I recall there was a long thread of discussion about that circuit at one time number of years ago! It works, at some frequency, whatever it is.
For higher currents off-the-shelf CM boost and buck controllers are so good, 1 MHz+ operating frequency makes for small board area, the control loop is pretty easy to stabilize for loads that don't get too crazy.
If the OP needs a really low-cost solution for 150/200 -> 12 the self-oscillating/hysteric flyback is a classic and a negative aux voltage is easily done by adding a winding. Don't even really need a controller at all for well-behaved loads
We don't use power transformers much these days. We usually buy fully standards-compliant, universal-input switching power supplies, wall-warts or enclosed boxes.
--
John Larkin Highland Technology, Inc
lunatic fringe electronics
Which is fine until you need a power rail which isn't available off the shelf.
Once you've got far enough inside an enclosed box to get at the power transformer that it almost always contains, it isn't standards-compliant any more.
Bill Sloman wrote in news: snipped-for-privacy@googlegroups.com:
You are Mumbling... again. COTS is abig world.
Ooops... Billy is obsolete. He refers to the mains input transformer paradigm. THAT is what is not around much more.
We had some very noise sensitive devices that we were only able to power with linear supplies. Short of that, not much reason to use one ever again. Vastly less efficient than a switcher.
Looking again like you never were. You certainly are not right now.
Big switching supplies, for serious power busses, are available in most any voltage, and are available as adjustable.
I usually build a lot of secondary linear and switching regs, on my PC boards, that never get near the AC line, so I can generally design around a 24 volt wart or equivalent. We buy supplies with all the conformance stickers, real or maybe not, and that work anywhere in the world without tap switching and fuse changing hazards.
It's a lot easier to do a CE compliance doc if the power supply is already conforming.
A MeanWell 800 watt switcher box is a fraction of the weight and cost of an 800 watt transformer, and outputs clean DC. The heavy ugly transformer is just the start of a power supply.
--
John Larkin Highland Technology, Inc
lunatic fringe electronics
That's where the analog chipmakers are making a profit; lots of point-of-load power supplies, using single-source chip solutions. The MeanWell unit doesn't have a lot of single-source parts.
Five years from now, you'll be able to buy an off-the-shelf replacement for the MeanWell part of your power supply solution. How about the other parts?
Thats the power supply circuitry with out it's load. The load would be the comunicating cap & probably an inductor in series and sone diodes & 1 or 2 zeners & some more caps for dc output. Unfortunantly, there doesn't appear to be an integrated equivilent.
At our firm, we never use standard supplies. Price is king, so we need to f ind lowest cost. Even at low volumes, it pays to do a custom design
Only true if your power requirement is below 15W. If your unit draws more, or the external supply you use can supply more
Above 15W all the rules with fire comes into play, so the approval process is pretty much the same as approving your own custom supply. And the cost f or the approval is not that high, complete product might be 15k USD for an advanced product with several insulation systems
The hurdle with insulation systems is that it seems UL by amazing coinciden ce have an idea to only approve components/parts that is not part of the IE C system, so that one is forced to make both US and EU variants
Meanwell is expensive. But an easy solution. When you disassembly the Meanw ell and competitor supplies, you find that they really are not that good. W e did an internal products, just me and another guy, and in 12 months we ha d a solution that outprformed the Meanwell types in price and performance.
o find lowest cost. Even at low volumes, it pays to do a custom design
e, or the external supply you use can supply more
ss is pretty much the same as approving your own custom supply. And the cos t for the approval is not that high, complete product might be 15k USD for an advanced product with several insulation systems
dence have an idea to only approve components/parts that is not part of the IEC system, so that one is forced to make both US and EU variants
anwell and competitor supplies, you find that they really are not that good . We did an internal products, just me and another guy, and in 12 months we had a solution that outprformed the Meanwell types in price and performanc e.
Our lowest volume products are normaly 10k units
Max volume 6 million
We can make it for 10 times lower that price, with efficiency orders of mag nitude better (sub 90% efficiency is a joke, cannot see why do would sell s uch bad products)
About 100k USD for NRE (I only worked on i part time). Double that before w e have a final product
o find lowest cost. Even at low volumes, it pays to do a custom design
e, or the external supply you use can supply more
ss is pretty much the same as approving your own custom supply. And the cos t for the approval is not that high, complete product might be 15k USD for an advanced product with several insulation systems
dence have an idea to only approve components/parts that is not part of the IEC system, so that one is forced to make both US and EU variants
anwell and competitor supplies, you find that they really are not that good . We did an internal products, just me and another guy, and in 12 months we had a solution that outprformed the Meanwell types in price and performanc e.
n_title?ie=UTF8&psc=1
Sub 90% efficiency does indicate they just settled for a PFC and flyback de sign, which is a bad move
Do you have a picture of the PCB so we can what they have chosen ?
How do small companies that make e.g. tube guitar amps certify their products at reasonable cost? I don't think many of them are UL listed, too expensive. They don't have much choice but to use an internal off-line linear supply they designed themselves such as it is.
But bizarre voltage rails can be very idiosyncratic. It's your ignorance that is showing here, not mine.
What makes you think that a power transformer is a mains transformer?
Some people are better at keeping switching ripple off the rails at the device than you seem to be. Careful filtering does take skills as well as care, but some of us can manage it.
DLUNU is certain about quite few things where he is less well-informed about than he likes to think.
I didn't know if there was some level of standards certification between the CE self-policing and getting a UL certification on the mains-powered equipment which in addition to the hefty initial fees and re-cert fees they have to regularly test to destruction some number of your products; it's an expense that small "boutique" mfgrs probably can't afford when they're only moving dozens or small-hundreds of units a year that cost say $2000 per.
That stuff has not ever been "my department" so far.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.