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I find the figure which used to do the ZCD circuit. please see the below figure. Does anyone know what's name of U7? I can't find this module in SIMPLIS.

I would like to use this way to do the ZCD, but I need to know the name of this module.

enter image description here

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  • \$\begingroup\$ What are you trying to do here? We need a bit of context like the type of converter you want to simulate, the entire figure to see the rest of the circuit etc. \$\endgroup\$ Jul 28 at 18:30

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This (U7) is a monostable flip flop, sometimes called a 'one shot'. It is typically used to produce a single pulse each time it is triggered. You can be use it to debounce a mechanical switch so that only one rising and one falling edge occurs for each switch closure, or in your case to detect the zero cross point of Vds.

See datasheets for CD4098B or CD74HC221 (just two possible examples).

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  • \$\begingroup\$ Hi @Josh, Can I find this module in SIMPLIS? Do you mean I need to do it based on CD4098B or CD74HC22? \$\endgroup\$
    – Power JJ
    Jul 29 at 0:24
  • \$\begingroup\$ Those were just real world examples of the chip for reference and a broader understanding. SIMPLIS has built-in models for the four common edge-triggered Flip-Flops: D-type, S/R, J/K, and Toggle. Individual Flip-Flop documentation can be found here: simplistechnologies.com/documentation/simplis/dp_flip_flops/… \$\endgroup\$
    – Josh
    Jul 29 at 1:07
  • \$\begingroup\$ Hi Josh, Thanks. Could you please explain why we need to use this one? in my figure, why can't just connect U1 output to SR directly? \$\endgroup\$
    – Power JJ
    Jul 29 at 1:12
  • \$\begingroup\$ @PowerJJ, you could remove the OR gate. It is only necessary if you need it. It's not clear why what the purpose was in the original circuit (buffer or delay perhaps) but the zero crossing would still function. \$\endgroup\$
    – Josh
    Jul 29 at 1:31
  • \$\begingroup\$ Hi Josh, I mean do I need to add U7? \$\endgroup\$
    – Power JJ
    Jul 29 at 1:56

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