TEA1532P NXP Semiconductors, TEA1532P Datasheet - Page 10

• Manufacturer Part Number: TEA1532P
• Description: Greenchip Tm Ii Smps Control Ic
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9397 750 14319
Product 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
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 demagnetization 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
demagnetization 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
Rev. 02 — 4 February 2005
i
, long on-times at low V
mains
primary
stroke
TEA1532(A)P; TEA1532(A)T
secondary
stroke
CC
i
level at which the converter has to enter a
i
drops below V
can damage the (external) power device.
secondary
ringing
GreenChip II SMPS control IC
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
UVLO
(2)
. Capacitor C
i
is high enough (V
mgu235
(1)
VCC
i
is low.
will
10 of 27
m
,