4 Isolated Modulators in Traction Inverters

Figure 4-1 shows an implementation of an isolated-modulator-based design in automotive traction inverters.

Traction inverters have a direct influence on the driving experience and require precise control of speed and torque of the traction motor. A shunt coupled with an isolated delta-sigma modulator provides the highest-quality feedback signals to the controller to establish the pulse-width modulation (PWM) pattern for bridge transistors. The digital filter implementation allows the engineer to tune the quality of traction motor controls.

As shown in Figure 3-1, the FPGA, MCU, and DSP can have multiple digital filters running in parallel. One of the digital filters can be a high-performance digital filter that provides accurate feedback signals to control the bridge transistors. Another digital filter can be a low-latency digital filter for detecting overload or overcurrent conditions. A third-order (sinc³) filter with a different OSR can be used for both digital filters.