Two-Phase Hybrid Forward Convertor with Series-Parallel Auto-Regulated Transformer Windings and a Common Output Inductor

Wu, Xinke,Chen, Hui The Korean Institute of Power Electronics 2013 JOURNAL OF POWER ELECTRONICS Vol.13 No.5

For conventional interleaved two-phase forward converters with a common output inductor, the maximum duty cycle is 0.5, which limits the voltage range and increases the difficulty of the transformer's optimization. A new two-phase hybrid forward converter with series-parallel auto-regulated transformer windings is presented in this paper. With interleaved control signals for the two phases, the secondary windings of the transformers can work in series when the duty cycle is larger than 0.5, and they can work in parallel when duty cycle is lower than 0.5. Therefore, the maximum duty cycle is extended and the turns ratio of the transformer can be optimized. Duty cycle dependent auto-regulated windings result in the steady states of the converter being different in different duty cycle ranges (D>0.5 and D<0.5). Fortunately, the steady state gains of the proposed hybrid converter are identical at different duty cycle ranges, which means a stepless shift between two states. A prototype is built to verify the theoretical analysis. A conventional control loop is compatible for the whole input voltage range and load range thanks to the stepless shifting between the different duty cycle ranges.

Two-Phase Hybrid Forward Convertor with Series-Parallel Auto-Regulated Transformer Windings and a Common Output Inductor

Xinke Wu,Hui Chen 전력전자학회 2013 JOURNAL OF POWER ELECTRONICS Vol.13 No.5

For conventional interleaved two-phase forward converters with a common output inductor, the maximum duty cycle is 0.5, which limits the voltage range and increases the difficulty of the transformer’s optimization. A new two-phase hybrid forward converter with series-parallel auto-regulated transformer windings is presented in this paper. With interleaved control signals for the two phases, the secondary windings of the transformers can work in series when the duty cycle is larger than 0.5, and they can work in parallel when duty cycle is lower than 0.5. Therefore, the maximum duty cycle is extended and the turns ratio of the transformer can be optimized. Duty cycle dependent auto-regulated windings result in the steady states of the converter being different in different duty cycle ranges (D>0.5 and D<0.5). Fortunately, the steady state gains of the proposed hybrid converter are identical at different duty cycle ranges, which means a stepless shift between two states. A prototype is built to verify the theoretical analysis. A conventional control loop is compatible for the whole input voltage range and load range thanks to the stepless shifting between the different duty cycle ranges.

Case study on stability performance of asymmetric steel arch bridge with inclined arch ribs

Xinke Hu,Xu Xie,Zhanzhan Tang,Yonggang Shen,Pu Wu,Lianfeng Song 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.18 No.1

As one of the most common failure types of arch bridges, stability is one of the critical aspects for the design of arch bridges. Using 3D finite element model in ABAQUS, this paper has studied the stability performance of an arch bridge with inclined arch ribs and hangers, and the analysis also took the effects of geometrical and material nonlinearity into account. The impact of local buckling and residual stress of steel plates on global stability and the applicability of fiber model in stability analysis for steel arch bridges were also investigated. The results demonstrate an excellent stability of the arch bridge because of the transverse constraint provided by transversely-inclined hangers. The distortion of cross section, local buckling and residual stress of ribs has an insignificant effect on the stability of the structure, and the accurate ultimate strength may be obtained from a fiber model analysis. This study also shows that the yielding of the arch ribs has a significant impact on the ultimate capacity of the structure, and the bearing capacity may also be approximately estimated by the initial yield strength of the arch rib.

Design and optimization of a wide output voltage range LED driver based on LLC resonant topology

Yue Chen,Xinke Wu,Zhaoming Qian,Wenping Zhang 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

LLC resonant converter is an excellent candidate for medium power DC/DC converter. However, it is usually used in constant voltage output application. As for the DC/DC stage in high efficiency LED driver, the output voltage may vary widely while output current remains constant. This paper proposes a new design method which is suitable for wide output range application. Design process, analysis and optimization of design parameters are also discussed in detail. A 140W experimental prototype is built to verify the design and proved a high efficiency after optimization. Experimental result shows LLC is a good topology choice for LED driver for it is highly efficient throughout wide output voltage range.

Analysis and Design Considerations for a High Power Buck Derived LED Driver with Extended Output Voltage and Low Total Harmonic Distortion

Haijun Lv,Xinke Wu,Junming Zhang 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.5

In order to reduce the cost, improve the efficiency and simplify the complicated control of existing isolated LED drivers, an improved boundary conduction mode (BCM) Buck ac-dc light emitting diode (LED) driver with extended output voltage and low total harmonic distortion is proposed. With a coupled inductor winding and a stacked output, its output voltage can be elevated to a much higher value when compared to that of the conventional Buck ac-dc converter, without sacrificing the input harmonics and power factor. Therefore, the proposed Buck LED driver can meet the IEC61000-3-2 (Class C) limitation and has a low THD. The operating principle of the topology and the design methodology of the ac-dc LED driver are presented. A 150 W ac-dc prototype was built in the laboratory and it shows that the input current harmonics meet the lighting standard. In addition, the THD is less than 16% at a typical ac input. The peak efficiency is higher than 96.5% at a full load and a normal input.

Analysis and Design Considerations for a High Power Buck Derived LED Driver with Extended Output Voltage and Low Total Harmonic Distortion

Lv, Haijun,Wu, Xinke,Zhang, Junming The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.5

In order to reduce the cost, improve the efficiency and simplify the complicated control of existing isolated LED drivers, an improved boundary conduction mode (BCM) Buck ac-dc light emitting diode (LED) driver with extended output voltage and low total harmonic distortion is proposed. With a coupled inductor winding and a stacked output, its output voltage can be elevated to a much higher value when compared to that of the conventional Buck ac-dc converter, without sacrificing the input harmonics and power factor. Therefore, the proposed Buck LED driver can meet the IEC61000-3-2 (Class C) limitation and has a low THD. The operating principle of the topology and the design methodology of the ac-dc LED driver are presented. A 150 W ac-dc prototype was built in the laboratory and it shows that the input current harmonics meet the lighting standard. In addition, the THD is less than 16% at a typical ac input. The peak efficiency is higher than 96.5% at a full load and a normal input.

Analysis of MHz 380V-12V DCX with low FoM device

Hongbo Shi,Xinke Wu,Mingchao Xia 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

1MHz isolated high efficiency high power density DC/DC converter is critical for future industrial applications. The GaN devices have a better performance for such high frequency than silicon device of high breakdown voltage due to their much lower parasitic capacitance. The modeling of the primary switches conduction losses is built in this paper. Based on the model the relation between the NFoM (Rdson⋅Cotr) of primary devices and conduction loss is revealed, thus the lower voltage devices with lower FoM is adopted to implemented the experimental verification. Since the equivalent NFoM is independent of the device count of series connection and is decided by single device, an inputseries output-parallel structure prototype with multiple SRC DCX cells is implemented with low voltage MOSFETs. The 380V-12Vprototype achieves a peak efficiency of 98.3% and a power density of 810W/inch3 with multiple 60V MOSFETs.

Primary Side Constant Power Control Scheme for LED Drivers Compatible with TRIAC Dimmers

Junming Zhang,Ting Jiang,Lianghui Xu,Xinke Wu 전력전자학회 2013 JOURNAL OF POWER ELECTRONICS Vol.13 No.4

This paper proposes a primary side constant power control scheme for TRIAC dimmer compatible LED drivers. The LED driver is a Flyback converter operated in boundary conduction mode (BCM) to minimize the switching loss. With the proposed control scheme, the input power of the Flyback converter can be controlled by the TRIAC dimming angle, which is not affected by AC input voltage variations. Since the output voltage is almost constant for LED loads, the output current can be changed by controlling the input power with a given conversion efficiency. The isolated feedback circuit is eliminated with the proposed primary side control scheme, which dramatically simplifies the whole circuit. In addition, the input current automatically follows the input voltage due to the BCM operation, and the resistive input characteristic can be achieved which is attractive for TRIAC dimming applications. Experimental results from a 15W prototype verify the theoretical analysis.

Primary Side Constant Power Control Scheme for LED Drivers Compatible with TRIAC Dimmers

Zhang, Junming,Jiang, Ting,Xu, Lianghui,Wu, Xinke The Korean Institute of Power Electronics 2013 JOURNAL OF POWER ELECTRONICS Vol.13 No.4

This paper proposes a primary side constant power control scheme for TRIAC dimmer compatible LED drivers. The LED driver is a Flyback converter operated in boundary conduction mode (BCM) to minimize the switching loss. With the proposed control scheme, the input power of the Flyback converter can be controlled by the TRIAC dimming angle, which is not affected by AC input voltage variations. Since the output voltage is almost constant for LED loads, the output current can be changed by controlling the input power with a given conversion efficiency. The isolated feedback circuit is eliminated with the proposed primary side control scheme, which dramatically simplifies the whole circuit. In addition, the input current automatically follows the input voltage due to the BCM operation, and the resistive input characteristic can be achieved which is attractive for TRIAC dimming applications. Experimental results from a 15W prototype verify the theoretical analysis.