How to regulate the dc power supply?

[zhenqiang]

Assume use a switching PSU to power a project.
If use the +5Vdc out of the psu, but the transient voltage may reach 6.7V,so how to regulate this transient voltage?

 

[KlausST]

Hi,

To regulate 5V supply:
* you could use a linear voltage regulator, like 7805.

A switching PSU specified to output 5V but outputs transients to 6.7V .. in my eyes is no power supply. Buy a better one.

Just to avoid some ripples you coud use a C, an RC filter or a (damped) LC filter.

If you want us to calculate/recommend some circuit we need your supply (voltage, current) requirements
and informations about the "transients" like waveform, frequency ...

Klaus

 

[zhenqiang]

7805,i saw this ic in wikipedia,it has a minimum input voltage above 7v,and i need more current,about 3A.

 

[andre_luis]

I would support the Klaus's recommendation of inserting/increase the capacitor on the load side, prefereably adding ceramic ones in parallel with electrolitics, once this would enhance the I effect if the PID control already performed by the PSU.

 

[schmitt trigger]

Some cheaper power supplies are only guaranteed to regulate if they have a minimum output load.

Try adding some power resistors at the output, which consume about 10% of the rated load, and repeat your tests. You'll be very surprised.
That would be about 300 mA.
Across 5 volt that would be 16 ohm, 2 watt resistor.

 

[treez]

..or put a post smps on the output to get you 5v all the time near enough...eg a sepic.