16
6-4 SMPS CIRCUIT SECTION
Power supply is composed of line filter, switching AMP and switching trans circuit. Line filter circuit
removes the noise element of power line supplied from outside and prevents noise generated in
switching amp from flowing out to external power line. The circuit is made up of C401, L401, C402
and C403.
AC voltage supplied through line filter circuit is supplied to D401 and converted to ripple voltage,
and then converted to DC through the operation of C404.
The switching circuit operates as following; As the DC is supplied to FE401 Gate through R402
(overvoltage preventive resister) and R403 (Start Resister), FE401 is turned on, provides pulse to
T401 PINs 2 and 4, and supplies the voltage to T401 PINs 5, 6 and 7. The voltage supplied to PINs
5, 6 and 7 is supplied to Q403 Base and on both ends of R402.
The voltage to Q402 Base is variable by V/R401, and you can have the required voltage for the
second destination. Therefore, if high voltage is supplied to Q403 Base, voltage to Q402 Base gets
lower, and collector voltage goes up. On the other hand, if low voltage is supplied to Q403 Base,
Q402 Base voltage gets lower and collector voltage goes down.
KTN-2001/1401
KORTEK Corporation