Low Output Voltage Applications Research Articles

A High Efficiency Δ-Lr-Y Type Three-Phase Interleaved LLC Converter With Less Transformer Loss

Y-type three-phase interleaved LLC has advantages in high-power applications with small output current ripple. However, the traditional Y-type three-phase interleaved LLC has large winding current under low output voltage and high power (LVHP) applications, which affects the efficiency and power density. In this paper, a high efficiency delta-type three-phase interleaved LLC topology with less transformer losses was proposed. This paper verifies that the transformer loss of the proposed topology is lower than that of the traditional Y-type topology based on the loss model and simulation. Furthermore, considering the coupling between three-phase transformers, a more accurate soft-switching analysis method and the first harmonic gain formula of the proposed topology are given. According to the analysis results, compared with the traditional Y-type topology, only half of the magnetizing current was needed to achieve soft-switching. Meanwhile, the length of the transformer air gap is one-third of the traditional Y-type topology, which can reduce the fringing loss. Finally, a 3 kW prototype was designed and verified. Compared with the Y-type, this paper achieves 19.2% loss reduction.

Closed Loop Modified SEPIC Converter for Photovoltaic System

The high static gain modified single ended primary coil (MSEPIC) converter is presented in this paper. The proposed converter presents low switch voltage and high efficiency for low input voltage and high output voltage applications. The configuration of MSEPIC converter is presented and analyzed. Closed loop feedback control with PID controller based on triggering system is developed for MSEPIC converter to maintain constant output voltage. Furthermore, the model is integrated with Photovoltaic generator where the input voltage and current depend on the solar irradiation rates. The proposed model is analyzed and simulated in Matlab/Simulink and m-file code. Simulation model is developed with a maximum power at full sun equal to 315 W, which presents efficiency equal to 99.03%. The PID controller works as intended, as the output voltage can approach the expected value. Furthermore, performance and robustness are tested by load variations and set point variations.

Variable Frequency Control for Isolated, Nonresonant Single-Stage AC–DC Converter With a Constant DC-Link Voltage

This article proposes a system, which comprises an isolated, nonresonant single-stage ac–dc converter with variable frequency control. One of the main contributions of this article is that the proposed system ensures a stable dc-link voltage independent of power flow, which improves the reliability of the system. Moreover, it eliminates the capacitor imbalance issue when using pulsewidth modulation control in bridgeless, nonresonant single-stage converters. Due to this, a minimal output capacitance is needed to regulate the output current in low output voltage applications tightly. The proposed system shows high flexibility in controlling the current waveforms, which enables soft switching for all turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> instants of the switches. A new equivalent circuit is introduced to study the steady-state operation of the proposed system accurately. Experimental and simulation results are provided for a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$250 \, \mathrm{W}$</tex-math></inline-formula> prototype to demonstrate the superior performance of the proposed system.

Implementation of High Precision Error Amplification Scheme for AC-DC Converter

these days, demand for small volume and low cost of the home automation device is getting higher and higher. Converter with single-stage scheme has advantages of simple structure, low cost, and small theoretical volume, but it often suffers bad output accuracy in low output voltage applications. This paper proposes a constant voltage compensation circuit for AC/DC converters to improve the output accuracy which can also be used in a BUCK AC/DC converter with low output voltage. To verify the feasibility of the proposed compensation method, a BUCK controller based on the proposed circuit is implemented in Episil 0.5μm/40V-HVCMOS process and occupies a die size of 0.99×0.8 mm2. By the help of the proposed circuit, the output accuracy of the prototype with single-stage structure, which has advantages of small volume and low cost, can reach as high as those converters with multi-stage structure. Test results show that the load regulation of the prototype is about 1.3% with 3.3V output and less than 0.9% with 5V and 12V outputs.

A New Dead Time Regulation Synchronous Rectification Control Method for High Efficiency LLC Resonant Converters

In low output voltage and high output current LLC resonant converter applications, a synchronous rectification (SR) is essential component for high efficiency and high power density. However, stray inductances in MOSFET package and printed circuit board (PCB) pattern make premature turn-off of SR gate and large SR dead time. To compensate the stray inductance effect and increase system efficiency, a hysteresis band dead time regulation control method is proposed. In the proposed control method, SR dead time is regulated to predetermined dead time target regardless of the stray inductances by using a mixed signal, which includes instantaneous drain voltage information and previous cycle dead time information. As a result, the proposed control method can provide lower conduction losses by the dead time regulation and better transient characteristic by the instantaneous drain voltage information. To verify the validity of the proposed control method, 234-W prototype is built and experimented with the proposed controller, which is implemented with 0.25-μm BCDMOS technology.

Discontinuous Conduction Mode Operation of the Current-Shaping Modular Multilevel DC–DC Converter

The Current Shaping Modular Multilevel DC-DC Converter (CS-MMC) is a recently proposed class of modular multilevel dc-dc converters for dc distribution grid applications consisting of a single string of cascaded voltage source submodule cells (VSMs), a current source submodule (CSM) and notably no series inductor. In the CS-MMC, since it is the CSM that shapes the string current and there is no series inductor, this frequency can readily be in the medium-frequency range, enabling VSM cells to be realized with low cell capacitance. In the previous work, only continuous conduction mode (CCM) operation of the CS-MMC had been considered which led to several limitations including elevated switching losses and low utilization of the semiconductor devices in low output voltage applications. In this work, discontinuous conduction mode (DCM) operation is proposed for the CS-MMC which addresses these limitations. In traditional dc-dc converters, DCM is determined by the inductor current ripple. However, unique to the CS-MMC, DCM is determined by the VSM capacitor voltage ripple. In this work, the proposed DCM operational approach is presented along with its analysis and control. Both simulation and experimental results from a laboratory scale converter system are provided for validation.

MATLAB/Simulink based simulations of KY converter for PV panels powered LED lighting system

&lt;p&gt;The main objective of this research work is to develop KY conveter topology for renewable energy sources.Solar energy is the readily available and is the cheapest form of energy. It is non-polluting and environment friendly. The development of high static gain DC-DC converters is an important research area due to the crescent demand of this technology for several applications supplied by low DC output voltage power sources. It is used to provide the uninterruptable power supply and battery powered to the system. So here, step-up DC-DC converters based on the KY converter are proposed for LED lighting systems. The proposed topologies present high voltages and high efficiency for low input voltage and high output voltage applications. The simulation results of the proposed topology have been presented using MATLAB/SIMULINK software.&lt;/p&gt;

A Dual Half-Bridge Converter With Hybrid Rectifier for DC Power Supply in Railway Systems

Dual half-bridge (DHB) converter is a recent innovation in the family of full-bridge converters, and it can achieve higher efficiency compared to the traditional converters. The DHB converters with center-tapped rectifier (CTR) and full-bridge rectifier (FBR) have been adopted in low ( 200 V) output voltage applications, respectively. However, the output voltage is between 100 and 200 V in some applications, such as auxiliary railway dc power supply, both CTR and FBR can be the candidate and it is very indistinct to select the matched rectifier. To suit for such specific application, this article proposes a DHB converter with hybrid rectifier (Hyb-R). The Hyb-R is composed of a CTR section and an FBR section, which are connected in series by sharing two diodes. As a combined structure, the voltage stress of Hyb-R is between that of FBR and CTR, which makes Hyb-R well appropriate for dc power supply in railway systems. In this article, the operational principle and performance of the proposed converter are analyzed in depth. Three prototypes based on the DHB converters with CTR, FBR, and Hyb-R are built and tested, respectively. Experimental results show that the proposed converter can achieve a superior efficiency compared with other converters.

A Three-Winding Coupled-Inductor DC–DC Converter Topology With High Voltage Gain and Reduced Switch Stress

This paper presents a dc–dc boost converter topology for low input and high output voltage applications, such as photovoltaic systems, fuel cell systems, high-intensity discharge lamp, and electric vehicles. The suggested configuration consists of a three-winding coupled-inductor, a single switch and two hybrid voltage multiplier cells. Furthermore, two independent hybrid voltage multiplier cells are in parallel when the single switch S is turned on , and they are in series when the switch S is turned off . So, the advantages of the proposed converter structure are summarized as follows: 1) A coupled inductor with three windings is introduced in the presented converter structure. The two secondary windings of the coupled inductor are, respectively, used to form a hybrid multiplier cell on the one hand, on the other hand, it increases the control freedom of the voltage gain, enhances the utility rate of magnetic core and power density, and reduces the stress of power components to provide a stable constant dc output voltage. 2) The two hybrid multiplier cells can absorb synchronously the energy of stray inductance, which not only reduces the current stress of corresponding diodes, but also greatly alleviates the spike voltage of the main switch, which improves the efficiency. 3) The two hybrid multiplier cells are connected in series to supply power energy for the load, so the voltage gain is extended greatly due to this particular structure. Thus, low-voltage low-conduction-loss devices can be selected and the reverse-recovery currents within the diodes are inhibited. The operating principles and the steady state analyses of the proposed converter are discussed in detail. Finally, a test prototype has been implemented in the laboratory, and the simulated and experimental results show satisfactory agreement with the theoretical analysis.

An LLC Converter Family With Auxiliary Switch for Hold-Up Mode Operation

This paper proposed a new half-bridge (HB) LLC resonant converter family with pulse-width modulated (PWM) auxiliary switch (sLLC converter) for hold-up mode operation. The proposed sLLC converters could operate with synchronous rectifier, which is suitable for low-output voltage applications. In the proposed converters, an auxiliary switch is added at the primary side to provide charging path for the series resonant inductor. For nominal 400-V input, sLLC achieves same performance as conventional LLC converter, and all the good features such as soft switching are naturally retained. For slight input voltage fluctuation, frequency modulation is used to regulate the output voltage. When the input voltage reduces further, HB switches will operate at constant minimum frequency, and the auxiliary switch will operate in the PWM mode to energize the resonant inductor with the bus voltage directly during hold-up period. Thus, the converter achieves higher voltage gain, and the output voltage can be maintained at desired level. To verify the effectiveness of the proposed sLLC converter, operational principle and equivalent circuits will be carefully explained and analyzed in this paper. A 300-W prototype is built for 250–400-V input 12-V output application.

A New High Step-down DC-DC Converter for Renewable Energy System Applications

This paper proposes a new topology of a high step-down dc-dc converter with a conversion ratio of approximately 20 times for high-input and low-output voltage applications such as renewable system applications. This proposed converter employs only one single switch with low control complexity. In this paper, the converter configuration is presented and its operating principle under continuous conduction mode (CCM) is described. The relationship between the step-down voltage ratio and the duty cycle is also presented in order to illustrate the performance of the proposed converter. In addition, the laboratory phototype of the proposed converter is implemented. The simulation and experimental results are shown to demonstrate the effectiveness of the proposed high step-down single-switch dc-dc converter.

Decentralized Inverse-Droop Control for Input-Series–Output-Parallel DC–DC Converters

Input-series-output-parallel dc–dc converters are suited for high-input voltage and low output voltage applications. This letter presents a decentralized inverse-droop control for this configuration. Each module is self-contained and no central controller is needed; thus, improving the system modularity, reliability, and flexibility. With the proposed inverse-droop control, the output voltage reference rises as the load becomes heavy. Even though the input voltages are not used in the inverse-droop loop, the power sharing including input voltage sharing and output current sharing can still be well achieved. Besides, the output voltage regulation characteristic is not affected by the variation of input voltage. The operation principle is introduced, and stability of the strategy is also revealed based on small signal modeling. Finally, the experiment is conducted to verify the effectiveness of the control strategy.

A Modified SEPIC Converter With High Static Gain for Renewable Applications

Two high static gain step-up dc-dc converters based on the modified SEPIC converter are presented in this paper. The proposed topologies present low switch voltage and high efficiency for low input voltage and high output voltage applications. The configurations with magnetic coupling and without magnetic coupling are presented and analyzed. The magnetic coupling allows the increase of the static gain maintaining a reduced switch voltage. The theoretical analysis and experimental results show that both structures are suitable for high static gain applications as a renewable power sources with low dc output voltage. Two experimental prototypes were developed with an input voltage equal to 15 V and an output power equal to 100 W. The efficiency at nominal power obtained with the prototype without magnetic coupling was equal to 91.9% with an output voltage of 150 V. The prototype with magnetic coupling operating with an output voltage equal to 300 V, presents an efficiency at nominal power equal to 92.2%.

Comparison of the Synchronous-Rectified Push–Pull Converter with LLC DC to DC Converter

This paper deals the comparison of soft switched push–pull type LLC series resonant converter with proposed soft-switched self-driven synchronous-rectified push–pull converter. The 48 V DC is efficiently reduced to 12 V using DC to DC converter at 20 KHz switching using both methods. Performance of proposed synchronous-rectified push–pull converter is compared with push–pull LLC series resonant converter in low output voltage applications. This converter has advantages like reduced switching loses stresses and EMI. Laboratory model of microcontroller-based DC to DC converters are fabricated and tested. The experimental results are compared with simulation results.

0 ~ 100 % 시비율을 갖는 새로운 모드 가변형 비대칭 풀 브리지 DC/DC 컨버터

In this paper, a new mode changeable asymmetric full bridge dc/dc converter is proposed to solve the freewheeling current problem of the conventional zero voltage switching(ZVS) phase shift full bridge(PSFB) dc/dc converter of low output voltage and high output current applications. The proposed converter is operated as an asymmetric full bridge converter when the duty cycle is less than 50% and active clamp full bridge converter when the duty cycle is greater than 50%. As a result, since its freewheeling current is eliminated, the conduction loss is lower than that of the conventional ZVS PSFB dc/dc converter. Moreover, ZVS of all power switches can be ensured along a wide load ranges and output current ripple is very small. Therefore, high efficiency of the proposed converter can be achieved. Especially since its operation mode is changed to the active clamp full bridge converter during hold up time and can be operated with 50~100% duty ratio, it can produce the stable output voltage along wide input voltage range. The operational principles, theoretical analysis and design considerations are presented. To confirm the operation, validity and features of the proposed converter, experimental results from a 1.2kW() prototype are presented.

Advanced power semiconductors and ICs for DC/DC converter applications

This paper describes recent advances in power semiconductor devices, integrated circuits, and packages for DC/DC converter applications. Special emphasis is placed on the latest discrete power MOSFET devices and packages. Features and trends in ICs for control of synchronous buck converters are highlighted as well. The paper will also cover a new class of miniaturized hybrid assembly that sets new efficiency standards for high current low output voltage applications.

Active clamped ZVS forward converter with soft-switched synchronous rectifier for high efficiency, low output voltage applications

The analysis, design, and implementation of an active clamped ZVS forward converter equipped with a soft-switched synchronous rectifier (ACFC-SR), proposed for high-efficiency low output voltage DC-DC converter applications, is presented. The converter efficiency is maximised due to soft switching of the main, active clamp, synchronous rectifier, and freewheeling MOSFET switches. The operating principles of the ACFC-SR are analysed in detail, and the converter performance is compared with that of alternative forward converter schemes employed in low output voltage DC-DC converters, in view of their power conversion efficiency. Experimental results are presented for a 50 W ACFC-SR converter with a DC input voltage of 48 V, an output voltage of 5 V, and operating at a switching frequency of 120 kHz. In general, good agreement is observed between the theoretical and experimental results.

Design considerations of power MOSFET for high frequency synchronous rectification

Synchronous rectifiers used in high frequency, low output voltage applications are power MOSFETs specially designed to replace the usual output Schottky diodes in order to reduce converter losses. This paper deals with the analysis and design optimization of a synchronous rectifier suitable for applications of 1 to 10 MHz switching-mode power supplies. Three different MOSFET structures were studied and evaluated through detailed 2-dimensional device simulations. The internal parameters are optimized against three major performance factors, namely (1) the recovery time of the body diode, (2) the product of on-state resistance and input capacitance, i.e., the loss factor, and (3) the breakdown voltage of the body diode. Based on the evaluation, the UMOS structure produces the lowest RC loss factor and the shortest body diode reverse recovery. The final design optimization of the UMOS was then carried out and an optimized device is presented as the final design. >