# MOSFET switching loss from datasheet parameters

• Number2Pencil
In summary, there are a few ways to approximate a MOSFET's switching energy from datasheet parameters, but it is often difficult to find all the necessary parameters listed. These methods include directly listed Eon and Eoff values, using turn-on/turn-off voltage and current waveforms, and following a documented method using gate charge, drain capacitance, and drain to gate capacitance. A simple estimate for switching loss is also provided with an example calculation.
Number2Pencil
Greetings. I am not sure how to approximate a MOSFET's switching energy from datasheet parameters. I have stumbled upon a few ways, but in all cases I've found it is pretty rare to find a datasheet with all the correct parameters.

Here are some ways I've found:

1) Eon and Eoff are listed directly in the datasheet. Very rare find.

2) The turn-on/turn-off voltage and current waveforms are provided on a single time plot, so I can multiply them together and integrate (usually with geometric approximations). Also very rare.

3) The method outlined in this document:
http://www.btipnow.com/library/whit...lculation Using the Data-Sheet Parameters.pdf. Seems to be based off of a particular test-circuit (some test circuits have Rg going from the gate to ground instead of gate to pulse generator and don't include the upper mosfet/inductor). Also, the "gate plateau voltage" is a rare find in the datasheets for me...unless it is listed with a different name. I actually haven't found any datasheets with this parameter listed.

So I'd like to know if there is a way to approximate switching energy that could be derived from the most common mosfet datasheet parameters.

The switching loss will be determined by the gate drive and the load circuit topology.
You must use the mosfet parameters to evaluate turn on and turn off transition times.
It is usually enough to know the gate charge, drain capacitance and drain to gate capacitance.

A simple estimate of switching loss is = frequency * 0.5 * (total transition time) * (off voltage) * (on current).

So if you are switching 24 volt, 10 amp at 10 kHz and it takes 1 usec to turn on and 2 usec to turn off, the switching loss will be... = 10 k * 0.5 * (1u + 2u) * 24 * 10 = 3.6 watt.

## 1. What is MOSFET switching loss?

MOSFET switching loss refers to the energy dissipated by a MOSFET during the process of turning the transistor on and off. This energy is lost in the form of heat and can impact the overall efficiency and performance of the MOSFET.

## 2. How is MOSFET switching loss calculated?

MOSFET switching loss can be calculated by using the parameters provided in the datasheet, such as the gate charge, drain-source voltage, and switching frequency. There are also online calculators and simulation tools that can help with this calculation.

## 3. What are the main factors that contribute to MOSFET switching loss?

The main factors that contribute to MOSFET switching loss include the gate charge, drain-source voltage, and switching frequency. The higher these values are, the higher the switching loss will be. Other factors such as temperature, parasitic capacitances, and the design of the circuit can also play a role.

## 4. How can MOSFET switching loss be reduced?

MOSFET switching loss can be reduced by carefully selecting a MOSFET with lower gate charge and on-resistance values, as well as operating it at a lower switching frequency. Proper circuit design and layout can also help minimize parasitic effects and reduce switching loss.

## 5. How does MOSFET switching loss affect circuit performance?

MOSFET switching loss can impact circuit performance by reducing efficiency, increasing heat dissipation, and potentially causing thermal issues. It can also affect the switching speed and reliability of the MOSFET, which can impact the overall performance of the circuit.

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