Stability analysis of a feedback-controlled resonant DC-DC converter

This paper reports on the stability analysis of one member of a dual-channel resonant DC-DC converter family. The study is confined to the buck configuration in symmetrical operation. The output voltage of the converter is controlled by a closed loop applying constant-frequency pulsewidth modulation. The dynamic analysis reveals that a bifurcation cascade develops as a result of increasing the loop gain. The trajectory of the variable-structure piecewise-linear nonlinear system pierces through the Poincare plane at the fixed point in state space when the loop gain is small. For stability criterion the positions of the characteristic multipliers of the Jacobian matrix belonging to the Poincare map function defined around the fixed point located in the Poincare plane is applied. In addition to the stability analysis, a bifurcation diagram is developed showing the four possible states of the feedback loop: the periodic, the quasi-periodic, the subharmonic, and the chaotic states. Simulation and test results verify the theory.     

Harmonic resonant DC-DC converter for low coupling transformers

A new harmonic resonant DC-DC converter is proposed. The harmonic resonant converter is related to the multi-resonant converter and is used for transformers with low coupling. Two harmonic frequencies are present during any resonant state and the switch voltage can be less than two times the input voltage     

带有高精度片上电流感应器的自适应开关频率降压型DC-DC变换器

本文提出了一种基于电流模式的PWM降压型DC-DC变换器。在高精度片上电流感应器的作用下,当负载不同时自动选择开关频率,提高了系统效率,并获得良好的瞬态响应。电流感应器采用简单的开关技术省去了复杂的运算放大器,但获得了高精度,减少了功率损耗,节省了芯片面积。此外,为了避免启动时的浪涌电流,设计了一种新型的软启动电路。芯片采用了0.5μm标准CMOS工艺,面积3.38mm2,电流感应器的精度可以达到99.5%@200mA,在5-18V的宽输入电压范围内可以输出2A的负载电流。     

On-chip CMOS current-sensing circuit for DC-DC buck converter

An on-chip CMOS current-sensing circuit for a DC-DC buck converter is presented. The circuit can measure the inductor current through sensing the voltage of the switch node during the converter on-state. By matching the MOSFETs, the achieved sense ratio is almost independent of temperature, model and supply voltage. The proposed circuit is suitable for low power DC-DC applications with high load current.     

A forward converter topology employing a resonant auxiliary circuit to achieve soft switching and power transformer resetting

This paper presents a forward converter topology that employs a small resonant auxiliary circuit. The advantages of the proposed topology include soft switching in both the main and auxiliary switches, recovery of the leakage inductance energy, simplified power transformer achieving self-reset without using the conventional reset winding, simple gate drive and control circuit, etc. Steady-state analysis is performed herein, and a design procedure is presented for general applications. A 35-75-Vdc to 5 Vdc 100-W prototype converter switched at a frequency of 200 kHz is built to verify the design, and 90% overall efficiency has been obtained experimentally at full load.     

A novel self-excited forward DC-DC converter withzero-voltage-switched resonant transitions using a saturable core

A novel self-excited forward DC-DC power converter is proposed. The turn-on and turn-off of the switch are zero-voltage-switching with resonant transition. A saturable core is used to achieve the self-excitation and the zero-voltage-switched resonant transition. The voltage waveform across the switch is trapezoidal with sinusoidal transitions, and the current waveform flowing through the switch is quasisquare. The switching losses, the conduction losses and the stresses of the switch are significantly reduced in the proposed power converter. The output voltage is determined by the ON duty ratio of the switch as in a PWM converter. Two methods to modulate the ON duty ratio are proposed. Both methods results in variable-frequency operation. Experiments on two 5 V, 20 A DC-DC power converters show good performance     

一种新型软开关DC-DC PWM升压变换器设计

为提高转换效率并降低电源开关的电流应力,提出一种基于新型有源缓冲电路的PWM DC-DC升压变换器。该有源缓冲电路使用ZVT—ZCT软开关技术,分别提供了总开关ZVT开启及ZCT闭合、辅助开关ZCS开启及ZCT闭合。消除了总开关额外的电流及电压应力,消除了辅助开关电压应力,且有源缓冲电路的耦合电感降低了电流应力。另外,通过连续将二极管添加到辅助开关电路,防止来自共振电路的输入电流应力进入总开关。实验结果表明,相比传统的PWM变换器,新的DC-DC PWM升压变换器在满负荷时电流应力降低且总体效率能达到98.7%。     

A LLC resonant converter with dual resonant frequency for high light load efficiency

This paper presents a new approach to achieve high light-load efficiency for inductor-inductor-capacitor (LLC) resonant converters. Compared with the conventional LLC resonant converters, an additional active resonant network is employed to give the proposed converter another resonant frequency and another steady state. Thereby, the proposed converter has advantages of narrow switching frequency range and high light-load efficiency. The operation principle and the resonant network switching strategy of the proposed converter are analysed, as well as the design considerations. A 1.2-kW prototype with silicon carbide (SiC) MOSFETs is built to verify the proposed converter. The peak efficiency is tested as 94.4% at 680 kHz. Especially, the light-load efficiency is improved from 89% to 91%.     

A dynamic equivalent circuit model for solid magnetic cores forhigh switching frequency operations

This paper presents a dynamic equivalent circuit model of solid magnetic cores for high frequency operations in power electronic circuits. The effects of eddy current, domain wall motion, and hysteresis are taken into account by distributed equivalent resistors and distributed nonideal differential inductors, respectively. The Preisach hysteresis model is employed to simulate hysteresis effects in the inductors. A discrete transform technique based on the transmission line method is adopted to develop a discrete model for numerical dynamic analysis. The resultant model is just a simple tridiagonal system of equations. Good agreement between computer simulations and measurements has confirmed the validity of the new model     

A zero-voltage transition boost converter using a zero-voltage switching auxiliary circuit

A soft switching boost converter with zero-voltage transition (ZVT) main switch using zero-voltage switching (ZVS) auxiliary switches is proposed. Various operating intervals of the converter are presented and analyzed. Design considerations are discussed. A design example with experimental results obtained from a 300-W, 250-kHz, 300-V output DC-DC converter is presented. A modified gating scheme to utilize the auxiliary switch in the main power processing is discussed. A 600-W, 100-kHz, 380 V output, 90-250 V AC, power factor corrected, AC-to-DC, boost converter with the modified gating scheme is presented. Results show that the main switch maintains ZVT while auxiliary switches retain ZVS for the complete specified line and load conditions. Parasitic oscillations existing in the converters proposed in the literature are completely removed.     

具有方波输出谐振逆变桥的直流——直流变换器的分析和设计

本文从具有方波输出谐振逆变桥的直流—直流变换器的基本结构出发,通过对电路元件进行简化处理,详细分析了电路在不同工作时限的输出特性,获得了开关的最小关断时间,进而以上述结论为依据,提出了这种电路的一种简单的设计方案.     

Re-lift circuit: a new DC-DC step-up (BOOST) converter

A re-lift circuit, which is a new DC-DC step-up (boost) converter, is proposed. This converter performs positive to positive DC-DC voltage increasing conversion with high output voltage     

A high-power high-frequency ZCS-ZVS-PWM buck converter using afeedback resonant circuit

This paper presents a buck DC-to-DC power converter using a novel lossless commutation cell for high switching frequency and high power operation. The proposed cell consists of a main and auxiliary switches, with ZVS and ZCS switching characteristics, respectively. The power converter control using this cell is realized by the PWM technique, with constant switching frequency operation. The complete operation principles, theoretical analysis, relevant equations, state-space phase, simulation and experimental results for the buck converter are presented     

Phase control for resonant DC-DC converter with class-DE inverter and class-E rectifier

In this paper, a phase control scheme for Class-DE-E dc-dc converter is proposed and its performance is clarified. The proposed circuit is composed of phase-controlled Class-DE inverter and Class-E rectifier. The proposed circuit achieves the fixed frequency control without frequency harmonics lower than the switching frequency. Moreover, it is possible to achieve the continuous control in a wide range of the line and load variations. The output voltage decreases in proportion to the increase of the phase shift. The proposed converter keeps the advantages of Class-DE-E dc-dc converter, namely, a high power conversion efficiency under a high-frequency operation and low switch-voltage stress. Especially, high power conversion efficiency can be kept for narrow range control. We present numerical calculations for the design and the numerical analyses to clarify the characteristics of the proposed control. By carrying out circuit experiments, we show a quantitative similarity between the numerical predictions and the experimental results. In our experiments, the measured efficiency is over 84% with 2.5 W output power for 1.0-MHz operating frequency at the nominal operation. Moreover, the output voltage is regulated from 100% to 39%, keeping over 57% power conversion efficiency by using the proposed control scheme.     

An improved ZCT-PWM DC-DC converter for high-power and frequency applications

In this paper, an improved active resonant snubber cell that overcomes most of the drawbacks of the normal zero-current transition (ZCT) pulsewidth-modulation (PWM) dc-dc converter is proposed. This snubber cell is especially suitable for an insulated gate bipolar transistor (IGBT) PWM converter at high power and frequency levels. The converter with the proposed snubber cell can operate successfully with soft switching under light-load conditions and at considerably high frequencies. The operation principles, a detailed steady-state analysis, and a snubber design procedure of a ZCT-PWM buck converter implemented with the proposed snubber cell are presented. Theoretical analysis is verified with a prototype of a 5-kW and 50-kHz IGBT-PWM buck converter. Additionally, at 90% output power, the overall efficiency of the proposed soft switching converter increases to about 98% from the value of 91% in the hard-switching case.     

Boolean-based fractional order SMC for switching systems: application to a DC-DC buck converter

The combination of sliding mode control and fractional order control (FOC) has received a considerable attention in the last years due to the advances and effectiveness of FOC solving robust control problems. This paper collects different methods to apply FOC in sliding mode problems through the use of fractional order surfaces and proposes a direct boolean control (BC) strategy based on this kind of surfaces. The application of BC is novel and takes advantage of avoiding the use of PWM. Simulation results for a DC-DC buck converter application are given to show the goodness of the proposed approach.     

软开关隔离型升压DC-DC变换器设计与实现

为了满足升压型变换器低成本和大功率密度的需求,本文提出了一种软开关单极隔离型DC-DC变换器。该变换器电路包含一个无损耗缓冲器,通过漏电感固定住开关的电压峰值,从而实现开关的ZVS关断。在失谐状态下,使用Lr-Cr串联谐振电路来实现二极管的ZCS关断。由于磁化电流低,相较于传统的基于反激的变换器,变压器的容量更少。在输出功率250W和开关频率100kHz的条件下进行了实际测试,提出的变换器的最大测量效率为97.0%。     

Analysis of a series resonant converter pulse width-modulated orcurrent-controlled for low switching loss

Pulse width modulation (PWM) and current-controlled switching are applied to a full-bridge series resonant converter to regulate the output from no load to full load with low switching loss and with a narrow range of frequency variation. Drive strategies, control law, component stress, and other steady-state functions are analyzed for both switching modes. The range of frequency variation of the resulting switching scheme is narrower than that of a normal square-wave drive. It is noted that the advantages of low switching stress and narrow band frequency variation can be extended over the entire range of voltage gain or load by combining PWM with current-controlled switching     

Novel sliding valley current mode pulse train control for switching DC-DC converter

ABSTRACT

Multi valley current mode pulse train (MVC-PT) control technology can completely eliminate the low-frequency oscillation phenomenon of DC-DC switching converters operated in continuous conduction mode (CCM). However, this method needs to increase the number of preset value to broaden the output power range, which will increase the complexity and cost of the controller, and reduce the robustness of the system. Meanwhile, the output voltage ripple is uncontrollable and varied with the changes of the load. In this paper, a novel sliding valley current mode PT (SVC-PT) control technique is proposed to solve the above-mentioned problem. The SVC-PT operating principle and the deficiency of MVC-PT method are analysed in details. The approximate discrete-time models of SVC-PT and MVC-PT controlled switching DC-DC converters are constructed and compared. The comparison results verify that the proposed control method can thoroughly lessen the restriction of the controller on the output power range. Moreover, the control circuit is simplified and the output voltage ripple can be controlled. Finally, the simulation and experimental results are present to prove the feasibility and scientific of SVC-PT control technology.     

Interleaved soft switching resonant converter with a small input ripple current

ABSTRACT

An interleaved frequency control soft switching converter is studied for solar power or fuel cell power applications. The proposed circuit topology contains two parallel current-fed circuit cells with interleaved pulse-width modulation operation. Thus, the ripple currents at input and output terminals are decreased. In each circuit cell, the proposed current-fed dc-dc converter includes boost circuit and resonant circuit to achieve current ripple-free on low voltage side and less switching losses on active devices. The boost circuit and the resonant circuit have same active devices to decrease power switches. Due to the resonant behaviour, the reverse recovery current loss on secondary diodes is removed. The voltage doubler circuit topology is accomplished on secondary-side to reduce diode counts and conduction loss. The performance and effectiveness of the developed interleaved PWM current-fed converter are verified and confirmed by experiments.