Dear all,
I have designed a buck converter of:
Vin=50V
Vout=12V
Iout=30A
Fsw=50KHz
How do i calculate the type 2 compensation for this buck converter.
Vikas Dabas
India
Dear John,
I have already studied this note. it shows type 2 and type 3 compensation using simple and OTA. But when it comes to an example, it only shows example of "Type 2 compensation using OTA".
For my application, i am using simple opamp. it is not OTA. Kindly suggest how to calculate or assume the frequency of pole and zero for type 2 compensation.
also How to assume the value of first R1 in FP0 for calculation to start.
One more thing to clear here is: following values are calculated for OTA, are these frequency same as Fp1 and Fz1 for simple feedback? if not than please suggest how to calculate them? if yes, still i need to calculate the Fp0.
Also one more thing( do not mix with above question):
You have mentioned something in previous post: "Your ESR zero will cancel one pole. You can place the zero of your compensator network at or below the LC resonant frequency to cancel the other pole. You can place the compensator pole two decades above that"
What about the third pole which is produced by the compensation? where should it be placed?
By definition the crossover frequency occurs where the gain of the compensated error amplifier is equal and opposite of the gain of the power stage. So you have to know the power stage gain to calculate the integrator. Placing the zeros and poles can be done many different ways. The above example places the zero and pole symmetrically about the crossover frequency. That approach gives maximum phase boost. I previously suggested a method that uses zero / pole cancellation. It is just another way to do it. There are a few other techniques as well. here is some additional literature:
And another app note for voltage mode control. It uses type 3 compensation, but thee principles are similar:
