TLE 4305
Application Information
The TLE 4305 is a voltage and current regulator for Switch Mode Power Supply (SMPS)
applications.
It controls the output voltage and the maximum output current of a power supply unit. It
is located on the secondary side of the SMPS.
The TLE 4305 consists of a output voltage control loop and a current control loop. The
driver is especially designed to drive the opto-isolator. The current controls the PWM
duty cycle of the primary regulator.
Isolated SMPS
Switch mode power supply (SMPS) systems generate a regulated DC voltage
V
Q
that is
isolated from the primary side. A maximum output current
I
Qmax
is defined to protect the
system in any load failures.
Line
SMPS
with
Cool Set
Secondary
Regulator
with
TLE 4305
Precise Output Voltage
Output Current precise limited
Short circuit protected
Opto
Isolator
AES02888
Figure 3
Isolated SMPS Principle
The principle of an isolated SMPS is shown in
Figure 3.
The primary side of the SMPS
is supplied by the line. The secondary side supplies a regulated voltage to the load.
Primary and secondary side are isolated from each other by the transformer and an opto
isolator.
A SMPS controller such as the Infineon TDA1683x controls the PWM duty cycle of the
output voltage signal. The signal is transmitted by a Transformer with n1:n2 (n: number
of windings). On the secondary side a load capacitor is charged. The secondary
regulator controls the output voltage
V
Q
and limits the output current. It generates an
analog control signal to the primary side through an opto isolator to regulate the PWM
duty cycle of the primary signal. The loop is closed through the primary SMPS regulator
and the transformer.
Simple SMPS defines the output voltage by a voltage divider and a transistor. This
requires very precise resistor values and due to the nature of the transistor the control
signal is dependent on temperature and device variation. The current limitation has to be
done on the primary side with elements suitable for high voltages.
Data Sheet
8
Rev. 2.2, 2008-11-17
INFINEON [ INFINEON TECHNOLOGIES AG ]
