反激设计大功率LED恒流源.pdf

MODEL : 60-120V OUT PUT CONSTANT CURRENT POWER SUPPLY REV :01 Write by: Wink Fang Date: 2007 10 30 Toplogy: FLYBACK DCM 1. Abstract This is design for constant current converter use for LED driver input : DC 20-28V out put voltage: DC 60-120v out put current: 340mA 1. Abstract 2. Symbol and units define 3. Design varibles define 3.1 Input variables Vin_min : 20V Vin_nom : 24V Vin_max : 28V 3.2 Output variables Vo_max : 120V Vo_min : 60V Vdrop : 0.7V Vo_ripple : 300mV Lp_fixed : 10μH Lp : Lp_t if Lp_fixed = 0 Lp_fixed otherwise − 5 Lp 1 × 10 H DutyTransformer Current IN criticaloperation : Icr*Vo=Lp*Ipeak^2*Fsw*h/2, Ippeak=Vin*Dcr/(Lp*Fsw) 2 ⎡ (Vo + Vdrop) ⋅Nps ⎤ ⎢Vin ⋅ ⎥ ⋅η_set ⎣ Vin + (Vo + Vdrop) ⋅Nps⎦ Icr(Vin , Vo) : Lp ⋅Fsw⋅Vo⋅2 2 Pin(Vo , Io) ⋅Lp ⋅Fsw Lp ⋅Fsw Dmod(Vin , Vo , Io) : if Io ≤ Icr(Vin , Vo) Vin (Vo + Vdrop) ⋅Nps otherwise Vin + (Vo + Vdrop) ⋅Nps Ton(Vin , Vo , Io) : Dmod(Vin , Vo , Io)⋅TPsw Vin ⋅Ton(Vin , Vo , Io) Toff (Vin , Vo , Io) : (Vo + Vdrop) ⋅Nps Tdead(Vin , Vo , Io) : TPsw − Ton(Vin , Vo , Io) − Toff (Vin , Vo , Io) Vin ΔIP(Vin , Vo , Io) : ⋅Ton(Vin , Vo , Io) Lp ⎡ Pin(Vo , Io) ⎛ Vin ⋅Ton(Vin , Vo ,