3.1.2.4.2 INCR_BUILD 1.2: Open Loop, DC (Valley Switching Validation Under Open Loop)

The objective of this exercise is to evaluate the valley switching under open loop with DC input.

1. Open the main.syscfg file by double-clicking on the filename in the Project window. Under Project Options, select Open Loop as the INCR_BUILD option (see Figure 17). Select the Single-phase PFC and the valley switching options should be automatically set to valley switching enabled. This enables valley switching under Build 1. Rebuild the project if there are any changes in the solution_settings.h.
2. Open the solution_settings.h file. Notice that the incremental build (INCR_BUILD) option is set to "1" (Build 1) and the INTERLEAVE option is set to "1" (valley switching control is enabled). If not, go back to step 1 to make sure the setting is correct.
3. "Turn on" the 12-V DC bench power supply. Click the Debug button or click Run → Debug from the menu. Once complete, the Build 1 code should compile and load.
4. Repeat ^{step 1} through ^{step 4} in Section 3.1.2.4.1.5 for real-time emulation and to continuously refresh.
5. Probe the drain-to-source voltages for the phase 1 using appropriately-rated voltage probes and oscilloscopes.
6. Set the resistive load to 4 kΩ.
7. Run the code by using the <F8> key or by using the Run button () on the toolbar.
8. The dutyPU parameter should be automatically set to 0.2 initially. Verify channel A of the PWM1 module maintains the output and that channel B is disabled.
9. "Turn on" the power supply and gradually increase the voltage to 100 V. This will increase the output to approximately 220 V.
10. Using the oscilloscope, observe the Vds voltage waveform . The MOSFET (Q1) should be "turned on" at the valley point of Vds (see Figure 18).
11. Inspect the values in the valley switching-related registers (that is, DCFCTL, VCAPCTL, and VCNTCFG). For more information on these registers and the associated values, refer to the Valley Switching Application Report and TMS320F28004x Piccolo Microcontrollers Technical Reference Manual .