TEA2260 ST Microelectronics, Inc., TEA2260 Datasheet - Page 6

• Manufacturer Part Number: TEA2260
• Description: Switch Mode Power Supply Controller
• Manufacturer: ST Microelectronics, Inc.

TEA2261/0
GENERAL DESCRIPTION
The TEA2260/61 is an off-line switch mode power
supply controller. The synchronization function
and the specific operation in stand-by mode make
it well adapted to video applications such as TV
sets, VCRs, monitors, etc..
The TEA2260/61 can be used in two types of ar-
chitectures:
– Master/Slave architecture. In this case, the
– Conventional architecture with linear feedback
Using the TEA2260/61, the stand-by auxiliary
power supply, often realized with a small but costly
50Hz transformer, is no longer necessary. The
burst mode operation of the TEA2260/61 makes
possible the control of very low output power
(down to less than 1W) with the main power trans-
former.
When used in a master/slave architecture, the
TEA2260/61 and also the power transistor turn-off
can be easily synchronized with the line transform-
er. The switching noise cannot disturb the picture
in this case.
As an S.M.P.S. controller, the TEA2260/61 fea-
tures the following functions:
– Power supply start-up (with soft-start)
– PWM generator
– Direct power transistor drive (+1.2A, -2.0A)
– Safety functions: pulse by pulse current limita-
S.M.P.S. OPERATING DESCRIPTION
Starting Mode - Stand By Mode
Power for circuit supply is taken from the mains
through a high value resistor before starting. As
long as V
the quiescent current is very low (typically 0.7mA)
and the electrolytic capacitor across V
charged. When V
10.3V), the circuit starts, generating output pulses
with a soft-starting. Then the SMPS goes into the
stand-by mode and the output voltage is a per-
centage of the nominal output voltage (e.g. 80%).
To do this, the TEA2260/61 contains all the func-
tions required for primary mode regulation: a fixed
frequency oscillator, a voltage reference, an error
amplifier and a pulse width modulator (PWM).
6/11
1
TEA2260/61 drives the power transistor accord-
ing to the pulse width modulated signals generat-
ed by the secondary located master circuit. A
pulse transformer provides the feedback (see
Figure 1).
signal (feedback sources: optocoupler or trans-
former winding) (see Figure 2).
tion, output power limitation, over and under volt-
age lock-out.
CC
of the TEA2260/61 is below V
CC
reaches V
CC
start (typically
CC
is linearly
CC
start,
For transmission of low power with a good efficien-
cy in stand-by, an automatic burst generation sys-
tem is used, in order to avoid audible noise.
Normal Mode (Secondary Regulation)
The normal operating of the TV set is obtained by
sending to the TEA2260/61 regulation pulses gen-
erated by a regulator located in the secondary side
of the power supply.
This architecture uses the “Master/Slave Con-
cept”, advantages of which are now well-known
especially the very high efficiency in Stand-by
mode, and the accurate regulation in Normal
mode.
Stand-by mode or normal mode are obtained by
supplying or not the secondary regulator. This can
be ordonnered for example by a microprocessor in
relation with the remote control unit.
Regulation pulses are applied to the TEA2260/61
through a small pulse-transformer to the IN input
(Pin 2). This input is sensitive to positive square
pulses. The typical threshold of this input is 0.85V.
The frequency of pulses coming from the second-
ary regulator can be lower or higher than the fre-
quency of the starting oscillator.
The TEA2260/61 has no soft-starting system
when it receives pulses from the secondary. The
soft-start must be located in the secondary regula-
tor.
Due to the principle of the primary regulation, puls-
es generated by the starting system automatically
disappear when the voltage delivered by the
SMPS increases.
Stand-by Mode - Normal Mode Transition
During the transition there are simultaneously
pulses coming from the primary and secondary
regulators.
These signals are not synchronized and some
care has to be taken to ensure the safety of the
switching power transistor.
A very sure and simple way consist in checking the
transformer demagnetization state.
– A primary pulse is taken in account only if the
– A secondary pulse is taken in account only if the
With this arrangement the switching safety area of
the power transistor is respected and there is no
risk of transformer magnetization.
transformer is demagnetized after a conduction
of the power transistor required by the secondary
regulator.
transformer is demagnetized after a conduction
of the power transistor required by the primary
regulator.