Philips dvd 962 sa service manual

Page 1

9. Circuit Descriptions and List of Abbreviations

1. Introduction power 'switch' (MOSFET). The regulation of the 'duty cycle',

2. Power Supply controls the supply output, at a fixed switching frequency

3. Loader/Monoboard (approximately 58 kHz, determined by the RC timing

4. Data Processing components at pin 4).

5. Control and Display

6. Abbreviations The UC3842 (item IC1) is a high performance, fixed frequency,
current mode controller for DC-to-DC converter applications.

Notes: This integrated circuit features a:

0 Figures can deviate slightly from the actual situation, due - trimmed oscillator for precise duty cycle control,

to different set executions.
- For a good understanding of the following circuit
descriptions, please use the diagrams in chapter 6 and 7. current sensing comparator and
Where necessary, you will find a separate drawing for high current totem pole output ideally suited for driving a
clarification. power MOSFET (item 01).
Also included are protective features consisting of input and
reference under-voltage lockouts each with hysteresis, cycle
by cycle current limiting, programmable output dead time and
a latch for single pulse metering.

temperature compensated reference,
high gain error amplifier,

9.1 Introduction

9.1.1 Features

9.2.2 Output Voltages
The SACD 900/DVD9628A range is a new model DVD/SACD
player and is equipped with:
v Build in MPEGZ, AC-S and DSD decoder,
6 channel audio output,
RGB video output on SCAFtT (Europe only),
YUV output,
Progressive scan (for DVDQSZSA Non-Europe models),
CD-RW compatible.

+12V_stdby (present during standby).

+5V_ stdby (present during standby).

+5V_digital (will switch off via QB during Standby).
+5V7AV (will switch off via 03 during Standby).
3V3 (present during standby).

-5V (will switch off during standby).

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9.2.3 Operation
9.1.2 Differences

Power Supply
The SACD 900/DVDQGZSA is derived from the SACD 1000. It ______________________________________________________ .
has a new Audio/Video board, Front Display board.
Progressive scan board (same as used in Step2001 DVD-
player) and another Power Supply module (same as used in
Step2001 DVD-players).

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9.1.3 Modules

CONTROL :
l 7

The main modules are: l {
Power Supply Unit (PSU). l Rm 107 3 §_ 5

Mercury 1 Loader - VAL6011
ASD1.1 Mono Board.

Audio Video (AN) Board.
Front Display Board.
Progressive Scan Board.

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9.1.4 Service

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DVD generations.

Flashing of the application-SW is not possible with the ComPair Figure 9'1

cable, except with a CD-Fl disc. For sets with Mask-ROM

software, replace it with a programmed Flash (available via Mains Input Circuit

your Philips Sen/ice organisation). The bridge rectifier (DI-D4) rectifies the mains voltage, after

which 05 smoothens this voltage. The DC voltage across this

capacitor is the DC input voltage (approximately 300 V), to pin

1 of transformer T1.

The mains input also consists of a (differential mode) lightning

9-2-1 Introduction protection ZNFt1 and a (common mode) lightning protection
SP1 (spark gap).

9.2 Power Supply Unit

This supply is a Switching Mode Power Supply (SMPS), which
uses the control IC UCSB42 to produce pulses to drive the

Page 2

Start-up and Take-over Circuitry

With the mains voltage input, C7 will charge. When this
voltage, (at pin 7 of |Ct), reaches the start-up threshold of min
14.5 V, the control circuit starts to operate.

After start-up, |C1 requires a maximum sinking current of 17
mA, which the start-up circuitry cannot deliver. Therefore, a
take-over circuitry (a coupled winding of transformer T1) is
present. The voltage at this point will take over the supply
voltage at pin 7 of the IC.

If the take-over circuit does not function, the IC will switch off
again at the minimal operating voltage of 8.5 V. The whole
operation cycle will repeat itself with audible hiccup sound if
take-over is not present.

9.3

Secondary Voltage Sensing

The secondary voltage regulating circuit comprises of opto-
coupler ICZ (which isolates the error signal from the control IC
on the primary side), and a reference component ICS (TL431).
The reference component has two functions:

0 a very stable and accurate reference diode

' a high gain amplifier.

9.3.1
TL431

2.5V

A

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Figure 9-2

When the output voltage increases (due to a reduction in the
load), the voltage across R23 increases to above the internal
reference voltage of 2.5 V. ICB will conduct and the current
through the opto-coupler will increase. This results in an
increase of the voltage at pin 2 of IC1, which will reduce the on
time of FET Q1.

In the event of an output voltage decrease (due to an increase
in the load), the control circuit will operate in the opposite way.

Primary Current Sensing

The current through FET Qt , will result in a voltage drop across
R3A. This line goes to pin 3 of IC1, which is the current sense
input. The higher the input voltage, the more the primary
current is limited. In this way, the maximum output powerof the
power supply is limited.

Under-voltage Protection

Two under-voltage lockout comparators are incorporated, to
guarantee that IC1 is fully functional

before the output stage is enabled. Separate comparators with
built-in hysteresis monitor both the supply voltage at pin 7 and
the reference voltage at pin 8,

If the supply voltage at pin 7 drops below 10 V (typical), e,g.
due to a shorted secondary voltage or

excessive load, the drive pulse at pin 6 is disabled and the
controller will switch off.

Over-voltage Protection

The over-voltage circuitry (ZD1, Q7, and OS) is used to detect
an over-voltage situation on the secondary side of the
transformer.

If, after start-up, the voltage at the zenerdiode ZD1 will exceeds
its zener voltage, the internal latch circuit is triggered (via pin
1), the output buffer is disabled. and the SMPS goes into over-
voltage protection. Now a complete restart sequence is
required.

Note: If the event of the over-voltage situation remains present,
the SMPS will go in sequence of protection, start-up, protection
and the cycle repeats. This effect is highly audible.

Loader/Monoboard

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Figure 9-3

The Servo Part

The Optical Unit

The optical unit consists of two lasers, one for CD with a
wavelength of 780 nm, and one for DVD with a wavelength of
650 nm. The TZA1033 (item 71 02) controls the data from these
lasers, and the supply to them.

The Signal Processor TZA 1033

The TZA1033 (or DVDALASZ) is an analogue pre-processor
and laser supply circuit. It contains data amplifiers and several
options for radial tracking and focus control.

It is possible to optimise the dynamic range of this pre-amp/
processor combination for the LF sen/o and RF data paths. The
gain in both channels is separately programmable. This will
guarantee an optimal playability for all kind of discs.

Also, a dual laser supply is implemented, with fully automatic
laser control including stabilisation and an ON/OFF switch, plus
a separate supply pin for power efficiency.

The servo signals go to the MACE2 servo processor, while the
HF output signal, goes to the SAA7335 decoder (item 7311).

The Servo Processor MACEZ

The servo circuit in the MACE2 to (item 7207), takes care of
the servo controls. In a CD system, there are some 12 control
loops active. About six of them are needed to adjust the servo
error signals, that is once per disc rotation. It also adjusts
offsets, signal amplitudes, and loop gains (AGCs), to enlarge
system robustness and to avoid expensive potentiometer
adjustments in production.

The other six loops determine the laser spot position on the
disc in the radial, axial (focus), and tangential directions.

It also has to take care that the spot accesses a required
position as fast as possible. This access system consists of two
parts, namely the actuator and the sled, which are (within a
certain range) mechanically and electrically independent.
Therefore, during an access, the servo has to control as well
the actuator as the sled.

The analogue signals from the diode pro-processor are
converted into a digital representation using A/D converters.
For the communication between the host processor (STi5505)
and the servo processor the S23 bus is used, this supports full-
duplex asynchronous communication.

Note: For an extensive description of the MACE2 IC, see
Service Manual 3122 78511010.

The Decoder SAA7335

The SAA7335 (item 7311) is a high-end combined Compact
Disc (CD) and Digital Versatile Disc (DVD) compatible
decoding device. The device operates with an external 32 KB
SFtAM for DVD error correction and die-interleaving operations.