I have designed a 5V ,350mA fixed power supply with a 12 Vrms step down transformer. the voltage across filtering capicitor should be almost peak value i.e 15V or 16V . but I am getting 12 volts acrossthe capacitor why is it so.

 

Schematic.

Is the supply loaded at 350 mA when you are measuring the voltage?

Schematic.

What is the size of the filter capacitor?

Schematic.

ak

 

YES IT IS WHEN THE CIRCUIT IS LOADED .
5500MICRO FARAD 25VOLTS

Please answer it

 

POST YOUR CIRCUIT PLEASE.

 

image

 

We mean the schematic.

 

Your question has been answered in the other forums.

 

MAY IT WORK

 

NO, you have resistors in series with the output supply, and the zener is pulling too much current through the resistors, i would use a lm7805 regulator instead of the resistors and zener.

 

SIR THIS IS OUR LAB PROJECT USING ZENER MY QUESTION IS WHY VOLTAGE DROPS ACROSS CAPACITOR THEORY BASED ANSWER NEEDED

 

Hello,

I moved your thread to the homework forum , as you stated it is a lab project.
Better read this first : PLEASE READ - Posting Questions in the Homework Help Forum
What do you think what is happening with your circuit?

Bertus

 

I have designed a 5V ,350mA fixed power supply with a 12 Vrms step down transformer. the voltage across filtering capicitor should be almost peak value i.e 15V or 16V . but I am getting 12 volts acrossthe capacitor why is it so.

The capacitor gets charged by the peaks only so the charge current is quite high. This makes the drop across the 1 ohm and the diodes higher than you think.

 

What is the average current through the 15 Ω resistor between the cap and the zener?

What fraction of the time do the diodes spend conducting?

What is the average current through the 1 Ω resistor between the bridge and the cap?

What is the average voltage drop across that 1 Ω resistor?

 

SIR THIS IS OUR LAB PROJECT USING ZENER MY QUESTION IS WHY VOLTAGE DROPS ACROSS CAPACITOR THEORY BASED ANSWER NEEDED

Typing in all caps on a forum (or e-mail) is considered the equivalent of shouting and it is also considered quite rude. Please refrain from the practice (except, of course, when your intent is to shout and be rude).