Accurate Voltage Reference Research Articles

Distributed observer-based resilient control of islanded DC microgrids under actuator faults

In this paper, a distributed observer-based resilient control scheme is proposed to solve the voltage regulation and current sharing problems of islanded direct current (DC) microgrids under actuator faults. First, an observer-based distributed fault estimation design is presented to estimate fault signals with high accuracy. Then, based on the estimated information, a primary decentralized fault-tolerant control layer is designed to ensure accurate voltage reference tracking. A secondary cooperative control layer is employed to achieve the goal of current sharing. Besides, both the fault estimation observers and the fault-tolerant controllers are designed in a plug-and-play fashion, which guarantees the scalability of the DC microgrid. The simulation and experimental results show that the proposed control strategy can efficiently improve the reliability and resilience of the DC microgrid.

Dual-mode auto-calibrating resistance thermometer: A novel approach with Johnson noise thermometry.

A dual-mode auto-calibrating resistance thermometer (DART) is presented. The novel DART concept combines in one instrument the fast and accurate resistance thermometry with the primary method of Johnson noise thermometry. Unlike previous approaches, the new thermometer measures the spectral density of the thermal noise in the sensing resistor directly in a sequential measurement procedure without using correlation techniques. A sophisticated data analysis corrects the thermometer output for both the parasitic effects of the sensor wiring and the amplifier current noise. The instrument features a highly linear low-noise DC coupled amplifier with negative feedback as well as an accurate voltage reference and reference resistor to improve the gain stability over time and ambient temperature. Therefore, the system needs only infrequent calibrations with electrical quantum standards and can be operated over long intervals and a wide temperature range without recalibration. A first prototype is designed for the industrially relevant temperature range of the IEC 60751 (-200 °C to +850 °C); a later extension of the measurement range is being considered. A proof-of-principle measurement with a calibrated Pt100 sensor at room temperature yielded an uncertainty of about 100 µK/K. The final device is expected to reach uncertainties of below 10 µK/K, suitable for accurate measurements of the difference between thermodynamic temperatures and temperatures traceable to the International Temperature Scale of 1990 (ITS-90).

A Highly Robust Interface Circuit for Resistive Sensors

The signal from a resistive sensor must be converted into a digital signal to be compatible with a computer through an interface circuit. Resistance-to-Period converter, used as interface, is preferred if the resistance variations are very large. This paper presents the structure of an interface circuit for resistive sensors that is highly robust to component and power supply variations. Robustness is achieved by using the ratiometric approach, thus complex circuits or highly accurate voltage references are not necessary. To validate the proposed approach, a prototype was implemented using discrete components. Measurements were carried out considering a variation of ±35% in the single supply voltage and a range from 1 k Ω to 1 M Ω .

A CMOS Readout Circuit for Resistive Transducers Based on Algorithmic Resistance and Power Measurement

This paper reports a readout circuit capable of accurately measuring not only the resistance of a resistive transducer, but also the power dissipated in it, which is a critical parameter in thermal flow sensors or thermal-conductivity sensors. A front-end circuit, integrated in a standard CMOS technology, sets the voltage drop across the transducer, and senses the resulting current via an on-chip reference resistor. The voltages across the transducer and the reference resistor are digitized by a time-multiplexed high-resolution analog-to-digital converter (ADC) and post-processed to calculate resistance and power dissipation. To obtain accurate resistance and power readings, a voltage reference and a temperature-compensated reference resistor are required. An accurate voltage reference is constructed algorithmically, without relying on precision analog signal processing, by using the ADC to successively digitize the base–emitter voltages of an on-chip bipolar transistor biased at several different current levels, and then combining the results to obtain the equivalent of a precision curvature-corrected bandgap reference with a temperature coefficient of 18 ppm/°C, which is close to the state-of-the-art. We show that the same ADC readings can be used to determine die temperature, with an absolute inaccuracy of ±0.25 °C (5 samples, min–max) after a 1-point trim. This information is used to compensate for the temperature dependence of the on-chip polysilicon reference resistor, effectively providing a temperature-compensated resistance reference. With this approach, the resistance and power dissipation of a 100 $\Omega $ transducer have been measured with an inaccuracy of less than $\pm 0.55~\Omega $ and ±0.8%, respectively, from −40 °C to 125 °C.

Temperature sensors and voltage references implemented in CMOS technology

This paper reviews the concepts, opportunities and limitations of temperature sensors and voltage references realized in CMOS technology. It is shown that bipolar substrate transis- tors are very suited to be applied to generate the basic and PTAT voltages. Furthermore, it is shown that dynamic element matching and auto-calibration can solve the problems related to mismatching of components and noise. The effects of mechan- ical stress are a major source of inaccuracy. In CMOS technology, the mechanical-stress effects are small, as compared to those in bipolar technology. It is concluded that, with low-cost CMOS tech- nolog, rather accurate voltage references and temperature sensors can be realized.

Accurate low power bandgap voltage reference in0.5 µm CMOS technology

In mixed level applications, accurate voltage references are difficult to realise due to the lack of lateral p-n-ps and the large offsets inherent to CMOS opamps. If low power is essential, the accuracy is mainly impaired by the increased offset of the opamps. It is shown that by using chopping techniques, the accuracy of a bandgap voltage reference can be improved by about ten times without laser trimming, with the added benefit of reducing the 1/f noise of the amplifier.

An Integrating Analog-to-Digital Converter for Differential Transducers

An improved dual-slope analog-to-digital converter for measurements made with a pair of resistive or capacitive differential transducers is described. The converter can be contrasted with the conventional method in which the transducers are placed in a bridge, the bridge output is amplified, and the conversion is made. In the new converter the transducers are part of the integrator. As a result, conversion of the signal to a time interval takes place at an earlier stage, eliminating the bridge and the amplifier. The method has the same advantages as the dual-slope method and several additional ones. The fractional change in the transducers is obtained as the ratio of the difference and sum of two time periods. As a result, the converter does not need an accurate voltage reference. In addition, errors due to offset in the integrating amplifier are eliminated.

The Zener diode—an accurate voltage-reference source

The success or failure of many current Earth-satellite and space-exploration programmes is highly dependent on the performance of precision Zener diodes. Military and industrial users of these subminiature semiconductor devices are inheriting the benefits of the necessary applied technology.

Accurate voltage reference systems

Abstract This article briefly surveys the various batteries and other electrical devices which are now available for use as accurate direct voltage references. Some information on their performance when subject to fairly severe mechanical vibration, is given, and a new temperature controlled voltage reference source using Zener diodes and germanium junction transistors is described.