[riphet]

Have a look in the datasheet at the current paths through the components in all modes.
You will notice that in some cases there's current flowing through the internal diodes integrated in the mosfets's. Their spec's are not really good for some chip's: not fast enough or to high VF.
This creates additional power to be dissipated.

This current will flow through the external diodes when good and fast ones are used and this will reduce the chip's heatdissipation.
There are other reasons also but heat reduction is the most important.

Indeed in the datasheet is written:

"Note: Parasitic diodes are indicated on the designed lines. However, these are not normally used in Mixed Decay mode. "

"As shown in the figure above, an output transistor has parasitic diodes.
Normally, when the energy of the coil is drawn out, each transistor is turned ON and the power flows in the
opposite-to-normal direction; as a result, the parasitic diode is not used. However, when all the output
transistors are forced OFF, the coil energy is drawn out via the parasitic diode."

Only when transistors are forced OFF...
That's like a car makes a journey very well, only heats when turned off.

I understand that: Tturn off the last step of each half cycle,
As off twice per cycle. This is in any mode.

Or is it the case that when it passes through zero, some transistor is turned on?

My idea is not to dissipate heat, but that energy regenerating prosecute. I understand that even the existence of regenerating ohm causes heat. But at least most regenerated.

That's my idea, use the correct diodes.
But how fast is fast?
So, I'm looking to calculate the duration of the peak. And also current.

I appreciate any related information.