switch mode DC step down converter

Thread Starter


Joined Sep 19, 2006
hello,i wish to ask,can a simple BUCK converter be use as step down power supply?

what i doubt is,the voltage is constantly ON and OFF although it switch at high frequency like 1kHz,

so what i doubt the most is,can a simple BUCK converter step down from 30V to 5V and supply a memory unit such as microcontroller?

the microcontroller has it maximum voltage rating,which is 5.5V ,if to see the switching microscopically, actually for every duty cycle, it apply 30V to the microcontroller(this is over votage rating) then ZERO volt for the rest.

my simple question is:
1) will the microcontroller work? or it contantly reset because the voltage is zero and 30V periodically.

2) or will the microcontroller blow due to over voltage?

3) can i really consider a switch mode buck convert output as REAL voltage level,in another words,can i consider a 30V - 5V buck converter is same like the output of a linear voltage regulator?

i dont dare to try this on my PIC controller because each cost me 40 bucks,please help me every experts.i'm very appreciate your help.

Please share with me the actual experience regarding this,because i know the theory,i lack of practical experience.

Thank you very much to everyone.


Joined Feb 24, 2006
You have a great misconception of how a buck converter works. The output is not switched between 0v and 30V, the output is constant plus or minus small excursions in the tens of millivolt range. One side of a clamped inductor is switched.

Go quickly to the Linear Technology website
Download LTSpice/SwitcherCAD III
File | Switch Selector, and enter your parameters for input voltage range, output voltage range, and current. Boom! the program will create a schematic for a switching regulator and then simulate it.

Even if you can't afford their parts you can learn how a SMPS works and avoid asking rediculous questions.