• These commercial threads are for private transactions. diyAudio.com provides these forums for the convenience of our members, but makes no warranty nor assumes any responsibility. We do not vet any members, use of this facility is at your own risk. Customers can post any issues in those threads as long as it is done in a civil manner. All diyAudio rules about conduct apply and will be enforced.

Scalable PSU/regulator GB

Status
Not open for further replies.
Jump to Latest
#421
Hi Jens
the design able to withstand a short circuit by simply not letting any power be dissipated in the pass devise during a short circuited output situation
Click to expand...
that applies at start up IF Vin is kept below Vstart.
But, I think that, once Vin exceeds Vstart the pass device closes and supplies current to the shorted output. Am I correct?
The smoothed voltage will be high initially when the pass device is open and the extra voltage available during pre-start is what causes the circuit to kick itself into passing then the extra cap voltage will ensure an extra large current pulse into the shorted output.



If the output short is applied after the circuit has successfully started the pass device will be destroyed anyway. Post414 confirms this senario.

If both the above senarios are correct then your simulation is misleading you regarding the short circuit tolerance of the high Vstart topology.
 
#422
AndrewT said:
Hi Jens that applies at start up IF Vin is kept below Vstart.
But, I think that, once Vin exceeds Vstart the pass device closes and supplies current to the shorted output. Am I correct?
Click to expand...

No (Not for the low voltage version, I have not tested the high voltage version yet as you have not posted a BOM)

AndrewT said:
If the output short is applied after the circuit has successfully started the pass device will be destroyed anyway. Post414 confirms this senario..
Click to expand...

For the high voltage version it might happen I have not tested it yet - BOM still missing, the 15V version works fine!

AndrewT said:
If both the above senarios are correct then your simulation is misleading you regarding the short circuit tolerance of the high Vstart topology.
Click to expand...

Thats funny, I simulated and measured the same results..... go figure.

Please post your BOM so I have a chance to actually find out what your are doing, and what your circuit is doing.

\Jens
 
#423
A little late, but I have posted a PSU construction guide on http://mysite.verizon.net/vze3xvxs/audio/ (or the www button below)

There is also a Bill of Materials for the standard version and a BOM for my 65 Volt version as well as an Excel spreadsheet for calculating component values (previously posted here).

I'm working on the active crossover page, but for now it contains the construction guide and filter calculation spreadsheet.

I still have boards and parts kits if anyone needs them - I bought extras for latecomers and then Advanced went over by 21 boards. I am out of transformers and heat sinks, but I believe Gengis has a few hundred more sinks.
 
#424
Bob. wouldn't it be easier to use BC639/BC640 instead of the MPSA's.They are rated at 100V if i'm correct and the current gain should be a lot higher giving better performance. Also the pin layout should be the same as the low voltage version.
As a bonus they are much easier to come by here in europe.


Kees.
 
#425
Kees,

That seems like a reasonable choice. Hfe numbers seem similar, Fairchild lists the Vceo at 80 V. Ft is 100 MHz for the BCs while the MPSA are a bit slower at 50 MHz. For those interested in the US, Mouser carries BC639/BC640.

I have a couple hundred of the MPSAs handy, so I used them. The circuit works with the MPSAs at 65V, at least on this side of the pond. If someone wants to test with the BC639/640, please let us know how it works out.

Bob
 
#429
== PSU Round 2 Underway - closing date 18 August ==

To simplify my record keeping and try to improve accuracy, I've set up a PayPal shopping cart for purchase of boards and kits. You can use a credit card even if you have no PayPal account. If you don't have a credit card, email me to make arrangements.

Go to http://mysite.verizon.net/vze3xvxs/audio/id19.html click on "Purchase Boards and Parts". Click on the "add to cart" buttons as desired. You can increase the quantities in the cart.

Be sure to select a shipping option. In the US, most orders will fit in the Priority Mail envelope. Outside the US, I can fit 10 boards or 6 boards and a power supply kit into a small GPM envelope. Small quantities of 100 nf will fit as well. If you have more than one PSU kit, you'll need the large envelope for up to 4 psu kits. If in doubt, email me and I'll figure out shipping cost.

Pricing:

Filter Boards $5
PSU Boards $6.25
PSU Kit $28 (includes board, parts and heat sinks)
I also will offer 470 uF Panasonic FCs for the filter boards (2 required per), 100 nF/100V Epcos Film caps for decoupling, 1500 uF 35V Panasonic FCs and BC546C/BC556C.
 
#430
Dear Bob and Jens,

I looked through this entire thread, and also looked at the PSU 2 details on delta-audio.com, but couldn't find the Eagle .sch and .brd files. Do you think you would like to make those available? I might like to take a look at them, maybe modify them a bit here and there to suit local component availability, and make a few boards?

If these files are not meant for public release, please ignore this post. 🙂

Thanks for the great design.

PS: Is there any difference between the PSU 2 on Delta-audio and the PSU schematic you are talking about here?
 
#431
Jens has the Eagle files. The PSU 2 is what we ended up building, there were a few iterations along the way.

Pretty much everything should be available worldwide, the BC546C and BC556C are sometimes a problem, but I have plenty if you want to do it piecemeal. LM4040's can be expensive in some parts of the world, but you could also use a zener, since there is a pad for that already. Or you could buy the kit with everything you'd need. Click on my www button before August 18th.
 
#432
start up problem ? PLEASE HELP

I think I'm having a start up problem on th negative side of the PSU.
On the positive part the output voltage is correct (15.1 V), on the negative side it depends on I don't know what. Somteimes I get 15 V somtimes only 2 V.
With the small load of one 2134 it doesn't start, but disconnecting the negative supply to the opamp immediately turns on the LED and gives 15 V. It stays on when reconnecting the opamp.
Another curious phenomenon is that it seems to turn on a few seconds after disconnecting the 220 V AC.

DC voltage after the bridge seems OK (19.6 V DC on + and - sides) but the voltage across R10 is far too low (only .6 V; across R3 it's 10 V).
I had a look into the discussion in this tread on start up problems but couldn't make tea of it. I'm far too much of a layman.
Can anybody tell me what to do?

Thanks
Dick.
 
#434
No, I can't increase the voltage like that but I can of course choose a lower output voltage like e.g. 13 V
I suppose this would also solve the problem without causing too much of a problem in the filter.

I'll try that.
Thanks a lot, Bob.

Dick.
 
#435
Hi Bob & Dick,
lowering the output voltage will not solve the start up problem.
It has been documented at length that this circuit has an inherent problem at start up. See Jens' plots of simulated in/out voltage at start up.
Careful choice of component values and types seems to be the only partial solution. Optimising for better/reliable start up compromises the output noise and ripple. The corolary is also true, optimising for good noise and ripple rejection exagerates the start up problem.

Buying the kit of components from Bob seems to avoid the problems.
 
#437
BobEllis said:
Jens has the Eagle files.
Should I write an email to him?

Pretty much everything should be available worldwide, the BC546C and BC556C are sometimes a problem, but I have plenty if you want to do it piecemeal. LM4040's can be expensive in some parts of the world, but you could also use a zener, since there is a pad for that already. Or you could buy the kit with everything you'd need. Click on my www button before August 18th.
Click to expand...
I won't go with the kit... I'll probably need this PSU much later, so it's better to just study it now and arrange for some of the parts. Thanks for your offer though. 🙂 Will an ordinary zener add noise to the output? The BC transistors shouldn't be any problem in India... we are veteran BC country. 🙂
Click to expand...
Click to expand...
 
#438
A zener will probably add a bit of noise. Another low noise but expensive option would be to use an LM329 as the reference if you cannot find LM4040s. This would require changing the voltage divider values, but is rather straightforward.
 
Status
Not open for further replies.
Top Bottom