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I have seen many high watt like 1200 or 1500 watt boost converters and not a buck converter with that high wattage or power rating . I'm planning to make one buck converter (input- 35 volts output-3 to 35 volts current -30amp max and adjustable ) but is there any restrictions to the power of a buck converter or are there any certain limitation to the current it can output.(I dont want to buy any 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 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 the current
  • Output cap 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\$ – Hrituraj Singha Roy Aug 30 '18 at 11:26
  • \$\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 '18 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\$ – Hrituraj Singha Roy Aug 30 '18 at 14:13

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