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I need to drive MOSFETs for a 3 phase 3 level inverter circuit. I have thought of two methods to design the circuit. I want to know which of the two methods will work the best in terms of noise immunity, rise and fall time of PWM, and other problems that might play here.

Following are the parameters:

  • 20 KHz to 40 KHz switching frequency
  • 3.3V PWM from microcontroller
  • 12V PWM MOSFET driver output
  • 3 phase AC inverter output

The main difference the two methods have is that method 1 has two connectors with 3.3V PWM on long wires of length 0.5m to 1m while the second method has one connector and 12V PWM on long wires with the same length.

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  • \$\begingroup\$ Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. \$\endgroup\$
    – Community Bot
    Nov 8, 2021 at 8:24
  • \$\begingroup\$ Do you care about emissions interference with USB? acoustic step effects from high Q and L/RC resonance, losses and added complexity of suppression or matching source impedances to cable and losses. None of the Answers have focused on specs \$\endgroup\$ Nov 8, 2021 at 15:26
  • \$\begingroup\$ @TonyStewartEE75 That's because there is no specification of cable type nor the logic levels of the MCU, & gate driver. A buffer/driver could be a line driver w/ impedance match & twisted pair, or simple CMOS buffer & ribbon cable, It would require some more detailed view. \$\endgroup\$ Nov 8, 2021 at 17:07
  • \$\begingroup\$ @MarkoBuršič That's my point. no answer is valid or correct without specs. \$\endgroup\$ Nov 8, 2021 at 23:02
  • \$\begingroup\$ Let me be perfectly clear. Both methods work better if you match source impedance with compromises if you do not. Method 1 is lower power with less energy being transferred over a longer distance, but NO ANSWER IS ACCEPTABLE UNTIL YOU DEFINE ALL YOUR SPECS, which is a question you must learn to define. The options are simple with match driver impedances, but your awareness to thermal, acoustic , EMI issues and stepper resonance. Must be defined. Technically NEITHER OF THESE 2 CHOICES ARE BEST. Been there done that. Got it? \$\endgroup\$ Nov 8, 2021 at 23:27

3 Answers 3

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Always bring the gate driver as close as possible to the MOSFET and minimize the gate drive current loop.

The digital signal being sent to the gate driver is less critical. Good layout practice helps here, too, of course. So best is to use a good return current concept, e.g. microstrip and properly terminate it if you have a strong drive controller that is capable of fast rise times.

If you have to pass that signal through a cable, put a ground conductor alongside with it in the same cable.

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The 1st Method, of course. The gate driver has to be as close as possible to the MOSFET gate, the trace inductance plays a very important role, here.

The MCUs output could be enough or maybe not, for a such long cable it could be also good to have a high speed buffer/driver.

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In addition to what was already said, even if you get your "Method 2" device working, having a 1m long cables carrying 0-20V signals with microsecond-long edges will be a HUGE challenge to get FCC (or your local equivalent) certification for.

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