NCP1380EVB/D Performances of a Quasi-Resonant Adapter Driven by the NCP1380 Prepared by Stéphanie Conseil http://onsemi.com ON Semiconductor resulting in an unstable operation and noise in the transformer at medium and light output loads. In order to overcome this problem, the NCP1380 features a “valley lockout” circuit: the switching frequency is decreased step by step by changing valley as the load decreases. Once the controller selects a valley, it stays locked in this valley until the output power changes significantly. This technique extends the QR operation of the system towards lighter loads without degrading the efficiency. This application note focuses on the experimental results of an adapter driven by the NCP1380. Quasi−square wave resonant converters also known as quasi−resonant (QR) converter are widely used in the adaptor market. They allow designing flyback Switched−Mode Power Supply (SMPS) with reduced Electro−Magnetic Interference (EMI) signature and improved efficiency. However, as the switching frequency of QR converter increases as the load decreases, the frequency must be limited. In traditional QR converter, the frequency is limited by a frequency clamp. But, when the switching frequency of the system reaches the frequency clamp limit, valley jumping occurs: the controller hesitates between two valleys Specifications of the Adapter The adapter is designed to meet the following specifications: Table 1. SPECIFICATIONS OF THE 19 V, 60 W ADAPTER Parameter Symbol Value Minimum input voltage Vin,min 85 Vrms Maximum input voltage Vin,max 265 Vrms Vout 19 V Pout(nom) 60 W Fsw 45 kHz Output voltage Nominal output power Switching frequency at Vin,min, Pout(nom) Description of the Board The 60 W adapter has been designed using the method described in the application note AND8431/D [1]. © Semiconductor Components Industries, LLC, 2009 December, 2009 − Rev. 1 The B version of NCP1380 has been chosen to drive the adaptor. 1 Publication Order Number: NCP1380EVB/D http://onsemi.com 2 R30 100k Figure 1. Schematic of the 60 W Adapter R31 1000k R32 100k X2 C9 330nF L1 10 mH 2A C18 220nF IN X18 KBU4K − + D10 1N4148 C14 100u C21 68p R13 1k R14 220k C5 1n 220p C8 D4 1N4148 R17 100pF 100p C4 5 4 R29 1k 6 7 3 2 X2 NCP1380B 8 1 R18 1k NC C11 4.7u R4 18k NC R16 10 D7 1N4148 D1 1N4937 R12 10 R22 1200k R23 1500k C20 100n C17 R21 R19 1n NC NTC D6 1N967 R33 NC R25 NC 1.5n C1 Q1 BC857 D3 1N4148 C12 220u D5 1N4937 S11 R6 18k R3 47k R2 R24 0.47 0.47 M1 IPA60R385 T1 SFH6156−2 C3 100p C22 10n R15 NC GND X5 TL431G R9 1k D9 1n4148 C15 2.2nF Type = Y1 C5b 680 uF 35V C19 220p R34 1.2k D2 MBR20H150 C5a 680uF 35V TO−220 R28 47 D8 MRA4004 C10 47n R20 2.2k GND C7 100uF 35V L3 2.2u R8 10k R7 39k R5 27k GND Vout NCP1380EVB/D BOARD SCHEMATIC NCP1380EVB/D Figure 2. Photograph of the Top Side of the Board Figure 3. Photograph of the Bottom Side of the Board Efficiency The measurements were made after the board was operated during 10 mn at full load, low line, with an open frame and at ambient temperature. The input power was measured with the power meter WT210A from Yokogawa. The output current and the output voltage were measured using the digital multimeter 34401A from HP. Output Power Efficiency (%) Pout (W) Pout (%) Vin = 115 Vrms Vin = 230 Vrms 60.6 100 88.3 89.1 45.5 75 88.7 88.4 30.3 50 88.2 87.3 15.2 25 86.4 86.1 At Vin = 115 Vrms, the average efficiency is 87.9%. At Vin = 230 Vrms, the average efficiency is 87.7% which is above the 87% limit defined by the ENERGY STAR® norm EPA 2.0. http://onsemi.com 3 NCP1380EVB/D Efficiency at Light Output Load The efficiency at light load was first measured with the TL431 normally biased by a 1 kW resistor inserted in parallel of the optocoupler LED (Figure 4) R28 47 C19 220p . Vout L3 2.2u D2 MBR20H150 C5a 680uF 35V C5b 680uF 35V C7 100uF 25V GND GND R5 27k R9 1k R15 1k SFH6156−2 C10 47n X5 TL431_G R7 39k R8 10k GND Figure 4. TL431 Biased by a 1 kW Resistor The following results were obtained: Table 2. LIGHT LOAD EFFICIENCY WITH THE TL431 BIASED BY A 1 kW 115 Vrms 230 Vrms Pout (W) Pin (W) Efficiency (%) Pin (W) Efficiency (%) 1.0 1.312 76.1 1.364 73.2 0.7 0.945 73.9 0.993 70.4 0.5 0.701 71.6 0.750 66.9 The efficiency at light load is very good. Also, for an output power of 0.7 W the input power consumption is less than 1 W at low line and high line. In order to increase the efficiency at light load and to decrease the power consumption at no load, the TL431 bias is removed at light load using a special circuit patented by ON Semiconductor, shown in Figure 5. http://onsemi.com 4 NCP1380EVB/D D8 MRA4004 D9 1n4148 R34 1.2k C22 10n Vout L3 2.2u . D2 MBR20H150 C5a 680uF 35V . C5b 680uF 35V C7 100uF 25V C15 2.2nF Type = Y1 GND R9 1k R15 2.2k C10 47n X5 TL431_G GND R5 27k R7 39k R8 10k GND Figure 5. TL431 Bias Removal Circuit The results obtained with the TL431 bias removed are summarized inside Table 3. Table 3. LIGHT LOAD EFFICIENCY WITHOUT THE TL431 BIAS 115 Vrms 230 Vrms Pout (W) Pin (W) Efficiency (%) Pin (W) Efficiency (%) 1.0 1.290 77.6 1.340 74.6 0.7 0.923 75.9 0.965 72.2 0.5 0.678 73.8 0.720 69.6 By removing the TL431 bias at light load, we increase the efficiency at 0.5 W by 3% at 230 Vrms and by 2% at 115 Vrms. We also gain 1% efficiency at 1 W with the TL431 bias removed. Table 5. NO LOAD CONSUMPTION WITHOUT THE TL431 BIAS No Load Power Consumption The no load power consumption is the power drawn on the mains by the adaptor when no output load is connected to the board. Table 4 shows the power consumption with the TL431 biased by a 1 kW resistor. Table 5 shows the power consumption with the TL431 bias removed using the special circuit patented by ON Semiconductor. 230 Vrms Pout (W) Pin (mW) Pin (mW) 0 82 122 230 Vrms Pout (W) Pin (mW) Pin (mW) 0 64 98 By removing the TL431 bias, we managed to decrease the power consumption below 100 mW at no load. The power consumption is only 98 mW for a 230 Vrms input voltage. Thus, removing the TL431 bias has allowed saving 24 mW at high line. It is possible to decrease further the power consumption at no load by connecting the start−up resistor to the half−wave instead of the bulk rail as shown by Figure 6. For the same startup time, we only need to divide the value of the startup resistors from the schematic (R23 + R22 = 3.2 MW) by p. We obtain a half−wave startup resistor of 1.1 MW. The reference [1] shows in details how to calculate the half−wave startup resistor. Table 4. NO LOAD CONSUMPTION WITH THE TL431 BIAS 115 Vrms 115 Vrms http://onsemi.com 5 NCP1380EVB/D half−wave voltage mean value is 148 V instead of 103 V), the startup current is higher and charges the VCC capacitor faster than expected. For the sake of comparison, the half−wave resistor is increased to have a startup time equal to the startup time obtained with the startup resistor connected to the bulk rail. Finally, the half−wave startup resistor value is 1.3 MW. With the half wave startup resistor of 1.1 MW, we measure a startup time of 2.6 s instead of the 3 s startup duration that was obtained with the 3.2 MW resistor connected to the bulk rail. While observing the half−wave voltage, we noticed that there is a slight distortion of the waveform, leading to a higher mean value of the half−wave voltage. The half−wave mean value being higher than expected (at 230 Vrms, the Vbulk Rstartup 1.3Meg L C14 100u N D7 1N4148 VCC C11 4.7u D5 1N4937 C12 100u Laux Figure 6. The Startup Resistor is Connected to the Half−Wave Waveforms Table 6 highlights the no load consumption obtained with the startup resistor connected to the half−wave. The power consumption is decreased to 85 mW at high line! Valley Lockout Thanks to the valley lockout, the controller changes valley (from the 1st to the 4th valley) as the load decreases without any valley jumping. This allows extending the quasi−resonance operation range. The following scope shoots show the operating valley as the load decreases for an input voltage of 230 Vrms. Table 6. NO LOAD CONSUMPTION WITH THE STARTUP RESISTOR CONNECTED TO THE HALF−WAVE AND WITHOUT THE TL431 BIAS 115 Vrms 230 Vrms Pout (W) Pin (mW) Pin (mW) 0 59 85 http://onsemi.com 6 NCP1380EVB/D Figure 7. 1st Valley Operation at 60 W, 230 Vrms Figure 8. 2nd Valley Operation at 45 W, 230 Vrms Figure 9. 3rd Valley Operation at 30 W, 230 Vrms Figure 10. 4th Valley Operation at 24 W, 230 Vrms The following graph shows the switching frequency evolution as the output load varies. The pink curve portrays the switching frequency variation when the output load is decreased from 60 W to 0 W. The blue curve represents the switching frequency evolution when the output load is increased from 0 to 60 W. Figure 11. Switching Frequency Evolution versus Output Power at Vin = 115 Vrms http://onsemi.com 7 NCP1380EVB/D VCO Mode In the 60 W adapter, the switching frequency is around 31 kHz at Pout = 10 W and drops to 6 kHz for an output power of 1 W. At light output load, the controller will operate in VCO mode. In this mode, the peak current is fixed to 17.5% of its maximum values when VFB < 0.56 V. The switching frequency is variable and decreases as the output load decreases thus minimizing the switching losses. Figure 12. VCO Mode at 10 W, 230 Vrms Figure 13. VCO Mode at 1 W, 230 Vrms Startup The NCP1380 consume a very low current during startup (20 mA maximum). Thus, the power supply designer can choose startup resistors values in the range of MW and this allows decreasing the power consumption in standby. The following scope shoots show the startup time at the lowest input voltage for a 3.2 MW resistor connected to the bulk rail and for a 1.3 MW resistor connected to the half−wave. In each case, the startup time is around 3 s. Figure 14. Startup Duration with a 3.2 MW Resistor Connected to the Bulk Rail, Vin = 85 Vrms Figure 15. Startup Duration with a 1.3 MW Resistor Connected to the Half−Wave, Vin = 85 Vrms Output Load Step between 3.2 A and 0.1 A (100% to 3% of the maximum output power) with a slew rate of 1 A / ms and at a frequency of 20 Hz. In order to verify the stability of the adapter, a variable load is applied to its output. The output current varies http://onsemi.com 8 NCP1380EVB/D Figure 16. Transient Load Step Response at Vin = 115 Vrms Figure 17. Transient Load Step Response at Vin = 230 Vrms the NCP1380 allows saving space on the board and decreasing the bill of material cost. Very low standby power consumption can be obtained with the NCP1380. For an input voltage of 230 Vrms, we measured a power consumption of only 85 mW! The output voltage waveform (Figures 16 and 17) shows that the loop is stable and indicates a phase margin above 60°. Conclusion Due to the valley lockout, the NCP1380 allows building QR adapter without valley jumping. Building adapter with average efficiency greater than 87% is easily achievable with the NCP1380. The controller offers every protection needed to build safe power supply. Also, by combining functions on single pins, References 1. Stéphanie Conseil, “Designing a Quasi−Resonant Adaptor Driven by the NCP1380”, Application Note AND8431/D. Table 7. BILL OF MATERIAL Reference Qty Value Description Manufacturer Part Number C1 1 1.5n Ceramic Capacitor, Axial, 1000 V Standard Standard C3 1 100 pF Ceramic Capacitor, Axial, 1000 V Standard Standard C4 1 100 pF Ceramic capacitor, SMD, 50 V Standard Standard C5b,C5a 2 680 uF Electrolytic capacitor, 35 V RUBYCON 35ZL680M12.5X20 C5,C17,C22 3 1 nF Ceramic capacitor, SMD, 50 V Standard Standard C7 1 100 uF Electrolytic capacitor, 35 V Standard Standard C12 1 220 uF Electrolytic capacitor, 25 V Standard Standard C8,C19 2 220 pF Ceramic capacitor, SMD, 50 V Standard Standard C9 1 330 nF X2 capacitor, 305 V EPCOS B32922D3334M784 C10 1 47 nF Ceramic capacitor, SMD, 50 V Standard Standard C11 1 4.7u Electrolytic capacitor, 25 V Standard Standard C14 1 100 uF Electrolytic capacitor, 400 V NICHICON UCY2G101MHD C15 1 2.2 nF Y1 capacitor, 250 V CERAMITE 440LD22 C18 1 220 nF X2 capacitor, 305 V EPCOS B32922C3224M784 R17 1 100 pF Ceramic Capacitor, SMD, 50 V Standard Standard C20 1 100 nF Ceramic capacitor, SMD, 50 V Standard Standard C21 1 68 pF Ceramic capacitor, SMD, 50 V Standard Standard D1,D5 2 D1N4937 Fast Recovery Diode, Axial, 1 A, 600 V ON Semiconductor 1N4937G http://onsemi.com 9 NCP1380EVB/D Table 7. BILL OF MATERIAL Reference Qty Value Description Manufacturer Part Number D2 1 MBR20H150 Schottky Diode, TO−220, 20 A, 150 V ON Semiconductor MBRF20H150CTG D3,D7,D9 3 D1N4148 Diode, Axial, 100 V NXP 1N4148 D4, D10 2 D1N4148 Diode, SMD, 100 V VISHAY 1N4148W D6 1 Zener 18 V Zener Diode, Axial Standard Standard D8 1 MRA4004 Diode, SMD, 1 A, 400 V ON Semiconductor MRA4004T3G HS1 1 Heatsink, 14°C/W SEIFERT KL194/25.4SW HS2 1 Heatsink, 8.2°C/W SEIFERT KL196/25.4SW ISO1 1 Optocoupler SFH6156−2, SMD VISHAY SFH6156−2T J1 1 Input Connector, 2.5 A, 260 V MULTCOMP JR−201S(PCB) J2 1 Output Connector WEIDMULLER PM5.08/2/90 J3 1 Connector for external VCC WEIDMULLER PM5.08/2/91 L1 1 10 mH Common Mode Choke, 2*10 mH, 2 A WURTH 744823210 L3 1 2.2 uH Radial Coil, 2.2 uH, 6 A, 20% WURTH 744772022 M1 1 IPP60R385 MOSFET, 600 V, 7 A INFINEON IPP60R385CP Q1 1 BC857 PNP transistor, SMD ON Semiconductor BC857ALT1G R2,R24 2 0.47 W Ceramic Resistor, SMD, 1W, 1%, 50 V Standard Standard R3, R21 2 47 kW Ceramic Resistor, SMD, 0.25 W, 1%, 50 V Standard Standard R4,R6 2 18 kW Resistor, Axial, 3 W, 5% Standard Standard R5 1 27 kW Ceramic Resistor, SMD, 0.25W, 50 V Standard Standard R7 1 39 kW Ceramic Resistor, SMD, 0.25W, 50 V Standard Standard R8 1 10 kW Ceramic Resistor, SMD, 0.25W, 50 V Standard Standard R9,R13,R15, R29,R30, R31,R32 7 1 kW Ceramic Resistor, SMD, 0.25W, 50 V Standard Standard R12 1 10 W Resistor, Axial, 1 W, 1% Standard Standard R14 1 220 kW Ceramic Resistor, SMD, 0.25 W, 50 V Standard Standard R16 1 10 W Ceramic Resistor, SMD, 0.25 W, 50 V Standard Standard R18 1 1 kW Resistor, Axial, 0.25 W, 1% Standard Standard R19 1 NTC, 100 kW at 25°C, Beta = 4190 VISHAY NTCLE100E3104JB0 R20 1 2.2 kW Ceramic Resistor, SMD, 0.25 W, 50 V Standard Standard R22 1 1200 kW Resistor, Axial, 0.25 W, 1% Standard Standard R23 1 1500 kW Resistor, Axial, 0.25 W, 1% Standard Standard R25,R33 2 3000 kW Resistor, Axial, 0.25 W, 1% Standard Standard R28 1 47 W Ceramic Resistor, SMD, 0.25 W, 50 V Standard Standard R34 1 1.2 kW Ceramic Resistor, SMD, 0.25 W, 50 V Standard Standard U1 1 QR Transformer CME 17212 X2 1 NCP1380B QR controller ON Semiconductor NCP1380B X5 1 TL431 Shunt Regulator, 2.5 − 36 V, 1 − 100 mA ON Semiconductor TL431CLPG X18 1 KBU4K Diode Bridge, 4 A, 800 V MULTICOMP KBU4K SFH6156−2 http://onsemi.com 10 NCP1380EVB/D ENERGY STAR and the ENERGY STAR mark are registered U.S. marks. 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