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# Need a split power supply (+ and -)

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#### TheDude1888

##### New Member
Ok, I need jus a simple power supply that can output about 24 volts for both + and - volts. I can get the positive easily but im getting confused on the negative. I can use a LM317 regulator for the postive output but what can i use for a negative output? Also, does the negative voltage regulator need to have a negative voltage input? If yes, then how can i get the rectifier to output only the negative part of the sine wave of the AC signal? Is it jus flipping the bridge outputs? I'm jus confused on the whole negative side.

The bridge rectifier with the leads would work by itself. However if you take two bridge rectifiers from the same supply and tried to have a
+ and - supply I think you would have a current path between the two rectifiers. Try drawing out the circuit and see. A charge pump is an easy way to generate a negative supply for low current applications. Another method uses a voltage of half your supply as a ground. This makes V+ your positive supply and ground your negative supply. Be sure to buffer your V+/2 ground to void weird effects. Both of these are good only for low current draw on the negative supply.

To have a true + and - supply you need to have outputs that are isolated from each other (i.e. no common ground). Two transformer windings or two separate transformers will acomplish this.

Brent

Would something like this work, I need +5V,0,-5V, 300mA?
What would complete the circuit to make it even better?TIA.

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What is the current you are looking at?
Do you want a fixed output of 24V or vairable up to 24V?
LM317 is a variable positive voltage regulator.
If you want a fixed output you may use 7824 (positive) and 7924 (negative) voltage regulators in the ckt suggested by GTO. In that case the power transformer should be capable of supplying the required output
(current & voltage). The regulators needs minimum input voltage of 27V to sustain stabilistion.

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