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POWERSUPPLY
Vehicle Adapterfor Notebook PCs19 volts from a car battery
Design by R. Badenhausen
Notebook PCs are great but stray too far from a source of power
and
its not long before low-battery warnings start to appear. Mains
adapters
come as standard but car adapters are expensive accessories.
Good
enough reason to get the soldering iron out!
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POWERSUPPLY
20
19
18
17
16
15
14
13
1210 11 12 13 14 15 16
010042 - 12
21
R14 [k]
outputvoltage
[V]
500
400
300
200
100
0uAC[mV]
Fi 2. Resistor R14 sets the output voltage.
COMPONENTS LIST
Resistors:
R1,R2 = 10kR3 = 560R4,R11,R12 = 3k3R5,R7,R8 = 1k5R6,R9 = 6k8R10
= 220, 1WR13 = 1k8R14 = 15kR15,R17 = 680R16 = 150, 5WR18 = 820
Capacitors:
C1 = 5nF6C2 = 2200F 16V axialC3 = 470F 63V axial *C4,C5 = 470F
16V radialC6 = 10F 16V
Semiconductors:
D1 = 1N4148D2,D3 = MBR745D4 = zener diode 6V8 0.4WD5 = zener
diode 12V 0.4WD6 = LED, high efficiencyIC1 = TLC272CPT1,T5 =
BC337-40T2 = BDX53B
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increased risk of accidental knocks
and bumps. Allow adequate spacingbetween the tracks running
along
the edge of the PCB and the inside of
the case and to be really sure it is a
good idea to fix thin insulating strips
of phenolic resin (Pertinax/Bakelite)
along the inside of the case.
The spacing under the PCB
should be no greater than 5 mm oth-
erwise the tops of the TO220 pack-ages and the inductor will be
too
close to the lid.
The input and output cabling can
be attached to the PCB using solder
pins. The cables should have a cross
sectional area in the order of 1.5 mm2
and strain relief grommets should be
fitted to the entrance and exit holes
in the case. It is better to use theadapter in unfused cigarette
lighter
sockets because the fuse gives an
additional voltage drop at the input
to the adapter, better still fit a good
quality accessory socket on the dash-
board for connection of the adapter.
(010042-1)
POWERSUPPLY
010042-1
(C)ELEKTOR
1
2
C
1
C2
C3
C4
C5
C6
D1
D
2
D3
D4
D5
D6
F1
H1
H2
H3
H4
IC1
L1
R1
R2
R3
R4
R5
R6
R7
R8
R9
R10
R11
R12
R13
R14
R15
R16
R17R18
T1
T2
T3
T4
T5
4A/T
0+
0 +
01004
2-1
010042-1
(C)ELEKTOR
Figure 5. The PCB with two small heatsinks (board not available
ready-made).
