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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.

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.

Nowadays, an intensive development of multilevel inverters has been seen in hybrid and fuel cell electric vehicles. For this, a high voltage cascade inverter with step pulse PWM strategy is an applicable topology as it can reduce electromagnetic interference as well as switching losses on power devices. The converter is usually controlled with a look-up table of commutation angles, which are computed off-line base on an assumption of equal dc voltage sources. However, in reality, the inequality of these dc voltage sources can occur due to different charging/discharging processes and this reduces the quality of output voltages such as the existence of low order harmonics and an error in fundamental voltage. To overcome this problem, PWM angles in the look-up table can be changed according to different cases of dc source variation. However, this solution may require a large memory for the look-up table. Thus, off-line PWM stratergy in case of dc voltage source variation may not be a suitable approach to control the converter. In this paper, an on-line step pulse PWM method will be proposed to control fundamental voltage and reduce the amplitudes of low-order harmonics to possibly low values. Similar to the original on-line method, the control principle between two defined trajectories will be appropriately modified for solving the problem. The principle is mathematically formulated, and demonstrated by simulation results.