PSUDII simulation vs reality

Navyblue · 22nd May 2012, 08:20 AM

I have a tube rectified LC-LC-LC power supply that I designed with PSUDII. I took care to use have enough resistance and large enough capacitor to avoid the initial voltage spike. Not only I do get the spike, I get a pretty big one (upto 180+V, takes a few seconds to stabilise to 100+V).

I was told that the initial spike can be an indication that the PSU would ring.

I wonder if it is normal? Or is there something wrong? The chokes I used are pretty cheap. And the tube rectifier heater is starved (5.4V instead of 6.3V) and probably because of that I also get quite a bit lower output than simulated.

DF96 · 22nd May 2012, 09:06 AM

PSUs with chokes can ring. Difficult to say more than that without a circuit diagram.

Zen Mod · 22nd May 2012, 09:54 AM

zip and attach PSUD file here

Navyblue · 22nd May 2012, 02:19 PM

Here it goes.

I put the first choke as 1083 ohms, it is actually 250 ohms with 833 ohms worth of resistor in series.

The last cap of 80uF is made up of 2x40uF in parallel.

DF96 · 22nd May 2012, 03:14 PM

Sorry, my PSUD2 won't open it.

Navyblue · 22nd May 2012, 03:37 PM

This is how it looks like.

SY · 22nd May 2012, 03:43 PM

So L1 really has that high of a DCR?

To check stability, use a CCS as the load, set to the expected current for the intended load. Then use the "step" option to have it step up or down by (say) 20% after 10 seconds or so. See what happens.

DF96 · 22nd May 2012, 03:57 PM

I suspect what is happening is that the LC filtering means that the initial choke input stage sees very little current draw at first, so its voltage shoots up. Once things stabilise it does what you expect. You won't see any spike on the output with PSUD2 because your load in the simulation draws current straight away. Plot V(C1) to see a spike (my prediction - I could be wrong).

AndrewT · 22nd May 2012, 04:19 PM

C1 and C2 and C3 ensure that the first L sees a substantial current load from start up.
That should prevent a spike due to the L not seeing a significant current load for choke input to operate as expected.

Navyblue · 22nd May 2012, 04:23 PM

Quote:

Originally Posted by SY

So L1 really has that high of a DCR?

To check stability, use a CCS as the load, set to the expected current for the intended load. Then use the "step" option to have it step up or down by (say) 20% after 10 seconds or so. See what happens.

Before L1 I put a bunch of resistors in series to cut down the voltage to where I need it, I lumped the total resistance together with L1.

The load is set as CCS. I tried stepping up or down, they look smooth, no spikes.

22nd May 2012, 08:20 AM	#1
Navyblue diyAudio Member Join Date: Mar 2012	PSUDII simulation vs reality I have a tube rectified LC-LC-LC power supply that I designed with PSUDII. I took care to use have enough resistance and large enough capacitor to avoid the initial voltage spike. Not only I do get the spike, I get a pretty big one (upto 180+V, takes a few seconds to stabilise to 100+V). I was told that the initial spike can be an indication that the PSU would ring. I wonder if it is normal? Or is there something wrong? The chokes I used are pretty cheap. And the tube rectifier heater is starved (5.4V instead of 6.3V) and probably because of that I also get quite a bit lower output than simulated.

22nd May 2012, 09:54 AM	#3
Zen Mod diyAudio Member Join Date: Jan 2003 Location: ancient Batsch , behind Iron Curtain	zip and attach PSUD file here __________________ my Papa is smarter than your Nelson ! tnx to clean thread ; Cook Book ; PSM LS Cook Book ; Baby Diyaudio FORUM ; Mighty ZM's Bloggg;I'm dumb

22nd May 2012, 03:43 PM	#7
SY diyAudio Moderator Join Date: Oct 2002 Location: Chicagoland Blog Entries: 1	So L1 really has that high of a DCR? To check stability, use a CCS as the load, set to the expected current for the intended load. Then use the "step" option to have it step up or down by (say) 20% after 10 seconds or so. See what happens. __________________ If there's a sucker born every minute, where do the rest of them come from?

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22nd May 2012, 09:06 AM	#2
DF96 diyAudio Member Join Date: May 2007	PSUs with chokes can ring. Difficult to say more than that without a circuit diagram.

22nd May 2012, 03:14 PM	#5
DF96 diyAudio Member Join Date: May 2007	Sorry, my PSUD2 won't open it.

22nd May 2012, 03:37 PM	#6
Navyblue diyAudio Member Join Date: Mar 2012	This is how it looks like.

22nd May 2012, 03:57 PM	#8
DF96 diyAudio Member Join Date: May 2007	I suspect what is happening is that the LC filtering means that the initial choke input stage sees very little current draw at first, so its voltage shoots up. Once things stabilise it does what you expect. You won't see any spike on the output with PSUD2 because your load in the simulation draws current straight away. Plot V(C1) to see a spike (my prediction - I could be wrong).

22nd May 2012, 04:19 PM	#9
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	C1 and C2 and C3 ensure that the first L sees a substantial current load from start up. That should prevent a spike due to the L not seeing a significant current load for choke input to operate as expected.

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