Power Supply for Buck converter Controller

[asimkumar]

I am working for a 120V DC to 5V DC converter. I have planned for a microcontroller based design. But the problem is how to power up the controller part. The Controller needs 5 Volt and how can i get this at startup as there is no power except the 120V input.

 

[mister_rf]

Try this way:

**broken link removed**

**broken link removed**

---------- Post added at 16:22 ---------- Previous post was at 16:20 ----------

Need to modify the resistors value in order to obtain the necessary 5V.

 

[PeteEH]

Alternatively, you could add an LDO with an output of less than 5V (say 4.75V), and then diode OR this output with the output from the buck. This allows (4.75V - Vd) for the microcontroller during power up, but when the buck has stabilized, the diode OR will switch over to the more efficient output.
Look for:

- 120~150V Linear Regulator
- Schottky diode OR (0.25~0.4 Vd)
- Low bias current (Quiescent Current)

Depending on your requirements:
MIC5280YME ?