Hello, in the datasheet of TPS40090/1 there are three proposed methods of sensing the inductor currents: Resistive, DCR and thermally-compensated DCR. My problem is that I can not use any of these methods in my design. I am designing a four-phase buck-type power supply which uses tapped inductors. The converter works in the boundary conduction mode. Since the output voltage of the converter is far above 5V, which is maximum common-mode voltage at current sense inputs, resistive and DCR methods are not possible. So my idea is to use HF current transformers. But since the buck inductors are tapped, there is a sharp step in the waveform: If I put the current transformers at the input winding, I get zero current-sense voltage past the high-side switch turns off. If I sense the output current, I get a step upwards, as the low-side switch, connected to the tap, starts conducting.
But in both cases, the current waveform while high-side mosfet is on, is as it would be in case of resistive or DCR sensing. I think that the important point in the waveform is just before the high-side switch turns off, as the converter employs a peak-current control scheme. So I think using the current transformers would be okay. Can you confirm this?
Thanks in advance. Matej
