Magnets For EnergyEnergy Recovery Snubbers with Rudy Severns
Written by admin on January 23, 2009 – 11:43 pm -
Energy Recovery Snubbers. Part of a series of videos on the design of snubber circuits for power electronics by Rudy Severns. Hello. I’m Rudy Severns, and welcome to my office. I’m writing a book on the design of snubber circuits for power electronics. In fact, the book’s title will be Snubber Circuits for Power Electronics.
What I’d like to do now is to share with you the contents of one of the chapter so that you get a really good feel for what this book is all about. The book will have a number of chapters on different types of snubbers, on switching, on general advice of component selection.
One of the chapters, which I have a copy of the draft in front of me here, will be on energy recovery type snubbers. Because while the normal dissipated type snubbers are the most commonly used, as soon as the power levels start to go very high particularly in power conversion units above about a kilowatt or so, an awful lot of power can be dissipated in the dissipated resistors for the snubbers.
That power becomes quite significant as the power level goes up. For reasons of both efficiency and thermal management you’re going to want, on many occasions, to use a snubber circuit which recovers the energy rather than dissipates it.
By recover it usually means that the energy that would have been dissipated is either delivered to an output load of some kind, or it is back to the input source. In other words, it’s put to some useful purpose.
This particular chapter we’re talking about here on energy recovery snubbers, goes through and talks about a number of different things, but particularly it also talks in general principles. For example, there are many, many papers that have been written on energy recovery snubbers. Most of them, almost all of them, don’t mention the practical problems with energy recovery snubbers in that an energy recovery snubber in its purest form, will have no damping in it because you’re trying to have as high efficiency as possible.
Unfortunately what happens is, without any damping you have noise and ringing so that the circuit doesn’t behave as you think. One of the things that this chapter is intended to bring out clearly is that you still have to have some dissipated damping in the circuit. What it is, is a balancing act between efficiency and saving as much power as possible, and on the other end, having waveforms which are acceptable from a noise and ringing point of view.
The chapter goes through, for example, start off with an example, turn-off snubbers; energy recovery turn-off snubbers. Then it will go on to energy recovery turn-on snubbers. These are circuits which are working, in one case, at recovering the energy in the snubbing at the end of the switching cycle, and the others at the beginning of the switching cycle.
Then, of course, what is very popular is to try to recover all of the energy and to have snubbing at both the turn-on and the turn-off. This section of the chapter will deal with several examples of energy recovery snubbers which are intended to work at both ends; we call them combination snubbers. It turns out that some of them are fairly simple and some of them are very complex.
The final section of energy recovery snubbers will deal with bridge circuits, or we should say these half-bridge totem poles which can be half-bridge, full bridge, poly-phase, these types of snubbers. These form another class of energy recovery snubbers.
In fact, energy recovery snubbers themselves can be divided into those that use the switch as the energy recovery mechanism, the switch being protected, or those which use an auxiliary switch.
All of this information will be presented in this chapter to give a really good overview of what energy recovery snubbers are all about, and more importantly, practical. What can you expect from an energy recovery snubber? Just how good could it be?
In theory it can be 100%, but in practice maybe 75%-80% of the power loss can be recovered and then you’re about there. It actually turns out that the real driver is controlling the circuit waveforms and getting rid of the ringing. The damping, in other words, that’s required to be used in there.
Duration : 0:5:5
Tags: aviation, electronics, energy, Foutz, Jerrold, lossless, power, recover, Rudy, Severns, snubbers, space, supply
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