Are these two circuits equal?

[Shahriar]

Hi

Are the outputs of these two circuits different or they are the same if Vin is 12VDC with some noises (i.e. from an Ignition Motor)

L1 and L2 are completely seperate and wounded on different cores!

ThanX
Shahriar

View attachment 40925

 

[audioguru2]

The regulators are missing important input and output capacitors that might resonate with the inductors.

 

[Shahriar]

Dear audioguru

Ok, put two caps around the regulator; Not important for this question! 

I just mean what would happen for the output if we change the Inductors position?

ThanX
shahriar

 

[audioguru2]

The datasheets for the regulators show capacitors to keep them from oscillating,  not inductors. Their error amplifier has a high gain to keep the output voltage from changing.
A regulator that works properly regulates its output voltage so inductors are not required.

 

[Shahriar]

Dear audioguru

when you are to power an MCU based or a sensitive device from an iginition power supply, i.e. when connecting your circuit to a Car, because of high transient voltage (upto 60v) you can not just use
7805 and some capacitors;
if you search between the car CD players you can always see an inductor around 800uH before the regulator and some caps around it; without this inductor, you will have crash!

now if you are conviced, can you tell me Do those two circuits (I attached) differs?

thanX
Shahriar

 

[gogo2520]

Hello Shahriar
    Just to keep it simple Yes there different, One has one inductor and the other has two. Witch is obvious, Your question isn't.
                                                  gogo

 

[audioguru2]

I think that if you are going to use a voltage regulator in a car then you should use one that is designed to be used in a car.
I use the little LM2931 but there are many others and some are bigger with higher power dissipation and current ratings.

View attachment 40930

 

[Shahriar]

Hi

I didn't know there are such regulators on the market! :
I will definitely use them in future

thanX
Shahriar