TEA1532 Philips Semiconductors, TEA1532 Datasheet - Page 10

• Manufacturer Part Number: TEA1532
• Description: GreenChip SMPS control IC
• Manufacturer: Philips Semiconductors

Philips Semiconductors
9397 750 13113
Preliminary data sheet
7.14 Brown-out protection
During the so called brown-out test, the input voltage is slowly decreased. Since the
on-time depends on V
device. This is prevented by stopping the converter when the input voltage drops too low.
When the voltage on pin DEM drops below 50 mV during the on-time (QR mode), the
maximum on-time is set to 25 s. The maximum on-time will be reached while V
Subsequently, the IC stops switching and V
only be recharged and the supply will restart only when voltage V
also see
safe restart can be set with a demag resistor. During the primary stroke, the rectified
mains input voltage is measured by sensing the current drawn from pin DEM. This current
depends on the mains voltage, according to the following formula:
Where:
The latter function requires an on-time of at least 2 s. This on-time ensures that a reliable
demag current can be measured.
I
Fig 8. Signals for valley switching.
DEM
(1) Start of new cycle at lowest drain voltage.
(2) Start of new cycle in a classical PWM system at high drain voltage.
N
Section
-------------- -
R
V
DEM
=
aux
----------- -
N
secondary
N
oscillator
aux
p
stroke
valley
7.1). In addition to this, a V
N
------------------------- -
drain
R
DEM
V
i
, overlong on-times at low V
mains
Rev. 01 — 28 May 2004
primary
stroke
secondary
stroke
CC
i
level at which the converter has to enter a
drops below V
i
can damage the (external) power
secondary
ringing
GreenChip II SMPS control IC
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
UVLO
(2)
. Capacitor C
i
is high enough (V
TEA1532
mgu235
(1)
VCC
i
is low.
will
10 of 27
m
,