Single-inductor Multiple-output Research Articles

Freewheel charge-pump controlled single-inductor multiple-output step-up DC–DC converter

This paper presents a freewheel-charge-pump-controlled design for a single-inductor multiple-output (SIMO) DC---DC Converter. By applying the freewheel-charge-pump-controlled (FCPC) technique, the ...

Adaptive pseudo-continuous conduction mode operation schemes and circuit designs for single-inductor multiple-output switching converters

As single-inductor multiple-output (SIMO) switching converters proliferate in integrated power management designs, pseudo-continuous conduction mode (PCCM) operation with freewheel switching has been well adopted owing to its effectiveness on cross-regulation, voltage ripple and switching noise issues, especially in heavy load scenarios. However, the technique faces a direct challenge in unbalanced loading conditions. Potential lengthy freewheel switching periods and high I dc current levels could lead to conduction and switching power losses, degrading the efficiency of the converters. To alleviate this problem, this paper presents adaptive PCCM operation schemes with the respective distributed and unified freewheel switching schemes. The optimal freewheel switching durations are achieved in various load conditions by adaptively adjusting the phase durations and freewheel switching I dc current level, thereby reducing the conduction and switching losses effectively. The switching power loss is further reduced by turning on/off the freewheel switch less frequently, without compromising the performance of operation. The proposed schemes have been implemented and verified in digital and analog-based SIMO power converters designed with 130 nm CMOS process.

A Single-Inductor Multiple-Output Switcher With Simultaneous Buck, Boost, and Inverted Outputs

Portable applications require multiple supplies with different output levels and some applications also require negative outputs. Single-inductor multiple-output (SIMO) switchers are a good for existing parallel output configurations. This study presents an SIMO dc-dc converter capable of generating buck, boost, and inverted outputs simultaneously. The operation of this class of converter being driven by the ripple in the inductor current the conventional averaging method does not work well. An inductor current ripple-based modeling approach has been proposed to accurately model and analyze the converter. The control, cross-coupling, and cross-regulation transfer functions, generated through the model, accurately represent the performance of the converter. The proof of concept has been carried out with discrete components on an in-house built PCB and the experimental results validating the steady state and ac responses of the converter are presented.

Predictive Digital Current Control of Single-Inductor Multiple-Output Converters in CCM With Low Cross Regulation

This paper presents a new digital current-mode control technique for single-inductor multiple-output converters in continuous-conduction mode. This predictive control method can calculate all the required duty cycles corresponding to the outputs for the next switching cycle. Since the calculation is based on every current reference representing the load current, all current control loops corresponding to different outputs are theoretically independent, which can greatly reduce the cross regulation. To avoid subharmonic oscillation, proper predictive digital current control is adopted. Inductor current estimation is used to remove the current sensing circuit, and corresponding calibration techniques are presented. Simulation and experimental results are given to verify the effectiveness of this control technique.

Hardware-Software Codesign of an Embedded Multiple-Supply Power Management Unit for Multicore SoCs Using an Adaptive Global/Local Power Allocation and Processing Scheme

Power dissipation has become a critical design constraint for the growth of modern multicore systems due to increasing clock frequencies, leakage currents, and system parasitics. To overcome this urgent crisis, this article presents an embedded platform for on-chip power management of a multicore System-on-Chip (SoC). The design involves the development of two key components, from the hardware to the software level. From the hardware perspective, a multiple-supply power management unit is proposed and is implemented using a Single-Inductor Multiple-Output (SIMO) DC-DC converter. To dynamically respond to the sensed instantaneous power demands and to accurately control the power delivery to the processor cores, the power management unit employs a software-defined adaptive global/local power allocation feedback controller. The proposed controller is designed using the hardware-software codesign methodology to uniquely control the SIMO converter during various operation scenarios. This is achieved using several embedded software control algorithms that operate synergetically to ensure efficient and reliable system operation. The hardware-software codesign technique also allows the SIMO controller to be integrated with future microprocessor cores. Therefore, by employing the vast amount of on-chip resources, the converter can perform effective power processing to provide the most power-optimal voltages at the hardware level. Such an embedded power management module leads to an integrated, power-aware, and autonomous SoC design that is independent of additional external hardware control, thereby reducing on-chip area and system complexity. In this design, each power output from the SIMO converter provides a step-up/down voltage conversion, thereby enabling a wide range of variable supply voltage. An adaptive global/local power allocation control algorithm is employed to significantly improve Dynamic Voltage and Frequency Scaling (DVFS) tracking speed and line/load regulation, while still retaining low cross-regulation. Designed with a 180nm CMOS process, the converter precisely provides three independently variable power outputs from 0.9 V to 3.0 V, with a total power range from 33 mW to 900 mW. A very fast load transient response of 3.25 μ s is achieved, in response to a 67.5-mA full-step load current change. The design thus provides a cost-effective power management solution to achieve a robust, fast-transient, DVFS-compatible multicore SoC.

On-Chip Single-Inductor Multiple-Output Power Converter Design with Adaptive Cross Regulation and Supply Variation Control for Power-Efficient VLSI Systems

Dynamic voltage and frequency scaling (DVFS) algorithms are widely used power management techniques which enable the optimization of system-level power dissipation, energy consumption and operation performance. One cost-effective hardware-enabling platform to implement the DVFS is through single-inductor multiple-output (SIMO) DC-DC converters. However, the major drawback with such converters is cross regulation, which leads to undesired supply voltage variations. These variations have significant impact on modern VLSI applications, from the circuit to the system level. Based on these challenges, this paper presents a cross-layered design of two SIMO DC-DC converters with an adaptive freewheel switching technique. The proposed converters are able to minimize cross regulation by adaptively adjusting the freewheel switching durations and currents. This also increases the efficiency of the SIMO converters, by reducing the conduction losses due to the lossy freewheel switch. To verify the cross regulation performance of the SIMO converters, its influence on clock frequencies generated by a ring oscillator is investigated. By simulating various load transient conditions, it is shown that the SIMO converters are able to significantly minimize frequency variations. The operation of the converters is verified through transistor-based HSPICE simulation results, with a 130-nm CMOS process. The SIMO converter with the digital-based adaptive freewheel switching controller achieves a maximum efficiency of 93.2%, while the analog counterpart achieves a maximum efficiency of 93.4%. For a load change from 200 mA to 40 mA, the proposed technique reduces the conduction losses during the freewheel switching duration by 99.96%, compared with traditional methods.

Topologies and control of a class of single inductor multiple-output converters operating in continuous conduction mode

In this paper, continuous conduction mode (CCM) operation of a class of single inductor multiple output dc-dc converters is proposed. The power stage combines boost and buck-boost structures loading non-inverted and inverted outputs. The control strategy is based on current mode control under an interleaving scheme, in which each output is controlled by a specific channel. These channels use different dynamic references, which are obtained from a set of proportional-integral (PI) controllers associated to the voltage outputs. The dynamical behaviour of this system is described by means of a large signal averaged model and direct simulations of the switched circuit-based model. Small signal stability analysis of the slow scale dynamics is also carried out by using the averaged model. Finally, some experimental results are provided to validate the theoretical predictions and the numerical simulations.

Enabling Power-Efficient DVFS Operations on Silicon

With the perpetual power increase in modern VLSI systems, efficient and effective power management has been critical to next-generation IC designs. To overcome this grand challenge, techniques, such as dynamic voltage/frequency scaling (DVFS), have been proposed to jointly optimize power, energy and operating performance, leading to significantly improved system reliability, efficiency and battery lifetime. From both system-level and circuit-level perspectives, this paper investigates key design issues, control schemes, circuit architectures and future research directions, involved in the development of application-aware, multiple- and variable-output DC-DC power converters. The article first discusses key multiple-output converters such as the single-inductor multiple-output (SIMO) DC-DC converters and their system-level integration for DVFS power management, followed by our investigation on various adaptive-output power converter topologies and corresponding design challenges. The paper also addresses the importance of hardware-software co-design for future power management systems. With the integration of the enabling hardware platform, power processing, in addition to the traditional signal processing, rises to become another key factor to next-generation VLSI designs. This naturally enables effective on-chip power tracking, power processing and thermal monitoring. More importantly, it would significantly change traditional design concepts and largely benefit signal processing in return, eventually leading to revolutionary changes on system reliability, performance, efficiency and operating lifetime.

Single-Inductor–Multiple-Output Switching DC–DC Converters

Emerging feature dense portable microelectronic devices pose several challenges, including demanding multiple supply voltages from a single miniaturized power-efficient platform. Unfortunately, the power inductors used in magnetic-based switching converters (which are power efficient) are bulky and difficult to integrate. As a result, single-inductor-multiple-output (SIMO) solutions enjoy popularity, but not without design challenges. This brief describes, illustrates, and evaluates how SIMO dc-dc converters operate, transfer energy, and control (through negative feedback) each of their outputs.

Integrated zero-inductor-current detection circuit for step-up DC–DC converters

A new integrated zero-inductor-current detection circuit suitable for step-up DC–DC converters is presented. The detection circuit can correctly detect zero-inductor-current with a novel method. The method helps overcome difficulties in measuring online current from on-resistance of output PMOS switches. With its simplicity and independence from output PMOS switches, this circuit promises wide application in either single-output step-up DC–DC converters or single inductor multiple output (SIMO) step-up DC–DC converters with different control theories, and especially in discontinuous-conduction-mode (DCM) operation.

A pseudo-CCM/DCM SIMO switching converter with freewheel switching

This paper presents a single-inductor multiple-output (SIMO) converter operating in pseudo-continuous conduction mode (PCCM) and/or discontinuous conduction mode (DCM). With the proposed freewheel switching control, this converter can handle large load currents with a much smaller current ripple, while retaining low cross regulation. It can also work in DCM for high efficiency at light loads. A prototype of a single-inductor dual-output (SIDO) boost converter was fabricated with a standard 0.5-/spl mu/m CMOS n-well process. The two outputs are regulated at 2.5 and 3.0 V, respectively. At an oscillator frequency of 1 MHz, the efficiency reaches 89.4% at a total output power of 320 mW. Compared with prior designs, both current and voltage ripples are reduced. This design can be extended to have multiple outputs and for different types of dc-dc conversions, or be applied to single-output converters for fast transient response.