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variable power supply circuit

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aneesh:
hi,
i am designing a 30v5A variable supply. the circuit is similar to korad 3005 power supply, the difference is i am replacing the power transitor with pmos but it becomes very hot and temp goes on increasing. the circuit is attached.
whats wrong? why so hot ? at 20v 500ma

bin_liu:
You need to choose the heat sink according to the power loss of 150W.
Also choose a MOS tube that can withstand a lot of power continuously.

aneesh:
mosfet that i am using has good continuously current.
my plan is to design 30v 5A supply. but i cannot go above 500mA. i am using heatsink but i think there is some other problem. As there are PS in the market like dps3005 which uses IRF5210 with the same heatsink and achieves 5A.

xavier60:

--- Quote from: aneesh on June 16, 2020, 04:43:18 am ---mosfet that i am using has good continuously current.
my plan is to design 30v 5A supply. but i cannot go above 500mA. i am using heatsink but i think there is some other problem. As there are PS in the market like dps3005 which uses IRF5210 with the same heatsink and achieves 5A.

--- End quote ---
What is your source voltage? The dps3005 will likely have tap switching to reduce dissipation and a fan to reduce temperature. 
The MOSFET could also be oscillating although it need not necessarily increase dissipation.

aneesh:
input is 20v dc output is correctly regulated to 5v as per requirement  but when i start drawing current 500mA it gets heated badly... the circuit is uploaded whats the prob with the design

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