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EN 96
9.
9.2.7
Aux. Supply (Diagram P7)
The Aux. supply part, hosts the supplies, which are derived
from the V
supply:
S
•
V
supply,
A
•
V
supply,
CC
•
3V3 supply,
•
Audio supply (V
SND_POS
In addition to the FM23 monitor, a circuit is added ( around
7143, 7144, and 7145), which takes care that the V
supplies are discharged immediately after set switch 'off'. This
to prevent discharge spikes of the elcaps. The circuit will
ground the supply voltage of IC7112 as soon as its trigger line
(+9V_STBY_SW) is switched 'off'.
V
Supply
A
The V
voltage is derived from the LLC supply '77-100V' line
A
via a down converter principle. Control IC TEA1507 (item
IC7112) and MOSFET TS7117 are used.
S
Vin
D
I
T
S
Vin
D
S closed
S open
I
I
T
D
δT
T
Figure 9-11 Principle of Down Converter
After closing switch 'S', the linear in time increasing current I
will charge capacitor C.
Opening switch 'S' will generate a counter-e.m.f. (= reverse
voltage) in coil L, trying to maintain current I
via diode D (this diode is also called 'freewheel diode').
Therefore, after opening 'S', the magnetic energy stored in coil
L will be transferred to electrostatic energy in capacitor C. The
V
will only supply current during the time that 'S' is closed
IN
while a constant current is flowing through R
V
is directly proportional with V
OUT
closed and reverse proportional with period time 'T'. Therefore,
by changing the duty cycle, it will be possible to control V
To apply this on the FM24 (diagram P7): replace switch 'S' by
FET TS7117, coil L by L5120, diode D by D6120, C by C2121,
V
= 77-100V, and V
IN
OUT
Stabilising is done in the same way as for the V
mixed into the feedback voltage, using an additional TL431
(7011 at schematic P6). Control signal V
FM24
Circuit Descriptions and List of Abbreviations
and V
).
SND_NEG
and V
A
L
V
OUT
+
R
C
L
I
D
L
V
OUT
+
R
L
C
. δT
V
V OUT =
IN
T
CL 26532038_009.eps
280302
. This is possible
T
.
L
and the time that 'S' is
IN
= V
.
A
supply. V
S
, coming from the
RA
display, influences the output of the V
voltage of the V
V
= 30 + (20 * V
A
V
Supply
CC
This part delivers, besides the V
V (for optional Fan control) and derived from that, an +8V6 (for
small signal analogue circuitry).
The V
voltage is derived from the V
CC
converter principle. Control IC TEA1507 (item 7212) and
MOSFET 7212 are used.
S
V
IN
V
IN
Figure 9-12 Principle of Flyback Converter
After closing switch 'S', the current I
The magnetic energy in the primary coil is directly proportional
with the self-inductance of the coil and current I
time the switch is closed). The voltage polarity at the secondary
winding is negative (due to different winding direction),
meaning that diode D will block. Capacitor C will discharge via
R
, V
will decrease.
L
OUT
Opening switch 'S' will generate a counter-e.m.f. in the primary
winding, trying to maintain current I
of the secondary voltage will inverse. The magnetic energy,
stored in the coil, will now be transformed to the secondary
side. Diode D will now conduct, capacitor C will be charged and
U
will increase.
OUT
To apply this on the FM24 (diagram P7): replace switch 'S' by
FET TS7217, coil L by L5220, diode D by D6224, C by C2224,
V
= V
IN
S_UNSW
3V3 Supply
The 3V3 voltage, is directly derived from the LLC supply (+15V
line). Via a fuse (1005/1045), this voltage is rectified by diodes
6021/6045 and smoothed by C2022. Via control IC L4973V
(item 7260), the 3V3 voltage is generated. This IC contains a
complete down converter, with integrated MOSFET.
Audio Supply
,
This is a 'floating' symmetrical supply (±14.5 V) derived from V
T
via transformer 5290. Because this voltage is tightly coupled to
the V
voltage, this voltage varies considerable, between 11 V
S
(max. load, V
The Audio ground is connected to the normal secondary
ground, with a capacitor (C2290) and a resistor (R3292) in
parallel, to have the possibilities to suppress spurious
oscillations.
.
OUT
is
RA
supply. The output
A
supply varies according the following formula:
A
).
RA
voltage (+5 V), also a +12
CC
voltage via the flyback
S
D
+
-
+
C
+
S
-
Id
D
-
+
Isec
+
C
-
S
+
will increase linear in time.
D
. Through this the polarity
D
, and V
= V
.
CC
OUT
= 70 V) and 20 V (min. load, V
S
V
OUT
RL
V
OUT
RL
CL 26532039_010.eps
280302
(thus with the
D
S
= 90 V).
S
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