Protection Circuit Schematic Diagrams - Sony KDP-51WS550 Training Manual

AX-1 Protection Circuit Schematic Diagrams
Direct Latch/AC-Relay Shut-OFF Circuits (B+ OVP, B+ OCP, IK-Prot 2 and DC Regulator
protection)
TO MA BRD.
D6122
IC0001
9 CN2011
9
CN5006
D6803
+136V
R6814
R6821
R6816
C6804
D BOARD
NOTE: In this diagram, B+ OCP and B+ OVP has system designated flash sequences. The IK-PROT 2 and
REG-PROT circuits are connected in parallel with the B+ OCP and B+ OVP circuits. When the IK-PROT 2
and REG-PROT trigger, the STBY/TIMER LED will flash 2X and 3X respectively.
B+OCP Protection Circuit
(Reference Figure 4-2)
The current in the +135V line is monitored using R6812 and Q6803. R6812 is the current sensing resistor. The
current in the +135V line flows direct through R6812. The voltage drop across R6812 in normal operation is very
low approximately 0.2V. So, the +135V is passed with very little loss in normal operation. The voltage on the left
side is essentially equal to the voltage on the right side of R6812, and because R6812 is connected across the
base/emitter junction of Q6803, there is no 0.6V difference across the junction and Q6803 is OFF.
When the current in the +135V line begins to increase due to a defect the voltage drop across, R6812 will also
increase. Because of the increased voltage drop across R6812, the voltage on the left side of R6812 will remain
constant but the voltage on the right side of R6812 will decrease. The decreased voltage on the right side is
applied to the base of Q6803 through D6805. Once the voltage drop across R6812 is large enough to cause a
0.6V difference across Q6803, base/emitter junction Q6803 turns ON.
Current now flows through the voltage divider consisting of R6816, R6817 and R6815. The voltage drop across
R6815 is applied to the anode of D8005 and then D6122 forward biasing both diodes. A high is then applied to
the LATCH. The LATCH reduces the voltage at the base of Q6102, turning it OFF, which removes the ground to
the AC-Relay turning it OFF and therefore shutting OFF the unit.
The TV video is muted and the AC relay shuts down and the Stby/Timer LED flashes a 2X sequence.
FROM
R6118
IC0002
P-CONT
MA BOARD
Q6108
R6122
B+OCP
R6812
+135V
D6805
12V
C6803
134V
R8022
R6831
Q6803 R6805
C8012
R6817
0V
R6815
FIGURE 4-2 - AX-1 LATCH/AC-RELAY SHUT-OFF PROTECTION CIRCUITS
R6113
D6115
Q6102
R6111
Q6105
C6119 R6123
TO MA BRD. IC0001
+135V
IK_PROT 2
R8040
R8039
D8023 R8038
5V
R8043
Q8007
R8030
0.6V
0V
R8027
C8017
R8036
FBT
R8041
PIN 1
(ABL)
R8039
20
4. AX-1 Protection Circuits
TO
AC RELAY
RY6000
A BOARD
D6121
CN2011
8
8
CN5006
B+
0VP
D6804
Q6802
R6811
3V
15V
R6810
15V
2
IC6801
3
1
135V
R6809
+135V
FROM
D6508
REG PROT.
D6208
IC6200
2
9V REG
D6207
10V
D6206
IC6201
2
5V REG
D6205
6V
D6204
IC6202
2
3.3V REG
D6203
5.6V
D6212
IC6203
2
3.3V REG
D6211
5.6V
TVP16.4-2 1/13/04