Version 2.0

9

1 Jul 2002

TDA 4605-3

Pin 8

The zero detector controlling the logic block recognizes the transformer being discharged by

positive to negative zero crossing of pin 8 voltage and enables the logic for a new pulse. Parasitic

oscillations occurring at the end of a pulse cannot lead to a new pulse (double pulsing), because an

internal circuit inhibits the zero detector for a finite time

Start-Up Behaviour

The start-up behaviour of the application circuit per sheet 88 is represented an sheet 90 for a line

voltage barely above the lower acceptable limit time

–

–

–

The current drawn by the IC in this case is less than 1.6 mA.

If

current draw max. rises to 12 mA. The primary current- voltage reproducer regulates

and the starting impulse generator generates the starting impulses from time point

feedback to pin 8 starts the next impulse and so on. All impulses including the starting impulse are

controlled in width by regulating voltage of pin 1. When switching on this corresponds to a short-

circuit event, i.e.

depending on the regulating voltage feedback (the IC operates in the overload range). The IC

operates at the overload point. Thereafter the peak values of

attempt is aborted (pin 5 is switched to low). As the IC remains switched on,

to

time point

fall below

primary voltage monitor then clamps

up attempt begins at time point