# Compact 3 \(\times\) 1 Matrix Converter Module Based on the SiC Devices with Easy Expandability
## 2 Structure of the Module
The SiC transistors offering a high blocking voltage together with a low \(\text{R}_{\text{DS(on)}}\) in comparison with traditional MOSFET technology. To ensure the short signal traces to the SiC MOSFET Gate pin, the driver board is placed right above the power board. The signals are transferred through the connectors. Since the input of the converter is connected to the phase voltage and a common source of transistors floats at the high voltage potentials, the isolated gate driver is needed. For the proper supply of the secondary side of the driver, the isolated push-pull power supply is designed based on the SN6505 push-pull driver to ensure a small form factor. The secondary voltage from the power supply is 18.5 V, and this voltage is further divided into +15.5 V and \(-\)3 V to ensure proper driving of the SiC power MOSFETs. For the gate driving, the dual isolated gate driver for the H-bridge applications was used. The secondary side of this driver was designed that way so that this driver can drive two transistors connected with a common source. The driver is capable of sourcing 4 A and sinking 6 A to each MOSFET. For proper SiC driving and ensuring that the driver is not overloaded by the current, the proper external gate resistors must be selected as shown in Figure 6. The following driving configuration was selected to ensure faster gate discharge and thus faster turn off times:  
Figure 4: Design of the power IMS board. Figure 5: The 3D model of the power board. During the turn-on, only the \(R_{ON}\) resistor applies, since diode \(D\) is in the blocking direction. In the turn-off time, the diode is in the conducting stage and the resistors are connected in parallel, which allows reaching a higher discharge current. The resistors were selected as follows: \(R_{ON}\) = 4.1 \(\Omega\) and \(R_{OFF}\) = 2.8 \(\Omega\). Then, the current capacity of the driver needs to be checked [25]:  
\[I_{POS\_MAX}=\frac{V_{DD}-V_{SS}}{\frac{R_{N_{max}}R_{OH}}{R_{N_{min}}+R_{OH}}+R _{ON}+R_{FETin}} \tag{1}\]  
\[I_{NEG\_MAX}=\frac{V_{DD}-V_{SS}-V_{D}}{R_{OL}+\frac{R_{ON}-R_{OFF}}{R_{ON}+R_{ OFF}}+R_{FETin}} \tag{2}\]  
where \(R_{OH}\) and \(R_{OL}\) represent internal driver driving MOSFETs resistances, \(R_{Nmos}\) is internal pull-up driving resistor, and \(R_{ON}\), \(R_{OFF}\), and \(R_{FETin}\) represent the turn-on, turn-off, and SiC internal resistors, respectively, according to the SiC datasheet. Diode forward voltage is represented by \(V_{D}\) and supply voltages are denoted in \(V_{DD}\) for positive rail and \(V_{SS}\) for negative rail. The calculated values from (1) and (2) must be lower than 4 A for turn-on current (\(I_{POS\_MAX}\)) and lower than 6 A for turn-off current (\(I_{NEG\_MAX}\)) according to datasheet [25], to ensure that driver is not overloaded. In our case, the calculated results are 2.9 A and 5.2 A for \(I_{POS\_MAX}\) and \(I_{NEG\_MAX}\), respectively. Calculated values are below the maximum values specified by the datasheet [25] which confirms the correctness of the design. All circuitry in the driver board is powered from the single 5 V power supply. The board includes a voltage supervisor IC, which ensures the power supplies startup when the supply voltage reaches 4.7 V by enabling the drivers to prevent current inrush. Together with isolated power supplies and isolated gate drivers, the current measurement was implemented on this board. Current measurement is implemented on the driver board (Top PCB). The OUT pin shown in Figures 4 and 5 is used to conduct current from the power board to the driver board. Then, the current is flowing through the hall current sensor and then to the output phase pin shown in Figure 7. The sensor can measure current in the range of \(\pm\) 20 A, which is suitable for this application, even if the SiC devices would be changed for more powerful ones. If the output current would be bigger, the manufacturer of the sensor offers a \(\pm\) 30 A version in the same package, which can be easily changed if more output power is needed.