Duncan PSUII question

[Brit01]

Quick psu2 question.

Can I use the software to simulate a 6V rectification using a SS bridge? I can't seem to get it to work for 6 or 12 V supply.

[Sheldon]

It works fine for this. What component values did you use. Did you change the transformer resistance to something realistic for low voltage/high current?

Sheldon

[SY]

Works fine here for 12V secondary, 6R source resistance, 100R load, 1N5400 rectifiers in a bridge, 2200uF filter cap. Are you using "high accuracy?"

[Brit01]

Maybe I'm way off track here.

If I want to use a constant current of 750mA for a heater?

[SY]

Here's a sample; make sure that you have the transformer source resistance set appropriately (3R in this example):

[Brit01]

If I use 6V-2R, 1N5400's, 2200u filtering cap and a constant current of 750mA all I get is huge ripple between 0.5 and 4V.

Also I expected the voltage to be higher due to the rectification.

I'm a little confused.

[Sheldon]

Originally posted by Brit01
Maybe I'm way off track here.

If I want to use a constant current of 750mA for a heater?

PSUD just models basic RC and LC circuits. I assume that you will use a voltage regulator or current regulator after the basic supply.

For modeling the RC part of the supply, yes you can use a 750mA current source as proxy for the current draw of the filament. Just adjust your supply parameters so that it delivers the voltage you want at that current level.

Better yet, tell us what you are planning and we can offer specific help.

Sheldon

[SY]

Originally posted by Brit01
If I use 6V-2R, 1N5400's, 2200u filtering cap and a constant current of 750mA all I get is huge ripple between 0.5 and 4V.

Also I expected the voltage to be higher due to the rectification.

I'm a little confused.

Why? That sounds about correct. You'll drop 1.5 volts from the transformer, another 1.5 volts from the diodes. Doesn't leave much! For that current draw, you'll need a lot more filtering to drop the ripple. If you really want it quiet, you'll need more transformer voltage, more filtering, and possibly some active regulation.

[Sheldon]

Originally posted by Sheldon


PSUD just models basic RC and LC circuits. I assume that you will use a voltage regulator or current regulator after the basic supply.

For modeling the RC part of the supply, yes you can use a 750mA current source as proxy for the current draw of the filament. Just adjust your supply parameters so that it delivers the voltage you want at that current level.

Better yet, tell us what you are planning and we can offer specific help.

Sheldon

I wrote the above before I saw your stats.

Yes, as SY said, those values are correct. You need a lot more capacitance. Say 20 time what you have. I'd use something like 20,000uF, then 0.1R, then 20,000uf. If you don't plan active regulation, you will need more RC sections.

To pick the correct transformer, go to the transformer dialog box and start playing with variables. Click on the "RMS V" button and experiment. I'd suggest using a 2A rated transformer. The standard 5% voltage regulation is about right. Then plug in different values for the nominal voltage rating, until you get the voltage output you want.

Sheldon

[Brit01]

Thanks guys.

Thought this would be easy.

Have always used AC for heaters. I wanted to try simulating rectification for my 6.3V and 12.6V trannies to drive the heaters with DC.