MiscEl: PowerMos

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This page is used to estimate the turn on and turn off time for a PowerMos.

Input values

DriverWhat type of driver used, select the best match for your actual driver
Vswitch (Vsw)Open loop drain voltage
Iswitch (Isw)Closed loop drain current
FswitchPowerMos switching frequence
On percentPart of switch cycle driver output is pulling high
VgdriveGate driver supply voltage
IgdriveGate driver current
RgdriveGate resistor, excluding any internal driver resistance
QgsGate charge before PowerMos start conducting
QgdGate charge required to change output voltage from Vswitch to 0
QgTotal gate charge including safety overdrive
VgsthVoltage where PowerMos start conducting
VtVoltage where Qgd charges, this value must be estimated from the curves i.e. "Typical Output Characteristics", it is the lowest gate voltage that can turn on the PowerMos at the desired current.
VgGate voltage for Qg, Qg is scaled for other gate voltages

Output values

Total turn on timeTime from drives goes high to Vg has reached Vgdriver
Turn on timeTime from Vg reaches Vgsth to Qgd is charged
Total turn off timeTime from drives goes low to Vg has reached 0
Turn off timeTime from Vg reaches Vt until Vg is down to Vgsth
PowerMos powerEstimated power lost in PowerMos (Turn-On on-state Turn-Off)
Gate resistor powerPower lost in gate resistor (Turn-On Turn-Off)
Gate driver powerPower lost in driver (Turn-On Turn-Off)
Scaled QgQg is scaled according to high voltage on gate

The assumptions used are

It is possible to make external tables with driver specifications, for more information email me.