Y.K. Cheng

Bio: Y.K. Cheng is an academic researcher. The author has contributed to research in topics: LED lamp & LED circuit. The author has an hindex of 1, co-authored 1 publications receiving 124 citations.

General Study for using LED to replace traditional lighting devices

Abstract: High power LED provides a high luminous and high efficient for using as a lighting source. Because of the advent for LED as lighting device, LED lighting becomes one of the new trends in the lighting industry. In this paper, the power circuit design based on the constant current flyback and the heat distribution matter are discussed. The aims of the work are provide a solution for using LED to replace the traditional lighting device.

Step-Up DC–DC Converters: A Comprehensive Review of Voltage-Boosting Techniques, Topologies, and Applications

Abstract: DC–DC converters with voltage boost capability are widely used in a large number of power conversion applications, from fraction-of-volt to tens of thousands of volts at power levels from milliwatts to megawatts. The literature has reported on various voltage-boosting techniques, in which fundamental energy storing elements (inductors and capacitors) and/or transformers in conjunction with switch(es) and diode(s) are utilized in the circuit. These techniques include switched capacitor (charge pump), voltage multiplier, switched inductor/voltage lift, magnetic coupling, and multistage/-level, and each has its own merits and demerits depending on application, in terms of cost, complexity, power density, reliability, and efficiency. To meet the growing demand for such applications, new power converter topologies that use the above voltage-boosting techniques, as well as some active and passive components, are continuously being proposed. The permutations and combinations of the various voltage-boosting techniques with additional components in a circuit allow for numerous new topologies and configurations, which are often confusing and difficult to follow. Therefore, to present a clear picture on the general law and framework of the development of next-generation step-up dc–dc converters, this paper aims to comprehensively review and classify various step-up dc–dc converters based on their characteristics and voltage-boosting techniques. In addition, the advantages and disadvantages of these voltage-boosting techniques and associated converters are discussed in detail. Finally, broad applications of dc–dc converters are presented and summarized with comparative study of different voltage-boosting techniques.

Enabling vehicular visible light communication (V2LC) networks

Abstract: Visible Light Communication (VLC) is a fast-growing technology to provide data communication using low-cost and omni-present LEDs and photodiodes. In this paper, we examine the key proper-ties in enabling vehicular VLC (V2LC) networks as follows. We first develop a custom V2LC research platform on which we expe-rimentally evaluate the feasibility of a V2LC system under working conditions in relation to link resilience to visible light noise and interference. Our experiments show that a receiver's narrow field-of-view angle makes V2LC resilient to visible light noise from sunlight and legacy lighting sources as well as to interference from active VLC transmitters. Then, by leveraging our experimental characterization as the basis of modifications to our simulator, we examine V2LC's performance in providing network services for vehicular applications. Our key findings include: (i) in dense vehicular traffic conditions (e.g., urban highway during peak hours), V2LC takes advantage of multiple available paths to reach vehicles and overcomes the effects of packet collisions; (ii) in the presence of a visible light blockage in traffic, V2LC can still have a significant number of successful transmissions by opportunistically using dynamic inter-vehicle gaps.

Current source ballast for high power lighting emitting diodes without electrolytic capacitor

Abstract: An LED driver requiring no electrolytic capacitor in the whole power conversion process is presented It consists of two power conversion stages The first stage is a buck converter operating in discontinuous capacitor voltage mode, so that the input current is continuous It is used to deliver a regulated current for the second stage The second stage is a current-fed inverter, in which the semiconductor switches are operated at constant switching frequency and constant duty cycle of 05 The power supplying to the LED string is regulated by controlling the duty cycle of the main switch in the front-stage buck converter The two stages are interconnected by an LC filter, which is designed to attenuate harmonics at double of the line frequency Instead of using an electrolytic capacitor for the filter, a polyester capacitor of better lifetime expectancy is used An 18 W experimental prototype has been built and tested

Smart Personal Sensor Network Control for Energy Saving in DC Grid Powered LED Lighting System

Abstract: Emerging smart grid technologies aim to renovate traditional power grid by integrating intelligent devices and their communications for monitoring and automation of the power grid to enable efficient demand-side energy management. In this paper, energy management in smart dc building grid powered dc electrical appliances like lighting is investigated, in particular energy savings from proposed personal lighting management strategy. Unlike conventional fluorescent lamps powered mainly by ac grid, LED luminaires are dc in nature, thus results in significant power conversion losses, if operate on traditional ac powered system, are analyzed with proposed dc distribution building grid for LED lighting. This paper continues to explore the use of smart wireless sensors for personal control of the dc grid powered networked LED lighting. Experimental results show that the proposed smart LED lighting system with an energy saving mechanism incorporated is able to achieve similar lighting performance as the conventional lighting condition, while at the same time, able to attain about 44% energy saving as compared to the original ac fluorescent system. For a low voltage dc grid being implemented, the maximum power loss and voltage drop of the developed dc distribution building grid are 2.25% and 3% respectively.

A Simple Current-Balancing Converter for LED Lighting

Abstract: In this paper, a current-balancing converter is proposed herein and applied to driving LED strings paralleled, so as to make the required current shared among LED string. There are two stages of the proposed current-balancing converter. The first stage is one buck converter under constant current control and transfers DC current to AC current, whereas the second stage is passive AC-DC rectifiers with front-end current-balancing transformers. Some experimental results, together with a simple mathematical derivation, are provided to verify the proposed scheme.