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Design ideas for a low-count part, low power isolated DC-DC power supply?
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SiliconWizard:

--- Quote from: Wolfgang on November 07, 2018, 10:25:38 pm ---Sync rectification could help, thats correct. There was some IC that did it very elegantly LT4320 but this does it to 600Hz only.
Maybe there is a faster part just as simple ?

--- End quote ---

https://www.infineon.com/cms/en/product/power/ac-dc-power-conversion/ac-dc-pwm-pfc-controller/synchronous-rectification-ics/
(Minimum working voltage will not fit all applications though, but it's a lot lower than for the LT4320.)
Some interesting stuff: https://www.monolithicpower.com/en/products/ac-dc-power-conversion/synchronous-rectifiers.html
IDEngineer:

--- Quote from: SiliconWizard on November 06, 2018, 10:08:53 pm ---they are pretty noisy (can make EMC testing fail even when you think you have routed them properly - they need extra care).
--- End quote ---

"Pretty noisy" doesn't begin to describe those nasty little transmitters. I wasted a couple of weeks once trying to quiet them down, both radiated and conducted. In some cases the PRIMARY is noisier than the secondary, corrupting the incoming supply. TI devotes many pages in their appnotes trying to put RFI/EMI lipstick on these pigs... I tried all of their "solutions" and none was even barely acceptable. I'd be embarrassed to have my name associated with something that noisy.

As I've noted elsewhere in these forums, also watch out for isolation capacitance. Think of it as a qualitative measurement of the coupling across the supposed "isolation" barrier. It's generally ghastly, with medical-rated modules being modestly better for horrific increases in price. Note that being expressed in terms of capacitance means the coupling is frequency dependent... anything high frequency on one side is cheerfully conveyed right through the module to the other side.

I'll never touch those modules again if I can help it. I have lots of samples from many suppliers here, in various voltages and configurations, and hope I never have to work with them again. My recommendation: Stay far, far away unless you're building something like Widlar's Hassler.
Wolfgang:
The rant is always the same; People want chips in a microscopic package (meaning low dissipation capabilities). In the sake of energy efficiency, switching times are reduced as much as they can, creating a UWB noise level all around the circuit. Then, some cosmetic RFI measures try to amend things until it is tolerable.

If you want quiet circuits, stay away from fast components. Efficiency will suffer somewhat, but RFI problems are a lot less.

There are some Jim Williams appnotes where switching speed was deliberately reduced to keep RFI problems at bay.
SiliconWizard:

--- Quote from: IDEngineer on November 07, 2018, 10:38:14 pm ---
--- Quote from: SiliconWizard on November 06, 2018, 10:08:53 pm ---they are pretty noisy (can make EMC testing fail even when you think you have routed them properly - they need extra care).
--- End quote ---

"Pretty noisy" doesn't begin to describe those nasty little transmitters. I wasted a couple of weeks once trying to quiet them down,
(...)
I'll never touch those modules again if I can help it. I have lots of samples from many suppliers here, in various voltages and configurations, and hope I never have to work with them again. My recommendation: Stay far, far away unless you're building something like Widlar's Hassler.

--- End quote ---

Yep, that partly explains why I'm looking for alternatives, even if they have to be made of discrete parts.
Apart from the noise issues, the startup can be a huge problem as well especially if you're powering them from switching regulators. Had a few headaches. Lastly, I also noticed that they tended to run very warm even at minimal load.
ANTALIFE:


https://power.murata.com/data/power/ncl/kdc_nxe1.pdf
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