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Density functional calculations are performed to study the energetic, structural, and electronic properties of graphene and silicene functionalized with hydrogen. Our calculations predict that H atoms bind much more strongly to silicene than to graphene. The adsorbed H atoms tend to cooperatively stabilize each other leading to a two-dimensional nucleation and growth mechanism. The different structural and electronic modifications induced by H in fully functionalized graphene and silicene (known as graphane and silicane) are also explained. Finally, the electronic properties of defective graphane with multiple hydrogen vacancies are investigated. Engineering the vacancies in graphane offers a way to modify the electronic properties of this material.

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Pulse width modulation strategies have been developed for indirect matrix converters (IMCs) in order to improve their performance. In indirect matrix converters, the LC input filter is used to remove input current harmonics and electromagnetic interference problems. Unfortunately, due to the existence of the input filter, the input power factor is diminished, especially during operation at low voltage outputs. In this paper, a new space vector modulation (SVM) is proposed to compensate for the input power factor of the indirect matrix converter. Both computer simulation and experimental studies through hardware implementation were performed to verify the effectiveness of the proposed modulation strategy.It is well known that the poor input power factor induces negative effects on AC power source utilization, as well as increasing the magnitude of the electric current more than is necessary.

This paper presents the implementation of a two-stage light-emitting diode (LED) driver based on commercial integrated circuits (IC). The presented LED driver circuit topology, which is designed to drive a 150 W LED module, consists of two stages: AC-DC power factor correction (PFC) stage and DC/DC power converter stage. The implementation of the PFC stage uses IC NCP1608, which uses the critical conduction mode to guarantee a unity input power factor with a wide range of input voltages. The DC/DC power converter with soft-switching characteristics for the entire load range uses IC FLS2100XS. Furthermore, the design of an electromagnetic interference (EMI) filter for the LED driver and the dimming control circuit are discussed in detail. The hardware prototype, an LED lighting system, with a rated power of 150 W/32 V from a nominal 220 V/50 Hz AC voltage supply was tested to show the effectiveness of the design. The presented LED driver was tested for street lighting, and the experimental results show that the power factor (PF) was higher than 0.97, the total harmonics distortion (THD) was lower than 7%, and the efficiency was 91.7% at full load. The results prove that the performance of the presented LED driver complies with the standards: IEC61000-3-2 and CIRSP 15:2009. Electronics 2020, 9, 52 2 of 22There are three types of LED driver systems: Single-stage [10,11], two-stage [12][13][14], and integrated LED drivers [15,16]. The single-stage LED driver is an AC/DC converter that provides a constant output current for the LED and a unity power factor. The two-stage system consists of two separate stages, an AC/DC power factor correction (PFC) converter and a DC/DC converter. Recently, some integrated topologies were introduced in order to reduce the size and cost. Single-stage and integrated solutions have some advantages such as low-cost designs and high efficiency due to only one energy conversion. However, the PFC of these topologies causes a high-output voltage ripple due to the absence of electrolytic capacitors. Hence, the low-frequency current ripple makes LEDs flicker. These single-stage and integrated solutions are not suitable LED street lighting systems and are instead used for LED-based replacement lamps where small-size converters are needed. Furthermore, the bridgeless topologies usually generate high electromagnetic interference (EMI) due to large dv/dt and di/dt. The two-stage topology is the most popular topology for LED drivers above 100 W [17]. In the two-stage LED driver, the constant output current regulation is more easily implemented due to the bus voltage. Additionally, an isolated DC-DC stage is needed in the LED driver in order to ensure constant current control.Recently, there have been several commercial analog integrated circuits (ICs) available on the market that are recommended for a high power factor and low cost with a high efficiency. These commercial ICs fulfil the IEC 1000-3-2 Class C, but the total harmonics distortion (THD) is higher than 20% [18]. In reference [19], a reson...