Philips FM24 Service Manual page 97

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9.2.8 Power Supply Protections (Diagram P3)
Introduction
+9V_STBY_SW
STANDBY
DC_PROT
> 1
TEMP. ERROR
OVP
(Vs_unsw, Va,+5V,+3V3)
> 1
UVP
(Vs_unsw, Va,+5V,+3V3)
Vsago
Vs_UNSW OK
In general, all efforts need to be taken, to make a safe power
supply. Therefore, all major outputs are monitored with respect
to over- and/or under voltage. All protections are handled by
hardware. The software only monitors the hardware to
generate error codes for service.
C, errors of the power supply are transmitted to the µP on
2
Via I
the SCAVIO panel. If an error occurs, POWER_OK will change
from 'high' to 'low'. The errors are transmitted to the µP, on the
following ports and pin numbers of the I/O expander
PCF8574AT (item 7370):
Table 9-2 IC7370 Inputs
Pin Name
4 Vs
5 Va
6 +5V
7 +3V3
9 OVP
10 Switch
11 DC_PROT
12 TEMP
This POWER_OK signal is connected to an interrupt pin of the
OTC, in order to be read as fast as possible. This is very
important in case of a time limited error like over voltage. After
detection of the error, the control system will log the error in
NVM, and transmit the first occurrence back to the power
supply through the I
Note: The POK signal is fed to buffer 7366, together with the
'8V6 UNDER VOLTAGE' and 'SWITCH' sensing. The output of
this buffer, the POWER_OK line, will follow the inputs.
Operation
V Protection
S
Detection of over- or under voltage on V
IC7308-A and -B. If this voltage exceeds certain levels (set via
voltage dividers), the protection will activate the Power OK
(POK, active 'low'), which will shut down the set.
Circuit Descriptions and List of Abbreviations
1450
1460
Vac_SW
MAIN
MAINS IN
SUPPLY
Vs_UNSW
SUPPLY_ON OFF
&
LATCH
LATCH
POWER_OK
&
Discharge
&
Vs_UNSW
Va
or
SUPPLY
Vac_SW
OFF
Figure 9-13 Protections
Description
Detection of under- or overvoltage on Vs
Detection of under- or overvoltage on Va
Detection of under- or overvoltage on
+5V
Detection of under- or overvoltage on
+3V3
Detection of overvoltage on Vs, Va, +5V
or +3V3
Detection of functional switch
Detection of DC_PROT going high
Detection of over temp. inside power sup-
ply
2
C bus.
S_UNSW
Aux. outputs
+5V / Vcc
Vs
Va
CL16532099_012.eps
180901
9.3
9.4
by comparators
Digitized in Heiloo, Holland
FM24
V Protection
A
Detection of over- or under voltage on V
IC7308-C and -D. If this voltage exceeds certain levels (set via
voltage dividers), the protection will activate the Power OK
(POK, active 'low'), which will shut down the set.
V Protection
CC
Detection of over- or under voltage on V
comparators IC7330-A and -B. If this voltage exceeds certain
levels (set via voltage dividers), the protection will activate the
Power OK (POK, active 'low'), which will shut down the set.
+3V3 Protection
Detection of over- or under voltage on the +3V3 voltage by
comparators IC7330-C and -D. If this voltage exceeds certain
levels (set via voltage dividers), the protection will activate the
Power OK (POK, active 'low'), which will shut down the set.
OVP protection
This line detects, if one of the above mentioned voltage
protections is an over voltage protection. Therefore, this works
in combination with the above mentioned under-/over voltage
protections.
Latch Protection
When an OVP-, DC-, or Temperature protection occurs,
thyristor 6348 is fired and the LATCH signal is made 'low'. This
signal will switch 'off' the main supply and prevents that the
supply is switched 'on' again, as long as the protection is active.
In addition, the V signal can activate the LATCH signal (via
CEGO
TS7352 and 7348), but this is temporarily. This is done for
correct start-up behaviour.
DC Protection
Detection of a DC voltage on the audio amplifier outputs. If a
DC voltage is detected, TS7362 will activate the Power OK
(POK, active 'low'), which will shut down the set.
Temp Protection
Detection of the temperature (via PTC 3368) in the power
supply by comparator IC7366-A. If this voltage exceeds a
certain level (set via voltage dividers), the protection will
activate the Power OK (POK), which will shut down the set.
VGA Connector Panel (Diagram VGA)
The Video Graphics Array (VGA) panel serves as an interface
between the peripheral VGA equipment (Receiver box, PC,
etc.) and the SCAVIO panel. Some specifications of this panel:
• Two NVMs are present, which hold identification data for
the DDC line.
• Further, there are buffers present for the incoming and
outgoing sync signals.
• RC_OUT cinch for linking with other equipment.
Provision to terminate the incoming sync lines with 75 Ω via
•
the EBOX_PRESENT line.
For a description, see the next SCAVIO chapter.
SCAVIO Panel (Diagrams SC)
The Scaler Control Audio Video Input Output (SCAVIO) panel
contains:
• All the input connectors,
• Analogue and digital video processing,
• Scaler (co-processor)
• Interface to the PDP,
• Audio processing (excluding the audio amplifier),
• OTC (main processor), and
• RS232C in/out.
31/8/2014
9. EN 97
by comparators
A
(+5 V) by
CC