TIDUES0F June 2019 – April 2026 TMS320F28P550SG , TMS320F28P550SJ , TMS320F28P559SG-Q1 , TMS320F28P559SJ-Q1
The closed-loop performance was done with output voltage control using Lab 3. Figure 4-50 shows the results. The drop in efficiency for lower output voltages is apparent. There are two main contributors to the drop in efficiency. First the lower efficiency for high loads is due two increasing circulating currents in the system, which increases the RMS currents and therefore conduction losses. The second contribution impacting light-load efficiency is loss of ZVS for light loads.
With extended-phase-shift (EPS) control circulating currents are reduced and the ZVS range is increased. This improves both light-load and full-load efficiency. EPS control enables this reference design to work at lower output voltages, which is not possible with single-phase-shift (SPS) due to the higher losses. A value of 10kW can be achieved down to 350V output and 5kW can be reached at 250V output voltage.