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Traditional load regulation methods for a resonant converter mainly rely on frequency modulation. It is always a tradeoff between the design of the resonant network and the range of load. Especially for wireless power transfer (WPT) systems, the resonant network usually has a high quality factor. Small variation on frequency leads to huge drop in gain and efficiency. Due to this problem, many WPT systems are unregulated and they need one or two more front-end stages to regulate the dc bus voltage and perform power factor correction (PFC). In order to lower the cost and complexity of two- or three-stages structure, a single-stage solution with a silicon carbide (SiC) based Z-source resonant converter (ZSRC) was recently proposed. The Z-source network provides high reliability as being immune to shoot-through problems. Additionally, a ZSRC can boost the dc bus voltage while the traditional voltage-source inverter can only produce a lower voltage. However, the load regulation of this new topology has not been addressed. Two effective load regulation methods with constant frequency are presented for this SiC-based ZSRC specifically. Operation principle of the two load regulation methods are described in this paper. Experimental results based on a 200-W scale-down prototype with a full-bridge series resonant dc–dc converter are presented to illustrate the mechanism of these two methods. [ABSTRACT FROM AUTHOR]

In this paper, the Z-source converter is introduced to power factor correction (PFC) applications. The concept is demonstrated through a wireless power transfer (WPT) system for electric vehicle battery charging, namely Z-source resonant converter (ZSRC). Due to the Z-source network (ZSN), the ZSRC inherently performs PFC and regulate the system output voltage simultaneously, without adding extra semiconductor devices and control circuitry to the conventional WPT system such as conventional PFC converters do. In other words, the ZSN can be categorized as a family of the single-stage PFC converters. In addition, the ZSN is suitable for high-power applications since it is immune to shoot-through states, which increases reliability and adds a boost feature to the system. The ZSRC-based WPT system operating principle is described and analyzed in this paper. Simulations and experimental results based on a 1-kW prototype with 20-cm air gap between the system primary and secondary sides are presented to validate the analysis and demonstrate the effectiveness of the ZSN in the PFC of the WPT system. [ABSTRACT FROM PUBLISHER]

The quasi-resonant (QR) control scheme is widely adopted in a Flyback converter to maximize its efficiency by reducing the switching loss. The switching frequency increases with decreasing load or increasing input voltage. In order to limit electromagnetic interference noise and improve light load efficiency, the maximum switching frequency should be limited. However, the maximum switching frequency limitation adopted in QR control will cause audible noise due to the frequency hopping phenomena at certain load and input condition, which is related to the intrinsic output characteristic of the control scheme. This paper presents a simple solution to eliminate the frequency hopping in the QR Flyback using an adaptive blanking time circuit. The proposed method changes the blanking time automatically to keep the output characteristic smooth that eliminates the audible noise in the transformer. The detailed operation principle and design considerations are presented. The experimental results from a 16 V/4 A prototype are provided to validate the effectiveness of the proposed solution. [ABSTRACT FROM AUTHOR]