For flyback SMPS, how do we know that our input capacitor value is sufficient for some peak power requirement?
I understand that bigger input capacitor will have more advantage on this peak power. These capacitors are local energy buffers that can quickly supply high currents to the load when it needs it, but how minimum do we need to meet this peak power?
Assume that the transformer have enough primary current,
Example if the flyback SMPS is designed at rated power 16W, and it has peak power requirement at 80W, therefore I need to change capacitor value from 47uF to 270uF?
Below are some calculation that I made & some reference from Infineon Design Guide
Is this the correct way?
Please share if you've any better way to do it.
UPDATE : 29-MAY-2020
Thanks to @Verbal Kint for very useful comment.
By referring to some equation in Bulk Capacitor Calculations, C.Basso, I think the estimation of the input capacitor value for certain peak power requirement will be better due to it able to check the minimum bulk valley voltage at low line while delivering 94W.
Below are my new calculations:
By using equation below, I will get 116.4uF
After that, selecting a normalized value for the bulk capacitor. For this example, I choose 150uF, and check value of Vmin when the equation below equal to zero.
Remark: For charge/discharge curve, Vcmin = 84V is based on td = 5.957ms, Vpeak = 120.2V, Cbulk = 150uF
From graph above, during Y=0, Vmin = 68V, and Vbulk = 52V
Based on that, for peak power 94W at 85V minimum voltage input, with 150uF capacitor, the capacitor DC voltage will discharge from 120V to 68V within 6ms.
Just one new question, how do we relate peak duration, example the peak duration requirement is 100ms into the calculation above?