Time-multiplexing Control Research Articles

A Compact and High-Performance Acoustic Echo Canceller Neural Processor Using Grey Wolf Optimizer along with Least Mean Square Algorithms

Recently, the use of acoustic echo canceller (AEC) systems in portable devices has significantly increased. Therefore, the need for superior audio quality in resource-constrained devices opens new horizons in the creation of high-convergence speed adaptive algorithms and optimal digital designs. Nowadays, AEC systems mainly use the least mean square (LMS) algorithm, since its implementation in digital hardware architectures demands low area consumption. However, its performance in acoustic echo cancellation is limited. In addition, this algorithm presents local convergence optimization problems. Recently, new approaches, based on stochastic optimization algorithms, have emerged to increase the probability of encountering the global minimum. However, the simulation of these algorithms requires high-performance computational systems. As a consequence, these algorithms have only been conceived as theoretical approaches. Therefore, the creation of a low-complexity algorithm potentially allows the development of compact AEC hardware architectures. In this paper, we propose a new convex combination, based on grey wolf optimization and LMS algorithms, to save area and achieve high convergence speed by exploiting to the maximum the best features of each algorithm. In addition, the proposed convex combination algorithm shows superior tracking capabilities when compared with existing approaches. Furthermore, we present a new neuromorphic hardware architecture to simulate the proposed convex combination. Specifically, we present a customized time-multiplexing control scheme to dynamically vary the number of search agents. To demonstrate the high computational capabilities of this architecture, we performed exhaustive testing. In this way, we proved that it can be used in real-world acoustic echo cancellation scenarios.

Single-Inductor, Multiple-Input, Multiple-Output, DC-DC Converter Based on a New Software Zero-Current Switching (ZCS) Technique

A single-inductor multiple-input multiple-output converter is proposed in this paper that can be used in low-power systems due to low output current and voltage. This converter is implemented discretely, and only one microcontroller is employed to control the system. The unique zero-current switching (ZCS) technique considered in this paper is such that only by reading the inductor’s left-side voltage the optimal value of the inductor discharge duty cycle is determined. This method can be generalized to low-power and high-power converters, whether implemented and designed as discrete or integrated. This converter works in discontinuous conduction mode. It uses pulse width modulation control and the time-multiplexing control method, which makes the system have high efficiency and makes the cross-regulation problem between the converter’s outputs tiny. The control algorithm considered in this converter is digital, which determines the optimal charge and discharge duty cycles. Also, the switching frequency of this converter is constant, relatively low, and equal to 5[Formula: see text]kHz. The efficiency of this converter has reached 91.6% by using the ZCS technique and other mentioned control methods.

A Novel, Software-Defined Control Method Using Sparsely Activated Microcontroller for Low-Power, Multiple-Input, Single-Inductor, Multiple-Output DC–DC Converters to Increase Efficiency

This article proposes a novel control for the multiple-input, single-inductor, multiple-output dc–dc converters. It is digitally and discretely implemented, which can have an outstanding performance in low-power applications so that at the power of 10 mW, it has an efficiency of 92.5%. Conventionally, in this power range, an attempt is made to take advantage of an analog design that is flexible. Thus, a fully programmable (software designed) converter with digital design using a microcontroller is in great demand. This converter design basis is to deploy the microcontroller's central processing unit (CPU) as little as possible. Also, it only turns <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> the CPU when necessary to be employed in low-power, portable systems, e.g., energy-harvesting technologies. Therefore, construction costs are significantly reduced. Depending on the energy level of the inputs, they can simultaneously be utilized to charge the outputs. This article uses stability analysis, time-multiplexing control method, and variable-frequency pulsewidth modulation in the proposed control design. Each output can be charged with different frequencies according to its load, and the maximum switching frequency is equal to 10 kHz. Also, the proposed technique for zero-current switching has been digitally implemented; it can be utilized to determine the optimal value of the inductor discharge duty cycle based on the inductor's left-side voltage. Comparative simulations and experimental results reveal the superiority and practicality of the proposed approach.

A dynamic power control scheme for a standalone solar photovoltaic system using multiport DC–DC converter

ABSTRACT A technique, utilizing a single-stage, single inductor, a multiport DC–DC converter is proposed for dynamically controlling the power supplied to isolated loads by a set of solar PV panels. The double-input/output buck-boost (DIOBB) converter is used to feed the load from the PV panels and a bank of batteries. The converter can operate in various modes, depending on the availability of the power levels of the solar panels and the output voltage levels of the panels, and the DC load present on the system. The operation of the converter is described using pertinent analytical expressions. The proposed dynamic power control technique maintains power flow between the PV module, battery, and the load, by time multiplexing control and tracking the maximum power from the module. A hardware prototype of DIOBB converter and the control algorithm is programmed in the dSPACE DS1103 real time control board. The efficacy of the proposed dynamic power control technique has been validated by extensive experimentation carried out under different conditions of solar power availability and DC load voltage levels with the converter working efficiency of about 93% at full load condition.

SIMO DC-DC Converter with Low-Complexity Hybrid Comparator-Charge Control

A hybrid control method using a comparator and a charge control method is proposed for a single-inductor multiple-output (SIMO) DC-DC converter. SIMO DC-DC converters have the weaknesses relating to cross-regulation, as all the output channels share the energy stored in a single inductor. Although multiple control methods such as Time-Multiplexing Control (TMC) and Ordered Power Distributing Control (OPDC) have been proposed to prevent cross-regulation or to improve load capability, effective use of limited resources appears to have not yet been achieved. This paper introduces a hybrid control topology that (1) utilizes comparator-based regulations for most outputs and (2) uses a new charge control loop method for the last output to reduce cross-regulation with low hardware complexity. In addition, the proposed scheme efficiently reuses the system’s redundant energy by adaptively controlling the freewheeling switch that opens the path to the input battery to store the surplus energy resources again. The proposed SIMO DC-DC converter was designed and validated with a 0.18 μm 3.3 V CMOS process. The converter has four regulated outputs of 0.9, 1.2, 1.5, and 2.2 V, and as a result of the simulation, it was found that the cross-regulation was estimated to be 0.4 mV/mA when the output current changes by ~200 mA. In addition, estimated peak power conversion efficiency of 88.5% was achieved at a total output power of 405 mW.

A digital controller for single-inductor dual-output switching converter with low cross regulation

In this paper, motivated by improving the characters of the single-inductor dual-output switching converter (SIDO) at continuous-conduction mode (CCM), a new digital controller for converter is proposed. The digital controller mainly consists of the time-multiplexing control method and the predictive control method. The simulation results demonstrate that the converter with the proposed digital controller can aim high output stability and low cross regulation.

Multiple String LED Driver With Flexible and High-Performance PWM Dimming Control

The main objectives in driving multiple LED strings include achieving uniform current control and high performance PWM dimming for all strings. This work proposes a new multiple string LED driver to achieve not only current balance, but also flexible and wide range PWM dimming ratio for each string. A compact single-inductor multiple-output topology is adopted in the driver, accompanied by synchronous integrators and variable dimming frequency, to achieve both high efficiency and high performance dimming. By using the proposed variable dimming frequency scheme, high dimming frequency is applied to a string with high dimming ratio, which helps to maintain the deviation of LED string current in an acceptable range, while low dimming frequency is applied to a string with low dimming ratio, which helps to achieve rectangular LED current waveform. Meanwhile, the new time multiplexing control scheme automatically optimizes the LED string's bus voltages, thus minimizes each string's power loss. A three string LED driver prototype is constructed to validate the effectiveness of the peoposed control scheme, where the three strings can have different dimming ratios between 4% and 100%.

High‐efficiency multi‐string LED driver based on constant current bus with time‐multiplexing control

A high-efficiency multi-string LED driver based on constant current bus with time-multiplexing control scheme is proposed and analysed. Each LED string is connected to the constant current bus, which is provided by the output of a front-end high-efficiency converter. The current of each LED string can be independently controlled by the turn on duty ratio of its time-multiplexing switch. A capacitor is connected to the current bus to provide a current flowing path for constant bus current when none of the LED string is connected to the current bus. It needs only one output filter capacitor, which makes circuit volume small and cost low. Finally, a 7.2 W two-string LED driver is provided to verify the studied results.

A Single-Inductor Multiple-Output Auto-Buck-Boost DC–DC Converter With Autophase Allocation

A single-inductor multiple-output (SIMO) converter with auto-buck-boost feature is presented in this paper. A seamless auto-buck-boost scheme for SIMO dc–dc converter using time-multiplexing control is proposed. Additionally, with the proposed first-order phase-locked loop (FOPLL) and autophase allocation, this circuit solves the problem of unbalanced loadings of different channels, and it also keeps the locking time of the inductor current sufficiently short to minimize average inductor current for attaining higher efficiency. By combining with all channel controllers, FOPLL not only allows fast load-transient response without degrading the power efficiency, but it also reduces controller order of the frequency control loop, attenuates the noise injected from charge pump, and achieves robust stability. The scheme enables the dc–dc converter to operate from wide input and output ranges. Implemented in a 0.35-μm CMOS technology, the chip area is 5000 μm × 1850 μm, including ESD test pads. The switching frequency is fixed at 0.25 MHz. The load-transient response time is less than 100 μs. The proposed converter achieves a peak efficiency of 89% and maximum output power up to 1.46 W with efficiency of 70%.

Scalability of Quasi-Hysteretic FSM-Based Digitally Controlled Single-Inductor Dual-String Buck LED Driver to Multiple Strings

There has been growing interest in single-inductor multiple-output (SIMO) dc-dc converters due to its reduced cost and smaller form factor in comparison with using multiple single-output converters. An application for such a SIMO-based switching converter is to drive multiple LED strings in a multichannel LED display. This paper proposes a quasi-hysteretic finite-state-machine-based digitally controlled single-inductor dual-output buck switching LED driver operating in discontinuous conduction mode (DCM) and extends it to drive multiple outputs. Based on the time-multiplexing control scheme in DCM, a theoretical upper limit of the total number of outputs in a SIMO buck switching LED driver for various backlight LED current values can be derived analytically. The advantages of the proposed SIMO LED driver include reducing the controller design complexity by eliminating loop compensation, driving more LED strings without limited by the maximum LED current rating, performing digital dimming with no additional switches required, and optimization of local bus voltage to compensate for variability of LED forward voltage VF in each individual LED string with smaller power loss. Loosely binned LEDs with larger VF variation can, therefore, be used for reduced LED costs.

A SIMO Parallel-String Driver IC for Dimmable LED Backlighting With Local Bus Voltage Optimization and Single Time-Shared Regulation Loop

Traditional LED drivers with multiple converters for powering up multiple strings in parallel suffer from high system volume and cost. The reported literature with single converter and dynamic bus voltage offers compact designs. However, the performance on power consumption is degraded. Meanwhile, all the aforementioned approaches require multiple current regulation elements, which inflict current balance errors due to mismatches. A compact single-inductor multiple-output parallel-string LED driver with time-multiplexing control is, thus, proposed. It can independently optimize local bus voltages for power loss reduction. In addition, a single time-shared control loop is proposed for current regulation in multiple parallel strings, resulting in a dramatic reduction of current balance errors. A 0.35 μm CMOS prototype achieves 2.8 times loss reduction over the reported literature, with a current balance error well controlled below 1.7%. The control scheme also offers flexible dimming for advanced backlighting operations.

Flyback-Based Single-Stage Power-Factor-Correction Scheme With Time-Multiplexing Control

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A flyback-based single-stage power-factor-correction scheme with time-multiplexing control (TMC) is proposed. As a portion of the input power will be transferred to the output after the first power processing to improve the conversion efficiency, the output voltage would contain substantial low-frequency ripple. An isolated auxiliary circuit based on forward topology is therefore added to the converter to serve as a buffer and a ripple suppression circuit. With TMC, all the power processes can be achieved by a single transformer to lower the size and cost of the converter. In addition, the proposed converter inherits bulk capacitor (auxiliary) voltage clamping capability. The experimental results confirmed the effectiveness of the proposed scheme with high power factor, natural bulk capacitor (auxiliary) clamping voltage, and tight output regulation. </para>

Single-switch dual output flyback DC/DC converter with time multiplexing control

Controlling two outputs with a single controlling switch in the power converter presents difficulties when two contrasting actions are required to raise one output and decrease the other. This paper studies the application of time multiplexing control (TMC) technique on power converters, with particular interest on single-switch multiple-output converters. Each output has its own feedback control circuit but these discrete feedback control loops are intermittently switched to regulate the duration of the 'on period' and 'off period' of the power switches. The inclusion of multiplexing logic to incorporate multiple controllers will improve the regulation of the auxiliary outputs and the main output within the tolerances required for electronic equipment. The output errors can be distributed between the outputs according to the time sharing factor of the time multiplexing logic controller. Simulation and experimental results on a single-switch dual-output flyback converter with and without TMC are reported to verify the error sharing capability of the proposed method. This control approach suggests a possible solution in improving the overall performance of the power supply in terms of output voltage regulation.

Single-inductor multiple-output switching converters with time-multiplexing control in discontinuous conduction mode

An integrated single-inductor dual-output boost converter is presented. This converter adopts time-multiplexing control in providing two independent supply voltages (3.0 and 3.6 V) using only one 1-/spl mu/H off-chip inductor and a single control loop. This converter is analyzed and compared with existing counterparts in the aspects of integration, architecture, control scheme, and system stability. Implementation of the power stage, the controller, and the peripheral functional blocks is discussed. The design was fabricated with a standard 0.5-/spl mu/m CMOS n-well process. At an oscillator frequency of 1 MHz, the power conversion efficiency reaches 88.4% at a total output power of 350 mW. This topology can be extended to have multiple outputs and can be applied to buck, flyback, and other kinds of converters.