TIDUEY6 April 2021
Voltage sense module is designed to provide digital feedback of inverter phase output voltages and analog feedback of DC bus voltage. All feedback signals are isolated. Digital feedback is provided by ISO7240CF-Q1 and some standard linear parts. Analog differential feedback is provided by TI's isolation amplifier AMC1311-Q1 and is based on ±480-V isolated voltage-sensing circuit with differential output. A picture of this board is shown in Figure 3-25.
AMC1311 provides a good linear performance for an input voltage range of 2 V with high source impedance. It has low offset error and drift, fixed gain of 1 with very low gain error and drift and low non-linearity and drift, and has an output bandwidth of above 200 KHz. For DC measurement, this is substantially superior.
AMC1311 requires separate power supplies for the high voltage (HOT) and low voltage (COLD) sides. Isolated power supply for the HOT side of AMC1311 is derived from one of the low side gate drive's secondary power supply (CL) and drop regulated to 3.3 V. COLD side power supply is fed in through a 4x2 connector. This module is mounted on headers J20, J23, J24, J25, J26 and J27 of the inverter mother board. Feedback signals are brought out to 4x2 connector J20 of the inverter mother board.