Seventeam 12 V to 3.3 V 15 A Buck Converter Power Supply (1995)

I was interested in converting 12 V to 3.3 V at 15 A and so I stripped down the about 1995 made (in Taiwan) Seventeam PC Power Supply Buck Converter. Here are some photos and schematics of it.

12 to 3.3 V 15 A Buck Converter by Seventeam Electronics Ltd

Seventeam Electronics Co., LTD. is a Taiwanese manufacturer of power supplies for Personal Computer and Industrial PC. Some PSU models from Seventeam are sold by Cooler Master and Silverstone under their own brand names.

 PCB measures

 

 Parts Lay Out

 

Parts on PCB

Buck Converter Schematics (12 to 3.3 V at 15 A)

Seventeam 3V3 15A Buck Converter Parts List :

R1    1 k
R2    2.2 ohm
R3    27 k
R4    2 k
R5    10 k
R6    100 k
R7    10 k
R8    1.8 k
R9    1 k
R10  56 ohm
R11  15 ohm
VR    1 k trimmer
J1      0 R jumper

C1    4u7 50V elco
C2    2200u 50V elco
C3    102 blue small    = 1n
C4    10u 50V elco
C5    102 blue small    = 1n
C6    101 blue small     = 0.1n
C7    152 blue small    = 1n5
C8    4u7 50V elco
C9    104 blue small    = 100n
C10  2200u 50V elco
C11  2200u 50V elco
C12  104 blue small    = 100n

Q1    2SK1388    Power N-MOSFET RDSon 0.022 ohm 35A 30V 60W
Q2    TYN408G   Power SCR 8/80A 400V
D1    CTB24L ?? C82 xx 004 ?? Dual Power diode
D2    small diode 1N4148
D3    small diode 1N4148
D4    small diode 1N4148

IC1   Motorola UC3843AN Current Mode Controller

L1    ferrite core
L2    ferrite toroid
L3    ferrite core

This was new in a IBM PC about 20 years ago but the design is still working very fine.

TO-220 Package

Q1, Q2 and D1 (TO-220) are on the heat sink as shown in the following picture.

Heat Sink and 3 TO-220 Packages

The whole power supply schematics can be seen in this picture.

STK-200 HRK PC Power Supply Schematics (around 1995)

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