tea1501t-n1 NXP Semiconductors, tea1501t-n1 Datasheet - Page 4

• Manufacturer Part Number: tea1501t-n1
• Description: Greeny; Greenchip
• Manufacturer: NXP Semiconductors

Philips Semiconductors
TEA1501_2
Product data sheet
7.1.1 On/off
7.1.2 Start-up
7.1.3 Operation
7.1 System operation
The system of the TEA1501 can be switched on and off by means of a low cost, low
voltage switch. In the Off mode the start-up current source and power switch are disabled.
In the On mode, the TEA1501 delivers the start-up current for the supply capacitor and
after the supply voltage reaches the start-up level, the TEA1501 activates the power
switch.
The start-up is realized with a high voltage start-up current source instead of a dissipative
bleeder resistor which is commonly used by low voltage control ICs. When the TEA1501 is
switched on, the start-up current source is enabled and starts charging the AUX capacitor.
The start-up current level is high and accurate (typical 1.8 mA) which results in a
well-defined and short start-up time, within 0.25 s. After the supply voltage reaches the
start-up level the current source is switched off and the AUX capacitor supplies the chip.
Reducing the power dissipation in the current source to zero after start-up is one of the
green features of the TEA1501.
After start-up the flyback converter starts delivering energy to the secondary and auxiliary
winding. The system of the TEA1501 works with fixed switching frequency and fixed peak
current.
As all the windings of the flyback transformer have the same flux variation, the secondary
voltage and the auxiliary voltage are related via the turns-ratio (n
isolated secondary voltage is controlled by the non-isolated auxiliary voltage.
Fig 3. Basic flyback configuration
(1) The secondary earthing point is isolated from the primary earthing points.
R SOURCE
C BURST
Rev. 02 — 31 March 2006
SOURCE
BURST
OOD
REF
R REF
TEA1501
on/off
DRAIN
n.c.
GND
AUX
V in
V zener
n p
n a
GreenChip SMPS controller IC
© Koninklijke Philips Electronics N.V. 2006. All rights reserved.
n s
s
: n
(1)
a
). Therefore, the
TEA1501
mgm823
V out
load
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