Thinking of using one of my many old laptop switchers in leu of a transformer for the input to a very good linear regulator to feed a DAC. Wondering how much capacitance switchers can handle without stability or surge failure.
Guessing they should handle a couple hundred mic, but probably not more.
Cheaper than a transformer and large filter as I have them.
Guessing they should handle a couple hundred mic, but probably not more.
Cheaper than a transformer and large filter as I have them.
Another problem with CRC filter after the switcher is that C (normally electrolytics in hundred microfara range) loses its effective capacitance when going to 500kHz-1MHz and higher frequencies. This make your CRC useless for filtering high frequency noise anyway.
I think if your DAC does not consume much power, you should consider TPS7A470x regulator family. Its bandwidth extends to 10 MHz, so it is useful to filter the high frequency noise from the laptop switcher.
I think if your DAC does not consume much power, you should consider TPS7A470x regulator family. Its bandwidth extends to 10 MHz, so it is useful to filter the high frequency noise from the laptop switcher.
Take a look at this thread:
PO89ZB , an inline DC filter for SMPS wall warts . Preamps, HPA, Korg NuTube, etc
PO89ZB , an inline DC filter for SMPS wall warts . Preamps, HPA, Korg NuTube, etc
Suggest you track down Mark Johnson's thread somewhere herein -- it goes by a 4-letter acronym (that of course I can't remember 
) .. Wish I could give you a link, but I've struck out looking for it a couple of times, now. It's designed specifically for this situation, should remedy all of your concerns, and he's giving away the engineering, including the Gerbers! Thanks Mark.
Cheers
edit: Oops -- shouldn't have breezed over a few posts: jackinnj already had it -- "PO89ZB".
) .. Wish I could give you a link, but I've struck out looking for it a couple of times, now. It's designed specifically for this situation, should remedy all of your concerns, and he's giving away the engineering, including the Gerbers! Thanks Mark.Cheers
edit: Oops -- shouldn't have breezed over a few posts: jackinnj already had it -- "PO89ZB".
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No. This is a DIY site after all...
In fact, you'll probably need to get a batch of PCBs made yourself, but that's super easy and Mark gives all that information in the documentation. I use JLPCB, it's really, really easy.
Once you have a batch, sell off all the ones you won't use to people who are interested, they will be happily and quickly snapped up by other members.
In fact, you'll probably need to get a batch of PCBs made yourself, but that's super easy and Mark gives all that information in the documentation. I use JLPCB, it's really, really easy.
Once you have a batch, sell off all the ones you won't use to people who are interested, they will be happily and quickly snapped up by other members.
Well, for my crossovers, I took a laptop 24V supply, followed it with a pair of 4700u separated by 10 Ohms into the crossovers which have an on-board 3 pin something. Zero low frequency garbage and by my scope, more noise out of the on-board than the input, but we are talking in excess of 120 dB down. Only pull 200mA for the boards. I hear nothing an inch away from the speakers.
Been playing with this. Gaining respect for SMPS. My particular application has some issues not quite normal. It is for my crossover boards and powering their output mute relay. I need the control circuit to be faster than the boards artificial ground collapse (and huge thump)
So I figured, just toss a big cap before the boards, isolation diode and tap my control board before this. Easy, but inrush for the cap is a big concern. Transformers and diodes are easy. A 30A spike is nothing. But not sure that is good for the SMPS. So I added a 4 Ohm resistor which according to Spice ( I don't have a storage scope) limited it to 3A. It is a 1A supply. Testing today to see if the relay is faster. It does measure pretty clean on RightMark.
As I of course have no specs on an old HP printer power supply, anyone have any knowledge of SMPS ability to handle capacitive loades?
So I figured, just toss a big cap before the boards, isolation diode and tap my control board before this. Easy, but inrush for the cap is a big concern. Transformers and diodes are easy. A 30A spike is nothing. But not sure that is good for the SMPS. So I added a 4 Ohm resistor which according to Spice ( I don't have a storage scope) limited it to 3A. It is a 1A supply. Testing today to see if the relay is faster. It does measure pretty clean on RightMark.
As I of course have no specs on an old HP printer power supply, anyone have any knowledge of SMPS ability to handle capacitive loades?
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