Active Ripple Compensation Research Articles

Frequency-Based Active Ripple Compensation Technique to Reduce Bulk Capacitance in Integrated Offline LED Drivers

In order to increase the power density and the lifespan of LED drivers, several studies have proposed Active Ripple Compensation (ARC) techniques for minimizing the converter bulk capacitance. However, a common side-effect of the ARC method is the increase in the Total Harmonic Distortion (THD) of the converter input current. In this context, a frequency-based ARC technique is proposed as an alternative to the conventional ARC methodology, in which the duty-cycle is modulated. The analyses presented in this paper show that the frequency-based ARC approach applied to resonant converters has a better performance than the one used in hard-switching converters, since it allows for a huge capacitance reduction with a small THD increase. Furthermore, this paper presents a generalized analysis of ARC techniques applied to integrated off-line LED drivers, which reduce the number of components and the overall LED driver cost. The input current harmonic content and the output ripple reduction have been theoretically predicted for several converters. Experimental results gathered from a 96-W laboratory prototype supplied from a 127-V 60-Hz grid attested the superior performance of the frequency-based active ripple compensation, since a capacitance reduction of 66.6% has been obtained with an increase of only 0.9% in the THD.

A Constant On-Time Control With Internal Active Ripple Compensation Strategy for Buck Converter With Ceramic Capacitors

Constant on-time control has been widely used due to its advantages of fast transient response and light load efficiency. However, the control scheme is intrinsically unstable if the output capacitor's equivalent series resistance (ESR) is not large enough, which needs ripple injection techniques to enhance loop stability. The traditional passive ripple compensation technique uses only passive component networks to realize this function, which exhibits some inherent shortcomings, including difficulties in high-speed current sensing amplifier design and large chip area consumption. This paper proposes an internal active ripple compensation strategy that senses the low-side power mosfet current and extracts relevant ac information for feedback-ripple enhancement. Output-voltage dc offset does not occur and subharmonic instability is significantly improved even with ceramic capacitors. The circuit architecture has been realized in a synchronous buck regulator with a 0.5 μm 40 V bipolar-CMOS-DMOS (BCD) process. The programmable switching frequency is up to 1 MHz and the maximum load current is 4 A. Simulation and experimental results are given to prove the proposed high performance.

Optimized capacitive active ripple compensation topology for a 3.7 kW single-phase high power density on-board charger of electric vehicles

In this paper, a comprehensive investigation of the capacitive active ripple compensation (ARC) techniques is made to conclude which one is optimal to be used in on-board chargers of electric vehicles. Crucial aspects in such an application are: lifetime, volumetric and specific power density (including components’ size and the needed cooling solution), and overall efficiency of the charger. As presented in this paper, all capacitive ARC topologies (buck, boost, and buck–boost) have successfully diverted the low-frequency ripple from the dc side with a maximized power density. The ARC circuit consists of two additional switches, a smoothing auxiliary inductor, and a storage auxiliary capacitor. Finally, the buck capacitive ARC topology proves to be the optimal ARC technique for on-board chargers because of its maximal power density, minimal loss behavior and voltage stress, and long lifetime capability as it requires a downsized capacitance to the extent, where film capacitors or ceramic capacitors can replace the normally used bulky electrolytic capacitors. The performance of the three capacitive ARC techniques is proved by simulation results.

LLC LED Driver Small-Signal Modeling and Digital Control Design for Active Ripple Compensation

This paper presents a new approach for the small-signal modeling of the dc–dc LLC resonant converter aimed to supply high-power light-emitting diodes (LEDs). This small-signal modeling procedure is based on the extended describing function method, where for a reliable small-signal model of the LLC LED driver, the equivalent piece-wise linear circuit of the LED has to be considered under some conditions throughout the model development. Otherwise, the obtained model does not reflect the real dynamic behavior of the converter. Furthermore, a numerical analysis is presented showing the conditions where the proposed model better describes the real dynamic behavior of the converter in relation to the traditional approach where the LED is modeled by an equivalent resistance. From the obtained model, the feedback compensator is designed and implemented in order to track the average current reference and avoid output current ripple, consequently sidestepping output light modulation (flicker). Experimental results show the feasibility of the proposed small-signal model and the active ripple compensation through a dimmable digitally controlled LLC LED driver under closed-loop operation.

Investigation of the Active Ripple Compensation Technique to Reduce Bulk Capacitance in Offline Flyback-Based LED Drivers

This paper presents the study of an offline flyback-based light-emitting diode (LED) driver with reduced storage capacitance. An approach called active ripple compensation was used for minimizing the converter bulk capacitance. This technique is oriented to voltage-controlled pulse width modulation converters and is based on the modulation of the duty cycle, which allows for the reduction of the filtering capacitance by increasing the harmonic content of the input current up to the limits established by the standards. By means of the design procedure presented in this paper, the amount of capacitance reduction and input current distortion can be fully controlled and theoretically predicted. In addition, no extra sensors are required to implement the proposed technique, apart from the LED current sensor already available in most LED drivers. Experimental results from a 50-W laboratory prototype supplied from a 220-V 60-Hz grid were carried out. The results were compared with the conventional approach, attesting the superior performance of the proposed methodology.

Design and Simulation of VLC Transmitting System

Low ripple and large bandwidth VLC (Visible Light Communication) transmitting system driven by switching current source is designed to use common LED as transmitter for VLC. Active ripple compensation circuit is designed to eliminate inductance current ripple of switching current source. Wallman differential circuit is adopted to realize LED brightness modulation for transferring information. Simulation results show that the design of VLC transmitting system meets the needs of VLC.

A High Power Density Integrated Charger for Electric Vehicles with Active Ripple Compensation

This paper suggests a high power density on-board integrated charger with active ripple compensation circuit for electric vehicles. To obtain a high power density and high efficiency, silicon carbide devices are reported to meet the requirement of high-switching-frequency operation. An integrated bidirectional converter is proposed to function as AC/DC battery charger and to transfer energy between battery pack and motor drive of the traction system. In addition, the conventional H-bridge circuit suffers from ripple power pulsating at second-order line frequency, and a scheme of active ripple compensation circuit has been explored to solve this second-order ripple problem, in which a pair of power switches shared traction mode, a ripple energy storage capacitor, and an energy transfer inductor. Simulation results in MATLAB/Simulink validated the eligibility of the proposed topology. The integrated charger can work as a 70 kW motor drive circuit or a converter with an active ripple compensation circuit for 3 kW charging the battery. The impact of the proposed topology and control strategy on the integrated charger power losses, efficiency, power density, and thermal performance has also been analysed and simulated.