Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

Idea about Flyback circuit

Status
Not open for further replies.

nikhillife11

Member level 2
Joined
Jan 15, 2011
Messages
52
Helped
4
Reputation
8
Reaction score
3
Trophy points
1,288
Activity points
1,671
Hii all,

I need a bit of help with Flyback PSU circuit. In the image below I have marked a series resistor and capacitor in RED colour. I want to know why are they used and why the connection is from the I/p of primary of transformer to the ground of secondary winding.
Please help me to understand it better.

Thanks all.

Regards
Nikhil
 

Attachments


mtwieg

Advanced Member level 5
Joined
Jan 20, 2011
Messages
3,481
Helped
1,241
Reputation
2,488
Reaction score
1,210
Trophy points
1,393
Activity points
26,089
My guess is that it is there to protect the isolation barrier across the transformer and optocoupler. At least the high voltage rating of the capacitor implies that.

My question is what's all that other crap on the secondary side...
 

Orson Cart

Advanced Member level 3
Joined
Jun 18, 2009
Messages
800
Helped
346
Reputation
1,144
Reaction score
558
Trophy points
1,373
Location
New Zealand
Activity points
5,973
THe RC is to reduce common mode noise propagation and help meet EMC standards, the total circuit is a forward converter - it's not a flyback - and all the other "crap" is the synchronous rectifiers using 2 mosfets instead of diodes, Regards, Orson Cart.
 

nikhillife11

Member level 2
Joined
Jan 15, 2011
Messages
52
Helped
4
Reputation
8
Reaction score
3
Trophy points
1,288
Activity points
1,671
Yup Orson Cart

Your right,But can u help me with a bit of explanation that how theses capacitor and resistor in series works.. Can you give me a details knowlegde for the same please

thanks and regards
Nikhil
 

FvM

Super Moderator
Staff member
Joined
Jan 22, 2008
Messages
47,667
Helped
14,078
Reputation
28,413
Reaction score
12,742
Trophy points
1,393
Location
Bochum, Germany
Activity points
276,933
Most SMPS, e.g. off-mains power supplies are using a single small capacitor to drain RF currents injected in the transformer between primary and secondary. I guess, that the designer faced an EMI resonance peak and found the series resistor helpful to reduce it. some SMPS have a small ferrite tube at a capacitor pin to supress resonances, but it's a compomrise, also reducing the capacitor effect.
 

Status
Not open for further replies.
Toggle Sidebar

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top