Philips PM32671 Service Manual page 46

2-30
-
The flyback converter (see Fig. 2.10)
The flyback converter functions as follows:
If transistor V1413 conducts under the control of base current 13, the collector current
During the period T I , the voltage level on the collector of V1413 i s e a t earth potential.
A t the moment when V1413 i s blocked i t s collector current
A t the same time, the energy present in T1402, built up during period T I , is discharged via the secondary
winding of T I 4 0 2 during period T2.
This results in current17 which, after rectification and smoothing, i s fed t o the various circuits in the instrument.
The energy that was present in T I 4 0 2 i s consumed a t point A and the procedure described above is repeated
after 40 ps.
Diode V1415, capacitor C1430 and resistors R1418, R1425 serve t o eliminate the switching spikes present on
the collector of transistor V1413.
A
u c
I
2.10 Fly-back converter
Fig.
A
I
I
M A T 9 4 9
16 i s switched o f f (see point B of Fig. 2.10).
increases t o 4 A.