simple DC DC up converter

LTC had/has a chip that will run on millivolts, like from a thermocouple.

You could design a boost converter from scratch. That would be interesting.

Whatever you do, the 1.5v battery won't last long.

Why not use two 1.5v cells? That's sure easy.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

If the single 1.5V cell is physically big enough, you can get any life-time you want.

Switches that turn on hard with only 1.5V to drive the gate can be hard to find, but as Jim Williams spelled out, in a bunch of Linear Technology application notes, you can get better than 90% conversion efficiency out of a Baxandall Class-D converter (not that Jim Williams knew that Peter Baxandall had invented the circuit in the UK back in

You will probably have to wind your own transformer and feed inductor (or get them wound for you). John Larkin likes to buy his off the shelf, but mostly you have to match the transformer to the job.

The Baxandall circuit with bipolar transistors can be picky about the inductor value. Switching FETs don't seem to be able to "squeg" in the same way, and I suspect that the right zener diode could tame the start-up with bipolar switches without doing much at all in regular operation.

The best transformer is no transformer.

A Bax with custom magnetics might cost 50x what a practical circuit would. And probably take years (or decades?) of fiddling.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

I have used MCP1640 to do exactly that. TI have very similar parts but I have not used them.

Which is the reaction one always gets from people who can't design transformers.

It might if John Larkin designed it.

Most inverters are built around transformers, and if you have a transformer-winding machine - hand-cranked one from China can be remarkably cheap - it won't take more than a couple of days.

Modern inverters are reputed to rely on printed windings, but you can get them on fast turnaround if you are prepared to pay a bit extra.

The sort of printed circuit shops who can squeeze enough copper into the printed windings to make a respectable transformer are a bit specialised. I talked to couple the last time I went to an industry exhibition, but that was more than a decade ago.

ebay has it all? ebay.com/itm/375617242393?_skw=DC+1.2V+to+5V+upconverter+converter+module

Nice! And cheap!

That looks perfect, thx. This is a hobby project and whilst there are some super cheap ready built modules from china/ebayI need to integrate this into an existing small pcb. Othe options mentioned are a non starter really.The Iq of my design is 3uA with only now and again requirement to switch on the booster so battery life will be goog at 1.5V

That is also a possibility ! I can make it into an 'add on' daughter board. Saves rolling my own . Thx.

The Baxandalls are all step-ups because the transformer is approximating a current transformer. Voltages get switched across primaries, currents get switched through them.

Pre-Assembled Modules (much better than the headache(s) of building your own)

If you prefer a ready-to-use solution rather than designing a PCB, several modules are available:1.5V to 5V Step-Up Module: Common generic modules found at retailers like Amazon or AliExpress can deliver up to 500mA from a single cell.Quartz Components 1.5V-4.2V Module: A compact module designed to provide a stable 5V output for USB devices and microcontrollers.Critical Design Note: When boosting from 1.5V to 5V, the input current will be significantly higher than the output current (typically \(>3.5\times\) higher due to voltage ratios and efficiency losses). Ensure your battery can handle the required discharge rate.

-google AI

This looks interesting:

Wonder how much Rs. 36 is...it's pretty cheap.

basically the same form factor as an to-220 78xx voltage regulator

A tiny Tadiran lithium cell would give you 3.6 volts and about an amp-hour. Simple.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

Sure, but you can buy AA cells any drugstore or filling station, Tadiran not so much.

Plus I would have to include an Li charger and USB C socket...

The Tadirans are primary cells and will last at least 40 years at microamp loads.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

Most published Bax oscillators have a secondary on the transformer, so can output any voltage. The transformer typically has seven pins. Plus an inductor off to the side.

They use a large number of expensive components to do a simple function. Some people enjoy that style.

I wonder if any successful products use the Bax topology nowadays.

In olden days, tubes and transistors were expensive and transformers were relatively cheap, so equipment used a lot of transformers. No more.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

I think that TT expects microamp-level loads. Cheap boost converters may be 1% efficient down there, and will kill the battery soon even with no load.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics