18

 2005 Semtech Corp.

www.semtech.com

SC4901

POWER MANAGEMENT

OUT P UT

QF

DF

C

••

T

DR

QS

DS

QR

L

SIN GLE EN DED

FOR W A R D

CON V ER TOR

PR IM A R Y

GATE F

GAT E R

Vre c

Vse c

Ind C urre nt

Se c C urre nt

Vse c

GA TE F

Vre c

Ind ucto r C urre nt

Tra nsf o rm e r Se co nd a ry C urre n t

Transf o rm e r Se c V o ltage

Ga te Driv e f o r

F o rw a rd M OSF E TS QS, QF

RECTIF IED SECON DARY V OL TAGE

W ITH POST REGU L ATION

Ga te Driv e F o r QR

GA TE R

T3

T2

T1

T0

Pulse W idth M o dula te d by

Se c o nd a ry Sid e C o ntro lle r

-V E

+V E

T2 : QS , QF are t urne d OF F .

This e dge is Pulse Widt h M odulat e d t o po st - re gulat e t he out put .

T1 : F o rward MOS F ETs QS and QF are swit ched ON

T1 - T0 : F o rward de lay t o pre ve nt short ing the se co ndary winding

T3 - T2 : Turn OF F delay t o prev ent sho ot thro ugh

T3 : QR is t urne d ON

T0 : Transfo rme r se co ndary volt age go es +ve , QR is t urne d OF F at t his instant .

Application Information (Cont.)

FIg 11) Theoretical waveforms of Combi Sync topology