Jianping Ying

Common mode noise modeling and analysis of dual boost PFC circuit

To achieve high efficiency PFC front stage in switching mode power supply (SMPS), dual boost PFC (DBPFC) topology shows superior characteristics compared with traditional boost PFC, but it by nature brings higher EMI noise, especially common mode (CM) noise. This paper deals with the modeling and analysis of DBPFC CM noise based on and compared with boost PFC, noise propagation equivalent circuits of both topologies are deduced, and theoretical analysis illustrates the difference. Experiments are performed to validate the EMI model and analysis.

A Novel Precise Design Method for LLC Series Resonant Converter

In this paper, a novel precise analysis method based on time domain analysis for LLC series resonant converter is proposed and a clear design guide line is given. Because LLC resonant converter has simple structure, high efficiency and high switching frequency capability, it is widely used nowadays. To achieve an optimized design and propose a clear design guide line, understanding its DC gain characteristic and parameters effect on efficiency is very important. Traditional analysis method based on fundamental-harmonic approximation can not give accurate results. Finally, following proposed design guide line, a prototype of MHz LLC series resonant converter with 96% efficiency has been built and tested. Experimental results testified the analysis method and proposed design guide line

Analysis and Implementation of LLC Burst Mode for Light Load Efficiency Improvement

Burst mode control is applied to improve light load efficiency of LLC converter in this paper. Detailed analysis on characteristic and operation processes of LLC burst mode control with SR is presented. Based on the analysis, some important rules of LLC burst mode control are proposed, which is the key to achieve high light load efficiency. The rules include: the suitable primary and secondary driving timing, design guild line of output filter, reasonable control strategy etc. To verify the analysis, a prototype with 12V/100A output has been built. Thanks to the proposed control strategy and optimum design, light load efficiency of LLC converter can be improved significantly, such as efficiency at 10% load can be improved from 92.5% to 94.8%.

A Novel Transformer Structure for High power, High Frequency converter

Power transformer structure is a key factor for the high power, high frequency converter performance which includes efficiency, thermal performance and power density. This paper proposes a novel transformer structure for the kilo-watt level, high frequency converter which is reinforce insulation needed for the secondary side to primary side. The transformer has spiral-wound primary layers using TIW (triple insulation wire) and PCB-winding secondary layers. All the windings are arranged by full interleaving structure to minimize the leakage inductance and eddy current loss. Further more, the secondary rectifiers and filter capacitors are mounted in PCB-winding secondary layers to further minimize the termination effect. A 1.2 KW (O/P: 12 V/100 A, I/P: 400 V) Mega Hz LLC converter prototype employed the proposed transformer structure is constructed, and over 96% efficiency achieved.

Prediction of PIN diode reverse recovery

Generally, the reverse recovery issue of diode is difficult to deal with, which causes large added loss and EMI. Different down slopes for diode reverse voltage mean different working conditions, and this paper shows you the general concept with different down slopes and how to predict the reverse recovery current to calculate the relative switching loss. The empirical equations are deduced based on physical concepts and verified by lab measurements.

A novel light load solution for LLC series resonant converter

LLC series resonant topologies has many unique characteristics and improvements over PWM topologies. However, at light load or open load, the unstable output voltage is one of critical issues of LLC-SRC which uses diodes as rectifiers. The traditional solution employs dummy load, nevertheless it results in high dummy load loss and low system efficiency. This paper analyzed the root cause that result in the open load issue and proposed a simple and practical solution, which can stabilize the output voltage at no dummy load and make LLC series resonant converter work in a narrow frequency range. At last, the solution is employed in a 580 kHz, 54 V/50 A telecom power supply and the LLC circuit operating frequency is 748 kHz with 15 W total losses, rather than 1 MHz with 200 W total losses in an unstable case.

Asymmetrical H-PFC for Low Line Applications

In this paper, a novel bridgeless power factor correction (PFC) circuit has been proposed. High efficiency can be obtained especially at low line condition because no input bridge rectifier is used in the proposed topology. A concept of unique configuration of diodes has been proposed to reduce the common-mode (CM) conducted noise. Eventually, an 800 W prototype has been built. And experimental results show high efficiency and acceptable original CM noise.

Sensorless brushless DC motor drive for air-conditioner compressor

Brushless DC motors (BLDCM) conventionally require position sensors to generate proper commutation instructions. Due to the high temperature environment, BLDCM in air-conditioner compressor requires a robust speed control without rotor position sensors. In this paper, a novel hybrid solution was presented to achieve reliable sensorless rotor position detection with relative concise and low cost circuit as well as little software expense. Experimental results shows that the schemes implemented are workable and the performance achieved are satisfactory.

A Novel Three-Phase Three-Level Power Factor Correction (PFC) Converter Using Two Single-Phase PFC Modules

In recent years, the research on power factor correction (PFC) circuits for high-power applications has increased for the rigorous harmonic limits. Three-level boost type PFC is a very attractive solution for high power density and high efficiency three-phase preregulator. The major advantage of the three level structures is the reduction of the voltage stress on the power switches, which allows the use of low losses and low cost power semiconductors. A common practice for three-phase high-power PFC is the connection of three single-phase modules to the three-phase AC system to achieve the required output power level. Unity power factor is obtained with single-phase modules, but the cost is high because of the large number of components used in the system. In this paper, based on the above considerations, a novel three-phase power-factor correction scheme using only two single-phase PFC modules is proposed and compared with the conventional one in section II. The control strategy is analyzed in section III in detail. The proposed converter has advantages such as fewer components, lower cost, higher component utilization and so on. At last, experimental results are presented to prove the high reliability and efficiency of the converter.

A high efficiency 3 KW DC-DC converter with novel external driven synchronous rectifier

A high efficiency phase shifted ZVS full bridge converter with novel external driven synchronous rectifier is presented. The proposed external driver scheme is mainly discussed in the paper. The two synchronous rectifiers driver signals are generated by logic combination of four control signals from phase shift controller. An 80 KHz, 24 V/125 A DC-DC converter prototype is constructed, nearly 1.5% efficiency improvement has been achieved compared with the conventional Schottky rectifier.