Output impedance

About: Output impedance is a research topic. Over the lifetime, 11185 publications have been published within this topic receiving 134949 citations.

Adaptive two-loop Voltage-mode control of DC-DC switching converters

Abstract: A new two-loop control scheme for voltage-mode control (VMC) of dc-dc switching converters is presented. The proposed method adds a high-gain robust loop with two controllers to the conventional VMC loop, achieving an analog "adaptive" loop in which the "equivalent voltage regulator" varies with the changing power stage parameters given as follows: 1) input voltage; 2) load; and 3) component tolerances. The loop significantly improves the disturbance rejection of the control system, i.e., closed-loop output impedance and audiosusceptibility while preserving the stability and the loop gain crossover frequency to a significant extent. Both the small-signal analysis and the experimental results carried out on a buck converter demonstrate the superiority of the proposed scheme with respect to the conventional single loop.

A Simple Control Method for High-Performance UPS Inverters Through Output-Impedance Reduction

Abstract: The purpose of a voltage controller for uninterruptible-power-supply inverters is to produce stable output voltage with low distortion under all loading conditions, particularly under nonlinear loads and load transients. Since the output impedance of the inverter is the source for tracking error caused by load current, this paper proposes a simple digital feedback controller that focuses on reducing the output impedance of inverters by a feedback of the load current. The proposed control strategy ensures high-quality steady-state and dynamic responses from the inverter system. The design of the proposed digital controller is simple and requires only a reasonably accurate knowledge of the output L-C filter parameters. In addition, only the output voltage and the load current are sensed if the dc link voltage is constant. The results of simulations and experiments show that the proposed controller can achieve very low total harmonic distortion and fast dynamic response under varied loads including nonlinear loads with low switching frequency.

High input impedance filters with low component spread using current-feedback amplifiers

Abstract: A new configuration for high input impedance bandpass, lowpass and highpass filters with low component spread using two current-feedback amplifiers is presented. It has the following features: orthogonal control of the natural frequency and quality factor by grounded resistors or capacitors, simple conversion into a voltage-controlled filter, minimum active components, low active and passive sensitivities, low component spread suitable for high-Q applications and low output impedance. Experimental results are given to demonstrate the feasibility of the proposed circuits. >

Modeling and Impedance Analysis of a Single DC Bus-Based Multiple-Source Multiple-Load Electrical Power System

Abstract: The impedance-based stability analysis method has been widely used to assess the stability of interconnected systems in more electric transportations. This paper deals with the source/load impedance analysis of the droop-controlled multiple-source multiple-load system, which is a promising candidate in the future more-electric aircraft. This paper develops a mathematical model of a permanent magnet synchronous generator-active front-end generation system, derives the output impedance of the source subsystem including converter dynamics, and shows the effect of parameter variations on the source and load impedance. A dynamic droop controller is proposed to provide active damping to the system. In addition, the impedance analysis is extended to a generalized single bus-based multiple-source multiple-load system in which power losses are also investigated. Finally, the analytical results obtained in this paper are confirmed by the experimental results.

Current sensing and current sharing

Abstract: An interleaved small-inductance buck voltage regulator (VRM) converter with the novel current sensing and sharing technology significantly improves transient response with size minimization. Specifically, two or more buck VRM modules are interleaved or connected in parallel. The resultant current waveform has a fast transient response but with reduced ripples since the ripples in the individual modules mathematically cancel one another. The result is a smooth output current waveform having spikes within an acceptable tolerance limits when for example the load increases due to a connected processor changing from “sleep” to “active” mode. A novel current sensing and sharing scheme between the individual VRMs is implemented using an RC network in each module to detect inductor current for that module. Good current sharing result can be easily achieved. Unlike peak current mode control and average current mode control, with this technology, the converter still has low output impedance and fast transient response. As a result, the VRM can be very cost-effective, high power density, high efficiency and have good transient performance.