TEA1533AT Philips Semiconductors, TEA1533AT Datasheet - Page 9

• Manufacturer Part Number: TEA1533AT
• Description: GreenChipTMII SMPS control IC
• Manufacturer: Philips Semiconductors

Philips Semiconductors
OverCurrent Protection (OCP)
The cycle-by-cycle peak drain current limit circuit uses the
external source resistor to measure the current accurately.
This allows optimum size determination of the transformer
core (cost issue). The circuit is activated after the leading
edge blanking time, t
voltage to an internal level.
OverPower Protection (OPP)
During the primary stroke, the rectified mains input voltage
is measured by sensing the current drawn from pin DEM.
This current is dependent on the mains voltage, according
to the following formula:
2002 Aug 23
handbook, full pagewidth
GreenChip
A: Start of new cycle at lowest drain voltage.
B: Start of new cycle in a classical PWM system at high drain voltage.
TM
leb
II SMPS control IC
. The OCP circuit limits the ‘sense’
secondary
I
DEM
oscillator
stroke
valley
drain
-------------- -
R
V
DEM
aux
primary
stroke
N V
--------------------------
Fig.8 Signals for valley switching.
R
DEM
mains
secondary
stroke
9
where:
The current information is used to adjust the peak drain
current, which is measured via pin I
compensation is such that an almost mains independent
maximum output power can be realized.
The OPP curve is given in Fig.9.
secondary
N
ringing
=
N
----------- -
N
aux
p
B
TEA1533T; TEA1533AT
MGU235
A
sense
Product specification
. The internal