Switching loss parameter?

[grizedale]

Hello,

I am trying to calculate switching loss's for a FET in an SMPS.

I am usingthis guide.....

**broken link removed**

However, on the middle of page 4 (Right hand side, equation for "Cgd.eqv") there is a parameter called "RL" which i do not know what it means.

Do you know what "RL" means?

 

[Gimlix]

Could it be the load equivalent R?

 

[grizedale]

maybe, i honestly dont know

 

[FvM]

gm*RL is commonly known as the voltage gain (simplified expression) of a transistor stage. Notice that the formula is referring to Miller effect. So RL is obviously means the load resistance.

But the relation only applies in linear operation, and thus apparently, it's introduced to the discussion without further impact. In switching operation, charge summation is used to describe the same effect.

 

[mtwieg]

I have no idea why a linear amp equation appears in literature on SMPS... but the document itself even mentions that the formula isn't useful. Not sure what they were thinking when they wrote it.