AN4070 datasheet(35/53 Pages) STMICROELECTRONICS

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AN4070

Experimental test results

Doc ID 022934 Rev 1

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Experimental test results

The typical voltage and current waveforms of both the DC-DC and DC-AC converter are

shown in this section. In particular, Figure 22 shows the characteristic waveforms of the DC-

DC converter MOSFETs, namely the drain to source MOSFET current (green track) and

voltage (purple track).

Figure 22.

DC-DC converter MOSFET current (green) and drain to source voltage

(purple) @250 W

The transformer leakage inductance is the cause of the peak on the drain to source voltage

at turn-off. This peak has a maximum value of 89 V, which was recorded when the

microinverter was operating at 250 W of output power with an input voltage of 30 V.

Figure 23 shows the current flowing through each of the two input inductors and the effect of

current ripple cancellation that the interleaving has on the converter input current (blue

track) when the system is operating at 30 V input and 250 W output power.

The HF transformer main waveforms are reported in Figure 24, where the purple track is the

transformer input voltage, the blue track is the transformer secondary voltage and the yellow

track is the primary winding current. It is worth noting that the secondary voltage is only half

of the total output voltage due to the presence of a voltage doubler connected downstream

of the secondary winding. The current and voltage waveforms across one of the two rectifier

diodes are shown in Figure 25.

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