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Why signal from secondary output is not equal on the positive and negative side like as in the second image?

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  • \$\begingroup\$ Do you mean duty cycle or voltage level? \$\endgroup\$
    – Ralph
    Mar 15, 2022 at 18:15
  • \$\begingroup\$ Voltage level is not equal on positive and negative ( mid on 0v ). Thnx :) \$\endgroup\$
    – Miau
    Mar 15, 2022 at 18:19

3 Answers 3

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Vsecondary is shifted down -1V or so due to the "forward" drop of D2.

If D2 were perfect, there would be no shift and the traces would match.

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You will see both the voltages same if you measure the primary and secondary voltage of the coupled inductors, here you have measured primary as the Vds of the switch. So after the switch has turned off from ON position the freewheeling diode comes into picture and the 0.7V drop adds up to the 5V showing around 5.7V when switch is off and when the switch is ON the 0 seems to be I *Rdson. From next time please ensure for the measurements, probe exactly what u need to be probe. Use differential measurements in LTSPICE to avoid such confusions where the measurement has been done wrt ground. Cheers!

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Voltage level is only a matter of reference. Setting the reference point 2.5 volts higher or middle of the secondary coil would yield the values you are looking for.

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