Toru Tanaka’s research while affiliated with Japan Tobacco Inc. and other places

This paper presents a new digital load-dependent soft-start method of dc-dc converter for energy management system. The soft-start operation is used to prevent negative effects for a power supply. In the conventional soft-start operation, the dc-dc converter must start up very slowly to deal with the worst load condition. It takes long time to start up a power supply. The proposed digital control method is constructed as the digital current-mode control dc-dc converter used in the higher voltage direct current (380V HVDC) system. The speed of the soft-start operation should be set up depending to the load conditions. In the proposed digital control method, the fastest speed of the soft-start is determined using the approximated linear function of output current which is obtained from the experiment results in advance. The proposed control method has the superior soft-start characteristics of the output voltage. As a result, the convergence time of the output voltage is improved in the soft-start operation.

The purpose of this paper is to present the demonstration of digitally controlled peak current mode parallel dc-dc converter for the higher voltage direct current (HVDC) system. The peak current mode control circuit is only composed of the RC integrator and comparator. It can detect the peak current in real time. A prototype uses 800W phase-shifted full-bridge zero volt switching (ZVS) dc-dc converter. The digital control circuit is implemented by the field programmable gate array (FPGA) except the A-D conversion of output voltage. In this paper, the prototype tests the transient response by the experiment. Experimental results show that the prototype has superior transient response and it is suitable for switching power supplies for the HVDC system.

This paper presents a high speed soft-start dc-dc converter for energy management in the data center. The proposed con-trol method is constructed as the digital current-mode control dc-dc converter used in the higher voltage direct current (380V HVDC) system. In this system, power supplies are connected in parallel to obtain more high efficiency, safety and reliability in the data center. It is needed to balance between the each unit in parallel operation. In order to suppress the current imbalance between each unit, the maximum current tracking control is operated. The speed of the soft-start operation should be set up depending to the load conditions. In the proposed control method, the fastest speed of the soft-start is determined using the approximated liner function of output current which is obtained from the experiment results in advance. The proposed control method has the superior soft-start characteristics of the output voltage. As a result, the convergence time of the output voltage is improved.

The purpose of this paper is to present the prototype of digital peak-current-mode and fast feedback control dc-dc converter system with the energy management. The prototype has been developed for the higher voltage direct current (HVDC) system in the data center. The proposed digital control circuit has two features for quick responses. One is a fast P control for quick feedback calculation of output voltage. Another one is a digital peak current mode control circuit which can detect the peak current in real time unlike the conventional method. In this paper, the power efficiency and transient response of prototype has been measured in the parallel operation using up to 4 prototypes. As a result, the efficiency of prototype can keep at least 91% in more than 11% load. Furthermore, the prototype shows a superior transient response. The convergence time of output voltage can be improved by 33% compared with the conventional digital control method.

This paper describes a solution to a problem that occurs in the operation of data centers due to the disparity between the capacity of power supply equipment and the power consumption of information and communication technology (ICT) equipment. As a result of this disparity, the power supply modules and power supply units (PSUs) operate at a low load factor, which causes them to operate at low efficiency. Here we describe the operation of a supply management scheme depending on load factor for controlling the number of operating power supply modules in real time with a 380 V direct current distribution system and assess the performance of this scheme.

The purpose of this paper is to present performance characteristics of a quick response digital peak-current-mode 380V dc-dc converter for the green IT system. A proto-type is constructed as the digital control dc-dc converter used in the higher voltage direct current (HVDC) system for the green IT. The proto-type uses the digital peak-current-mode control to show a superior transient response. A dc power supply uses 380V in above HVDC system. The transient response of proto-type is indicated in this paper. As a result, the convergence time and undershoot of output voltage are suppressed to one half and one fourth, respectively.

This paper presents a fast response digitally controlled full bridge converter in parallel operation. The digital controlled circuit has some problem. One of the main problems is the delay time. The delay time includes the conversion time of A-D converter and processing time of digital controller. It exerts a bad influence on the dynamic characteristic. In the proposed method, the sample timing for P control is contrived, thus the delay time for P control is minimized. The proposed fast P control method is applied to the full bridge converters in parallel operation. It is confirmed that the proposed method has superior transient response compared to the conventional method. The proposed digitally controlled parallel full bridge converter is suitable to the power converter for automotive.

This paper presents a new digital peak current mode dc-dc converter using a FPGA delay circuit and a simple A-D converter. The peak current detection circuit is only composed of RC integrator and field programmable gate array (FPGA) delay circuit. The sampling point of detected current is changed by the feedback value of output voltage. The RC integrator is performed as the A-D converter for the current. The proposed method can detect the peak point of current in real time and shows a superior transient response. As a result, the convergence time and undershoot of output voltage are suppressed to one third and one fourth, respectively.

In recent years, 380Vdc distribution systems have been expected to be one of the energy saving solutions for telecommunication buildings and data centers. However, DC distribution systems have various problems. In this paper, We report the results of an investigation of inrush current, including current size, effects and testing methods, as one problem in the construction and operation of 380Vdc power distribution circuit.

The purpose of this paper is to present a new digital control switching power supply for the HVDC system in data center. The two stage converters are proposed to address the problem of input voltage drop. It consists of the boost converter and the phase-shifted full bridge converter. Since the first stage boost converter make the output voltage constant, good regulation characteristics against the input voltage of the server as the load and superior transient response are achieved with keeping high efficiency in this proposed converter for HVDC. A digital peak current mode control and the existing fast P control are implemented. And then the transient responses of converters in parallel operation are discussed because it is needed in the data center. The digital control method presented in this paper achieves the superior response compared with the existing digital control. It is experimentally verified with 800W prototypes that this unit has superior static and dynamic characteristics.