Converter In Continuous Conduction Mode Research Articles

High efficiency AOT-controlled boost converter with pseudo-constant switching frequency

An on-time generator for boost converters is proposed to achieve an adaptive on-time (AOT) control with pseudo-constant frequency in continuous conduction mode (CCM). Since the first-order parasitic effect of the components and devices is considered in the design of the on-time generator, the switching frequency (fsw) variation of the boost converter in CCM can be better suppressed with the load current (ILOAD), input voltage (VIN) and output voltage (VOUT) changes, which can effectively solve the EMI noise problem. In addition, the idea of capacitor pre-charging is applied to simplifying circuit complexity. Meanwhile, an on-demand modulation strategy is applied to improve the conversion efficiency. Simulation results show that the boost converter based on the proposed on-time generator can realize the fsw variation of 0.4 % in case of 200 mA ILOAD change. Moreover, the VIN may range from 0.8 to 1.5 V, the VOUT is set to 1.8 V, and the peak efficiency of the simulation is 96.9 %.

A new positive output DC–DC buck–boost converter based on modified boost and ZETA converters

A new DC–DC buck–boost converter with a wide conversion ratio is presented in this paper. The proposed buck–boost converter consists of a combination of modified boost converter and ZETA converter, which has the advantages of both converters such as continuous input/output current and positive polarity of the output voltage. The combination of these two converters achieves semi-quadratic voltage gain and makes the proposed converter suitable for industrial and renewable energy applications. With a voltage gain higher than that of the ZETA converter and modified boost converter, the proposed converter also reduces input current stress due to its continuity. Two operating states are available for this converter in continuous conduction mode. This converter has two switches that operate simultaneously and can be easily controlled. The converter's output voltage ripple and output capacitor current stress are reduced as a result of continuous output current. Computational analysis and the introduced structure efficiency considering the influence of parasitic elements are presented in this paper. The small signal modelling and closed-loop control, as well as simulation and experimental results are also presented. This converter has also been compared with other similar and recently presented topologies. Finally, a 40–60 W, 20–76 V for boost mode and 10 V for buck mode prototype was implemented to verify the accuracy of the computational analysis.

New single-switch buck–boost converter with continuous input/output currents and a wide conversion range

The main aim of this paper is to introduce a new high step-up/down buck-boost converter with a minimum number of switches which provides the benefit of having the continuity of the input/output current. This single-switch semi-quadratic converter is suitable for high step-up applications while being able to provide step-down voltage gains. Also, by applying some minor changes to the circuit elements, another single-switch buck-boost converter is suggested which has two operative outputs with different voltage gains. One of the outputs of this topology has quadratic buck-boost converter voltage gain which is appropriate for high step-up/step-down applications. The other output could vary from input voltage to minus infinity, ideally. After studying the steady-state operation of the proposed converters in Continuous Conduction Mode (C.C.M), the simulation results are presented. In addition, a comparison among related converters proposed in the literature is made. Finally, experimental results are evaluated by implementing a laboratory prototype of the proposed converter in both step-down and step-up modes. Theoretical, simulation, and experimental results are compatible with each other.

Robust digital voltage mode control of buck converter with enhanced tracking performance

The digital voltage controller of power converters is used because it has many advantages over its analog counterparts. Thus, in this paper, a controller of digital voltage mode is designed and analyzed for a non-isolated DC-DC buck converter in continuous conduction mode (CCM). First, an analog controller is designed using a Bode plot to achieve the desired stability margins in the frequency domain. Next, the analog controller is discretized using bilinear transformation with the pre-warping method. The characteristics of the discretized compensator can be maintained close to the corresponding analog compensator as long as a proper sampling time is selected. The digital control scheme is simulated with a nonlinear DC-DC buck converter model in MATLAB/Simulink to investigate the controller performance. The simulation results demonstrated the validation of the proposed digital voltage-mode control design approach. The developed digital controller eliminates DC error by tracking the reference voltage, achieving a fast transient response, maintaining specified stability margins, and effectively rejecting large disturbances.

Fractional-Order Modeling and Nonlinear Dynamic Analysis of Forward Converter

To accurately investigate the nonlinear dynamic characteristics of a forward converter, a fractional-order state-space averaged model of a forward converter in continuous conduction mode (CCM) is established based on the fractional calculus theory. And nonlinear dynamical bifurcation maps which use PI controller parameters and a reference current as bifurcation parameters are obtained. The nonlinear dynamic behavior is analyzed and compared with that of an integral-order forward converter. The results show that under certain operating conditions, the fractional-order forward converter exhibits bifurcations characterized by low-frequency oscillations and period-doubling as certain circuit and control parameters change. Under the same circuit conditions, there is a difference in the stable parameter region between the fractional and integral-order models of the forward converter. The stable zone of the fractional-order forward converter is larger than that of the integral-order one. Therefore, the circuit struggles to enter states of bifurcation and chaos. The stability domain for low-frequency oscillations and period-doubling bifurcations can be accurately predicted by using a small signal model and a predictive correction model of the fractional-order forward converter, respectively. Finally, by performing circuit simulations and hardware-in-the-loop experiments, the rationality and correctness of the theoretical analysis are verified.

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 3 A. 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.

Small-signal transmittances of the non-ideal flyback switch-mode DC–DC converter

Small-signal transmittances of the power stage of a flyback converter in continuous conduction mode are derived on the averaged model obtained by the separation of variables approach. The precise knowledge of these transmittances is necessary in the design process of the converter control circuit. Apart from mathematical formulas for transmittances, the numerical calculations of the frequency dependencies of the transmittances for the assumed set of the converter parameters are presented with the parasitic resistances of components taken into account. The results of the calculations are compared with the measurements performed on the laboratory model of the converter and a good consistency is observed. It is concluded, that the results of the paper may be useful in the designing process of a control circuit of the flyback converter.

Investigation of the Effect of Different Electromagnetic Interference Filter Topologies to DC–DC Boost Converter for Continuous Conduction Mode

Investigation of the Effect of Different Electromagnetic Interference Filter Topologies to DC–DC Boost Converter for Continuous Conduction Mode

Evaluation of custom-designed lateral power transistors in a silicon-on-insulator process in a synchronous buck converter

Most of todays power converters are based on power semiconductors, which are built in vertical power semiconductor processes. These devices result in limited packaging possibilities, which lead to physically long galvanic connections and therefore high external electromagnetic fields. These fields compromise power quality significantly. Therefore this paper examines the possibility to use lateral silicon-on-insulator power MOSFETs and uses the custom-made devices in a 48 V to 12 V synchronous buck converter in continuous conduction mode. The converter is designed based on custom made power transistors, implemented and verified by experimental results. The resulting efficiency of the 1 Wconverter is around 93 % across a wide load range and its temperature rise is less the 10 C. This leads to the conclusion, that modern lateral silicon-on-insulator power processes allow high integration of power stages and therefore promise lower emissions, leading to higher power quality.

Adaptive slope compensation technology for current-mode controlled SIDO DC-DC converter in continuous conduction mode

Adaptive slope compensation technology for current-mode controlled SIDO DC-DC converter in continuous conduction mode

A pulse train controlled Buck converter based on a single memristive multi-vibrator

ABSTRACT Memristors (MRs) have been used in integrated circuit design due to their nanoscale size and low power consumption. In this study, a flux-controlled binary MR emulator is designed by using off-the-shelf circuit components. Then, two MR-based multi-vibrators are constructed and applied to pulse train (PT) controlled Buck converters. Compared with traditional PT controlled Buck converters requiring two pulse train generators, only one single memristive pulse generator with controllable duty cycle is used to regulate the output voltage. To suppress the low-frequency oscillations of the PT-controlled Buck converter in continuous conduction mode (CCM), an inductor current based PT (IC-PT) control method is devised with the proposed MR-based pulse generator. Simulation and experimental results both show that the IC-PT-controlled Buck converter with the MR-based pulse generator can achieve fast transient response and minimum low-frequency voltage oscillations in the CCM.

High gain modified SEPIC converter with asymmetrical switched inductor super lift cell for renewable energy applications

ABSTRACT This paper provides a modified single-ended primary inductor converter (SEPIC) with an asymmetrical switched inductor super lift cell (ASISLC) for renewable energy applications. Solar, fuel cells, and so on, provide low output voltage, which is not sufficient for high voltage dc grid or dc loads. Therefore, the existence of a high gain DC-DC converter is mandatory. The proposed converter provides high gain, high efficiency, and less voltage stress at a low duty cycle. The proposed converter incorporates switched inductor together with a super lift cell. The super lift cell has a charge pump capacitor is connected in an asymmetrical fashion. The proposed converter offers continuous current at the input together with the above-mentioned advantages. This paper explains the operation of the ASISLC SEPIC converter in continuous conduction mode (CCM) and discontinuous conduction mode (DCM). The operating principle, theoretical analysis, design process, and comparison of the suggested converters with converters from the literature that use similar operating principles are all discussed in this paper. A MATLAB simulation is done and their results are provided. Finally, a hardware prototype for 200W, 50 kHz switching frequency is built and their results are validated to authenticate the effectiveness of the proposed converter.

New multi‐operational multi‐port DC–DC converter with bidirectional capability

AbstractA new triple‐input DC–DC converter with bidirectional ability is proposed in this paper. This converter is an interface between two unidirectional ports, one bidirectional port for the battery, and a DC link. This makes the proposed converter suitable for hybrid energy systems (HES). The load power can be provided by each input source separately or simultaneously. Also, the battery can be charged by input sources as well as with the energy returned from the output. These features provide a high degree of flexibility for the proposed converter. Boost and buck‐boost operation and low‐voltage stress on semiconductors are other advantages of the proposed converter. The performance of the converter in continuous conduction mode (CCM) is given along with the governing mathematical equations. The experimental results on a laboratory prototype confirm the theoretical calculations.

Sensorless Current-Sharing Scheme for Multiphase DC-DC Boost Converters

Accurate current sharing is beneficial to realize uniform heat distribution and electrical stresses in multiphase converters. Most of the present current-sharing schemes need many current sensors which increase the cost and decrease the system reliability. To solve this problem, a sensorless current-sharing scheme is proposed to balance the phase currents of multiphase dc–dc boost converters in continuous conduction mode. By converting the inner resistances of inductors and switches to series resistances on the input side, the actual converter model is simplified. Regarding one duty cycle as reference, the relationship between duty cycle and series resistance ratio (SSR) is derived for equal current distribution. After that, two methods are provided to obtain the SSRs. One is based on duty disturbance and the other is based on current measurement. Actually, the phase with largest series resistance is chosen as reference to improve the transient response. Despite phase number, only output and input voltages are measured to achieve output voltage regulation and current balance in the overall control scheme. The validity of proposed scheme is verified on a three-phase dc–dc boost converter.

Reducing Low-Frequency Ripple Using Alternative Output Capacitor Connection on Integrated Converters for LED Drivers

Although advantageous in several aspects, the integration of converters leads to a loss of independence between the converter's stages, since both stages are controlled by the same active switch. This condition makes it impractical to adopt control techniques that act on the duty-cycle to mitigate the low-frequency ripple at the output current without distorting the line current. The low-frequency ripple transferred from the bus voltage to the LED current has been studied for integrated converters operated at constant duty-cycle. To comply with IEEE 1789-2015 recommendation, the integrated converters use large capacitors to mitigate the low-frequency ripple. Converters operating in discontinuous conduction mode (DCM) have been widely adopted because they transfer less ripple to the output than converters operating in continuous conduction mode (CCM). A novel circuit arrangement for the buck-boost power control (PC) stage integrated with a buck-boost power factor correction (PFC) stage is explored in this paper as a technique to minimize the low-frequency output ripple for converters operating at constant duty-cycle and CCM. The proposed circuit provides current feedback to the bus capacitor, acting to reduce the output current and bus voltage low-frequency ripple. A dynamic model for the proposed converter in CCM is obtained and used to determine the output current modulation as a function of converter parameters. It is shown that the proposed topology leads to a smaller low-frequency ripple than a conventional counterpart at the same operating point. A 95 W design example and a prototype supplying an LED load of 98.8 V / 960 mA for the proposed circuit and the conventional counterpart are presented. The experimental results show that the proposed arrangement can achieve similar results to the conventional circuit in efficiency, THD, or semiconductor stress, while the obtained output current modulation equals to 8.66 % is 3.5 times lower than that in the conventional circuit at same operating point and component values.

Systematic Synthesis of Multiple-Input and Multiple-Output DC–DC Converters for Nonisolated Applications

Multiple-input converters (MICs) and multiple-output converters (MOCs) are attractive solutions for interfacing various voltage levels. In order to reveal the intrinsic relationships among the diverse topologies and provide as many viable topologies as possible for practical applications, this article aims to analyze the topology construction principles and propose a systematic approach to derive MICs and MOCs. To begin with, the general principle of the topology derivation is analyzed according to circuit network theory. Inspired by the idea of design controllable inductor power-flow loops (IPFLs), five construction types are proposed to create multiple power-flow network (MPN) in MICs and MOCs. Then, four basic switching cells for the topology synthesis are proposed and a flow diagram for the optimal design procedure is provided to guide the topology derivation. As one example, a family of viable and optimized MICs and MOCs with various characteristics is derived from typical Buck converter. Based on the analysis of the derived converters in continuous conduction mode (CCM) and discontinuous conduction mode (DCM), the number of magnetic components is not increased at all so that they are promising candidates for applications requiring compact size and high integration. Besides, topology comparison and selection among a family of MICs is also conducted in view of practical specifications. Finally, one derived dual-input converter is analyzed in detail and experimentally verified to demonstrate the theoretical results.

New unidirectional step-up DC-DC converter for fuel-cell vehicle: Design and implementation

Supplying electric vehicles from renewable energy sources including fuel cells (FCs) is one of the significant challenges for large automotive companies. To match FC and electric vehicle's energy level, a DC-DC converter is needed, so the specifications of electric vehicles and FCs have to be considered. The present study proposes a new design for unidirectional DC-DC non-isolated boost converters with reasonable conversion rate, lower semiconductor stress, ripple-free input current, and higher efficiency. This paper analyzes the converters in continuous conduction mode (CCM), and critical mode is then evaluated. Next, the proposed converter and some other converters are compared. The inductance and capacitance values are calculated and the relationships of efficiency and losses are obtained. The performance of the proposed converter is evaluated using a dynamic analysis. The results of experiment and Matlab/Simulink simulation are used to confirm the accuracy of the theory under 94.5% implemented efficiency.

Simplified Double-Integral Sliding-Mode Control of PWM DC-AC Converter with Constant Switching Frequency

In this paper, a simplified double-integral sliding-mode control method for pulse-width-modulated dc-ac buck conversion is introduced. The control equation is derived based on the equivalent control method, in which the control-oriented model is developed using the averaged dynamics of the power converter in continuous conduction mode. In contrast with the conventional sliding-mode control schemes, the complexity of adding a capacitor current sensor, variable ramp voltage, and other relevant components is avoided. Furthermore, the control equation is translated into a simple electronic circuit with minimal added components, which reduces the practical implementation cost. The proposed control method rejects large disturbances, tracks the reference signal, and maintains a constant switching frequency. Systematic design procedure, control parameters selection, and stability conditions are presented. The design methodology is verified via simulating the proposed control circuit using Simscape Electrical in MATLAB. The control method is also compared with the conventional double-integral sliding-mode control scheme under load disturbances. The results show that the simplified control approach provides a fast transient response and robust tracking performance.

A non-cascading DC/DC quadratic boost converter with high voltage gain for PV applications

ABSTRACT This paper proposed a new quadratic boost converter featuring a high voltage conversion ratio, high efficiency, and comparatively low inductor currents using reduced redundant power processing and voltage lift configurations for PV applications. The proposed Quadratic Boost Converter (QBC) consists of fewer components and improves voltage gain at a lower duty cycle. Furthermore, the inductor and capacitor are controlled to reduce output current and voltage ripples. The operational modes, steady-state analysis, design aspects, and dynamic modelling of the converter in continuous conduction mode are discussed clearly. The performance of the proposed QBC is compared with different existing converters in terms of component count, voltage gain, voltage and current stress of the switching components, effective index, total switching device power, and component losses. A110W hardware prototype has been developed. The simulation and experimental results of the converter validate its performance and stated benefits. The efficiency curves for the proposed QBC for various load currents are presented, with a peak efficiency of 93.8%.

A new Buck-Boost converter with capability of eliminating right-half-plane zeros

ABSTRACT In this paper, a new Buck-Boost converter with coupled inductor that can eliminate right-half-plane (RHP) zeros is proposed. The steady-state model and small-signal model of the proposed Buck-Boost converter in continuous conduction mode (CCM) are established and analysed, and its control-to-output voltage transfer function is obtained. The condition for this proposed converter to eliminate RHP zeros is derived based on the Mason formula. The comparisons among the other extant four Buck-Boost converters and the proposed Buck-Boost converter are carried out, and it shows that the proposed Buck-Boost converter has the advantage of eliminating RHP zeros. Finally, some simulations and circuit experiments are presented for confirmation.