12V to 24V DC- DC Converter

This simple circuit is a DC-DC converter that converting up 12V source to a 24V. 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.

 The Schematic 12V to 24V DC- DC Converter

This DC-DC Converter 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 square wave 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.

Parts List
R1-R4,R7-R8 100K 1/4W Resistor
R5 470 Ohm 1/2W Resistor
R6 10K Linear Pot
C1 0.01uF Mylar Capacitor
C2 0.1uF Ceramic Disc Capacitor
C3 470uF 63V Electrolytic Capacitor
D1 1N4004 Rectifier Diode
D2 BY229-400 Fast Recovery Diode See Notes
Q1 BC337 NPN Power Transistor
U1 LM358 Dual Op Amp IC
L1 See Notes
MISC Board, Wire, Socket For U1, Case, Knob For R6, Heat sink for Q1

DC- DC Converter Notes
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 toroidal 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 heat sink.

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Variable DC Power Supply With LM317

This DC power supply circuit is adjustable using IC Voltage Regulator LM317. LM317 is a versatile and highly efficient 1.2-37V voltage regulator that can provide up to 1.5A of current with a large heat sink. It's ideal for just about any application. This was my first workbench power supply and I still use it.

Since LM317 is protected against short-circuit, no fuse is necessary. Thanks to automatic thermal shutdown, it will turn off if heating excessively. All in all, a very powerful (and affordable!) package, indeed.

Although voltage regulator LM317 is capable of delivering up to 37V, the DC power supply output circuit here is limited to 25V for the sake of safety and simplicity. Any higher output voltage would require additional components and a larger heat sink.

Make sure that the input voltage is at least a couple of Volts higher than the desired output. It's OK to use a trim-pot if you're building a fixed-voltage supply.

Problems:
Follow all the safety precautions when working with mains voltage. Insulate all connections on the transformer.

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6A, 5 Volt Power Supply

The standard variable voltage regulator type LM150 is fairly easily available, but at times its out, which is limited to about 3 amperes, may prove to e a limiting factor to its utility, nut the simple modification describe here allows the to be enhanced to about 6 amperes. The circuit has inbuilt safe area protection and thermal overload protection.The circuit has been tested for lone regulation of the order of about 0.01% volt and load regulation of about 0.1% volt.
The circuit works on principle similar to the compact 10A power supplies. The two LM150 regulators are wired in parallel mode with  IC3 which controls them. The output voltage is given by the relation
Vout=1,25x(1+R5/R4) volts. The input voltage may lie anywhere in the range of 12 to 30 volts.

The IC must be adequately heat sinked in order to obtain full output current all over the operative temperature range 

The circuit 6A, 5 volt Power Supply

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High Current Regulated Supply

The high current regulator below uses an additional winding or a separate transformer to supply power for the LM317 regulator so that the pass transistors can operate closer to saturation and improve efficiency. For good efficiency the voltage at the collectors of the two parallel 2N3055 pass transistors should be close to the output voltage. The LM317 requires a couple extra volts on the input side, plus the emitter/base drop of the 3055s, plus whatever is lost across the (0.1 ohm) equalizing resistors (1volt at 10 amps), so a separate transformer and rectifier/filter circuit is used that is a few volts higher than the output voltage. The LM317 will provide over 1 amp of current to drive the bases of the pass transistors and assumings a gain of 10 the combination should deliver 15 amps or more. The LM317 always operates with a voltage difference of 1.2 between the output terminal and adjustment terminal and requires a minimum load of 10mA, so a 75 ohm resistor was chosen which will draw (1.2/75 = 16mA). This same current flows through the emitter resistor of the 2N3904 which produces about a 1 volt drop across the 62 ohm resistor and 1.7 volts at the base. The output voltage is set with the voltage divider (1K/560) so that 1.7 volts is applied to the 3904 base when the output is 5 volts. For 13 volt operation, the 1K resistor could be adjusted to around 3.6K. The regulator has no output short circuit protection so the output probably should be fused.

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