# Need help in Making a DC_power supply...??

#### dogar sahab

Joined Mar 15, 2008
116
I need to make a 10-volt Dc-power supply..I have to make it using FULL-WAVE RECTIFIERS,TRANSFORMER,CAPACITOR FILTER,ZENER DIODES FOR REGULATION..
I want to ask that what things I should keep in mind while buying equipment for constructing circuit.For example,the current-rating of Zener diode..
I need your help in this regard.I want to know the rating of all the things used in the circuit..
thanks

#### Pich

Joined Mar 11, 2008
119
We need to know the current the power supply will provide. Is this a project that needs to be built this way or could you use a regulator?

#### Wendy

Joined Mar 24, 2008
22,146
This sounds like a homework assignment. The absolute first step is to determine the maximum current you will need, then add 10% or so. Then you look at the parts you're planning on using for your basic power supply, the transformer, diodes, and capacitor, and figure out what no load voltage is going to be, then work from there.

The experiments section of the book has a pretty good discussion of a zener regulator.

#### dogar sahab

Joined Mar 15, 2008
116
Actually,we are asked to to do the regulation using Zener diode..But the problem is that the regulation power of zener diode is not very good.Thats why it creates a lot of problems.No use of IC is allowed for voltage regulation.
No restriction of current is there that the power supply should provide.
Only voltage must be 10 volts....

#### Wendy

Joined Mar 24, 2008
22,146
Actually zeners are excellent regulators. To set up the parameters of the design you have to do what was asked though, maximum current being the first step, then establishing what the brute force power supply will provide. Once these are done, the rest is plugging in the numbers. First things first, so pick some values...

Zener regulation is backward in one way, most regulators dissipate the most heat with maximum current, while a zener does just the opposite. They can be pretty inefficient, which isn't the same thing as poor regulators.

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#### Pich

Joined Mar 11, 2008
119
You need to go back to the old days where zeners and transistors were all the rage.
You can build a good regulator with a zener by using a transistor to create a feedback loop from the output that would compensate for the pass transistor's emmiter base voltage drop.

#### Wendy

Joined Mar 24, 2008
22,146
Homework assignment, has to work within the set parameters.