tea1532ct-n1 NXP Semiconductors, tea1532ct-n1 Datasheet - Page 7

• Manufacturer Part Number: tea1532ct-n1
• Description: Greenchip Ii Smps Control Ic
• Manufacturer: NXP Semiconductors

NXP Semiconductors
TEA1532BT_TEA1532CT_1
Product data sheet
7.6 OverCurrent Protection (OCP)
7.7 Demagnetization (QR operation)
7.8 Valley switching
The primary peak current in the transformer is measured accurately cycle-by-cycle using
the external sense resistor R
internal level equal to 1.5 V
suppressed during the leading edge blanking period, t
caused by the switch-on spikes.
The system will be in Discontinuous Conduction Mode (DCM) (QR operation) when
resistor R
secondary stroke has ended.
Demagnetization features a cycle-by-cycle output short-circuit protection, which
immediately reduces the frequency (longer off-time), thereby reducing the power level.
Demagnetization recognition is suppressed during the first t
1.5 s). This suppression may be necessary in applications where the transformer has a
large leakage inductance and at low output voltages or start-up.
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.
Fig 5. The V
p
Figure
DEM
is the primary self inductance of the transformer and C
is applied. The oscillator will not start a new primary stroke until the previous
sense(max)
6. A new cycle starts when the power switch is activated. After the on-time
Rev. 01 — 18 January 2007
voltage as a function of V
V
sense(max)
Figure 6
25 mV
0.52 V
sense
V
CTRL
(V)
. The OCP circuit limits the voltage on pin SENSE to an
shows the drain voltage, valley signal, secondary stroke
(typ)
(see also
TEA1532BT; TEA1532CT
1 V
----------------------------------------- -
2
Section
CTRL
1.5 V
1
(typ)
leb
L
7.5). The OCP detection is
p
, to prevent false triggering
cycle
skip
active
GreenChip II SMPS control IC
coa016
V
C
CTRL
sup(xfmr_ring)
d
(V)
d
is the capacitance on
© NXP B.V. 2007. All rights reserved.
time (typical
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