8.2.1 Voltage Sensing

ΔΣ modulators are widely used in frequency inverter designs because of their high AC and DC performance. Frequency inverters are critical parts of industrial motor drives, photovoltaic inverters (string and central inverters), uninterruptible power supplies (UPS), and other industrial applications.

Figure 45 shows a simplified schematic of a motor drive application with the AMC1035 used for the DC-link and output phase voltage sensing. In this example, all resistive dividers reference to the negative DC-link voltage that is also used as a ground reference point for the microcontroller. An additional fifth AMC1035 can be used for temperature sensing of the insulated-gate bipolar transistor (IGBT) module; see the IGBT Temperature Sensing section for more details.

Current feedback is performed with shunt resistors (R_SHUNT) and TI's AMC1306M25 isolated modulators. Depending on the system design, either all three or only two motor phase currents are sensed.

Depending on the overall digital processing power requirements and with a total of eight ΔΣ modulator bitstreams to be processed by the MCU, a derivate from either the low-cost single-core TMS320F2807x or the dual-core TMS320F2837x families can be used in this application.

Figure 45. The AMC1035 in a Frequency Inverter Application