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I'm working on half bridge mosfet gate driver using IR2184 and IRF540N mosfets. You can find circuit diagram and scope captures in images.

I have observed that there is a small spike (LC tank like output) at the gate of low side gate driver output whenever high-side gate driver output switches.

I can not upload 3 images due to smaller reputation but you can find all 3 images here

Figure 1, shows circuit diagram of half bridge driver and all the values are calculated from infineon application note AN-978. All the grounds i.e. microcontroller, gate driver, half bridge are common.

Figure 2, shows scope capture of half bridge driver. I observe surge on gate of low side driver output. This surge in turn reflects at microcontroller PWM output.

I have observed microcontroller PWM output without connecting it to driver and that PWM output is clean. From other posts like here I understand that length of power supply cable and all that forms a LC like circuit that causes this.

Then I implemented on breadboard and take utmost care that all the components have minimum distance between them as possible. After that amplitude of surge reduced to what you see in scope capture.

Then I connected RC snubber circuitry across D-S terminals of both the mosfets and RC of both the circuits is 100 kHz as maximum signal frequency in system is 32kHz PWM frequency. Scope capture of this has also reduced amplitude of surge further. But how to get rid of it completely?

Figure 3 shows scope capture after adding RC snubber to the system.

Figure 1 Figure 2 Figure 3

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  • \$\begingroup\$ Added the pictures for you. Please edit the text block to include them and break up the wall of text. \$\endgroup\$ – winny Mar 8 '17 at 11:44
  • \$\begingroup\$ Do you have any cap near supply of gate driver IC? \$\endgroup\$ – Marko Buršič Mar 8 '17 at 12:29
  • \$\begingroup\$ @MarkoBuršič No, I have not connected any cap for gate driver IC, but as answered by peufeu I'll make some changes and report results here. Thank you all for suggesting and working on edits needed for the post, I really appreciate how helpful stackexchange community is. \$\endgroup\$ – Vinay Joshi Mar 9 '17 at 3:39
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D1 (1N4001) is inadequate. This diode is for rectifying 50 Hz, not 32kHz. Please select an appropriate fast rectifier (schotty or standard, doesn't really matter, but aim for a fast recovery time).

Decoupling is insufficient. Both +36V and +12V need proper decoupling.

Power rail (+36V) needs low-ESR capacitor(s) plus MLCC for HF decoupling. Driver rail (+12V) needs MLCC as close to the chip as possible. Add aluminium cap if necessary for regulator stability.

Also, the glitch appears on the input PWM too, which means it is a measurement artifact, probably a grounding issue, either due to induction into long scope's alligator clip wire, or shared ground paths on breadboard.

Now, this is on breadboard, so you can expect poor transient behavior. Do a proper layout (we can help) and it should be OK.

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  • \$\begingroup\$ Thank you for your answer, I'll make these changes and report results here. \$\endgroup\$ – Vinay Joshi Mar 9 '17 at 3:40
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    \$\begingroup\$ With advice from peufeu I designed PCB with all the three phases and even then there was not much improvement. Then I changed gate charge resistors at HO and LO, for all the phases, to twice of their present value and it worked. I think small gate resistance was causing spikes and increasing resistance did the job by increasing RC time constant at gate of the MOSFETs and hence reducing magnitude of dv/dt changes. Results can be seen here.. Three phase output with resistive load observed is perfect. (1/2) \$\endgroup\$ – Vinay Joshi Mar 25 '17 at 6:40
  • \$\begingroup\$ But when I'm using three phases to drive BLDC motor available with me I see that there are lots of spikes at the output. I think when inductive load is dissipating energy through flyback mechanism it is causing this spikes and I need to dissipate magnetic energy due to motor coils and snubber circuits seems next logical step. Any suggestions on how to move along with snubber circuits for 3-phase inverter will be great help? Thank you all again for your help.(2/2) \$\endgroup\$ – Vinay Joshi Mar 25 '17 at 6:41

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