circuit description for 2 switch forward converter.

[arr_baobao]

can someone help me with this 2 switch forward converter.
i need someone to explain to me how the part of the circuitry in red box works.
i know it is a power factor correction circuitry but i don't know how it works.
any expert here can enlighten me?
thanks!

 

[goldsmith]

Dear arr_baobao
Hi
I don't think it is a PFC! it can be kind of EMI filter .
Best Wishes
Goldsmith

 

[arr_baobao]

need more info on this....
expert please....

 

[goldsmith]

About EMI filter ? if my prediction is correct , and if that is kind of EMI filter : as you probably know the waveform of current is has some high frequency components . these components can go into the supply of each stuff that connected to the common power line ! such as radio or TV or refrigerator or ... etc . it can destroy correct behavior of them ! so this filter needed to don't allow those harmonics , to go through the power line , and it will just allow the main voltage to get in !

 

[arr_baobao]

no... i dont think it's a emi filter. as the emi filter is the square box on the bottom left. i pretty sure it's a pfc/input current shaper to reduce the harmonics content after the non linear component (full bridge rectifier.) and the L3 is the reset winding from the transformer. i just need to know the these pfc/input current shaper works. and also the function of the bulk capacitor c1 (if not mistaken) in the circuit.

thanks

 

[goldsmith]

But i have some doubts about that it is a PFC . because a pfc will build with a boost converter . for example when you have an H bridge you can use kind of boost converter and a line filter , this the current and voltage will be the same . but i suspect that when both switches are on , this circuit with input inductor can make a boost converter . but i don't know why it didn't use any line filter ? each PFC need a line filter too . and of course if it is a PFC it has not any feedback . i didn't see circuits such as this until now . hence i'm not sure about it's action . perhaps other ones saw circuits such as that , thus they can help .
Good luck
Goldsmith

 

[FvM]

To work as a PFC, the circuit must be able to reduce the odd mains frequency harmonics (150, 250, 350 Hz etc.). By circuit LC parameters, this is hardly possible. There may be a certain effect in combination with a PFC like operation of the inverter itself, but if so, it won't be seen with the constant duty cycle control in your simulation.

I think, it's your job to give "more info on this":
- where did you get the circuit
- what's said about PFC operation or other circuit poperties

 

[grizedale]

Categorically

That is not a PFC circuit.

Also, that circuit has a negligible effect in reducing mains harmonics.

Can you show the rest of the circuit.
Can you provide the .asc file in .txt for us, so we can run it and see what the circuit does, with and without that unusual combo of L and C.

The only passive PFC circuit arund is the Valley-filler.................or , of course , a passive pfc using L and C.but the L and C would be ENORMOUSSSSS !!!

 

[iepower]

This is not a complete PFC circuit.
it should be a PFC circuit with a zero ripple current technique
for details about zero ripple technique please look at the article "a zero ripple technique applicable to any dc converter"

 

[grizedale]

this is not a comlete PFC circuit.

-its nothing like a pfc circuit.

Youve got 470uF after the diode bridge..........who told you it was a pfc circuit.?......................or which book told you?

Is this an audio amplifier power supply.........well in that case, you dont need pfc in most cases.

 

[mtwieg]

It can't be a PFC circuit, at least not an effective one. Choked passive PFCs require many mH, not uH of inductance to be effective.

As has been suggested it is likely an EMI filter, though a strange one. It is likely tuned to the specific switching frequency of the converter.

 

[goldsmith]

Hi again
I think if the original poster , mention that where this circuit is derived from , and show us the reference of it , it can helps . because it is pretty unusual circuit .
Regards
Goldsmith

 

[FvM]

This is not a complete PFC circuit.
it should be a PFC circuit with a zero ripple current technique

I fear, you are missing the point. "Zero ripple" technique is a kind of filter. It hasn't been doubted that the circuit can work as a filter, but where is the PFC function?

 

[arr_baobao]

it's a circuit for power supply for telecom equitment. i get it from my friend. the circuit design by his lecture and i cnt get in touch with her lecture and my friend dont knw how the circuit works.

btw can anyone tell me what the function of L-C filter in the output side? and how it works?

 

[goldsmith]

t's a circuit for power supply for telecom equitment. i get it from my friend. the circuit design by his lecture and i cnt get in touch with her lecture and my friend dont knw how the circuit works.

You should mention it at first !
If so , i think this supply have been used in some sections of a transmitter , ( probably ) thus that filter is to prevent from interferences of main harmonic of that transmitter .
Best Luck
Goldsmith

 

[arr_baobao]

You should mention it at first !
If so , i think this supply have been used in some sections of a transmitter , ( probably ) thus that filter is to prevent from interferences of main harmonic of that transmitter .
Best Luck
Goldsmith

so the circuitry in that red box is pfc? can u explain to me how its work?
i just get reply from other thread that the pfc might work together with input-current shaper, and the project did mention about the inpur current shaper.
so can anyone comfirm with me is that pfc with input current shaper ? and how this part of the circuitry works

thanks a lot for helping

much appreciated

 

[goldsmith]

Recall , it is not a PFC . it is kind of RF filter .

 

[arr_baobao]

can u tell how its work?

- - - Updated - - -

can u tell how its work?

 

[goldsmith]

i think it is obvious . this filter won't allow the unwanted harmonics to go in and go out through the circuit .

 

[arr_baobao]

but how the circuit operate? what the function of the L4(inductor), D1 (diode), and C1 (capacitor).
how they work tgt and perform those function.

thanks

- - - Updated - - -

but how the circuit operate? what the function of the L4(inductor), D1 (diode), and C1 (capacitor).
how they work tgt and perform those function.

thanks