Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics 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

Working of TL431 Optocoupler feedback design circuit

Status
Not open for further replies.
vishnuk

vishnuk

Member level 1
Joined
Dec 8, 2017
Messages
38
Helped
1
Reputation
2
Reaction score
1
Trophy points
8
Location
Nandikkara
Activity points
297
Hi,

I am debugging one AC-DC quick charger from last week. I saw a general feedback circuit using TL431 common in all AC-DC converters.
This is what i found in my board(Please see the figure). I want to know how capacitor C1 works in this Circuit. If we dont give that capacitor C1 then we didnt get the TL431 cathode voltage regulated at 2.5. Whats the role of that capacitor
Capture.JPG
 

It’s an integrating cap used to compensate the feedback loop.

It limits the bandwidth (or response time) of the feedback loop to prevent oscillations.
 

yes here it is on page 31
Basso books talk of it too

- - - Updated - - -

also shown in ridley doc

- - - Updated - - -

yes so you can calculate your compensation pole frequency now...with 10uF and 5k1 it will be quite low....so you havbe a low frequency zero in your feedback compensation.......and having a zero kind of lifts the phase a bit so that you can cross over a bit higher and have a bit higher crossover frequency and a slightly faster power supply with a bit better transient response....you need zeros to counteract power stage poles....eg in a flyback the c(out) and load form an output pole.
 

Attachments

  • TL431_OPTO ..ONSEMI ..TND381-D.pdf
    581.2 KB · Views: 131
  • Designing with the TL431.pdf
    4.1 MB · Views: 192

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top