Discontinuous Conduction Mode Research Articles

A fast-response RBCOT buck converter with second-order differential and integrator compensation based on FVF

A second-order differential and integration circuit based on a flipped voltage follower (SDI-FVF) is proposed in the paper, providing compensation ripple for the buck convert with ripple-based constant on-time (RBCOT). Additionally, an adaptive conduction time module is designed which stabilizes the operating frequency of the converter in continuous conduction mode (CCM) and guarantees stable conduction time in discontinuous conduction mode (DCM). The proposed RBCOT buck convert has been designed using 180 nm process. It operates with an input voltage range of 2.5 V–5 V and an output voltage range of 0.8 V–5 V, accommodating a load current range of 0 A to 3A. It operates at a frequency of 4 MHz, exhibiting an output ripple of 1.4 mV, achieving a peak efficiency of 91.5 %. The efficiency exceeds 85 % under a load current of 1 mA. The undershoot and overshoot voltage are only 0.13 mV and 7.1 mV with a load current variation rate of 3 A/μs.

Modeling and control of a single-phase grid-tied medium-frequency isolated converter for active and reactive power management in photovoltaic applications

A single-phase photovoltaic converter formed by the full-bridge dc–dc converter with a capacitive output filter and a grid-tied full-bridge inverter is studied in this paper. The switched model, the average model based on a modified-conventional approach, and the linear state-space model of the dc stage operating in discontinuous conduction mode are presented and compared with the behavior of the state variables obtained from a simulator. A duty-ratio constraint is obtained from the modified average model, which is eliminated by expressing its dependency on the control and the state variables. In addition, the modeling of the ac stage is carried out in the dq reference frame. Linear controllers are designed to guarantee the maximum power point tracking, the regulation of the dc-link voltage, the injection of the active power generated, and the reactive power management as an ancillary function. The controllers proposed, according to the transfer functions derived from the linear models, are validated via simulation for a 1.41 kVA converter.

Lyapunov stability analysis and FIL implementation for boundary‐based hybrid controller in boost converter

AbstractThis paper presents a comprehensive stability analysis of the boundary‐based hybrid control (BBHC) algorithm designed for boost converter. The stability assessment is carried out utilizing multiple Lyapunov functions, addressing both continuous conduction mode (CCM) and discontinuous conduction mode (DCM) operation. The boost converter is modeled as a hybrid automaton to capture its dynamic behavior accurately. Through rigorous Lyapunov stability analysis, this study demonstrates the effectiveness of the BBHC algorithm in ensuring stable operation of the boost converter across various operating modes. Additionally, the proposed control algorithm's validation is conducted using the FPGA‐in‐the‐loop (FIL) technique, highlighting its efficiency and robustness in real‐world applications. This research contributes valuable insights into the design and implementation of stable control strategies for boost converter, emphasizing the practical utility of the BBHC algorithm with FIL for enhanced performance and reliability in power electronics systems.

Unified Small-Signal Model for DC–DC Converters Based on the Four-State Switching Cell in Discontinuous Conduction Mode

Unified Small-Signal Model for DC–DC Converters Based on the Four-State Switching Cell in Discontinuous Conduction Mode

LLC resonant converter analysis in PO mode

The PO mode under time-domain analysis is a kind of discontinuous conduction mode (DCM) which is beneficial to reduce the switching loss of the converter, but the calculation of the gain and frequency characteristics of the converter in this mode is cumbersome and difficult to be solved. Based on the analysis method of time domain approximation, the PO operating mode characteristics of the LLC resonant converter are analyzed, and a simple and accurate voltage gain calculation formula is theoretically deduced. Simple analytical expressions for the PO mode power boundary conditions are given based on the voltage variations of the magnetizing inductance and capacitance. A simulation model of the studied converter is established, and the simulation can prove that the proposed voltage gain formula and PO mode boundary conditions are correct.

Modeling and Experimental Validation of Broad Input-Output Range Three-Voltage-Level Rectifier

A new type of single–conversion–step wide–input–range versatile step–up/down three–voltage–level power–factor correction stage is presented in this manuscript. The rectifier can operate both in continuous–conduction mode and discontinuous–conduction mode. First, the rectifier’s principle of operation is described, and then the innovative rectifier is analyzed in continuous and discontinuous–conduction modes. After, an average model for the innovative rectifier is developed. Lastly, the proposed theory is experimentally validated using a multiplier–less dual–control–loop mode at discontinuous–conduction modes. It is shown that although no multiplier is used in the control circuitry, the power factor is near unity. It is revealed that the rectifier can swing the output voltage from 50 V to 900 V while the input voltage is 230 Vrms. Although the rectifier output has a split DC bus with three voltage levels, the required control effort is low, and the output voltage is balanced. The innovative topology suits any standard power–factor correction rectifier application, dual–stage low–voltage power supply, and three–level voltage supplement for low–harmonic inverters. Since the rectifier’s output–voltage swing is extremely wide, energy storage systems and electric vehicle batteries are suitable applications.

Power Loss and Temperature Distribution in Coil of PFC Inductor with Air Gap for Multimode Operation

Power converters inherently display non-linear load characteristics, resulting in a high level of mains harmonics, and hence the necessity of implementing Power Factor Correction (PFC). Active PFC circuitry typically comprises an inductor and a power switch to control and alter the input current so that it matches, in shape and phase, the input voltage. This modelling of the waveforms can be performed by means of distinct conduction modes of the PFC inductor. The digital controller implemented in the constructed and investigated boost-type PFC converter can be programmed to operate in discontinuous conduction mode (DCM), continuous conduction mode (CCM), or a combination of the two. The individual modes of operation, via distinct PFC inductor current waveforms, impact the overall efficiency of power conversion and, by extension, temperature distribution in the magnetic component. This paper investigates how the examined conduction modes bear on distinct power-loss mechanisms present in the PFC inductor, including high-frequency eddy-current-generating phenomena, and the fringing effect in particular. As demonstrated herein, the DCM operation, for the set output power level, exhibits exacerbated power dissipation in the winding of the inductor due to the somewhat increased RSM value of the current and the intensified fringing magnetic flux at an air gap. The latter assertion will undergo further, more quantitatively focused research. Finally, the construction of the coil was optimised to reduce power loss by diminishing eddy-current mechanisms.

A hybrid step-up converter for PV integration with wide input variation acceptability: comprehensive performance and reliability assessment

Abstract A high-step-up DC–DC converter (DDC) is commonly used in micro-grids, renewable energy source (RES) integration, uninterruptible power supplies, hybrid vehicles, and other applications to deal with intermittency in power sources. Solar photovoltaic (SPV) is a prominent RES due to its many benefits, but its output voltage must be enhanced for high-voltage (HV) applications; hence, various topologies are suggested for desirable gain in the literature. Nevertheless, contemporary topologies exhibit restricted gain, higher device stress, analysis on restricted performance metrics, constrained handling capacity for input variations, relatively lower reliability, and suboptimal device utilization. This work investigates a new Z-source with switched-capacitor (HZSSC)-based hybrid step-up converter to solve the aforementioned restrictions and adapt PV voltage dynamics. Additionally, this paper presents MIL-HDBK-217F-based methodology for evaluating converter-level reliability, assessing the implications of device parametric variation on overall reliability, conducting a detailed analysis of figure of merits, performing thermal modeling, and executing small-signal-modeling to demonstrate operational efficacy. In-depth mathematical analysis of both continuous conduction mode (CCM) and discontinuous conduction mode (DCM) are conducted. The detailed comparison analysis shows that the suggested converter outperforms traditional converters in voltage-gain, voltage-stress, device-utilization, and reliability. Additionally, a 400 W, 220 V laboratory-scaled prototype shows 68 % reliability after 20 years. The hardware test outcomes validate the accuracy of both the mathematical investigation and simulation findings.

Analysis of Power Transmission Characteristics of a Novel Secondary Side LCD Series Forward Converter

A novel secondary-side LCD series forward converter is proposed, and the power transmission characteristics of the excitation inductance of the proposed converter under different modes are analyzed. By analyzing the relationship between the transmission power of forward branch and additional branch and excitation inductance, it is concluded that when the excitation inductance Lm works in CCM (continuous conduction mode), the transmission power of forward branch and additional branch has nothing to do with the value of excitation inductance. When the excitation inductance Lm works in DCM (discontinuous conduction mode), the transmission power of forward branch increases with the increase of excitation inductance, while the transmission power of additional branch decreases with the increase of excitation inductance. At the same time, the influence of power distribution on the efficiency of transformation topology is explored, and the relationship between the transmission power of the forward branch and the current stress of the switching tube was derived, and the parameter design method of magnetic element is put forward. Finally, the circuit model of the novel secondary side LCD series Forward converter is established, and the experimental results verify the correctness of the theoretical analysis and the feasibility of the parameter design method.

A DCM-Based Non-Isolated Step-Down DC Transformer

DC transformers have emerged as essential devices for medium voltage DC (MVDC)-low voltage DC (LVDC) distribution systems. However, conventional step-down single-level converters have limits on the voltage level of the MVDC-LVDC distribution system. This paper proposes a non-isolated step-down (NISD) DC transformer based on discontinuous conduction mode (DCM). The proposed structure can withstand high voltage levels by sharing voltages between energy storage modules dividing voltage levels. The proposed NISD DC transformer determines operational modes based on energy storage modules and performs the voltage conversion process. The effectiveness of the proposed NISD DC transformer is verified based on a case study using a power system computer-aided design and electromagnetic transient simulation engine including DC (PSCAD/EMTDC™).

A new transformerless buck‐boost converter with improved voltage gain and continuous input current

AbstractThis paper proposes a new transformerless buck‐boost converter with an extended voltage conversion ratio. This converter has semi‐quadratic voltage gain, which provides more gain with lower duty cycles. This converter has a simple structure and easy implementation, which reduces the cost and increases efficiency. The proposed converter operates in continuous conduction mode and provides two operation modes by turning on and off the switches. The suggested converter has continuous input current and low input current ripple, which is important when utilizing renewable energy sources. The calculation of the proposed converter includes ideal and practical voltage gain, current calculations, voltage stresses of the switches and diodes, current stress of the switches, parameter design, efficiency, and a brief analysis of discontinuous conduction mode and boundary conditions. The proposed converter provides efficiency of about 93.1% in boost mode and 92.14% in buck mode at 50 W output power. The suggested converter varies the input voltage from 20 to 48 V in boost mode and changes the input voltage from 20 to 10.4 V in buck mode. Finally, a laboratory prototype has been built to prove and evaluate the simulation results and theoretical analysis of the proposed converter.

Differences between Riemann–Liouville and Caputo calculus definitions in analyzing fractional boost converter with discontinuous‐conduction‐mode operation

SummaryFractional‐order calculus is an extension of the integer‐order calculus in that its order is not limited to integers but can be noninteger as well, thus making the application of fractional‐order calculus more flexible. It has been shown that actual reactive elements such as capacitors and inductors have fractional‐order properties and that the theory of fractional‐order calculus can be utilized to more accurately characterize circuits and systems containing reactive elements. However, there is no uniform definition of fractional order calculus. Different definitions will yield different results in solving the same fractional‐order circuits and systems, and it is worth exploring whether these differences have an impact on the accuracy of solving fractional‐order systems. Taking a fractional‐order boost converter running in discontinuous conduction mode (DCM) as an example, this paper focuses on the differences between the Riemann–Liouville (R–L) and the Caputo fractional calculus definitions. Effects of the two definitions on the division of the converter's CCM (continuous conduction mode) and DCM operating regions are analyzed, as well as their impact on the characterization of a fractional‐order boost converter in DCM operation, including the DC (direct current) operating point, current ripple, and voltage gain. Simulations and experiments show that the analytical results based on the R–L definition can more accurately describe the operation of a real fractional‐order converter than those based on the Caputo definition.

Coupled Inductor-Based Current-Fed Ultra-High Step-Up DC-DC Converter Featuring Low Input Current Ripple

A DC-DC converter with ultra-high voltage gain is presented in this article. The current-fed structure of the proposed converter provides outstanding performance for sensitive source applications due to its continuous input current with minimal ripple. Using two double-winding coupled inductors in the suggested structure provides more degree of freedom arising from the turn ratios. Simultaneous operation of the two switches causes a simple operation and a simple control system in addition to the need for a single switch gate pulse. Operation of the converter in continuous and discontinuous conduction modes is analyzed as well as design considerations of the active and passive components. The converter is compared with some recent introduced converters, and a 200 W laboratory prototype of the converter is implemented, and experimental results confirming the converter performance are given.

A High-Efficiency DC-DC Converter Based on Series/Parallel Switched Inductor Capacitors for Ultra-High Voltage Gains

A high-efficiency DC-DC converter employing a modified architecture called the hybrid switched inductor–capacitor series (MHSLCS) is proposed in this paper. The primary goal is to achieve a notably ultra-high voltage gain for renewable energy systems (RESs). Furthermore, the use of only one input capacitor in the MHSLCS eliminates pulsations in the input current at both low and high duty ratios. The proposed converter integrates the MHSLCS with a modified switched capacitor (MSC) that interleaves with the main MOSFET, effectively doubling the voltage transfer gain. Additionally, a modified hybrid switched inductor–capacitor parallel (MHSLCP) is incorporated in parallel with an interleaved auxiliary MOSFET. Both MOSFETs, combined with the MSC, contribute to achieving an ultra-high voltage gain. In addition, the inductors of the MHSLCP operate in a discontinuous conduction mode (DCM), which results in significant stress reductions in the power diodes and switches at high output voltages. The advantages of the proposed converter are multifaceted, demonstrating a high efficiency while minimizing the voltage in power device diodes and MOSFETs. The use of low inductance and capacitance values at high switching frequencies further enhances the performance. Wide-bandgap (WBG) power devices are employed to achieve the desired high voltage gain and efficiency. The proposed converter was designed with a PCB and underwent experimental testing to validate laboratory results. The proposed converter boosted the input voltage from 30 V to a variable output voltage between 325 V and 500 V, with a power output of 325 watts and an efficiency of 95.5%.

Performance analysis of a bridgeless power factor correction (PFC) buck–boost LED driver with ripple diversion scheme for extended lifespan

SummaryIn the state of the art of AC‐fed light‐emitting diode (LED) drivers, power factor correction (PFC), second harmonic LED current ripple elimination, low current total harmonic distortion (iTHD), removal of electrolytic capacitors (EC) and flicker‐free operation are the major challenging issues. This paper proposes a bridgeless universal voltagerange AC‐fed LED driver that overcome the major issues of LED driver. The bridgeless buck–boost PFC configuration minimizes the losses relative to the front‐end bridge rectifier‐based configurations. Operating in discontinuous conduction mode (DCM), the source current tracks the input voltage shape for a wide operating range, achieves inherent PFC and maintains low input current THD. Also, this provides significant reduction in the output current ripple with the ripple diversion circuit (RDC) connected in shunt across the LED load, which relatively reduces and utilizes low value of output capacitance. Hence, a flicker‐free operation is achieved without the use of electrolytic capacitors. In addition, the elimination of ECs improves the operating lifespan of the proposed LED driver. A detailed theoretical analysis and results of the proposed LED driver are validated on DSP and analog controller platforms with a 62 W/62 V experimental laboratory prototype. The experimental results confirm that the proposed LED driver achieves a power factor of 0.94–0.997, input current THD of maximum 6.8%, output current ripple of 5%, and a peak efficiency of 91.25% for the wide range of input voltage variation. These indices also satisfy IEC‐61000‐3‐2 and IEEE 1789‐2015 standard limits.

Frequency Modulation Scheme for CCM Boost PFC Converter to Improve THD in Light-Load Condition

This study proposes a novel frequency modulation scheme for a continuous conduction mode (CCM) boost power factor correction (PFC) converter. The aim is to improve the total harmonic distortion (THD) under light-load conditions. Boost converters are widely utilized with CCM control for the PFC stage owing to their ability to achieve high efficiency with minimal components. In addition, they have a high power factor (PF) and low THD. However, despite being designed for CCM operation, the boost PFC converter transitions into discontinuous conduction mode (DCM) as the output load decreases. This mode, known as mixed conduction mode, degrades the PF and THD of the PFC converter. To address these issues, we propose a novel frequency modulation scheme. The CCM boost PFC converter adopts frequency variation to reduce the DCM region. To validate the feasibility of the proposed concept, a prototype with a 60 Hz/230 Vac input and 850 W/380 V output was utilized. Consequently, the boost PFC converter attains a high PF and low THD with simplified circuits.

Large-signal input characteristics of selected DC–DC switching converters, Part II. Discontinuous conduction mode

Large-signal input characteristics of selected DC–DC switching converters, Part II. Discontinuous conduction mode

Dependence of Continuous-Discontinuous Conduction Mode Boundary on Gate Pulse Shift in Coupled Inductor Single-Input Dual-Output Boost Converter

The coupled inductor single-input dual output (SIDO) converters can supply two different output voltages from one input voltage with reduced component counts, reduced losses, and increased efficiency. Inversely coupled inductors enhance the advantages by reducing the core and overall converter sizes. The CI-SIDO boost converters operate in three modes– continuous conduction mode (CCM), discontinuous conduction mode (DCM) and CCM/DCM boundary. Due to simple load-independent control, the CCM is preferred more for operating CI-SIDO converters. This paper introduces the method of lowering the CCM/DCM boundary, thus, widening the CCM range of the converter by shifting the gate pulse. The commonly used method of reducing the CCM/DCM boundary current is increasing the inductance values, which is not preferred due to the increased size of the core and the converter. The paper presents the shift of gate pulses to reduce the boundary current of the CI-SIDO boost without changing inductance or any other circuit element. The gate pulse shift where maximum reduction takes place is found analytically. The proposed method is experimentally verified for all possible voltages and coupled inductor parameters. The presented experiments observed the percentage reduction in CCM/DCM boundary current is up to 91.67%.

Single-Phase Voltage-Doubler High-Power-Factor Ćuk Rectifier Operating in Discontinuous Conduction Mode

Single-Phase Voltage-Doubler High-Power-Factor Ćuk Rectifier Operating in Discontinuous Conduction Mode

Fully Soft-Switched Buck–Boost Bridgeless PFC Converters With Single-Magnetic Core

This paper proposes new fully soft switched bridgeless buck-boost power factor correction converters using single magnetic core with capability of realizing positive or negative output voltages. Full ZVS operation is provided for the main switches independent of the load and grid voltage variations. Also, the proposed converters have common ground and single ended output which increase power density and alleviates common mode noise. The proposed converters operate under discontinuous conduction mode (DCM) to shape the input current inherently. A 120W, 100kHz laboratory prototype with negative output voltage is implemented to verify the theoretical analysis and the effectiveness of the proposed topologies. The results demonstrate efficiency of 96.2% and total harmonic distortion (THD) of 4% at full load condition.