In switching mode, the power switch starts to switch to operate the active MPPT algorithm. Table 4-6 through Table 4-5 and Figure 4-5 show the test results for different power ratings and currents.

For 400W panels, set a constant output current at 9A, peak efficiency is achieved at 98.7% for power higher than 300W. At 300W output power, the converter works in buck-boost mode. At 400W output power, the converter works in boost mode, see Table 4-6. At other power points, the converter works in buck mode.

For 500W panels, set a constant output current at 12A, peak efficiency is achieved at 98.8% at 500W full load condition. At 500W output power, the converter works in buck-boost mode, see Table 4-4. At other power points, the converter works in buck mode.

For 600W panels, at 15A constant output current condition, peak efficiency is achieved at 99.0% at 600W full load, see Table 4-5. At 18A constant output current condition, peak efficiency is also achieved at 98.6% at full load. At all power points, the converter works in buck mode.

Figure 4-5 Switching Mode Efficiency

Figure 4-6 shows the switching node waveform in buck stage. Overshoot is very small and there is no obvious ringing.

Figure 4-6 No Load Switching Node Waveform, Buck Stage

Figure 4-7 Switching Node Waveform Rising Edge With Full Load, Buck Stage

Figure 4-8 Switching Node Waveform Falling Edge With Full Load, Buck Stage

Figure 4-9 shows the switching node waveform in boost stage. The waveform is also clean.

Figure 4-9 Switching Node Waveform With Full Load, Boost Stage