Gate Driver Supplies and Dead Time Management Circuits for AC to AC Converters

This paper presents an original implementation of a technique in AC-to-AC power converters to power the gate drivers of power transistors. AC-to-AC converters are well known for the complexity of their implementation due to the large number of power transistors required, many of which have different potential references. This requires a consequent number of insulated gate drivers and corresponding power supplies. Besides, MOS-MOS switching transitions (characterized by switching transitions among transistors without the introduction of freewheeling diode conduction time), typical of these converters, are complex to manage and often lead to voltage or current overshoots. The gate driver powering technique presented in this paper simplifies the global implementation of the converter as well as the management of MOS-MOS switching transitions. The proposed technique harvests energy from the power side, when this energy is available, in order to redistribute this energy to the transistor drivers. This original self-powering technique significantly simplifies the implementation of the transistor since it can be integrated within the power switch to be controlled. The immediate benefit is a reduced number of elements to be implemented, thus providing a cost-effective solution. As an additional benefit, the proposed technique simplifies the management of high-stress switching transitions. Indeed, the gate driver power supplies are designed to be sensitive to positive dv/dt, a feature that allows self-powering during the dead time of switching transitions. This leads to a reduction in both dead time duration and voltage overshoots, as validated by a practical implementation.