XW-HTD640
59
5
7
8
5
6
7
8
C
D
F
A
B
E
7.1.4 PROTECTION CIRCUIT
UNREG
PRE+5
V+B (UNREG PRE12)
To
XPROTECT
H/L CONT
PRE12
PRE12
Q71
R74
47K
R74
4.7K
470K
10K
R73
100
1
µ
D72
PRE5
R78
4.7K
D74
390
390
390
R3654
4.7K
R3655
22
R3656
220
R3661
33K
R3667
10K
47K
Q3653
R3679
680
R3652
680
R3670
33
R3665
33
R3659
33
R3666
33
390
390
47K
22K
10K
10
22K
R76
4.7K
D71
D75
D73
Q3651
Q3654
2SC2412K
Q3655
DTC114TK
D3664
D77
D3657
R75
R3681
R3664
R3663
R3657
R3651
D3651
D3652
D3653
D3654
D3656
D3665
Q3652
1/50
1/50
100/10
FAN
C3656
47/35
10/50
PROTECT Operation Description
This circuit has following five items that performs the Short
detection.
1
PRE5
2
PRE12
3
FAN +B (for Hi rotation)
4
FAN short
5
About
1
to
3
When the voltages of
1
to
3
fell in the voltage (less than
about 3.2V) that Q71 turned ON, and turn Q3654 ON via
R73 and D75.
→
XPROTECT becomes low.
About FAN short or open detection
At normal state:
The voltage appears in Q3655 base by current that flows
to the FAN, and so Q3655 is always ON.
Q3654 cannot turn ON so that the voltage appears only with
Vce(sat) of Q3655 in D3665 anode.
In addition, Q3654 cannot turn ON so that the voltage (Vb
×
1/4.3=lesst than 0.8V) that divided the base voltage of
Q3655 with 33k and 10k is the voltage of D3664 anode.
Therefore, Q3654 maintains the OFF state.
In the short or open state:
The voltage appears at D3664 anode in the short state
and appears at D3665 anode in the open state.
Q3654 turns ON and XPROTECT becomes low (Active).
I
REGULATOR ASSY
(AWU7969)
www. xiaoyu163. com
QQ 376315150
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TEL 13942296513
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TEL 13942296513 QQ 376315150 892498299
