Bidirectional Signal and Power Co-Transmission Techniques in Isolated Gate Driver for SiC MOSFET

Traditional isolated gate drivers (IGD) rely on optical fiber (FO) and isolated power supplies to transmit IGD signals and power separately to be applied in medium- and high-voltage applications. However, this method suffers significant signal delay, large size, and high cost. Signal and power co-transmission through one isolation channel will be a potential candidate for a compact IGD. State-of-the-art approaches have the limitations of narrow signal duty-cycle range, large gate driving voltage ripples, and unachievable bidirectional signal transmission. Therefore, this paper proposes an edge-triggered time-division multiplexing IGD architecture which enables high-quality transmission of forward signal, reverse signals, and power via one isolation channel. A new pulse-edge-count modulation is employed for forward signal transmission to minimize propagation delay. The reverse signals, which are composed of fault and feedback signals of the gate driver power supply, are modulated by pulse-serial-encoding modulation. The gate driver power is modulated by pulse width modulation. A novel half-bridge DAB-LLC circuit is proposed for highly efficient signal and power co-transmission. A planar transformer with non-closed magnetic core is designed in vertically stacked structure. The parasitic capacitance (Ccp) between primary and secondary windings is only 2.2 pF. The proposed IGD achieves an ultra-compact dimension of 72 mm × 19 mm × 6 mm. At input voltage of 18 V and operation frequency of 20MHz, the output power of proposed IGD reaches 2.55 W at efficiency of 77%. An ultra-wide duty-cycle range is achieved, covering from 0% to 100%. The propagation delay of the gate driver signal is less than 85 ns. The reverse signal transmission realizes both fault protection and output voltage regulation. Experimental results also confirm that proposed IGD meets partial discharge (PD) test of 10 kVrms, with common-mode transient immunity (CMTI) > 100 V/ns.