Yuto Adachi

Bio: Yuto Adachi is an academic researcher from University of Electro-Communications. The author has contributed to research in topics: Digital control & Power factor. The author has an hindex of 2, co-authored 6 publications receiving 14 citations.

Robust digital control for an LLC current-resonant DC-DC converter

Abstract: If a pulse frequency, a load resistance of an LLC current-resonant DC-DC converter are changed, the dynamic characteristics is varied greatly, that is, the LLC current-resonant DC-DC converter has non-linear characteristics. In many applications of DC-DC converters, loads cannot be specified in advance, and they will be changed suddenly from no loads to full loads. A DC-DC converter system used a conventional single controller cannot be adapted to change dynamics and it occurs large output voltage variation. In this paper, a robust digital controller for suppress the change of step response characteristics and variations of output voltages in the load sudden changes is proposed. Experimental studies using a micro-processor for the controller demonstrate that this type of digital controller is effective to suppress the variations.

Design of approximate 2DOF digital controller for interleaved PFC boost converter

Abstract: In general, a current conduction mode boost converter is used for active PFC (Power Factor Correction). In a PFC boost converter, if a duty cycle, a load resistance and an input voltage are changed, the dynamic characteristics are varied greatly. This is the prime reason of difficulty of controlling the interleaved PFC boost converter. In this paper, the robust digital controller using an A2DOF (Approximate 2-Degree-Of-Freedom) method for suppressing the variation of output voltage in dynamic load response with high power factor and low harmonic is proposed. Experimental studies using a micro-processor for controller demonstrate that this type of digital controller is effective to improve power factor and to suppress output voltage variation.

Design of a robust digital controller for a PFC boost converter

Abstract: A PFC boost converter is a non-linear system whose small perturbation model is changed at each operating point depending on a duty ratio. And when the duty ratio, a load resistance and an input voltage are changed, the small perturbation model is changed greatly. The robust controller for the PFC boost converter is needed to suppress the output voltage change at load sudden change while attaining a high power factor and a low harmonic. In this paper, the combining method and design methods of two approximate 2-degree-of-freedom (A2DOF) controllers which simplify the overall controller and attain good robustness are proposed. The proposed controller is actually implemented on a Micro-processor and is connected to the PFC boost converter. Experimental studies demonstrate that the proposed robust controller is effective to suppress the output voltage change improving the power factor and decreasing the harmonic.

Approximate 2-Degree-of-Freedom control for interleaved PFC boost converters

Abstract: Making power factor and harmonics distortion of power supply better are needed. An interleaved boost converter is used for an active PFC (Power Factor Correction) for reducing ripples. In the PFC boost converter, if a duty ratio, a load resistance and an input voltage are changed, the dynamic characteristics are varied greatly. This is a prime reason of difficulty of controlling the PFC boost converter. In this paper, a robust digital controller of the interleaved PFC boost converter using an A2DOF (Approximate 2-Degree-Of-Freedom) method for keeping up high power factor and low harmonics against any load is proposed. Experimental studies using a microcontroller for the controller demonstrate that this type of digital controller is effective to improve power factor and to suppress the output voltage variation.

Approximate 2DOF Digital Controller for Interleaved PFC Boost Converter

Abstract: In recent years, improving of power factor and reducing harmonic distortion in electrical instruments are needed. In general, a current conduction mode boost converter is used for active PFC (Power Factor Correction). In a PFC boost converter, if a duty cycle, a load resistance and an input voltage are changed, the dynamic characteristics are varied greatly. This is the prime reason of difficulty of controlling the interleaved PFC boost converter. In this paper, the robust digital controller using an A2DOF (Approximate 2-Degree-Of-Freedom) method for suppressing the variation of output voltage in dynamic load response with high power factor and low harmonic is proposed. Experimental studies using a micro-processor for controller demonstrate that this type of digital controller is effective to improve power factor and to suppress output voltage variation.

Control of an LLC Resonant Converter Using Load Feedback Linearization

Abstract: LLC resonant converter is a nonlinear system, limiting the use of typical linear control methods. This paper proposed a new nonlinear control strategy, using load feedback linearization for an LLC resonant converter. Compared with the conventional PI controllers, the proposed feedback linearized control strategy can achieve better performance with elimination of the nonlinear characteristics. The LLC resonant converter's dynamic model is built based on fundamental harmonic approximation using extended describing function. By assuming the dynamics of resonant network is much faster than the output voltage and controller, the LLC resonant converter's model is simplified from seven-order state equations to two-order ones. Then, the feedback linearized control strategy is presented. A double loop PI controller is designed to regulate the modulation voltage. The switching frequency can be calculated as a function of the load, input voltage, and modulation voltage. Finally, a 200 W laboratory prototype is built to verify the proposed control scheme. The settling time of the LLC resonant converter is reduced from 38.8 to 20.4 ms under the positive load step using the proposed controller. Experimental results prove the superiority of the proposed feedback linearized controller over the conventional PI controller.

Analysis and Modeling of LLC Resonant Converter Used in Electric Vehicle

Abstract: In this paper, analysis and modeling of an LLC resonant converter applied for an electric vehicle, are presented. The converter parameters, such as resonant tank elements, are chosen in order to improve the overall efficiency of the converter and to reduce the switching losses. Thus, to make a practical use of this topology, the small signal modeling technique based on the generalized state space averaging method is applied to the LLC converter. Finally, simulation results are presented to prove that the circuit operation is verified for these specifications: Input voltage 24V, output voltage 120V and output power 500W. Keywords: Resonant converter, switching losses, planar transformer, phase shift, average model, electric vehicle.

Digital regulation of an LLC resonant converter undergoing dynamic load transients — Model-based PIM design and simulation

Abstract: A digital pulse-frequency-modulated controller is designed by discretizing an analog integral controller for an LLC resonant DC-DC converter using the so called IA-PIM digital redesign method. It regulates the output voltage by adjusting the frequency of the input switching, which in turn changes the gain of the LLC converter. Its performances to sudden changes in the load are evaluated though extensive simulations. These results show that the digital controller can realize the performance of an analog controller at a sampling frequency that can be much lower than those currently prevail, which may be advantageous in terms of reduced computational requirements and power consumption.

The Parametric Simulation of the Interleaved Boost Converter for the Electric Transport Vehicle

Abstract: This paper deals with the analysis of four phase boost interleaved DC-DC converter with the non-coupled inductors for higher power application in Continuous Conduction Mode. The interleaved topology reduces input and output current ripple, voltage ripple and improves the efficiency of SMPS. The value of capacities and inductances affect the behavior of the converter. The investigation of these parameters is described and supported by parametric simulation in LT spice.

Rectifier Current Control for an LLC Resonant Converter Based on a Simplified Linearized Model

Abstract: In this paper, a rectifier current control for an LLC resonant converter is proposed, based on a simplified, two-order, linearized model that adds a rectifier current feedback inner loop to improve dynamic performance. Compared to the traditional large-signal model with seven resonant states, this paper utilizes a rectifier current state to represent the characteristics of the resonant states, simplifying the LLC resonant model from seven orders to two orders. Then, the rectifier current feedback inner loop is proposed to increase the control system damping, improving dynamic performance. The modeling and design methodology for the LLC resonant converter are also presented in this paper. A frequency analysis is conducted to verify the accuracy of the simplified model. Finally, a 200 W LLC resonant converter prototype is built to verify the effectiveness of the proposed control strategy. Compared to a traditional single-loop controller, the settling time and voltage droop were reduced from 10.8 ms to 8.6 ms and from 6.8 V to 4.8 V, respectively, using the proposed control strategy.