Transient Response Improvement of DC to DC Converter by Using Auto-tuned PID Controller

In this paper, average power balance control (APBC) scheme is designed and analyzed for a buck converter. The proposed scheme consists of two control loops, the fast inner current loop uses sliding mode control (SMC) and outer voltage loop uses the average power balance algorithm (APBA), which contains average power balance equation (APBE) and PI controller. The existence condition of SMC is derived using Lyapunov stability theorem such that the stable tracking performance can be ensured under occurrence of system uncertainties. The proposed APBC scheme is modelled and simulated using MATLAB / SIMULINK. The effectiveness of APBC in terms of voltage tracking, transient response and robustness to uncertainties in parameters are verified by simulation results.

Existing design methods under voltage mode control (VMC) are carried out using perturbed linear small-signal models (SSMs), and the design works fine in a synchronous buck converter if the control bandwidth <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$f_{c}$</tex> is set to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$f_{c}\leq f_{\text{sw}}/10$</tex> , where <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$f_{\text{sw}}$</tex> is the switching frequency. In this paper, small-signal based tuning of a practical PID controller and a type-III compensator is discussed in a VMC buck converter, and the model validity aspects are presented using simulation results. For individual cases, the closed-loop bandwidth <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$f_{c}$</tex> is limited to a fraction of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$f_{\text{sw}}$</tex> , and the performance limit under VMC is due to the model limit and because of ignoring ripple information. Further, a nonlinear PID controller tuning method is proposed in a VMC buck converter using large-signal models. This can achieve proximate time optimal recovery, in which the closed-loop performance can be improved up to the slew rate limit of the converter. Stability and robustness analysis are presented. A comparative study is considered using simulation results to demonstrate load transient performances using small-signal and large-signal based design approaches. Finally, the proposed large-signal based PID tuning is validated experimentally in a VMC buck converter.

DC-DC converters are extensively used for switched mode power supplies. Hence, this chapter presents a design, modelling and hardware implementation of a digitally controlled system and its application to DC-DC buck converter being interfaced with Texas Instruments DSP TMS320F2812 controller for voltage control mode. ADC, compensator and digital PWM are the main building blocks that appears in digital controller design. Conventionally, analog controller is popular to get the desired output voltage in DC-DC converters, whereas, digital controllers offer high speed arithmetic and high resolution. Analog PI controller design approach is reviewed and the digital PI controller design is being implemented in this chapter. Digital control has been applied using standard frequency responses with design by emulation approach. Modulation delay in digital control is very critical while designing for fast control loops. Therefore, this chapter also introduces discrete time modelling of synchronous buck converter from practical standpoint considering feedback loop delays. Whereas, this chapter illustrates PI digital controller design methodology, hardware implementation and experimental verification. Experimental results have been taken from a closed loop 18W buck converter. The transient and steady state performance of the converter using PI controller are also presented with appropriate simulation and hardware results.

In this paper, a review of the common techniques used for high step-down dc-dc voltage conversion is presented. First, the limitations of conventional buck & synchronous rectifier buck converters used for high step down dc-dc voltage conversion which include narrow duty cycle, high voltage stress, large ripple and low efficiency are briefly discussed. Then various topologies of non-isolated step-down dc-dc converters are reviewed and discussed. The topologies/techniques used for high step down dc-dc conversion are divided into various groups which include interleaved, quadratic, tapped, switched capacitor, switched inductor, coupled inductor, multi level and buck converter with three state switching cells. Each group of converters is briefly discussed, main circuit structure of each topology is given and their features and limitations are given. Finally a comparison of all the discussed topologies is carried out based on some common features.

This paper presents a control scheme for DC-DC converters designed for battery operated systems. These systems require very high efficiency to prolong the battery life The inductor peak current is maintained constant either by oscillator on/off time control or monoshot on time control. But these types of control require a fixed and accurate value of inductor and they require preprogramming of monoshot/oscillator. The proposed control scheme uses a peak current detector for the inductor peak current detection. Therefore it rules out maintaining a very precise value of inductor size and any kind of preprogramming. A design and its implementation have been carried out in a 1.5 /spl mu/ BiCMOS process and both simulation and experimental results are presented.

DC-DC converters are being widely used in electrified transportation systems. It has been proven that chaos in this family of converters can lead to instability. This digest presents a mathematical study of bifurcation and chaos in PWM- controlled DC-DC buck converters. The derivation of discrete time models for the period -1, period -2, period -4 and period -8 orbits are demonstrated. A practical circuit has been constructed and tested, and the experimental results verified the validity of the theoretical analysis.

In this paper, we address the control problem of the DC-DC buck converter with perturbed input source and load current. A new nonlinear control method is proposed which can ensure to generate a bounded control signal corresponding to the Pulse-Width Modulation (PWM) duty ratio in the range of [0, 1]. The overall system stability is rigorously analyzed using the Lyapunov second method. PSPICE based Monte carlo simulation is conducted to further validate the effectiveness of the proposed new design in the presence disturbances as well as system parametric uncertainties.

In the recent years, Buck converters have been widely involved in a variety of the everyday applications such as smartphones and PCs. Buck converters can provide better and steadier performance when integrating a control system in the design. Therefore, it is interesting to work on this integration and gain the required efficiency in term of the gained voltage. In this paper, PID controller is adopted to control the output voltage of the Buck converter. An optimization is achieved on the performance of the Buck converter using two bio-inspired algorithms namely, Particle Swarm Optimization (PSO) and Artificial Bee Colony (ABC). The voltage controlled Buck converter system is simulated using Matlab environment to validate the proposed PID controller system. In this study, the voltage regulation process of Buck converter is investigated based on many working disturbances such as the change in the supply voltage, reference voltage, and load resistance in order to verify the robustness of the proposed PID controller. Finally, the feedabck voltage control system of the Buck converter is implemented experimentaly in real-time to validatde the simulated PID controller.

This paper presents an auto-tuned, fuzzy logic controller. It starts with a simple fuzzy PID controller definition which is a useful nonlinear PID controller. Then an analysis of the fuzzy nonlinear relationship is given and some features of the fuzzy controller are discussed. The scaling factors of the fuzzy PID controller are associated with PID controller parameters. Thirdly, a practical approach to auto-tuning the fuzzy PID controller is proposed by using Astrom and Hagglund's (1984) auto-tuning technique for PID tuning. Last, experiments on the auto-tuned fuzzy PID controller are conducted and compared to regular PID controllers.

This paper presented a comparative study in function reliability between dc-dc converters used in power LED. Between dc-dc converters more used to power LED are the Buck and Flyback converter, because the Buck provides a lower output voltage than the input, and in the case of flyback has galvanic isolation. The study has objetive to determine the reliability obtaining the failure rate of the system and the average time when failures occurs, because the LED driver must have an average life similar to the LED lamp. The reliability analysis is based in the standard MIL-HDBK-217, for this study performed was used a LED load of 54.6 W in both converters. The results have shown that the buck converter has a lower failure rate and a higher mean time between failures, therefore has a longer useful life.

Power supplies for last generation of microprocessors and DSPs must present low output voltage and fast transient response. The linear-non-linear control (LnLc control) was presented as a solution to improve the transient response in DC-DC buck converters. However, once the LnLc control has been analyzed, other important performances have been found such as, improving the stability of the system, improving the efficiency, reducing of the recovery time, making independent the bandwidth and the switching frequency; reaching all these performances with an easy implementation. In this paper, the features of the linear-non-linear control are described. It will be shown, how the LnLc improves the stability of a DC-DC buck converter modifying the open loop gain and phase as a function of the load current steps. To show this behavior the control transfer function (G/sub LnLc/) has been deduced. Several experimental results have been obtained in a synchronous rectifier buck converter to check its behavior. Thus, the novel LnLc control has been compared with the conventional voltage control under different conditions. Finally, the control transfer function has been obtained experimentally.

This paper presents a comparison between relay feedback tuning and other controller tuning methods for a digitally controlled DC-DC buck converter operating in continuous conduction mode. In the first method, a relay feedback test is used to obtain ultimate gain and period measurements experimentally. PI and PID controllers are then tuned according to the classic Ziegler-Nichols formulae. In the second and third method, a converter model is developed based on experimental identification and analytical derivation, respectively. PI and PID controllers are then designed through optimization of an integral performance criterion applied to the simulated step response. Experimental tests show that all three approaches to controller tuning provide comparable and acceptable results, but the simplicity of the approach based on the relay feedback test makes it a viable alternative to offline-tuned optimal controllers given the ability of the former to retune the controller to adapt to system changes. Results also suggest that with some improvements to the test and tuning rules, a well-tuned controller may be produced with reasonable computational effort in the auto-tuning schema.

This paper proposes a new soft switching synchronous Buck converter to provide complete ZVS conditions for both high and low side MOSFETs under the light- or no-load, as well as full load conditions. In the continuous conduction mode (CCM) with a heavy load current condition, the high side MOSFET is generally turned ON while the body diode of low side MOSFET is in the conducting condition in a dead-time region, which causes switching loss in the high side MOSFET. A proposed soft-switching Buck converter consists of the conventional synchronous Buck converter with additional L and C. By using a resonance with the additional L and C, the inductor current in CCM can be effectively commutated from the low side body diode to the high side body diode of the two MOSFETs during the dead time region. The detailed modes of operation with experimental results are provided to verify performance.

This paper presents a fuzzy auto-tuning PID controller to improve the motor performance in a low-cost fault tolerant motor drive of electric vehicles. The fault tolerant control system considered for the motor drive is specifically designed for the inverter power semiconductor devices faults. The drive control strategy is based on the well-known V/F control method. Normally fault tolerant schemes allowing nonstop operation of the motor drive during the fault condition result in poor motor performance (e.g. two leg operation of the inverter). Because of the system complexity and low motor performance in fault conditions, a fuzzy tuner is proposed to readjust the PID control parameters. The proposed tuner leads to an overall acceptable system performance in both transients and steady-state conditions. To evaluate the controller tuner used in the fault condition of the motor drive, a fuzzy tuner is applied and programmed. Simulation results are obtained with both classic and fuzzy tuned controller. The results show that the motor performance parameters such as efficiency and power factor have been improved with the tuned PID controller compare to classic controller.

Recently techniques have been developed for the calculation of PID controller gains based on frequency domain approximation using least squares methods. This paper presents methods for auto-tuning PID controllers based on limited frequency response information, using a weighted least squares approximation to a desired open loop transfer function. Automated techniques used for the calculation of this desired open loop transfer function are described, and simulation results of the auto-tuner are presented. It is shown that the auto-tuner performs well, and effectively designs PID controllers in situations where other auto-tuning techniques have not, including the case of mildly oscillatory systems.