This simple DC-DC converter can provide up to 24V from a 12V source.
It can be used to run radios, small lights, relays, horns and other 24V
accessories from a 12V vehicle with a maximum draw of about 800mA. It
can be used to charge one 12V battery from another, or step up the
voltage just enough to provide necessary overhead for a 12V linear
regulator. Using one op-amp as a squarewave oscillator to ring an
inductor and another op-amp in a feedback loop, it won”t drift around
under varying loads, providing a stable 24V source for many
applications. With a wide adjustment in output this circuit has many
|R1, R2, R3, R4, R8, R7||6||100K 1/4W Resistor|
|R5||1||470 Ohm 1/2W Resistor|
|R6||1||10K Linear Pot|
|C1||1||0.01uF Mylar Capacitor|
|C2||1||0.1uF Ceramic Disc Capacitor|
|C3||1||470uF 63V Electrolytic Capacitor|
|D1||1||1N4004 Rectifier Diode|
|D2||1||BY229-400 Fast Recovery Diode||See Notes|
|Q1||1||BC337 NPN Power Transistor|
|U1||1||LM358 Dual Op Amp IC|
|MISC||1||Board, Wire, Socket For U1, Case, Knob For R6, Heatsink for Q1|
- R6 sets the output voltage. This can be calculated by Vout = 12 x (R8/(R8+R7)) x (R6B/R6A).
- L1 is made by winding 60 turns of 0.63MM magnet wire on a toroidial core measuring 15MM (OD) by 8MM (ID) by 6MM (H).
- D2 can be any fast recovery diode rated at greater then 100V at 5A. It is very important that the diode be fast recovery and not a standard rectifier.
- Q1 will need a heatsink.