Single-inductor Multiple-output Research Articles

Modeling and analysis of digital current‐mode controlled single‐inductor dual‐output DC–DC converter with different PWM modulation modes

SummaryCurrent‐mode control is extensively used in dc–dc converters as the merits of fast transient performance, simple control loop, and elimination of right‐half‐plane zeros for boost‐type dc–dc converters. In single‐inductor multiple‐output (SIMO) dc–dc converter, the inductor current would present different trends under different circuit parameters. Therefore, the control logic changes for different inductor current trends, and the corresponding modulations are absolutely different. In this paper, a digital current‐mode control technology for SIMO dc–dc converter is proposed to expend the convenience of current‐mode control with different inductor trends. Choosing continuous conduction mode (CCM) single‐inductor dual‐output (SIDO) dc–dc converter as the research object, the principles are analyzed under different pulse width modulation modes, and the corresponding control algorithms are derived. Moreover, the discrete iterative map model is established to analyze the stability of input and output voltages varying. The results show that not only the digital current‐mode controlled SIDO buck converter has fast load transient response and small cross‐regulation but also the input and output voltages will not affect the stability in the leading edge modulation, which is different from the corresponding analog current‐mode control technology. Finally, the experimental results verify the correctness of the theoretical analysis.

Considerations on Practical Implementation of Current Source Mode Single-Inductor Multiple-Output LED Driver

There are many possible LED lighting applications where separate regulation of the LED current (luminous flux) of individual LED strings would be desirable—specialized variable correlated color temperature lights for ambient lighting, decorative lighting, surgical lights, horticultural lights, etc. Separate regulation of the current or light flux of individual LED strings is associated with a known problem: the necessity of using a controllable LED driver for each string, which increases the total component count, overall system complexity and costs. One of the possible solutions—a current source mode single-inductor multiple-output LED driver—was discussed in previous different papers. However, the practical implementation of this solution was not discussed in detail. This article aims to correct this omission.

An efficient controller design of a PV integrated single inductor multiple output DC-DC converter for dynamic voltage and low power applications.

In this article, a Single Inductor Multiple Output (SIMO) DC-DC boost converter for driving independent three outputs of dynamic voltage and low power is proposed. Compared with the traditional SIMO DC-DC converter, the proposed work accomplishes (i) independent control of power at each output, (ii) small switch count, (iii) relatively better scalability with increasing output channel, (iv) fast response time, and (v) relatively better efficiency. The core aim of the current article is to implement an efficient controller design of the SIMO DC converter circuit operating in continuous conduction mode for dynamic voltage applications. The SIMO circuit comprises a photovoltaic (PV) array as a renewable energy harvesting source at the input. A hysteretic controller based on direct control with seamless transition control topology is implemented in this model for SIMO operation. This scheme is popular due to its less cost, simple, easy-to-use design architecture, and fast speed of close loop control. The configuration of the solar array is designed to deliver maximum power on the input of the SIMO DC-DC converter. For tracking the maximum power point, incremental conductance with integral control configuration is applied on the PV array with fast speed and efficiency. The MATLAB/Simulink environment is utilized for model configuration. The simulation results show that the proposed SIMO configuration with the PV array provided 100.5 W and 21.7 W for 1000 W/m2 and 250 W/m2, respectively.

A Pseudo-LDO-Assist Charge-Control SIMO Buck DC-DC with 0.02 mV/mA Cross Regulation

Cross-regulation (CR) suppression is a challenge in single-inductor-multiple-output (SIMO) DC-DC. The pseudo-LDO-assist technology is presented to decrease CR of charge-control SIMO Buck DC-DC in this paper. With the fast current compensation of the proposed pseudo-LDO, the CR of the last DC-output, which used to be the largest CR in traditional charge-control SIMO, could be suppressed to the same level as that of the other DC-outputs regulated by charge control. Experimental results show that the largest CR of the proposed SIMO Buck DC-DC is 0.02 mV/mA in 488 mA load transient, which shows a 42.86% improvement compared to the existing charge-control SIMO.

Fully Decoupled Current Control and Current Balancing of the Modular Structure for LED Color-Mixing System

For LED color-mixing, the different color LEDs need to be controlled independently, so a fully decoupled current control and current balancing of the modular structure is proposed for LED color-mixing system. The capacitive current-balancing structure is combined with the quasi-boost converter to realize the decoupled current control and current balancing in each module. The capacitive current-balancing structure is based on the relative reactance of the capacitor with respect to the equivalent resistance of the associated LED string. The inductor in quasi-boost converter is used to further stable the output current flowing through each LED string, and the switch in quasi-boost converter for controlling the current of each LED string adopts the parallel connection to protect LEDs from the current-spike caused by the switch. The structure is modularity and scalability so that the different color LEDs can be added and removed easily. Compared with SIMO (Single-Inductor-Multiple-Output) structure, the proposed structure has no cross-coupling issues. The LED string currents working with PWM mode have a good current-balancing performance since the equivalent resistance of LED string is much smaller than the reactance of capacitors. In addition, the resonant capacitors separate the grounds of the power source and LED strings, so all the switches in parallel with LED strings do not need the isolated gate drivers. A prototype with RGB modules has been built and evaluated, and the experimental results have a good agreement with the theoretical analysis.

An optimization method for PLL‐based charge control SIMO Buck DC‐DC

SummaryThe PLL‐based charge control scheme is optimized and implemented in a single‐inductor multiple‐output (SIMO) Buck DC‐DC in this paper. In order to decrease cross regulation (CR) during heavy load transient, the gain adaptive charge pump (GACP) is optimized to speed up the regulation of inductor current, and the current loop off‐time (CLOT) control is introduced to prevent the PLL‐based structure from frequency unlock. The proposed SIMO is designed in a 0.18 μm standard CMOS process. Experimental results show that the worst CR performance is 0.026 mV/mA, which is a 50% improvement of PLL‐based charge control scheme and 61.19% advantage above the existing charge‐controlled SIMO.

An Inductor-First Single-Inductor Multiple-Output Hybrid DC–DC Converter With Integrated Flying Capacitor for SoC Applications

With the increasing complexity of highly integrated system on chips (SoCs), the power management system (PMS) is required to provide several power supplies efficiently for individual blocks. This paper presents a single-inductor multiple-output (SIMO) inductor-first hybrid converter that generates three outputs between 0.4V and 1.6V from a 1.8V input. The proposed multiple-output hybrid power stage can improve the conversion efficiency by reducing inductor current while extending the output voltage range compared with the existing hybrid topologies. In addition, the proposed converter employs an on-chip switched-capacitor power stage (SCPS) with a dual-switching frequency technique, resulting in a fast response time, low cross-regulation, and reduced number of on-chip pads. Measurement results show that the converter achieves a peak efficiency of 87.5% with the maximum output current of 450mA. The converter is integrated with a fast voltage regulation loop with 500MHz system clock to achieve a less than 0.01mA/mV cross-regulation and a maximum 20mV overshoot at full-load transient response. The design is fabricated in the standard 180nm CMOS technology.

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.

Design of Single Input Multiple Output Buck Converter with Light Load Efficiency

The major demand for portable electronics devices such as pagers, laptops, cellular phones etc. Single input multiple output (SIMO) converter will be proposed to give different supply voltages while keep up prolong battery life. A single-discharge (SDC) control scheme is introduce to simplify the Single inductor multiple output design, attain to low cross regulation, and to support board range of loads with decent efficiency of power. A Single discharge control single input multiple output buck converter with 4 outputs composed of comparators, phased-locked loop, finite state machine (FSM) controller, and an output stage. In addition to the basic switching functions, the FSM controller provides a state skipping feature to allow no-load regulation. Single input multiple output converter is available for less cost and used for maintaining long battery life and they are growing in vast range with rich feature portable electronic device. The design of converter is designed for limited range for prolonged battery life. The SIMO converters are used for the reduction of cost and switching losses, hence improve system efficiency. In our study, we proposed buck converter topology with single input of 24v and multiple output of 12v and 5v. The 12v voltage is used for electric vehicles. In electric vehicles it is used in horns and headlights. 5v voltage is used for small signal and stability analysis. The simulated conversion efficiency for peak power is 86% the power ranging for output is 50 to 300mW. The ICs exhibit has a low measured peak efficiency of 73% and cross regulation of 0.24 mV/mA because of parasitic bond wire resistance. The proposed system is simulated in MATLAB/Simulink software.

Voltage Regulation and Power Consumption Analysis of LED Driver using Switched String Method

This paper discusses an AC/DC buck converter-based LED driver to reduce the voltage from 230VAC to 12VDC with a few strings of LEDs. This led driver is designed with a cost-effective circuit because using a single inductor, single inductor multiple-output (SIMO) can reduce the number of components, control the current independently and precisely on each LED string simultaneously, compared to using an inductor on each LED string. To control current and voltage, PWM (Pulse Width Modulation) control is used as a MOSFET signal switch. This MOSFET calculates the duty cycle so that the desired DC output according to the LED specifications can be realized. The circuit was analyzed using PSpice software. The test based on the duty cycle shows that the highest output voltage is obtained with a work cycle of 10% resulting in a voltage of 5.9V and a current of 32.4mA. Meanwhile, achieving the output value based on the led specification with a voltage of 12V and a maximum current of 31mA has been achieved at a duty cycle of 4.7%. This AC/DC buck converter circuit not only lowers the voltage but can overcome dimming and provide a uniform light output on each LED with an output voltage of 12VDC. The experimental results show that this AC/DC buck converter circuit has been tested and can be applied to the Led driver system.

A Single-Inductor–Multiple-Output (SIMO) 0.8-V/1.8-V/12-V Step-Up/Down Converter With Low-Quiescent Current for Implantable Electroceutical SoCs

This letter presents a single-inductor multiple-output (SIMO) step-up/down DC-DC converter for an implantable electro-ceutical system-on-chip (SoC), which generates the supply voltages of 0.8 V, 1.8 V, and 12 V from a battery (3 -4.2 V). To extend the battery life-time during a long standby period, the load-adaptive frequency-scaling (LAFS) without an active load sensor is proposed, effectively reducing the quiescent current under light loads at no expense of tran-sient response performance. Also, this paper introduces a new design of a low-power adaptive on-time (AOT) generator to achieve a consist-ently low output ripple regardless of battery voltage variation. The proposed chip fabricated in 0.18-mum BCD consumes a quiescent cur-rent of only 217 nA and offers the output recovery time of ≤ 1 ms at a zero-to-full load transition. The measured efficiency was 86% with a load of 500 muA and 55% even with an ultra-light load of 1 muA.

High-Efficiency Multilevel Multimode Dynamic Supply Switching Modulator for LTE Power Amplifier

A high efficiency multilevel multimode (MLMM) dynamic supply switching (DSS) modulator using a single-inductor multiple-output (SIMO) dc–dc converter is presented to improve the efficiency of power amplifiers (PAs) for a 900 MHz band. The efficiency improvements from the DSS PA were analyzed according to the number of switching levels using the probability density function of the modulation signal. Based on the analysis results, the proposed DSS modulator was configured to give four optimal switching levels in relation to efficiency improvement of the overall DSS PA, efficiency of the modulator itself, and circuit complexity. The SIMO dc–dc converter, which newly adopts a duty skip method, was designed to generate multiple dc voltages. In addition, the four voltage levels were reconfigured according to the average output power to further improve the efficiency of the PA through a wide output power range. The proposed MLMM DSS PA was fabricated using a 0.18 $\mu$ m CMOS process. For 16-quadrature amplitude modulation long-term evolution (LTE) signals, the proposed MLMM DSS modulator exhibited an efficiency of no less than 80% in the supply power range of 0.1–1 W. Using LTE signal with 10 MHz and peak to average power ratio of 7.58 dB, the MLMM DSS PA showed power added efficiency (PAE) of 41.7% at an average power of 25 dBm with an adjacent channel leakage ratio (ACLR) of $-$ 30 dBc.

Single Inductor Multiple Output Auto-Buck-Boost DC–DC Converter with Error-Driven Randomized Control

We propose a single inductor multiple output (SIMO) auto-buck-boost DC–DC converter with error-driven randomized control (EDRC). The conventional controls in a SIMO DC–DC converter supply power to outputs that have been selected in a sequential order. Furthermore, they control the inductor current levels at either edge of a switching period in a steady state to be at the same level to alleviate cross-regulation. However, this limits the flexibility of the converter to respond to changes in load requirements. A sequential selection of light loads results in these loads being selected more often than a load demand, degrading the efficiency for light loads. In addition, limited flexibility leads to delayed responses. This paper introduces an auto-buck-boost topology that selects outputs based on output errors, and instantaneously adjusts the inductor current level. Moreover, we propose a technique for allowing any output to avoid selection when all outputs are fully supplied. The proposed EDRC scheme achieves improvements in efficiency in regards to light loads, cross-regulation, and output driving capability.

Single-Inductor Multiple-Output (SIMO) Buck Hybrid Converter for Simultaneous Wireless and Wired Power Transfer

In this article, a nonisolated single-inductor multiple-output (SIMO) dc–ac buck-derived hybrid converter for simultaneously driving multiple independent ac and dc loads using only a single inductor in the power stage is proposed. Compared with the prior art, the proposed SIMO-based hybrid converter carries the conspicuous advantages of 1) a simple, compact, and low-cost implementation of the power stage; 2) reduced component count; 3) high power density; 4) increased output power, better flexibility, and scalability in realizing any combinations of ac and/or dc loads; and 5) high efficiency. By operating in pseudocontinuous conduction mode (PCCM), this hybrid converter enables wireless and wired power transfer at medium-power level without cross regulation. In practice, this converter can serve as a Qi-compliant hybrid charger with multiple transmitting coils and universal serial bus (USB) charging ports for quick and concurrent multidevice charging. A hardware prototype of a single-inductor four-output (SIFO) buck-derived hybrid converter is constructed. The experimental results show that the SIFO converter produces a rated output power of 20 W and a maximum efficiency of around 88%.

Soft-Switching Techniques for Single-Inductor Multiple-Output LED Drivers

Although a plethora of prior-art single-inductor multiple-output (SIMO) light-emitting diode (LED) drivers have been reported, they remain inadequate for resource-constraint drone applications due to compromised power efficiency and weight. This article proposes a monolithic SIMO red–green–blue–white LED driver that features high power efficiency and light weight. The former is obtained by employing our proposed soft-switched cross-current-eliminated controller and proposed on-chip bidirectional current sensor. The latter is achieved by means of employing a tiny inductor attributed to boundary conduction mode and high switching frequency. To the best of authors’ knowledge, the proposed SIMO LED driver is the first-ever design that features soft switching for all power switches and innate elimination of current cross-regulation. In comparison with the state-of-the-art designs listed in the benchmark table, the proposed design features the highest power efficiency of 96.2%, smallest output inductor of 820 nH, shortest LED current settling time of 900 ns, and the highest switching frequency of 2 MHz.

A Single-Inductor Multiple-Output Buck/Boost DC–DC Converter With Duty-Cycle and Control-Current Predictor

A single-inductor multiple-output (SIMO) buck/boost dc–dc converter with average-current control is presented in this article. With the proposed duty-cycle and control-current predictor, fast and robust reference tracking of inductor current is achieved. The conventional charge-balance method is modified together with an auto-tuning-divider-based duty generator to release the cross-regulation to the last channel. Moreover, an anti-right-half-plane zero method is also proposed to suppress cross-regulation during large loading transient when the SIMO dc–dc converter operating in the boost mode. The proposed SIMO buck/boost dc–dc converter has four output channels which are adaptive to both boost and buck operations and is implemented in a standard 0.35-μm CMOS process. Measurement results show that the proposed dc–dc converter achieves a peak efficiency of more than 89% at a total output power of about 0.5 W, load transient's response time of less than 40 μs, cross-regulation within 0.05 V/A when a 300-mA loading transient is applied to a boost channel.

Voltage‐mode hysteretic control techniques for high‐current single‐inductor multiple‐output switching regulators

In this Letter, two comparator-based voltage-mode hysteretic controller designs are proposed to enhance dynamic response for single-inductor multiple-output (SIMO) switching converters to minimise over-/under-shoot voltages due to self- and cross-regulations in fast load transients, especially with high output power and large current steps. The proposed converters are designed and simulated in a 65 nm CMOS process with standard I/O devices. With the proposed techniques, the output voltage fluctuations, including steady-state voltage ripples and over-/under-shoot voltages due to self- and cross-regulations during a 1.8 A load transient in 1 ns, are kept within 60 mV. The proposed converter delivers more than 3 A maximum load current per output and a maximum total output power above 6 W, with a peak efficiency above 90%. Compared to state-of-the-art SIMO converters, this work achieves a significantly higher output power capacity and faster dynamic response thus smaller self- and cross-regulations within 0.033 mV/mA.

Novel modulation method for torque ripple suppression of brushless DC motors based on SIMO DC–DC converter

In this paper, a novel modulation method is proposed for the torque ripple suppression of a brushless DC motor (BLDCM) during both the commutation period and the speed regulation period. The main sources of torque ripple are the imbalance current during commutation and the PWM during speed regulation. A single-inductor multiple-output (SIMO) Buck DC–DC converter is adopted to generate input voltage for the inverter driver of a BLDCM. During the commutation period, the input voltage of an inverter can be adjusted to four times the back electromotive force (EMF), which suppresses the torque ripple caused by imbalance commutation current. Meanwhile, by changing the output voltage of a SIMO DC–DC, the speed of a BLDCM can be regulated without PWM on the inverter switches, which also suppresses the torque ripple. A control algorithm is applied on a Field Programmable Gate Array (FPGA), and the proposed BLDCM drive prototype is fabricated and tested. Measurement results show that with the proposed speed regulation strategy, the torque ripple is suppressed from 33.3% to 20.1%, and that with the proposed suppression strategy in commutation, the torque ripple is suppressed further to 5.3%.

Single-Inductor Multiple-Output Inverter With Precise and Independent Output Voltage Regulation

In this article, a single-inductor multiple-output (SIMO) inverter with precise and independent output voltage regulation is presented. This SIMO inverter with controllable output voltage enables each individual transmitting coil in a multicoil wireless power transfer system to be driven by a tightly regulated constant-voltage source. This is especially useful for the wireless charging of rechargeable batteries when they act as a constant-current (CC) load in the CC charging phase. By precisely regulating the source voltage at each transmitting coil, a constant load current at the corresponding receiver can be achieved at a particular resonant frequency and mutual inductance between the transmitting and receiving coil. The closed-form expressions of the sinusoidal-like output voltage and resonant inductor current as a function of the duty ratio of the main switch are also analytically derived. An experimental prototype of a single-inductor three-output inverter with a single time-multiplexed analog-based controller employing the type II compensation is implemented. It is experimentally verified that the individual ac outputs can be accurately and independently controlled. The maximum error between the target and measured peak voltage values is shown to be within 1.14%.

A High-Power LED Driver Based on Single Inductor-Multiple Output DC–DC Converter With High Dimming Frequency and Wide Dimming Range

This article proposes an LED driver circuit which is wide-range continuous dimmable for high power lighting application. The proposed LED driver is based on single-inductor–multiple-output (SIMO) dc–dc converter. A pulsewidth modulation (PWM) control strategy is applied on the LED driver to control the brightness of LEDs flexibly and precisely, with which the dimming frequency can be increased significantly, and the dimming ratio for all branches can be adjusted separately. PWM dimming would cause the inductor current overshooting when dimming switch alters from off to on , which makes the LED current varying. To suppress the inductor current overshooting, a sampling–holding circuit is adopted in the feedback loop of the proposed LED driver. A prototype of the proposed LED driver is fabricated and tested. The measurement results show that the dimming frequency can be increased to 10 kHz, the dimming ratio can be set from 5% to 100% with a minimum pulsewidth of 5 $\mu$ s, and the inductor current overshooting is suppressed from 150% to approximately 0%. The proposed LED driver can output more than 80 W and achieve a conversion efficiency of 97%.