# How to limit current while almost keeping voltage same

I am supposed to design a power supply to a project. I have 3 alternative power supply designs for this purpose. However, one of them sucks huge current while giving enough current. My design is given below:

I have searched a lot to find a way to limit this current. I have found current limiter including 2 transistor and the power supply including current limiter is given below:

As it can be seen, Although stated as low voltage drop, just after the limiting block, voltage almost hit the ground. Please offer me a way to limit this current somehow by depending on the design, please. Thanks in advance.

• As this is your project, what alterations are you considering? – Solar Mike Jul 17 '19 at 18:56
• by the way, can you see my attached pictures? – Muhammed Selman Jul 17 '19 at 18:57
• Trace the possible paths through the two bridge rectifiers. There's a path through two diodes across the source. – Phil G Jul 17 '19 at 18:58
• Is the power source 26 V DC,as implied by the battery symbol, or 14 or 22 KHz AC as impiled by the text boxes. Can you show a schematic without all those text boxes - they cover important parts of the circuit. as Phil G says, it appears that D3 and D5 form a short circuit across the supply. – Peter Bennett Jul 17 '19 at 19:03
• if you limit the current, then the terminal voltage will drop to whatever is required to keep the current into the load constant. You can't limit current while maintaining voltage. – Neil_UK Jul 17 '19 at 19:25

You seem to be trying to make a split-rail PSU out of a 24 V DC supply.

Look at your first circuit. You have 24 V short-circuited by D5 (I think, because you've covered it with a label) and D3. If your supply is strong enough these will be destroyed very quickly.

Your second circuit is the same although you have attempted a current limiter so the diodes may be protected.

How to proceed:

1. Write a specification. This should include input voltage range, output voltages required, current required on each output.
2. Attempt a design. Try to lay it out so that current flows from top to bottom. That will affect the layout of your diodes in particular.
3. Eliminate unnecessary kinks and cross-overs in your schematic. Use GND symbols where possible to eliminate wires.
4. Review your design looking out for silly stuff (such as short circuits as described above).
5. Turn off the grid before taking screengrabs.
6. Update your question. Avoid phrases like "voltage almost hit the ground" and use phrases like "voltage dropped from 24.3 V to 1.4 V relative to ground".