I'm designing for a very power sensitive motor controller, and I'm concerned about the power that will be lost to the ESR of my decoupling capacitors. I have a prototype board as well, but there's no way to tell how much energy is being wasted within the capacitors.
With the capacitors, I expect the current draw into the board to resemble a square wave, because it's a 3-phase BLDC motor. However, with all my nice decoupling, it's become a reasonably sinusoidal wave at my PWM frequency.
Is there any way to determine how much power is being wasted in these capacitors? All of the literature I can find on it seems to be overly complex white papers. Are there rules of thumb or first order approximations I can use?
Could I also perhaps remove the capacitors, capture voltage and current waveforms, and add them back and check the difference? This approach would tell me the results for the current design, but doesn't really help in the design process.