For the boost converter below operating in DCM mode, the voltage conversion ratio is calculated as follows:

M = V/Vg = 1 + D1/D2
where
V, Vg are output and input voltage respectively.
From the formula, it is clear that the conversion ratio doesn't depend on D3. So, is there any requirement for D3 here?

 

From the formula, it is clear that the conversion ratio doesn't depend on D3. So, is there any requirement for D3 here?

Just that the lower the voltage drop the more efficient the conversion.
And of course the voltage and current ratings must be high enough.

 

From the formula, it is clear that the conversion ratio doesn't depend on D3. So, is there any requirement for D3 here?

D3 is primarily determined by the load.

 

D3 is primarily determined by the load.

Thanks.
How does it depend on load current?

 

How does it depend on load current?

When the voltage at the cap drops below the target voltage, the switch needs to turn on. A higher load will discharge the cap faster, making it necessary for the switch duty cycle to be higher.

 

When the voltage at the cap drops below the target voltage, the switch needs to turn on. A higher load will discharge the cap faster, making it necessary for the switch duty cycle to be higher.

Can I reduce switching frequency instead of increase duty cycle? I think it is the same here.