Current sensing wakeup time

Wall-E · ‎2013-05-06

Posted on May 06, 2013 at 15:23

Hi, I have an application where I am trying to measure accurately the inductor current in a buck converter using a TSC103 current sense amplifier. Unfortunately when the converter is in pulse frequency modulation mode, the current through the inductor falls to zero, and with ringing it can even go negative. In the Spice simulation I see a delay in the output of the amplifier when the converter switch is closed again (see attached file showing the sense resistor current and the sense amplifier output voltage).

Is this the result of a so-called waking-up effect? Is it real or an artefact of the simulation model?

Assuming it is real, can anything be done to avoid it? Do any of the current sense amplifiers support negative Vsense?

Anthony BOIMOND · ‎2013-05-07

Posted on May 07, 2013 at 10:02

Hello,

You designing a buck converter in discontinuous mode, and the TSC103 is OK to measure the inductor current in such application. My recommendation would be to insert the shunt resistor between the DC/DC converter input capacitor and the inductor, so that the voltage common-mode remains steady. Could you share more details about your application? (input voltage, output voltage, output current range...). With more details we'll be able to duplicate your simulation settings on our side.

Best regards,

Anthony