Electronic circuit help (about diodes)!!!

[Sukhdeep]

Sorry...

Actually my schematic is not at all what i introduced above. I just was Learning simple Electronics behind diodes, inductors, capacitors and loads. I was just trying to understand that what will happen if i do this and that and so on. I think i have laernt a lot so far. Since i am not that good in Electronics so for be sure i asked and cleared my doubts here. I want to leaarn more like about switches and also that how the charges are moving in the Circuits.

Anyways thanks a lot so far

 

[Harald Kapp]

I didn't mean to make you feel sorry. Just wanted to express my opinion on how to design a circuit.

 

[Sukhdeep]

Thats Fine...

Attached is the schematic im working on. In the schematic i feel i used D2 and L2 correctly but someone doubted me that using L2 in this Circuit is useless and if im using L2 then i should move D2 before D1. This is something im confused about!!

 

[Harald Kapp]

D2 allows current to flow when d1 is off but the inductor still stores energy. It is the same setup as in your original post.
Moving D1 to the left of D1 would short-circuit the negative part of the input signal.

Here L2 and C4 form a low pass filter to smooth the output voltage (reduce ripple). Compare the simulation result for the voltage across R4 (Rl) with another simulation where you remove the inductor.

 

[Sukhdeep]

I already did lot of comparisons. I believe that if i remove D2, L2, C3 and just let the D1 and R4 in the Circuit then it shouls show me the results like that from halfwave rectifier, but unfortunately it dont.

If i simulate the above Circuit and look into the D1 , i see that D1 conducts during negative half of input voltage.

That person (my teacher) said that if i move D2 before D1 then the Circuit will behave like half wave rectifier . I simulated doing that too and its true.

So on Whole i feel either something is wrong in above Circuit or in the previous Circuits we discussed so far!!!!!!!!!!!CONFUSED

 

[Harald Kapp]

Upload the .asc file with the simulation you are having trouble with.

And no, your teacher is wrong. The circuit may look like a half wave rectifier seen from the output, but D2 will short circuit the source during the negative half of the input voltage and therefore overload the source. In practice it may blow a fuse... I gave you all the information (links) about the way a half wave rectifier works. I also eplained to you that D1 becomes conducting if the voltage at the node D1, D2, L1 becomes negative and that the negative voltage is a consequence of the release of the energy stored within the inductor.

Start by analyzing a simple true half wave rectifier (see the link I gave). ou don't even need a computer or simulator to understand it. USe a sheet of paper and a pencil and draw the voltages and current through the elements as a function of time. Once you have understood the basic half wave rectifier, add more components (filter capacitor, filter inductor) one by one and re-analyze the circuit's behavior over time. Adding more components to a haflf wave rectifier will change the waveforms of voltages and currents. t does not, however, change the basic operating principle of the rectifier. And none of the rectifiers I've seen in my life has had D2 in place.

The circuit around D1, D2, L1 and C4 is typically used for step-down regulators (where D1 is replaced by a switch or transistor), not for rectifiers.

 

[Sukhdeep]

Hi,

Here is the .asc file in the Attached folder. Kindly have a look . In theschematic i put D1 and D2 . Keeping D1 and deleting D2 gives different results than that of when both are kept in the circuit. Also keeping only D1 looks like Halfwave rectifier but it dont behave as halfwave rectifier.

Can you please help me understand what exactly is going on here.

Thanks

 

[Harald Kapp]

Of course the behavior will differ. With D2, Vp1 cannot go negative to more than ~0.6V, this is where D2 starts conductig. Without D2, Vp1 can reach large negative values.
Also your circuit has a connection between the upper sub-circuit (V1 etc.) and the lower sub-circuit (V2 etc.)

Look at the much simplified version of the simulation (appended).

 

[Sukhdeep]

But what will be path of the current flow when D1 is off and D2 is conducting? wnt it overload the Source this way?

 

[Harald Kapp]

But what will be path of the current flow when D1 is off and D2 is conducting? wnt it overload the Source this way?

That's what I tried to tell you in my post #10 and again in #24 when I wrote that the input will be "shorted" or "short circuited". And that's why you don't use D2 for a half wave rectifier.