Hi,

I am using the SPEEDVAL Kit Half-Bridge Motherboard (MOD-MB-HB-0900V-40A) along with the MOD-PWR-MM-C3M0060065J power card to build a synchronous buck converter.

I want to measure the drain-source current (I_ds) of the upper MOSFET. To do this, I used a current probe to measure the supply current from the DC source — specifically, the current flowing from the DC source into the +DC bus. Typically, in a buck converter, this method provides the upper MOSFET’s I_ds current.
However, with this setup, the measured waveform appears sinusoidal, as shown below.

Ch1- Upper MOSFET V_ds, Ch2- Upper MOSFET I_ds

Can I know the reason for this sinusoidal current behaviour (ch2)? Do you have any suggestions to measure the current through the upper MOSFET, directly?

Thank you!