Single-inductor Dual-output Buck Converter Research Articles

Stability Analysis for Hybrid Conduction Mode Single-Inductor Dual-Output DC–DC Converter With Dynamic-Freewheeling Control and Dynamic Ramp-Compensation

Hybrid conduction mode (HCM) is gradually applied in single-inductor dual-output (SIDO) dc-dc converter as its advantages of reducing switching loss and minimizing cross-regulation. However, it shows that the circuit parameters will affect the stability and restrict its operation range, which causes the converter to operate in non-HCM and these advantages are lost. In this paper, to figure out this phenomenon, eight different operation modes of the HCM SIDO buck converter are analyzed. On this basis, a three-dimensional discrete-time model, which is suitable for variable-frequency control, is established. And then, the effect of output capacitors and its equivalent series resistances (ESRs), load resistors, input voltage and output voltages, constant turn-off time on the stability is discussed. The study results show that the stability and operation mode is sensitive to the difference circuit parameters and control parameters. In addition, the dynamic ramp-compensation based on inductor current is proposed and analyzed for stabilization control, which can broaden the stable operation range of this converter. Finally, experimental results validate the accuracy of proposed theoretical analysis.

Dynamic Freewheeling Control for SIDO Buck Converter With Fast Transient Performance, Minimized Cross-Regulation, and High Efficiency

Slow load transient performance, potential cross-regulation, and low efficiency are the major drawbacks for pseudocontinuous conduction mode single-inductor dual-output (SIDO) dc–dc converters. To overcome these drawbacks, this article proposes a voltage-ripple (VR)-based dynamic freewheeling (DF) control technique for hybrid conduction mode (HCM) SIDO buck converter. With the employment of VR controller, the proposed control technique improves the load transient performance significantly. As the fast recovery during load transition, the cross-regulation is minimized. Additionally, due to the DF controller, the freewheel current value automatically updates in each switching period, which can improve the efficiency of the HCM SIDO buck converter, especially under the light load conditions. Finally, the proposed converter has been verified through experimental results. The transient response time on 0.5 A load change takes only 1–2 switching periods. No observable cross- regulation is found and maximum efficiency of 92.03% is achieved. Finally, the experimental waveforms are presented to verify the theoretical research.

Modeling and Analysis of Voltage Ripple-Controlled SIDO Buck Converter in Pseudo-Continuous Conduction Mode with Limited Cross-Regulation and Fast Load Transient Performance

Typical voltage mode-controlled DC–DC converters with single-inductor dual-output (SIDO) in pseudo-continuous conduction mode (PCCM) have slow load transient performance, and cross-regulation still exists between their two outputs. For the purposes of suppressing the cross-regulation and improving the load transient performance, a voltage ripple control technique for a PCCM SIDO buck converter is proposed in this study. A description of the PCCM SIDO buck converter and the voltage ripple control technique is provided in detail. In addition, the small-signal model was established, and the cross-regulation was further compared by Bode plots, as well as the load range and the power losses being analyzed. The cross-regulation and load transient performance of the voltage ripple-controlled PCCM SIDO buck converter was studied and compared with the conventional voltage mode-controlled. Using the proposed voltage ripple control for PCCM SIDO buck converters, we found no cross-regulation or rapid load transient behavior, which was validated by experimental results.

A Capacitor Current and Capacitor Voltage Ripple Controlled SIDO CCM Buck Converter With Wide Load Range and Reduced Cross Regulation

It is well-known that the ripple control technique benefits from fast load transient response and small cross regulation for single-inductor dual-output (SIDO) dc–dc converter. However, existing capacitor current ripple (CCR) controlled SIDO buck converter suffers from incomplete operation state and single switching path. Thus, it has a limited stable load range. In order to extend the stable load range and suppress cross regulation of SIDO buck converter in continuous conduction mode (CCM), a novel ripple control technique, called as capacitor current and capacitor voltage ripple (CCVR) control, is proposed in this article. The operation principle of the proposed CCVR controlled SIDO CCM buck converter is presented, and its discrete iterative map model is established. Furthermore, the stability and stable load range have been discussed by using bifurcation diagrams. Based on the established small signal model, Bode plots are given to show the performance in suppressing cross regulation. Finally, simulation and experiment results are provided to verify the theoretical analysis. It shows that the proposed CCVR control technique can be applied to SIDO CCM buck converter to extend its stable load range and suppress its cross regulation.

A PAIM control scheme on hybrid system with its application on SIDO buck converter

This work concerns the stability and stabilization problems on switched impulsive positive system. A single-inductor dual-output (SIDO) buck converter is employed for investigation and evaluation, which is a typical switched system. Then, considering the complex dynamical behaviour, a novel control scheme applying proportional with asynchronous integral and memory (PAIM) control algorithm is developed to guarantee not only the positivity but also the exponential state convergence with L1-gain performance of the hybrid system with unexpected complexity. Numerical results are illustrated to verify this proposed development.

Effect of Circuit Parameters on the Stability and Boundaries of Peak Current Mode Single-Inductor Dual-Output Buck Converters

Peak current mode (PCM) control has been widely used for the control of switching dc–dc converters due to its excellent transient performance. With the development of single-inductor dual-output (SIDO) dc–dc converters, PCM control technique is introduced to the control of SIDO dc–dc converters. Conventional PCM buck converter has only one reference current, with two inductor current borderlines are used to divide the operation modes of inductor current. However, PCM SIDO buck converter has more inductor current borderlines as it has one more reference current than that of PCM buck converter. In this paper, inductor current borderlines of PCM SIDO buck converter are investigated, and unified discrete iterative model of PCM SIDO buck converter is established. The effect of the difference of reference currents, initial inductor current and input voltage on the stability of PCM SIDO buck converter has been discussed by using bifurcation diagrams. The study results show that the stability of PCM SIDO buck converter is sensitive to the difference of reference currents, initial inductor current and input voltage. The stability boundary of the difference of reference currents, stability region of initial inductor current, and stability boundary of input voltage are derived. Lyapunov exponent and experimental results are carried out to verify the theoretical analysis results.

0.6-μm CMOS-Switched-Inductor Dual-Supply Hysteretic Current-Mode Buck Converter

Microsystems can sense, process, and transmit information between nodes across hospitals, factories, and homes that can save lives, energy, and money. Unfortunately, supplying power with so much embedded functionality is challenging, because while some functions can survive higher noise levels and voltages, others cannot. Power supplies must therefore satisfy several independent outputs without consuming much power or occupying much space. A switched inductor is attractive in this respect because, with only one off-chip inductor, the system can output 80%–90% of the power it draws. Regulating multiple outputs with one inductor, however, links several feedback loops and their reactions to individual and combined loads. The sacrifice for this is usually accuracy in the form of response time. The single-inductor dual-output buck converter presented here uses a hysteretic current loop for this reason: to accelerate the response of the loops used to regulate the outputs. The 0.6-μm CMOS prototype supplies 70 and 50 mA to 1.5- and 2.5-V outputs with 80%–88% power-conversion efficiency and responds to 45–65 mA load dumps within 3.8 μs to keep 1.5 V within ±5% and 2.5 V within ±7%.

A Ripple Control Dual-Mode Single-Inductor Dual-Output Buck Converter With Fast Transient Response

A novel integrated single-inductor dual-output buck converter based on the ripple control technique is presented, which can provide two independent output voltages (1.2 and 1.8 V) only using one inductor. The peak current common-mode and ripples compare differential-mode are adopted to improve the system transient response. The converter can automatically switch between pulsewidth modulation and pulse-skip modulation to improve the light load conversion efficiency. The proposed converter has been fabricated in a 0.18 μm 1P6M CMOS process. The experimental results show the transient response time is about 10 μs and the cross-regulation is less than 0.05 mV/mA while the load current suddenly changes 200 mA. In general, the conversion efficiency at light load is above 86% and the peak efficiency at the full load can achieve 93.5%.

Monolithic quasi-sliding-mode controller for SIDO buck converter with a self-adaptive free-wheeling current level

An analog implementation of a novel fixed-frequency quasi-sliding-mode controller for single-inductor dual-output (SIDO) buck converter in pseudo-continuous conduction mode (PCCM) with a self-adaptive freewheeling current level (SFCL) is presented. Both small and large signal variations around the operation point are considered to achieve better transient response so as to reduce the cross-regulation of this SIDO buck converter. Moreover, an internal integral loop is added to suppress the steady-state regulation error introduced by conventional PWM-based sliding mode controllers. Instead of keeping it as a constant value, the free-wheeling current level varies according to the load condition to maintain high power efficiency and less cross-regulation at the same time. To verify the feasibility of the proposed controller, an SIDO buck converter with two regulated output voltages, 1.8 V and 3.3 V, is designed and fabricated in HEJIAN 0.35 μm CMOS process. Simulation and experiment results show that the transient time of this SIDO buck converter drops to 10 μs while the cross-regulation is reduced to 0.057 mV/mA, when its first load changes from 50 to 100 mA.

Closed Loop Analysis of Single-Inductor Dual-Output Buck Converters with Mix-Voltage Conversion

A single-inductor dual- output (SIDO) buck converter has recently found applications in hand- held battery-powered electronic devices. The circuit operation and the functional interdependencies among basic converter parameters such as dc gains, transistor duty cycles, and load current levels are much more complicated than those of the single- output counterpart. In this project, a rigorous analysis was conducted to develop dc equations in steady state operation for SIDO converters. More importantly, from the analysis results, a possibility of a new mode of operation, dubbed mix-voltage operation, will be pointed out. In the so-called mix- voltage operation, the converter is capable of working even when the input is lower than one of the two output voltages. In the past, a SIDO buck converter has been used for providing pure-buck outputs, i.e., both output voltages are lower than the input voltage. Therefore, this possibility not only opens up new applications but also extends the operating battery range in existing applications. Experimental results confirmed the dc equations and the mix-voltage conversion of SIDO buck converters.

Design and implementation of a digitally controlled single‐inductor dual‐output (SIDO) buck converter

SUMMARYThis paper describes design and implementation of a digitally controlled single‐inductor dual‐output (SIDO) buck converter operating in discontinuous conduction mode. This converter adopts time‐multiplexing control in providing two independent output voltages using only an inductor. The design issues of the digital controller are discussed, including static and dynamic characteristics. Implementation of the controller, a modified hybrid digital pulse width modulator and a single look‐up table are developed. The digital controller was implemented on a field‐programmable gate array‐based control board. Experimental results demonstrating system validity are presented for a SIDO buck converter with nominal 3.6 V input voltage, and the outputs are regulated at 1.8 and 2.2 V. Copyright © 2012 John Wiley & Sons, Ltd.

Mix-Voltage Conversion for Single-Inductor Dual-Output Buck Converters

A single-inductor dual-output (SIDO) buck converter has recently found applications in hand-held battery-powered electronic devices. The circuit operation and the functional interdependencies among basic converter parameters such as dc voltage gains, transistor duty cycles, and load current levels are much more complicated than those of the single-output counterpart. In this paper, a rigorous analysis was conducted to develop dc equations in steady-state operation for SIDO converters. More importantly, from the analysis results, a possibility of a new mode of operation, dubbed “mix-voltage” operation, will be pointed out. In the so-called “mix-voltage” operation, the converter is capable of working even when the input voltage is lower than one of the two output voltages. In the past, a SIDO buck converter has been used for providing “pure-buck” outputs, i.e., both output voltages are lower than the input voltage. Therefore, this possibility not only opens up new applications but also extends the operating battery range in existing applications. Experimental results confirmed the dc equations and the “mix-voltage” conversion of SIDO buck converters.