Digital Charge Balance Controller to Improve the Loading/Unloading Transient Response of Buck Converters (original) (raw)
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International Journal of Circuit Theory and Applications, 2012
Multi-cell converters have been developed to overcome shortcomings in usual switching devices. The control system in these circuits is twofold: first, to balance voltages of the switches and second to regulate the load current to a desired value. However, with a purely proportional controller, the system presents a static error. With a PI controller the static error is annihilated, but at the expense of shortening the stability region and increasing settling time. In this work, a zero static error dynamic controller for a two-cell DC-DC buck converter is designed. To achieve zero current error, we propose a generalized scheme of a dynamic controller. Then, using nonlinear analysis and Lyapunov stability theory and bifurcation prediction tools, we prove that zero static error is achieved. The proposed controller outperforms the PI controller in terms of settling time in the presence of saturating effect during the start-up transients. Numerical simulations in the form of time domain waveforms and bifurcation diagrams from switched circuit-based model are presented to confirm our theoretical results.
Fast Transient Digitally Controlled Buck Regulator with Inductor Current Slew-Rate Boost
A step-down (buck) switching converter architecture that makes use of switched capacitors to improve the transient response is presented. Using the proposed architecture, the transient response is improved by a factor of two or more in comparison to the theoretical limits that can be achieved with a basic step down architecture. The architecture presented in this paper can be used for both analog and digitally controlled topologies. Simulation results of a 1.8V, 15W, 1MHz digitally controlled step down converter with a 12mV ADC resolution and a 2ns DPWM resolution are presented.
IEEE Power Electronics Specialists Conference, 2008. PESC 2008., 2008
In this paper a novel digital controller and modified buck converter for improving heavy-to-light load transient response of low-power low-voltage dc-dc converters is introduced. The system is primarily designed for point-of-load (PoL) converters providing low regulated voltages for digital loads. In conventional buck topologies, the low output voltage, often below 1 V, severely limits the inductor current slew rate during the transients. To overcome this physical limitation, a modification is introduced whereby during heavy-to-light transients, the inductor current is, by the means of two extra switches, steered into the source and at the same time, the slew-rate of the current is significantly increased. The steering action is governed by a digital controller. The effectiveness of the system is verified on an FPGA-controlled, 12 V to 0.9 V, 10 W, experimental prototype. The results show that the steered-inductor digitally controlled buck converter has much shorter settling time and provides 2.8 times smaller overshoot than the conventional buck.
IJERT-Digital Control of DC -DC Buck Converter
International Journal of Engineering Research and Technology (IJERT), 2014
https://www.ijert.org/digital-control-of-dc-dc-buck-converter https://www.ijert.org/research/digital-control-of-dc-dc-buck-converter-IJERTV1IS7038.pdf The paper describes the design and implementation of a digital controller for DC-DC Buck Converter. Digital controllers are increasingly replacing their analog counterparts due to its improved flexibility, easier integration, programmability, reduced design time, size, cost and improved reliability. Switching devices are selected based on the power handling capability and high frequency switching. Voltage mode control is used in order to get faster response. Proposed DC-DC Buck Converters are controlled using PD controller and Full State Feedback Controller designed using Pole Placement technique. The PD controller has been implemented on an Atmega32-8 bit Microcontroller. The Full State Feedback controller has been simulated in MATLAB/SIMULINK.
Modeling and Design Rules of a Two-Cell Buck Converter Under a Digital PWM Controller
IEEE Transactions on Power Electronics, 2008
In this paper, we give a detailed analytical study of a two-cell dc-dc buck converter. We analyse the dynamics of the system by using a discrete time modelling approach and considering a digital controller. This controller includes a dynamic compensator in the form of a digital integrator for the output variable regulation. The discrete time model for the whole system is used to predict the instability of the system when some design parameters are varied. To facilitate the design, an approximated closed form discrete time model is derived in the form of a recurrence equation which accurately describes the dynamical behavior of the system. The Jury test is applied to the characteristic polynomial in order to obtain stability boundaries in the design parameter space. Some design rules to obtain optimal transient behavior are also given. Numerical simulations and experimental measurements confirm the theoretical predictions.
An Adaptive Digital Compensation Design For Buck Converter Topology
This paper presents a digital type III compensator that needs no calculation made by a designer. First an analog type III compensator is designed for a buck converter and based on it the digital model is obtained. Both the analog and digital approaches are simulated in PSIM and the digital compensator is written in a Microchip dsPIC for experimental results. The dynamic response of these controllers under input voltage change and load current variations are presented.
Digital Multimode Buck Converter Control With Loss-Minimizing Synchronous Rectifier Adaptation
IEEE Transactions on Power Electronics, 2000
This paper develops a multimode control strategy which allows for efficient operation of the buck converter over a wide load range. A method for control of synchronous rectifiers as a direct function of the load current is introduced [1]. The function relating the synchronous-rectifier timing to the load current is optimized on-line with a gradient power-loss-minimizing algorithm. Only low-bandwidth measurements of the load current and a power-loss-related quantity are required, making the technique suitable for digital controller implementations. Compared to alternative loss-minimizing approaches, this method has superior adjustment speed and robustness to disturbances, and can simultaneously optimize multiple parameters. The proposed synchronous-rectifier control also accomplishes an automatic, optimal transition to discontinuous-conduction mode at light load. Further, by imposing a minimum duty-ratio, the converter automatically enters pulse-skipping mode at very light load. Thus, the same controller structure can be used in both fixed-frequency pulsewidth modulation and variable-frequency pulse-skipping modes. These techniques are demonstrated on a digitally-controlled 100-W buck converter.
Turkish Journal of Electrical Engineering and Computer Sciences, 2018
One type of DC-DC converters is dual transistor forward converter. In this article, a low-cost architecture of a digital controller for dual transistor forward converter is presented. This architecture is designed by using the finite set model predictive control technique. Based on this approach, a low-cost fixed-point arithmetic architecture with minimum functional units is presented to find the optimum switching time at each sampling point. Charge balance control method is utilized to improve the dynamic performance of the transient response. The proposed architecture is implemented and realized by using a field-programmable gate array (FPGA) platform to evaluate the precision of the fixed-point calculation. Several cases for different loading conditions for different word lengths are practically investigated and the proposed digital controller shows a minimum voltage overshoot-undershoot and short settling time under load-changing situations. Compared with other controllers, the presented work provides a better dynamic performance and lower implementation cost.
A Novel Linear-Non-Linear Digital Control for DC/DC Converter with Fast Transient Response
Twenty-First Annual IEEE Applied Power Electronics Conference and Exposition, 2006. APEC '06., 2006
In this paper, a digitally controlled multi-module DC-DC converter with fast transient response, based on a linearnon-linear control is presented. The proposed digital control improves the stability of the system, cuts off the effects of limitcycle and reduces the recovery time, by making the "effective" bandwidth of the system independent of the bandwidth of the linear control loop and limits, at the same time, output voltage variations. The novel digital control is AVP-compatible and halves the recovery time. Preliminary hardware tests on a single phase step-down converter are reported. The experimental results match simulation ones, obtained by modelling system with Matlab/Aldec mixed environment. Implemented system shows fast transient responses comparable to analog controls.