2.1 AN3172 Light-load operation efficiency Measurement results are given in Table 2 and plotted in Figure 4. As seen, efficiency is better than 55 % even for very light loads such as 500mW. Table 2. Light-load efficiency Test 230 V - 50 Hz 115 V - 60 Hz Vout Iout Pout Pin Eff. Vout Iout Pout Pin Eff. [V] [mA] [W] [W] [%] [V] [mA] [W] [W] [%] 0.25 W 18.89 13.06 0.247 0.643 38.37 % 18.89 13.06 0.247 0.62 39.60 % 0.5 W 18.89 26.83 0.507 0.
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AN3172 Harmonic content measurement 3 Harmonic content measurement The board has been tested according to the European standard EN61000-3-2 Class-D and Japanese standard JEITA-MITI Class-D, at both the nominal input voltage mains. As shown in Figure 5 and 6, the circuit is able to reduce the harmonics well below the limits of both regulations. Figure 5. Compliance to EN61000-3-2 at 230 Vac - 50 Hz, full load 0HDVXUHG YDOXH Figure 6.
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Functional check 4 AN3172 Functional check The following are some waveforms relevant to the resonant stage during steady-state operation. The selected switching frequency is about 100 kHz, in order to have a good trade off between transformer losses and dimensions. The converter operates above the resonance frequency. Figure 8 shows the resonant ZVS operation. It is worth noting that both MOSFETs are turned on when resonant current is flowing through their body diodes and drain-source voltage is zero.
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AN3172 Figure 9. Functional check Rectifier waveforms Figure 10. Startup waveforms CH1: D23 anode voltage CH2: D24 anode voltage CH1: HB voltage CH3: D23 current CH4: D24 current CH3: Vcc 4.1 CH2: Vout PFC CH4: Output voltage Standby and no-load operation In Figure 11 and Figure 12, some burst-mode waveforms are given. As seen, both L6599A and L6563H operate in burst-mode. In Figure 11 it may also be noted that PFC and LLC bursts are synchronized. Figure 11.
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Functional check AN3172 Figure 13. Transition full load to no-load at 265 Figure 14. Transition no-load to full load at 265 Vac - 50 Hz Vac - 50 Hz CH1:HB voltage CH3:D23 Anode 4.2 CH2:Vcc CH1:HB voltage CH4:Output current CH3:D23 Anode CH2:Vcc CH4:Output current Overcurrent and short-circuit protection The L6599A is equipped with a current sensing input (pin #6, ISEN) and a dedicated overcurrent management system.
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AN3172 Functional check Figure 15. Short-circuit at full load and 115 Vac - 60 Hz CH1: HB Voltage CH3: DELAY pin CH4: Output current In Figure 15 the narrow operating time with respect to the off time of the converter may be seen; consequently, the average output current, as well as the average primary current, are very low, avoiding over-heating of components and consequent failure.
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Thermal map 5 AN3172 Thermal map In order to check the design reliability, a thermal mapping by means of an IR Camera was done. In Figure 16 and 17 the thermal measurements of the board, component side, at nominal input voltage, are shown. Some pointers, visible in the images, have been placed across key components or showing high temperature. The ambient temperature during both measurements was 27 °C. Figure 16. Thermal map at 115 Vac - 60 Hz - full load Figure 17.
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AN3172 Thermal map Table 3.
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Conducted emission pre-compliance test 6 AN3172 Conducted emission pre-compliance test The following figures are the average measurement of the conducted noise at full load and nominal mains voltages. The limits shown in the images are EN55022 Class-B, which is the most popular standard for domestic equipment and has more severe limits compared to Class-A, dedicated to IT technology equipment. As seen in Figure 18 and 19, in all test conditions the measurements are far below the limits. Figure 18.
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AN3172 BOM list 7 BOM list Table 4. EVL6599A-90WADP demonstration board: BOM list Des. Part type/ Case style Part value /Package Description 9.0 × 18.0 p.
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BOM list Table 4. Des. AN3172 EVL6599A-90WADP demonstration board: BOM list (continued) Part type/ Case style Part value /Package Description 9.0 × 18.0 p.15 mm X2 - MKP film cap - B32922C3474K Supplier C4 470 nF C40 100 nF 1206 50 V cercap - general purpose AVX C43 4n7F 1206 50 V cercap - general purpose AVX C44 10 nF 1206 50 V cercap - general purpose AVX C45 220 nF 0805 25 V cercap - general purpose AVX C46 N.M. 0805 Not mounted C5 470 nF 7.0 x 16.0 p. 22.
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AN3172 Table 4. BOM list EVL6599A-90WADP demonstration board: BOM list (continued) Part type/ Case style Part value /Package D9 STPS1L60A SMA F1 FUSE T4A 8.5x4 p.5.08mm Fuse 4A - time lag - 3921400 HS1 HEAT-SINK DWG Heat sink for D1, Q1, Q3, Q4 HS2 HEAT SINK DWG Heat sink for D23, D24 J1 MKDS 1,5/ 3-5,08 DWG PCB term. block, screw conn.,pitch 5mm 3 W. Phoenix contact J2 MKDS 1,5/ 2-5,08 DWG PCB term. block, screw conn.,pitch 5mm 2 W.
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BOM list Table 4. AN3172 EVL6599A-90WADP demonstration board: BOM list (continued) Part type/ Case style Part value /Package R21 39 R 0805 SMD STD film res, 1/8 W, 5 %, 250 ppm/°C VISHAY R22 0R47 PTH SFR25 axial stand. film res, 0.4 W, 5 %, 250 ppm/°C VISHAY R23 0R68 PTH SFR25 axial stand. film res, 0.
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AN3172 Table 4.
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PFC coil specification 8 AN3172 PFC coil specification General description and characteristics: ● Application type: consumer, home appliances ● Transformer type: open ● Coil former: vertical type, 6+6 pins ● Max. temp. rise: 45 ºC ● Max. operating ambient temperature: 60 ºC ● Mains insulation: n.a. ● Unit finishing: varnished Electrical characteristics: ● Converter topology: boost, transition mode ● Core type: PQ26/20-PC44 or equivalent ● Min.
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AN3172 8.1 PFC coil specification Mechanical aspect and pin numbering ● Maximum height from PCB: 22 mm ● Coil former type: vertical, 6+6 Pins (Pins #1, 2, 4, 6, 7, 10, and 12 are removed) ● Pin distance: 3.81 mm ● Row distance: 25 mm ● External copper shield: not insulated, wound around the ferrite core and including the coil former. Height is 8 mm. Connected to pin #3 by a soldered solid wire. Figure 21. PFC coil mechanical aspect Manufacturer: ● MAGNETICA, R.
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Transformer specifications 9 AN3172 Transformer specifications General description and characteristics: ● Application type: consumer, home appliances ● Transformer type: open ● Coil Former: horizontal type, 7+7 pins, two slots ● Max. temp. rise: 45 ºC ● Max. operating ambient temperature: 60 ºC ● Mains insulation: Acc. with EN60065 Electrical characteristics: ● Converter topology: half-bridge, resonant ● Core type: ETD34-PC44 or equivalent ● Min.
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AN3172 9.1 Transformer specifications Mechanical aspect and pin numbering ● Maximum Height from PCB: 30mm ● Coil Former Type: horizontal, 7+7 pins (pins #1 and 7 are removed) ● Pin distance: 5.08mm ● Row distance: 25.4mm Figure 23. Transformer overall drawing Manufacturer: ● MAGNETICA, R. Volpini - Italy ● Transformer P/N: 1860.
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Revision history 10 AN3172 Revision history Table 7.
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AN3172 Please Read Carefully: Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any time, without notice. All ST products are sold pursuant to ST’s terms and conditions of sale.