Philips 7629 Service Manual page 87

Protection Events
The SMPS IC 7520 has the following protection features:
Demagnetization sense
This feature guarantees discontinuous conduction mode operation in every situation.
The oscillator will not start a new primary stroke until the secondary stroke has ended.
This is to ensure that FET 7521 will not turn on until the demagnetization of transformer
5520 is complete. The function is an additional protection feature against:
saturation of the transformer,
damage of the components during initial start-up,
an overload of the output.
The demag(netization) sense is realized by an internal circuit that guards the voltage
(Vdemag) at pin 4 that is connected to V
below shows the circuit and the idealized waveforms across this winding.
Figure:
winding by resistor R
CC
(R3522). The Figure
1