In-Car SMPSU

The OSCAR Stand-Alone MP3 Player described in last year’s September issue appears to be very popular with our readers. So popular in fact, that a large number would also like to use it in their car, boat or caravan. Using the DC/DC-converter described here will make that easier, from the power supply perspective at least.We really have ourselves to blame for this. In the first instalment of the series of articles describing the OSCAR, we carelessly let it slip that it would be advisable to use a special DC/DC converter to power this MP3-CD-player for mobile use. As a result, one can promptly expect the question ‘when are you publishing such a converter?’ Consequently, we immediately got to work and developed one. The end result is described below. It turns out that the required electronics is actually quite reasonable.

Resistors:
R1,R2 = 2kOhm 2
R3 = 2kOhm 7
R4,R5 = 0.1 Ohm 5W
R6 = 470Ohm
R7 = 4kOhm 7
R8 = 1kOhm 8
R9,R10,R13 = 1kOhm 
R11,R12 = 47Ohm
R14 = 249Ohm
R15 = 10kOhm 
R16 = 8kOhm 2
P1 = 250 Ohm preset H
P2 = 5kOhm preset H
Capacitors:
C1,C4,C5,C10,C12,C13 = 100nF ceramic
C2,C3 = 470µF 25V radial
C6,C7,C8 = 100µF 25V radial
C9 = 1000µF 40V radial
C11 = 15nF
C14 = 220µF 25V radial
Inductors:
L1,L3 = 100µH 5A, e.g., SFT12-50 (TDK)
L2 = ferrite bead (see text)
Semiconductors:
D1 = MBR745
D2 = zener diode 5.1V, 0.5W
D3 = LED, flat, red
T1 = 2SJ334 (Toshiba) 
T2 = BC557B
T3,T5,T6,T7 = BC547B
T4 = BF245A
IC1 = LT1074CT (Linear Technology)
Miscellaneous:
K1,K2,K3 = 2-way PCB terminal block, lead pitch 5mm
F1,F2 = fuse, 2A, with holder and cap for PCB mounting
PCB, order code 000193-1