Yuanchao Liu

The dynamic Power Loss analysis in Buck Converter

The dynamic Power Loss in Buck Converter has been investigated in this paper, and the main contributions are as follows: 1) A transient analytic model for BUCK converter has been proposed to calculate the transient loss. This proposed model involves with some significant parasitic parameters which was always ignored in past; 2) Based on the proposed model, the total Dynamic Power Loss in Buck Converter has been developed and some formulas for finding out dynamic loss have been put forward, so designer can calculate the whole loss of a switching circuit by the static characteristics and parameters of semiconductor devices given in datasheet and make devices do their best operation in the circuit; 3) The parasitic parameters in the converter play an important role in transient operation and the dynamic losses make a significant contribution for the total loss. The conclusions can be applied to not only analyzing power loss of converter but selecting power devices.

Small-Signal Modeling of Series Resonant Converter

Based on the basic modeling approach, a new small-signal modeling technique applied to the series resonant converters is presented and the models are in good agreement with the simulation and measurement results.

Low Frequency Model for the Metal Halide Lamp

A new modeling approach for the metal halide (abbrev. MH) lamp has been put forward in this paper. Our works focus on the followings: (1) Based on the low frequency behaviors of MH lamp, a new model for the MH lamp has been proposed. This model is simple but very useful; (2) The voltage waveform of the lamp is not sinusoid but looks like a square waveform, a method for estimating the voltage value has been developed; (3) In order to verity the model for the MH lamp, we calculate the inductors current using the new model. The calculation results are agreed with theoretic results. (4) The five prototypes, which power range is 575 W, 1200 W, 2500 W, 4000 W and 6000 W, have been made. The entire five prototypes work well. (5) Five experiments have been provided in this paper. The experimental results are good agreed with theoretic results, the maximum error is less than 2.5%. So, the new model provides useful tools for analyzing and designing electromagnetic ballasts

A discrete modeling for power factor correction circuit

In this paper, a novel discrete model has been proposed to simulate the controller IC UC3854. The main contributions are as followings: 1) The power stage of the Boost converter has been modeled by using the large signal approach and the loop gain of current program has been put forward; 2) The continues-time voltage control diagram has been investigated by employing equivalent power stage which contains the main circuit and current program; 3) Based on the continues-time model, a new discrete model of PFC has been given out and the operational principle has been introduced; 4) A 4kw prototype has been built up to verify the validity of the new model; Results of the simulation and the experiment show that the power factor is 96.7% and the linear current harmonics components can completely meet the requirements of IEC 61000-3-2.

Design and optimization of mutual inductance for high efficiency ICPT system

An optimization method of mutual inductance for Inductively Couple Power transfer (ICPT) system is proposed in this paper. Then, a method to avoid the multimodal-gain in the effective load range is proposed, which can help to design the ICPT system. All of the study is based on Series-Series (SS) topology. Through the theoretical analysis, the system efficiency can be improved by using the optimization methods. In order to verify the result of theoretical analysis, a 500W wireless power transfer (WPT) prototype with 15cm distance is built. The results show that the efficiency is above 0.88. This result proves that the optimization method is reasonable, reliable and universally applicable. This system can be used as a reference in the field of design and application of wireless power transmission.

Narrow- control-bandwidth Operation of Piezoelectric-transformer Converter

According to the operating and efficiency properties of piezoelectric-transformer, an input matching network (abbrev. IMN) attached to it is proposed in this paper. The main contributions are as follows: (1) The operating principles of piezoelectric-transformer are analyzed and its IMN is put forward. This enable piezoelectric-transformer converter operating area close to the resonant frequency as well as the control bandwidth narrow enough to improve the efficiency. (2)Analyses the electric property of IMN, and draw a conclusion, in agreement with analyze. (3)The simulation is achieved by PSPICE, and the results show that operating bandwidth of the entire resonant network, including IMN and PT, are much narrower than that without IMN but only piezoelectric-transformer.

Small Signal Analysis of a dual-switch forward Converter with non-ideal transformer in Current-Programmed Control

A small signal analysis approach of a dual forward converter with non-ideal transformer in current-programmed control (CPC) has been investigated in this paper. A small-signal model has been derived to determine the small-signal characteristics of the converter. By employing this model, the following significant features have been revealed or explained: (1) if the artificial ramp slop is properly selected, the ideal line-to-output transfer function of the converter becomes zero. That is to say, the output voltage fluctuation of causing from a perturbation of the DC bus voltage can be substantially restrained; (2) the CPC can greatly reduce the Q-factor and make the converter to become a low Q-factor system; (3) the current- programmed control can extend the bandwidth; (4) the magnetizing inductor plays an important role in the converter, so we must consider it when we design the control circuit.

Study of Measurement Approach of Loop Gain of Converter

In this paper, an approach by using the Agilent 4395A to measure the loop gain of the power supply has been deeply developed. The main issues have been investigated as the following: (1). Measurement techniques about the parasitic parameters of the filtering components will be studied. One is how to test of the electrolyte capacitor by Agilent 4395A; another is how to test dynamic inductance of filter inductor by Tektronix TDS5052 with TDSPWR3 software; (2). A measurement approach for loop gain has been put forward; (3). A prototype has been made up and its loop gain has been tested to verify the proposed approaches; (4). The experimental result has first revealed that the biggest analytic error of the loop gain occurs nearby about the resonance frequency of low pass filter. It can be explained that the error results from the equivalent resistor of the power diode and MOSFET; (5). Based on considering the equivalent resistor, a novel accurate small-signal model of buck converter has been proposed to reduce the theoretic error. The proposed approaches, model and other results have provided a powerful tool to analyze and design a power supply

A Novel Soft Switching Technique for Special Buck Converter with High Power and High Efficiency

Based on high power-electronic ballast application, a novel soft switching technique for special buck converter has been investigated in this paper, which has many good performances such as high power, low loss and so on. The main contributions are as follows: 1. a new topology with soft switching has been proposed to match the electronic ballast; 2. the control approach for this new circuit has been put forward and the simulation has done by Pspice, the simulative results show that all power switches in the new circuit are soft switching; 3. The designing procedure has been developed. In order to verify the new circuit, a prototype of output power 6 kW has been made up. The experimental results display that the new proposed circuit has higher efficiency (about 96%) and the overall efficiency of this ballast, which is about 85% in hard switching case, has been increased to 93%

Variable parameter model for low-power PT

To reduce the analytic error, a new variable parameter model for low power PT has been explored in this paper. A multi-frequency test approach is proposed to obtain more exact internal parameters of PTs model. Based on its conventional model, a set of multi-frequency equations is built up. Through solving these equations by employing the measured data, the internal parameters of PTs model is determined. Some experimental results are provided in this paper to verify the variable parameter model. The experimental results show that the maximum analytic error of the new model is less than 5%. The variable parameter model is an important tool for analyzing and designing PT converter.