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Electronics => Projects, Designs, and Technical Stuff => Topic started by: Mat219 on January 28, 2020, 08:04:46 pm

Title: ESR of a boost converter output capacitor
Post by: Mat219 on January 28, 2020, 08:04:46 pm

Hi.
I'm trying to design a 200V boost converter for nixie tubes based on this schematic : https://threeneurons.wordpress.com/nixie-power-supply/hv-supply-kit/

But i don't know if my output capacitor will be good for the job. Is the capacitor ESR important for a boost converter design? And what are the effects of it?

Thanks for your time everyone.

Title: Re: ESR of a boost converter output capacitor
Post by: Dmeads on January 29, 2020, 06:43:33 am

With only 5W of output power, it shouldn't be a super bad issue, but still something to take into consideration. I was building a 300W Boost converter where ESR was a HUGE deal due to output ripple current and power dissipation. (I blew up more than a few capacitors haha).

I dont believe ESR will effect the output voltage much (may cause a little ripple), but it could effect the current more.

These tutorials were a great help to me: https://www.powerelectronicsnews.com/technology/the-dc-dc-boost-converter-power-supply-design-tutorial-section-5-1 (https://www.powerelectronicsnews.com/technology/the-dc-dc-boost-converter-power-supply-design-tutorial-section-5-1)

some of stuff went over my head but some really did help me. Maybe it can help you out too.

What I would do I calculate the ESR of your cap, then throw it in a SPICE simulator, and model it with the calculated ESR and other values. I can help you if you have LTSPICE or TINA-TI or PSPICE. See what happens at the output.

To calculate ESR, you have to look at the datasheet of your cap. If it is electrolytic/aluminum, it might have the ESR listed, if not, look for the "tan(δ)" parameter. This is called the dissipation factor or DF. Then calculate ESR from this link: https://www.illinoiscapacitor.com/pdf/Papers/impendance_dissipation_factor_ESR.pdf (https://www.illinoiscapacitor.com/pdf/Papers/impendance_dissipation_factor_ESR.pdf)

let me know what happens. you can send a message if needed cuz i dont check the beginner forum a whole lot

Title: Re: ESR of a boost converter output capacitor
Post by: Mat219 on June 11, 2020, 12:24:35 pm

Thanks for the help.
I tried putting 10 ceramic capacitors in parallel at the output and if my simulation is correct, then it should be able to handle somewhere around 30W-50W at like 80-90% efficiency (Using the LT3759).
Now I'm waiting for the parts to arrive and then I can start testing and hoping something doesn't blow up.

Title: Re: ESR of a boost converter output capacitor
Post by: Dmeads on June 13, 2020, 04:31:55 am

Happy to help :)