11 flyback

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Unformatted text preview: Flyback Converter Chern-Lin Chen (陳 秋 麟) Department of Electrical Engineering & Graduate Institute of Electronics Engineering National Taiwan University e-mail - clchen@cc.ee.ntu.edu.tw office tel – +886-2-3366-3575 Apr. 27, 2010 Application - PC ATX Power ~ bridge rectifier Boost PFC LLC resonant Flyback standby 1 National Taiwan University 國立台灣大學 Power ICS Laboratory 功率積體電路與系統實驗室 Chern-Lin Chen 陳秋麟 Application – Low-Cost Charger/Adaptor ~ ~ National Taiwan University 國立台灣大學 bridge rectifier Flyback charger bridge rectifier 2 Flyback adaptor Power ICS Laboratory 功率積體電路與系統實驗室 Chern-Lin Chen 陳秋麟 Complete Flyback System 3 National Taiwan University 國立台灣大學 Power ICS Laboratory 功率積體電路與系統實驗室 Chern-Lin Chen 陳秋麟 Pin Count 1. VDD 2. GND 3. Output 4. Feedback 5. Isense 6. (Frequency) 1 4 2 3 5 4 National Taiwan University 國立台灣大學 Power ICS Laboratory 功率積體電路與系統實驗室 Chern-Lin Chen 陳秋麟 Flyback Basics 5 National Taiwan University 國立台灣大學 Power ICS Laboratory 功率積體電路與系統實驗室 Chern-Lin Chen 陳秋麟 Coupled Inductors VDD UVLO RI OSC Green Mode GND FB SQ R OCP Gate Driver OUT LEB SENSE Primary + Secondary + Auxiliary windings 6 National Taiwan University 國立台灣大學 Power ICS Laboratory 功率積體電路與系統實驗室 Chern-Lin Chen 陳秋麟 Equivalent Model DO ipri LP Vd Cin n:1 isec CO R VO Q1 NP n= = NS 7 National Taiwan University 國立台灣大學 LP LS Power ICS Laboratory 功率積體電路與系統實驗室 Chern-Lin Chen 陳秋麟 Switch On ip VDC is vO di p VDC = dt Lp (i p current slope) i p , peak VDC = ton + i p ,ini (i p peak value) Lp 12 Lp i p , peak (energy stored in Lp ) 2 8 National Taiwan University 國立台灣大學 Power ICS Laboratory 功率積體電路與系統實驗室 Chern-Lin Chen 陳秋麟 Switch Off ip VDC is vO i p charges Cds vd grows to VDC + Np (VO + VF ) Ns diode conducts, i p stops, is appears 12 12 Ls is , peak = L p i p , peak (energy conservation) 2 2 dis V + VF (is drops from is , peak ) =− O dt Ls 9 National Taiwan University 國立台灣大學 Power ICS Laboratory 功率積體電路與系統實驗室 Chern-Lin Chen 陳秋麟 Reflection Voltage VDiode = Vo + Vdc*Ns/Np VMOS = Vdc + (Vo+VF)*Np/Ns 10 National Taiwan University 國立台灣大學 Power ICS Laboratory 功率積體電路與系統實驗...
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