I am trying to design a buck converter using LM2576HV (Vref:1.23 V) and a digital potentiometer. (Input:48 V, Output: 0 to 48 V, Imax=3 A). 

But the digital potentiometer with the highest supply voltage I could find works with 36 V. So I can only get 1.23-36 V at the output of the buck converter. 

I am thinking of using a linear regulator like TPS7A4101 that converts 48 V to 36 V to be able to supply the potentiometer, then using an opamp to be able to increase the digital potentiometer output from 36 to 48 V. In this way, the output will be 1.65-48 V.
 
Would this be the right approach or should I go a different way? I have doubts about whether I can get enough current from the opamp output. Also I can't get 0 V at the output because of the reference voltage of the LM2576HV. How can I reduce the minimum voltage at the output from 1.65 to 0 V?