DC–DC converters with voltage boost capability are widely used in a large number of power conversion applications, from fraction-of-volt to tens of thousands of volts at power levels from milliwatts to megawatts. The literature has reported on various voltage-boosting techniques, in which fundamental energy storing elements (inductors and capacitors) and/or transformers in conjunction with switch(es) and diode(s) are utilized in the circuit. These techniques include switched capacitor (charge pump), voltage multiplier, switched inductor/voltage lift, magnetic coupling, and multistage/-level, and each has its own merits and demerits depending on application, in terms of cost, complexity, power density, reliability, and efficiency. To meet the growing demand for such applications, new power converter topologies that use the above voltage-boosting techniques, as well as some active and passive components, are continuously being proposed. The permutations and combinations of the various voltage-boosting techniques with additional components in a circuit allow for numerous new topologies and configurations, which are often confusing and difficult to follow. Therefore, to present a clear picture on the general law and framework of the development of next-generation step-up dc–dc converters, this paper aims to comprehensively review and classify various step-up dc–dc converters based on their characteristics and voltage-boosting techniques. In addition, the advantages and disadvantages of these voltage-boosting techniques and associated converters are discussed in detail. Finally, broad applications of dc–dc converters are presented and summarized with comparative study of different voltage-boosting techniques.

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Step-Up DC–DC Converters: A Comprehensive Review of Voltage-Boosting Techniques, Topologies, and Applications

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

A single-inductor step-up DC-DC switching converter with bipolar outputs is implemented for active-matrix OLED mobile display panels. The positive output voltage is regulated by a boost operation with a modified comparator control (MCC), and the negative output voltage is regulated by a charge-pump operation with a proportional-integral (PI) control. The proposed adaptive current-sensing technique successfully supports the implementation of the proposed converter topology and enables the converter to work in both discontinuous-conduction mode (DCM) and continuous-conduction mode (CCM). In addition, with the MCC method, the converter can guarantee a positive output voltage that has both a fast transient response of the comparator control and a small output voltage ripple of the PWM control. A 4.1 mm2 converter IC fabricated in a 0.5 mum power BiCMOS process operates at a switching frequency of 1 MHz with a maximum efficiency of 82.3% at an output power of 330 mW.

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A Single-Inductor Step-Up DC-DC Switching Converter With Bipolar Outputs for Active Matrix OLED Mobile Display Panels

A single-chip dual-output step-up DC-DC converter is implemented for active-matrix OLED mobile display panels. The bipolar outputs are regulated independently and integrated with a boost and a charge-pump topology sharing a single inductor. The chip is 4.1mm2 fabricated in a 0.5 mum power BiCMOS process and operates at 1MHz with a maximum efficiency of 82.3% at an output power of 330mW.

A Single-Inductor Step-Up DC-DC Switching Converter with Bipolar Outputs for Active Matrix OLED Mobile Display Panels

Cost and size are very important issues for power-management ICs (PMICs), in particular for portable systems where typically multiple voltage levels are required to achieve multi functionality. To meet these requirements, a single-inductor multiple-output (SIMO) switching converter is a very strong candidate. SIMO converters have been the subject of many recent studies and reports [1–3]. The presented converters uses the current-mode controller and PWM with a constant switching frequency. However, designing the feedback control loop of the PWM converters is not an easy task since their stability inherently depends on the load conditions.

A PLL-based high-stability single-inductor 6-channel output DC-DC buck converter

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.

Chang-Seok Chae

Papers

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

A Single-Inductor Step-Up DC-DC Switching Converter With Bipolar Outputs for Active Matrix OLED Mobile Display Panels

A Single-Inductor Step-Up DC-DC Switching Converter with Bipolar Outputs for Active Matrix OLED Mobile Display Panels

A PLL-based high-stability single-inductor 6-channel output DC-DC buck converter

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