UCC28056: How to measure the bode plot

Hi Red,

Thanks for your interest in UCC28056. Typically the bode plot is measured by inserting a small resistance at the toop of the VOSNS divider (R14 in the UCC28056EVM). An oscillating signal is injected at TP13 and the small signal response is measured at TP12. This application note provides further detail for measuring loop response for power supplies:www.ti.com/.../slup386.pdf.

Please keep in mind that a PFC stage will typically have very low bandwidth (<10Hz or so). Also keep in mind that there is inherently output voltage ripple at twice the line frequency in a PFC stage. This is not from instability but from the PFC matching the input current waveform to the input voltage waveform.

Best Regards,
Ben Lough