Research on High Power Density Silicon Carbide Motor Controller Based on Parallel Connection of Discrete Devices

The motor controllers for new energy vehicles are generally realized by high-power modules, but the high-power module is high cost, large volume, and limited in resources. This paper proposes a high-power density motor controller based on the parallel design of SiC MOSFET discrete devices, which maximizes material and space utilization from the perspectives of electrical and heat dissipation. In order to achieve high power density, three circular circuit boards with a minimum diameter of only 72 mm, consisting of an upper and lower three-layer structure, were used to design the control circuit, driving circuit, and power circuit. The system has a circular structure and uses the Kelvin source of SiC MOSFET to separate the power and drive circuits. The power circuit uses the power source located on the power board, and the drive circuit uses the Kelvin source located on the drive board. It can prevent the interference of the high-voltage side transient signal on the grid voltage feedback and reduce the dynamic loss, allowing for a symmetrical layout of the parallel tube power circuit to the drive circuit. In the circuit design, taking into account the area, power, heat dissipation, and other factors, the method of using magnetic components to balance the impedance characteristics of the circuit is selected to realize parallel current sharing. A high anti-interference driving circuit is proposed to dynamically equilibrium the current of parallel MOSFETs. A calculated impedance ferrite magnetic bead is connected in series behind the on and off resistors of each SiC MOSFET tube, ensuring that the parallel equivalent impedance is the same while suppressing ringing caused by rapid switching in the SiC MOSFET gate circuit. In addition, the series connection of source resistance and ferrite bead is added to the Kelvin source pole, which can further synchronize the gate signal and realize current sharing. The anti-crosstalk circuit designed using source resistance achieves dual use of one resistor, enhancing the circuit's anti-interference performance. A new design of PCB stacked busbar, suitable for parallel application of discrete devices, has been achieved with a focus on the goals of low parasitic inductance, high current, and high heat dissipation. The busbar realizes the integrated design of parallel MOSFET tubes, current sensors, discharge resistors, DC capacitors, and AC-DC terminals. When the opposite direction of current in the vertical direction has the smallest parasitic inductance on the smallest loop area and adjacent circuits have opposite current directions, the inductance decreases with the increase of the number of circuits. Accordingly, a low-noise PCB busbar with multiple sets of stacked PCBs is designed. The top and bottom layers of the busbar both have metal windows for DC and AC wiring, which can weld irregularly shaped metal sheets or strips of different thicknesses to expand the current. Hence, it meets the requirements of carrying maximum current, provides good heat dissipation, and achieves long-term operation with a maximum peak current of 120 A. Dual pulse and power experiments show that the designed discrete device parallel controller can achieve a maximum efficiency of 99.5% and a power density of 60 kW/L at the highest bus voltage of 600 V, suitable for new energy vehicle systems. © 2023 Chinese Machine Press. All rights reserved.