Philips DVDR615 Service Manual page 131

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Circuit-, IC descriptions and list of abbreviations
positive voltage on pin 7 of the transformer [5300] can be
assumed as constant for a switching cycle. The current in the
primary coil of the transformer [5300] increases linearly. A
magnetic field representing a certain value of the primary
current is formed inside the transformer. In this phase, the
voltages on the secondary coils are polarized such that the
diodes [6300, 6301, 6304, 6306, 6309, 6311, 6315 and 6318]
block. From the controller [7319] a current is supplied into the
CTRL input on the IC [pin 3, 7311] via optocoupler [7316]. Once
the switch on time of the switching transistor [7308] - that
corresponds to the current supplied into the CTRL input - has
been reached, the switching transistor [7308] is switched off.
When the switching transistor has been switched off, the
blocking phase begins. No more energy will be transferred
into the transformer. The inductivity of the transformer will still
attempt to keep the current flowing at a constant level (U=L*di/
dt). Switching off transistor [7308] interrupts the primary current
circuit. The polarity of the voltages on the transformer is
reversed, which means that the diodes [6300, 6301, 6304,
6306, 6309, 6311, 6315 and 6318] become conductive and
current flows into the capacitors [2302, 2308, 2316, 2322, 2325
and 2329] and the load. This current is also ramp-shaped (di/dt
negative, therefore decreasing).
The feedback control for the switched-mode power supply is
done by changing the conductive phase of the switching
transistor so that either more or less energy is transferred from
the rectified mains voltage at [2314/2315] into the transformer.
The regulation information is provided by voltage reference
[7319]. This element compares the 5V-output voltage via
voltage divider [3360, 3363, 3364] with an internal 2.5V
reference voltage. The output voltage of [7319] passes via an
optocoupler [7316] for insulation of primary and secondary
parts as a current value into pin 3 on the IC [7311]. The switch-
on time of the transistor [7308] is inversely proportional to the
value of this current.
Overload, power limitation, burst mode:
With increasing load on one or more of the power supply
outputs, the switch-on time for the power transistor [7308]
increases, and thus also the peak value of the delta-shaped
current through this power transistor. The equivalent voltage of
this current profile is passed from resistors [3330] and [3331]
via [3335] to pin 5 of the IC [7311]. If the voltage on pin 2
reaches approx. 0.4V in one switching cycle, the conductive
phase of the switching transistor is ended immediately. The
check is done in each individual switching cycle. This process
ensures that no more than approx. 50W can be taken out from
the mains ( = power limitation ).
If the power supply reaches the power limit, the output voltages
and the supply voltage V on pin 1 of the IC [7311] will be
CC
reduced following further loading. If V
at any point during this process, the output of the IC [7311, pin
6] is blocked. All output voltages and V
start-up cycle begins. If the overload status or short-circuit
remains, the power limitation will be activated immediately and
the voltages will again decrease, followed by another start-up
cycle ( Burst Mode ). The amount of power taken up from the
mains in burst mode is low.
Standby modes:
In the AV-Standby operating mode of the set, the DD_ON
control line is low switching off the +5VE and +12VE supply
[connector 1932] to the FEBE Frontend and DVD drive. This
reduces the amount of power taken from the mains.
In Low Power Standby mode, additional STBY control line is
high switching off the 12V, 5V, 5N and 3V3SW supply. In this
mode all functions are switch off and the slave µP (in idle mode)
and real time clock (32.768kHz) is running. This reduces power
consumption to less than 3W. In some program mode the
slave µP provides a wakeup service (STBY-line switches to
low), then the Chrysalis main controller starts up and asks for
the wakeup reason.
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is less than approx. 9V
CC
decrease and a new
CC
DVDR615/69
9.1.10 Tuner Frontend
The MOBO board supports 3 possible Tuner Frontend unit
namely:
* 1700 - PAL BG, DK and I Broadcast System
* 1701 - NTSC-M Broadcast System
* 1702 - not in used
It has a RF IN for antenna connection and RF OUT which
provides a RF loop through during Standby mode for
connection to the TV.
The Frontend [1701] (Tuner & IF-demodulator) is controlled by
the I2C (SCL_5V- and SDA_5V-) lines coming from the slave
µP.
Complete video processing is done in this unit and the video
output (CVBS) is taken out from the [VID_OUT] pin via
transistor 7700 as VFV-line to the Video I/O circuitry.
The audio-IF component SIF1 is taken out from the [SIF_OUT]
pin for demodulation in the sound processor [7600].
A modulator is also included in this unit. The audio- and video-
signal to the modulator are the ones from the selected input or
the playback path of the set (AMCO- and D_CVBS-line). Via
the MSW-signal and [7701] the modulator is switched on and
off. In opposite to this the antenna loop-through is opened or
closed. The CSW-line switches the modulator between CH3 or
CH4.
To achieve optimal tuning the AFC-line is detected by the slave
µP via an analog input.
Audio demodulator
The sound demodulation is done by the MSP3425 [7600],
which is also fully controlled via I
(determination of bandwidth, amplitude, standard, ...). The
audio signals are available at pin 30 and pin 31 of [7600] and
fed as AFER- & AFEL-line to the audio-I/O for further
processing.
9. EN 131
2
C-bus by the slave µP