J.A. Abu Qahouq

Adaptive Step Size With Adaptive-Perturbation-Frequency Digital MPPT Controller for a Single-Sensor Photovoltaic Solar System

This paper presents a load-current-based maximum power point tracking (MPPT) digital controller with an adaptive-step-size and adaptive-perturbation-frequency algorithm. Only one sensor is needed in the controller circuitry since the MPPT controller is only utilizing the load current information. By utilizing a variable step-size algorithm, the speed, accuracy, and efficiency of the PV system MPPT are improved when compared to the fixed step-size load-current-based algorithm. Furthermore, the proposed adaptive algorithm utilizes a novel variable perturbation frequency scheme which further improves the controller speed. The concept and operation of the load-current adaptive-step-size and adaptive-perturbation-frequency MPPT controller are presented, analyzed, and verified by results obtained from a proof-of-concept experimental prototype.

Power Converter With Digital Sensorless Adaptive Voltage Positioning Control Scheme

A digital sensorless adaptive voltage positioning (SLAVP) control method is presented in this paper in order to realize AVP control without the need for load or inductor current sensing and high-resolution high-speed analog-to-digital converter sampling. The SLAVP control law utilizes the readily available error signal of the conventional voltage-mode closed-loop compensated controller or, in other words, the duty cycle of a dc-dc buck converter in order to realize AVP control. The elimination of the need for high-speed and accurate sensing and sampling of currents using the proposed SLAVP control reduces the size and cost of the digital controller, reduces the power losses associated with current sensing and sampling, and simplifies hardware design. Moreover, the SLAVP control can easily be added to controllers with conventional voltage-mode closed-loop control with minimum size and cost increase, and therefore, SLAVP control can be used for a wide range of applications and not only for high-end applications like powering microprocessors. The theoretical SLAVP control law derivation and analysis and SLAVP controller architecture are presented in this paper and verified by experimental results obtained from a proof-of-concept experimental prototype.

Online Closed-Loop Autotuning Digital Controller for Switching Power Converters

A switching power-converter closed-loop online autotuning controller is presented in this paper. The presented controller is based on tuning the closed-loop-compensator parameters by simply observing the compensated-error-signal time-domain characteristics. Moreover, the presented online autotuning controller does not require the knowledge of the power-stage frequency response, does not depend on any conventional rule-of-thumb control-design criteria such as gain and phase margins, can be used without interrupting the normal operation of the power converter, and is relatively simple when compared to other methods particularly those that require measuring the frequency response of the power stage or closed-loop converter system. The online autotuning controller is presented in this paper based on a dc-dc buck switching converter with a fully digital closed-loop controller, as an example and not for limitation.

Efficiency-Based Auto-Tuning of Current Sensing and Sharing Loops in Multiphase Converters

Multiphase converters require a current-sharing loop to maintain equal or desired current sharing between phases or paralleled modules. The current-sharing loop is highly sensitive to current-sensing accuracy. In this letter, a method is presented to achieve auto-tuning of the current-sharing loop in multiphase converters while adaptively calibrating the current sensing based on power conversion efficiency. This is achieved without the need for a precise calibration reference or resistor and with no dependency on sensing accuracy. A digital controller implementation of the method is described and experimental results are obtained for a 0.84 V/30 A two-phase buck voltage regulator.

Control Scheme for Sensorless Operation and Detection of CCM and DCM Operation Modes in Synchronous Switching Power Converters

Switching power converters with synchronous rectification utilize transitioning between inductors current continuous and discontinuous conduction operation modes (CCM and DCM) in order to achieve improved power efficiency across wide load and input voltage ranges. The inductor current zero crossing is sensed in order to detect the operation modes transition point between CCM and DCM. The challenges associated with this include inductor current zero crossing point sensing accuracy, noise effect near the zero crossing point, and the sensing circuitry speed and power loss. Moreover, additional hardware such as analog-to-digital converter is required if the controller used is a fully digital controller. In this letter, a control scheme for sensorless operation and detection of CCM and DCM in a switching power converter is presented. The presented controller utilizes dual control loops and does not require sensing the inductor current or any current in the converter, which eliminates or reduces challenges associated with inductor current sensing for the zero point detection. The presented controller is discussed, and proof-of-concept experimental prototype results are presented.

Voltage regulator module with interleaved synchronous buck converters and novel voltage-mode hysteretic control

Todays on-board low-voltage, high-current DC-DC voltage regulator module (VRM) requirements for the new generation of ICs and microprocessors are increasingly becoming stricter than ever, as the demand for high dynamic performance and high power density converters continues to increase. A new scheme that combines an interleaved technique and voltage-mode hysteretic control approach, by upgrading an existing single-phase chip, is proposed. It is expected that the new combined approach, with some design tradeoffs, will meet many of todays VRM requirements.

Adaptive step-size digital controller for switching frequency auto-tuning

A switching frequency auto-tuning digital controller for a power converter with adaptive step-size is presented in this paper. The controller automatically tracks and finds the switching frequency of a power converter in order to achieve highest power conversion efficiency under variable conditions and load. The adaptive controller utilizes a proposed adaptive variable-step-size function to improve the convergence speed and convergences error. The auto-tuning controller with the proposed adaptive step-size function is discussed and verified in this paper.