Boost converter diode dissipation?

[eem2am]

Hello,

I wish to calculate the loss in the boost diode of a boost converter.

I wish to do this because I want to see if it’s worth using a synchronous boost converter instead.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Here is the spec:

Switching frequency = 100KHz
V(in) = 2.1V
V(out) = 10V
P(out) = 2.71W
Inductor = 100uH

Average boost diode forward current = 0.339A

Boost diode = 1N5819

….datasheet of boost diode…….
**broken link removed**

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

This diode, at my I(f) of 0.339A would have…………
V(f) = 0.4V …and…
Diode capacitance = 30pF

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Please now could you check the diode dissipation calculation:-

I am taking it from page 4 of…………
Cree Applcation Note:
**broken link removed**



So:-

Conduction loss = 0.339 x 0.4 = 0.136W
Switching Loss = 2 x ½.C.V^2 X f = 300uW


…..Total Boost diode loss = 0.1363W

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


This seems very low,
I am now wondering why anyone would ever consider using a synchronous boost converter.

I cannot seem to find the "beta" value which is necessary to calculate the equivalent diode resistance “Rd” figure in the 1N5819 datasheet above, though the above Cree Application Note mentions that I should take it into account.

So…..

Do you know what figure I should take for the Diode’s Resistance “Rd” ?
(On page 3 of the above app note it’s given as:- (beta) x Tj + Rd0
-but it doesn’t say what “beta” is)

-And do you know if this didoe dissipation calculation is correct ?
[/u][/b]