0-30V 0-3A Latest Data Discussion

[zbb]

I thought I would outline the voltage spike problems with the PSU...........I spent a good while on this problem but as the supply spikes at switch on as well, and the PSU works very well in all other areas, I’m going to leave it, as is (no switch off clamp transistor) and look at a separate on off switch, perhaps using a FET. More later.

A solution that works guaranteed is reasonably simple: put a single throw switch between the point R8/R9/C4 and the ground tab of the voltage pot. Use this switch to easily switch the output on and off without switching the whole supply on or off. Make it a habit to have this switch in the output-off-position, switch closed, before you switch the supply on or off.

If you are adverse to having a second switch:
Did you try putting a capacitor parallel to R13? As the lower base resistor is very small, it should be a bigger one; a wild gues would be an elco of at least 47-100microFarad. That capacitor is charged by the rise of the positive supply rail and discharges over R14. If the capacitor is large enough to delay 1/50th of a second to hold Q1 open, the negative supply is about where it should be. In order to use much higher resistance values and have longer delays with a smaller capacitor, try replacing Q1 by a MOSfet.

 

[zbb]

I have to add a comment to the above: If at switch-on there is a delay because of the capacitor discharging from the full positive tension, say 36V, to less then Vbe, there will also be a very much smaller delay at switching off, the voltage rising from -1.3V to +Vbe. The latter delay is an order of magnitude smaller than the former, but still it means that the value of capacitor can not be made unlimitedly big.

 

[elboa8]

Hi I think that at some point you have to stop and say I'm happy with this as it is. Look at the 100's of threads on this project.
With all respect to the original design a lot of the problems is the use of a _ve supply on the current control IC. As it stands switching OFF by the DC switch before switching OFF my the AC switch does not of course give a spike. Also setting the voltage level only slightly above the current set value minimizes the spike. I did spent quite a bit of time playing around with cap values (not simulation) on a breadboard before building the supply. I guess at the end of the day this is a hobby. The reality is you could buy a better spec PSU from Ebay! But were is the fun in that. Also at the moment there are several different topics all on the same supply. It certainly got people interested. For me I think it's time to move onto something else. Regards

 

[elboa8]

I forgot. What time zone is this blog in? I live in France and it's hours apart from me.

 

[burrap]

Wouldn't elimination of the negative rail mean that we could get rid of the 10V zener as well?  Something like this?

View attachment 42333

I tried simulating this. Works beautifully. I think I had to switch the inputs U1 though. I have the simulation at work.

But in this design, Q1 is pointless though. So I will either remove it or modify the negative supply to work with Q1 only.

I think I'll go with the latter. Don't need a good neg supply since it's only purpose is to die at shutoff

I love getting rid of the neg supply in current limiting mode though. Otherwise I would feel the need to improve it.

I will also move most ground connections to go after the current sense resistor. As it is now the 6mA going from the reference zener to ground (and also other small currents) goes through the current sense resistor which I don't like.

Thanks for the idea!

When the load current is higher than the current regulator setting and the voltage is set high, the "on" voltage spike is caused by the time it takes for the negative supply to reach a low enough voltage (-1V?) for the current regulating opamp to pull down the voltage feeding the voltage output amplifier.

Here is my proposed fix: 

View attachment 42332

Do you still have this pic audioguru? I'd love to see it and the link doesn't work for me.

 

[audioguru2]

I cannot remember my fix for the "on" voltage spike.

If you remove the negative supply then you will not be able to limit shorted output current less than about 0.43A since the transistor that replaces the diode cannot go lower than its max saturated output of about 0.2V.

0.2V/0.47 ohms= 0.43A.

 

[burrap]

Oh. Ok. I thought your fix was for the peak that occurs when you are in current limit mode and turn the supply off (since the current limit function collapses faster than the output is pulled down.

Then it's ok. Turn on transients shouldn't be as tricky.

0.2 volt on the base of a 2n4401 shouldn't open it, so it should be ok.

 

[bemnet]

CID/CID+ certification is requirenment is high did some one knows how i can get certified in my home counrty?

 

[electron234]

Is it possible to charge 12V  18AH  battery with this Charger ? In past i have blown 0-30V / 0-3A LOADSTAR PSU.

Thanks Ahead

 

[audioguru2]

Is it possible to charge 12V  18AH  battery with this Charger ? In past i have blown 0-30V / 0-3A LOADSTAR PSU.

No, it is a power supply, not a charger.

 

[elisson]

Alguém tem o PCB e os dados mais recente por favor

Does anyone have the PCB and the latest data please