Dongyuan Qiu

Study on frequency-tracking wireless power transfer system by resonant coupling

Detuning is the application barrier of resonant coupling wireless power transfer. This paper analyzes the effects about inductance variations of launch coil and receiving coil to wireless transmission efficiency from its transmission mechanism and model, and also analyzes detuning mechanism. And thus, it reveals that transmission efficiency has a great affection with inductance of launch coil changing. In order to make sure that wireless power transfer by resonant coupling operates without detuning, a new method of frequency tracking control is came up with, which is, making frequency of transmitting power source tracking with the nature frequency of launch resonant circuit automaticllly. Hence, it avoids detuning and improves transmission efficiency greatly. Finally, a prototype of 1 MHz wireless power transfer system by resonant coupling was made. Experimental results prove this method very well.

Single current sensor control for single-phase active power factor correction

This paper presents the realization of a boost-type active power factor corrector (APFC) using a single current sensor to sense the inductor current for input current shaping and output voltage regulation. Neither input voltage nor output voltage sensing is needed. The sensed inductor current is used for two main functions. The first one is for comparing with a sawtooth signal in order to shape the input current waveform. The second one is for determining the input and output voltages by processing the rate of change of the inductor current when the main switch is in on and off states, respectively. Compared with conventional APFCs, the proposed technique has several advantages. First, no dissipative voltage divider is required. Second, electrical isolation between the power conversion stage and the control stage can be achieved inherently. Finally, no complicated or sophisticated digital sampling and numerical computations are needed. The applicability and accuracy of the proposed technique have been studied experimentally. Steady-state behavior and large-signal response under output load disturbance are also investigated.

Duty ratio control of resonant switched capacitor DC-DC converter

Resonant switched capacitor (RSC) converter has the advantage of zero-current switching, however, its output power range is narrow and its voltage conversion ration is predetermined by its topology. In this paper, a new duty ratio control method for RSC converter was presented. In the proposed method, the discharging time was fixed and the charging time was variable. By adjusting the ratio of charging time, good output voltage regulation for large changes in input voltage and/or load values could be obtained. Most of the switching devices were still zero-current switching. The advantage of low switching current and low EMI in RSC converter was still kept in the proposed duty ratio control scheme. A step-down RSC converter was used as an example in this paper. The circuit operation principle and steady-state characteristics were described in detail. A step-down RSC prototype with the proposed method has been implemented and tested; theoretical prediction of its regulation is verified experimentally

The Quantitative Characterization of Symbolic Series of a Boost Converter

In this letter, the authors put forward a symbolic approach to analyze the nonlinearities of switching power converters. This proposed method can be used to describe bifurcation and chaos behavior by means of coarse-grained symbols. First, the period-doubling structure of a symbolic series is studied in symbolic dynamics. Second, the block entropy, which is the related statistics of subsequences of a symbolic series, is introduced. Finally, two Boost converters are studied as examples to illustrate the applications of the proposed symbolic dynamics method. Via block entropy, both period-doubling and border collision bifurcations are identified and quantified, and initial value sensitivity is successfully used to distinguish chaos from periodic motions.

A modified Z-source DC-DC converter

A modified Z-source dc-dc converter is proposed in this paper. Compared with the conventional Z-source dc-dc converter, the proposed converter can obtain higher voltage gain with lower voltage stresses of switch and the impedance network capacitor and operate with wide-range load. Therefore, the proposed Z-source dc-dc converter not only has lower cost but also has smaller weight and size. The operating principle is analyzed in detail and parameter design of the impedance network is introduced. An experimental prototype was built to verify the validity of the proposed Z-source dc-dc converter.

A single-switch high step-up DC-DC converter with coupled inductor

With the development of photovoltaic (PV), fuel cells and uninterruptible power supply (UPS), high step-up converter plays an important role in them. In this paper, a single switch high step-up DC-DC converter is proposed, which can achieve high voltage gain without extreme duty cycle and huge turn ratios of coupled inductor. The leakage energy of coupled inductor can be recycled and the voltage across the switch can be clamped. Moreover, the reverse recovery of some diodes can be reduced. All these characteristics make it possible to design appropriate parameters to realize high step-up gain and high efficiency. The operating mode, static analysis and simulation results have been presented, and a prototype circuit has been realized to verify the effectiveness of the proposed converter.

Parameter monitoring of high-frequency electronically operated discharge lamp systems

Discharge lamps require high ignition voltage from typically one to several kilovolts for cold-start, but have low on-state voltage of typically 100 V. For discharge arc monitoring purposes, it is difficult or uneconomical to implement voltage sensor to cover such a wide range of voltage. In this paper, a nonintrusive and electrically isolated method, based on the single-sensor principle, is used to derive the system parameters and variables for system monitoring and control purposes. Unlike the traditional resistive potential divider for voltage feedback, the proposed method is nondissipative. Only one coupled winding is used to derive the converter inductor voltage, from which the lamp power, lamp arc resistance and inverter dc link voltage can be accurately derived. The proposal is verified with good agreement between derived values and measurements in an electronic ballast-fluorescent lamp system. The proposal can be useful in applications in which sensing the voltage across the load is either difficult or costly.

A novel single-switch cascaded DC-DC converter of Boost and Buck-boost converters

This paper proposes a novel single-switch dc-dc converter with voltage gain D/(1-D)2 by cascading a Boost converter and a Buck-boost converter. The proposed converter has the advantages of simple circuit structure and extended voltage conversion ratio. The operating principle and steady-state analysis of the proposed converter are discussed in detail. Finally, a prototype is implemented to verify theoretical analysis.

A quasi-Z-source DC-DC converter

A novel quasi-Z-source dc-dc converter is proposed in this paper. Compared with the conventional Z-source dc-dc converter, the proposed converter features high voltage gain with lower voltage stress of the impedance network capacitors and has common ground for input and output. Moreover, both the input source current and output load current of the proposed converter are continuous, which provides advantage for input and output filtering. Therefore, the proposed converter has lower cost and better performance. The circuit analysis of the proposed converter is illustrated in detail and the parameter design is introduced. Finally, simulation and experimental results are presented to verify the validity of proposed converter.

A high-performance Z-source inverter with low capacitor voltage stress and small inductance

A novel high-performance Z-source inverter is proposed in this paper. It can obtain the same voltage gain with low Z-source network capacitor voltage stress than conventional one and has inherent limitation to inrush-current at startup. Moreover, it can work in a very wide range load even with small inductance of the Z-source network inductor. Therefore, compared with the conventional Z-source inverters, the proposed converter not only has lower cost but also has smaller weight and size. The operating principle and parameters design of the proposed converter are analyzed. Simulation and experimental results are presented to verify the validity of the proposed high-performance Z-source inverter.