12V To 24V DC-DC Converter Circuit

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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

Parts

Part	Total Qty.	Description	Substitutions
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

Notes

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.

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Comments

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farrukh 12V To 24V DC-DC Converter Saturday, January 02, 2010 7:52:22 PM

this transistor is not the correct choice.. when i tried it got burned D313 npn transistor effective enough to give 22.3 voltage at the node with fr diode 1n5819..... it really works

anonymous 12V To 24V DC-DC Converter Saturday, December 26, 2009 7:57:55 AM

DC-DC converters are important in portable electronic devices such as cellular phones and laptop computers, which are supplied with power from batteries primarily. from -svtelindia

anonymous 12V To 24V DC-DC Converter Tuesday, December 22, 2009 2:52:11 PM

I couldn't get this circuit to work and have checked my worl several times, is this schematic correct?

smazzarello 12V To 24V DC-DC Converter Wednesday, December 02, 2009 1:41:54 PM

How many current can supply this device?

Dnstje 12V To 24V DC-DC Converter Saturday, November 28, 2009 3:13:56 PM

Hmm, The emitter from the transistor(q1) should be on ground right?
(Editor's notes: Yes. I will correct the schematic soon. )

skywriter 12V To 24V DC-DC Converter Thursday, November 19, 2009 1:02:12 AM

It seems the circuit above is wrong. Q1 would never open because there is no difference of potentials between base and emitter

anonymous 12V To 24V DC-DC Converter Sunday, October 18, 2009 6:20:00 PM

Any specs on the inductor? For example if I wanted to buy one instead of making one? Thanks

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farrukh	12V To 24V DC-DC Converter	Saturday, January 02, 2010 7:52:22 PM
this transistor is not the correct choice.. when i tried it got burned D313 npn transistor effective enough to give 22.3 voltage at the node with fr diode 1n5819..... it really works
anonymous	12V To 24V DC-DC Converter	Saturday, December 26, 2009 7:57:55 AM
DC-DC converters are important in portable electronic devices such as cellular phones and laptop computers, which are supplied with power from batteries primarily. from -svtelindia
anonymous	12V To 24V DC-DC Converter	Tuesday, December 22, 2009 2:52:11 PM
I couldn't get this circuit to work and have checked my worl several times, is this schematic correct?
smazzarello	12V To 24V DC-DC Converter	Wednesday, December 02, 2009 1:41:54 PM
How many current can supply this device?
Dnstje	12V To 24V DC-DC Converter	Saturday, November 28, 2009 3:13:56 PM
Hmm, The emitter from the transistor(q1) should be on ground right? (Editor's notes: Yes. I will correct the schematic soon. )
skywriter	12V To 24V DC-DC Converter	Thursday, November 19, 2009 1:02:12 AM
It seems the circuit above is wrong. Q1 would never open because there is no difference of potentials between base and emitter
anonymous	12V To 24V DC-DC Converter	Sunday, October 18, 2009 6:20:00 PM
Any specs on the inductor? For example if I wanted to buy one instead of making one? Thanks