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This study introduces a new modified high-gain interleaved boost–flyback converter with pulse frequency modulation. In the proposed converter, a four-winding coupled inductor and a switching cell are utilized to achieve high voltage gain without requiring a large turn ratio. It presents soft commutation for a wide frequency range, the shared ground connection between source and load, continuous input current with low ripple, and low current oscillation even for cases with low-frequency output voltage ripple. These features make the proposed converter suitable for low-input voltage applications that require a high step-up gain, such as renewable energy systems. The proposed converter is analyzed in steady-state to provide the detailed principle of operation and characteristics, a static gain comparison, a design guide, and losses and efficiency analysis for all the components. Finally, experimental results were obtained from a 450-W prototype with an input voltage of 60/65 V, generating an output voltage of 480 V. The efficiency at peak power is 95.7%.

This article presents a design methodology to improve the power density of integrated converters operating at universal input voltage fulfilling the standards of connection to the grid and load. The proposed integrated two-stage converter is composed of the power factor correction (PFC) stage behaving as a current source to the bus, and the power control (PC) stage which provides continuous energy to the LED load. Traditionally, the low-frequency ripple (LFR) filtering process is performed by the bus capacitor placed in the output of the PFC stage, while the PC stage output capacitor works only as a high-frequency (HF) filter. The idea is to explore the lower and fixed operating voltage characteristics of the PC stage to share the LFR filtering with the PFC stage. Thus, a mathematical analysis is carried out, considering the influence of the LED characteristics, bus voltage, and capacitances to predict the LFR in the LED current. A case study, composed of an integrated buck and buck-boost converter to supply a 75 W LED load, is presented. For the traditional design method, the LED driver needs an 820 uF/160 V PFC bus capacitor and a 10 uF/80 V output capacitor to filter the HF components, representing a total capacitors’ volume of 17.9 cm3. With the proposed analysis, the optimized driver circuit requires a 220 uF/160 V PFC bus capacitor and a 470 uF/80 V output capacitor, resulting in a total capacitors’ volume of 9.7 cm3, providing a volume reduction of approximately 45%.

Energy efficiency plays a crucial role in the development of solar-powered standalone lighting systems, as it directly impacts both the system's autonomy and size, ultimately affecting the cost. In scenarios where a single converter simultaneously functions as both battery charger and LED driver, minimizing energy losses becomes challenging due to the different power levels processed in each mode. The use of gallium nitride (GaN) semiconductors in the converter helps achieving this goal as they allow for a wide range of switching frequencies, maintaining high efficiency even in light-load conditions. However, focusing solely on the converter's efficiency in each task may not necessarily minimize energy losses when considering its 24/7 operating characteristic and charger/driver time ratio. This study introduces a methodology tailored to select circuit components and switching frequencies within a GaN-based dual-purpose converter solution. The primary objective is to maximize system autonomy. A comprehensive analytical model of the converter's losses is paired with a search-based algorithm, enabling the evaluation of commercial components. This evaluation pinpoints the combination that minimizes energy consumption, ultimately leading to a more compact design that efficiently harnesses available resources. Experimental results are showcased for a system with a 30 W driver and 150 W charger, affirming the efficacy of the proposed design methodology. By meticulously selecting parameters, a high-efficiency converter can be realized. This achievement extends the system's autonomy by nearly an hour without necessitating changes to the battery pack's dimensions.

Although advantageous in several aspects, the integration of converters leads to a loss of independence between the converter's stages, since both stages are controlled by the same active switch. This condition makes it impractical to adopt control techniques that act on the duty-cycle to mitigate the low-frequency ripple at the output current without distorting the line current. The low-frequency ripple transferred from the bus voltage to the LED current has been studied for integrated converters operated at constant duty-cycle. To comply with IEEE 1789–2015 recommendation, the integrated converters use large capacitors to mitigate the low-frequency ripple. Converters operating in discontinuous conduction mode (DCM) have been widely adopted because they transfer less ripple to the output than converters operating in continuous conduction mode (CCM). A novel circuit arrangement for the buck-boost power control (PC) stage integrated with a buck-boost power factor correction (PFC) stage is explored in this paper as a technique to minimize the low-frequency output ripple for converters operating at constant duty-cycle and CCM. The proposed circuit provides current feedback to the bus capacitor, acting to reduce the output current and bus voltage low-frequency ripple. A dynamic model for the proposed converter in CCM is obtained and used to determine the output current modulation as a function of converter parameters. It is shown that the proposed topology leads to a smaller low-frequency ripple than a conventional counterpart at the same operating point. A 95 W design example and a prototype supplying an LED load of 98.8 V/960 mA for the proposed circuit and the conventional counterpart are presented. The experimental results show that the proposed arrangement can achieve similar results to the conventional circuit in efficiency, THD, or semiconductor stress, while the obtained output current modulation equals to 8.66% is 3.5 times lower than that in the conventional circuit at same operating point and component values.

This article presents a survey of light-emitting diode (LED) drivers for visible light communication by making a systematization of the most relevant published research. The modulator circuits were classified according to four types. To match the solutions with potential applications, power and efficiency ratings of conventional lighting and data rate of typical multimedia streaming are used as reference values. In conclusion, linear mode modulators (LMMs) lead the number of publications and switching mode modulators (SMMs) are a recent trend. SMMs can provide a good efficiency supporting power levels for indoor and outdoor luminaries and data rate for audio streaming. LMMs support video streaming given the higher data rates; however, the power rating corresponds to, at most, indoor illumination with significantly lower efficiency.

This work presents an analysis and a design methodology for a DC–DC LLC resonant converter applied to off-line LED driving. An investigation regarding the main design parameters that influence the LED low-frequency (LF) ripple has been carried out. The study was based on a mathematical analysis of the converter and employs numerical algorithms to solve a set of equations that accurately describe the converter behavior. Based on this analysis, a novel design methodology that allows for LF current ripple prediction has been devised. A numerical model has been developed to determine the LF current ripple transmission in DC–DC LLC resonant converters and provide a methodology for designing the bus capacitance in two-stage off-line LED power supplies. The work shows that the design of the LLC resonant converter for off-line LED driving is a trade-off between the converter efficiency and the LF ripple transmission. Experimental results were taken from two 46-W laboratory prototypes considering two different design goals: one for LF ripple reduction and another aiming at the highest converter efficiency and better power quality. Furthermore, the design of a two-stage LED driver based on an LLC converter taking into account the LF ripple transmission is also presented.

The development of high-frequency power converters is continuously improving their power density, efficiency and fast dynamic response. Among them, high-voltage-conversion-ratio (HVCR) dc–dc converters are widely used in high gain, i.e., step-up/-down or bidirectional applications, such as power supply for data center, dc micro-grids, electrical vehicle charging systems, etc. In this article, the current main high-frequency HVCR dc–dc converters are classified into inductive-based and capacitive-based approaches, which can then be described further by four kinds in detail, namely transformer-based, coupled-inductor-based, and switched-capacitor-based, as well as combination of coupled inductor and switched capacitor. A comprehensive analysis and comparison is given, which can provide guidance for proper topology selection and further topology optimization.

The reuse of the omnipresent LED lights for visible light communication (VLC) as a short-range data carrier may be an environmentally-friendly add-on to the radio frequency-based mobile network and make several new applications feasible. However, this comes with the price of additional lighting device complexity and also with lower energy efficiency, which can be measured by its consumption factor (CF) representing the data rate to the extra energy expense ratio (bits/J). This article addresses the choice of driver circuit type and data modulation strategy in a framework based on the known VLC channel, LEDs, and circuit models. Four applications of VLC are considered in the analysis: Li-Fi, virtual reality (VR), indoor localization (IL), and vehicular communication (VC). The main findings are that the reduced bit load and increasing bandwidth occupied by the modulation harm the efficiency of switching mode converters used as modulators, which were found to be cost-effective at low data rate applications of VLC, such as IL and VC. On the other hand, in higher data rate applications such as Li-Fi and VR, linear mode modulators are surprisingly more energy-efficient even when an extra step of power conversion is necessary to control average light or step down an unregulated supply voltage.

Visible light communication (VLC) shows up as a trend for short-range wireless networks. However, from the energy point of view, there is still a lack of light-emitting diode (LED) drivers that support considerable data rates with high efficiency. Common solutions would include switched-mode power converters (SMPCs), which are efficient, but they still face challenges regarding the modulation bandwidth (BW) for VLC. Thus, this article presents an analysis of a preemphasis (PE) technique to overcome the low BW constraint of the SMPC. The PE filter is used to render the frequency response of the circuit to provide a wider BW for communications. It operates on the duty cycle of the converter, and it dictates the average output signal value over a switching period. Finally, the technique is presented in a theoretical approach with the aligned experimental results in a 21.5-W buck-converter-based LED driver switched at 1 MHz, with 89% efficiency and an increased modulation BW from 8.12 to 450 kHz (55 times).

This article presents a resonant switched-capacitor (RSC) dc-dc converter for visible light communication (VLC) applications operating as both high-efficiency power converter and fast-response data transmitter. By operating under soft switching, the topology allows for higher switching frequency and higher slew rate so that the VLC functionality can be embedded into the power stage without an auxiliary switch. In the literature, this additional switch has been presented as a viable implementation of on-off-keying (OOK) and variable pulse position modulation (VPPM) for data transmission yet, at the same time, is a major efficiency bottleneck for higher transmission rates due to its inherent hard-switching operation. This justifies new efforts in enabling pulse-based transmission (PBT) without this additional switch. A 10-W prototype was built to demonstrate such feasibility, operating at a switching frequency of 500 kHz, resulting in nominal efficiency of 85% during data transmission under the VPPM scheme, achieving up to 100 kb/s for various brightness levels, over a distance up to 1m.

In this paper, a hardware emulator (HE) for organic light-emitting diodes (OLEDs) is proposed. Two OLED panels used in lighting applications are characterized based on a theoretical equivalent model (TEM). The objective is to better understand OLED operation and to infer about their electric static and dynamic behavior. From this, a HE able to represent the real behavior of an OLED panel using equivalent devices is proposed. The goal is to provide a useful tool for an adequate OLED driver design. In order to validate the HE, OLED samples were experimentally tested under static and dynamic operating conditions. The comparison between HE and OLED experimental results demonstrates a satisfactory accuracy.

This paper presents an optimization strategy for designing an offline light-emitting diode (LED) driver with a wide-bandwidth controller aimed at reducing the converter storage capacitance. The approach is based on the modeling of all the designing process as a nonlinear constrained optimization problem so that the power circuit elements and also the controller are designed, simultaneously in order to optimize a given parameter, such as the filtering capacitance or the total harmonic distortion. Although the low-frequency ripple compensation can insert a distortion in the input current of the converter, the proposed technique ensures that all the design requirements are fulfilled, including the IEC 61000-3-2 compliance, and also the maximum low-frequency ripple constraints. In order to verify the feasibility of the design procedure, the strategy was employed to an offline LED driver based on the integrated double buck-boost converter. Experimental results taken from a 75-W laboratory prototype, fed from a 220-V grid voltage, attested the proposed methodology.

When in 1907, Henry Joseph Round (1881–1966) published “A Note on Carborundum,” in Electrical World, 49, pp. 309, reporting the electroluminescence effect on a carborundum (SiC) crystal, little he knew about the huge impact that his discovery would cause in the lighting industry 100 years later. Unfortunately, carborundum proved impractical for light production, mainly due to its very low conversion efficiency. Thus, it was not until the early 1960s, when the first commercial GaAs-based light-emitting diodes (LEDs) were produced. Since then, LED technology has experienced a continuous improvement, especially intense during the 1990s, which led to the great number of applications that we can enjoy nowadays.