A Passive Soft-Switching Snubber for PWM Inverters (2004) [pdf]

>"To reduce switching stresses, losses, and electromagnetic interference (EMI), soft-switching techniques have been developed for power converters since the 1970s [1]. There are many topologies of soft-switching inverters [1]–[10], such as resonant dc link, resonant snubber, and zero-current transition inverters [8]. Soft-switching inverters can be grouped into two main categories: resonant dc link and resonant snubber. The resonant dc link provides zero dc-link voltage or current intervals to all phase legs during switching instants, whereas the resonant snubber diverts current from and/or provides zerovoltage intervals to each main device at switching instants. The active clamped resonant dc link converter [1] and the auxiliary quasiresonant dc link converter [2], [10] are examples of resonant dc link inverters. Auxiliary resonant snubber inverters such as the auxiliary resonant commutated pole (ARCP), zerovoltage transition, and resonant snubber inverters [9] belong to the second resonant snubber category."

What it is: A "snubber" (terrible terminology btw, IMHO, but we'll go with it for now!) basically adds a resonant circuit part to a previously non-resonant switch or switched circuit, such as those common in switched power supplies and inverters.

Basically, the "switch-on, switch-off, repeat" circuits that drive electrical transformers of all sorts.

Well, take that, add a resonant circuit component to it (which basically "smooths" the immediate presence of a voltage during the on phase and the immediate drop of a voltage to 0 during the off phase) and that's what "snubber" is.

I should point out that There are power snubbers that do the same thing but for current, i.e., snubbers of one type for voltage, snubbers of another for current, but the basic idea is the same -- smooth things out, smooth the waveform out -- don't allow immediate (instantaneous) dips or spikes, smooth it out over milliseconds, microseconds, nanoseconds, whatever the frequency of the waveform requires...

Anyway, that's a "snubber" (an added resonant circuit component).

Added to power supplies and inverters and transformers of all sorts, once resonance is established, heat/heating/heat losses drop, and power conversion efficiency increases rather significantly.

Switch/switching circuit life is also extended.

Anyway, it's a fascinating topic!