ICE1QS01 Datasheet, PDF (8/21 Pages) Infineon Technologies AG – Controller for Switch Mode Power Supplies Supporting Low Power Standby and Power Factor Correction (PFC)

ICE1QS01
the current in the power transistor (Iprimary) is:
VPCS
=
1,
5V
+
L_----p_----r_--i_--m_-----a_----r_--y_-----×_-----I_--p_---r_---i_-m_------a_---r_---y_-
R2 × C2
Lprimary: Primary inductance of the transformer
The advantage of primary current simulation is the elimination of the leading edge spike, which is
generated when the power transistor is switched on.
RZI (zero crossing input and primary regulation)
Zero current counter
Every time when the falling voltage ramp of V_RZI crosses the 50 mV threshold a pulse is sent to the
zero-current-counter and increases the counter by one. If zero-current-counter and up-down-coun-
ter are equal the gate drive OUT is switched to high. Up-down counter is influenced via SRC voltage
as described below. If V_RZI is greater than 50 mV gate drive OUT is always switched low.
Figure: Zero Crossing Switching Behaviour
V
VSRC
VPCS
1.5V
VRZI
t
OUT
status up-down
counter = 0001:
switch on at first
zero crossing
Version 1.4
ton toff
8
status up-down
t
counter = 0010:
switch on at second
zero crossing
ton toff
t
27 Apr 2004