DC-DC Switching Regulators Research Articles

Analytic design of constrained control laws for nonlinear dynamic systems with symmetric and asymmetric limits

In this article, we formulate and investigate dynamic optimisation of systems with control limits. Aerial, electronic, electromechanical, mechatronic and robotic systems exhibit symmetric and asymmetric bounds. Applying a Hamiltonian optimisation, and, minimisation of specified-by-constraints nonquadratic performance functionals result in analytically designed bounded control laws. Closed form solution of an optimisation problem is found. Continuous control algorithms ensure consistency to physical systems and homogeneous performance. Findings in dynamic optimisation and constrained control are analytically, numerically and experimentally substantiated. Experimental studies and results are documented for a dc-dc switching regulator and permanent-magnet synchronous motor.

An Active EMI Cancellation Technique Achieving a 25-dB Reduction in Conducted EMI of LIN Drivers

Robustness to electromagnetic interference (EMI) is one of the primary design aspects of state of the art automotive ICs like System Basis Chips (SBCs) which provide a wide range of analog, power regulation and digital functions on the same die. One of the primary sources of conducted EMI on the Local Interconnect Network (LIN) driver output is an integrated switching DC-DC regulator noise coupling through the parasitic substrate capacitance of the SBC. In this paper an adaptive active EMI cancellation technique to cancel the switching noise of the DC-DC regulator on the LIN driver output to ensure electromagnetic compatibility (EMC) is presented. The proposed active EMI cancellation circuit synthesizes a phase synchronized cancellation pulse which is then injected onto the LIN driver output using an on-chip tunable capacitor array to cancel the switching noise injected via substrate. The proposed EMI reduction technique can track and cancel substrate noise independent of process technology and device parasitics, input voltage, duty cycle and loading conditions of the DC-DC switching regulator. The EMI cancellation system is designed and fabricated on a 180nm Bipolar-CMOS-DMOS (BCD) process with an integrated power stage of a DC-DC buck regulator at a switching frequency of 2MHz along with an automotive LIN driver. The EMI cancellation circuit occupies an area of 0.7 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , which is less than 3% of the overall area in a standard SBC and consumes 12.5 mW of power and achieves 25 dB reduction of conducted EMI in the LIN driver output’s power spectrum at the switching frequency and its harmonics.

Design of Ultra-Low Noise and Low Temperature Usable Power System for High-Precision Detectors

In high-precision detector systems, the power supply usually need to be ultra-low noise and stabilized. Design and implementation of an ultra-low noise power supply is described in this paper. We implemented and tested the power system actually in a scientific CCD (Charge-coupled device) detector system, but the design structure could be used in many high-precision detector systems as infrared detector or high-energy particles detectors. The power system uses DC-DC switching regulators and LDO regulators for power generating, uses multi-stage filters for noise reducing. Multi-output power supply with noise about $40~\mu \text {V}_{\mathbf {rms}}$ is achieved, the overall energy efficiency is 68.5%. Besides, the electronic system takes the low temperature as an important consideration, and the system has been tested in an extreme environment as low as 193 K.

Control Scheme for Reduced Cross-Regulation in Single-Inductor Multiple-Output DC–DC Converters

Single-inductor multiple-output (SIMO) dc-dc switching regulators are potentially very good replacement to multiple parallel converters in today's power management units for portable applications where multiple supplies are required. The outputs in these converters being coupled, cross-regulation among the outputs plays a major role in deciding the performance of the system. This paper proposes a control scheme that ensures good load and line regulation and stable system dynamics and reduces cross-regulation effect significantly. In designing a control scheme, proper analysis of the system is an important factor, and SIMO class of converters being driven by a ripple in the inductor current, conventional modeling does not hold good. Consequently, a ripple-based modeling approach that accurately judges the system performance is adopted. A cross-derivative state feedback control methodology has been proposed so as to completely decouple the outputs. Finally, a single-inductor dual-output SIMO converter has been built on a printed circuit board using discrete components, and the test results presented validate the modeling technique proposed. The simulation and experimental results show that the proposed control scheme significantly reduces cross-regulation at the outputs.

Soft-Start Circuit Based on Switched-Capacitor for DC-DC Switching Regulator

An on-chip soft-start circuit based on a switched-capacitor for DC-DC switching regulator is presented. A ramp-voltage, which is generated by a switched-capacitor, is used to make pulse width slowly increase from zero, in order to eliminate the inrush current and the overshoot voltage during start-up. The post simulation results show that the regulator soft starts well with the proposed soft-start circuit.

A Double-Hybrid Spread-Spectrum Technique for EMI Mitigation in DC-DC Switching Regulators

Randomizing the switching frequency (RSF) to reduce the electromagnetic interference (EMI) of switching power converters is a well-known technique that has been previously discussed. The randomized pulse position (RPP) technique, in which the switching frequency is kept fixed while the pulse position (the delay from the starting of the switching cycle to the turn-on instant within the cycle) is randomized, has been previously addressed in the literature for the same purpose. This paper presents a double-hybrid technique (DHB) for EMI reduction in dc-dc switching regulators. The proposed technique employed both the RSF and the RPP techniques. To effectively spread the conducted-noise frequency spectrum and at the same time attain a satisfactory output voltage quality, two parameters (switching frequency and pulse position) were randomized, and a third parameter (the duty ratio) was controlled by a digital compensator. Implementation was achieved using field programmable gate array (FPGA) technology, which is increasingly being adopted in industrial electronic applications. To evaluate the contribution of the proposed DHB technique, investigations were carried out for each basic PWM, RPP, RSF, and DHB technique. Then a comparison was made of the performances achieved. The experimentally investigated features include the effect of each technique on the common-mode, differential-mode, and total conducted-noise characteristics, and their influence on the converter’s output ripple voltage.

Runtime Extension of Low-Power Wireless Sensor Nodes Using Hybrid-Storage Units

The sensor nodes of wireless sensor networks remain inactive most of the time to achieve longer runtimes. Power is mainly provided by batteries, which are either primary or secondary. Because of its internal impedance, a significant voltage drop can appear across the battery terminals at the activation time of the node, thus preventing the extraction of all the energy from the battery. Additionally, internal losses can also be significant. Consequently, the runtime is reduced. The addition of a supercapacitor in parallel with the battery, thus forming a hybrid-storage device, has been proposed under pulsed loads to increase the power capabilities and reduce both the voltage drop and the internal losses at the battery. However, this strategy has not yet thoroughly been analyzed and tested in low-power wireless sensor nodes. This paper presents a comprehensive theoretical analysis that extends previous works found in the literature and provides design guidelines for choosing the appropriate supercapacitor. The analysis is supported by extensive experimental results. Two low-capacity (< 200 mAh) batteries were tested together with their hybrid-storage unit counterparts when using an electronic load as a pulsed current sink. The hybrid-storage units always achieved a higher runtime. One of the batteries was also tested using a sensor node. The runtime extension was 16% and 33% when connecting the hybrid-storage unit directly and through a dc-dc switching regulator to the sensor node, respectively.

Optimal Buck Converter Output Filter Design for Point-of-Load Applications

This paper presents a novel method to design the output filter of low-voltage/high-current buck dc-dc switching regulators. The method is based on the concept of acceptability boundary curves (ABCs). ABCs are the curves bounding the regions in the space of parameters, including commercial components which ensure an acceptable output voltage ripple and a load-transient surge based on design specifications. ABCs help in quickly finding tradeoff design solutions, as well as in a better understanding of the functional correlations among power components. Examples regarding buck converters for point-of-load applications are discussed to highlight the flexibility and reliability of the ABC-based design method. Experimental measurements confirm the analytical results and numerical predictions.

Tolerance design of controllers for switching regulators

An evolutionary approach to worst case tolerance design is introduced here, with a focus on feedback compensation networks for dc-dc switching converters. Assumed that varying parameters values are uniformly distributed and uncorrelated, as provided by the worst case approach, the proposed algorithm, of general applicability, seeks for the set of nominal values and tolerances of the circuit parameters ensuring that the design constraints are met and that a user-defined circuit performance index assumes its optimal value. Design constraints, are fixed in the frequency domain, in terms of acceptability ranges of loop gain crossover frequency and phase margin, to guarantee closed loop stability and the desired dynamic performance. Resistive and capacitive compensation network's parameters values are chosen within a suitable database of couples nominal value/tolerance available on the market, while the nominal values and tolerances of the parameters of the power stage are fixed. Referring to a buck dc-dc switching regulator, two widely used different compensation network topologies are compared in terms of reliability, robustness, and cost of components. Simulation results show the wide usefulness of the proposed method in supporting designer decisions.

A dynamic voltage scaled microprocessor system

A microprocessor system is presented in which the supply voltage and clock frequency can be dynamically varied so that the system can deliver high throughput when required while significantly extending battery life during the low speed periods. The system consists of a dc-dc switching regulator, an ARM V4 microprocessor with a 16-kB cache, a bank of 64-kB SRAM ICs, and an I/O interface IC. The four custom chips were fabricated in a standard 0.6-/spl mu/m 3-metal CMOS process. The system can dynamically vary the supply voltage from 1.2 to 3.8 V in less than 70 /spl mu/s. This provides a throughput range of 6-85 MIPS with an energy consumption of 0.54-5.6 mW/MIP yielding an effective energy efficiency as high as 26200 MIPS/W.

Large-signal modeling and simulation of switching DC-DC converters

A general nonlinear continuous formulation procedure for large-signal analysis of switching DC-DC converters is presented. The method can be applied in either of the two conduction modes, and it is easily programmed for computer-aided analysis with small simulation time. A boost regulator operating in constant-frequency current-programmed mode is used to illustrate the application of the method. A stability graph is subsequently developed to facilitate the design of DC-DC switching regulators for large-signal applications. The graph provides an estimation of the values of input voltage and load resistance leading to a stable regulator behavior.