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Diva Dv79 Circuit description.
Overview
The DiVa DV/79 is a completely new design platform
and only shares it power supply board and display
board with the DV78.
The player is based around acclaimed Zoran Vaddis
V chipset coupled to high specification Wolfson D to A
converters for all six audio output channels and a
extremely high quality digital video encoder also
featured in this design is a HDMI output digital Video.
Power supply board.
Non-switching
Mains power arrives at IEC inlet socket SKT1 and is
filtered by EMC choke LI and Y caps C3 and C4,
mains switch SW2a/b switches both Negative and Live
phases before the power reaches the mains select
switch at location SW1 the switch allows the primary
windings of the transformer TX1 to be wired in either
Parallel or Series configuration.
The Bridge rectifying Diode package at location D1
forms the basis of the conventional power stage and
supplies a VN35V6 (-35.6v) to the Switch mode
stage, transistor TR1 is biased by 2v7 Zener diode
DZ1 and allows for the series Zener diodes DZ2, DZ3,
DZ3 to supply the VN13V5 and VN19V rails.
We will also see a simple A.C present circuit this is
used for delayed output relay operation and fast relay
closure under interrupted supply conditions thus
preventing power down op-amp offsets from reaching
the Audio output sockets.
Switch mode
The switch mode supply is formed around the
Driver/Control chip IC1 UC3843 (used in regulating
mode). The chip is referenced the –36.5V supply line
and the Digital ground DGND, the supply for the chip
is formed by the 12v Zener at location DZ6 and can be
seen on Pin 7 as VCC. The power supply allows for
the switch-mode to be tied the to Audio sampling
frequency for any given compatible format see Fig 1.
Fig 1 PSU clock control
Fs
PSUFS1
Frequency
Pin 11
select
IC305a
44.1 kHz
0
48 kHz
0
88.2 kHz
0
96 kHz
0
176.4 kHz
1
192 kHz
1
Others
1
The PSU sync signal is driven into the power supply via
Resistor R9 if no Sync is present the unit is set to free run at
xxxx due to the RT/RC network attached to Pin 4.
IC1 is running in regulated mode and monitors the voltage
output on the +5V and +3V3 D.C lines, the two voltages are
summed by TR8 and Driven into the VFB and Comp inputs
of IC1, the Voltage is then regulated by changing the time
base of the PWM output at pin 6 (longer the time base the
lower the voltage), the PWM switching frequency is driven
into the switch-mode transformer by the high speed Nmos
device at position M1, R5 is used to sense the Current
across the gate of the Nmosfet and in the event of a short
circuit will safely shut the power supply down. We derive the
12v Mech supply from the output of M1 using the Ultra-fast
Diode at location D8 to rectify the PWM line.
The D.C outputs from the switch mode have extensive
switch mode noise removing filters these are seen as 100n
caps down to ground and Wire wound inductors in series
with the supply rail.
Power supply main board
All the power supply rails are supplied to the main board via
the 32 way FFC conector at location CON1001.
The Digital supplies from the switch mode stage of the
power supply arrive as 3V3D, +5VD and +12VD we also see
the Display board power supplies arrive as –19V, -9 and
–13.5V all of the supplies have a second stage of
implemented on the board to remove all traces of ultra-sonic
noise.
The 3V3D rail is the main 3V3 rail used to power the digital
circuitry; +5VD is used for all 5v Digital/Video supplies the
+12VD is used for Scart switching and to power the HDMI
circuit.
The 1V8 rail is derived from the 3V3 rail and is regulated by
the adjustable regulator at location REG1003.
PSUFS0
PSUCLK
Pin 12
Output Pin 5
IC305a
of IC305a
0
44.1 kHz
0
48 kHz
1
44.1kHz
1
48 kHz
0
44.1 kHz
0
48 kHz
1
OFF
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