5v power supply without ripples

[raman00084]

i am designing a pic development board i need 5v power supply i am planning to use 7805 regulator .
what inductor value i must use for LC FILTER is a free welling diode necessary for series inductor, at the output of 7805 can i use another RC filter.

people say that using an inductor in the micro controller vcc pin eliminates noise if so what value can i use whether i must use a free welling diode there i am confused about the freewheeling diode where to use.

please suggest inductor values that i can use near micro controllers and dc converter circuit

my transformer is 24v ac

 

[jiripolivka]

Read 7805 specifications: you do not need to use any inductor to filter the output, only capacitors.
Take care with your 24 V AC transformer: after a bridge rectifier the peak voltage reaches 34 V, close to 35 V allowed for 7805 input. I killed several 7800 regulators by this.
Using 12 V AC is much safer, or , add a resistor and 30 V ZEner before your 7805 regulator (the resistor must be calculated from your load current).

 

[wp100]

Hi,

Agree 100% with Jiripolivka plus at that high input voltage the 7805 will need a large heatsink to dump out all the heat generated by the large voltage loss, 34v - 5v = 29 v to dissipate as heat

 

[jiripolivka]

Yes, I agree, all depends on the load current.

 

[milad_gh]

hi .
if you want to convert 24 volt to 5 volt, it is better to use a switching regulator instead of linear regulators.
there are many reasons why:
1) because it generates a lot of heat
2) a lot of power is wasted
3) you need to use bigger transformer because you need a lot of power(which is going to waste)

mc34063 is a great chip if you do not need more than 1.5 Amps

 

[embpic]

use of 7805 is simpler and doesn't require inductor. again lm317 u can adjust it to 5 volt it also does require inductor. but
LM2576 require inductor for regulating.

 

[milad_gh]

hi.
hear is a link that suggests when to use a switching mode power supply and when a linear one:
**broken link removed**
In summary, designers use linear regulators or LDOs because they are simple, low noise, low cost, easy to use and provide fast transient response.
but otherwise it is more efficient to use switching mode power supplies.