FudFly converter

Tim Williams wrote:

> Yes, at low power you don't care about crap efficiency

True, but even then the efficiency is not that bad. 70% or so, very 
close to a regular flyback.

> and the current can be limited by relatively high Rds(on) or hFE-limited transistors.

Adding insult to injury, the SN6501 uses R_DS_ON(temperature) to balance 
the flux. But at that power level any dishonourable trick is acceptable.
For example, a series of 100mW flybacks I use in quantity for gate 
driving purposes are based on a 6mm OD ungapped toroid. There are enough 
volt-seconds available that allow me not to care. It is super-tiny and 
reliable, f^Hignore the rules.

	Best regards, Piotr

jlarkin@highlandsniptechnology.com wrote:

> I call that an autotransformer flyback. I usually use the DRQ127-type
> dual inductors and as much voltage multiplier as needed.

Here is a good introduction to these:

https://www.youtube.com/watch?v=mr3sCPnsOas

	Best regards, Piotr

On Sun, 26 Jul 2020 22:38:58 +0200, Piotr Wyderski
<peter.pan@neverland.mil> wrote:

>jlarkin@highlandsniptechnology.com wrote:
>
>> I call that an autotransformer flyback. I usually use the DRQ127-type
>> dual inductors and as much voltage multiplier as needed.
>
>Here is a good introduction to these:
>
>https://www.youtube.com/watch?v=mr3sCPnsOas
>
>	Best regards, Piotr

My very first switcher was a center-tapped-inductor buck. It converted
+24 to +5 for a military control system, on the LHA ships. I tapped
the inductor because we couldn't get a 24 volt schottky diode. I might
even have the board still.

The ripple current into the output cap went way up, so it fried caps.
N*I is constant and the tap changes N every cycle.





-- 

John Larkin         Highland Technology, Inc

Science teaches us to doubt.

  Claude Bernard
  

On 25/07/2020 23:07, jlarkin@highlandsniptechnology.com wrote:
> On Sat, 25 Jul 2020 16:57:27 -0500, "Tim Williams"
>> This monstrosity might be better deserving of such a name,
>> https://www.seventransistorlabs.com/Images/Flyward_Converter.png
>> but I don't know why anyone would ever build it.
>
> That one's not isolated.
>
>
But it could be made isolated, as in ...

<https://www.dropbox.com/s/jxr2rx7ujj6l19i/Flyward.JPG?raw=1>

Secondary turns ratios probably need tweaking to fairly distribute the 
two modes of operation?

piglet