T50-2 toroid

I forgot to mention an 8.5 cent MOSFET that's an optional part of the kit. The semi company Alpha & Omega makes many outstanding parts that sell for almost nothing. The AO3418 is a 30V 4A with 85-mR of resistance at Vgs=2.5V.

The PT1301 boost IC can switch up to 0.3A on its own, or it can drive the AO3418 at up to 4A. The IC runs off its boosted output voltage (giving the MOSFET gate at least 2.5V to operate), but starts with as little as 800mV, for single-cell batteries, solar cells, etc.

--
 Thanks, 
    - Win

^ ^ ^ ^ ^

Yes, that is called, proving the point... :-)

Same thing here,

A resonant generator, worth a watt or two. You can just see the coil in the bottom. It's incredibly oversized, T86 or thereabouts, would be good for

10x the power in forward mode.

If it's what you have on hand, fine, but don't fool yourself that it's in any sense efficient or economical.

Tim

--
Seven Transistor Labs, LLC 
Electrical Engineering Consultation and Design 
Website: https://www.seventransistorlabs.com/

The only two important factors here were robustness and the abilty to withstand 7kV potential difference between the driver and the floating circuit. Energetic efficiency has never been a concern at all, but surprisingly turned out to be a bit better than that of a regular optocoupler. Economy has never been considered important, the circuit had to be robust. And it is, so what's wrong with that?

The cores are the smallest possible that have enough window area to host the TIW-wound windings. The only smallest core in the catalog, the 4mm one, wouldn't do it. The transformer is less than 8mm tall and the final module is very thin and has superior thermal properties. So again, what's wrong with that?

Best regards, Piotr

I futzed around with the Micrometals calculator and it recommends a different type of core material for the sort of thing I'm doing, I can't bring it up at the moment (site is giving me a "bad credentials" error even though the login I'm using is correct AFAIK.) It may have been MPP powder.

Whoops, I ATM-machined myself. :(

It isn't cheap whatever it is

MPP is the Rolls-Royce in the class, you high-volume production accountant would have a heart attack after looking at the prices. ;-) SuperMSS is often the right choice for a flyback. The problem is there are no physically small powder cores AFAICT, but ferrites go down to 4mm external diameter and if you search hard enough, there are even smaller. So if all you need is a tens of mW physically compact flyback, a ferrite ring would work OK. Pure geometry is the limiting factor there, not the core's saturation properties, etc.

Best regards, Piotr

Another example: a 150mW multi-output push-pull on a 9mm core. Magnetically oversized like hell, but again the smallest able to host all the windings given the required insulation strength. Magnetic properties are not the only factor that matters.

Best regards, Piotr

Given the number of external components in its typical application circuit I would say it has been designed by LTC. ;-) For me the state of the design art is TPS54302: only the expected components, not to mention that it is synchronous. But it is a step-down.

Best regards, Piotr

Step downs are often synchronous; you don't want to waste power on the diode drop, which can be high compared to the output voltage. Also, we're talking low-voltage MOSFETs for the low side. OTOH, for boost step-up converters, with high output voltages, the diode drop isn't very significant. Furthermore the synchronous MOSFET would have to be a high-voltage type. TI usually makes you use an external diode for parts higher than 6 volts out. E.g., the TPS61040 I'm using in my bee-hive monitor.

--
 Thanks, 
    - Win

Incidentally speaking of step down converters I still have some prefab

120 watt fanless ATX power supplies I'd like more power from on the +5 and +12 rails. The controller IC for those rails is a RT8105 and the circuit configuration essentially appears to be the reference design:

The switches are M3006D, they seem pretty beefy already:

The inductors are both 1/2" diameter yellow toroids with about 15 turns of 18 gauge magnet wire on each. Input and output caps are 1000uF 16V through-hole electrolytic.

I might be able to get away with just beefing up the inductors and caps

Actually they're yellow/white so that looks like they're material 26 powdered iron

Where do you people even find those things? I've just been looking for iron powder toroids at the usual distributors, But all I can find are hi mu ferrites.

Have you tried Amidon ?

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-TV

I'm lucky enough to have an old-timey brick and mortar parts distributor about a dozen miles away, with walls and walls full of components. You can just buy them off the shelf in bulk there, they had some overstock.

There's apparently enough customers in a ~6 million population metro area to keep one store like that still chuggin' along.

Thanks.

AFAIK these are re-branded Micrometals. It could be much cheaper to go to the source.

Cheers, Gerhard

Yeah, for any kind of quantity, you want to talk to Elna Magnetics (they used to have an online inventory search, looks like they've overhauled their website and conveniently left this feature on the back burner...), or

, or or a couple of others out there.

Don't know any .eu sources, YMMV.

Tim

--
Seven Transistor Labs, LLC 
Electrical Engineering Consultation and Design 
Website: https://www.seventransistorlabs.com/