PS—FB—ZVSPWM DC／DC变换器中副边占空比丢失问题的研究

移相控制ZVSPWM DC／DC全桥变换器是变换器的一个研究热点,诸如高性能、高效率、低噪声、低污染等理论问题急待研究。副边占空比丢失是移相全桥PWM DC／DC变换器中的一个重要现象,文章以移相全桥ZVSPWM DC／IX;变换器电路模型为基础,结合变换器谐振电路的工作特点,对变换器副边占空比丢失的原因进行了详尽的分析,阐述了全桥变换器滞后臂比超前臂更难实现ZVS的原因,最终得到了移相全桥ZVSPWM DC／DC变换器死区时间和工作频率的设置条件与解决副边占空比丢失的措施。     

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     

Sigma-Delta调制及其在低噪声DC-DC变换器的应用

分析了传统PWM调制和Sigma-Delta调制在噪声性能方面的差异,以及它们对DC-DC变换器输出噪声的影响。在Chartered 0.35μm CMOS工艺条件下实现了一个基于二阶Sigma-Delta调制的低噪声DC-DC变换器,并对其中Sigma-Delta调制模块进行了流片验证。测试结果表明,Sigma-Delta调制模块能够将环路带宽内噪声抑制到-50 dB左右,并且未引入与开关频率有关的谐波成分。仿真结果表明,DC-DC变换器输出电压噪底能够达到-60 dB以下。     

PWM半桥变换器电路仿真

随着电力电子技术的迅速发展,PWM型DC-DC变换器的应用日益广泛。如今,高性能、高效率、小型化和轻量化越来越成为各类DC-DC变换器追求的目标。文中优选电路结构简单、容易控制的半桥电路作为直直变换拓扑,在剖析了脉宽调制对称半桥变换器工作原理及特性后,设计出270 V直流输入、360 V直流输出、输出功率为500 W变换器的相关参数。切实了解SG1525芯片脉冲产生原理后,设计出控制电路参数,从而搭建出完整的闭环系统。详尽分析了所得出仿真结果,并以此验证了理论分析和工程设计的正确性。     

开关稳压电源系统设计

文章构建了基于Boost型变换器的DC/DC变换器,系统以专用芯片UC3842作为控制核心,辅以Atmega128单片机稳定输出电压。利用UC3842自身的电压电流环反馈,加上输出电压均值环设计成输出电压稳定可调的DC/DC变换电路。本系统还采用了模拟PWM技术、在线保护技术、人机交互技术。实际测试表明该系统各项指标均达到或超过设计要求。     

A comparison of nondeterministic and deterministic switchingmethods for DC-DC power converters

An analysis and experimental results of the random pulsewidth modulation (RPWM) and random pulse-position modulation (RPPM) methods for DC-DC converters are presented. The characteristics and performance of power converters under two randomized modulations are evaluated. The theoretical relationships of discrete harmonics, continuous noise, and output-voltage ripple of the RPWM and RPPM schemes are established and compared with those of a standard deterministic pulsewidth modulation (PWM) scheme in a buck converter. Limitations in the randomly switched DC-DC converters, which have not been addressed before, are highlighted. Randomized schemes generally have inherent problems in achieving low-output-voltage ripple due to the low-frequency continuous noise within the passband of the converter filter. The inherent low-frequency noise-induced voltage ripple problems of nondeterministic switching methods for DC converters are confirmed experimentally. The performance of the RPPM method is found to be closer to the standard PWM method than that of the RPWM method. For DC-DC power conversion, the RPPM method offers much better output-voltage performance than the RPWM method     

A continuously variable hydraulic pressure converter based on high-speed on–off valves

A continuously variable hydraulic pressure converter utilizing high-speed on–off valves is studied in this paper. The hydraulic pressure converter is analogous to a switchmode buck converter in power electronics. Substituting the electronic components in the buck converter with their hydraulic counterparts, a hydraulic pressure converter is built. The steady state and fluctuation characteristics of the hydraulic pressure converter are studied in both the theoretical analysis and the simulation. The hydraulic pressure converter was built and tested. Experimental results show that the system output pressure can be continuously adjusted by changing the duty ratio of the PWM signal supplied to the high-speed on–off valve. Although there is fluctuation on the output pressure, the system output pressure has a quasi-linear relationship with the PWM signal duty ratio. Results also show that the output pressure fluctuation is greatly influenced by the PWM signal frequency and the flywheel inertia. The hydraulic pressure converter based on high-speed on–off valves brings a new way to transform system pressure continuously.     

一种恒压输出的DC-DC升压电路设计

针对DC-DC升压器存在效率低,纹波电压较大,输出电压不稳定等问题,文中开发和设计了一种具有恒定输出电压的DC-DC升压转换器的方法。通过升压电路和电压反馈技术,将波动的输入电压变成恒定的直流电压输出。该设计通过将转换器的输出电压与参考电压相比较,两者的差值会产生一个PWM信号控制升压器的通断时间,从而达到恒定电压输出。仿真结果显示,该实验电路能在频率为20 kHz的连续导通模式中工作,产生24 V的恒定输出电压,输出功率为100 W。     

适合低压大电流直流输入的软开关局部PDM PWM高频DC-DC功率变换器

本文特别针对24V电池输入条件下的低电压、大电流特性，设计了一种新颖的PWM软开关DC-DC前向式功率变换器模型。在局部运行区域，利用了ZCS PWM DC-DC前向式功率变换器的附加控制模式来实现软开关。这种新型功率变换器在低负载条件下可支持PWM-PDM双模控制方式，研究结果证实，在ZCS和有功电压钳位开关条件下，基于PWM-PDM双模控制的软开关前向式功率变换器可在较大的负载范围内改善运行效率。     

应用于PWM降压DC-DC变换器的高性能误差放大器

提出了一种应用于PWM降压型DC-DC变换器的高性能误差放大器。该误差放大器采用反馈结构,具有较大的动态范围,并可消除噪声影响,从而显著减小了DC-DC电源的纹波电压。另外,采用该误差放大器还有效地减小了电源启动时间。文中提出的误差放大器电路及PWM控制芯片的其他电路模块采用2.0μmBipolar工艺实现。仿真结果表明,误差放大器的开环和闭环增益分别为61dB和33dB,GBW为200MHz,SR为0.64V/μs。芯片测试结果表明,在输出电压为3.3V,负载电流为0.2A时,输出纹波电压的峰-峰值小于25mV。     

A high-efficiency,low-noise power solution for a dual-channel GNSS RF receiver

A high-efficiency low-noise power solution for a dual-channel GNSS RF receiver is presented.The power solution involves a DC-DC buck converter and a followed low-dropout regulator(LDO).The pulsewidth -modulation(PWM) control method is adopted for better noise performance.An improved low-power highfrequency PWM control circuit is proposed,which halves the average quiescent current of the buck converter to 80μA by periodically shutting down the OTA.The size of the output stage has also been optimized to achieve high efficiency under a light load condition.In addition,a novel soft-start circuit based on a current limiter has been implemented to avoid inrush current.Fabricated with commercial 180-nm CMOS technology,the DC-DC converter achieves a peak efficiency of 93.1%under a 2 MHz working frequency.The whole receiver consumes only 20.2 mA from a 3.3 V power supply and has a noise figure of 2.5 dB.     

Technique for sensing inductor and DC output currents of PWM DC-DCconverter

The design, analysis and trade-offs of a novel method to sense the inductor and DC output currents of PWM converters are presented. By sensing and adding appropriately the currents in the transistor, rectifier and capacitors of a converter using current transformers, the waveforms of inductor and DC output currents can be reconstructed accurately while maintaining isolation. This method offers high bandwidth, clean waveform, practically zero power dissipation and simple circuit. The technique is applicable to all PWM converters in both continuous and discontinuous modes, and is most suitable for the implementation of current mode control schemes like hysteretic, PWM conductance control, and output current feedforward. This approach has been experimentally verified at a wide range of current levels, duty cycles, and switching frequencies up to 1.4 MHz     

PWM DC-DC变换器功率级的采样数据模型

将PWM变换器按其工作状态,分别写出开关导通和截止时的数学模型,根据其周其工作的特点,写出其非线性采样数据模型,将该方法用于变换器功率级的建模。以连续导通电压型DC-DC变换器为例,给出了PWM变换器功率级的一种非线性和线性化的采样数据模型,并推导了考虑到控制作用延迟时由控制到输出的传递函数,满足了控制器设计的需要。     

A PWM DC-DC converter with optimum segmented output stage and current detector

High efficiency is very important for DC-DC power supplies in portable applications. A PWM DC-DC converter with optimum segmented output stage is proposed in this paper whose efficiency at light load is improved. The segmented output stage is optimally divided into 5 small segments plus 4 big segments. The segmented number of the output stage can be adaptively regulated according to the load current. Moreover, two current detector circuits are simultaneously adopted to form a mixed load current sensor in the converter to improve the detecting accuracy. A segmented current SenseFET (SCS) is used to sense the load current in continuous current mode, and a time digital converter with digital judgement (TDC-D) is designed to detect the load current in discontinuous current mode. The structure of the proposed PWM converter with optimum segmented output stage and mixed load current detector circuits is described in this paper, which has been implemented in a 0.13 μm CMOS process. Simulation and testing results show that the output stages of the PWM converter can self transit from one segment stage to another segment stage according to the load condition. And the maximum efficiency improvement of the proposed converter can reach 15%.     

Adaptive duty ratio modulation technique in switching DC–DC converter operating in discontinuous conduction mode

Adaptive duty ratio (ADR) modulation technique in switching DC–DC converter operating in discontinuous conduction mode is proposed in this paper. The proposed ADR modulation technique can regulate the output voltage of the DC–DC converter by generating a series of duty ratios with very simple circuit architecture. The duty ratio is approximately proportional to the square root of the voltage difference between the regulated output voltage and the reference voltage at the beginning of the switching cycle at the light load. As a result, the proposed ADR modulation technique can achieve smaller ripple than the conventional pulse skip modulation over the whole load range. Moreover, the compromise between the light-load ripple and the output power range in the design stage in previous works is solved in the ADR modulation technique. Theoretical analysis, simulation and experimental results are presented to show the operation principle and the advantage of the proposed ADR modulation technique.     

峰值电流控制模式中的分段线性斜坡补偿技术

PWM反馈技术在现代DC-DC芯片中得到了广泛的应用,在此基础上讨论了PWM模式峰值电流控制中的斜坡补偿的意义,并结合峰值电流模控制方式,提出一种分段线性斜坡补偿方法,详细的介绍了分段线性斜坡补偿电路的设计思想,并且给出了最终设计电路。该电路提供的补偿信号在不同的占空比区间具有不同的斜率。电路基于Hynix0．5μm CMOS Standard Logic工艺设计,并经Hspice仿真验证达到设计目标。该斜坡补偿电路的优化设计避免了因过补偿而带来的系统瞬态响应慢和带载能力低等不良影响。     

On the periodic behavior of PWM DC-DC converters

In this paper, we present a method to compute the periodic behavior of PWM DC-DC converters. The method is based on Fourier series and can be seen as a generalization of the state space averaging techniques that are well-known in the field of DC-DC converters. The method of this paper can be used to compute the periodic behavior of a DC-DC converter up to any degree of accuracy. This can be done in open loop as well as in closed loop situations. In an open loop situation the method only requires the solving a set of linear equations in the Fourier coefficients. It is shown that the periodic behavior in an open loop situation always is stable. In a closed loop situation the method requires the solving of a set of equations consisting of the previously mentioned set of linear equations in the Fourier coefficients, combined with an additional nonlinear equation in the relative pulse width (duty ratio). In both situations the method of this paper can be implemented in an efficient way. The method is illustrated by means of known examples taken from the literature and is shown to be useful in establishing whether or not a periodic behavior in a closed loop situation is stable     

A novel maximum power point tracking technique for solar panels using a SEPIC or Cuk converter

A novel technique for efficiently extracting the maximum output power from a solar panel under varying meteorological conditions is presented. The methodology is based on connecting a pulse-width-modulated (PWM) DC/DC SEPIC or Cuk converter between a solar panel and a load or battery bus. The converter operates in discontinuous capacitor voltage mode whilst its input current is continuous. By modulating a small-signal sinusoidal perturbation into the duty cycle of the main switch and comparing the maximum variation in the input voltage and the voltage stress of the main switch, the maximum power point (MPP) of the panel can be located. The nominal duty cycle of the main switch in the converter is adjusted to a value, so that the input resistance of the converter is equal to the equivalent output resistance of the solar panel at the MPP. This approach ensures maximum power transfer under all conditions without using microprocessors for calculation. Detailed mathematical derivations of the MPP tracking technique are included. The tracking capability of the proposed technique has been verified experimentally with a 10-W solar panel at different insolation (incident solar radiation) levels and under large-signal insolation level changes.     

一种低噪高输出电压DC—DC变换器设计

针对某航天器设备用的130V高压DC—DC变换器的低噪声要求,采用初级侧隔离的负载端直接反馈控制方式,次级侧采用结合LC低通无源滤波电路和有源滤波电路的两级输出滤波电路设计方法。通过实验,不仅实现了高压DC—DC变换器的低噪声输出,而且通过优化设计,使得两级滤波器的体积较小,可靠性较高,实现了星载应用。     

Solar Energy System with Digital Controller for Grid Connected Systems

The solar photovoltaic (PV) module output voltage changes according to the variation of light intensity and temperature. This paper presents the implementation of an automatic digital controller of a DC-DC boost converter without batteries for a solar cell module by using a peripheral interface controller, which forms a closed loop, to control the ON-OFF period of the switching pulse. The output of DC-DC converter is maintained by automatically increasing or decreasing the pulse width. To produce the pulse width modulation (PWM), the microcontroller is programmed according to the required duty cycle for the power switch. The PWM ON period is increased with the decrease in the PV voltage and vice-versa. The input voltage to the inverter is maintained constantly and is converted into an AC signal by using the metal-oxide-semiconductor field effect transistor (MOSFET) H-bridge operated in the sinusoidal pulse width modulation mode by using a PIC (peripheral interface controller) microcontroller. The generated AC signal can be connected to the AC grid or to the AC load. The simulated results by using Proteus 8 and hardware implemented results verify the effectiveness of the proposed controller.