An RCD clamp circuit is usually used in flyback converters, in order to limit the voltage spikes caused by leakage transformer inductance. Oscillation ringing appears due to the clamp diode, which deteriorates the converter's power rate. This brief describes this ringing phenomenon and the use of an RC-RCD clamp circuit for damping the clamp diode's oscillation. This clamp circuit is capable for improving a flyback converter's power ratio.

This paper investigates a control approach for achieving reliable zero-voltage switching transitions within the entire operating range of a conventional nonisolated bidirectional dc-dc converter that utilizes synchronous rectification. The approach is based on operation in the discontinuous conduction mode with a constant reversed current of sufficient amplitude, which is achieved by load-dependent variation of the switching frequency. This paper focuses on the obtained resonant voltage transitions and provides analytical models for determining the reversed current and timing parameters that would ensure safe, reliable, and highly efficient operation of the converter. In addition, the proposed approach solves the synchronous transistor's spurious turn-on and body diode reverse recovery induced issues, does not require any additional components or circuitry for its realization, and can be entirely implemented within a digital signal controller. The effectiveness and performance of the presented control approach was confirmed in a 1-kW experimental bidirectional dc-dc converter that achieved 97% efficiency over a wide range of output powers at switching frequencies above 100 kHz.

This article introduces a new method for temperature-compensated capacitance–frequency converter with a single quartz crystal oscillating in the switching oscillating circuit. The novelty of this method lies in the use of additionally connected capacitances in series with JFET switching transistors to the shunt capacitance of the quartz crystal bringing a considerable reduction of the temperature influence of AT-cut crystal frequency change in the temperature range between 0 and 50°C. The oscillator switching method and parallel switching stray capacitances connected to the quartz crystal do not only compensate crystal's natural temperature characteristics but also any other influences on the crystal such as aging of both the crystal and other oscillating circuit elements. In addition, they also reduce the output frequency measurement error. The experimental results show that through high temperature compensation improvement of the quartz crystal characteristics, this switching method enables 20zF resolution capacitance to frequency transduction in the range 0–4pF to 2–45kHz

An already published current control strategy for the coupled-inductor buck-boost converter is able to change its aim from controlling the input current to controlling the output current, and vice versa, depending on the instantaneous operation point and the applied current references. The main drawback of the two PI-based control implementation is its slow response when the control aim is changed from one current to the other. Due to the magnetic coupling, the converter's control-to-input and control-to-output current small signal transfer functions exhibit similar first-order characteristics. Therefore, it is possible to transform the previous control scheme to a PI-based one that exhibits faster and, in certain cases, much faster transitions between input and output current control operation. The presented experiments also show that the steady-state behavior of the converter is unaffected by the new control implementation.

This review presents various ways of detection of different physical quantities based on the frequency change of oscillators using piezoelectric crystals. These are influenced by the reactance changes modifying their electrical characteristics. Reactance in series, in parallel, or a combination of reactances can impact the electrical crystal substitute model by influencing its resonant oscillation frequency. In this way, various physical quantities near resonance can be detected with great sensitivity through a small change of capacitance or inductance. A piezoelectric crystal impedance circle and the mode of frequency changing around the resonant frequency change are shown. This review also presents the influence of reactance on the piezoelectric crystal, the way in which the capacitance lost among the crystal’s electrodes is compensated, and how the mode of oscillators’ output frequency is converted to lower frequency range (1–100 kHz). Finally, the review also explains the temperature–frequency compensation of the crystals’ characteristics in oscillators that use temperature–frequency pair of crystals and the procedure of the compensation of crystals own temperature characteristics based on the method switching between the active and reference reactance. For the latter, the experimental results of the oscillator’s output frequency stability (f_out = ±0.002 ppm) at dynamical change of environment temperature (0–50 °C) are shown.

This paper deals with a wireless power transfer system where a novel structure of transmitting/receiving double DD coils is applied. This system uses two identical double D (DD) transmitter coils stacked on each other to transfer power to two stacked receiver coils. The power is transmitted simultaneously and independently through both transmitter coils to the receiving coils. The magnetic field of the first coil does not interfere with the second coil. Both transmitter and receiver coils are placed on each other and occupy the same footprint, so there is no need for increased space. This can lead to an interesting wireless power transfer system—from single load to double the load and higher power transfer density.