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# mosfet losses during inrush current

#### Siddharth_saxena

##### Junior Member level 1
how to calculate losses of mosfet during inrush current?

You can do this with a DSO oscilloscope.

Regards, Dana.

To calculate the losses of a MOSFET during inrush current, you need to consider the following parameters:

1. MOSFET parameters: The datasheet of the MOSFET provides information about the maximum voltage, current rating, on-resistance, and gate charge.
2. Circuit parameters: The inrush current, the voltage level, and the duration of the current surge.
3. Switching frequency: The frequency at which the MOSFET turns on and off.
The losses can be calculated as follows:

1. Conduction losses: During inrush current, the MOSFET will be fully turned on, and the losses will be due to the on-resistance of the MOSFET. The conduction losses can be calculated using the formula:
Pcon = I2R
where Pcon is the conduction losses, I is the current flowing through the MOSFET, and R is the on-resistance of the MOSFET.
2. Switching losses: During inrush current, the MOSFET will switch on and off rapidly, which leads to switching losses. The switching losses are proportional to the switching frequency, the gate charge of the MOSFET, and the voltage level. The switching losses can be calculated using the formula:
Ps = Qg x V x f
where Ps is the switching losses, Qg is the total gate charge of the MOSFET, V is the voltage level, and f is the switching frequency.
By adding conduction and switching losses, you can calculate the total power losses of the MOSFET during inrush current.

It is essential to ensure that the MOSFET's maximum power dissipation rating is not exceeded during the inrush current, as this can cause thermal runaway and damage the MOSFET.

Regards, Dana.