What does the line "edge resonance between an inductor and a capacitor" exactly mean?

Question

I am working on a project on DC DC converters in which the concept of soft switching i.e, zero voltage switching (ZVS) and zero current switching (ZCS) are used. One method to attain this is using an edge resonant switched capacitor cell (ER-SWC) as specified in one of the IEEE Transactions published in 2013: Analysis, Design, and Performance Evaluations of an Edge-Resonant Switched Capacitor Cell-Assisted Soft-Switching PWM Boost DC–DC Converter and Its Interleaved Topology.

I have been trying to find out the significance of "edge resonance" but in vain. In all my findings I could only see the lines "edge resonance between the resonant inductor and the resonant capacitor" but nothing about what it is exactly and why it is so called. It would help me to justify why I should be using this concept for my converter if I knew what it meant.

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I am familiar with normal resonance occurring in an electrical RLC circuit but not edge resonance. On googling for the same, the results are based on some communication related topics and not electrical. I have seen the same question posted before by someone else but it has never been answered.

Answer 1

All circuits have parasitic inductance and capacitance. Nothing can really be done about that. But, it is possible to find ways to use the parasitic components to advantage in some cases. In power conversion it is sometimes possible to arrange things such that the transfer of energy from a parasitic inductor to capacitor results in greatly reduced switching losses in transistors and diodes.

The most simple example of edge resonance is a voltage step driven RLC with diode circuit.

You probably know that the Q of this circuit is \$\frac{Z_o}{\text{R1}}\$, and as long as R1 has a value that allow Q > 5, the circuit will be very under damped (highly resonant). If a step input is applied, voltage on C1 will ring up to ~ 2Vstep. At that time current in L1 will be zero. D1 blocks any discharge of C1. That's a resonant rising edge. Replace the diode with a well timed switch and you can get a resonant falling edge as well. This may seem a trivial example, but all edge resonance is based on the same dynamic.

H-bridges that have an inductive load and switch capacitance can use edge resonance for Zero Voltage Switching. Operational conditions can be narrow, restricting load and input range, for complete ZVS. Extra inductance or capacitance may have to be added to reach the proper condition for a given input voltage or load.

Also, the same resonance can be used to reduce high frequency spectral components for reduced noise and interference.

Answer 2

Based solely on reading abstracts of papers, the term "edge resonant" seems to relate to snubber action occurring in a selected manner at switching edge in order to minimise energy losses - probably typically by implementing a mix of ZCS (zero current switching) and / or ZVS (Zero Voltage switching as appropriate to achieve the desired optimisation. Snubber triggering and/or switching appears to be based on some derived function of extant conditions rather than at an external time defined position.

For example:

This paper A novel pulse regenerative active auxiliary edge resonant bridge leg link soft commutation snubber and resonant snubber-assisted three phase soft switching sinewave PWM inverter specifically contrasts edge resonance snubbing and "hard switching". I do not have unpaid access to the paper but it seems likely that an examination of their comparison will explain the differences in method. They say -

• The operation principle and operating characteristics of this active auxiliary snubber circuit are respectively described, together with the practical design procedure of this unique edge resonant snubber. Furthermore, the three phase soft switching sinewave PWM inverter with the novel auxiliary active edge resonant bridge leg link snubbers treated here is evaluated and discussed as compared with three phase hard switching sinewave PWM inverter

And this paper A Divided Voltage Half-Bridge High Frequency Soft-Switching PWM DC-DC Converter with High and Low Side DC Rail Active Edge Resonant Snubbers (apparently) associates the term with ZVS / ZCS snubber control. They say :

• " ...All the active power switches in the half-bridge arm and dc bus lines can achieve ZCS turn-on and ZVS turn-off commutation operation and consequently the total turn-off switching losses can be significantly reduced. ..."

Similarly here:

Boost chopper-fed ZVS-PWM DC-DC converter with parasitic oscillation surge suppression-based auxiliary edge resonant snubber

• " ... discussed and compared with the hard switching scheme from an experimental point of view. Finally, this paper proposes a practical method to suppress parasitic oscillation due to the active auxiliary resonant switch at ZCS turn-off mode transition with the aid of an additional lossless clamping diode loop, ... "

Answer 3

Well, from http://www.google.com/patents/US4912622 I found that an alternative term is transition-resonant converter. And this surely is textbook material, the general definition being "it employs resonant transitions only during the instants of switching". That seems to match what the circuit from your paper is doing (in this respect). It appears that "edge resonant" is a term preferred by researchers in Asian countries for some reason.