TEA152x family
SMPS ICs for low-power systems
Rev. 02 — 25 January 2006
Product data sheet
1. General description
The TEA152x family STARplug+ is a Switched Mode Power Supply (SMPS) controller IC
that operates directly from the rectified universal mains. It is implemented in the
high-voltage EZ-HV SOI process, combined with a low-voltage BiCMOS process. The
device includes a high-voltage power switch and a circuit for start-up directly from the
rectified mains voltage.
A dedicated circuit for valley switching is built in, which makes a very efficient slim-line
electronic power plug concept possible.
In its most basic version of application, the TEA152x family acts as a voltage source.
Here, no additional secondary electronics are required. A combined voltage and current
source can be realized with minimum costs for external components. Implementation of
the TEA152x family renders an efficient and low cost power supply system.
2. Features
s
Designed for general purpose supplies up to 30 W
s
Integrated power switch:
x
TEA1520: 48
Ω;
650 V
x
TEA1521: 24
Ω;
650 V
x
TEA1522: 12
Ω;
650 V
x
TEA1523: 6.5
Ω;
650 V
s
Operates from universal AC mains supplies (80 V to 276 V)
s
Adjustable frequency for flexible design
s
RC oscillator for load insensitive regulation loop constant
s
Valley switching for minimum switch-on loss
s
Frequency reduction at low power output makes low standby power possible
(< 100 mW)
s
Adjustable overcurrent protection
s
Undervoltage protection
s
Temperature protection
s
Short-circuit winding protection
s
Simple application with both primary and secondary (opto) feedback
s
Available in DIP8 and SO14 packages
Philips Semiconductors
TEA152x family
SMPS ICs for low-power systems
8. Functional description
The TEA152x family is the heart of a compact flyback converter, with the IC placed at the
primary side. The auxiliary winding of the transformer can be used for indirect feedback to
control the isolated output. This additional winding also powers the IC. A more accurate
control of the output voltage and/or current can be implemented with an additional
secondary sensing circuit and optocoupler feedback.
The TEA152x family uses voltage mode control. The frequency is determined by the
maximum transformer demagnetizing time and the time of the oscillator. In the first case,
the converter operates in the Self Oscillating Power Supply (SOPS) mode. In the latter
case, it operates at a constant frequency, which can be adjusted with external
components R
RC
and C
RC
. This mode is called Pulse Width Modulation (PWM).
Furthermore, a primary stroke is started only in a valley of the secondary ringing. This
valley switching principle minimizes capacitive switch-on losses.
8.1 Start-up and undervoltage lock-out
Initially, the IC is self supplying from the rectified mains voltage. The IC starts switching as
soon as the voltage on pin V
CC
passes the V
CC(start)
level. The supply is taken over by the
auxiliary winding of the transformer as soon as V
CC
is high enough and the supply from
the line is stopped for high efficiency operation.
When for some reason the auxiliary supply is not sufficient, the high-voltage supply also
supplies the IC. As soon as the voltage on pin V
CC
drops below the V
CC(stop)
level, the IC
stops switching and restarts from the rectified mains voltage.
8.2 Oscillator
The frequency of the oscillator is set by the external resistor and capacitor on pin RC. The
external capacitor is charged rapidly to the V
RC(max)
level and, starting from a new primary
stroke, it discharges to the V
RC(min)
level. Because the discharge is exponential, the
relative sensitivity of the duty factor to the regulation voltage at low duty factor is almost
equal to the sensitivity at high duty factors. This results in a more constant gain over the
duty factor range compared to PWM systems with a linear sawtooth oscillator. Stable
operation at low duty factors is easily realized. For high efficiency, the frequency is
reduced as soon as the duty factor drops below a certain value. This is accomplished by
increasing the oscillator charge time.
To ensure that the capacitor can be charged within the charge time, the value of the
oscillator capacitor should be limited to approximately 1 nF.
8.3 Duty factor control
The duty factor is controlled by the internal regulation voltage and the oscillator signal on
pin RC. The internal regulation voltage is equal to the external regulation voltage (minus
2.5 V) multiplied by the gain of the error amplifier (typically 20 dB which is 10
×).
TEA152X_FAM_2
© Koninklijke Philips Electronics N.V. 2006. All rights reserved.
Product data sheet
Rev. 02 — 25 January 2006
5 of 20
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