On the Implementation of “Dead Time” in a Synchronous Step-Down Converter

The paper investigates and addresses the “dead time” of a synchronous step-down converter implemented with P-channel and N-channel transistors. The transistors are controlled by a single driver, and “dead time” is implemented with external circuits and Schottky diodes. The influence of the Schottky diode capacitance on “dead time” is considered. Mathematical expressions were derived, showing the ratio of the value of this capacitance to the input capacitance of the transistor and the influence of this ratio on the shape of the leading edge of the pulse for switching on the transistor. The results of computer simulations are given for different ratios of the two capacitances. It was found that the capacitance of the Schottky diode must be much lower than the input capacitance of the transistor. The results of the mathematical description and computer simulations were used to select a suitable transistor and Schottky diode and are applied in the subsequent practical implementation. Conclusions and recommendations were made for a synchronous step-down converter, as well as for other cases of implementing “dead time” in the manner considered.