48v power supply design questions

[c12mech]

I am working on a hybrid amp that requires a 48v 350ma power supply. I have a 24v 1.5a transformer that I would like to use. I'm just having trouble getting from 24v to 48v. Power supply designs are my week point. I'm learning as I go. Thanks for any help.

Bryant

[mickeymoose]

Use one end of the secondary as common. On the other end of the winding connect two diodes, one positive out, one negative out. Two suitable capacitors. There you go.

[AndrewT]

that voltage doubler circuit he's suggested is not a good idea for a high current supply. They work well at low currents but not at 350mA.

The 24Vac with a voltage doubler will give almost 70Vdc on very light load and as the load increases the ripple becomes enormous causing the average voltage to fall.

[c12mech]

Most of the designs that I have seen are the voltage doubler type and as you say the ripple makes it almost useless at that point. I found a 48v 3a transformer but am unsure how to get the amps down to the level I need. I know it's just a matter of adding resistors and capacitors but in what order and where. Right now all of those formulas I had memorized are just gone.

[mickeymoose]

I did not suggest a voltage doubler but a Delon (bridge) circuit.

[AndrewT]

Originally Posted by mickeymoose

I did not suggest a voltage doubler but a Delon (bridge) circuit.

Hi,
it is the same as a voltage doubler, using diodes and capacitors to double the voltage.
If the correct name for the circuit is "Delon" then that is something else I will try to remember.

[AndrewT]

Originally Posted by c12mech

...... I found a 48v 3a transformer but am unsure how to get the amps down to the level I need.

the circuit/load will draw as much current as it needs. Do not try to reduce the current, simply satisfy the demand.

A 48Vac 3Aac will give you 65 to 75Vdc and continuous output of 750mA and stay cool.

If you want 48Vdc you need a 33Vac to 35Vac transformer.

[star882]

Use a boost PFC converter.

[stratus46]

Originally Posted by c12mech

I am working on a hybrid amp that requires a 48v 350ma power supply. I have a 24v 1.5a transformer that I would like to use. I'm just having trouble getting from 24v to 48v. Power supply designs are my week point. I'm learning as I go. Thanks for any help.

Bryant

So go to AnTek and buy the right transformer for $11 or $13.

G²

[paulb]

I think Andrew's replies have been the only useful ones so far.
I'm all about trying to use parts on hand. You could use your 48VAC transformer and a simple transistor regulator to drop the ~70VDC unregulated to 48VDC. You'll need a fair heatsink on the transistor, it would be dissipating about (70-48)V * 350 mA = 7.7W.
Here's an example:
zener regulated power supply