Low Line Current Distortion Research Articles

A Family of Bridgeless Quasi-Resonant LED Drivers

A family of offline bridgeless quasi-resonant LED drivers is introduced. The prominent features of the proposed drivers are the capacitive isolation feature, inherent low line-current distortion, and high power factor. The concept is validated by a 30-W prototype operated in the range of 150–200 kHz and 30-V dc output (LED string voltage).

A Unity Power Factor Correction Preregulator With Fast Dynamic Response Based on a Low-Cost Microcontroller

Low cost passive power factor correction (PFC) and single-stage PFC converters cannot draw a sinusoidal input current and are only suitable solutions to supply low power levels. PFC preregulators based on the use of a multiplier solve such drawbacks, but a second stage dc-dc converter is needed to obtain fast output voltage dynamics. The output voltage response of PFC preregulators can be improved by increasing the corner frequency of the output voltage feedback loop. The main drawback to obtaining a faster converter output response is the distortion of the input current. This paper describes a simple control strategy to obtain a sinusoidal input current. Based on the static analysis of output voltage ripple, a modified sinusoidal reference is created using a low cost microcontroller in order to obtain an input sinusoidal current. This reference replaces the traditional rectified sinusoidal input voltage reference in PFC preregulators with multiplier control. Using this circuitry, PFC preregulator topologies with galvanic isolation are suitable solutions to design a power supply with fast output voltage response (10 or 8.33 ms) and low line current distortion. Finally, theoretical and simulated results are validated using a 500 W prototype.

Characteristics of a disc permanent magnet linear synchronous machine with back iron

A disc permanent magnet linear synchronous machine (DPMLSM) with back iron is presented in this paper. The proposed machine is to fulfil the requirements of high efficiency and large torque for electric vehicle (EV) applications. The back iron plays an important role in enhancing flux linkage and reducing flux leakage so that the designed machine has characteristics of high flux and power density to reduce the physical volume of EV. The steady-state, dynamic operating characteristics, and three-dimensional (3-D) finite element analyses are obtained to demonstrate the performance of the machine. Experimental results show that the proposed machine has a very low line current distortion with just a six-step inverter and a very wide range of operating speed without gear-ratio devices.

Operation of the LCC-type parallel resonant converter as a low harmonic rectifier

A single-phase high-frequency transformer isolated single-stage AC-to-DC controlled rectifier with low line current harmonic distortion using a variable-frequency controlled LCC-type (or series-parallel) resonant power converter (SPRC) is presented. A simple analysis and design procedure is used for designing the converter for low line current harmonic distortion and high power factor operation. The converter performance characteristics have been verified with SPICE3 simulations (without active control) and experimental prototype SPRC (rated at 150 W, with and without active control) for variation in load as well as line voltage. When operated with active current shaping, this converter operates in zero-voltage-switching mode for the complete range, maintaining power factor close to unity with low line current distortion and low peak current compared to the parallel resonant converter.