12-Soft Start - Soft Start Chern-Lin Chen (陳 秋 麟)...

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Unformatted text preview: Soft Start 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 May 11, 2010 Hard Start-Up ipri isec ipri isec t ON VO → 0 OFF maximum ON time i pri , peak VDC = tON L1 disec VO + VF = dt L2 1 slow discharge 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 Hard Start-Up Cycles iP iS OCP Limit or maximum duty minimum ON time iP di p dt = vdc Lp iS dis vO + vF = dt Ls Vo slowly grows. Inevitable CCM Primary/secondary current peaks grow 2 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 Magnetic Concerns vI n1 n2 vO Faraday ' s law V p = N p Ae BON VDC DmaxT = ×108 n1 Ae B × 10−8 T BOFF = − B (VF + VO )(1 − Dmax ) T ×108 n2 Ae during start - up vO grows from 0 H ( 3 BON >| BOFF | BON =| BOFF | at steady state ) 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 Ideal Start-Up B H let D gradually grow keep starting point at origin 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 Implementation RI OSC S R Q Gate Driver OUTPUT OCP VDD UVLO LEB SENSE GND Green Mode FB digital divider 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 Usual Phenomenon n:1 vds = vDC + n(vO + vF ) + spike start spike n(vO+vF) soft start (+ OCP) CCM ipri peak Lleak,pri stored energy vds vDC voltage feedback 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 Short SS Period soft start OCP VDC 120Hz ripple OCP voltage feedback 7 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 ...
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This note was uploaded on 10/16/2010 for the course GRADUATE I Power IC taught by Professor Chern-linchen during the Fall '09 term at National Taiwan University.

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