AN4070 datasheet(37/53 Pages) STMICROELECTRONICS

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AN4070

Experimental test results

Doc ID 022934 Rev 1

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Figure 25.

DC-DC converter rectifier diode waveforms

Figure 26.

Inverter modulating signals

As already mentioned, the DC-AC converter has a hybrid modulation allowing one leg to

switch at 17.4 kHz and one leg to switch at grid frequency. The image in Figure 25 is a

scope capture of the two modulating signals generated by the microcontroller and sent to

the input pin of the L6390 driver. This device is then used to generate the two

complementary signals controlling the gate of each STB11N65M5 MOSFET in the bridge.

The resulting output voltage and current waveforms are shown in Figure 27 where the

purple track is the voltage between the mid points of each leg, the blue track is the system

output voltage on the filter output and the green track is the system output current.

The efficiency of the system has been measured connecting the microinverter to a resistive

load and adapting the ohmic value of the electrical load to the desired output power level.

The open loop mode of operation allows the operating point of both the DC-DC converter

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