Ripple current cancellation circuit

The flyback converter is widely used in modern power conversion systems due to its simple topology, single switch, low component count, and inherent galvanic isolation. This paper investigates the performance characteristics of flyback converters by analyzing their operation in Continuous Conduction Mode (CCM) and Discontinuous Conduction Mode (DCM), with particular emphasis on voltage spike behavior. The main contribution of this study is the development of a mathematical model that correlates the operating mode (CCM or DCM) with the voltage spike across the power switch. In addition, the study examines the impact of duty cycle variations on voltage spike behavior. The results show that, for comparable operating conditions and moderate duty cycles, CCM operation generally results in lower voltage spikes than DCM due to reduced peak magnetizing current, while at higher duty cycles and load levels, CCM may exhibit increased voltage stress. The proposed approach was validated through MATLAB/Simulink simulations and a scaled-down experimental prototype. A proportional integral (PI) controller is implemented in simulation to ensure regulated output voltage under practical operating conditions. The results demonstrate that optimizing the duty cycle and accounting for the influence of conduction mode can enhance the reliability of flyback converters, making them suitable for applications requiring galvanic isolation and cost-effective solutions.

Three-level inverter has been widely used in electric drives and renewable power generation system. However, the common mode voltage (CMV) and output current ripple reduction of three-level inverter should be carefully regulated for the appropriate operation. As these two targets are mutually interrelated, the conventional space vector modulation (SVM) scheme cannot cope with them decently. To overcome this drawback, this paper proposes a novel modified SVM scheme to realize CMV and current ripple reduction simultaneously. The generating mechanism of output current ripple is analyzed, and the relationship between current ripple and utilized vectors is quantitatively described. Based on the analyses, the proposed optimal current ripple and CMV reduction pulse width modulation (OCR-CMVRPWM) method adopts four voltage vectors (large, medium, small and zero vectors) to reduce root mean square (RMS) value of current ripple by allocating the sequence and dwell times of utilized vectors. Compared to the existing PWM methods, the proposed OCR-CMVRPWM scheme can reduce the peak of CMV to half of value using the conventional SVM, and obtain a significant reduction of output current total harmonic distortion (THD). The effectiveness of the proposed method is validated by both simulation and experimental results.

Current-Fed Switched Inverter (CFSI) is widely used due to its higher gain and inherent shoot-through protection. To account for the pulsating power output of the single phase CFSI, the passive storage elements (inductor and capacitor) of its boost stage contains a second harmonic component. As a result, the peak-to-peak ripple in the inductor current increases. This increased ripple forces the CFSI to have Discontinuous Conduction Mode (DCM) during light load condition. This distorts the AC output voltage of the CFSI. To avoid DCM, the peak-to-peak ripple in inductor current must be reduced. This paper presents a control based approach, in which second harmonic component of the inductor current is suppressed. This expands the boundary range of Continuous Conduction Mode (CCM) in a CFSI and improves its light load range. The proposed control scheme is validated for CFSI using a 500 W prototype, and it shows that the peak to peak ripple in the inductor current is reduced from 6.04 A to 2.76 A for a resistive load. This results the CCM boundary is extended by 54.3 % for a DC input of 35 V and AC output of 61 V (RMS).

The coupled inductor single input dual output (CI-SIDO) converters have applications in portable electronic devices, electric vehicles, hybrid energy systems, renewable energy systems, etc. The coupled inductors present in the converter helps to reduce the physical size of the converter and also helps to reduce the ripples in input and inductor currents. The CI-SIDO converters are generally operated in continuous conduction mode (CCM) because of the load-independent input-output voltage relations and control. However, once the converter is designed and used, loads of the converter may reduce, leading to the discontinuous conduction mode (DCM). Therefore, the DCM analysis is essential when the converter is used in practical applications. This paper presents the DCM operation of the CI-SIDO boost converter. The DCM operations depend on the inductor current waveforms. As illustrated in the literature, the CI-SIDO boost converter has numerous inductor current waveforms depending on the voltages and coupled inductor parameters. As the analysis of each waveform in DCM is very tedious, this paper presents the DCM operation when the two inductor current slopes are opposite to each other. With these slope conditions, it is found the CI-SIDO boost converter has eight different DCM waveform possibilities. Each waveform is analyzed separately, and the output-input voltage relations are found for each case. The analysis is verified by simulations in Matlab/Simulink.

Dual Randomized Pulse Width Modulation (DRPWM) is renowned for its better effectiveness than Simple Randomized Pulse Width Modulation (SRPWM) in reducing conducted Electro-Magnetic Interferences (EMI) in power converters. However, the introduction of low-frequency ripples into the output voltage by dual randomization has not yet been addressed; this effect is investigated in this paper for a buck converter operating in both the continuous conduction mode (CCM) and the discontinuous conduction mode (DCM). First, the modulating principle is presented. Then, a general analytical expression for power spectral density (PSD) of the input current is derived and validated for the proposed DRPWM scheme for both the CCM and DCM. A comparison of the PSDs of the input current for all RPWM schemes in both the CCM and DCM shows the PSD spreading effectiveness of the dual scheme as compared to simple schemes. Finally, the low-frequency output ripple is analysed using the PSD of output voltage. The results reveal that the output voltage ripple is affected by all the randomized schemes in both the CCM and the DCM. Also, the dual scheme (RCFM-RPPM) introduces the highest low-frequency voltage ripple, especially in the CCM and for low duty cycles. In DCM, the RPPM scheme gives the lowest voltage ripple, while the RCFM scheme gives the lowest voltage ripple in the CCM. The results are confirmed by both theory and simulations.

This paper analyzes a coupled inductor based $LL$ – $LC$ network as a building block to achieve input or output current ripple cancellation in power converters. The proposed current ripple cancellation technique works on the principle of inductance matching. It also provides reduced current stress on the switching devices of the converter compared with the other current ripple cancellation networks discussed in the literature. The current ripple cancellation technique is verified in achieving input and output current ripple minimization in different converters. The effect of inductance mismatch, inductor and capacitor tolerances, and circuit parasitic is also studied. Some of the published research works are demonstrated to be a special case of the proposed idea. The effectiveness of the proposed method is validated by demonstrating the zero-ripple input current using a 31 V dc to 60 V dc, 240 W boost converter prototype and a 31 V dc to 115 V (rms) ac, 320 W current-fed-switched inverter prototype, and the zero-ripple output current using a 62 V to 42 V dc, 450 W buck converter prototype.

In this article, a novel high-power-factor electrolytic-capacitorless light-emitting diode (LED) driver based on the use of a ripple port is presented. The ripple port consists of adding an extra power processing circuit at the output of the converter that injects energy to compensate for the output current and voltage ripples. In this work, the main converter is built by using a flyback converter operating in the discontinuous conduction mode (DCM). The ripple port is implemented by adding an extra winding to the flyback coupled inductors, together with an extra switch, a capacitor, and an inductor. The additional switch is used to inject energy to the output in the time intervals, in which the flyback output current is low, thus reducing the output current ripple. The proposed converter is analyzed in detail, and a design methodology is proposed. A design example for a 27-V/1-A LED lamp is presented. Simulation and laboratory experiments have also been carried out. It is demonstrated that the proposed solution can achieve a reduction on the output current ripple of around 65% compared to the solution without ripple port for the same total capacitance and maintain a high power factor of 0.994.

This paper discusses experimental validation of semi-bridgeless boost rectifier (SBBR) operation of continuous conduction mode (CCM) & discontinuous conduction mode (DCM) for power quality improvement in uninterrupted power supply (UPS) system. The double stage conversion in UPS attenuates power quality at the input side and output configuration of the system. Many researchers have proposed the improvement of power quality with CCM and DCM operations for ac-dc conversion stage in bridge and bridgeless rectifier, but there is lack of knowledge about their performance and drawbacks of CCM and DCM operation with SBBR topology. This paper focuses on experimental analysis of SBBR topology operating in CCM and DCM under different load ranges. The performance of power quality factors and efficiency of SBBR operating in CCM and DCM are addressed. To study the stability analysis of SBBR operation in CCM and DCM, a comprehensive small signal model is derived by analyzing the inductor current waveforms. PSCAD simulations have obtained theoretical study of SBBR with CCM and DCM operations and experimental validation is carried out through FPGA Spartan 3A processor.

The boost converter operates either in discontinuous conduction mode (DCM) or in continuous conduction mode (CCM). The operation mode is determined by the duty ratio, load and parameters of the boost converter. The plant model in DCM and CCM are different in the frequency domain response. Therefore, it will be difficult to design a controller with stable operation and fast transient response for both modes. Moreover, the boost converter will be unstable between DCM and CCM. In this paper, the proposed control strategy can transit between DCM and CCM seamlessly by adding a mode detector, the boost converter can be automatically operated by selecting of control loop in both operation modes. The proposed controller still has a voltage control loop in DCM and current/voltage control loops in CCM. Each controller is designed by considering the stability and response time. The proposed mode detector will be explained with a frequency domain analysis. Due to the wide range operation capability of the proposed control strategy, the proposed control strategy is suitable in the fuel cell portable applications. In addition, smooth operation of the converter will also be beneficial to the fuel cell stack reliability. A 20 W boost converter prototype is used to verify the performance of the proposed control scheme.

Continuous and discrete-time averaged models are available for pulse width modulated (PWM) converters operating in the continuous conduction mode (CCM). A new discrete-time model for PWM converters operating in the discontinuous conduction mode (DCM) is proposed that leads to the exact discrete-time mathematical representation of the averaged values of the output signal.This model can also provide the averaged values of other internal signals with little increase in simulation time. This model is also used to simulate PWM converters operating in both DCM and CCM when combined with the averaged CCM model in [1]. It is compared to other models with respect to accuracy and simulation speed through a numerical example of boost converter. This method gives the exact values of the one-cycle-average (OCA) values of signals at switching instants. Numerical simulations show the accuracy and speed of the proposed method as well as its advantage in simulating PWM converters operating in both CCM and DCM.

This paper presents renewable energy system which consists of low voltage sources like fuel cells and photovoltaic (PV) cells. Thus the high step-up dc-dc converters are used to produce high step-up gain. Theoretically the boost converter can provide the high voltage gain at large duty cycle. But in practice the voltage gain is reduced, due to losses in utilized components like rectifier diode, power switch, inductor and capacitor. Hence the converter using coupled inductor technique was introduced. However, the leakage inductor cause voltage transients on main switch and also reduce the conversion efficiency. To mitigate the voltage stress on the main switch due to voltage spike/transients, the coupled inductor with active clamp circuit based converters are introduced. In this work, a high step-up dc-dc converter with lossless passive clamp circuit is proposed to reduce stress on the main switch and also to recycle the energy of the leakage inductor. The proposed topology consists of two diodes and two capacitors on the secondary side of the coupled inductor to achieve the high voltage gain. The proposed topology will be analysed in PSIM model in both continuous conduction mode (CCM) and discontinuous conduction mode (DCM) of operation and the boundary condition between CCM and DCM will be presented.

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.

This paper presents a control method for three-phase inverter under grid fault condition based on a novel critical conduction mode (CRM)-based soft-switching modulation. In the soft-switching modulation, one phase is clamped to dc bus, other two phases operate in CRM and discontinuous conduction mode (DCM), respectively. The soft-switching technique with silicon carbide (SiC) power devices allows the inverter to operate at hundreds of kHz with high efficiency by reducing switching loss. In order to extend the modulation scheme to more practical cases, behavior of the inverter under grid fault conditions, specifically voltage sag, is investigated. During voltage sag, the grid voltage becomes unbalanced requiring unbalanced ac current reference for the avoidance of output active power oscillation. With the unbalanced grid voltage and ac current reference, continuous conduction mode (CCM) operation occurs where DCM operation is intended leading to high turn-on loss. To eliminate the CCM operation and reduce the turn-on loss, an improved modulation technique is proposed by using off-time extension concept in CRM phase. In this paper, how the CCM operation appears under grid fault condition, and details of the proposed control are discussed. Performance of the proposed control method is validated experimentally with SiC-based three -phase inverter laboratory prototype.

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 efficiency comparison of quadratic boost converter in continuous conduction mode (CCM) and discontinuous conduction mode (DCM). Analytical expression for the DC component and RMS component of currents in CCM and DCM is derived. Total losses incurred in quadratic boost converter are calculated. Discontinuous conduction modes in three cases are discussed. The simulation result in software MATLAB/SIMULINK is presented for validating the results obtained by mathematical theories.