The collapse of a magnetic field

What happens if you bridge out switch 2?

 

This is the circuit of a boost convertor for increasing the input voltage to what is required. They are used in many situations and there is much information on the net.

Normally a diode is placed across switch2 so that the current can pass instantly. If the voltage drop of the diode is too large, then the switch can be closed the odd microsecond later (use a fet) to pass most of the energy.

 

Why are you rejecting the boost mode converter? The fact that current comes from the battery and the inductor just increases the voltage available to charge the capacitor. And it does not have the possibly annoying property of inverting the voltage.

Bob

 

There is no such thing as simultaneity. Read about it in the Special Theory of Relativity by Albert Einstein. There is no such thing as instantly either. For a beginner's introduction, written pretty much in layman's terms, read this paper.

OTOH, if all you want to do is create a magnetic field, and then collapse it to recover part of the energy stored in the field, all you need is a fast switch and a diode, as @Harald Kapp directed you to in his post #5. Here again is his link, just in case you missed it.

It appears from your posts that this is a learning experience for you, rather than having a specific application in mind. There are several things you need to know about practical (real) switches. First, two switches will never change states simultaneously. You can get close, within a few femtoseconds with the best technology, but never simultaneously, for reasons I won't go into. Second, the same goes for instantly. Any switch requires a finite period of time to change from a closed circuit to an open circuit and vice versa. The transition never occurs instantly, although with the best technology it can occur very rapidly.

 

The original requirement that the capacitor is ONLY charged by the discharge of the inductor, is odd or synthetic, and sounds like more of an assignment or thinking challenge. The "simultaneous" would only apply to the 2 switch version - so the original post seems to mix both Initial Requirements - and some of THEW's expected solution...

Here is a great reference for the field...

 

I have versions of that chart dating back to the 80s. I think the first was from Harris. Thanks for a PDF version.

ak

 

I always wondered if you could use something like " http://www.linear.com/product/LT1158 " - where the load=inductor, source of lower mosfet=cap. Q: Is gate drive to lower mosfet high enough to follow source as cap charges up? Also, STMicroelectronics makes a slew of nice mosfet drivers - look at some of those?