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Original question:

UC2842: UC2842A: UC2842A Voltage explain and Understanding the circuit.

UC2842: UC2842: UC2842A: UC2842A Voltage explain and Understanding the circuit.

SHREYAS S BAGI
Intellectual 400 points
Part Number: UC2842

Hi,

I have read datasheet of UC2842A and application circuit ( calculation ).

Questions :

1. Snubber Circuit ( RCD snubber selection ) Calculation not specified ? Please give the calculation details.

2. Is there any Simulation Model available for my Design 14 ? ( attached in this thread )

3. Explain the functionality of Qsc transistor ?

4. Explain the functionality of Q1 transistor ?

5. Explain on what range of output voltage values does the opto-isolator section switching occurs ? For example now my Vout=20V ( instead of 24V ) does the Optoisolator turns on the led ? or If Vout =24V what happens ?

6. Explain the proper frequency of switching of MOSFET ?  Is the switching frequency of MOSFET same as the f=(1.72)/(Rt*Ct)) ?

7.Is there any switching frequency for the optoisolator section ?

8.How the frequency of opto isolator section is maintaining the output voltage 24V ? 

9. Can I get these waveforms : 

     (i) Switching of MOSFET w.r.t to input voltage ?

     (ii) Waveforms of Primary and Secondary voltages w.r.t to MOSFET Switching ?

     (iii) Waveform for opto isolator switching w.r.t to MOSFET switching and also pto isolator switching w.r.t to output voltage ?

    Note: Please all the waveforms w.r.t to DESIGN 14 pdf from the Webench.5305.WBDesign14.pdf

  • 0
    TI__Mastermind 31580 points

    Hi Shreyas,

    For snubber calculations please see this snubber paper by Todd,

    TI has a power supply design library which can be found here,

    This will have lots of information on the flyback topology and how it operates.

    TI also has the power stage designer tool which will display the principle waveforms for the power stage components.

    Note the the opto-coupler is not a switching device, there are many references in google on the how the opto-coupler operates.

    The e2e forum is for specific questions relating to TI IC's or applications and it is not resourced to provide the level of design support that you are requesting.

    Regards

    Peter