带纹波控制的全载高效率DC-DC变换器的设计

便携式通信设备对DC-DC变换器的轻载效率及输出电压纹波的要求较高,轻载时,降低频率可以提高效率,但会带来纹波的恶化。针对这种缺陷,深入研究了轻载下纹波与频率之间的关系,得到一种降低纹波的新颖方法—带电感电流峰值控制的PFM技术。基于CSMC 0.5μm标准CMOS工艺,完成了电路设计。仿真结果表明,与传统PFM相比,该方法显著减小了轻载时的输出电压纹波,减小幅度最高可达80%。     

LLC谐振变换器轻载输出电压稳定性研究

LLC谐振变换器在实际应用中,轻载输出电压稳定问题是普遍关注解决的难点问题。对特定条件下增益-频率不单调和变压器副边电压振荡两种常见导致轻载/空载输出电压失调的原因进行分析,提出实用化解决方案并进行了实验验证。另外,分析常见采用打嗝模式解决轻载输出电压稳定问题时纹波较大的原因并提出解决方案和进行实验验证。     

不连续导通模式PSM PT控制开关变换器

脉冲跳周期调制（Pulse Skip Modulation,PSM）采用ON/OFF控制对输出电压进行调整,提高了开关变换器的轻载效率,但存在输出电压纹波大的缺点。文中结合开关变换器的脉冲序列调制（Pulse Train,PT）控制与PSM技术,提出了开关变换器的PSM PT控制技术,其降低了输出电压的纹波,并使PT控制开关变换器在空载时能稳定工作。     

开关DC-DC变换器的自适应占空比跨周期控制方法

针对脉冲跨周期调制(PSM)开关DC-DC变换器输出电压纹波较大的问题,该文提出一种新型的自适应占空比跨周期(ADPS)控制方法。在ADPS控制的变换器中,轻载下,每个周期变换器控制脉冲的占空比与该周期开始时输出电压与参考电压误差的平方根近似成正比;负载越轻,变换器的输出电压纹波越小。研究表明,ADPS控制的DC-DC变换器不仅具有比PSM控制的变换器更低的输出电压纹波,同时具有优异的鲁棒性和瞬态响应能力。     

一种CLLLC谐振型双向DC/DC变换器效率优化技术研究

为提升CLLLC谐振型双向DC-DC变换器的工作效率，文中提出一种基于间歇控制技术的变频恒压控制方法。首先，建立变换器基波等效模型得到变换器的电压增益和传输效率特性，通过对原边逆变器的变频控制来改变电压增益，实现输出的恒压控制；然后，针对变换器在轻载时效率较低的情况，提出一种效率优化控制方法，在改变原边逆变器工作频率的同时改变间歇控制占空比，使副边整流器的输入等效负载维持在最优负载处，实现变换器的高效恒压输出；最后，搭建一台30 W的实验样机验证所提方法的可行性和有效性。实验结果表明，变换器轻载时，采用间歇控制变频恒压方法的工作效率比采用变频恒压控制方法提高约6%，在整个负载范围内效率可达87%以上。     

DC-DC变换器突加负载时的动态性能研究

提出了一种能够有效改善DC-DC变换器动态性能的方案。该方案是在全桥电路基础上并联一单端正激变换电路，使变换器负载从10%轻载突加到100%满载时，其暂态过程小于1μs输出电压达到设计要求。文中对具体电路进行了详细分析，并通过仿真进行了验证。     

新型矩阵式变频器在变频电梯中的应用

因为变频电梯在运行时,变频器输出存在大量谐波,本文介绍了一种新型的功率变换器,引入了电压电流双闭环控制策略,分析了一种新型的矩阵变换器输出电压和电流的谐波成分及影响因素.通过MATLAB/SIMULINK软件进行了仿真实验.结果表明.与传统的变频器相比,矩阵变换器结合输出电压电流双闭环控制,能够有效地降低输出电压电流谐波,并能抑制输入侧谐波对输出电压电流的影响。     

异步电动机最小损耗LMC的工程实现

变频调速技术的发展对异步电机系统的节能降耗起到了巨大的推动作用,但一般采用额定恒励磁控制,电机在空载或轻载稳态运行时,效率会明显下降;也就是低电磁转矩、低转速,低电磁转矩、高转速,高电磁转矩、低转速等情况下,效率均会明显下降。本文以异步电动机矢量控制变频调速系统为对象,针对其轻载稳态运行工况,将基于损耗模型的异步电动机最小损耗控制策略进行了工程实现。详细论述了工程实现的过程。     

基于UC3875的复合式全桥三电平变换器的研究

文中研究了一种基于UC3875的复合式全桥三电平变换器。该变换器可以降低开关管的电压应力,利用开关管的寄生电容与变压器的漏感在较宽的负载范围内实现ZVS,在减小输出滤波器的容量和体积的同时,有效地提高了效率。对该变换器进行了仿真分析并通过一台600W的原理样机进行验证,给出了实验结果。     

一种用于恒压AC-DC变换器的新型模拟指数波产生电路

本文提出了一种用于恒压AC-DC变换器的新型模拟指数波产生电路,并据此设计了一种受误差放大器输出动态调节幅值的可变指数波产生电路。该结构能够解决传统三角波恒压控制负载调节范围窄的问题,且相比于其他指数波电路,本文电路结构简单,可以有效节省版图面积,输出波形平滑,误差较小。本文对提出的指数波产生电路输出电压进行了完整的分析和公式推导,并基于Nuvoton 0.35um BCD工艺在Cadence Spectre仿真平台上验证了指数波产生电路的可行性和有效性。经仿真验证,轻载下的开关频率能够降低为三角波控制方式下的1/4,有效降低了轻载开关频率。且改进后指数波应用于恒压AC-DC变换器系统中负载调整率仅为0.542mV/mA。     

Analysis and Design of a Novel Three-Phase AC–DC Buck-Boost Converter

This paper proposes a novel three-phase ac-dc buck-boost converter. The proposed converter uses four active switches, which are driven by only one control signal. This converter is operated in discontinuous conduction mode (DCM) by using the pulsewidth modulation (PWM) technique, and the control scheme very easily and simply achieves purely sinusoidal input current, high power factor, low total harmonic distortion of the input current and step-up/down output voltage. Also, the proposed converter provides a constant average current to the output capacitor and load in each switching period. Thus, the ripple component of sixth times line frequency will not appear in the output voltage. Therefore, a smaller output capacitor can be used in the proposed converter. Moreover, the steady-state analysis of voltage gain and boundary operating condition are presented. Also, the selections of inductor, output capacitor and input filter are depicted. Finally, a prototype circuit with simple control logic is implemented to illustrate the theoretical analysis.     

Adaptive off-time control for variable-frequency, soft-switchedflyback converter at light loads

The soft switching of a flyback converter can be achieved by operating the circuit in the critical conduction mode. However, the critical-mode operation at light loads cannot be maintained due to a very high switching frequency and the loss of the output voltage regulation. A control which regulates the output down to the zero load and maintains soft switching at light loads is proposed. The proposed control scheme was implemented in the 380 V/19 V, 65 W flyback DC/DC converter     

Boost变换器跨周期调制(PSM)的状态空间平均模型

基于Boost变换器,利用状态空间平均法对跨周调制(Pulse Skipping Modulation,PSM)进行建模和特性分析,推导出电感电流连续(CCM)和电感电流断续(DCM)时系统变压比,调制度M与负载的关系及系统转换效率的理想化公式,得到PSM具有轻载下高转换效率的结论,并设计具有PSM调制特性的控制电路,给出仿真结果。     

On the output voltage ripple in the ideal boost and buck-boost dc–dc converters

This paper re-examines the typical textbook analysis of the ideal boost and buck-boost dc–dc converters operating in the continuous conduction mode. It is shown that there is a range of valid average load currents for which the simple equation usually derived to relate output voltage ripple to output capacitor size in both converters is not strictly correct. An equation giving the correct relationship for the range of load currents in question is derived, using basic concepts. It is shown that the error introduced by using the original equation where the new one is appropriate is significant if both the switching duty cycle of the converter is relatively small (～0.3 or smaller) and the average load current is close to the continuous conduction cutoff. In such cases the size of the output capacitor needed to meet a maximum output voltage ripple specification will be significantly underestimated. The results are illustrated with an example and PSPICE verification.     

A single-switch AC/DC converter with voltage regulated storage capacitor

A single-stage power-factor-corrected AC/DC converter (SSPFC) usually causes high voltage stress on the intermediate storage capacitor, due to the lack of control of this voltage. The storage capacitor voltage varies largely with line voltage, and load current and is usually higher than the peak line voltage. This paper presents a new single-switch SSPFC based on a flyback topology for which the storage capacitor voltage is loosely regulated by the output voltage. Without using extra power switches to increase the control dimension, the proposed converter uses a flyback converter with dual-output transformer to achieve the control purpose. The range of storage capacitor voltage change against the change of input voltage and load current is significantly reduced. Moreover, the maximum storage capacitor voltage can stay below the peak line voltage at high line condition. Experimental results verifying the operation of the proposed SSPFC are also reported.     

一种新型单级功率因数校正AC/DC变换器的研究

文章研究了一种新型单级单开关PFC反激变换器。该变换器负载变轻时其储能电容电压不会飘升,应用于宽范围交流输入电压,储能电容电压低于450V。变换器用其变压器中的一个附加绕组实现了升压功能。由于省去了大电感,减小了变换器的体积和重量,在中小功率应用场合下,变换器符合IEC61000-3-2class D谐波标准,并且具有输出电压快速调节能力。     

输出可调谐振开关电容变换器潜电路分析

对输出可调谐振开关电容变换器中存在的潜电路进行了研究,对潜电路状态及其激励条件进行了分析,讨论了减小潜电路影响的措施。仿真对比分析证明,输出可调谐振开关电容变换器的输出功率存在限制;同时,采取适当的限制措施,对提高系统响应和抑制电源干扰和负载变化有较好的作用。     

基于电流型控制的LED恒流源分析与设计

设计了一种输出功率约50W的LED恒流源驱动模块, 其负载为由多只LED管(每只功率为1W)采用混联方式组成的LED阵列。通过对其电流型反激式变换及恒流控制电路的设计与试制, 并在不同输入电压下, 改变负载测试, 可看出其电流变化规律基本相似。随着负载变小, 输出电压升高, 输出电流逐渐减小, 输出电流稳定度达4.6%。在一定负载时, 输出电压值保持在47.2V左右, 电压纹波峰-峰值约为400mV。电流波动约0.05A, 输出电流稳定可靠, 可用于对多只串并混联的LED阵列驱动供电。     

基于电流型控制的LED恒流源分析与设计

设计了一种输出功率约50W的LED恒流源驱动模块,其负载为由多只LED管(每只功率为1W)采用混联方式组成的LED阵列。通过对其电流型反激式变换及恒流控制电路的设计与试制,并在不同输入电压下,改变负载测试,可看出其电流变化规律基本相似。随着负载变小,输出电压升高,输出电流逐渐减小,输出电流稳定度达4.6%。在一定负载时,输出电压值保持在47.2V左右,电压纹波峰-峰值约为400mV。电流波动约0.05A,输出电流稳定可靠,可用于对多只串并混联的LED阵列驱动供电。     

A ZCS Current-Fed Full-Bridge PWM Converter With Self-Adaptable Soft-Switching Snubber Energy

A new soft-switched, current-driven full-bridge converter is presented. The structure utilizes a simple snubber formed by two unidirectional switches and a capacitor to realize soft-switching operation over a wide line and load range. All primary-side switches are operated with zero-current switching (ZCS) and the snubber switches are operated with zero-voltage switching. The energy used for soft-switching is self-adaptable. For a given input current, the snubber capacitor is charged to the minimum required energy for ZCS of the switches. Thus, less resonant energy is used and the conduction loss can be kept minimal. The cyclical switching operation and control of the converter will be discussed. By compromising the voltage stress on the switches and loss of duty cycle (i.e., the regulation range), an optimized design procedure of the circuit elements is derived. The input voltage range and load variation that ensure both output voltage regulation and soft switching are determined. By studying the small-signal characteristics of the entire system, a current-controlled feedback control circuit has been implemented with a DSP. The experimental results measured on a 5-kW, 530-V/15-kV prototype confirms the advantages of the proposed converter.