Current-fed Push-pull Parallel-resonant Inverter Research Articles

An Improved Autonomous Current-Fed Push-Pull Parallel-Resonant Inverter for Inductive Power Transfer System

In the inductive power transfer (IPT) system, it is recommended to drive the resonant inverter in zero-voltage switching (ZVS) or zero-current switching (ZCS) operation to reduce switching losses, especially in dynamic applications with variable couplings. This paper proposes an improved autonomous current-fed push-pull parallel-resonant inverter, which not only realizes the ZVS operation by tracking the zero phase angle (ZPA) frequency, but also improves the output power and overall efficiency in a wide range by reducing gate losses and switching losses. The ZPA frequencies characteristic of the parallel-parallel resonant circuit in both bifurcation and bifurcation-free regions is derived and verified by theory and experiments, and the comparative experimental results demonstrate that the improved inverter can significantly increase the output power from 7.68 W to 8.74 W and has an overall efficiency ranging from 63.5% to 72.5% compared with the traditional inverter at a 2 cm coil distance. Furthermore, with a 2-fold input voltage (24 V), the improved inverter can achieve an approximate 4-fold output power of 38.9 W and overall efficiency of 83.6% at a 2 cm coil distance.

Bidirectional Current-Fed Resonant Inverter for Contactless Energy Transfer Systems

This paper presents a bidirectional current-fed parallel resonant push-pull inverter (CFPRPI) for contactless energy conversions. In conventional CFPRPIs, each switch is in series with a blocking diode. Direct zero voltage switching (ZVS) is proposed to remove the series blocking diodes for higher efficiency and boosting ratio. In addition, the modified inverter has bidirectional power flow capability when these blocking diodes are omitted. Resonant tuning of the system is investigated by using a phase-locked loop and a new self-oscillating switching technique (SST). By using the new SST, the inverter has direct ZVS in a wide range of operating frequencies, which is necessary for inductively coupled power transfer systems. Finally, a laboratory prototype with an input voltage of 12 V and a maximum output power of 60 W has been implemented.

A Current-Fed Parallel Resonant Push-Pull Inverter with a New Cascaded Coil Flux Control for Induction Heating Applications

This paper presents a cascaded coil flux control based on a Current Source Parallel Resonant Push-Pull Inverter (CSPRPI) for Induction Heating (IH) applications. The most important problems associated with current source parallel resonant inverters are start-up problems and the variable response of IH systems under load variations. This paper proposes a simple cascaded control method to increase an IH system's robustness to load variations. The proposed IH has been analyzed in both the steady state and the transient state. Based on this method, the resonant frequency is tracked using Phase Locked Loop (PLL) circuits using a Multiplier Phase Detector (MPD) to achieve ZVS under the transient condition. A laboratory prototype was built with an operating frequency of 57-59 kHz and a rated power of 300 W. Simulation and experimental results verify the validity of the proposed power control method and the PLL dynamics.

High-Voltage Closed-Loop Power Supply for Ozone Generators

In this paper the design, implementation and experimental results of a high-voltage power supply for ozone generation are presented. The power stage arrangement is formed by a buck converter plus a current-fed parallel-resonant push-pull inverter. The buck converter is used to both regulate the output power against the line voltage variation, and to control the power delivered to the ozone generator (OG). The push-pull inverter assures safe operation of the OG by working at the parallel resonant frequency given by the high-voltage transformer plus OG characteristic. The closed-loop operation of the proposed converter is analyzed and implemented as a method to compensate variations in the line voltage and in the OG. A low cost commercial UC3872 integrated circuit is used to control both the push-pull inverter and the buck converter, providing OG power control and regulation via buck converter duty cycle. Protections against short circuit and no load operation are also implemented. Experimental results for a 100 W prototype are shown and discussed.

Analysis, Design, and Experimentation of a High-Voltage Power Supply for Ozone Generation Based on Current-Fed Parallel-Resonant Push–Pull Inverter

The use of supply frequencies above 50-60 Hz allows for an increase in the power density applied to the ozonizer electrode surface and an increase in ozone production for a given surface area, while decreasing the necessary peak voltage. Parallel-resonant converters are well suited for supplying the high capacitive load of ozonizers. Therefore, in this paper the current-fed parallel-resonant push-pull inverter is proposed as a good option to implement high-voltage high-frequency power supplies for ozone generators. The proposed converter is analyzed and some important characteristics are obtained. The design and implementation of the complete power supply are also shown. The UC3872 integrated circuit is proposed in order to operate the converter at resonance, allowing us to maintain a good response disregarding the changes in electric parameters of the transformer-ozonizer pair. Experimental results for a 50-W prototype are also provided.