DC DC Step Up/Down - How it Works?

[Bo Deadly]

Maybe, let's choose then a smps chip that is already produced and available in big quantities.

The interface that is interchangeable is not specific ICs or transformers or whatever parts. It should simply be viewed as a module that accepts 12V+ DC in and produces isolated output voltages with whatever power requirements. So just determine your voltage and power requirements, pick an IC (if it's a common IC then great), make a board and have fun doing it. Maybe after a while making an SMPS with whatever voltages / power will be "A Thing" and designs will evolve and we'll all benefit from it. Right now people are stacking multiple SMPS to make different voltages. That works but it's not ideal. Personally I have no reservations putting a beige plastic LED supply in my fancy audio project. If it works, it works. But some people might really like something that is specifically designed for audio with adjustable rails and integrated CLC and capacitance multipliers are what-have-you. That's what DIY is all about.

 

[trobbins]

I've had fun DIYing a variety of small ebay switchmode modules.  Typically all the parts and the circuit have to be identified, and then choices made as to what may need to be changed or augmented.  That can be a fleeting situation if the module is not available after a year or two, or you only purchased one or two modules at the start. 

As it should be for switchmode, you need to be able to play with surface mount parts.  Some modules and mods also require one to appreciate switchmode design at a good level, so can be a steep learning curve if you haven't worked in the area.  Recently I was checking out XL6009 and MT3608 step-up dc/dc's for reapplying 5VAC to 12VDC for heater powering - and aspects of the Enable pin and control mode changes due to load changes needed some appreciation.  A few years ago a variety of 12Vdc battery inverters (for car  cigarette outlets) and similar were coming on the ebay market - they typically needed modified output side rectification/filtering done at the smt level but made very good B+ supplies.

For most B+ supply applications, if the input DC is stable, then any B+ output often doesn't need direct voltage regulation, as the supply is quite 'stiff'.  Also, grounding in the system is still a concern even for isolated outputs, due to parasitic current paths that are always going to be a concern whether the output rail is isolated or not.