Search Results (74)

This paper introduces a novel, high-accuracy method for determining the output voltage ripple in DC–DC converters. For the buck converter, the proposed approach enables accurate ripple estimation even under discontinuous conduction mode (DCM) operation. In the case of boost and buck–boost converters, this method not only facilitates ripple calculation in DCM but also enhances accuracy in continuous conduction mode (CCM), particularly near the transition boundary between CCM and DCM. The validity of the proposed method has been confirmed through both simulations and experimental measurements, with excellent agreement observed among theoretical, simulated, and experimental results. Full article

A Buck converter in the DC microgrid is often used to transform high DC voltage to meet the requirements of low voltage loads, where electrolytic capacitors are commonly regarded as the most vulnerable components. A lot of studies have shown that equivalent series resistance (ESR) is the best health indicator for electrolytic capacitors, which means that it is significant to monitor the variation in ESR values for health evaluation. This paper presents a non-intrusive online ESR estimation method of the output capacitor for a Buck converter based on inductor current ripple fitting. In this method, only output voltage is sampled and inductor/capacitor current ripple is fitted by use of the characteristics of output voltage ripple. ESR calculation is implemented based on the orthogonality of the voltage ripple and the fitted current ripple, which has high-precision and anti-noise characteristics. Compared to existing methods, the proposed scheme does not require additional current sensors or high-precision trigger sampling devices, making it a cost-effective solution. Based on the proposed scheme, accurate ESR estimation is achieved for both continuous conduction mode (CCM) and discontinuous conduction mode (DCM). An experimental ESR monitoring system platform is built and experimental estimation results are provided to verify the effectiveness and the precision. Full article

The isolated boost full-bridge converter (IBFBC) is a DC–DC conversion topology that achieves a high boost ratio and provides electrical isolation, making it suitable for applications requiring both. Its operational dynamics are often intricate due to its inherent characteristics and the prevalent usage of nonlinear switching elements, leading to bifurcation and chaos. Chaos theory was employed to investigate the impact of changes in the voltage feedback coefficient K and input voltage E on the dynamic behavior of the IBFBC when operating in discontinuous conduction mode (DCM). Based on an analysis of its operating principles, a discrete iterative mapping model of the system in DCM is constructed using the stroboscopic mapping method. The effects of two control parameters, namely the proportional coefficient and input voltage, on system performance are studied using bifurcation diagrams, fold diagrams, Poincaré sections, and Lyapunov exponents. Simulation experiments are conducted using time-domain and waveform diagrams to validate the discrete mapping model and confirm the correctness of the theoretical analysis. The results indicate that when the IBFBC operates in DCM, its operating state is influenced by the voltage feedback coefficient $K$ and input voltage $E$. Under varying values of $K$ and $E$, the system may operate in a single-period stable state, multi-period bifurcation, or chaotic state, exhibiting typical nonlinear behavior. Full article

The Cuk power factor correction (PFC) converter with an input inductor operating discontinuous conduction mode (DCM) is widely utilized for its advantages of continuous input and output currents, low output voltage ripple, and simple control. However, the conventional Cuk PFC converter encounters issues such as the inability to achieve high power factor (PF) because of input current distortion and high intermediate capacitor voltage, especially at high input voltage. To achieve high PF, high efficiency, and low intermediate capacitor voltage simultaneously, by operating the output inductor at critical conduction mode (CRM) and adjusting input inductance from 170 µH to 930 µH within the half-line cycle dynamically with the transient rectified input voltage, a DCM-CRM Cuk PFC converter utilizing variable inductor control is proposed in this paper. The topology operational principle, control strategy, and key characteristics of the proposed converter have been studied. A 108 W experimental prototype was built and tested to validate the proposed converter. According to the comparative experimental results between the conventional converter and the proposed converter, it can be concluded that the proposed converter utilizing variable inductor control can enhance the PF and efficiency and reduce the intermediate capacitor voltage and total harmonic distortion (THD) of input current with universal 90~240 Vac input voltage range. Full article

This paper proposes a steady-state analysis of the asymmetrical pulse-width-modulated series resonant converter, commonly employed under light load conditions for effective voltage regulation. The proposed method achieves precise and explicit converter waveforms by applying the Laplace-based theorem to the converter’s ordinary differential equation with periodic and discontinuous inputs, without relying on approximations. By numerically determining the intermediate variables that define converter waveforms, the analysis provides accurate steady-state results based on system parameters. Furthermore, it derives an analytical solution to identify the load conditions suitable for asymmetrical pulse-width modulation operation, as well as the boundary load conditions for discontinuous conduction mode within this mode. The mathematical expressions derived for the converter waveforms and operational modes are validated through simulations using a switching model in PSIM software, as well as through experimental results. Full article

This paper proposes a control method to improve the dynamic performance of a two-phase DM (Differential Mode)-coupled boost converter designed for applications such as hybrid vehicles and railway systems. A conventional boost converter can be modified to a two-phase interleaved configuration to reduce current ripple and incorporate a differential mode (DM)-coupled inductor to reduce the volume of magnetic components, thereby achieving a decrease in cost and volume. However, when this converter is operated using a conventional PI controller, significant issues arise, particularly in the discontinuous conduction mode (DCM), where dynamic characteristics and response times are considerably slow. For a conventional boost converter, the steady-state duty cycle during DCM operation can be calculated analytically and used for feedforward compensation in a current-duty controller. In contrast, the duty cycle of a two-phase DM-coupled boost converter during DCM operation exhibits non-linear behavior depending on input/output voltages and load conditions, making analytical computation infeasible. To address this, steady-state duty cycle data is extracted through experiments and simulations, and a Look-Up Table is constructed to perform feedforward compensation. Given the multiple input and output specifications, multiple Look-Up Tables are required, leading to excessive MCU (Micro Controller Unit) computation load. The proposed correction algorithm enables feedforward compensation in the DCM region with a single Look-Up Table for all input and output specifications, achieving improvements in dynamic characteristics and reducing MCU computational load. This method achieves a reduction in settling time by up to 77 ms, with a minimum improvement of 10 ms, thereby significantly enhancing the responsiveness of the converter. Full article

Z-source/quasi-z-source inverters can make up for some limitations of traditional voltage-/current-source inverters. In recent years, more and more research has been carried on z-source/quasi-z-source inverters, but most of them are unable to realize input/output galvanic isolation. The proposal of high-frequency isolated z-source/quasi-z-source inverters greatly enriches the topological family of this type of converter but places relatively high voltage stress on the capacitors. In this paper, a novel circuit topology of a quasi-z-source inverter with a high-frequency AC link of a new high-proportion power system is proposed. The operating principle and abnormal operating states, such as discontinuous-conduction mode (DCM) operation and abnormal states caused by component failures, are analyzed. The double closed-loop control strategy is analyzed and designed, and a grid-connected photovoltaic system based on the inverter is designed. The experimental results verify that the presented inverter has advantages such as high-frequency electrical isolation, bi-directional power flow, lower voltage stress on the capacitors, etc. Full article

Recently, a new type of lighting source, deep ultraviolet light-emitting diode (LED), has appeared in the markets of space purification and surface sterilization. In this paper, a new type of electronic lighting driver for supplying a deep-ultraviolet LED sterilization lamp is proposed and developed. The main circuit combines a buck converter and a flyback converter into a single-stage single-switch buck-flyback AC-DC power converter with power factor correction. In addition, the proposed electronic lighting driver leverages a wide bandgap SiC Schottky diode as the output diode to lower the power diode losses and recycles the energy stored in the leakage inductance of the transformer in order to improve the circuit efficiency. The magnetizing inductor inside the presented AC-DC power converter is designed to operate in discontinuous conduction mode (DCM), which naturally enables power factor correction (PFC). A single-stage prototype driver with a power rating of 3.6 W (90 V/40 mA) was developed and implemented for providing a deep ultraviolet LED disinfection and sterilization lamp. Experimental results show that the measured power factor (PF) is greater than 0.9 and the measured total harmonic distortion (THD) of the input current is less than 18% at an input utility voltage of 110 V. Furthermore, the measured output voltage ripple factor is less than 1% and the output current ripple factor is less than 4%. In addition, the proposed single-stage electronic lighting driver for supplying a deep ultraviolet LED disinfection and sterilization lamp achieves high circuit efficiency (greater than 90%), low circuit component count, and low circuit cost. Full article

A novel ac/dc LED driver with power factor correction and soft-switching functions is proposed. The circuit topology mainly consists of two modified single-ended primary inductance converters (SEPIC) with interleaved operation. The first half stage of SEPIC operates like a boost converter and the second half stage operates like a buck–boost converter. Each boost converter is designed to operate in discontinuous current mode (DCM) to function as a power factor corrector (PFC). The two buck–boost converters that share a commonly coupled inductor are designed to operate at near boundary conduction mode (BCM). Without using any active clamping circuit, auxiliary switch or snubber circuit, the active switches can achieve zero-voltage switching on, and all diodes achieve zero-current switching off. First, operation modes in steady state are analyzed, and the mathematical equations for design component parameters are derived. Finally, a prototype circuit of 180 W rated power was built and tested. Experimental results show satisfactory performance of the proposed circuit. Full article

In recent years, there has been a growing interest in using model-free deep reinforcement learning (DRL)-based controllers as an alternative approach to improve the dynamic behavior, efficiency, and other aspects of DC–DC power electronic converters, which are traditionally controlled based on small signal models. These conventional controllers often fail to self-adapt to various uncertainties and disturbances. This paper presents a design methodology using proximal policy optimization (PPO), a widely recognized and efficient DRL algorithm, to make near-optimal decisions for real buck converters operating in both continuous conduction mode (CCM) and discontinuous conduction mode (DCM) while handling resistive and inductive loads. Challenges associated with delays in real-time systems are identified. Key innovations include a chattering-reduction reward function, engineering of input features, and optimization of neural network architecture, which improve voltage regulation, ensure smoother operation, and optimize the computational cost of the neural network. The experimental and simulation results demonstrate the robustness and efficiency of the controller in real scenarios. The findings are believed to make significant contributions to the application of DRL controllers in real-time scenarios, providing guidelines and a starting point for designing controllers using the same method in this or other power electronic converter topologies. Full article

In this paper, a sample voltage dead-beat control based on differentiative voltage prediction (DVP) and switching-cycle extension (SCE) is presented to achieve optimal transient response for DC-DC converters under discontinuous conduction mode (DCM) operation. Firstly, to improve load transient response, a DVP method is proposed to estimate the load. With the estimated load, the controller realizes load current feedforward and thus improves the transient response with a wide load range. Secondly, an SCE strategy is proposed to enlarge the output current range and output voltage slew rate, both of which have limited value under conventional digital pulse width modulation (DPWM). When the output current reaches the limited value, the proposed strategy increases the switching cycle to enlarge the current range without losing DCM operation. Finally, combining DVP with SCE, the converter not only achieves optimal response in large signal transients, but also doubles the load range in DCM operation. Full article

This work introduces a generalized version of the pulse width modulation (PWM) switch model applied in the small-signal modeling of converters based on the multistate switching cell (MSSC) operating in discontinuous conduction mode (DCM). It consists of extending the concept formerly introduced by Vorperian for the representation of multiphase converters in DCM, yielding a circuit-based approach that does not rely on matrix manipulations unlike state-space averaging (SSA). The derived dc and ac models are valid for any number of switching states and any operating region defined in terms of the duty cycle, thus allowing for determining the voltage gain and distinct transfer functions. A thorough discussion of results is presented to demonstrate the applicability of the derived models to represent distinct configurations of the MSSC. Full article

In this paper, a single-stage step-down power factor corrector without a full-bridge rectifier is developed, which is designed to operate in discontinuous conduction mode (DCM). In terms of control, the DCM has the advantages of simple control and easy realization, no slope compensation, zero current switching, and no diode reverse current. By sampling the output voltage and using the voltage-follower control to generate the necessary control force to drive the power switch, not only can the output voltage be stabilized at the desired value, but also the input current can be, as much as possible, in the form of a sinusoidal waveform and can follow the phase of the input voltage. Moreover, the harmonic distortion meets the requirements of the IEC6100-3-2 Class D harmonics standard, and, thus, the proposed rectifier is appropriate for the computer, computer monitor, and television receiver. Eventually, by means of mathematical deductions, simulations by PSIM version 9.1, and experimental results, the feasibility and effectiveness of the proposed circuit can be verified. Full article

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™). Full article

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%. Full article