12V To 24V DC-DC Converter Circuit

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


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


Total Qty.
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
L1 1 See Notes
MISC 1 Board, 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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