I hope you can trust the simulations from Qspice now. I apologize for not delving deeply into what was causing the spike in the integrator before. Regarding your PWM measurement request, I cannot recall seeing such a real-time PWM frequency and duty measurement function in other SPICE programs. However, with Qspice, I have built one here.
The challenge with this symbol is that you have to remember the time of the last rising and falling edges, and I have found a way to address this using the latch device (a native device in Qspice). If you visit my Symbol library, you will discover a vast collection of custom symbols that streamline your simulation process.
How to measure duty - QSPICE - Qorvo Tech Forum
Here is a schematic example include this Measure-PWM.qsym symbol.
Self-Oscillating Class-D amplifier - 02 - Feedback PWM Out (Single Supply) [1126].qsch (21.3 KB)
