3 Test Results

The delayed protection scheme has been validated with the LaunchPad LAUNCHXL-F280049C. In the given example codes, changing positive_cycle to 1 or 0 to decide positive cycle or negative cycle operation; changing simulate_EPWM_Cmpa value to provide different time scale for the trip signal (EPWM8A). The test results are measured with the Kingst Logic Analyzer, as shown in Figure 3-1.

Figure 3-2 shows the condition of trip signal during positive cycle, where EPWM1A starts CBC protection right at the trip low event, while EPWM2B turns low after a delay of 1.12 µs measured. Since EPWM2B needs to follow the action of EPWM7A, the actual delay would be a bit longer than the defined value of 1 µs. Figure 3-3 shows the trip signal during negative cycle, where the delayed protection logic also works as expected.