DC-DC Converter problem

[Joe_Wu]

Hi, I have recently built a dc-dc converter to convert supply voltage from 6V to 32V, the circuit diagram is as below:



and the circuit on the breadboard is looks like this:



My friend has built one with the same circuit diagram, I have double checked with him, both circuit connects exactly the same with same components, he circuit is working perfectly fine, but my circuit has a problem. my output voltage jump to the 42V, slowly drops to 32V, jump up again to 42V, slowly drops and it repeats this process over and over again. I have no idea what is wrong with it.

Here is how my friend circuit looks like:



Any help will be appreciate!

Thank you!

 

[E-design]

It is not very clear, but make sure the feedback resistors are connected correctly. The connection of R2 to diode and output cap can't be seen clearly on your board.

 

[Akanimo]

Hi Joe_Wu,

If I understand the issues with your powersupply, then it is a 10-V ripple. I noticed that the filter caps = 1320uF (220uF + 100uF + 1000uF) but you reduced it to 470uF (less than 37%).

That reduced the time-constant and so the filter caps charges and discharges rapidly creating higher ripples.

 

[KlausST]

Hi,

I can't find any true storage coils.

A breadboard is not suitable for testing high frequency switch mode power supplies. It may work or not.

One simply can't fulfill the PCB design rules given in the datasheet.

Klaus

 

[Joe_Wu]

It is the problem with the breadboard. problem solved! Thank you!