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this paper proposes a new method eliminating external effect from (load, temperature) variation on a Piezoelectric Transformer (PT) converter by utilizing the phase-locked loop (PLL) modulation technique. The PLL control scheme involves detecting phase difference between injected sinusoidal signal and demodulated terminal voltage of PT. Generally, frequency control method decreases the efficiency of PT in wide input range. And, duty cycle control method has a problem of insufficient operating range for the load variation. In other to overcome these problems, this paper introduces a two loop control (PWM and PLL) with PT which provides wide ZVS condition nearly independent of the load variation, and excellent line regulation for the universal input voltage and load range. The performance of the proposed control method is verified by experimental result with 40 [W] DC/DC converter hardware prototypes.Index Terms-piezoelectric transformer, pulse with modulation, phase locked loop, DC/DC converter.

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To perform Earth observations, low-Earth orbit (LEO) satellites require attitude maneuvers, which can be classified into two types: maintenance of a target-pointing attitude and maneuvering between target-pointing attitudes. The former depends on the observation target, while the latter has nonlinear characteristics and must consider various conditions. Therefore, generating an optimal reference attitude profile is difficult. Mission performance and satellite antenna position-to-ground communication are also determined by the maneuver profile between the target-pointing attitudes. Generating a reference maneuver profile with small errors before target pointing can enhance the quality of the observation images and increase the maximum possible number of missions and accuracy of ground contact. Therefore, herein we proposed a technique for optimizing the maneuver profile between target-pointing attitudes based on data-based learning. We used a deep neural network based on bidirectional long short-term memory to model the quaternion profiles of LEO satellites. This model was used to predict the maneuvers between target-pointing attitudes. After predicting the attitude profile, it was differentiated to obtain the time and angular acceleration profiles. The optimal maneuver reference profile was obtained by Bayesian-based optimization. To verify the performance of the proposed technique, the results of maneuvers in the 2–68° range were analyzed.

Owing to the increasing demand for low-power electronic devices, the need for miniaturized, light-weight power supplies with a high power density is growing. A piezoelectric transformer, which is a mechanical resonance-based power transformer, can meet these requirements. However, piezoelectric transformers are based on mechanical resonance, and the resonance characteristics depend on the output current, temperature, and other parameters. Thus, their efficiency may rapidly reduce with changes in the resonance characteristics under specific load and temperature conditions. Therefore, this study proposes a technique that estimating the optimal frequency by using the measurements of the input voltage and current phase difference of the piezoelectric transformer and regulating the output voltage using the duty cycle. Modeling and control system analyses are performed to address the control interference problem caused by the plurality of control variables and control outputs. To demonstrate the proposed technique, a 40 W prototype hardware device is developed. The efficiency improvement is confirmed, and the analysis is validated.