I've designed and built an inverting buck-boost converter, but there is a persistent ripple that occurs on both the input and output voltage waveforms, regardless of input and output capacitor sizing. I initially thought this was due to capacitor ESR, but reducing this by placing capacitors in parallel only slightly helps reduce ripple. I've tried with up to 2200uF capacitors at 100kHz. Any ideas on how to rectify this? I'm testing at a lower current than designed, so could maybe DCM be causing the voltage ripple?
Image 1 below is the converter output voltage at fsw=100kHz.
Channel 1 of image 2 is the drain-source voltage over the switch and channel 2 is the source voltage, which is an ideal DC when the converter is not connected