TEA1532 Philips Semiconductors, TEA1532 Datasheet - Page 9

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

Philips Semiconductors
9397 750 13113
Preliminary data sheet
7.13 Valley switching
A voltage higher than 3 V on pin PROTECT will always latch the IC. This is independent of
the state of the IC.
Refer to
(determined by the sense voltage and the internal control voltage), the switch is opened
and the secondary stroke starts. After the secondary stroke, the drain voltage shows an
oscillation with a frequency of approximately
where L
the drain node.
As soon as the oscillator voltage is high again and the secondary stroke has ended, the
circuit waits for the lowest drain voltage before starting a new primary stroke. This method
is called valley detection.
signal and the oscillator signal.
In an optimum design, the reflected secondary voltage on the primary side will force the
drain voltage to zero. Thus, zero voltage switching is possible, preventing large capacitive
switching losses
results in small and cost effective magnetics.
•
•
When the voltage on pin CTRL is below 0.63 V, the IC is assumed to be out of
regulation (e.g. the control loop is open). In this case activating pin PROTECT
(V
V
repeated until the fault condition is removed (safe restart mode)
When the voltage on pin CTRL is above 0.63 V, the IC is assumed to be in regulation.
In this case activating pin PROTECT (V
the IC: The voltage on pin V
start switching again until the latch function is reset. The latch is reset as soon as V
drops below 4.5 V (typical value). The internal overtemperature protection will also
trigger this latch; see also
UVLO
PROTECT
p
Figure
is the primary self inductance of the transformer and C
, capacitor C
> 2.5 V) will cause the converter to stop switching. Once V
8. A new cycle starts when the power switch is activated. After the on-time
P
=
1
-- -
2
VCC
Rev. 01 — 28 May 2004
Figure 8
C
will be recharged and the supply will restart. This cycle will be
V
Figure
2
CC
shows the drain voltage, valley signal, secondary stroke
will cycle between V
f
1.
, and allowing high frequency operation, which
PROTECT
-------------------------------------------------
2
> 2.5 V), by external means, will latch
1
start
L
GreenChip II SMPS control IC
p
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
and V
C
d
d
UVLO
is the capacitance on
, but the IC will not
TEA1532
CC
drops below
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CC