Large Equivalent Series Resistance Research Articles

Adaptive On-Time Buck Converter with Wave Tracking Reference Control for Output Regulation Accuracy

A ripple-based constant on-time (RBCOT) buck converter with a virtual inductor current ripple (VICR) control can relax the stability constraint of large equivalent series resistance (ESR) at an output capacitor, but output regulation accuracy deteriorates due to the issue with output DC offset. Thus, this paper proposes a wave tracking reference (WTR) control to improve converter stability with low ESR and concurrently eliminate output DC offset on the regulated output voltage. Moreover, an adaptive on-time (AOT) circuit is presented to suppress the switching frequency variation with load current changes in continuous conduction mode. A prototype chip was fabricated in 0.35 µm CMOS technology for validation. The measurement results demonstrate that the maximum output DC offset is 4.1 mV and the output voltage ripple is as small as 3 mV. Furthermore, the switching frequency variation with the AOT circuit is 11 kHz when load current changes from 50 mA to 500 mA, and the measured maximum efficiency is 90.9% for the maximum output power of 900 mW.

A 93.4% Efficiency 8-mV Offset Voltage Constant On-Time Buck Converter With an Offset Cancellation Technique

In this brief a constant on–time (COT) buck converter with high efficiency and low offset voltage is presented. It was fabricated with a TSMC $0.18{\mu }\text{m}$ 1P6M CMOS process. An additional current feedback path (ACFP) technique was incorporated to avoid subharmonic oscillation of the converter without a large equivalent series resistance (ESR) capacitor, thus reducing the output voltage ripple. However, the ACFP causes an offset voltage on the converter’s output voltage dc level with loading changes. The proposed offset cancellation can remove the dc level from current sensor in ACFP. Hence, the offset voltage can be reduced through a proposed offset cancellation technique. The experimental results revealed that the offset voltage of the proposed converter is 8mV under a 0.1A to 1A loading changes. The converter’s maximum power efficiency is 93.4 %, and its output voltage ripple is less than 18mV.

A Constant-on-Time Control DC–DC Buck Converter With the Pseudowave Tracking Technique for Regulation Accuracy and Load Transient Enhancement

Constant-on-time (COT) control with an additional current feedback path in conventional buck converters can remove the need of large equivalent series resistance (ESR) at the output capacitor but it induces degraded output voltage regulation accuracy and slow transient response owing to opposite reaction between the output voltage and the additional current feedback information. Therefore, this paper proposes the pseudowave tracking (PWT) technique to reduce the load-dependent dc offset voltage of output load regulation while keeping the fast transient response similar to conventional COT buck converter with large ESR. The PWT technique further improves the transient response instantly by extending on-time and off-time periods during light-to-heavy and heavy-to-light load changes, respectively. The test chip fabricated in 28 nm CMOS process has demonstrated the improvement of offset voltage from 42 to 4 mV, while the transient response can be improved to 4 and 5 μs with load changes from 0.3 to 1.7 A and vice versa, respectively.

Sampled-data modeling and dynamical effect of output-capacitor time-constant for valley voltage-mode controlled buck-boost converter**Project supported by the National Natural Science Foundation of China (Grant Nos. 61371033 and 51407054), the Foundation for the Author of National Excellent Doctoral Dissertation of China (Grant No. 201442), and the Fundamental Research Funds for the Central Universities of China (Grant No. 2682016CX035).

By analyzing the output voltage ripple of a buck-boost converter with large equivalent series resistance (ESR) of output capacitor, one valley voltage-mode controller for buck-boost converter is proposed. Considering the fact that the increasing and decreasing slopes of the inductor current are assumed to be constant during each switching cycle, an especial sampled-data model of valley voltage-mode controlled buck-boost converter is established. Based on this model, the dynamical effect of an output-capacitor time-constant on the valley voltage-mode controlled buck-boost converter is revealed and analyzed via the bifurcation diagrams, the movements of eigenvalues, the Lyapunov exponent spectra, the boundary equations, and the operating-state regions. It is found that with gradual reduction of output-capacitor time-constant, the buck-boost converter in continuous conduction mode (CCM) shows the evolutive dynamic behavior from period-1 to period-2, period-4, period-8, chaos, and invalid state. The stability boundary and the invalidated boundary are derived theoretically by stability analysis, where the stable state of valley voltage-mode controlled buck-boost converter can enter into an unstable state, and the converter can shift from the operation region to a forbidden region. These results verified by time-domain waveforms and phase portraits of both simulation and experiment indicate that the sampled-data model is correct and the time constant of the output capacitor is a critical factor for valley voltage-mode controlled buck-boost converter, which has a significant effect on the dynamics as well as control stability.

Study of the Aluminum Anode Oxide Film and Cathode Material Interface of Conductive Polymer Aluminum Solid Electrolytic Capacitor

Introduction In 1745, Lyden jar was invented by J.Sesaguliers and Peter Van Muchenbroek. In1855, It was discovered by Charles Weatstone capable of forming an insulating film on the surface of the electrode. (By this discovery, we can make the electrolytic capacitor.) Aluminum electrolytic capacitor, was made by GE, Inc in 1908. And about 1931, aluminum electrolytic capacitor has been commercialized in the United States. Current, aluminum electrolytic capacitor is used in a power supply and noise reduction and an inveter. Electrolytic capacitor has a large equivalent series resistance and electricity is wasted. So, having a small equivalent series resistance, conductive polymer aluminum solid electrolytic capacitors are in practical use. However, conductive polymer aluminum solid electrolytic capacitor, to the leakage current is larger, the withstand voltage is low. It is desirable that this drawback is eliminated. It should be made clear disadvantages mechanism. It seems to be difficult when using typical electrochemical cell. This study was carried out by devising the cell. Experiments, Results and Discussion The anode oxide film even if contaminated with carbon in a conductive polymer was repaired. As a result, the conductive polymer has been shown that increasing the insulating film of the anode oxide film. A conductive polymer aluminum solid electrolytic capacitors made of aluminum foil and a separator, as compared with the electrolytic solution cathode electrolysis capacitance, equivalent series resistance decreases. equivalent series resistance was reduced, especially 10kHz ~ 100kHz. Anodic aluminum after being anode oxidation, affixed a reinforcement seal. It was added dropwise to the electrolyte solution into the hole of the reinforcement label. Put the counter electrode and measured cyclic voltammetry without separator. This experiment shows, the anode oxide film showed it to be damaged by a separator.

A Fast-Transient Quasi-V$^{\bf 2}$ Switching Buck Regulator Using AOT Control With a Load Current Correction (LCC) Technique

A switching regulator with quasi-V2 adaptive on-time (AOT) control that provides a fast load transient response is proposed in this paper. The feed-forward path network allows the proposed switching regulator to achieve a fast transient response and stable operation without requiring an output capacitor with large equivalent series resistance. The proposed adaptive on-time controller makes the switching frequency pseudofixed in the continuous conduction mode and works in the pulse-frequency modulation mode under ultralight-load conditions to maintain the conversion efficiency. The AOT controller adjusts the on-time according to the supply voltage and load current conditions. The measurement results verify that the switching regulator can operate under load current between 5 and 800 mA for the supply voltage of 3.3-4.2 V and an output voltage of 1.2 V. The recovery time is 3.6 μs and the voltage drop is 75 mV when the load current is increased from 5 to 750 mA.

A transient‐improved low‐dropout regulator with nested flipped voltage follower structure

SUMMARYIn this article, the existing low‐dropout regulator (LDO) based on cascoded flipped voltage follower (CAFVF) is reviewed. A new method to simulate the open‐loop gain of an LDO with a CAFVF structure is conveyed. The drawback of CAFVF‐based LDO is that the nondominant pole locates at low‐frequency and pole‐zero cancellation using a large equivalent series resistance of loading capacitor is required for stability. To tackle this problem, a novel LDO structure based on a nested CAFVF is proposed and analyzed in this article. It is shown that the nondominant pole is pushed to a high frequency and the LDO stability is improved. The proposed circuit is fabricated using a commercial 0.35‐µm CMOS technology, and the load‐transient response between 0.5 and 60 mA settles at approximately 5 µs. Copyright © 2012 John Wiley & Sons, Ltd.