Voltage regulator

This paper proposes the structured singular value () approach to the problem of designing an output voltage regulator for a Buck-Boost converter with current-mode control. This approach allows a quantitative description of the effects of reactive components' tolerances and operating point variations, which strongly affect the converter dynamics. At first, a suitable linear converter model is derived, whose parameter variations are described in terms of perturbations of the linear fractional transformation (LFT) class. Then,-analysis is used to evaluate the robustness of a conventional PI voltage regulator with respect to the modeled perturbations. Finally, the approximate-synthesis procedure known as D-K iteration is used to design a robustly performing regulator. Simulation results are presented, describing the small and large signal behavior of a reduced order approximation of the-synthesized controller. Index Terms-DC-DC power conversion, H-infinity control, H-infinity optimization, robustness, uncertain systems.

We present in this paper two new products for high-temperature, low-voltage (2.8V to 5.5V) power management applications. The first product is an original implementation of a monolithic low dropout regulator (XTR70010), able to deliver up to 1A at 230°C with less than 1V of dropout. This new voltage regulator can source an output current level up to 1.5A. The regulated output voltage can be selected among 32 preset values from 0.5V to 3.6V in steps of 100mV, or it can be obtained with a pair of external resistors. The circuit integrates complex analog and digital control blocks providing state of the art features such as UVLO protection, chip enable control, soft start-up and soft shut-down, hiccup short-circuit protection, customer selectable thermal shut-down, input power supply protection, output overshoot remover and stability over an extremely wide range of load capacitances. The circuit offers a fair ±2% absolute accuracy and is guaranteed latch-up free. The second product is ...

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This article deals with power supply linear and switching regulators commonly used in various applications for stabilizing an output voltage and ensuring a necessary power input to the load. It describes their basic parameters, performances, advantages, and disadvantages according to their topologies. We design a measurement chain for efficiency evaluation based on power monitors INA219 connected to an embedded system, Arduino UNO. Measurements were focused on evaluation linear regulators MA7805, LM317, switching regulators SZBK07, LM2575, SCW05B-05, and XH-M401. The resulting efficiency of linear and switching regulators was analyzed and errors in the measurement chain were evaluated. The second contribution is an innovative way of carrying out regulator noise estimation using a fast Allan variance method, focused on white noise and flicker noise (bias instability). The main contribution is employing a fast Allan variance method algorithm that dramatically decreases computation time by up to 11 s for 72 million measured (or generated) samples. It enables the analysis of large data sets of various physical quantities (for example, regulator output voltages).

In an ordinary (unregulated) power supply the voltage regulation is poor (i.e. the DC output voltage also changes due to variations in the input AC voltage). These variations in DC voltage may cause unreliable operation of electronic circuits; Therefore, regulated DC power supply is the only solution in such situations. In this paper, the V-I characteristics of a PN junction diode in both forward and reverse directions was investigated using Multisim 14.2, simulator and graphically discusses, the V-I characteristics of a Zener diode in both forward and reverse bias conditions and used it as voltage regulator was determined and discusses graphically, the effect of load resistance and filter capacitor on ripple factor of half wave was determined and discusses graphically, the effect of load resistance and filter capacitor on ripple factor full wave rectifiers was also determined and discusses graphically, finally a complete circuit of 8V DC regulated power supply with constant output voltage `irrespective of load variations was design using Zener diode as voltage regulator and simulated.

Clock multiplication is not possible with delay locked loops. However, ever increasing requirements for clock multiplication in analog integrated circuits has lead to the research in several avenues including ring oscillator and LC oscillator. Ring oscillators are typically used in clock multipliers of digital chips due to their smaller area, easier design, and larger frequency range compared to LC oscillators. However, ring oscillators typically exhibit much larger phase noise than their LC counterparts (for same power consumptions). This ...

The paper deals with an optimization procedure in terms of a network voltage parameters improvement. A software based approach is used to select optimal type of voltage regulator, its power and ideal location for application in a Low-Voltage (LV) test network, where it is required to enhance Voltage Quality (VQ). The test network presents a case where application of on-load tap changer transformer instead of conventional distribution transformer MV/LV is not adequate to maintain voltage profile in the LV system in limits. Therefore other type of voltage regulator has to be employed to increase VQ in the entire LV network. Principal measure for VQ evaluation there is adopted a Voltage Quality Index expressing the VQ level in dependence on selected and specified input parameters, which may be voltage magnitude, unbalance, harmonic distortion, flicker level and frequency. Within optimization process, maximal current carrying capacity of lines, network losses and cost of solutions are also taken into account.

In this article, the problem of voltage and frequency stability in a hybrid multi-area power system including renewable energy sources (RES) and electric vehicles has been investigated. Fractional order systems have been used to design innovative controllers for both load frequency control (LFC) and automatic voltage regulator (AVR) based on the combination of fractional order proportional-integral and proportional-integral-derivative plus double derivative (FOPI–PIDD2). Here, the dandelion optimizer (DO) algorithm is used to optimize the proposed FOPI–PIDD2 controller to stabilize the voltage and frequency of the system. Finally, the results of simulations performed on MATLAB/Simulink show fast, stable, and robust performance based on sensitivity analysis, as well as the superiority of the proposed optimal control strategy in damping frequency fluctuations and active power, exchanged between areas when faced with step changes in load, the changes in the generation rate of units, an...

Electric power comprises three basic fundamental components: generation, transmission and distribution system. Among these components, the distribution system plays a significant role in ensuring the reliable transmission of power to the load end. The distribution system is characterised by a large network structure that faces many challenges mainly due to the integration of distributed energy sources. As Distributed Generation offers environmental and economic benefits over centralised generation. Renewable energy sources are inherently distributed in nature and are the most important source for meeting future energy demands. Most generators in distributed generation are asynchronous and are affected by the problem of reactive power. They cannot produce reactive power but draw it from the power system. It can cause a voltage drop which is not acceptable for the customers due to the narrow operating range of voltages for appliances. From the last few years the power demand has increased due to increase in load requirements. The condition of power demand is not accompanied by only generation and transmission of electricity. Many industrial power plants are running on higher capacity to fulfil load requirements. There are many issues such as voltage instability and power quality which led to many power plants. In distributed generation generators are distributed asynchronous types and mostly affected by the reactive power. They basically cannot generate reactive power but draws away from the power system. It causes the voltage drop to the consumer side which may be not acceptable. With the penetration of renewable distributed generation and time-varying load connected to the distribution network, great challenges have appeared in the reactive power stability of the active distribution networks. Therefore reactive power management is essential for reducing those problems and provides continuity of electricity to the consumers. This problem can be overcome by using reactive power management techniques like distribution generation and distributed energy storage.

A computer algorithm .for optimal reactive power and voltage control, suitable fgr large distribution networks, is presented in this paper. The proposed algorithm starts with implementing a partitioning and Kron's reduction technique in order to reduce the size of the problem. The algorithm decouples the capacitor problems from the regulator problems and it use,: a dynamic programming technique to maximize the reduction in line losses in a real-time environment. The net outcomes of the algorithm are the capacitor bank locations, rating and switching scheme and location of voltage regulators, and tap settings that maximizes the loss reduction. The algorithm ensures that the voltage levels for all buses in the system are within permissible limits at all times. The algorithm is efficient, fast and reliable and can be easily implemented by any utility to optimize line loss reduction on distribution feeders.

An interleaving fixed switching frequency quasi-sliding control algorithm based on the Zero Average Dynamics (ZAD) approach is reported and applied to the design of a modular system of parallel-connected single-phase inverters. This approach is used in a laboratory prototype of three inverters with an FPGA control-based implementation embedding this algorithm. Experimental results are provided to illustrate the design features in terms of AC output voltage regulation, balanced current sharing among mismatched modules, interleaved fixed switching frequency operation and robustness with respect to load variations.

An interleaving fixed switching frequency quasi-sliding control algorithm based on the Zero Average Dynamics (ZAD) approach is reported and applied to the design of a modular system of parallel-connected single-phase inverters. This approach is used in a laboratory prototype of three inverters with an FPGA control-based implementation embedding this algorithm. Experimental results are provided to illustrate the design features in terms of AC output voltage regulation, balanced current sharing among mismatched modules, interleaved fixed switching frequency operation and robustness with respect to load variations.

Nowadays the H-bridge is one of the preferred solutions to connect DC loads or distributed sources to the singlephase grid. The control aims are: sinusoidal grid current with unity power factor and optimal DC voltage regulation capability. These objectives should be satisfied, regardless the conditions of the grid, the DC load/source and the converter nonlinearities. In this paper a passivity-based approach is thoroughly investigated proposing a damping-based solution for the error dynamics. Practical experiments with a real converter validate the analysis.

This paper is a study of the electrical device that can be able to sort out the problems of power fluctuation and improve the power quality by using servo mechanisms and comparison between relay and servo type voltage stabilizer. The servo voltage controlled stabilizers can be used in home as well as industries for stability and better voltage regulation and protects it from electrical hazard. The Indian power sector is one of the most diversified in the world. The demand for electricity in the country is growing at a rapid rate. The Indian power sector faces the problem in providing the stable power supply, and it creates the gap between the supply of power and its demand. This may cause heavy financial losses and also losses of industrial equipment. So, to obtain the stability and to overcome from power fluctuation, servo voltage stabilizer is required to be installed. Need of servo voltage stabilizer is increasing with the rise of demand of electrical and electronics devices in t...

The Use of FACTS Options to Permit Utilization of the Full Thermal Capacity of AC Transmission Long distance transmission of electric power permits serving loads with lower cost energy than may be available locally. For such economic reasons, most if not all of the world's electric power supply !systems are widely .interconnected, involving interconnections inside utilities' own territories. These interconnections extend to inter-utility and then to interregional connections. Due to a variety of environmental, land-use and regulatory pressures, the growth of electric power transmission facilities in many parts of the world is restricted, even though bulk power transfers and access by third parties are on the increase. The result is transmission bottlenecks, non-uniform utilization of facilities and unwanted parallelpath or loop flows. Often as power transfers grow, the power system beco:mes increasingly more complex to operate, and the system can become more insecure with large power flows with inadequate control. Th.e other aspect of the problem then becomes the inability to utilize the full potential of tran~mis~sion interconnections. With this in mind, the Electric Power Research Institute (EPRI), representing the collaborative research and development arm of the utility industries in the US, is supporting the development of FACTS (Flexible AC Transmi:ssion System) technologies. It has been discussed through publications , in speeches at IEEE meetings, forums, workshops, CIGRE, various utilities and most recently at a highly successful International Conferer~ce in Cincinnati in September 1990, organized by EPRI. The

A low leakage voltage pulse generator as needed in in I V small non-volatile memories for RFID applications is presented. vin in out o The voltage regulation loop is based on a capacitive divider which Charge pump v di, ad saves the static current usually consumed in a conventional pulse enable + e co generator based on a resistor divider. The proposed generator has been used in a 64bytes flash _ memory embedded in a RFID IC fabricated in a 0.22,u CMOS si lo 0d load process. Experimental results confirming the effectivness of the proposed generator are reported.

Testing is one of the crucial activities of software development life cycle which ensures the delivery of high quality product. As software testing consumes significant amount of resources so, if, instead of all software modules, only those are thoroughly tested which are likely to be defective then a high quality software can be delivered at lower cost. Software defect prediction, which has now become an essential part of software testing, can achieve this goal. This research presents a framework for software defect prediction by using feature selection and ensemble learning techniques. The framework consists of four stages: 1) Dataset Selection, 2) Pre Processing, 3) Classification, and 4) Reflection of Results. The framework is implemented on six publically available Cleaned NASA MDP datasets and performance is reflected by using various measures including: F-measure, Accuracy, MCC and ROC. First the performance of all search methods within the framework on each dataset is compared with each other and the method with highest score in each performance measure is identified. Secondly, the results of proposed framework with all search methods are compared with the results of 10 well-known supervised classification techniques. The results reflect that the proposed framework outperformed all of other classification techniques.

This paper addresses the closed-loop rampcomparison current regulation in an induction machine fed by a pulse width modulated voltage source inverter. The regulator is implemented in a synchronous frame, serving as a foundation for an overarching vector control of the induction machine. First, the effect of PI regulator gains on the controller performance is analyzed both theoretically and numerically using the developed Simulink model of the system. Next, the paper deals with highspeed and/or low-voltage operating conditions of the machine, introducing the concept of overmodulation and analyzing its impact on the regulator performance. Obtained simulation results coincide with model-based theoretical predictions and literature findings. Finally, the work proposes an outlook for the high-speed system enhancements in terms of power electronics topology, control and modulation.

Adjustable shunt regulators known as TL431 are extensively used to build the control systems in switched-mode converter applications. The resulting control system is typically a two-loop system, where one loop defines the low frequency behavior, and the other loop the higher frequency behavior, respectively. The shunt regulator is regarded to possess characteristics similar to an operational amplifier, even if it is basically a transconductance amplifier having current as an output signal instead of voltage as well as positive feedback instead of negative feedback. The small-signal response of a shunt regulator shows that it may be modeled as a voltage-controlled current source with a small transconductance gain and an equivalent capacitor as output impedance, which may be extracted from the open-loop frequency response by inspection. The variance in the parameters may be high depending on the manufacture, and operating point, i.e., cathode current, which is normally chosen to be close to 1 mA due to the specifications. The analysis shows, however, that the cathode current should be at least 5 mA for stable equivalent circuit parameters. If low cathode current is used, the control system may not be better than a Zener diode replacing the shunt regulator.

This paper describes the design of mixed-signal back end for an ultrahigh-frequency sensor-enabled radio-frequency identification transponder in full compliance with the Electronic Product Code Class-1 Generation-2 protocol, defined in the standard ISO 18000-6C. The chip, implemented in a low-cost 0.35-µm CMOS technology process, includes a baseband processor, an analog-to-digital converter (ADC) to digitize the signal acquired from the external sensor, and some auxiliary circuitry for voltage regulation and reference generation. The proposed solution uses two different supply voltages, one for the processor and the other for the mixed-signal circuitry, and defines a novel communication protocol between both blocks so that analog readouts are minimally affected by the digital activity of the tag. The whole system was first functionally validated by exhaustively testing with external dc power supplies ten prototype samples, and then, the two main blocks, processor, and ADC were individually tested to assess their performance limits. Regarding the baseband processor, experiments were performed toward the calculation of its packet error rate (PER) under two typical biasing configurations of passive tags, using either crude clamps or regulators. It was found that the regulated biasing outperforms the clamping solution and obtains a PER of 3 × 10 −3 with a supply voltage of 0.75 V. The current consumption of the processor during the reception and response to a Read command at maximum backward rate is only 2.2 µA from a 0.9-V supply. Regarding the ADC, it is a 10-b successive approximation register converter which obtains 9.41 b of effective resolution at 2-kS/s sampling frequency with a power consumption of 250 nW, including the dissipation of a current generation cell and the clock generation circuitry, from 1-V supply.

Regulation of load voltage in single-phase applications is becoming an important issue for critical loads. This paper proposes a method to regulate a single-phase ac source by using a series-connected auxiliary voltage source. A voltage source inverter, connected in series with the ac supply through a transformer, is used to compensate the input voltage variations to achieve a regulated load voltage. Input power factor improvement can also be obtained, when operating with reactive load, by phase-shifting the compensating voltage with respect to the input voltage. The operation of the compensator in all four quadrants allows the compensation of any voltage drop, and not only the reactive voltage drop within the same path. The total kVA rating for the system is a fraction of the load total power, and is determined by the maximum allowable line voltage variations. The use of a series connection associated with a high-performance modulation technique results in a high-quality output with a small size filter. This paper includes a description of the proposed method, implementation principles, design equations, and a design example. Steady-state performance features are investigated. Simulated and experimental results confirm the concept and feasibility of the proposed system. Index Terms-Power factor correction, series voltage regulator, single phase. I. INTRODUCTION EQUIREMENTS on the power quality of ac sources R are becoming more stringent as more voltage-sensitive equipment, such as computer systems and biomedical instrumentation, are being used. This results in a greater demand for high-quality voltage sources, increasing concerns about harmonic content, voltage balance, noise, and voltage stability in electrical supply systems. Voltage regulation and stability in ac sources are most commonly obtained by using phase-controlled ac-ac converters. The line voltage is increased by means of a transformer and its output voltage is then reduced by a line-commutated ac controller to obtain a regulated load voltage. As a result of the cycle-by-cycle control scheme, the harmonic content of Paper IPCSD 96-36, approved by the Industrial Power Converter Committee of the IEEE Industry Applications Society for presentation at the

Voltage unbalance typically present in three-phase ac supply systems adversely affects power system components, static converters, drive systems, electric machines, etc., connected to the system. This paper describes a method to eliminate this unbalance by means of a voltage compensator connected in series with the supply through transformers. The technique is based on extracting the negative sequence voltage component of the supply and cancelling it in order to obtain balanced voltages. The positive sequence component is then adjusted to achieve voltage regulation. It is shown that the compensation can be achieved with low kilovolt-ampere inverters and that harmonic injection is reduced to a minimum. This paper also includes implementation principles, design equations, and a design example. Simulated and experimental results confirm the theoretical concept and feasibility of the proposed system.

A distributed generation network could be a hybrid power system that includes wind–diesel power generation based on induction generators (IGs) and synchronous generators (SGs). The main advantage of these systems is the possibility of using renewable energy in their structures. The most important challenge is to design the voltage-control loop with the frequency-control loop to obtain optimal responses for voltage and frequency deviations. In this work, the voltage-control loop is designed by an automatic voltage regulator. A linear model of the hybrid system has also been developed with coordinated voltage and frequency control. Dynamic frequency response and voltage deviations are compared for different load disturbances and different reactive loads. The gains of the SG and the static volt-ampere reactive compensator (SVC) controllers in the IG terminal are calculated using the Black Widow Optimization (BWO) algorithm to insure low frequency and voltage deviations. The BWO optimiz...

The ever-changing use of electrical energy can affect the generator terminal voltage, this condition can result in a decrease in the reliability of the generator system. To maintain the reliability of the generator system, it is necessary to install a device capable of regulating the size of the terminal voltage or commonly called an auto voltage regulator (AVR). In this research, an AVR with Fuzzy Logic Control (FLC) method has been created which is able to regulate the generator terminal voltage. The results showed that the generator response with a 220V reference has a delay time = 0.45 s, rise time = 0.72 s, settling time = 1.15 s with a very small steady state error. AVR is able to improve the terminal voltage within ± 8 s when the generator is given a resistive load, and ± 6 s when the generator is given an inductive and capacitive load.

Nowadays, several test systems available in the specialized literature are used to verify studies regarding power system planning or network reliability. However, there are no test systems currently available with enough information in order to endorse studies that simultaneously approach expansion planning, operation, and reliability issues. This paper introduces a real test system, including the load modeling, and generation and transmission systems. The main objective is to provide all the details and information required to evaluate methods and models developed for power system planning, operation, and reliability. The presented load modeling includes hourly, daily, weekly, monthly, and seasonal patterns. Furthermore, besides the substation data, reliability details, construction costs, and characteristics of right of ways (e.g., line length, impedance, and ratings) for the transmission system are exposed. The real transmission system presented contains 39 buses, 135 transformers, and 66 lines at two voltage levels: 230 and 400 kV. Finally, the generation system reliability data as well as operation and installation costs for each unit are also provided.

This paper emphasizes the security and economy aspects of reac¬ tive power scheduling Thus two objective functions have been implemented in an automatic optimization procedure suitable for large scale systems too The choice of the more appropriate objec¬ tive is based on the structure of the system and on the load levels

An active filter-based on-chip DC-DC voltage converter for application to distributed on-chip power supplies in multivoltage systems is described in this paper. No inductor or output capacitor is required in the proposed converter. The area of the voltage converter is therefore significantly less than that of a conventional low-dropout (LDO) regulator. Hence, the proposed circuit is appropriate for point-of-load voltage regulation for noise sensitive portions of an integrated circuit. The performance of the circuit has been verified with Cadence Spectre simulations and fabricated with a commercial 110 nm complimentary metal oxide semiconductor (CMOS) technology. The area of the voltage regulator is 0.015 mm2 and delivers up to 80 mA of output current. The transient response with no output capacitor ranges from 72 to 192 ns. The parameter sensitivity of the active filter is also described. The advantages and disadvantages of the active filter-based, conventional switching, linear, and switched capacitor voltage converters are compared. The proposed circuit is an alternative to classical LDO voltage regulators, providing a means for distributing multiple local power supplies across an integrated circuit while maintaining high current efficiency and fast response time within a small area.

In electrical distribution networks, inefficiencies and instabilities often arise from inductive loads like motors and transformers, which exhibit a lagging power factor. This reduces system capacity, increases losses, and can lead to lower voltage levels. To address these issues, integrating parallel capacitors proves effective, enhancing the power factor, improving voltage profiles, and reducing overall system losses and costs. This research explores the optimal placement of parallel capacitors within a distribution network to manage reactive power effectively, thereby minimizing losses and improving voltage stability and system efficiency. Utilizing DigSILENT Power Factory and MATLAB, a genetic algorithm optimizes the location and sizing of capacitors in a 33-bus distribution network, considering scenarios with and without distributed generation (DG) and the impact of harmonic currents. The study finds that incorrect sizing or placement of capacitors can worsen voltage deviations when higher harmonic levels are present. However, the optimization method accurately determines the best parameters for capacitor installation, ensuring compliance with voltage and harmonic constraints. Deploying more than three to four capacitors does not significantly affect outcomes, while a single busbar capacitor often fails to meet operational standards. In conclusion, strategic capacitor placement and sizing can significantly reduce losses, enhance voltage stability, and mitigate inefficiencies caused by inductive loads. Attention to harmonics is crucial to avoid negative impacts on the network. This approach offers a replicable framework for similar optimizations in other distribution systems, advancing smart grid technology implementation.

This article aims to design a linear quadratic regulator (LQR)-based optimal current controller along with a Luenberger observer model in order to enhance power quality during the grid's dynamic conditions. To analyze the performance of the proposed control scheme, a three-phase photovoltaic-based gird-tied inverter is considered. A grid controller comprises a DC-link voltage controller to stabilize the capacitor voltage and a current controller to assure the output currents are well controlled according to the dynamic conditions of the grid as well as the source. In general, the capacitor-voltage and current controllers are regulated by traditional proportional Integral (PI) controllers which is associated with many demerits. In this work, a predictive LQRbased current controller with an observer algorithm and an adaptive capacitor voltage controller is proposed to improve the performance of the power grid at various dynamic conditions. The mathematical analogy is evaluated using MATLAB/SIMULINK software with different load and grid-disturbance conditions. Moreover, a laboratory prototype is designed to validate the simulation results. The outcomes prove that the proposed controller is dynamically robust to tackle any disturbance in load and grid.

An object-oriented simulation-in-the-loop C-written tool for power electronic apparatus in a dual (ac and dc) voltage prototype railway locomotive is proposed. By considering also the hardware elements of the control board, the simulator structure ensures the straightforward portability of the control codes from simulation to implementation, thus allowing to check the control algorithms and codes via realistic numerical tests. Each component of the locomotive is modeled as an object, by using state space dynamic models for the dynamic subsystems. The two line-side converter configurations, the field oriented controlled induction motors with Kalman filter as flux estimator and the space-vector modulated voltage source inverters are considered as examples. A new control strategy for the line-side converter ensuring voltage regulation and harmonic active filtering is also proposed and simulations show the effectiveness of the controller. The digital implementation of the control algorithms on an electronic control unit equipped with a DSP and a microcontroller is detailed, showing the time relationship between the control board tasks and the converters switching functions.

Thyristor controlled rectifier substations (TCRS) accomplish energy management objectives by controlling load flow. Voltage sources connected in parallel to a common grid share load dynamically in a complex relationship between the DC output voltage sources at fixed traction power substation locations and time variant loads at moving vehicle locations. Conventional diode rectifier sources with inherent voltage regulation produce a load

The transient stabilization and voltage regulation problem for a synchronous generator connected to an infinite bus is addressed, in this technical note, in the presence of all uncertain physical parameters. First, new interpretations for the Desensitized Four Loops Regulator, here referred to as robust coordinated PSS-AVR (Power System Stabilizer & Automatic Voltage Regulator), are derived in terms of minimum phase properties with respect to a suitably chosen output for the linearized error system. Secondly, on the basis of such an output, a nonlinear generalization of the robust coordinated PSS-AVR is designed with the aim of enlarging the stability region and improving the transients about the unpredictable operating conditions determined by the faults. Its linear action coincides with the one provided by the robust coordinated PSS-AVR: the compelling simplicity of control structure (just one integrator is involved) and robust tuning procedure of the linear design are definitely inherited, with, additionally, no use of the mechanical input power. A numerical analysis along with realistic simulations confirm improved stability when the proposed nonlinear controller is applied.

The paper describes a switching regulator system for adaptive voltage scaling (AVS) where the supply voltage to a digital VLSI chip is dynamically adjusted to the minimum value required for the desired system speed. The control loop includes a variable-frequency Watkins-Johnson switching DC-DC converter and a model of the critical path delay of the application. Simple bang-bang control of the critical path delay allows fast transient response to step changes in speed, and stable operation over a very wide range of system clock frequencies. A chip including the AVS controller and a small digital application has been fabricated in a standard CMOS process. Experimental results demonstrate operation over the application clock frequency range from 10 kHz to 20 MHz, and a 12 ¢ s transient response for a step change in speed from standby to maximum throughput operation.