Other Parts Discussed in Thread: ALLIGATOR
Tool/software:
A half-bridge circuit has been designed to drive an inductive load, with a sinusoidal pulse-width modulation (SPWM) signal controlling the switching. However, during operation, significant noise coupling into the low-voltage section has been observed when the half-bridge switches.
The circuit uses the UCC21540AQDWKRQ1, an isolated gate driver, for driving the MOSFETs. The SPWM signal is generated onboard by comparing a triangular waveform with a sinusoidal reference. Given the isolation provided by the gate driver, any disturbances on the high-side of the gate drive should ideally not affect the low-voltage section.
Despite this, common-mode (CM) noise has been detected in the low-voltage power rails (5V and 12V). The noise exhibits a frequency of greater than 45 MHz and an amplitude of approximately 3-4 V peak-to-peak. The high-side of the gate driver is powered externally, yet the issue persists.
For this test, the DC-link voltage was set to 24 VDC. The output of the half-bridge is filtered using an LC filter, resulting in the expected output: a 12 VRMS AC signal.
Please see the attached schematic for reference
The high-side MOSFET in the half-bridge is driven using a bootstrap circuit. When the gate voltage is probed with Q18 connected and Q17 not connected (NC), the observed behavior is as shown below. Could you suggest potential reasons for this behavior? Your insights would be greatly appreciated.
