Dual Switch Flyback Solution Solution for High Efficiency & Low Standby Power to meet 2013 EuP Computing Product Line Power Conversion Taiwan Fairchild Semiconductor

Dual Switch QR Solution Enabled by FAN6920 : CRM PFC + QR Controller Combo IC FAN7382 : HVIC FAN6204 : Syn. Rectifier IC

Basic Operation of Dual Switch Flyback Phase 1: Q1&Q2 On Phase 3&4: Q1&Q2 off, D1&D2 off Phase 2: Q1&Q2 Off, D1, D2 on

Benefit of Dual Switch Flyback (1) Snubber and Leakage Inductance Loss Improved No snubber loss and heat problem Leakage inductance is recycled into bulk capacitor Single Flyback iDS iLK Up to 70% of leakage inductance can be recycled Dual Flyback

Benefit of Dual Switch Flyback (2) Low MOSFET Vds and Near ZVS switching Low MOSFET Drain Source Voltage  Good reliability Allow large n design  Near ZVS Switching  Low switching loss Vds = Vin + n*Vo + Spike Vds= Vin/2 Spike is clamped by two recycle diodes, stress shared by two MOS Vds of Single Flyback Larger switching loss Vds of Dual Flyback Near ZVS Switching

Benefit of Dual Switch Flyback (3) Low VDS of SR MOS for secondary conduction loss Benefit of high turn ration n to SR MOSFET VDS of SR MOS is : Vin/n + Vout Large n  Lower VDS  Lower MOS Ron in lower price  cost & efficiency Example: Vin = 420V, Vo = 12V, n= 12  VDS = 420V/12 + 12V = 47V Could choose 60V or 75V SR MOSFET

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 > 180V  M1 off  PFC Vo = 2.5V x (R1+R2)/R2 When AC < 150V  M1 on  R2//R3  PFC Vo= 2.5V x (R1+R2//R3))/(R2//R3) M1 FAN6920 Block Diagram

Benefit of Dual Switch Flyback (5) Deep extended valley switch for light load efficiency Deep extended valley switch ( up to 12th valley) to allow low 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 4th valley) 5th valley detect First valley detect 12th valley detect FAN6920 Deep extended valley switch

Benefit of Dual Switch Flyback (6) Power Saving Dual Switch Flyback Could Meet < 0.5W @ 0.25W ( 2013 EuP) 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= 0.25W 115V 0.186W 0.482W 230V 0.195W 0.486W

Target Application For Power Range from 75W ~200W All in One PC Power LED TV Notebook Adapter Game Console LED Lighting

Dual-switch Flyback Schematic

Solution Comparison Dual Switch QR Flyback LLC Note Efficiency D2D stage : Nearly ZVS switching D2D stage: ZVS switching PFC stage: Better low line efficiency by two level PFC output 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 Low efficiency due to high frequency. FAN6920 could do up to 12th valley detection for slow frequency Dynamic Good line transient response Poor line transient response Inherent characteristic of topology Good load transient response Poor load transient response Power Saving <0.3W, <0.5W, LLC couldn’t allow PFC turn off at light load. Design Easiness Easy Difficult Resonant L & C control to prevent ZVS fail Manufacture Easiness

Key Parts Comparison MOSFET 3 (PFC and dual switch) 3 (PFC and LLC) Transformer 1 for PFC 1 for D2D 1 for resonant L & C IC FAN6920MR+FAN7382 (HVIC) CRM PFC+ LLC controller SR FAN6204 2 SR controller 1 2 MOSFETs Cost -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 Power Range 75W~200W 100W~500W

Dual Switch Flyback vs. LLC Efficiency: test board 90W/19V No load

Slim Type 19V/ 90W Dual Switch Flyback Efficiency Test Result Efficiency (18 AWG 1.2m wire include): No Load Power Consumption: 22.5W 45W 67.5W 90W 115VAC 89.48% 90.54% 90.40% 89.61% 230VAC 91.24% 90.04% 90.86% 90.88% Input Power @ 0.25W VAC (RMS) PIN(W) 115 0.482 230 0.486 60mm 95mm 16.5mm

19V/180W Dual Flyback FAN6204 + FDP032N08

130W/19V AIO power 100mm 145mm Efficiency 20% 26W 50% 65W 100% 130W AIO 130W Input Power @ no load VAC (RMS) PIN(W) 90 0.19 115 0.186 230 0.195 264 0.21 Efficiency 20% 26W 50% 65W 100% 130W 3 point AVG. 115Vac/60Hz 89.29% 92.15% 92.32% 91.25% 230Vac /50Hz 91.65% 93.59% 92.56% Input Power @ 0.25W VAC (RMS) PIN(W) 115 0.478 230 0.482 Spec: PIN<0.5W 2013 EUP

200W/19V AIO Power Efficiency 20% 40W 50% 100W 100% 200W 3 point AVG. Output Power @ no load Output Power @ 0.25W VAC (RMS) PIN(W) 90 0.168 115 0.183 230 0.206 264 0.223 VAC (RMS) PIN(W) 115 0.484 230 0.487 Efficiency 20% 40W 50% 100W 100% 200W 3 point AVG. 115Vac/60Hz 90.01% 91.62% 90.76% 90.79% 230Vac /50Hz 92.16% 91.76% 92.60% 92.17% Output Power @ 0.5W VAC (RMS) PIN(W) 115 0.762 230 0.781

Example Circuit (19V/90W)

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