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Chokes and Inductors ...
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madires:

--- Quote from: A Hellene on July 21, 2012, 10:14:07 pm ---But chokes are not only used for filtering. For example, the DC-DC flyback converters are called 'ringing choke converters' because the flyback inductor is not really a transformer; it is a choke actually (we should better call it a coil), often with a primary and a secondary winding, or with extra auxiliary secondaries. Why the flyback coil cannot be called a transformer? Simply, because in transformers the energy transfer happens directly from the primary to the secondary windings and at the same time. In the flyback, instead, the primary does not transfer energy to the secondary but it charges the magnetic material of the inductor, while the magnetics are discharged by the use of the secondary winding of the flyback inductor.

--- End quote ---

I think it's called a storage throttle. But with a primary and a secondary winding it's a transformer ;-) The difference is how we drive that transformer, i.e with a nice AC causing a magnetic flux or with DC impulses while storing their energy in a magnetic field. If I would take the flyback coil from above (primary and secondary windings) and drive it with AC there will be a magnetic flux inducing voltage into the secondary winding, matching your description of the classic AC transformer.
A Hellene:
A coil having both a primary and a secondary windings is not necessarily a transformer; it could either be a transformer or a flyback or just two coils magnetically coupled together (i.e. the SEPIC dual inductor). What makes the distinction is not how the primary is driven, but how the energy is collected from the secondary.

Inductors and their windings have a polarity. Assuming that the primary has a positive drive, we can collect the energy from the secondary either by using both the positive and the negative phase outputs, or, by the use of rectifiers, the positive phase output only or the negative phase output only.

In the first two cases we have a forward topology and the inductor can safely be called a transformer because the energy transfer is direct and immediate from the primary to the magnetically coupled secondary.

In the third case we have a flyback topology, and the inductor can not be called a transformer any more because there is not any direct energy transfer from the primary to the secondary windings; instead there is energy storage from the primary to the magnetic medium and energy harvesting from the magnetics by both the primary and the secondary windings after a delay determined by the driver and the inductor circuit resonance, where the stored energy will pick the easiest path to flow no matter if this path is through the primary or the secondary or through both the windings. The most simple examples of this topology are the boost/buck/buck-boost converters, where the inductors they use do not have a secondary winding.

Of course, conventionally, we call every inductor with more than one windings, a transformer.


-George
SeanB:
I have seen a few designs of TV sets that use the forward and flyback sides. A single winding that delivers +200V and -20V from the same winding. You look carefully at the component list and see the diodes are both 1000V silicon fast recovery diodes, and a supply that supplies 200V at 100mA and -20V 1A, but uses 3A diodes for both units, and they run hot for both diodes.
G7PSK:
Choke's is the early or original term for an inductance much in the same way as condenser was the early or original term for a capacitor. The choke was seen back then as throttling or choking the flow of electricity in much the same fashion as a condenser (or Condensor as it was spell't then) was seen as literally condensing electricity.
Kartika:
Hi,  Is did anyone measure how much induction there is for example @100 MHz vk100 vk200
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