A Novel High-Power-Factor Electrolytic-Capacitorless LED Driver Based on Ripple Port

The Weinberg converter is a suitable choice for the battery discharge regulator of a geostationary satellite due to its high efficiency, continuous input and output current, and soft switching of switches and diodes. Nevertheless, this converter has high output current ripple during the commutation period of its output diodes. Therefore, the output RMS current and output voltage ripple are high, which may directly affect the lifetime and total capacitance of bus capacitors and hence, the lifetime and volume of the geostationary satellite. Thus, reducing the output current ripple is important to the design of the geostationary satellite. An improved Weinberg converter with an additional inductor and capacitor is proposed in this paper to reduce the output current and voltage ripple. It features soft switching of all switches, no reverse recovery problems of the diodes, and reduced magnetizing offset current in the coupled inductor. The proposed converter is verified with experimental results from a 750W, 100kHz, 36-50Vdc prototype.

The proposal of this paper is a modular three-phase ac-dc light-emitting diode (LED) driver for high-power luminaires based on LEDs that uses each phase to control an independent LED load removing in the process both the electrolytic capacitor and the second stage to increase both the lifetime and the efficiency. The driving of each LED load is done by means of a dc-dc converter operating as a loss-free resistor responsible for controlling the current across it. Furthermore, each dc-dc converter needs to achieve power factor correction (PFC) to comply with the restrictive IEC 61000-3-2 class C requirements, hence, achieving unity power factor and low total harmonic distortion. Taking advantage of the light properties, the output of the LED driver will be the sum of the light of each of the phases. Therefore, a theoretical study will be carried out to observe the feasibility of removing the electrolytic capacitor while guaranteeing a flicker-free behavior of the LED luminaire, even if the current of each string is pulsating at twice the mains frequency. This particular performance under high output current and voltage ripples requires reevaluating the well-known limits between the conduction modes in PFC converters. In addition, the theoretical analysis also discusses and proposes control methods for the LED driver, which thanks to its modularity can easily scale in power to drive high-power luminaires. In order to validate the theoretical analysis, a prototype has been built comprised three PFC boost converters disposing of their electrolytic capacitors. The designed prototype operates in the full range of the European three-phase line voltage, which varies between 380 and 420 V, and supplies an output light of 42.000 lm at a maximum power of 300 W while achieving an electrical efficiency of 97.5%.

In this paper, a light-emitting diode (LED) driver with a high power factor (PF) and low-frequency current ripple suppression over a wide input range is presented, and a flyback converter is designed to operate in the discontinuous conduction mode (DCM), with a digital controller used to keep the duty cycle constant for half of the utility cycle under a fixed load and input voltage. This method ensures that the input current is in phase with the universal input voltage, thus achieving a high power factor without utilizing feedforward control. Furthermore, on the secondary side, the time of the zero point of the utility voltage can be attained so that the duty cycle can be updated at this time. In addition, a simple auxiliary circuit is connected parallel to the output side to absorb the excess output current of the flyback converter or to release the current to the load to make up for the shortage of the output current of the flyback converter so that the low-frequency ripple of the output current can be inhibited. There are only two current-detecting resistors used in this study: one is the output current-sensing resistor of the flyback converter, and the other is the output current-sensing resistor of the auxiliary circuit.

Switched-mode dc-dc converters are used to regulate dc voltages or currents at a certain desired level. Due to inherent switching action, currents and voltages in the circuit tend to oscillate around a given average value, as the output values present some ripple in steady-state condition. The low-frequency output current ripple (OCR) is a key parameter for design considerations when a light-emitting diode (LED) string load is considered. In order to compare their ripple magnitudes under distinct conditions regarding a buck-based LED driver operating in continuous conduction mode (CCM), this paper analyzes the conventional voltage mode control as well as the peak-current mode control in order to compare its OCR responses by the classical control theory. The methods are implemented considering the same control bandwidth so that a proper comparison can be established.

This paper proposes a hybrid filter structure consisting of a passive power filter and a DC active power filter (DCAPF) applied in high current, high precision and low ripple accelerator power supplies. The configuration of the power system with the DCAPF is firstly introduced. Then four control schemes to obtain the reference signal for the DCAPF control circuit is presented. For each method, the basic operation principle of eliminating output voltage and current ripples is analyzed in detail. Furthermore, the compensation characteristics of each method is discussed and compared. To verify the proposed circuit configuration and the control methods, the testing results of the practical field operation of the DCAPF with a 120kW accelerator power supply is introduced. By adopting the control method of detecting the load ripple voltage, the output current ripple factor and tracking accuracy of the accelerator power supply achieve 8.87/spl times/10/sup -6/ (peak-to-peak) and 1/spl times/10/sup -4/ respectively, which is very satisfactory for this kind of power supplies. The dynamic response of the accelerator power supply is also greatly improved through the application of the DCAPF.

This brief proposes a thorough methodology for the steady-state characterization of input and output current ripples in discontinuous conduction mode (DCM) interleaved power converters, under inductance mismatch. The proposal analyzes total ripple for any number of phases, any inductance ratio and operating point. Furthermore, calculation of amplitude, rms value and harmonic content of total input and output current ripples is presented. Experimental tests on a 5-phase boost converter are conducted under different conditions to verify the presented method.

This paper presents the modeling and control of a DC-DC buck converter with reduced output ripple which is achieved without additional switching devices. The converter results from replacing the LC output network in a conventional buck converter for an LCL network which is proposed to be implemented by using coupled inductors. Low output ripple is required when dealing with sensitive loads as in LED lighting applications and high precision test equipment. The functionality of the buck converter is preserved and the output current and voltage ripples are highly reduced. Active damping must be provided in order to mitigate resonant behaviors. A model-based controller is proposed which achieves active damping and output voltage regulation. A main feature of this controller is that it has an estimation scheme that deals with power change conditions under a constant output voltage. Numerical simulations are presented to evaluate the closed-loop performance.

A ripple current cancellation technique injects AC current into the output voltage bus of a converter that is equal and opposite to the normal converter ripple current. The output current ripple is ideally zero, leading to ultra-low noise converter output voltages. The circuit requires few additional components, no active circuits are required. Only an additional filter inductor winding, an auxiliary inductor, and small capacitor are required. The circuit utilizes leakage inductance of the modified filter inductor as all or part of the required auxiliary inductance. Ripple cancellation is independent of switching frequency, duty cycle, and other converter parameters. The circuit eliminates ripple current in both continuous conduction mode and discontinuous conduction mode. Experimental results provide better than an 80/spl times/ ripple current reduction.

The life cycle of the Light Emitting Diodes (LEDs) requires a robust and reliable driver since the components may have influence in the lifetime of the lighting system, which is an undesirable situation. In addition, LED strings can be sold for different loads possibilities. This requires the converter components to be designed in a generalized and oversized way. As a consequence, sizable components lead to increased losses mainly in the semiconductors. In the last ones, the forward voltage drops and resistances typically increase relatively to their voltage blocking capacity. This work presents a steady state and dynamic modeling of a SEPIC converter operating in Discontinuous Conduction Mode (DCM) for LED lighting applications, considering non-idealities. Simulations and Hardware-in-the-Loop results are presented to validate the derived dynamic and steady-state models as well as to present a DCM PFC SEPIC rectifier application driving a 72 V-100 W LED lamp from a 220 V-60 Hz grid.

This paper presents an analysis and design of a unidirectional resonant switched capacitor (URSC) step-up converter for OLED lamp driving. The URSC converter includes a very small inductor in series with the switched capacitor to improve the switching behavior. Also, the URSC converter presents the advantages of high power density, higher efficiency compared to other SC converters, low output voltage and current ripples and low EMI noise, which make it adequate for driving OLED lamps. URSC is designed to operate in closed loop with constant current VI control technique. By working the resonant inductor as a VI, the OLED current can be regulated and dimmed because of resonant frequency change. Simulation and experimental results of the VI inductor, which are in a good agreement, and the results of a URSC step-up converter design example for a 21.8 W OLED lamps array supplied from 48Vdc are presented, where a maximum 91.5% efficiency is obtained.

To balance the cost and volume when applying a low output current ripple, the power supply design should be able to eliminate the current ripple under any duty cycle in medium and high switching frequencies, and considerably reduce filter volume to improve power density. A stacked buck converter was eventually selected after reviewing the existing solutions and discussing their advantages and disadvantages. A stacked buck converter is used as a basis to propose the transient response and output current ripple elimination effect, boundary limit control method, and low output ripple dead time modulation method to make individual improvements. The principle, mathematical derivation, small-signal model, and compensator design method of the improvement method are presented in detail. Moreover, simulation results are used to mutually verify the correctness and effectiveness of the improvement method. A stacked buck converter with 330-V input, 50-V output, and 1-kW output power was implemented to verify the effect of the low output current ripple dead time modulation. Experimental results showed that the peak-to-peak value of the output current ripple was reduced from 2.09 A to 559 mA, and the RMS value was reduced from 551 mA to 91 mA, thereby effectively improving the output current ripple.

In order to meet the high performance and efficiency requirements, a new space vector-based discontinuous modulation strategy for neutral-point clamped three-level inverter is presented in this paper. Different from the conventional discontinuous PWM (DPWM) strategies, a new clamping state is applied to synthesize the reference voltage under the condition of low modulation index. The rms value of output current ripple for different clamping states are calculated, and then the distribution of the new clamping state and the other two clamping states adopted in conventional DPWMs is optimized based on the calculation results. The switching sequences are redesigned according to the new distribution of the three clamping states. The output voltage and current, switching loss, neutral-point voltage ripple and the common mode voltage of the proposed DPWM strategy and DPWM0–DPWM3 are compared by simulation and experimental results. The results show that by the use of the proposed strategy, the values of total demand distortion of output current ( I TDD) and weighted total harmonic distortion of output voltage $({\boldsymbol{V}_{{\mathbf{WTHD}}}})$ are the lowest. Furthermore, the product of switching loss and $I_{\rm TDD}$ of the proposed strategy maintains the lowest within a large range of modulation index-load angle plane. It can be concluded that the utilization of the new clamping state and optimal distribution of different clamping states could enhance the output performance of the inverter. Moreover, the high-efficiency requirement can also be realized at the same time.

The interleaving technique is required for LLC resonant converters to achieve high power levels, handle higher input/output currents, and reduce output current ripple. However, the high system efficiency and the low output current ripple for the multi-phase LLC resonant converter cannot be achieved at the same time at low and medium power levels. Most methods try to keep the multi-phase LLC resonant converter in load-sharing mode regardless of the power level, which will result in low system efficiency at low and medium power levels. In this paper, an output current ripple and efficiency optimal control method with finite load distribution schemes is proposed for the multi-phase LLC resonant converter to balance the efficiency and output current ripple. The optimal control method improves the efficiency as much as possible while keeping output current ripple low. According to the calculation of output current ripple and efficiency, the optimal load distribution scheme is selected. The pulse-frequency modulation (PFM) and phase-shift modulation (PSM) hybrid control is applied to regulate the load of each phase. An analysis is provided, and a 540-W three-phase interleaved LLC resonant converter is built to verify the superiority.

The aim of the experiment was to assess the effects of supplemental lighting of cucumber grown in greenhouse using lamps with differentiated light spectra: sodium lamps – high-pressure sodium (HPS) and light emitting diodes (LEDs). Plants (cucumber ‘Pacto’ F 1 ) were grown in two greenhouse compartments with five light treatments: I – HPS + LED (top light with HPS LEDs as interlighting), II – only HPS as top light, III – LED R (LED chips on board (COB) type with an increased level of red band), IV – LED W (LED COB type, white), V – LED B (LED COB type with an increased level of blue spectrum). Light treatments: HPS + LEDs and HPS were grown in one greenhouse compartment and the other three light treatments: LED R (red light supplementation), LED W (without additional supplementation) and LED B (red spectrum supplementation) in the second compartment in analogous climatic conditions. The LED lamps using COB technology are known to be a very efficient source of light. Plants were cultivated from December 2018 to March 2019 in mineral wool slabs Grotop Master (100 × 15 × 10) with four plants on one mat. They were illuminated for 18 h (from 5 am to 11 pm), setting the threshold value (on and off) at 130 W. The plants were drip-irrigated with a complete nutrient solution. The irrigation was controlled based on a weighting system. The assessment of the effect of lighting on early yield and quality of cucumbers was completed after 8 weeks of cropping. It was shown that it was possible to obtain 3.59 kg from one plant during the 8-week period of evaluation by illuminating plants with sodium lamps (HPS), while using HPS and LEDs as additional illuminated inter-rows 3.89 kg. The yield of plants illuminated by LED lamps varied depending on the variant of the spectrum used and was respective for LED R, LED W and LED B, 3.30 kg, 3.90 kg and 3.25 kg. The obtained results indicated that the yield of cucumber ‘Pacto’ F 1 grown with HPS lamps at top lighting and at the same time using interlighting with LED lamps was similar to LED W lamps (i.e. without additional supplementation in the range of red (LED R) and blue (LED B) light). Due to good results of LED lamps (type COB for top lighting or as interlighting) used for the cucumber supplemental lighting and high energy efficiency of LEDs, the promising future for that type of lamps compared with traditionally used HPS during winter cultivation in a greenhouse was demonstrated.

This paper presents an analysis of input and output ripples of PWM AC choppers. Expressions of input and output current and voltage ripples of single-phase PWM AC choppers are first derived. The derived expressions are then extended to three-phase PWM AC choppers. As input current and output voltage ripples specification alone cannot be used to determine the unique values of inductance and capacitance of the LC filters, an additional criterion based on the minimum reactive power is proposed. Experimental results are included in this paper to show the validity of the proposed analysis method.