Feb 19, 2013


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 uses. 
Schematic for the 12 To 24V DC-DC Converter circuit



Total Qty.
R1, R2, R3, R4, R8, R76100K 1/4W Resistor
R51470 Ohm 1/2W Resistor
R6110K Linear Pot
C110.01uF Mylar Capacitor
C210.1uF Ceramic Disc Capacitor
C31470uF 63V Electrolytic Capacitor
D111N4004 Rectifier Diode
D21BY229-400 Fast Recovery DiodeSee Notes
Q11BC337 NPN Power Transistor
U11LM358 Dual Op Amp IC
L11See Notes
MISC1Board, Wire, Socket For U1, Case, Knob For R6, Heatsink for Q1


  1. R6 sets the output voltage. This can be calculated by Vout = 12 x (R8/(R8+R7)) x (R6B/R6A).
  2. 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).
  3. 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.
  4. Q1 will need a heatsink.

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