Dynamic Optimum Dead Time in Piezoelectric Transformer-Based Switch-Mode Power Supplies

Abstract

Abstract-Soft switching is required to attain high efficiency in high-frequency power converters. Piezoelectric transformerbased converters can benefit from soft switching in terms of significantly diminished switching losses and stresses. Adequate dead time is needed in order to deliver sufficient energy to charge and discharge the input capacitance of piezoelectric transformers in order to achieve zero-voltage switching. This paper proposes a method for detecting the optimum dead time in piezoelectric transformer-based switch-mode power supplies. The provision of sufficient dead time in every cycle of the switching period results in the quick start up of resonant current inside the transformer. The new method is implemented by dynamically detecting the optimum dead time for each resonant cycle and results in reduced energy loss, and consequently, increased efficiency in the converter during initialization time and steady-state operation. The theory of optimum dead time operation is also discussed in this paper. Experimental results and simulation are provided to show the implementation of the concept.

Analysis and Design of a Charge-Pump-Based Resonant AC–DC Converter With Inherent PFC Capability

“…Accordingly, the actual contribution of the reverse conduction loss to the total power loss is of less concern. For achieving the best efficiency across line and load ranges, an adaptive dead-time adjustment circuit can be incorporated [45]. A less-effective but lower-cost method to alleviate that effect is through the incorporation of a larger capacitor C DC , which results in reduced ripple across the DC capacitor and half-bridge, see (19).…”

Analysis and Design of a Resonant Power Converter With a Wide Input Voltage Range for AC/DC Applications

“…18: Measured values for converter input resistance relative to target values. switching frequency to the values used in the measurements, with the converter being operational when the input voltage exceeds 60 V. Using an adaptive dead-time control technique [40], the duty cycle can be adjusted accordingly such that zero-voltage switching is ensured along the line cycle. From the waveforms in fig.…”

Optimum Phase Shift in the Self-Oscillating Loop for Piezoelectric-Transformer-Based Power Converters

“…One is that phase angle of the entire loop should be an integer multiple of 360°; the other requirement is that the loop gain should be greater than unity to start-up oscillation. This criterion is the Barkhausen oscillation criterion for feedback systems and is essentially a simplified and less mathematically rigorous loop-gain method for attaining self-oscillation, compared to the harmonic balance approach [29], [30]. Its attractiveness lies within its simplicity, even though its conditions are not sufficient to ensure self-oscillation in all possible operating conditions.…”