Xiaogao Xie

A Novel Output Current Estimation and Regulation Circuit for Primary Side Controlled High Power Factor Single-Stage Flyback LED Driver

A novel output current estimation and regulation circuit for the primary side controlled high power factor (PF) single-stage flyback LED is proposed in this paper. The proposed output current estimation and regulation circuit is composed of a novel output current estimation circuit and a negative feedback networks. The output current estimation circuit can estimate the output current in the primary side and then achieve output current regulation through negative feedback. The proposed output current estimation and regulation circuit is suitable for discontinuous conduction mode (DCM) and boundary conduction mode (BCM). The output of the proposed output current estimation and regulation circuit is a half-sine waveform and followed by the primary current, hence high PF can be achieved. Detailed theoretical analysis and design considerations were presented. Two 340 mA/25 V laboratory LED driver prototypes operating in DCM and BCM were built up. The experimental results verified theoretical analyses.

An Improved Buck PFC Converter With High Power Factor

An improved buck power factor correction (PFC) converter topology is proposed in this paper. By adding an auxiliary switch and two diodes, the dead zones in ac input current of traditional buck PFC converter can be eliminated. An improved constant ON-time control is proposed and utilized in this improved buck PFC converter to force it that operates in critical conduction mode (CRM). With optimal control parameters, nearly unit power factor can be achieved and the input current harmonics can meet the IEC61000-3-2 class C standard within the universal input voltage range. Moreover, the efficiency of the proposed converter is not deteriorated compared to the conventional buck converter. Detailed theoretical analysis and optimal design considerations for the proposed converter are presented and verified by a 100-W lab-made prototype.

Multioutput LED Drivers With Precise Passive Current Balancing

According to the detailed essential concept of current balancing presented in this paper, an improved passive current balancing method based on capacitive scheme is proposed consequently. This method can also be extended to the application of isolated multioutput LED drivers. Compared with active method to achieve current balancing among the multioutput LED strings, the passive method exhibits its attractive advantages in cost efficiency and balancing accuracy. Both the macromodel simulation and the prototype experiment results demonstrate the feasibility of the proposed method. The proposed method can achieve precise balancing in steady state and dynamic state even with considerably different peripheral parameters.

A Novel Integrated Buck–Flyback Nonisolated PFC Converter With High Power Factor

A novel integrated buck-flyback nonisolated power factor (PF) correction (PFC) converter is proposed in this paper. This new converter is an inherent integration of a buck converter and a flyback converter, which operates in either flyback mode or buck mode according to whether the input voltage is lower or higher than the output voltage. In this way, the dead zones of ac input current in traditional buck PFC converter are eliminated. Therefore, the proposed integrated buck-flyback nonisolated PFC converter can achieve high PF under universal ac input range, and its input current harmonics can easily meet the IEC61000-3-2 Class C limits. The efficiency of the proposed converter is not deteriorated obviously compared to the conventional buck converter. Detailed theoretical analysis and optimal design considerations are presented. A 100-W prototype was built up to verify the theoretical analysis of the proposed integrated buck-flyback nonisolated PFC converter.

A Finite-Time Motion Control Strategy for Odor Source Localization

This paper deals with the problem of odor source localization by designing and analyzing a finite-time motion control strategy (FTMCS), which consists of a finite-time parallel motion control algorithm and a finite-time circular motion control algorithm. Specifically, a motion control architecture is first given and includes two important modules: 1) a coordinating control module; and 2) a tracking control module. In the coordinating control module, robots communicate with each other to coordinate their virtual position and virtual velocity such that the virtual velocity consensus and the accurate virtual shape decided by the potential function can be reached within a finite-time interval. In the tracking control module, a finite-time tracking control algorithm is implemented such that the real velocity and the real position of the robot can track the virtual velocity and the virtual position within a finite-time interval. Based on the proposed motion control architecture, a finite-time parallel motion control algorithm that can control a group of robots to trace a plume, is derived. Moreover, a finite-time circular motion control algorithm that can enable the robot group to search for odor clues is also designed. Finally, simulations are worked out to illustrate the effectiveness of the FTMCS for odor source localization.

A Novel Control Strategy Based on Natural Frame for Vienna-Type Rectifier Under Light Unbalanced-Grid Conditions

In order to reduce the dc-link voltage ripple and the dc component of the reactive power under unbalanced input conditions, a novel natural-frame-based control scheme for a Vienna rectifier is proposed in this paper. First, by applying an early-developed direct decoupled synchronization method, the fundamental positive/negative-sequence voltage components are derived. Then, a natural-frame-based current control loop is designed based on the mathematical modeling of the Vienna rectifier under unbalanced input conditions. Based on the natural abc frame, the proposed control scheme considerably reduces total algorithm complexity and helps reduce the dc reactive components and total loss in comparison to the traditional dual-hybrid current control schemes. In addition, the stationary operation region of the Vienna-type rectifiers is analyzed, and the scheme is claimed to work out of the stationary operation region with severe voltage unbalance. The dynamic response of unbalanced input is presented. The experimental results are given to demonstrate the effectiveness of the proposed control scheme. In addition, the performance comparison between the traditional controller and the proposed controller is given by experimental results.

Study on the Single-Stage Forward-Flyback PFC Converter With QR Control

The single-stage forward-flyback power factor correction converter with quasi-resonant (QR) control is studied in this paper. This converter merges flyback converter and forward converter through a common transformer. Only the flyback subconverter works when the input voltage is lower than the reflected output voltage while both the flyback subconverter and the forward subconverter operate to share the output power in the rest region. The dead zones which exist in the ac input current of traditional forward converter are eliminated and high power factor can be achieved. Two different QR control schemes have been studied. Detailed analysis, optimal design considerations, and comparison for these two QR control modes are provided. Finally, two 120 W experimental prototypes for LED driver were built up to verify the theoretical analysis.

Improved Synchronous Rectifier Driving Strategy for Primary-Side Regulated (PSR) Flyback Converter in Light-Load Mode

Based on the concept derivation, this paper proposes an improved synchronous rectifier (SR) driving strategy focusing on the quasi-resonant primary-side regulation (QR-PSR) Flyback converter, for the applications of dc-dc front-end converter and ac-dc PFC converter both, to prevent reverse energy flowing in light-load/standby mode. Three different implementation candidates are exhibited and analyzed. This proposed driving strategy is programmable for the practical design with input voltage feedforward effect and helpful for achieving the rigorous target of low power loss under light output load condition presented by the U.S. Department of Energy (DoE). Two 60 W (12 V/5 A) lab-made prototypes of synchronous rectified QR-PSR Flyback ac-dc PFC converter and dc-dc front-end converter are built up, respectively, to verify the feasibility of this proposed driving strategy. In the lab-made prototype of ac-dc PFC converter, it improves the overall conversion efficiency more than 3% in light-load mode; in the lab-made prototype of dc-dc front-end converter, it saves the light load power loss up to 0.5 W, especially with 110 Vac input. Reliable operation is achieved when the proposed SR driving strategy is practically designed with enough margin; however, too large design margin could decrease the average conversion efficiency.

A variable-frequency one-cycle control for BCM flyback converter to achieve unit power factor

The single-stage flyback power factor correction (PFC) converter is well applied in medium and low power occasion such as adapters or LED drivers. Usually, the flyback PFC converter is preferred to operating in boundary conduction mode (BCM) for achieving high power factor (PF) and high efficiency at the same time. However, the conventional BCM control scheme such as input voltage tracking control or constant on-time control (COT) could not achieve unit PF for the flyback PFC converter. As input voltage increases, the PF and the total harmonic distortion (THD) of flyback converter deteriorate seriously. In this paper, a variable-frequency one-cycle control (VF-OCC) for BCM flyback single-stage PFC converter is presented to achieve unit power factor. Detailed theoretical analysis and design consideration for the VF-OCC are described. At last, two 54W/1.5A laboratory prototypes with two operation strategies have been built up. Experiment results show that the BCM flyback converter with VF-OCC can achieve high PF and low THD over universal input voltage range.

A single-stage high power factor bridgeless forward converter with an improved constant on-time control

A new isolated single-stage power factor correction (PFC) bridgeless forward converter is proposed in this paper. The proposed converter consists of two forward loops with a four-winding transformer. By eliminating the input bridge diodes, conduction losses can be decreased. An improved constant on-time control (COT) is applied to the proposed converter to achieve high power factor and then the input current harmonics can meet the IEC61000-3-2 Class C standard. The proposed converter operates in either discontinuous current mode (DCM) or boundary continuous current mode (BCM) according to the input voltage value. Detailed analysis and circuit operation stages are provided. An 80-W prototype is built up to verify the theoretical analysis of the proposed converter.