# Does MOSFET switching gate drive current depend on supply voltage?

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?

• To clarify, you're not asking if changing the gate driver supply will cause a current increase, right?
– W5VO
Jan 15, 2016 at 7:09
• Even if the current stays same, the dissipated power (in the driver) does increase, because while the gate is charging, the driver is half-open and dissipates some power; the higher voltage the more power is dissipated while switching. Jan 15, 2016 at 7:41
• The MOSFET driver usualy has supply voltage of +15V or +12V or double voltage supply +15V/-10V as the MOSFET ratings for Vgs max are almost identical for all MOSFETs. Jan 15, 2016 at 9:21
• Q=CV. I = dQ/dT = CV * switching frequency. And C includes the drain-gate capacitance (Miller capacitance) which sees the supply voltage. So, yes.
– user16324
Jan 15, 2016 at 13:05
• So is the Q used in current calculation not the "gate charge" from the data sheet, but some other function of C and V? Jan 15, 2016 at 20:47