Hi!

Currently I'm studying on how to make and design a Dc Boost converter. My design details are Vs=12V,2A. Switching frequency f=25kHz, output voltage=120V at duty ratio 0.9. For the switching I use a MOSFET. I found a MOSFET IRL510 (details as attached). The VDS for that MOSFET is 100V. So, my question is can I use that MOSFET for my circuit?

 

No. Output voltage is 120V, Maximum Vds is 100V. It will blow up.

 

Consider for a moment that with a duty cycle of 0.9V your converter is spending most of the time shorting the input supply to Ground. Is this really a good idea in your estimation?

 

You see buck regulators with 10% duty cycles, so why not boost regulators with 90%?
I know it’s not the most efficient, but it will work.
It’s not exactly shorted to ground, it‘s storing energy in the choke.

 

You see buck regulators with 10% duty cycles, so why not boost regulators with 90%?
I know it’s not the most efficient, but it will work.
It’s not exactly shorted to ground, it‘s storing energy in the choke.

If you seldom see load transients and you're not worried about having adequate headroom to adjust the duty cycle and the MOSFET can dissipate the heat then I guess it can work but my question goes deeper and asks if it is a good idea. I think not, but YMMV.

 

If you seldom see load transients and you're not worried about having adequate headroom to adjust the duty cycle and the MOSFET can dissipate the heat then I guess it can work but my question goes deeper and asks if it is a good idea. I think not, but YMMV.

I totally agree it won’t make the world’s greatest boost converter; but for someone who is just learning the basics of boost converters, it’s a place to start.
I do remember a while ago, asking for opinions on what was the best way to get 200V from an 18V supply, and a single stage boost converter was suggested by quite a few people.
https://forum.allaboutcircuits.com/threads/switched-mode-conundrum.175319/

 

I totally agree it won’t make the world’s greatest boost converter; but for someone who is just learning the basics of boost converters, it’s a place to start.
I do remember a while ago, asking for opinions on what was the best way to get 200V from an 18V supply, and a single stage boost converter was suggested by quite a few people.
https://forum.allaboutcircuits.com/threads/switched-mode-conundrum.175319/

I think that many people do not appreciate that the cost you must pay for boosting the voltage is a reduction in the available current to the load. They keep imagining a universe in which power out can be greater than or "at least" equal to the power in. The shock that this is not true is often sudden and quit "rude". You can literally see the light go out of their eyes.

 

Likely better would be a flyback circuit, where the two-terminal inductor becomes a 4 terminal coupled inductor.
But that is obviously a more complex circuit.

 

My cheap solar garden lights boost the voltage with a circuit like that in an IC. They limit the boosted voltage with an LED.
What will limit the boosted voltage in your circuit?

 

My cheap solar garden lights boost the voltage with a circuit like that in an IC. They limit the boosted voltage with an LED.
What will limit the boosted voltage in your circuit?

Avalanche breakdown of the MOSFET?

 

Consider for a moment that with a duty cycle of 0.9V your converter is spending most of the time shorting the input supply to Ground. Is this really a good idea in your estimation?

This is just for an experiment. I want my circuit can produce maximum output voltage about 90v at 0.9 duty ratio.

 

No. Output voltage is 120V, Maximum Vds is 100V. It will blow up.

So, the conclusion is I need to find another MOSFET that has VDS more than 120V right?

 

So, the conclusion is I need to find another MOSFET that has VDS more than 120V right?

Yes. And if it were more than "just an experiment" as @Papabravo an I were discussing, you'd probably want to find a better way of getting 90V from 12V as this wouldn't be the most efficient.

 

Yes. And if it were more than "just an experiment" as @Papabravo an I were discussing, you'd probably want to find a better way of getting 90V from 12V as this wouldn't be the most efficient.

This is just for an experiment. I want my circuit can produce maximum output voltage about 90v at 0.9 duty ratio.

Sorry *120v at 0.9 duty ratio

 

Sorry *120v at 0.9 duty ratio

By all means try it. It will work. Use something like a LM3478 to control it.

 

Yes. And if it were more than "just an experiment" as @Papabravo an I were discussing, you'd probably want to find a better way of getting 90V from 12V as this wouldn't be the most efficient.

Okay thanks ya. I try my best

 

Okay thanks ya. I try my best

I have two projects that need this type of circuit - one to power some LED luminaires containing LED modules that run at 90V from a 12V source, and one to power some valves at 200V from 18V, and I'm going to use this circuit, after the discussion we had (linked in Post #7) with a turns ratio of 1:9