EVLVIP27H-12SB

AN3011 Application note Wide range input (90 - 265), single output (5 V-11 W) EVLVIP27H-12SB, VIPer27 demonstration board Introduction In certain applications such as LCD or plasma TVs, desk top computers, etc., the power supply that converts the energy from the mains often includes two modules: the main power supply that provides most of the power which is off when the application is off or in standby mode, and the auxiliary power supply that only provides energy to specific parts of the equipment, like the USB ports, remote receivers, or modems, but stays on when the application is in standby mode. In standby mode it is often required that the equipment input power is as low as possible, which means reducing the input power of the auxiliary power supply, in no-load or light-load conditions, as low as possible. This demonstration board meets the specifications of a wide range of auxiliary power supplies for the above mentioned applications. Furthermore, it is optimized for very low standby consumption which helps to meet the most stringent energy saving requirements. Using the VIPer27, which has a switching frequency of 115 kHz, helps to reduce the transformer size. Figure 1. Demonstration board image !-V January 2011 Doc ID 16043 Rev 1 1/37 www.st.com Contents AN3011 Contents 1 2 3 Board descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.1 Electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.2 Schematic and bill of materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.3 Transformer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Testing the board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.1 Typical board waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.2 Precision of the regulation and output voltage ripple . . . . . . . . . . . . . . . . 11 Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.1 3.2 Light load performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3.1.1 No-load condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3.1.2 Low-load performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Test equipment and measurement of efficiency and input power . . . . . . 23 3.2.1 Measuring input power notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 3.3 Overload protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.4 Secondary winding short-circuit protection . . . . . . . . . . . . . . . . . . . . . . . 27 3.5 Output overvoltage protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 3.6 Brown-out protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 5 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 6 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 2/37 Doc ID 16043 Rev 1 AN3011 List of tables List of tables Table 1. Table 2. Table 3. Table 4. Table 5. Table 6. Table 7. Table 8. Table 9. Table 10. Table 11. Table 12. Table 13. Table 14. Table 15. Table 16. Table 17. Table 18. Table 19. Table 20. Table 21. Table 22. Electrical specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 BOM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Transformer characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Output voltage and VDD line-load regulation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Active-mode efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Line voltage average efficiency vs load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Energy efficiency criteria for standard models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Energy efficiency criteria for low voltage models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 No-load input power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Energy consumption criteria for no-load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Low-load performance. POUT = 30 mW (brown-out disabled) . . . . . . . . . . . . . . . . . . . . . . 19 Low-load performance. POUT = 30 mW (brown-out enabled) . . . . . . . . . . . . . . . . . . . . . . . 19 Low-load performance. POUT = 50 mW (brown-out disabled) . . . . . . . . . . . . . . . . . . . . . . 19 Low-load performance. POUT = 50 mW (brown-out enabled) . . . . . . . . . . . . . . . . . . . . . . . 20 Low-load performance. POUT = 100 mW (brown-out disabled) . . . . . . . . . . . . . . . . . . . . . 20 Low-load performance. POUT = 100 mW (brown-out enabled) . . . . . . . . . . . . . . . . . . . . . . 20 Low-load performance. POUT = 200 mW (brown-out disabled) . . . . . . . . . . . . . . . . . . . . . 21 Output power when the input power is 1 W (BR disabled) . . . . . . . . . . . . . . . . . . . . . . . . . 22 Output power when the input power is 1 W (BR enabled) . . . . . . . . . . . . . . . . . . . . . . . . . 22 Overvoltage protection activation level test results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Doc ID 16043 Rev 1 3/37 List of figures AN3011 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. Figure 24. Figure 25. Figure 26. Figure 27. Figure 28. Figure 29. Figure 30. Figure 31. Figure 32. Figure 33. Figure 34. Figure 35. Figure 36. Figure 37. Figure 38. 4/37 Demonstration board image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Transformer size - top view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Transformer size - side view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Pin placement diagram - bottom view. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Pin placement diagram - electrical diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Drain current and voltage at full-load 115 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Drain current and voltage at full-load 230 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Drain current and voltage at full-load 90 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Drain current and voltage at full-load 265 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Output voltage ripple 115 VINAC full-load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Output voltage ripple 230 VINAC full-load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Output voltage ripple 115 VINAC no-load (burst mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Output voltage ripple 230 VINAC 50 mA load (burst mode). . . . . . . . . . . . . . . . . . . . . . . . . 13 Efficiency vs VIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Efficiency vs load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Active mode efficiency vs VIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Input voltage average efficiency vs load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 ENERGY STAR efficiency criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Converter input power vs Vin_ac in light-load condition . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Converter efficiency vs Vin_ac in light-load condition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Efficiency vs AC input voltage when the input power is 1 W . . . . . . . . . . . . . . . . . . . . . . . 23 Wattmeter possible connections with the U.U.T. (unit under test) . . . . . . . . . . . . . . . . . . . 24 Wattmeter connection scheme for low input current. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Wattmeter connection scheme for high input current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Output short-circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Operation with output shorted. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Converter power capability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Second overcurrent protection - protection tripping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Operating with the secondary winding shorted. Restart mode . . . . . . . . . . . . . . . . . . . . . . 28 OVP circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 OVP protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 OVP protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 J7 jumper setting. Brown-out disabled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 J7 jumper setting. Brown-out enabled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Brown-out protection, internal block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Input AC voltage steps from 90 VAC to 65 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Input voltage steps from 90 VAC to 0 VAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Doc ID 16043 Rev 1 AN3011 Board descriptions 1 Board descriptions 1.1 Electrical specifications The electrical specifications of the demonstration board are listed in Table 1. Table 1. 1.2 Electrical specifications Parameter Symbol Value Input voltage range VIN [90 VRMS; 265 VRMS] Nameplate output voltage VOUTn 5V Max output current IOUT 2.2 A Precision of output regulation VOUT − VOUTn VOUTn ±5 % High frequency output voltage ripple ΔVOUT_HF 50 mV Max ambient operating temperature TA 60 °C Schematic and bill of materials The schematic of the board is shown in Figure 2, and the bill of materials is shown in Table 2. Doc ID 16043 Rev 1 5/37   +6     Schematic AN3011 Figure 2. %5  ') 0 X) 9 ' 1 0  677+/ '    & 5 & / X+    & & & X) 9 X) 9 X) 9 7 :( 5 0HJ  7  %$7 1 5 2879$ 6736   ' '    '  0HJ Q) ; + ( $ 7 6 ,1 . .( & 0HJ 5  & < Q)  Doc ID 16043 Rev 1 N  5 5 %85%/  N & Q) ; 2KP  X) 9 & (3&26      5 )% 5   6285&( Q) N  9] & ' Q) 76 5  N  N  N  & 5 95 5 N  ,1387>@9DF 6/37 !-V Board descriptions    5 N  Q) Q  & &217 5 %60  N 3& &21752/   W %5 & 17& '5$,1   5 2372    9'' 6(/(&725  ) $)8 6(  9,3(5+1 8 - AN3011 Table 2. Board descriptions BOM Part reference Description Part name Manufacturer BR1 Bridge diodes DF06M Fairchild/ Vishay C1,C13 100 nF X2 capacitor C3 33 µF 450 V electrolytic cap. C4 22 µF 35 V electrolytic cap. C5 N.M C6 1.8 nF ceramic cap C7 15 nF C8 2.2 nF Y1 capacitor C9, C14 ZL 1000 µF 16 V electrolytic cap. C10 YXF 47 µF 25 V electrolytic cap. YXF 47 µF 25 V C11 22 nF ceramic cap 22 nF C12 10 nF ceramic cap 10 nF D1 100 V small signal Schottky diode BAT46 D2 100 V small signal fast diode 1N4148 D3 600 V 1 A ultra-fast diode STTH1L06 STMicroelectronics D4 Power Schottky diode STPS745 STMicroelectronics D5 250 V Transil 1.5KE250 STMicroelectronics D6 18 V Zener F1 1 A Fuse HS1 Heat sink J7 Selector L1 3.3 µH 3 A inductor NTC1 15 Ω OPTO1 Opto-coupler R1 3.3 Ω resistor R3 33 kΩ 1% precision resistor R6 1 2kΩ 1% precision resistor R8 120 kΩ 1% precision resistor R9 39 kΩ 1% precision resistor R10 270 kΩ R12 47 kΩ R13 1.5 kΩ R14 180 kΩ 1% precision resistor R15 3.3 Meg 1% precision resistor RUBYCON RUBYCON STMicroelectronics EPCOS PC817 Doc ID 16043 Rev 1 SHARP 7/37 Board descriptions Table 2. AN3011 BOM (continued) Part reference Description R16, R17 2.7 Meg 1% precision resistor R18 47 kΩ 1% precision resistor R19 220 Ω T1 Part name Manufacturer Switch mode transformer WE - 750871012 Würth Elektronik T2 Common mode line filter BU15-4530R4BL Coilcraft U1 Offline switching regulator VIPER27HN STMicroelectronics VR1 Voltage reference TS431 STMicroelectronics 1.3 Transformer Transformer characteristics are listed in Table 3: Table 3. Transformer characteristics Properties Value Test condition Manufacturer Würth Elektronik Part number 750871012 Primary inductance 900 µH ±10 % Measured at 10 kHz 0.1 V Leakage inductance 25 µH max Measured at 100 kHz 0.1 V (primary and secondary windings shorted) Primary to secondary turn ratio (4 - 5) / (6, 7 – 8, 9) 14.75 ±1 % Measured at 10 kHz 0.1 V Primary to auxiliary turn ratio (6 - 4) / (3 - 1) 5.36 ±1 % Measured at 10 kHz 0.1 V Insulation 4 kV Primary to secondary Figure 3, 4, 5, and 6 show the size and pin distances (inches and [mm]) of the transformer. 8/37 Doc ID 16043 Rev 1 AN3011 Figure 3. Board descriptions Transformer size - top view Figure 4. Transformer size - side view   !-V Figure 5. Pin placement diagram - bottom view  !-V Figure 6. Pin placement diagram - electrical diagram  !-V Doc ID 16043 Rev 1 !-V 9/37 Testing the board AN3011 2 Testing the board 2.1 Typical board waveforms Figure 7 and 8 show the drain current and the drain voltage waveforms at the nominal input voltages, which are 115 VAC and 230 VAC when at maximum load (2.2 A). Figure 9 and 10 show the same waveforms for the same load condition, but with the input voltages at the minimum 90 VAC and the maximum 265 VAC. The converter is designed to operate in continuous conduction mode (in full-load condition) at low-line. CCM (continuous conduction mode) allows the reducing of the root mean square currents value, at the primary side, in the power switch inside the VIPer, and in the primary winding of the transformer; at the secondary side in the output diode (D4) and in the output capacitors (C9 and C14). Reducing RMS currents means reducing the power dissipation (mainly in the VIPer) and the stress on the above mentioned components. Figure 7. Drain current and voltage at fullload 115 VAC Figure 8. !-V Figure 9. Drain current and voltage at fullload 90 VAC !-V Figure 10. Drain current and voltage at fullload 265 VAC !-V 10/37 Drain current and voltage at fullload 230 VAC Doc ID 16043 Rev 1 !-V AN3011 2.2 Testing the board Precision of the regulation and output voltage ripple The output voltage of the board was measured in different line and load conditions. The results are given in Table 4. The output voltage is practically not affected by the line condition and only slightly affected by load condition (a difference of 10 mV between max and minimum VOUT, see Table 4). The VDD voltage was also measured. Table 4. Output voltage and VDD line-load regulation Full load Half load No load VINAC (V) VOUT (V) VDD (v) VOUT (V) VDD (V) VOUT (V) VDD (V) 90 5.073 21.1 5.078 20.00 5.083 9.98 115 5.073 20.98 5.078 20.02 5.083 9.83 230 5.073 20.94 5.077 20.08 5.083 9.30 265 5.073 20.98 5.077 20.04 5.083 9.17 In a two-output flyback converter, when just one output is regulated, the unregulated output does not rigorously respect the turn ratio. The unregulated output voltage value depends not only by the turn ratio but also, approximately, from the output currents ratio (output current at the regulated output divided by output current of the unregulated output). As confirmed from the results reported in Table 4, the VDD voltage (unregulated auxiliary output) increases as the load on the regulated output increases. In order to avoid the VDD voltage exceeding the VIPer27 operating range, an external clamp was used (D6, R19, see schematic). The ripple at the switching frequency superimposed at the output voltage was also measured. The board is provided with an LC filter for cleaner output voltage. The high frequency voltage ripple across capacitors C9 and C14 (VOUT_FLY), that is the output capacitors of the flyback converter before the LC filter (see schematic in Figure 2), was also measured to verify the effectiveness of the LC filter. The waveforms of the two voltages (VOUT and VOUT_FLY) are reported in Figure 11 and 12. The output voltage ripple when the converter input voltage is 115 VAC is shown in Figure 11, and the output voltage ripple when the converter input voltage is 230 VAC is shown in Figure 12. Doc ID 16043 Rev 1 11/37 Testing the board AN3011 Figure 11. Output voltage ripple 115 VINAC full-load #H6/54?&,9 #H6/54 #H6$2!). !-V The measured output voltage ripple is around 20 mV, well below the maximum admitted value (50 mV, see electrical specification in Table 1). Figure 12. Output voltage ripple 230 VINAC full-load #H6/54?&,9 #H6/54 #H6$2!). !-V When the device is working in burst mode, a lower frequency ripple is present. In this operation mode the converter does not supply continuous power to its output. It alternates periods when the power MOSFET is kept off, and no power is processed by the converter, and periods when the power MOSFET is switching and power flows towards the converter output. Even no-load is present at the output of the converter, during no switching periods the output capacitors are discharged by their leakage currents and by the currents needed to supply the circuitry of the feedback loop present at the secondary side. During the switching period the output capacitance is recharged. Figure 13 and 14 show the output voltage and the feedback voltage when the converter is no-loaded. In Figure 13 the converter is supplied with 115 VAC, and with 230 VAC in Figure 14. 12/37 Doc ID 16043 Rev 1 AN3011 Testing the board Figure 13. Output voltage ripple 115 VINAC no-load (burst mode) #H6 /54 #H) $2!). !-V Figure 14. Output voltage ripple 230 VINAC 50 mA load (burst mode) #H6 /54 #H) $2!). !-V Doc ID 16043 Rev 1 13/37 Efficiency 3 AN3011 Efficiency The efficiency of the converter was measured in different load and line voltage conditions. In accordance with the ENERGY STAR® active mode testing efficiency method, the measurements are done with different load values (full-load, 75%, 50%, and 25% of the fullload) for different input voltages. The results are given in Table 5 below. Table 5. Efficiency Efficiency (%) VINAC (VRMS) Full load (2.2 A) 75 % load (1.65 A) 50 % load (1.1 A) 25 % load (0.55 A) 90 73.0 75.1 76.9 77.9 115 75.3 76.5 77.9 78.1 132 75.9 76.9 77.8 77.7 175 76.8 77.3 77.6 76.4 230 77.4 77.6 77.3 75.4 265 76.8 76.9 76.3 74.2 For better visibility the results are plotted in the diagrams below. In Figure 15, efficiency versus converter AC input voltage (VIN), for four different load values, is plotted. In Figure 16, the value of efficiency versus load for different input voltages is plotted. Figure 15. Efficiency vs VIN (IILFLH QF\ (IILFLHQF\9V9 ,1$&               9,1$&9506 14/37 Doc ID 16043 Rev 1   !-V AN3011 Efficiency Figure 16. Efficiency vs load (IILFLHQF\9V3 287 (IILFLH QF\                     328 7:      !-V The active mode efficiency is defined as the average of the efficiencies measured at 25%, 50%, and 75% of maximum load and the maximum load itself. Table 6 shows the active mode efficiency calculated from the measured value of Table 5. The values in Table 6 are plotted in Figure 17. In Figure 18 the average value of the efficiency versus load is shown (the average was obtained considering efficiency at different input voltages). Table 6. Active-mode efficiency Active mode efficiency VINAC (VRMS) Efficiency (%) 90 75.8 115 77.0 230 76.9 265 76.1 Doc ID 16043 Rev 1 15/37 Efficiency AN3011 Figure 17. Active mode efficiency vs VIN (IILFLH QF\ $FWLYH0RG H(IILFLHQF\9V9 ,1B$&            9,1 B$& 9506  !-V Figure 18. Input voltage average efficiency vs load (IILFLH QF\ (IILFLHQF\$YHUDJHUHVSHFW9LQ9V3RX W        Table 7.   /2$'    !-V Line voltage average efficiency vs load Load (% of full load) Efficiency (%) 100 75.7 75 76.5 50 77.1 25 76.4 In version 2.0 of the ENERGY STAR® program requirement for single voltage external AC/DC power supplies (see References 2), the power supplies are divided into two categories: low voltage power supplies and standard power supply, with respect to the nameplate output voltage and current. An external power supply, in order to be considered a 16/37 Doc ID 16043 Rev 1 AN3011 Efficiency low voltage power supply, must have a nameplate output voltage lower than 6 V and a nameplate output current greater than or equal to 550 mA. Table 8 and 9 show the EPA energy efficiency criteria for AC/DC power supplies in active mode for standard models and for low voltage models respectively. Table 8. Energy efficiency criteria for standard models Nameplate output power (Pno) Minimum average efficiency in active mode (expressed as a decimal) 0 to = 1 W = 0.48 *Pno+0.140 > 1 to = 49 W = [0.0626 * In (Pno)] + 0.622 > 49 W = 0.870 Table 9. Energy efficiency criteria for low voltage models Nameplate output power (Pno) Minimum average efficiency in active mode (expressed as a decimal) 0 to = 1 W = 0.497 *Pno+0.067 > 1 to = 49 W = [0.075 * In (Pno)] + 0.561 > 49 W = 0.860 Figure 19. ENERGY STAR efficiency criteria : (IILFLHQF\  Ș Ș   VW  3QR OY  3QR        3QR 1DPHSODWHRXWSXW3RZHU !-V The criteria are plotted in Figure 19 above where the red line is the criteria for the standard model and the blue line is the criteria for the low voltage model. The PNO axe is in the logarithmic scale. The presented power supply belongs to the low voltage power supply category and, in order to be compliant with ENERGY STAR requirements, must have an efficiency higher than 74.1 % when the converter input voltage is at the nominal value (115 VAC or 230 VAC in this case). For all the considered input voltages the efficiency (see Table 6) results are higher than the required value. Doc ID 16043 Rev 1 17/37 Efficiency AN3011 3.1 Light load performance 3.1.1 No-load condition The input power of the converter was measured in no-load condition, with brown-out protection disabled (see relevant section) and brown-out protection enabled for different applied input voltages (see Table 10). The converter in no-load condition always works in burst mode so that the average switching frequency is strongly reduced. The average switching frequency values were also measured. The presence of the resistor dividers (R16, R17 and R18, see schematic of Figure 2) to sense the flyback input voltage, when brownout protection is enabled, does not affect the average switching frequency, but obviously affects the input power due to the power dissipated in the resistor divider itself. Table 10. No-load input power Pin (mW) Pin (mW) (BR enabled) (No BR) 90 19.20 16.80 1.0816 115 22.90 17.50 0.9706 132 25.00 18.60 0.9139 175 33.00 23.00 0.7552 230 48.00 29.00 0.6923 265 62.00 37.00 0.6561 Vin AC (VRMS) fSW_AVG (kHz) In the ENERGY STAR program version, the power consumption of the power supply when it is no-loaded is also considered. The compliance criteria is shown in Table 11: Table 11. Energy consumption criteria for no-load Nameplate output power (Pno) Maximum power in no-load for AC/DC EPS 0 to = 50 W < 0.3 W > 50 watts < 250 W < 0.5 W The performance of the demonstration board is far better then required, but it is worth noting that often the AC/DC adapter or battery charger manufacturer have stricter requirements regarding no-load consumption, compared to ENERGY STAR requirements, due also to other standards or recommendations which they want to be compliant with. In cases where the converter is used as the standby power supply for LCD TVs, PDPs or other applications, the line filter is often the big line filter of the main power supply which heavily contributes to the standby consumption, even though the power needed to the auxiliary power supply is very low. The ENERGY STAR program does not have other requirements regarding light-load performance, however the input power and efficiency of the demonstration board, also in other low load cases, is given in order to supply more complete information. 18/37 Doc ID 16043 Rev 1 AN3011 3.1.2 Efficiency Low-load performance The demonstration board was tested not only in no-load condition but also with a low-load applied. The tests were performed with 30 mW, 50 mW, 100 mW and 200 mW with brownout protection enabled and with brown-out protection disabled ● POUT = 30 mW Table 12. VIN_AC POUT (mW) PIN (mW) Eff. (%) PIN-POUT (mW) fSW_AVG (kHz) 90 29.48 51.60 57.13 22.12 3.731 115 29.48 54.40 54.19 24.92 3.375 132 29.48 55.00 53.60 25.52 3.155 175 29.48 59.60 49.47 30.12 2.814 230 29.48 69.00 42.73 39.52 2.876 265 29.48 74.00 39.84 44.52 2.534 Table 13. ● Low-load performance. POUT = 30 mW (brown-out disabled) Low-load performance. POUT = 30 mW (brown-out enabled) VIN_AC POUT (mW) PIN (mW) Eff. (%) PIN-POUT (mW) 90 29.48 54.80 53.80 25.32 115 29.48 57.90 50.92 28.42 132 29.48 62.30 47.32 32.82 175 29.48 69.80 42.24 40.32 230 29.48 87.00 33.89 57.52 265 29.48 101.00 29.19 71.52 POUT = 50 mW Table 14. Low-load performance. POUT = 50 mW (brown-out disabled) VIN_AC POUT (mW) PIN (mW) Eff. (%) PIN-POUT (mW) fSW_AVG (kHz) 90 54.39 85.90 63.32 31.51 6.248 115 54.39 87.40 62.23 33.01 5.663 132 54.39 88.20 61.66 33.81 5.314 175 54.39 94.80 57.37 40.41 5.259 230 54.39 104.00 52.30 49.61 4.845 265 54.39 111.00 49.00 56.61 4.299 Doc ID 16043 Rev 1 19/37 Efficiency AN3011 Table 15. ● VIN_AC POUT (mW) PIN (mW) Eff. (%) PIN-POUT (mW) 90 54.39 87.20 62.37 32.81 115 54.39 93.80 57.98 39.41 132 54.39 94.00 57.86 39.61 175 54.39 104.20 52.20 49.81 230 54.39 125.00 43.51 70.61 265 54.39 139.00 39.13 84.61 POUT = 100 mW Table 16. Low-load performance. POUT = 100 mW (brown-out disabled) VIN_AC POUT (mW) PIN (mW) Eff. (%) PIN-POUT (mW) fSW_AVG (kHz) 90 106 152 69.5 46 11.3 115 106 157 67.3 51 10.2 132 106 157 67.3 51 9.6 175 106 162 65.3 56 8.5 230 106 177 59.7 71 8.7 265 106 181 58.4 75 7.8 Table 17. 20/37 Low-load performance. POUT = 50 mW (brown-out enabled) Low-load performance. POUT = 100 mW (brown-out enabled) VIN_AC POUT (mW) PIN (mW) Eff. (%) PIN-POUT (mW) 90 106 155 68.2 49 115 106 159 66.5 53 132 106 166 63.7 60 175 106 174 60.8 68 230 106 195 54.2 89 265 106 206 51.3 100 Doc ID 16043 Rev 1 AN3011 Efficiency ● POUT = 200 mW Table 18. Low-load performance. POUT = 200 mW (brown-out disabled) VIN_AC POUT (mW) PIN (mW) Eff. (%) PIN-POUT (mW) fSW_AVG (kHz) 90 208.403 286 72.87 77.597 21.3115 115 208.403 293 71.13 84.597 19.2462 132 208.403 294 70.89 85.597 18.1681 175 208.403 296 70.41 87.597 16.0584 230 208.403 313 66.58 104.597 16.4671 265 208.403 328 63.54 119.597 14.7167 Low-load performance. POUT = 200 mW (brown-out enabled) VIN_AC POUT (mW) PIN (mW) Eff. (%) PIN-POUT (mW) 90 208.403 289 72.11 80.60 115 208.403 296 70.41 87.60 132 208.403 299 69.70 90.60 175 208.403 313 66.58 104.60 230 208.403 336 62.02 127.60 265 208.403 349 59.71 140.60 Figure 20. Converter input power vs Vin_ac in light-load condition 3 ,19V9 ,1B$& 1R%5 3 ,1  P:                    9 ,1 B$& 9 506  !-V Doc ID 16043 Rev 1 21/37 Efficiency AN3011 Figure 21. Converter efficiency vs Vin_ac in light-load condition (IILFLHQF\9V9 ,1B$&1R%5 (IILFLHQF\    3287                 9 ,1 B$&  9 5 06  !-V Depending on the equipment supplied, it’s possible to have several criteria to measure the standby or light-load performance of a converter. One of these is the measurement of the output power when the input power is equal to 1 watt. In Table 19 and 20, the output power needed to have 1 W of input power in different line conditions is shown, with BR disabled and with BR enabled respectively. Figure 22 shows the diagram of the efficiency (proportional to the output power) versus the input voltage when the input power is 1 W. Table 19. Output power when the input power is 1 W (BR disabled) VIN (VRMS) PIN (mW) POUT (mW) Efficiency (%) Pin-Pout (mW) 90 1000 737 73.70 263 115 1000 752 75.23 248 132 1000 757 74.74 243 175 1000 717 71.67 283 230 1000 686 68.62 314 265 1000 666 66.59 334 Table 20. Output power when the input power is 1 W (BR enabled) PIN POUT Efficiency Pin-Pout (mW) (mW) (%) (mW) 90 1000 737 73.70 263 115 1000 752 75.23 248 132 1000 742 74.21 258 175 1000 712 71.16 288 230 1000 676 67.60 324 265 1000 656 65.57 344 VIN (VRMS) 22/37 Doc ID 16043 Rev 1 AN3011 Efficiency Figure 22. Efficiency vs AC input voltage when the input power is 1 W (IILFLHQF\ZKHQ,QS XWSR ZHULV: (IILFLHQF\               9 ,1 B$& 9 506 3.2     !-V Test equipment and measurement of efficiency and input power The converter input power was measured using a wattmeter. The wattmeter contemporaneously measures converted input current (using its internal ammeter) and voltage (using its internal voltmeter). The wattmeter is a digital instrument, therefore, it samples the current and voltage and converts them into digital form. The digital samples are then multiplied giving the instantaneous measured power. The sampling frequency is in the range of 20 kHz (or higher depending on the instrument used). The display provides the average measured power, averaging the instantaneous measured power. Figure 23 shows how the wattmeter is connected to the UUT (unit under test) and to the AC source and the wattmeter internal block diagram. An electronic load was connected to the output of the power converter (UUT) sinking the load current. The electronic load also measures the load current. A voltmeter was used in order to measure the output voltage of the power converter. Once the input power and the output power can be measured, the efficiency in different operating conditions can be calculated by properly setting the AC source output voltage and the current sourced by the electronic load. 3.2.1 Measuring input power notes With reference to Figure 23, the UUT input current causes a voltage drop across the ammeter internal shunt resistance (the ammeter is not ideal so it has an internal resistance higher than zero) and across the cables that connect the wattmeter to the UUT. If the switch of Figure 23 is in position 1 (see also the simplified scheme of Figure 24) this voltage drop causes an input measured voltage higher than the input voltage at the UUT input which, of course, affects the measured power. The voltage drop is generally negligible if the UUT input current is low (for example, when measuring the input power of UUT in lowload condition). In the case of high UUT input current the voltage drop can be relevant (compared to the UUT real input voltage) and therefore, if this is the case, the switch in Figure 23 can be changed to position 2 (see simplified scheme of Figure 25) where the UUT Doc ID 16043 Rev 1 23/37 Efficiency AN3011 input voltage is measured directly to the UUT input terminal, and the input current does not affect the measured input voltage. The voltage across the voltmeter causes a leakage current inside the voltmeter itself (which is not ideal and which doesn't have infinite input resistance). If the switch in Figure 23 is in position 2 (see simplified scheme of Figure 25) the voltmeter leakage current is measured by the ammeter, together with the UUT input current, causing a measurement error. The error is negligible in a case where the UUT input current is much higher than the voltmeter leakage. If the UUT input current is low, and not much higher than the voltmeter leakage current, it is probably better to set the switch (in Figure 23) to position 1. In a case where it is not certain which measurement scheme least affects the results, it is possible to try with both and register the input power lower value. Figure 23. Wattmeter possible connections with the U.U.T. (unit under test) 6ZLWFK  :$770(7(5  887 8QLW8QGHUWHVW 9ROWPHWHU $& 6285&(  9 $ 0XOWLSOLHU ; $PPHWHU ,1387 287387 $9* ',63/$