一种快速瞬态响应Buck变换器设计

提出了一种基于锁相环锁频锁相ACOT控制模式的Buck变换器。该变换器具有快速瞬态响应的特点。分析发现,在负载阶跃时,传统ACOT控制模式Buck变换器受到最小关断时间和锁相环速度的限制,不能完全发挥其瞬态响应快的优势。设计了一种根据设定的开关频率可自适应调节环路参数的Buck变换器,它在较宽的开关频率下具有快速的瞬态响应特性。采用0.18 μm BCD工艺对提出的Buck变换器进行仿真验证。结果表明,负载电流从1 A跳变到5 A时,输出电压下冲恢复时间减小为1.68 μs。     

自适应开启时间的Buck型DC-DC控制器设计实现

设计了一种基于自适应开启时间(adaptive on-time, AOT)控制的Buck型DC-DC控制器电路,利用输入电压前馈和输出电压反馈技术来获得开启时间,并提出了一种充电电流补偿和充电时间超前电路,校正了开启时间的线性度.AOT控制保证了转换器在无需内部振荡器的条件下,工作于固定频率脉冲宽度调制模式,并改善了输出电压的纹波特性.AOT控制使系统在负载阶跃时能够连续开启最小关断时间的开关周期或连续关断,从而快速调节电感电流,极大地提高了系统的瞬态响应速度.自动跳跃式脉冲频率调制模式,有效地改善了轻负载下的转换效率.芯片采用UMC 0.6μm BCD工艺投片验证,并出了详细的测试结果.     

自适应开启时间的Buck型DC-DC控制器设计实现

设计了一种基于自适应开启时间(adaptive on-time, AOT)控制的Buck型DC-DC控制器电路,利用输入电压前馈和输出电压反馈技术来获得开启时间,并提出了一种充电电流补偿和充电时间超前电路,校正了开启时间的线性度.AOT控制保证了转换器在无需内部振荡器的条件下,工作于固定频率脉冲宽度调制模式,并改善了输出电压的纹波特性.AOT控制使系统在负载阶跃时能够连续开启最小关断时间的开关周期或连续关断,从而快速调节电感电流,极大地提高了系统的瞬态响应速度.自动跳跃式脉冲频率调制模式,有效地改善了轻负载下的转换效率.芯片采用UMC 0.6μm BCD工艺投片验证,并出了详细的测试结果.     

基于峰值电流模控制的浮动栅驱动电路

设计了一种基于峰值电流模控制的浮动栅驱动电路,包括浮动栅宽电路和浮动栅压电路。电感电流的峰值由误差放大器的输出电压决定,不需要额外的负载电流信息进行浮动栅控制。可以根据负载电流的大小自适应调节功率管的栅宽和栅压,使效率得到优化。仿真结果表明,在1 MHz开关频率、5 V输入、0.8 V输出的双N管Buck变换器中,采用浮动栅驱动控制的Buck变换器与普通的Buck变换器相比,在轻载情况下最多可达到10%的效率提升。     

一种用于同步Buck变换器的自适应反流检测电路

提出了一种用于同步整流Buck电路的自适应反流检测(AZCD)电路,能够有效限制Buck变换器在DCM模式下出现电感电流的倒灌现象,以实现低EMI和高能效。与传统反流检测电路不同,该电路能够在Buck变换器输出电压变化的情况下保证功率下管的关断准确性。在0.35 μm BCD工艺下,对该电路进行仿真验证。结果表明,在1 MHz开关频率、输出电压从1.5 V变化到3.5 V的情况下,Buck变换器中功率下管的关断误差可以控制在1 ns以内。此外,在负载电流从12.5 mA变化到50 mA的情况下,该AZCD电路可以使Buck变换器效率提升约1%。     

单周期控制开关电容DC-DC变换器

传统的开关电容DC-DC变换器通常采用PWM控制方法，以输出电压或者开关管的电流作为反馈信号来调节占空比，然而占空比信号的变化不能即时跟随输入电压或负载的变化，因而PWM控制方法的动态调节响应较慢。单周期控制方法是一种非线性控制技术，该技术利用开关变换器的非线性特点，对开关变量平均值实现即时的动态控制，只需在一个开关周期之内就能使开关变量平均值达到稳态，因而具有较快的响应速度。本文介绍了单周期控制方法的基本原理，并将该方法应用于一个恒定频率的升压(5V／12V)开关电容DC-DC变换器的控制．仿真结果轰明该方法是可行的。     

自适应开启时间Buck变换器定时器电路设计

设计了一种用于自适应开启时间(adaptive on-time,AOT)Buck型DC-DC变换器的定时器电路,采用了输入电压前馈补偿和输出反馈技术,使开关频率不随输入、输出电压变化,实现了固定频率的伪脉冲宽度调制。基于0.18μm BCD工艺进行电路设计,并使用Hspice仿真验证。仿真结果表明当输入电压从5~18 V,相同输出电压下开关频率变化不超过10 k Hz,不同的输出电压下系统开关频率变化不超过20 k Hz。同时,由于定时器中采用输入电压前馈技术,提高了输入线性瞬态响应速度。     

一种用于COT架构Buck变换器的导通定时器

针对恒定导通时间(COT)控制架构Buck变换器的开关频率随输入与输出电压变化较大的问题,在COT架构的基础上,引入输入电压前馈,使开关管导通时间与输入电压成反比,同时引入输出电压反馈,使开关管导通时间与输出电压成正比,从而使系统开关频率保持恒定,简化了输出滤波器的设计,减小了电磁干扰。Hspice软件仿真结果表明,导通时间随输入与输出电压的变化而变化,开关频率基本保持恒定。采用此结构的Buck变换器具有极佳的瞬态响应性能。     

基于多频脉冲序列控制Buck变换器的研究

针对开关变换器双频率控制技术存在的输出电压纹波大、输出功率范围窄等缺点,研究电压型多频率脉冲序列控制方法,该方法通过四组预设控制脉冲,实现开关变换器输出电压的调节。对多脉冲序列控制Buck变换器在电感电流连续导电模式（Continuous Conduction Mode,CCM）和电感电流断续导电模式（Discontinuous Conduction Mode,DCM）下的工作特性进行分析,重点研究了在DCM 模式下Buck变换器多频率控制。最后,分析了DCM Buck变换器工作在稳态时脉冲序列的组合方式,并通过实验验证了理论分析的正确性。     

一种用于RF供电的混合结构DC-DC变换器

设计了一种基于0.13 μm CMOS工艺的混合结构DC-DC变换器。该变换器由Buck变换器和LDO串联组成。Buck变换器输出电压可根据LDO负载电流进行调节,能有效减小LDO损耗。在负载电流为20 mA时,可将整个变换器的效率提高10.5%。LDO采用片外电容补偿。高带宽误差放大器使LDO在DC~20 MHz范围内具有较高的电源抑制比。LDO对Buck变换器开关频率处的噪声抑制达-62 dB。整个电源具有较低的输出噪声,适于为RF电路供电。     

High-accuracy current sensing circuit with current compensation technique for buck–boost converter

A novel on-chip current sensing circuit with current compensation technique suitable for buck–boost converter is presented in this article. The proposed technique can sense the full-range inductor current with high accuracy and high speed. It is mainly based on matched current mirror and does not require a large proportion of aspect ratio between the powerFET and the senseFET, thus it reduces the complexity of circuit design and the layout mismatch issue without decreasing the power efficiency. The circuit is fabricated with TSMC 0.25 µm 2P5M mixed-signal process. Simulation results show that the buck-boost converter can be operated at 200 kHz to 4 MHz switching frequency with an input voltage from 2.8 to 4.7 V. The output voltage is 3.6 V, and the maximum accuracy for both high and low side sensing current reaches 99% within the load current ranging from 200 to 600 mA.     

An automatic load-adaptive switching frequency selection technique for improving the light-load efficiency of a buck converter

A load-adaptive automatic switching frequency selection scheme is proposed to improve the power efficiency of a switching buck converter at light load condition. The buck converter operates in the continuous-conduction mode for heavy loading and the switching frequency is fixed at its maximum value. For light loading, the buck converter operates in the discontinuous-conduction mode and its switching frequency is automatically selected among a pre-defined set of frequencies according to the amount of the load current. The load current can be sensed indirectly by monitoring the on-time of power transistor because it is a function of the load current. With the proposed load-adaptive automatic switching frequency selection circuit, the power efficiency of a buck converter implemented in a 0.35-μm 2P4M BCDMOS technology is improved by 24.0-% when the load current load is 10-mA.     

Dynamic hysteresis band control of the buck converter with fast transient response

A dynamic hysteresis control of the buck converter for achieving high slew-rate response to disturbances is proposed. The hysteresis band is derived from the output capacitor current that predicts the output voltage magnitude after a hypothesized switching action. Four switching criteria are formulated to dictate the state of the main switch. The output voltage can revert to the steady state in two switching actions after a large-signal disturbance. The technique is verified with the experimental results of a 50 W buck converter.     

A Soft-Switched Full-Bridge Single-Stage AC-to-DC Converter With Low-Line-Current Harmonic Distortion

A single-phase high-frequency transformer-isolated soft-switching single-stage ac-to-dc converter with low-line-current distortion is presented. The circuit configuration is obtained by integrating two discontinuous current mode (DCM) boost converters with a DCM full-bridge buck converter. The zero-voltage switching for the top switches is achieved automatically, whereas bottom switches are aided by zero-voltage transition circuits. The output voltage is regulated by duty-cycle control at constant switching frequency. The intervals of operation and steady-state analysis are presented. A systematic design procedure is presented with a 1-kW converter design example. PSPICE simulation and experimental results obtained from a 1-kW laboratory prototype are presented for a wide variation in line and load conditions.     

An Accurate, Low-Voltage, CMOS Switching Power Supply With Adaptive On-Time Pulse-Frequency Modulation (PFM) Control

Integrated switching power supplies with multimode control are gaining popularity in state-of-the-art portable applications like cellular phones, personal digital assistants (PDAs), etc., because of their ability to adapt to various loading conditions and therefore achieve high efficiency over a wide load-current range, which is critical for extended battery life. Constant-frequency, pulsewidth modulated (PWM) switching converters, for instance, have poor light-load efficiencies because of higher switching losses while pulse-frequency modulation (PFM) control in discontinuous-conduction mode (DCM) is more efficient at light loads because the switching frequency and associated switching losses are scaled down with load current. This paper presents the design and integrated circuit prototype results of an 83% power efficient 0.5-V 50-mA CMOS PFM buck (step-down) dc-dc converter with a novel adaptive on-time scheme that generates a 27-mV output ripple voltage from a 1.4- to 4.2-V input supply (battery-compatible range). The output ripple voltage variation and steady-state accuracy of the proposed supply was 5 mV (22-27 mV) and 0.6% whereas its constant on-time counterpart was 45 mV (10-55 mV) and 3.6%, respectively. The proposed control scheme provides an accurate power supply while achieving 2%-10% higher power efficiency than conventional fixed on-time schemes with little circuit complexity added, which is critical during light-loading conditions, where quiescent current plays a pivotal role in determining efficiency and battery-life performance     

Fast-response single-inductor dual-output hysteresis-current-controlled DC–DC buck converter

A fast-response single-inductor dual-output hysteresis-current-controlled DC–DC buck is proposed for enhancing the transient characteristics of switching DC–DC converters and fabricated with TSMC 0.35 μm DPQM CMOS processes. By adopting a hysteresis-current-controlled DC–DC buck converter, it is demonstrated that the hysteresis-current-controlled technique have improved dynamic response of load variations whether the load current is light or heavy. Fast-response structure achieves 5 μs response with load variation which betweens 10 and 110 mA. Also proposed single-inductor dual-output structure is a time-multiplexing circuit to decrease the influence of cross regulation than that of previous designs. With a 3.6 V input power supply, the DC–DC buck converter precisely provides an adjustable power output with a voltage range from 0.9 to 3 V.     

A dual-mode fast-transient average-current-mode buck converter without slope-compensation

A dual-mode fast-transient average-current-mode buck converter without slope-compensation is proposed in this paper. The benefits of the average-current-mode are fast-transient response, simple compensation design, and no requirement for slope-compensation, furthermore, that minimizes some power management problems, such as EMI, size, design complexity, and cost. Average-current-mode control employs two loop control methods, an inner loop for current and an outer one for voltage. The proposed buck converter using the current-sensing and average-current-mode control techniques can be stable even if the duty cycle is greater than 50%. Also, adaptively switch between pulse-width modulation (PWM) and pulse-frequency modulation (PFM) is operated with high conversion efficiency. Under light load condition, the proposed buck converter enters PFM mode to decrease the output ripple. Even more, switching PWM mode realizes a smooth transition under heavy load condition. Therefore, PFM is used to improve the efficiency at light load. Dual-mode buck converter has high conversion efficiency over a wide load conditions. The proposed buck converter has been fabricated with TSMC 0.35 μm CMOS 2P4M processes, the total chip area is 1.45×1.11 mm². Maximum output current is 450 mA at the output voltage 1.8 V. When the supply voltage is 3.6 V, the output voltage can be 0.8-2.8 V. Maximum transient response is less than 10 μs. Finally, the theoretical analysis is verified to be correct by simulations and experiments.     

一种基于自适应峰值电流检测的模式切换电路北大核心

在降压转换器中，为了在不同的负载情况下获得高效率，常采用的方法是在重载时使用脉冲宽度调制(PWM),在轻载时使用脉冲频率调制(PFM),因此需要模式切换信号去控制整个降压转换器的工作状态，同时模式切换信号也可以用于自适应改变功率级电路中的功率管栅宽，减小功率管的栅极电容，提高整体电路的效率。文章设计了一个自适应峰值电流模式切换电路，用于产生模式切换信号，其原理是监控峰值电流的变化，产生峰值电压，将峰值电压与参考电压进行比较，得到模式切换信号，以决定降压转换器是采用PFM模式还是PWM模式。仿真结果表明，在负载电流0.5～500 mA范围内，该电路可以在两种调制模式之间平稳切换，其峰值效率可提升到94%以上。     

A voltage mode buck DC–DC converter with automatic PWM/PSM mode switching by detecting the transient inductor current

This paper presents a voltage mode buck DC–DC converter that integrates pulse-width modulation (PWM) and pulse-skipping modulation (PSM) to achieve high efficiency under heavy and light load conditions, respectively. Automatic mode-switching is implemented simply by detecting the voltage drop of high-side power switch when it is on, which indicates the transient current flowing through the inductor. Unlike other methods based on average current sensing, the proposed auto-mode switching scheme is implemented based on voltage comparison and simple control logic circuit. In order to avoid unstable mode switching near the load condition boundary, the mode switching threshold voltage is set differently in PWM and PSM mode. Besides, a 16-cycle counter is also used to ensure correct detection of the change in the load condition and fast response of the converter. In addition, a dual-path error amplifier with clamp circuit is also adopted to realize loop compensation and ensure 100 % duty cycle operation. Fabricated in a 0.18-μm standard CMOS technology, the DC–DC converter is able to operate under supply voltage from 2.8 to 5.5 V with 3-MHz clock frequency. Measurement results show that the converter achieves a peak efficiency of 93 %, and an output voltage ripple of less than 40 mV, while the chip area is 1.02 mm².