am building a 12 volt dc power supply with the following specifications:


output power- 1 watt

output voltage- 12volt

output current- 1amp

ripple factor- <1%


i need the formulas to calculate capacitance, diode, transformers and other components. i didnt get any values for the components thats why i need the formulas. plz help

thank you!

 

Hello,

Your caculation for the power is wrong.
A 12 Volts power supply that can deliver 1 A has a power of 12 Volts X 1 Ampere = 12 Watts.

Here is a simple power supply schematic from bill bowdens webpage with a LM 317.
It is capable of 1.5 Ampere.
http://ourworld.compuserve.com/homepages/Bill_Bowden/page12.htm

Greetings,
Bertus

 

that site is no help. sorry about that yes it it is 12 watts

 

Is this a school assignment or a personal project?
If it is a personal project you can use a LM7812 to regulate the output voltage.

 

Hello,

For the basics of a power supply look at the attached PDF.

More in linear powersupplies can be found in the links of this page of the EDUCYPEDIA.
http://www.educypedia.be/electronics/powerelectronicssupplies.htm

There are also circuits over there.
http://www.educypedia.be/electronics/circuitssupplies.htm

Greetings,
Bertus

 

yes it is a school assignment

 

These equations were derived by assuming the ripple voltage as a triangular wave and give approximations of the actual values.

Vr=Idc/(2*f*C)

Vr=ripple voltage peak-peak
Idc=DC current through the load
f=supply frequency
C=filter capacitance

k=Vrms/Vdc

k=ripple factor
Vrms=Vr/(2*sqrt3) rms ripple voltage
Vdc=DC voltage across the load

Vdc=1/{1+1/[4*f*C*R]}

Vdc=DC voltage across the load
C=filter capacitance
f=supply frequency
R=load resistance