Hello all,

I'm designing my first half bridge boost converter and I've got these two problems:

1. These transients that appear no matter what simulation model of MOSFET I use. I've got these massive spikes. They even appear when I insert larger diodes onto the MOSFETs. Is this an artifact of the simulation? 10 ns step time and a 2 ms simulation, if it helps. I've heard that switching mode converters are hard to simulate.
2. My output voltage doesn't have any ripple. My professor pointed this out to me. Upon further thinking, this isn't a traditional boost converter I'm used to working with. The output follows the Phase pin output when high. I don't think I'm supposed to have an output ripple. I've attached the driver I'm using. I can't find any examples of the output voltage of this sort of converter online to confirm my second point.

Any help would be appreciated

 

Why R10 0.1 ohm?
It looks like you have both MOSFETs on for a short time. There should be 250nS of delay to stop shoot through.
look at the Gare current of both MOSFETs. (or the current in the Gare resistor) You should see the turn off of one FET then 250nS later the turn on of the other. Or you could look at G-S voltage of the two.

Part of the ripple is R11. There might be ESR in the capacitor. Check it values. You might have another 0.1 ohm there.

 

Part of the ripple is R11. There might be ESR in the capacitor. Check it values. You might have another 0.1 ohm there.

That was exactly it! Removing this resistor fixed most of the transients!

I looked into proper sizing of a bootstrap capacitor and I realized mine was way oversized. I toned it down in accordance with the drain-source capacitance. Shrinking it allowed some delay between Ugate and Lgate and fixed the rest of the transients. There was still the issue of the lack of a triangle waveform, but shrinking the output capacitor as well as removing the chip resistor to ground allowed me to get a true output voltage ripple.

C1= 4 uF and C3 = 1.5 nF fixed my problem.

Thank you!

 

What SPICE are you using?

 

KiCad, so ngspice.