theinfamousbob said:
I've never used a MOSFET H-bridge but do know about H-bridges in general.
Remember that sudden changes in direction can cause a voltage swing of 2x the supply voltage, which could kill parts.
Other than that, the circuit looks alright. Just make sure the MOSFETs are high enough power, along with the other components.
-Infamous
The so-called regenerative effect of a 4-quadrant inverter. Yup you will need to dissipate that power somewhere. In big industrial drives this gets re-inverted onto the national grib, but hear I would suggest a braking cct.
a DC-link hysteresis-controlled chopper cct to switch in a low-ohmic, high power resistor across the DC-link to "dump" the excess charge.
Back to main question. 42 volt high
Well one thing I would say the intrinsic diode of MOSFET's are actually extreamly shite when used in H-bridges.
For low-power stuff (1W-5W) they are ok, but for more power, the mis-match in switching times starts to become a major hindrance in ensuring no switching shoot-throughs.
My only concern with this design is to do with your operating voltage. This H-bridge has been setup to run at 12V, as a result they can use the cheaky pull-up resistors to turn on/off the upper FET's
You are not going to have that luxury with working at 42volts.
You are going to have to have an isolated Gate-drive for (at least) the upper two FET's, giving them a floatingh supply to allow the gate-source to be switched local to this isolated supply.
Newport do some very good (small as well) isolated DC
C converters which I would recomend for hte design of the gate-drive.
It doesn't have to be fancy
DC
C converter for isolated/floating rails
Opto to isolate command signal
FET-driver chip
Whith working at a higher voltage the speed at which you turn the FET's on is going to become more important. The problem with this 12V design is it uses a 10k to turn OFF/ON which is bloody slow. You are going to want to turn these FET's on alot faster so a gate resistor in the order of 100R is needed (but check datasheets)
Also you might want to put dedicated interlocks between fuiring an upper & lower device to really rule out any switching shoot-through