Hi,
I was thinking about how to decrease switching losses in an Hbridge, ie. one with a 600V supply.
If the switching time is ~50ns for the fets, could you reduce the switching losses by using a series inductor between the 600V supply and the top of the Hbridge that saturates soon after the switching is complete, so that it restricts current flow during switching, and then saturates once switching is complete so that it doesn't restrict current flow to the load?
cheers, Jamie
In practice, this function is only practical if the device can be 'desaturated' in time for the next switching period. In the process, the flux swing produces losses that have to be taken into account to ensure that material limits and magnetic characteristics are not compromised.
The volt-seconds that such a device needs to exhibit in a 600V switching circuit is not small, while the choice of suitable core materials and shapes are.
Most attempts at switching loss reduction using saturable reactors employ the parts in circuit branches where impressed voltage reversal occurs naturally during the full switching cycle, or in auxiliary assisted switching cells that work to recycle the magnetizing energy.
In such circuits, the limitations of practical rectifiers soon becomes evident; don't be the first on your block to discover reverse recovery charge amplification. Large currents in small rectifiers accumulate larger stored charge and foward over-voltage than the same current in a larger rectifier of similar 'speed'. Sad but true.
RL
google 'loss-free snubber', "passive snubber", "soft switching" or "assisted switch"
RL
You've been anticipated. See:
Have something to add? Share your thoughts — no account required.
Ask the community — no account required