Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

5v power supply without ripples

Status
Not open for further replies.

raman00084

Full Member level 6
Joined
Nov 29, 2010
Messages
350
Helped
2
Reputation
4
Reaction score
2
Trophy points
1,298
Activity points
3,930
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

Advanced Member level 5
Joined
May 21, 2010
Messages
2,832
Helped
831
Reputation
1,660
Reaction score
802
Trophy points
1,393
Location
Santa Barbara
Activity points
22,012
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

Advanced Member level 5
Joined
May 15, 2009
Messages
3,056
Helped
883
Reputation
1,781
Reaction score
736
Trophy points
113
Location
Prime Meridian
Activity points
0
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
 

milad_gh

Newbie level 3
Joined
May 21, 2014
Messages
3
Helped
2
Reputation
4
Reaction score
2
Trophy points
3
Activity points
42
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

Advanced Member level 3
Joined
May 29, 2013
Messages
742
Helped
80
Reputation
160
Reaction score
77
Trophy points
1,308
Location
india
Activity points
5,213
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

Newbie level 3
Joined
May 21, 2014
Messages
3
Helped
2
Reputation
4
Reaction score
2
Trophy points
3
Activity points
42

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top