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STR-W6700 Series
Application Note (Ver0.3)
Preliminary
Japanese: Sept. 02
English: Oct. 02
SANKEN ELECTRIC CO., LTD.
Application Engineering Department -1
Semiconductor Operations
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5 Block Diagram
VCC
OVP
Reg&
Iconst
Start
Stop
Burst
Burst
Control
Abnormal
latch
R
Q
S
DRIVE
Reg
Delay
RQ
S
OLP
OSC
MaxON
QS
R
BSD
Bottom Selector
Soft Start
Counter
FB
OCP
BD
D
S/GND
FB
OCP/BD
SS/OLP
Functions of Each Terminal
Terminal
No.
1
2
3
4
Symbols
STR-W6700 STR-X6700
TO220F-6L
TO3PF-7L
D
2S
S/GND
GND
VCC
5 SS/OLP
6 FB
7 OCP/BD
Terminal Descriptions
Functions
Drain Terminal
Source/Grand Terminal
Power Supply Terminal
Delay at Overload/Soft-Start
set up Terminal
Feedback Terminal
Overcurrent Protection
Input/Bottom Detection
Terminal
MOSFET Drain
MOSFET Source and Ground
Control Circuit Power Supply
Input
Overload Protection and Soft-
Start Operation Time set up
Constant Voltage Control Signal
Input, Blocking Oscillation
Control
Overcurrent Detection Signal
Input / Bottom Detection Signal
Input
1. STR-X6700 is a HIC which has a different package from STR-W6700.
2. Terminated Pin (Refer to the Outline Drawings)
5
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8.1.3. Overvoltage Protection Circuit
Where the voltage exceeding 27.5V(TYP) is imposed on between Vcc and GND terminals, the OVP
circuit of the control IC starts its operation and turns latch-mode, and the control IC stops its oscillation.
Generally, the Vcc terminal voltage is supplied from the auxiliary winding of the transformer, and the
voltage is in proportion to the output voltage; thus, the circuit also operates at that time when the
overvoltage output of the secondary side comes out such as the voltage detection circuit open.
The secondary output voltage at the Overvoltage Protection circuit operation is obtained form the
following formula:
Vout( OVP)
VOUT (OVP)
V
VOUT aVtCNC ormal OV OpUeTra×ti2o7n.5
TYP
--------------------------------------------------------- X 27.5V (TYP) …… (1)
Vcc Terminal Voltage at Normal Operation
11
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