I have looked all over for a chip or a schematic that allows me to convert 12v to 6v and I can't find anything. I can find 12v to 5v with no problem at all but I need 6v. Would a simple voltage divider work? The load changes so I don't think a voltage divider will work but I am not sure. The current will be up to 3A at some times but as low as 500mA at other times. Thanks.
David
Look at the LM317 regulator with a pass transistor.
The 317 will do up to 1.5 amps (with heatsink).
Just make sure the input voltage is at least a couple of volts higher than the desired output.
The LM2587 is an adjustable, up to 5 amp switching regulator chip.
Do you mean 12V like 12.00VDC? Or do you mean 12V like plug it into a car? If it's the latter, you have a LOT more things to worry about. mike
The LM317, LM350 and LM338 and two resistors will all do that. The chips (on heat sinks) can handle up to 1.5 amps, 3 amps and 6 amps, respectively.
The LM317 with a PNP pass transistor and a few resistors is probably your best choice. Simpler, but more costly, would be the LM250 or LM338. Here's the circuit with the pass xsistor: PNP 2N2955 e c
+12 -----+------ ---------------------+ | \\ / | 3[R1] ----- | | | ------------ | +--------+------|in LM317 out|---+--- Vout +6 | ref | | ------------ [R2]240 | | +----------+ | [R3] 910 | GndThere will be a voltage drop across R1 (3 ohms) as the LM317 provides current to the load. The more current that is drawn, the greater the voltage. The effect is to cause the transistor to conduct when the current drawn is about 200 mA, and the more current that is drawn, the harder the transistor conducts. R2 (240 ohms) and R3 (910 ohms) form a voltage divider that "programs" the LM317 to produce very close to
6 volts. If you need it to be precisely 6.00 volts, substitute a 10 turn, 1000 ohm pot for R3 and adjust it to the exact voltage.Consult the datasheet for the LM117/LM317 for more detail.
Ed
Unless you want and know how to dissipate appropriately 18 W, you must go for a switching converter. Forget about linear regulators.
Hi,
You may not want to do this but by using two IR2110'S and 4 fets and a toroid with two wires bifilar wound . Connected as you would a push pull, center tapped 6 to 12 volt converter and replace the two diodes with two fets. This must be driven with a 40 to 50 % on each half cycle. You now have a synchronous rectified voltage doubler that is bi-directional and if a 12v charger is applied to the 12 volt output you will also charge the 6 volt battery.
I have built such a device for a friend to add a 12v battery to a triumph motorcycle because the 6v batteries are no longer made. The 6v charger charges the 12v battery and the electrical system is all 6v. Above I used the 555 timer and 4013 to divide by two and give a symmetrical output.
Ray
You could do a little experimenting with a mobile phone car charger - just change the output voltage divider resisters and bobs your auntie
David - who f> I have looked all over for a chip or a schematic that allows me to
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