I'm designing a type of a buck converter which has the following circuitry.

enter image description here

Simulation runs fine on PLECS and I've added three bootstrap connections to drive these high-side MOSFETs (All top three except FETD2). Simulation results to capture voltages across those capacitors is as follows;

Voltages across Bootstrap Capacitors

I have following questions to clarify before I build this circuit on a PCB.

  1. Is the voltage between each gate to source is enough to drive each MOSFET (Probably a Logic type MOSFET)?
  2. In simulation, when I use the same 12V source to bootstrap circuit, it throws an error "Cyclic behavior during switching". But when I use a separate source as in the schematic, it works fine. Can't I really use the same source for all bootstrap connections?

    enter code here

  3. Also the PWM frequency needs to be at 1 MHz. Has anyone used a driver circuit which can work at such high frequencies and got good results?

Thanks in advance :)

  • 2
    \$\begingroup\$ This will fail due to lack of dead time Design and latency from the PWM inverter and times five gain. \$\endgroup\$ Jun 16, 2018 at 18:11
  • \$\begingroup\$ Hello @TonyStewartolderthandirt ! Will I be able to get a considerable amount of dead-time with the operating frequency of 1MHz? Is Bootstrapping the best way in my design? \$\endgroup\$
    – Padmal
    Jun 17, 2018 at 5:10
  • \$\begingroup\$ No your boostrapping looks wrong and makes no sense. Normally Low side switch has PWM to drive Diode cap to make bootstrap voltage for high side gate drive. \$\endgroup\$ Jun 17, 2018 at 5:28
  • \$\begingroup\$ Isn't the idea of having a bootstrap connection to always supply a higher voltage at gate terminals with respect to each source terminal? If I don't call this a bootstrap, then would it work? \$\endgroup\$
    – Padmal
    Jun 17, 2018 at 14:14
  • \$\begingroup\$ Yes wth Vgs > 2.5 Vt but how is in my reply above and no \$\endgroup\$ Jun 17, 2018 at 15:05


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