Forced Quasi Resonant ZVS flyback controller
Functional Description
vDrain(t)
NPri / NSec × vSec
VBulk
0
t
Free-wheeling phase
Oscillation phase
vAux(t)
NAux / NSec × vSec
0
t
NAux / NPri × VBulk
1 1 1 1
4 4 4 4
tOn
tf
tOsc
tOff
iMag(t)
t
VOLTAGE_SENSING_SIGNALS
Figure 13 Auxiliary voltage and magnetization current waveforms for standard discontinuous
conduction mode operation
4.2.1.1
Output voltage sensing via ZCD pin
Output voltage is sensed at a fixed point of time during the free-wheeling phase. The free-wheeling phase begins when the
gate driver is switched off and ends when the secondary side demagnetization current becomes zero. During free-wheeling
phase the VCC capacitor of the IC, the output stage and the additional ZVS capacitor at ZVS winding for introducing a forced
resonant cycle (see Chapter 4.2.12) are supplied. As soon as VCC capacitor is charged, the auxiliary voltage is a function of
secondary side voltage.
푵
푨푼푿
푽푨푼푿
=
∙ 푽푺풆풄
( 1 )
푵
푺풆풄
Figure 14 shows the schematic related to secondary side voltage sensing and the equivalent network.
Data Sheet
15
Revision 2.0
2020-08-20
INFINEON [ Infineon ]
