The IC TDA 4605-3 controls the MOS-power transistor and performs all necessary control and

protection functions in free running flyback converters. Because of the fact that a wide load range

is achieved, this IC is applicable for consumer as well as industrial power supplies.

The serial circuit and primary winding of the flyback transformer are connected in series to the input

voltage. During the switch-on period of the transistor, energy is stored in the transformer. During the

switch-off period the energy is fed to the load via the secondary winding. By varying switch-on time

of the power transistor, the IC controls each portion of energy transferred to the secondary side

such that the output voltage remains nearly independent of load variations. The required control

information is taken from the input voltage during the switch-on period and from a regulation winding

during the switch-off period. A new cycle will start if the transformer has transferred the stored

energy completely into the load.

Type

Ordering Code

Package

TDA 4605-3

Q67000-A5066

P-DIP-8-1

Control IC for Switched-Mode Power Supplies

using MOS-Transistor

Bipolar IC

TDA 4605-3

P-DIP-8-1

Features

q

Fold-back characteristics provides overload protection for

external components

q

Burst operation under secondary short-circuit condition

implemented

q

Protection against open or a short of the control loop

q

Switch-off if line voltage is too low (undervoltage switch-off)

q

Line voltage depending compensation of fold-back point

q

Soft-start for quiet start-up without noise generated by the

transformer

q

Chip-over temperature protection implemented (thermal

shutdown)

q

On-chip ringing suppression circuit against parasitic

oscillations of the transformer

q

AGC-voltage reduction at low load

Version 2.0

3

1 Jul 2002