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5
Protection circuit that activates against a PRTCT ERR error
2 When the main power supply becomes LO level
because of short-circuit or disconnection of
connectors
2 -1 Short-circuit-detection circuit for the amplifier
power circuit (VH+[VP+15], VD+5, -12 V [VA-12])
Circuit for shutting the power off when VP+15, VD+5, or VA-12
is short-circuited to ground (GND)
I
VD+5
AMP Assy
E
VD+5
Q101_1/2
(Q103_1/2)
R108
C
R101
27k
to
(R104)
XPROTECT
C
1k
(µ-com)
B
Q102_1/2
(Q104_1/2)
+
C101
E
(C102)
1/50
* ( )means the wiring No. of VP+15 line.
• In Normal mode, as Q101 (Q103) (E2, B2, C2) and Q102
(Q104) (E2, B2, C2) are on, the voltage at Point A is about 5 V.
The voltage at Point B is therefore about the same. As Q101
(Q103) (E, C, B) is off, Q102 (Q104) (E, C, B) is also off.
(1) When VH+(VP+15) is short-circuited to GND
As the voltage at Point B becomes almost ground potential, and
Q101 (Q103) (E, C, B) then Q102 (Q104) (E, C, B) are turned on,
the level of XPROTECT becomes low.
→ The microcomputer detects the XPROTECT level and shuts
the power to the unit off.
(2) When VH-(VA-12) is short-circuited
As the electric potential of VE at Q102 (Q104) (E2, C2, B2)
becomes the same as that at VB, Q102 (Q104) (E2, C2, B2) is
turned off. Following this, Q101 (Q103) (E2, B2, C2) is turned
off, which changes the voltage at Points A and B to a value other
than 5 V. Therefore, Q101 (Q103) (E, C, B) then Q102 (Q104) (E,
C, B) are turned on, the level of XPROTECT becomes low.
(3) When VD+5 is short-circuited
The level of the XPROTECT line becomes low. The
microcomputer detects the XPROTECT level and shuts the power
to the unit off.
5
6
VH+
(VP+15)
Q101_2/2
(Q103_2/2)
E2
D101
(D102)
Q102_2/2
B2
(Q104_2/2)
B
B
C2
B2
C2
R102
(R105)
E2
10k
R109
R103
A
820
(R106)
D105
10k
(D106)
VH–
(VA–12)
6
7
3 When the FAN connector is disconnected or
when rotation of the fan is interrupted
I
AMP Assy
VD+5
R3654
R108
27k
to
XPROTECT
(µ-com)
C2
C
B2
Q3651_2/2
RN1901
E2
E
Q3651_1/2
RN1901
If no fan is connected between FAN+ and FAN-, or when the fan
cannot rotate because of a foreign object caught in the blades, the
BASE of Q3652 becomes OPEN, and Q3652 and Q3651-
B) are turned off. Then Q3651-
the level of XPROTECT becomes low.
→ The microcomputer detects the XPROTECT level and shuts
the power to the unit off.
When FAN+ and FAN- are short-circuited, the electric potential at
Point A becomes higher than GND level by the addition of the
values at D3656 and D3657. As this value is lower than that at
D3658, Q3651 (E, C, B) is turned off, Q3651 (E2, B2, C2) is
turned on, and the level of XPROTECT becomes low.
XV-EV500
7
8
VPF+15
1.8k
A
D3658
Q3652
UDZS3.9B
DTA124TK
B
R3657
R3658
+
2.2k
33(1/4W)
D3657
C3652
47/50
1SS355
D3655
1SS133
Q3654
R3655
2SD2144S
8.2k
D3651
1SS133
R3656
22k
V-12F
(E2, B2, C2) is turned on, and
2/2
8
A
FAN+
B
FAN–
(E, C,
1/2
C
D
E
F
117
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