TEA1532 Ver la hoja de datos (PDF) - Philips Electronics
Número de pieza
componentes Descripción
Fabricante
TEA1532 Datasheet PDF : 27 Pages
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Philips Semiconductors
primary
stroke
secondary
stroke
drain
TEA1532
GreenChip™II SMPS control IC
secondary
ringing
valley
secondary
stroke
oscillator
(2)
(1)
(1) Start of new cycle at lowest drain voltage.
(2) Start of new cycle in a classical PWM system at high drain voltage.
Fig 8. Signals for valley switching.
mgu235
7.14 Brown-out protection
During the so called brown-out test, the input voltage is slowly decreased. Since the
on-time depends on Vi, overlong on-times at low Vi can damage the (external) power
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 µs. The maximum on-time will be reached while Vi is low.
Subsequently, the IC stops switching and VCC drops below VUVLO. Capacitor CVCC will
only be recharged and the supply will restart only when voltage Vi is high enough (Vm,
also see Section 7.1). In addition to this, a Vi level at which the converter has to enter a
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:
I(DEM) ≈ -R--V--D--a-E-u--x-M-- ≈ -N------×R---D-V---E--m-M--a---i-n---s
Where: N = -N----a---u---x
Np
9397 750 13113
Preliminary data sheet
The latter function requires an on-time of at least 2 µs. This on-time ensures that a reliable
demag current can be measured.
Rev. 01 — 28 May 2004
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
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