# Compact 3 \(\times\) 1 Matrix Converter Module Based on the SiC Devices with Easy Expandability
## 3 Verification of the Operation  
For the proper SiC MOSFETs driving, the isolated power supply must be capable of delivering at least 1 W of the power. The output power of the isolated power supply was measured together with an output voltage as a load current function. The efficiency was calculated from the measured data. The measured data of the power supply are shown in Figure 11.  
As shown in Figure 11, the operating output power of approximately 1 W to 2 W converter reaches its maximum efficiency of around 82%. The converter can deliver more power in case if more powerful semiconductors are used. The output current is limited to 200 mA due to the used secondary rectification diode limitation. The thermal image of the one power supply during the output load of 2 W can be seen in Figure 12.  
Figure 11: Measured characteristics of the designed isolated power supply. Figure 10: Assembled module: (**a**) Side view (**b**) Top view. After the power supply efficiency and maximum load temperature, the most important indicator of the power supply quality is the output voltage waveform, especially during the startup of the power supply and dynamic events. If the overvoltage occurs during the startup, this can lead to the destruction of the semiconductor components. Thus, measuring the quality of the output waveform is important. The waveform of all of the voltages during the converter power supplies startup sequence can be seen in Figure 13.  
The Input signal represents the 12 V supply rail provided by the laboratory power supply. The 5 V rail is measured at the output of the buck converter. The Enable signal represents the signal from the supervisor circuit monitoring the 5 V rail. Finally, the Isolated signal is the voltage at the secondary side of the isolated power supply for the gate drivers. As shown in Figure 13, no overshoots are present, and the startup of the isolated power supply occurs after enabling signal when the 5 V supply rail is present and stable. For the driver functionality verification, the PWM signal was applied to the input of the driver board, and the output signal was measured at the gate of the SiC MOSFET. The measured waveforms can be seen in Figure 14.  
Figure 12: The temperature of the isolated power supply at the load of 2 W.  
Figure 13: Power supply startup sequence (Input Voltage, Blue 10 V/div; 5 V Rail, Cyan 5 V/div; Enable Signal, Purple 5 V/div; Isolated Output, Green 10 V/div). The cyan waveform in Figure 15 represents the output signal applied to the SiC MOSFET gate, where turn-off is represented by the \(-3\) V and turn-on is represented by the \(+15\) V, as was designed. In the isolated gate driver, the important parameter is the signal propagation delay from the non-isolated to the isolated side. The measured value of delay was 20 ns for the turn-on waveform and 25 ns for the turn-off waveform. These measured values correspond to the values in the driver datasheet. One important aspect of the gate driver circuitry is the stability and the response of the isolated power supply. During the turn-on and turn-off process, the major current needs to be delivered or removed from the MOSFET gate. These currents are delivered mainly from the isolated power supply capacitors, and when the switching state is stable, the capacitors are recharged. If the voltage drop during the turn-on or turn-off transients is big, this can lead to a faulty transistor switch or can cause triggering under-voltage protection in the modern gate driver ICs. In this case, the single power supply needs to deliver the required power to the two transistors since the switch is bidirectional and constructed from two SiC devices connected by the common source.