A bench power supply with adjustable voltage and current limits, is one of those essential bits of kit if you're into hobbyist or technical level electronics. Years ago (1960's) when I first started out in electronics, building your own adjustable power supply, was one of the very first projects you would tackle. Back in those days, pretty much all bench power supplies were the linear type utilizing a large mains powered transformer, because switchmode types (SMPS) hadn't came of age at that time. In fact, the mains transformer was very much the most expensive part of your own bench power supply.
Around 35 years ago in the early 1980's, Texas Instruments released the now ubiquitous TL-494 PWM driver IC - at the time (and maybe still today), this was really a mile-stone design, which reduced the complexity, component count, and circuit design requirements, for most all power control/regulation tasks, and was pretty much the 'go to' chip and first to give rise to the mains powered SMPS age. Over the next couple of decades, this IC ended up in everything and became so common place, it was expected the *all* modern designs would be using it. I'm sure a lot of folks here reading this, are familiar with the TL-494 life history, but what isn't widely known is that TI themselves discontinued production of this IC in 2008 or so. In 2005, TI signaled to the world this was going to happen, by announcing that the device will be discontinued, and a lifetime-buy period was in effect. ( see -> for the meaning of 'lifetime-buy' if you don't know the term) It was of course discontinued to make way for later, improved designs that obsoleted the venerable TL-494 product.
I'm not sure of exactly when (I doubt anyone really is), but because I've worked in electronics repair for many years, by my reckoning there were no more 'genuine made by TI' TL-494 chips left in the wild by 2010. I say that, because at around the same time, I started seeing a lot more SMPS power supply PCB failures, from many different types of equipment, and it got to the point where I'd put the post 2008 TL-494 IC, on my 'pet hate' list...along with old tantalum caps, and a host of other 'known problematic components'.
Why the short history recount? Well, here we are in 2020, and chinese knockoffs of the TL-494 are still being produced, and they're still the 'go to' chip for cheapest manufacture of antiquated mains SMPS designs. A few places in particular you will still see this IC being used, is in things like stand-alone SMPS power supply modules, DC->AC inverters, and cheap computer PSU units.
Another place they turn up, is inside these things ;
I have a few bench supplies, and I have one of those above, a made-in-china 0-30v/0-10A bench supply ; let me show you where I ended up using the thing;
Yep, out on the battery charging/electroplating bench ..exactly where it belongs. There is so much noise, ripple and spikes on the DC output of these things, they're useless for any precision or technical application, but are a reliable source of power for electroplating it seems, at least, it hasn't exploded yet, but it's never anywhere near running full output.
So come this human malware lockdown time, I started looking about for a replacement for my electronics bench. this unit was supposed to fill. and I came across a few YT vids from Dave Jones (EEVBlog) which I found really interesting -- these modules have been around for a few years, but I'd never really looked into them ->
I did a bit more searching, and found someone had created open source firmware for the modules as well, which is very cool -->
This got me thinking.... you could add some filtering to the regulator module to make the output cleaner (tried that with the cheap chinese made supply above, but the spikes were still a pita), so all one really needed to do to make their own adjustable supply, is find a suitable DC power source. Even though I have a few 300watt toroidal mains transformers on the shelf here, I'd still have to build a rectifier, add bulk capacitors, do all the wiring, find a case...etc etc, and I'm too old and lazy to be bothered anymore =) Plus the thing would end up weighing as much as my linear supply, that tips the scales at some 8kg.
So I started hunting about on ebay, and found these ;
Case kits for the control modules are out there if you want neat&tidy -->
'Best match' for the 480watt PU brick, is either Riden Rd6006, or DPS50V15 ...I chose the latter.
All these parts are on their way here, but best guess when it'll all arrive here - might still be weeks before the DPS module arrives -- when it all gets here, I'll post back with some of the build stuffs.
Just thought I'd post this, in case anyone else here were interested in this sort of part hacking =)
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