Biasing switching inductors for greatest efficiency for the size.

[gbugh]

Arrticles about Dr. Cuk's designs talk about alternating the inductor's magnetic flux direction so as to allow a smaller core to be used. Capacitors are added inline so there is no DC bias through the inductor. If I have to have pulsing DC current through certain inductors, can I accomplish the same thing if I attach a permanent magnet to return the flux to an opposite direction between DC pulses? I could size a permanent magnet's flux to be half the pulsed DC flux and then use a smaller size inductor core? Would that work?

George

 

[gbugh]

I guess maybe it would cause excessive leakage flux if the magnets were 180 degrees opposed to the pulsing DC generated magnetic flux direction. Would it work if the magnets were at 90 degrees to the pulsing flux direction? Would it still allow a smaller core to be used?

 

[BradtheRad]

By sending AC through a core, you can get by with less current amplitude.

When you send pulsed DC, it needs to be at greater current amplitude if you want the same power transfer. In turn, the greater current requires larger wires, as well as larger ferro metal mass to avoid saturation.

The idea of bringing a magnet close to a coil sounds similar to something called a 'magnetic amplifier'. It is also done by sending DC through an auxiliary winding on a transformer.

https://en.wikipedia.org/wiki/Magnetic_amplifier

 

[mtwieg]

Using an auxiliary bias winding is a more effective way to do the same thing, though it normally doesn't save any overall efficiency (once you account for power dissipated by the bias winding).

 

[schmitt trigger]

Do you have a link to those Dr Cuk's articles?

I had also read somewhere else about pre-biasing the core in the opposite direction of the working flux.

This would be analogous to prestressed concrete forms, where a stress opposite to the working conditions is added during fabrication.

 

[gbugh]

Do you have a link to those Dr Cuk's articles? QUOTE]

Somewhere in 1 of these:

part 1 **broken link removed**
part 2 **broken link removed**
part 3 **broken link removed**

I thought I read it saying that the capacitors in series with the coupling transformer's primary and secondary allowed a smaller transformer to be used because then the power pulses went both polarities through the windings.

 

[schmitt trigger]

Something happened to the links above. Page not found.

The path somehow becomes truncated after the images/

 

[gbugh]

I've watched for decades how some of the best information and discoveries available are sequestered from the internet.

or maybe the facts in the 3 part article were found to be in error.

but strange how they disappeared just a week after being accessed again.
I'll try to attach them to this message.

View attachment Bridgeless PFC Converter Achieves 98 percent part1.pdf
View attachment Bridgeless PFC Converter Achieves 98 percent part2.pdf
View attachment Bridgeless PFC Converter Achieves 98 percent part3.pdf