Boost (buck) with load disconnect protection

Hello,

I want to buid a (foolproof) battery charger using a (synchronous) boost topology but I've just realized that there's no protection at all (for the Mosfet switches or for the output capacitors) if the load is suddenly disconnected (accidentally or not).

That's it, if the main inductor is "charged" (I'm talking about medium power converters ~ 1kW) then one of its legs is suddenly floating, the voltage across the inductor will literally fly, excedding any common sense voltage limit of a Mosfet switch or an output capacitor.

I guess a full-bridge (non-inverted) buck-boost topology could help (you can latch both inductor's legs to ground) but the losses will increase during normal operations (due to extra switches).

Is there any method to protect a "classical" buck/boost converter against load disconnection?

The easiest and cheapest, is to add a bleeder resistor.
Cheap and easy also means that it is wasteful and lowers overall efficiency.

An improved solution would be to add a fast voltage comparator, which would turn on a mosfet with a large bleeder load.

It could even be made in two stages, where you have a fixed bleeder drawing a small amount of current, and a switched bleeder, drawing significantly more current.

Looks like the only feasible solution. I wonder how fast does it need to react (ns?)..