Boost Converter Design Help

Dear Mamarts,

Mamarts said:

I calculated the RLC components and duty cycle based on my Input and output, but I could not get a result at least close to 2.5V, Is it because I have to add the Error Amp first to see a good result? 

First, thank you for the information your provided! I am able to read all of it and I, personally, found it very helpful!

With respect to your question, I am not sure how you computed your "RLC and duty cycle" based on your desired input and output voltages of 500 mV and 2.50 V respectively, but perhaps you used the expression:

If so, this expression is only valid if the load power is exactly equal to the power delivered to the inductor during its charging period defined by your switching signal. This mode of operation is what is termed "continuous". It also ignores the on resistances of your switch and the ESR of the capacitor and series resistance of your inductor.

The relationship between the input voltage, output voltage and duty cycle of your switching clock above is no longer is applicable if the inductor current is no longer continuous throughout the switching period, but assumes a value of zero for some portion of the period. There is a critical load current that defines the boundary between continuous and discontinuous modes of operation. I do not know what your critical load current is as I am not sure which mode of operation you are trying to operate and do not see a  plot of inductor current.

Hence, I think you first need to define what mode of operation you are designing your boost converter and then set the component parameters before connecting any feedback.

Shawn

Dear Shawn,

Thank you very much for the response These are the equations I have used to compute for my RLC and duty cycle to be in CCM. Sorry that I forgot to mention that my boost converter is operating in CCM. Below are the provided Transient Response of the Inductor current with the PWM.

I have used this equations to show the operating regions of the MOS and their equivalent RDS ON.


The problem I found with this eqautions is that it will only use the First output of the PWM, if the PWM will start with a low signal it will turn the PMOS(M1) on and NMOS(M2) off, then it will calculate its Rout and its region. I will have to change the inputs of my comparator to make the PWM output start with a High signal to turn the NMOS on  and vice versa, and will calculate the NMOS(M2) Rout and region.

Dear Mamarts,

Mamarts said:

hese are the equations I have used to compute for my RLC and duty cycle to be in CCM. Sorry that I forgot to mention that my boost converter is operating in CCM. Below are the provided Transient Response of the Inductor current with the PWM.

Your first equation ignores all the parasitic elements in the converter. Hence, I am concerned you may expect performance that is not consistent with your expected performance. Thank you for your added waveforms. I took some time to analyze your waveforms and computed what I expect ts output voltage may be. The value I get when I estimate voltage drops for your two switching transistors (vds) and for your inductor real part (rs) is quite close to what you are observing. I then optimized the duty cycle to provide a n output voltage of 2.50 V. I included the equations I used. I also double-checked my result using an on-line tool. I included its result and the link in the attached note. I hope this is useful!

Shawn

boost_converter_analysis_060123v1p0.pdf

Dear Shawn,

I would like to express my sincere gratitude for the time you have dedicated to providing me with valuable feedback on my queries. Your insights and suggestions will undoubtedly prove invaluable in guiding me towards success. I genuinely appreciate your efforts, and I am confident that the knowledge you have shared will significantly contribute to the positive outcome of my endeavors.

Thank you once again for your kind assistance.

Best regards,

Mamarts

Dear Mamarts,

Thank you for your knid, but very undeserving, words! I am just happy to read some of the information is helpful to you. Thank you, however, for letting us know the comments were of some use!

Shawn