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I have seen many high wattage (like 1200 or 1500 W) boost converters but no buck converters with that high a wattage or power rating.

I'm planning to make a buck converter (input: 35 V, output: 3 to 35 V, current: 30 A max and adjustable).

Are there any restrictions on the power of a buck converter, or are there any certain limitations on the current it can output?

I don't want to buy a discrete buck converter IC; I intend to use typical PWM chips like uc38xx, tl494, etc. or even opamps.

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Any limitations will become apparent when you will decide on the exact implementation. Will the converter work in DCM or CCM? What kind of switching device are you going to use? Are you considering using a μC (for PWM) and transistor drivers, or you want a strictly analog device?

You should first answer those questions and then start worrying about limitations.

Things you should definitely check:

  • Inductor can withstand the current - this depends on the conduction mode (CCM, DCM)
  • Diode can withstand the voltage and current
  • Output capacitor can withstand the voltage
  • Transistor can manage the energy flow and not get burned. Maybe use a snubber?
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  • \$\begingroup\$ Well yeah mosfets and diodes are not a big deal. I have mosfets and diodes which will handle that current .I intend to use a uc3843 which works in ccm but its not actually meant for buck converters topology and there are no proper circuit implementation in buck mode also \$\endgroup\$ Aug 30, 2018 at 11:26
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    \$\begingroup\$ I don't think so. TI clearly states that it can be used in a buck topology (ti.com/product/UC3843). Also, the first page of the datasheet figures a simplified boost application. Change the place of the inductor and the MOS and continue from there. \$\endgroup\$
    – thece
    Aug 30, 2018 at 12:03
  • \$\begingroup\$ Yeah but its a CCM chip and you would need a inductor charging current signal to feed to the chip .I have seen people using this uc3843 chip in voltage mode for buck topology \$\endgroup\$ Aug 30, 2018 at 14:13

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