I'm trying to design an integrated power supply to use in IoT projects that I'm working on, some including microcontrollers like the ESP8266 or ESP32. In previous projects I've made, power supply ripple was extremely important to keep low so I just used a linear regulator (along with alkaline batteries since it was a portable product). This time, I'm making projects that are stationary and outlet powered so I'm wondering if this circuit is a way that I can integrate the power supply onto my PCB's directly or if I should just use a wall-wart instead.

The transformer I'm using steps down the input \$120V_{AC}\$ to \$12V_{AC}\$ with a maximum current of 200mA. The target output power for the power supply is 3.3V @ 250mA or approximately 825mW. The BOM list can be found here if component choice would matter overall.


  • \$\begingroup\$ Personally I wouldn't bother as the thermal requirements of an LDO to regulate a 5 V input down to 3.3V with a 250 mA load, are easily fulfilled with just a copper poly heatsink on a PCB. \$\endgroup\$
    – sstobbe
    May 15, 2019 at 4:55
  • \$\begingroup\$ When you say "product", does this mean you're going to sell the device? If so, you should consider the cost of getting the device (including your custom power supply) certified for mains voltage. This is why most manufacturers simply use a listed wall-wart and keep their device entirely low voltage. \$\endgroup\$
    – TooTea
    May 15, 2019 at 9:50
  • \$\begingroup\$ @TooTea I'm not planning on selling the device but I think this would be a good learning experience for me (as long as I don't kill myself) \$\endgroup\$
    – dylanweber
    May 15, 2019 at 16:14

1 Answer 1


A crude answer is that this power supply would work. However to confirm that it would meet your requirements is not something that can be confirmed without knowing the actual specifications. It is commendable that you are using discrete components to power your board. The BoM you have is quite costly. I would recommend using an integrated solution. Something more like this


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