Dual Switch Flyback Solution for High Efficiency Low
Dual Switch Flyback Solution for High Efficiency & Low Standby Power to meet 2013 Eu. P Computing Product Line Power Conversion Taiwan Fairchild Semiconductor www. fairchildsemi. com
Dual Switch QR Solution Enabled by n FAN 6920 : CRM PFC + QR Controller Combo IC n FAN 7382 : HVIC n FAN 6204 : Syn. Rectifier IC 2 www. fairchildsemi. com
Basic Operation of Dual Switch Flyback Phase 1: Q 1&Q 2 On Phase 3&4: Q 1&Q 2 off, D 1&D 2 off Phase 2: Q 1&Q 2 Off, D 1, D 2 on 3 www. fairchildsemi. com
Benefit of Dual Switch Flyback (1) Snubber and Leakage Inductance Loss Improved No snubber loss and heat problem n Leakage inductance is recycled into bulk capacitor n Single Flyback i. DS i. LK Up to 70% of leakage inductance can be recycled Dual Flyback 4 www. fairchildsemi. com
Benefit of Dual Switch Flyback (2) Low MOSFET Vds and Near ZVS switching n Low MOSFET Drain Source Voltage Good reliability n Allow large n design Near ZVS Switching Low switching loss Vds = Vin + n*Vo + Spike Vds of Single Flyback Vds= Vin/2 Spike is clamped by two recycle diodes, stress shared by two MOS Larger switching loss 5 Vds of Dual Flyback Near ZVS Switching www. fairchildsemi. com
Benefit of Dual Switch Flyback (3) Low VDS of SR MOS for secondary conduction loss Benefit of high turn ration n to SR MOSFET n VDS of SR MOS is : Vin/n + Vout n Large n Lower VDS Lower MOS Ron in lower price cost & efficiency Example: Vin = 420 V, Vo = 12 V, n= 12 VDS = 420 V/12 + 12 V = 47 V Could choose 60 V or 75 V SR MOSFET 6 www. fairchildsemi. com
Benefit of Dual Switch Flyback (4) Built in two level PFC output for low line efficiency • Two Level PFC output to improve low line efficiency When AC > 180 V M 1 off PFC Vo = 2. 5 V x (R 1+R 2)/R 2 When AC < 150 V M 1 on R 2//R 3 PFC Vo= 2. 5 V x (R 1+R 2//R 3))/(R 2//R 3) M 1 FAN 6920 Block Diagram 7 www. fairchildsemi. com
Benefit of Dual Switch Flyback (5) Deep extended valley switch for light load efficiency • Deep extended valley switch ( up to 12 th valley) to allow operating frequency in light load Improved light load efficiency Load ↓ Freq↑ Poor light load efficiency Freq. nearly constant QR Operation without extended valley switch Other IC: QR Operation with extended valley ( up to 4 th valley) 5 th valley detect First valley detect 12 th valley detect FAN 6920 Deep extended valley switch 8 www. fairchildsemi. com
Benefit of Dual Switch Flyback (6) Power Saving • Dual Switch Flyback Could Meet < 0. 5 W @ 0. 25 W ( 2013 Eu. P) • PFC Stage: • High line/light load Turn off PFC • Low line/light load burst mode • QR Stage: • enter into burst mode when light load • No snubber loss • SR Stage: • Turn off SR when light load Power Saving Load VAC Po = 0 W Po= 0. 25 W 115 V 0. 186 W 0. 482 W 230 V 0. 195 W 0. 486 W 9 www. fairchildsemi. com
Target Application • For Power Range from 75 W ~200 W • All in One PC Power • LED TV • Notebook Adapter • Game Console • LED Lighting 10 www. fairchildsemi. com
Dual-switch Flyback Schematic 11 www. fairchildsemi. com
Solution Comparison Dual Switch QR Flyback LLC D 2 D stage : Nearly ZVS switching D 2 D stage: ZVS switching PFC stage: Better low line efficiency by two level PFC output PFC stage: Poor low line efficiency due to high PFC output LLC could allow only narrow input voltage range Light load (~20%) : Higher efficiency due to slow freq. to reduce switching loss Light load (~20%) : Low efficiency due to high frequency. FAN 6920 could do up to 12 th valley detection for slow frequency Good line transient response Poor line transient response Inherent characteristic of topology Good load transient response Poor load transient response Inherent characteristic of topology Power Saving <0. 3 W, <0. 5 W, LLC couldn’t allow PFC turn off at light load. Design Easiness Easy Difficult Resonant L & C control to prevent ZVS fail Manufacture Easiness Easy Difficult Resonant L & C control to prevent ZVS fail Efficiency Dynamic 12 Note www. fairchildsemi. com
Key Parts Comparison MOSFET 3 (PFC and dual switch) 3 (PFC and LLC) Transformer 1 for PFC 1 for D 2 D 1 for resonant L & C FAN 6920 MR+FAN 7382 (HVIC) CRM PFC+ LLC controller IC FAN 6204 2 SR controller MOSFET 1 2 MOSFETs -Lower transformer cost -Lower MOSFET cost -One SR MOSFET needed -Higher transformer cost -Might need additional resonant T’mer -Two SR MOSFET needed -Might need additional std by stage for power saving 75 W~200 W 100 W~500 W IC SR Cost Power Range 13 www. fairchildsemi. com
Dual Switch Flyback vs. LLC Efficiency: test board 90 W/19 V No load 14 www. fairchildsemi. com
Slim Type 19 V/ 90 W Dual Switch Flyback Efficiency Test Result Efficiency (18 AWG 1. 2 m wire include): 22. 5 W 45 W 67. 5 W 90 W 115 VAC 89. 48% 90. 54% 90. 40% 89. 61% 230 VAC 91. 24% 90. 04% 90. 86% 90. 88% No Load Power Consumption: Input Power @ 0. 25 W VAC (RMS) PIN(W) 115 0. 482 230 0. 486 60 mm 15 16. 5 mm 95 mm www. fairchildsemi. com
19 V/180 W Dual Flyback FAN 6204 + FDP 032 N 08 16 www. fairchildsemi. com
130 W/19 V AIO power AIO 130 W 100 mm 145 mm Input Power @ no load VAC (RMS) PIN(W) 90 0. 19 115 0. 186 230 0. 195 264 0. 21 VAC (RMS) PIN(W) 115 0. 478 230 0. 482 Input Power @ 0. 25 W Efficiency 20% 26 W 50% 65 W 100% 130 W 3 point AVG. 115 Vac/60 Hz 89. 29% 92. 15% 92. 32% 91. 25% 230 Vac /50 Hz 91. 65% 92. 15% 93. 59% 92. 56% Spec: PIN<0. 5 W 2013 EUP 17 www. fairchildsemi. com
200 W/19 V AIO Power Output Power @ no load VAC (RMS) PIN(W) 90 0. 168 115 0. 183 230 0. 206 264 0. 223 Output Power @ 0. 25 W VAC (RMS) PIN(W) 115 0. 484 230 0. 487 Efficiency 20% 40 W 50% 100 W 100% 200 W 3 point AVG. 115 Vac/60 Hz 90. 01% 91. 62% 90. 76% 90. 79% 230 Vac /50 Hz 92. 16% 91. 76% 92. 60% 92. 17% Output Power @ 0. 5 W VAC (RMS) PIN(W) 115 0. 762 230 0. 781 18 www. fairchildsemi. com
Example Circuit (19 V/90 W) 19 www. fairchildsemi. com
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