Turbo Royer/Baxandall in boost configuration

Is it possible to take your standard Baxandall and tap the capacitor, 
take an aux winding off the secondary and feed a somewhat higher DC 
voltage to the cap (through the usual two-diode supply handoff 
arrangement), and use it to feed the gate drive to the transistors as 
well, which would be clocked rather than self-oscillating.

The goal would be to have a quiet step-up converter that could do say 5 
to ~150 in one step, or maybe with a single multiplier stage. That seems 
hard to do with anything off the shelf as compact pulse transformers 
with the appropriate turns ratio don't seem to be really available, you 
get into CFL-type transformers whose ratios are too large, but there 
might be something appropriate with a third winding to bootstrap the 
primary swing

On 9/20/2021 5:45 PM, bitrex wrote:
> Is it possible to take your standard Baxandall and tap the capacitor, 
> take an aux winding off the secondary and feed a somewhat higher DC 
> voltage to the cap (through the usual two-diode supply handoff 
> arrangement), and use it to feed the gate drive to the transistors as 
> well, which would be clocked rather than self-oscillating.
> 
> The goal would be to have a quiet step-up converter that could do say 5 
> to ~150 in one step, or maybe with a single multiplier stage. That seems 
> hard to do with anything off the shelf as compact pulse transformers 
> with the appropriate turns ratio don't seem to be really available, you 
> get into CFL-type transformers whose ratios are too large, but there 
> might be something appropriate with a third winding to bootstrap the 
> primary swing

Even if I really wanted to roll my own transformers the require ratio of 
something like 47u to 4.7m is annoying to do by hand on some common 
compact ferrite toroid like an FT50-43, and multiple multiplier stages 
start to suck efficiency pretty quickly

mandag den 20. september 2021 kl. 23.53.07 UTC+2 skrev bitrex:
> On 9/20/2021 5:45 PM, bitrex wrote: 
> > Is it possible to take your standard Baxandall and tap the capacitor, 
> > take an aux winding off the secondary and feed a somewhat higher DC 
> > voltage to the cap (through the usual two-diode supply handoff 
> > arrangement), and use it to feed the gate drive to the transistors as 
> > well, which would be clocked rather than self-oscillating. 
> > 
> > The goal would be to have a quiet step-up converter that could do say 5 
> > to ~150 in one step, or maybe with a single multiplier stage. That seems 
> > hard to do with anything off the shelf as compact pulse transformers 
> > with the appropriate turns ratio don't seem to be really available, you 
> > get into CFL-type transformers whose ratios are too large, but there 
> > might be something appropriate with a third winding to bootstrap the 
> > primary swing
> Even if I really wanted to roll my own transformers the require ratio of 
> something like 47u to 4.7m is annoying to do by hand on some common 
> compact ferrite toroid like an FT50-43, and multiple multiplier stages 
> start to suck efficiency pretty quickly

isn't a transformer like used in USB chargers right around the right voltages when run in reverse?

https://dk.rs-online.com/web/p/transformer-switch-mode-stromforsyning-smps/4185470/

On 9/20/2021 6:50 PM, Lasse Langwadt Christensen wrote:
> mandag den 20. september 2021 kl. 23.53.07 UTC+2 skrev bitrex:
>> On 9/20/2021 5:45 PM, bitrex wrote:
>>> Is it possible to take your standard Baxandall and tap the capacitor,
>>> take an aux winding off the secondary and feed a somewhat higher DC
>>> voltage to the cap (through the usual two-diode supply handoff
>>> arrangement), and use it to feed the gate drive to the transistors as
>>> well, which would be clocked rather than self-oscillating.
>>>
>>> The goal would be to have a quiet step-up converter that could do say 5
>>> to ~150 in one step, or maybe with a single multiplier stage. That seems
>>> hard to do with anything off the shelf as compact pulse transformers
>>> with the appropriate turns ratio don't seem to be really available, you
>>> get into CFL-type transformers whose ratios are too large, but there
>>> might be something appropriate with a third winding to bootstrap the
>>> primary swing
>> Even if I really wanted to roll my own transformers the require ratio of
>> something like 47u to 4.7m is annoying to do by hand on some common
>> compact ferrite toroid like an FT50-43, and multiple multiplier stages
>> start to suck efficiency pretty quickly
> 
> isn't a transformer like used in USB chargers right around the right voltages when run in reverse?
> 
> https://dk.rs-online.com/web/p/transformer-switch-mode-stromforsyning-smps/4185470/
> 

Oh yeah....one of those in reverse might work....

On 9/20/2021 6:50 PM, Lasse Langwadt Christensen wrote:
> mandag den 20. september 2021 kl. 23.53.07 UTC+2 skrev bitrex:
>> On 9/20/2021 5:45 PM, bitrex wrote:
>>> Is it possible to take your standard Baxandall and tap the capacitor,
>>> take an aux winding off the secondary and feed a somewhat higher DC
>>> voltage to the cap (through the usual two-diode supply handoff
>>> arrangement), and use it to feed the gate drive to the transistors as
>>> well, which would be clocked rather than self-oscillating.
>>>
>>> The goal would be to have a quiet step-up converter that could do say 5
>>> to ~150 in one step, or maybe with a single multiplier stage. That seems
>>> hard to do with anything off the shelf as compact pulse transformers
>>> with the appropriate turns ratio don't seem to be really available, you
>>> get into CFL-type transformers whose ratios are too large, but there
>>> might be something appropriate with a third winding to bootstrap the
>>> primary swing
>> Even if I really wanted to roll my own transformers the require ratio of
>> something like 47u to 4.7m is annoying to do by hand on some common
>> compact ferrite toroid like an FT50-43, and multiple multiplier stages
>> start to suck efficiency pretty quickly
> 
> isn't a transformer like used in USB chargers right around the right voltages when run in reverse?
> 
> https://dk.rs-online.com/web/p/transformer-switch-mode-stromforsyning-smps/4185470/
> 

This is a cheesy 1 transistor boost, works OK and I can wind the coil on 
a FT50-43 in a few minutes. Efficiency is bad, almost 1/2 watt in the 
base resistor :(((

<https://imgur.com/a/rQofaB4>

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On Mon, 20 Sep 2021 17:45:12 -0400, bitrex <user@example.net> wrote:

>Is it possible to take your standard Baxandall and tap the capacitor, 
>take an aux winding off the secondary and feed a somewhat higher DC 
>voltage to the cap (through the usual two-diode supply handoff 
>arrangement), and use it to feed the gate drive to the transistors as 
>well, which would be clocked rather than self-oscillating.
>
>The goal would be to have a quiet step-up converter that could do say 5 
>to ~150 in one step, or maybe with a single multiplier stage. That seems 
>hard to do with anything off the shelf as compact pulse transformers 
>with the appropriate turns ratio don't seem to be really available, you 
>get into CFL-type transformers whose ratios are too large, but there 
>might be something appropriate with a third winding to bootstrap the 
>primary swing

Lotta words. Got a sketch?

-- 

If a man will begin with certainties, he shall end with doubts, 
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon

On Tuesday, September 21, 2021 at 7:53:07 AM UTC+10, bitrex wrote:
> On 9/20/2021 5:45 PM, bitrex wrote: 

> > The goal would be to have a quiet step-up converter that could do say 5 
> > to ~150 in one step, or maybe with a single multiplier stage. That seems 
> > hard to do with anything off the shelf as compact pulse transformers 
> > with the appropriate turns ratio don't seem to be really available, you 
> > get into CFL-type transformers whose ratios are too large, but there 
> > might be something appropriate with a third winding to bootstrap the 
> > primary swing.
>
> Even if I really wanted to roll my own transformers the require ratio of 
> something like 47u to 4.7m is annoying to do by hand on some common 
> compact ferrite toroid like an FT50-43, and multiple multiplier stages 
> start to suck efficiency pretty quickly.

Buy yourself a simple winding machine with a turns-counter. They were pretty cheap when I last looked.

Or ask Winfield Hill if he knows of a small coil-winding shop near you. Academics are into one-offs for specific gear for specific experiments.

-- 
Bill Sloman, Sydney

On Monday, September 20, 2021 at 2:45:16 PM UTC-7, bitrex wrote:
> Is it possible to take your standard Baxandall and tap the capacitor, 
> take an aux winding off the secondary and feed a somewhat higher DC 
> voltage to the cap (through the usual two-diode supply handoff 
> arrangement), and use it to feed the gate drive to the transistors as 
> well, which would be clocked rather than self-oscillating. 
> 
> The goal would be to have a quiet step-up converter that could do say 5 
> to ~150 in one step, or maybe with a single multiplier stage. That seems 
> hard to do with anything off the shelf as compact pulse transformers 
> with the appropriate turns ratio don't seem to be really available, you 
> get into CFL-type transformers whose ratios are too large, but there 
> might be something appropriate with a third winding to bootstrap the 
> primary swing

I was gonna take a look at your Spice model, but I am currently digesting the active-clamp forward topology (off the clock) so why look at yet another power converter circuit?

But then I thought, maybe the active-clamp forward would work for you too.  Try one of the transformers Lasse recommended.  I cannot immediately see anything wrong with doing that...  the active-clamp forward is nice since there is no reset winding needed, and the clamp capacitor soaks up the leakage energy making it one of the quieter isolated topologies.

But like I said I am new to the topology so I cannot tell you if there are any subtleties to be careful with.  Does anyone here have any insight into the active-clamp forward topology that I can't find in all the app notes?  (not trying to hijack this thread)

On Tuesday, September 21, 2021 at 9:05:38 AM UTC+10, bitrex wrote:
> On 9/20/2021 6:50 PM, Lasse Langwadt Christensen wrote:
> > mandag den 20. september 2021 kl. 23.53.07 UTC+2 skrev bitrex: 
> >> On 9/20/2021 5:45 PM, bitrex wrote: 
> >>> Is it possible to take your standard Baxandall and tap the capacitor, 
> >>> take an aux winding off the secondary and feed a somewhat higher DC 
> >>> voltage to the cap (through the usual two-diode supply handoff 
> >>> arrangement), and use it to feed the gate drive to the transistors as 
> >>> well, which would be clocked rather than self-oscillating. 
> >>> 
> >>> The goal would be to have a quiet step-up converter that could do say 5 
> >>> to ~150 in one step, or maybe with a single multiplier stage. That seems 
> >>> hard to do with anything off the shelf as compact pulse transformers 
> >>> with the appropriate turns ratio don't seem to be really available, you 
> >>> get into CFL-type transformers whose ratios are too large, but there 
> >>> might be something appropriate with a third winding to bootstrap the 
> >>> primary swing 
> >> Even if I really wanted to roll my own transformers the require ratio of 
> >> something like 47u to 4.7m is annoying to do by hand on some common 
> >> compact ferrite toroid like an FT50-43, and multiple multiplier stages 
> >> start to suck efficiency pretty quickly 
> > 
> > isn't a transformer like used in USB chargers right around the right voltages when run in reverse? 
> > 
> > https://dk.rs-online.com/web/p/transformer-switch-mode-stromforsyning-smps/4185470/ 
> >
> This is a cheesy 1 transistor boost, works OK and I can wind the coil on 
> a FT50-43 in a few minutes. Efficiency is bad, almost 1/2 watt in the 
> base resistor :((( 
It's totally revolting. With only one transistor is isn't even a Royer inverter, and the simulation doesn't suggest that it is actually resonant.

That doesn't mean that it won't work, and I suppose it could solve your problem. But all the waveforms are horribly spikey. Not attractive.

-- 
Bill Sloman, Sydney

On 9/20/2021 9:04 PM, Anthony William Sloman wrote:
> On Tuesday, September 21, 2021 at 9:05:38 AM UTC+10, bitrex wrote:
>> On 9/20/2021 6:50 PM, Lasse Langwadt Christensen wrote:
>>> mandag den 20. september 2021 kl. 23.53.07 UTC+2 skrev bitrex:
>>>> On 9/20/2021 5:45 PM, bitrex wrote:
>>>>> Is it possible to take your standard Baxandall and tap the capacitor,
>>>>> take an aux winding off the secondary and feed a somewhat higher DC
>>>>> voltage to the cap (through the usual two-diode supply handoff
>>>>> arrangement), and use it to feed the gate drive to the transistors as
>>>>> well, which would be clocked rather than self-oscillating.
>>>>>
>>>>> The goal would be to have a quiet step-up converter that could do say 5
>>>>> to ~150 in one step, or maybe with a single multiplier stage. That seems
>>>>> hard to do with anything off the shelf as compact pulse transformers
>>>>> with the appropriate turns ratio don't seem to be really available, you
>>>>> get into CFL-type transformers whose ratios are too large, but there
>>>>> might be something appropriate with a third winding to bootstrap the
>>>>> primary swing
>>>> Even if I really wanted to roll my own transformers the require ratio of
>>>> something like 47u to 4.7m is annoying to do by hand on some common
>>>> compact ferrite toroid like an FT50-43, and multiple multiplier stages
>>>> start to suck efficiency pretty quickly
>>>
>>> isn't a transformer like used in USB chargers right around the right voltages when run in reverse?
>>>
>>> https://dk.rs-online.com/web/p/transformer-switch-mode-stromforsyning-smps/4185470/
>>>
>> This is a cheesy 1 transistor boost, works OK and I can wind the coil on
>> a FT50-43 in a few minutes. Efficiency is bad, almost 1/2 watt in the
>> base resistor :(((
> It's totally revolting. With only one transistor is isn't even a Royer inverter, and the simulation doesn't suggest that it is actually resonant.

It'll resonate and swing a vaguely sine wave, but not with the capacitor 
boostrapped in that way, forcing it to swing more than 2x the "real" supply.

> That doesn't mean that it won't work, and I suppose it could solve your problem. But all the waveforms are horribly spikey. Not attractive.
> 

I'd much prefer a proper Royer where I can clock two transistors with 
dead time and PWM the center-tap inductor and all that cool stuff, and I 
have a device in mind to do that with. Cost-effective solution for the 
transformer is a question, though.