An integrated five-output single-inductor multiple-output dc-dc converter with ordered power-distributive control (OPDC) in a 0.5 mum Bi-CMOS process is presented. The converter has four main positive boost outputs programmable from +5 V to +12 V and one dependent negative output ranged from -12 V to -5 V. A maximum efficiency of 80.8% is achieved at a total output power of 450 mW, with a switching frequency of 700 kHz. The performance of the converter as a commercial product is successfully verified with a new control method and proposed circuits, including a full-waveform inductor-current sensing circuit, a variation-free frequency generator, and an in-rush-current-free soft-start method. With simplicity, flexibility, and reliability, the design enables shorter time-to-market in future extensions with more outputs and different operation requirements.

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A Single-Inductor Switching DC–DC Converter With Five Outputs and Ordered Power-Distributive Control

A load-dependant peak-current control single-inductor multiple-output (SIMO) DC-DC converter with hysteresis mode is proposed. It includes multiple buck and boost output voltages. Owing to the adaptive adjustment of the load-dependant peak-current control technique and the hysteresis mode, the cross-regulation can be minimized. Furthermore, a new delta-voltage generator can automatically switch the operating mode from pulse width modulation (PWM) mode to hysteresis mode, thereby avoiding inductor current accumulation when the total power of the buck output terminals is larger than that of the boost output terminals. The proposed SIMO DC-DC converter was fabricated in TSMC 0.25 mum 2P5M technology. The experimental results show high conversion efficiency at light loads and small cross-regulation within 0.35%. The power conversion efficiency varies from 80% at light loads to 93% at heavy loads.

https://ir.nctu.edu.tw:443/bitstream/11536/27787/1/000265092300008.pdf

Single-Inductor Multi-Output (SIMO) DC-DC Converters With High Light-Load Efficiency and Minimized Cross-Regulation for Portable Devices

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.

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

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.

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

Cross regulation is the main technical challenge of a single-inductor multiple-output (SIMO) dc-dc converter. This paper proposes a multivariable digital controller to suppress the cross regulation of a single-inductor dual-output (SIDO) buck converter in continuous conduction mode (CCM) operation. The controller design methodology originates from the open-loop shaping of the multi-input multi-output (MIMO) systems. The control design procedure includes: 1) determination of a family of nonparametric models of the SIDO converter at operating points of interest, 2) determination of the class of the controller, and 3) system open-loop shaping by the convex minimization of the summation of the square second norm of the errors between the system open-loop transfer function matrices and a desired open-loop transfer function matrix. The proposed controller minimizes the coupling between the outputs of the SIDO converter and provides satisfactory dynamic performance in CCM operation. This paper describes the theoretical aspects involved in the design procedure of the controller and evaluates the performance of the controller based on simulation studies and experiments.

Multivariable Control of Single-Inductor Dual-Output Buck Converters

A single-inductor dual-output boost converter reported in [1] works either in discontinuous conduction mode or in pseudo-continuous conduction mode and requires separate controllers. As each controller regulates the output in time-multiplexed manner, it is difficult to extend the number of outputs and power capacity. The converter reported in [2] solves these limitations by adopting comparator-controlled method. Each comparator-controlled output receives its required energy and one final PWM controller adjusts the total inductor current so that the remaining current is adequate for the last output. However, as the PWM controller regulates one of the converter outputs, the response of controller becomes slow and voltage ripple of the other outputs increases when the load current of PWM-controlled output is reduced to zero (or near zero). As a possible solution, minimum bleeding current can be set for the last output, however, this approach degrades the efficiency at light-load condition. Also, the operation region of the previously reported multiple-output converters is restricted to step-up mode only.

Multiple-output step-up/down switching DC-DC converter with vestigial current control

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.

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

The luminance of AMOLED displays varies depending on the temperature owing to panel degradation. In this paper, a luminance compensation method using a monitor pixel with a multiple output boost converter and DAC for digital driving scheme is introduced. This method makes the panel luminance constant irrespective of the temperature. Furthermore, it has lower power consumption compared with the previous compensation method using monitor pixel.

Sung-il Kim

Papers

A Single-Inductor Switching DC–DC Converter With Five Outputs and Ordered Power-Distributive Control

Multiple-output step-up/down switching DC-DC converter with vestigial current control

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

60.2: Low-Power Consumptive Luminance Compensation for a Digital Driving AMOLED Display using a Multiple Output Boost Converter