I am using a 3-phase MOSFET driver to drive power MOSFETs for a motor controller. When I connect the circuit to a 24V supply (H-bridge supply) and enable the switching at 25 kHz, the driver gets warm. However, when I connect it to a 40V supply (for the final application) the MOSFET driver gets much warmer. Is the driving current supposed to increase with increased supply voltage? I am not sure because the gate-source voltage on the high-side MOSFETs is the same; the driver just needs to supply 40+Vgs to the gate instead of 24+Vgs to the gate. If the gate charge is the same, why would it take more current to drive it at a higher drain voltage?
Electronic – Does MOSFET switching gate drive current depend on supply voltage
mosfet
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Best Answer
There is a small change in total gate charge with the FET's supply voltage. It is not particularly large, because the difference in Gate-Drain capacitance when going from 24 V to 40 V is relatively small. However, the gate drive current is generated in your IC from a linear regulator from the 40 V input. Therefore with a constant gate drive, the IC will still dissipate more power at higher VIN.
There is an NXP Three Phase Driver IC -- MC34937 which allows the gate drive power to be distinct from the FET bridge supply -- you can use that to either 'move' some of the dissipation outside the IC, or supply it from a DC/DC converter which reduces the power dissipated considerably.