Further to the SEPIC design I asked about in LTSpice SEPIC simulation current spikes, I have a new problem. The output voltage is OK and the inductor current waveform looks much better but the inductor current has a low frequency ringing component. (Ringing might not be quite the right term?).
The blue trace is the inductor current and the red trace is the load current toggling between 100mA and 1 Amp.
The detailed waveform of the inductor current looks OK I think.
I have tried adjusting just about every value (inductors, C4, C6 & R8) without success.
The large ringing at power on is also a worry.
I am not sure how to tune the slope compensation components (C6 R8). What should I be looking at?