where heat of MOSFET comes from

[hitbuyi]

Heat of MOSFET
Does heat of MOSFET caused by its conduction losses or switching losses? or by both?
if the heat of MOSET causd by both its conduction losses and switching losses, which is dominating reason?

thank u

Rg.

 

[FvM]

Generally both. It's easy to reduce conduction losses by using a larger area FET. Unfortunately, the switching losses will usually increase. Switching losses can be minimized however by tuning the gate waveforms. Also resonant topologies (ZCS or ZVS) are a way to reduce it.

 

[hitbuyi]

is here a formula to calculate the conduction losses and switching losses?

 

[andre_luis]

Conduction losses may be estimated integrating current ( Ids ) versus voltage (Vds) against time.
However, switching losses is harder, because depends on gate driver capacity.
( slower slew rate increases comutation duration and so, dissipation duration )

+++

 

[ea.arun]

Switching losses are a function of output capacitance(which varies with Vds).Vds and switching frequency.As mentioned in the earlier posts it varies largely with how hard you turn the MOSFET on or other ways how much gate charge you ingect.

These may help

http://www.irf.com/technical-info/designtp/dtwarp.pdf
http://www.infineon.com/dgdl/Applic...506db&fileId=db3a304320d39d590121a671f2d90c38