Analysis of continuous conduction mode for boost DC-DC converter

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.

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 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.

A new discrete time state feedback controller is presented, which allows high bandwidth voltage control of a buck converter for any load condition whether it operates in discontinuous conduction mode (DCM), continuous conduction mode (CCM) or in the boundary of these regions. This makes the buck converter applicable for a wide range of applications. For the control design process two large signal models are developed, which represent the buck converter's discrete time dynamics in CCM and DCM. A simple PI regulator is used for the voltage control of the converter. The operation mode is detected and the voltage controller is connected in cascade to a current controller in CCM or to a nonlinear state feedback decoupling structure in DCM. In this work, the modeling and design of the proposed control topology are introduced and its performance is demonstrated in simulation and experiment.

This paper investigates the energy transfer modes of the quasi-Z-source (qZS) DC-DC converter, and accordingly, presents the critical inductor design considerations. The energy transfer modes of the qZS DC-DC converter are generally classified into the continuous conduction mode (CCM) and discontinuous conduction mode (DCM) when considering whether the inductor current reaches zero. In addition, the CCM can be further divided into a complete inductor supply mode (CISM) and an incomplete inductor supply mode (IISM) when comparing the minimum inductor current and the maximum load current. The critical inductance under the CISM, IISM, and DCM for the qZS DC-DC converter is derived in this paper within a specific range of the loading and input voltages in this paper. The capacitor voltage ripple in the impedance network and the output voltage ripple in these energy transfer modes are also obtained. Both simulations and experimental tests are presented to validate the theoretical analysis.

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.

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.

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 article presents a maximum efficiency tracking method for an inductive power-transfer (IPT) system based on a Boost dc-dc converter. Impedance matching (IM) is achieved by maintaining the equivalent load impedance to be constant against load variations. The expression of the optimal equivalent load impedance corresponding to the maximum system-transfer efficiency is derived, and the impedance-transfer characteristics of the Boost converter in both continuous conduction mode (CCM) and discontinuous conduction mode (DCM) are analyzed. The duty cycle of the Boost converter is controlled to maintain the optimal equivalent load with extended range in DCM mode, and the switching frequency of the Boost converter is further adjusted to improve the accuracy of the IM. Both simulation and experimental results have demonstrated that the proposed IM method can help achieve the maximum power-transfer efficiency under a wide range of load variations.

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.

Existing aggregation methods for large-scale data center power systems often overlook disparities in power supply units, leading to reduced accuracy in the small signal dynamics of aggregated model. To fill this gap, this article develops an impedance-based aggregation method for paralleled power factor correction (PFC) converters with heterogeneities in power levels, conduction modes, and line impedances. The closed-loop input admittances of PFC converters operating in continuous conduction mode (CCM) and discontinuous conduction mode (DCM) are presented first. The parametric scaling is then derived to aggregate multiple PFC converters at different power levels and operation modes, including the CCM, DCM, and mixed conduction mode, at the rack level. Furthermore, the aggregation rule and criteria for paralleled PFC converters with unequal line impedances is developed to provide a reduced-order dynamic model for adjacent server racks. The proposed parameter scaling and aggregation method allow efficient interaction analysis and stability assessment for data center power systems. The accuracy and robustness of the impedance-based aggregation are finally validated by simulations and experimental tests.

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.

An isolated power converter topology is presented which uses an integrated passive power-sharing network for equal brightness levels in parallel LED branches. Analyses of discontinuous conduction mode (DCM) and continuous conduction mode (CCM) of converter operation have been performed. The DCM operation shows an improved performance and allows a reduced size of the required transformers compared to the CCM. Analyses of the power sharing quality with non ideal transformers have been performed, additionally. A prototype has been built and tested. Experimental results are in good correlation with theoretical predictions.

Due to the simple structure and low cost, the primary-side-regulation (PSR) flyback converter is widely used in small power applications. As the output voltage is sampled from auxiliary winding in PSR flyback converter, some sampling error exists, especially when continuous conduction mode (CCM) is introduced for higher power. To improve the constant voltage accuracy, a novel digital controlled sampling strategy is proposed. This scheme uses a digital ramp sampling method to sample output voltage in both discontinuous conduction mode (DCM) and CCM, and proposes a voltage adjustment strategy to adjust sampling errors in CCM without weakening the stability in the load-switch process. Finally, the experimental results validate the presented scheme and show that the output voltage error is less than 0.6% in a 20-V, 5-A PSR flyback prototype.

A simple scheme is proposed for offline unity power factor rectification for high-frequency AC buses (20 kHz). A bandpass filter of the series-resonant type, centered at the line frequency, is inserted between the line and the full-wave rectified load. The Q=Z/sub 0//R/sub L/ formed by the load and the characteristic impedance of the tank circuit determines the power factor, the boundary between continuous and discontinuous conduction modes, the peak stresses, and the transient response of the rectifier. It is shown that for Q>2/ pi the rectifier operates in continuous conduction mode and the output voltage is independent of the load. Also, it is shown that for Q>2 the line current is nearly sinusoidal with less than 5% third-harmonic distortion and the power factor is essentially unity. An increase in Q causes an increase in the peak voltages of the tank circuit and a slower transient response of the rectifier circuit. The DC, small-signal, and transient analyses of the rectifier circuit are carried out, and the results are in good agreement with simulation and experimental results. >