Article
Symmetrical supply in cars
There is a problem if you want to use a car battery to power a
circuit which requires a symmetrical supply voltage. Having
abandoned the idea of mounting a second battery in your car
for that purpose, take a serious look at the circuit discussed
here. It converts the car battery voltage into symmetrical ±12 V
or even ±15 V rails. Since the converter is able to supply a
continuous output current of about 0.5 A, and a peak current
of up to 1 A, it is eminently suited to powering control
amplifiers and small power amplifiers.
Component list
Resistors:
R1;R4 = 1kΩ
R2 = 2kΩ2 2W
R3 = 10kΩ
Capacitors:
C1;C9;C10;C12;C14;C15;C17 = 220µF
25V radial
C2;C5;C8;C11;C13;C16 = 100nF
C3;C4 = 100IJF 25V radial
C6 = 1µF MKT
C7 = 220nF
Inductors:
L1;L2;L3 = SFT10-30 or SFT1030
(40µH)(TDK)
Tr1 = SFT12-50 or SFT1240 (see text)
Semiconductors:
D1;D2;D3 = BYW29-100
IC1 = LT1070 (Linear Technology)
Miscellaneous:
K1 = 2-way PCB terminal block.
K2 = 3-way PCB terminal block.
F1 = fuse 3A (slow) w. PCB mount holder.
Metal case, e.g., Hammond 1590S, 110x82x44mm.
Insulation set (washer and bush) for IC1, D2, D3.
R1;R4 = 1kΩ
R2 = 2kΩ2 2W
R3 = 10kΩ
Capacitors:
C1;C9;C10;C12;C14;C15;C17 = 220µF
25V radial
C2;C5;C8;C11;C13;C16 = 100nF
C3;C4 = 100IJF 25V radial
C6 = 1µF MKT
C7 = 220nF
Inductors:
L1;L2;L3 = SFT10-30 or SFT1030
(40µH)(TDK)
Tr1 = SFT12-50 or SFT1240 (see text)
Semiconductors:
D1;D2;D3 = BYW29-100
IC1 = LT1070 (Linear Technology)
Miscellaneous:
K1 = 2-way PCB terminal block.
K2 = 3-way PCB terminal block.
F1 = fuse 3A (slow) w. PCB mount holder.
Metal case, e.g., Hammond 1590S, 110x82x44mm.
Insulation set (washer and bush) for IC1, D2, D3.
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