Hi Akshay,
Thanks for the data you recommended, That will be very useful for my PCB design.
Both of the 150V converter works.
About he 150mA converter, I found the reason that the LM3488 be damaged. Sometimes a over 7V plus is on the FB, which come next stage high voltage plus. When I reduced the trace lengh which connect the FB pin with Rf1 and Rf2, The problem have been solved.I also add a zener diode on FA pin and COMP pin for protect the IC. They bring a slightly increase of output voltage. In the process of the solution to this problem, I tried to add a zener diode on FB simply, but It will bring a huge periodically spike on Vout.
Would you help me to analyse why Vout product the huge periodically spike and if I can remove it by adjust the compensation circuit, and how ?
About the 1.2A converter, I found the reason that it just output half voltage or lower voltage. It is that Rf1 and Rf2 is too small which will make the current of FB bigger. I think bigger current of FB will bring bigger error. So the Vout can not reach to 150V. When I changed the Rf1 and Rf2 for keep the FB current to close 15nA which come from datasheet, The converter works. I think this should be primary cause.
About the Rsen, in face, both of 9mohm and 5mohm works. When Rsen =5 mohm without Rsl, the converter will supply mor bigger current then Rsen= 9mohm with 270ohm Rsl. The reasen that converter just output 3VDC with Rsen=5mohm is that my 24VDC input was not stong enough. So your calculation is correct.
About the Csen. I think the drawing of Datasheet is correct. It should parallel with Rf2 before Rsl, because the signal of Pin Isen is current mode which is not easy to be interference and the signal of Rf2 is voltage mode which is easy to interference. So the Csen is for reduce the interference on Rf2.
About the comp. I found the Vout will be slow move around the 150V (like as it move slowly from 146V to 150v and then slowly move back ) without compensating circuit. Both compensating circuit works, which you select fc =804Hz,fzc= 526Hz, Cc1=1.5nF,Rc=82.5kohm Cc2=150pF and I select fc=69kHz, fzc=9.96kHz, fpc=1.28khz, Cc1=2.28nF, Rc=7Khz. I have read the "AN-1994 Modeing and Design of Current Mode Control Boost Converters". I think the open loop transfer function of main circuit should be equation 30 in page 5 and the open loop transfer function of compensating circuit should be equation 32 in page 6. But I can not found the close loop transfer function of the converter system. I am not very clear about the whole calculation. For example, How did you calculate the Cc2, and How did you remove the Zero of main transfer function by select poles of compensating circuit(like as the 66khz zero of right half plane in page 7).
So would you recommend some application notes or artical to me ? Would you like send your calculation process with detail to me?
Thank you very much.
B.Rs,
Dison