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This paper studies the impact of disc-shaped piezoelectric resonator dimensions on a non-isolated inductorless piezoelectric DC-DC converter. An analytical model, linking geometrical parameters to output power and efficiency is introduced. This later reveals the benefits of reducing the thickness and diameter of the piezoelectric disk. Five piezoelectric discs with different dimensions are tested and compared in experimental works, giving very high efficiency up to 98 % and output power up to 1.7 W. An exceptional power density of 366 W.cm-3 was measured at 450 kHz for a 25-30 Volt conversion with an efficiency of 81%.

With the growth in demand for miniaturization in power electronics, the current solutions are starting to display their limits in dimensions, power densities and efficiency. To meet the previous demands, the new piezoelectric materials achieving high power densities and efficiency could be the solution to ensuring the requirements. The piezoelectric resonators (PRs) and the piezoelectric transformers (PTs) have been used previously. Unlike the PTs, the use of PRs in power electronics has not been fully explored, and their use has been limited to operating as switched capacitors. However, a new operating principle using PRs based on energy and electrical balance exhibits good performances in steady state. In this paper, our motivation is to investigate in the capability to control a dc-dc converter based on PRs using this operating principle. Indeed, this paper presents the control strategy of a new step-down DC-DC converter based on a piezoelectric resonator (PR), which is used as an energy storage element. The operating principle of the converter is also presented. Moreover, the control algorithm has been implemented in field programmable gate array (FPGA) to regulate the output voltage. The control principle is validated experimentally for input-output voltages 120-48 V, and achieving an efficiency up to 94% for large operating power range.

The emergence of new piezoelectric materials makes it possible to offer high performances in terms of power densities and integration. These new materials can be used in DC-DC power converters as solution to replace the magnetic components and to meet the growth in demand of miniaturization, high power densities and high efficiency applications. This paper deals with a new topology of a DC-DC converter based on piezoelectric resonator. The conversion mechanism, based on energy and charge balance, is explained in details through an analytical model and validated by experimental results. A prototype has been designed for an input-output voltage up to 250-125 V and a power range of 100 W. It provides an efficiency higher than 93% for wide operating points in radial mode vibration. As an example, we obtain an efficiency 93.8 % of for 250 -117 V input-output voltage at 50 W output power. In addition, the thickness mode operation is experimentally validated at 1 MHz, and exhibited a peak output power of 175 W with an efficiency of 80 % for 200 -60 V inputoutput voltage. The experimental results show the promising performances of the proposed DC-DC power converter based on piezoelectric resonator for high-to-low voltage, high efficiency and low-to-medium power applications.

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Piezoelectric DC-DC converters operate between the series and parallel frequencies of the piezoelectric resonator to achieve soft switching and energy-balance conditions. This letter presents an experimentally validated model to accurately predict the operating frequency, the switching angles and the piezoelectric current for any 6-phases piezoelectric DC-DC converter. This model reduces the transient simulation's calculation time to reach steady state. It can be used to initially setup the switching angles in experiment, or to predict the high frequency spectrum generated by the converter cycle.