Kazuhiro Kajiwara

A new digital peak current mode DC-DC converter using FPGA delay circuit and simple A-D converter

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.

Digital peak current mode DC-DC converter for data center in HVDC system

The purpose of this paper is to present the digital peak current mode phase-shifted full-bridge zero volt switching dc-dc converter for the data center in the higher voltage direct current (HVDC) system, and show its transient response. The proposed peak current mode control circuit is composed of the RC integrator and comparator only and can detect the peak current in real time. At first, the basic operation of proposed method is confirmed by using the buck type dc-dc converter. Furthermore, the proposed method is applied to the prototype of 380V phase-shifted full-bridge zero volt switching dc-dc converter. The system has to be always stable in the transient response even if the input voltage is changed. As a result, the convergence time of output voltage is improved by about 50% compared with the conventional digital voltage mode control when the input voltage is 380V and 300V.

Digital load-dependent soft-start method of DC-DC converter for energy management system

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.

Control characteristics of novel digital peak current mode DC-DC converter

The purpose of this paper is to present a novel digital peak current mode dc-dc converter and its control characteristics. The proposed method can detect the peak current in real time. The proposed peak current detection circuit is composed of RC integrator and comparator as the A-D converter. The design of RC integrator has a large effect on regulation characteristics and the transient response of the proposed method. In this paper, the influence of circuit parameters of the RC integrator is clarified. As a result, it is confirmed that the proposed method shows a superior transient response by selecting optimal parameters. The convergence time and undershoot are suppressed by 67% and 34% compared with the conventional digital voltage mode control method, respectively.

A novel fast average current mode digital control for DC-DC converter

This paper introduces a novel fast average current mode digital control for dc-dc converter. The proposed control circuit has two features. First, the voltage controlled oscillator (VCO) is used for the switch/reactor current detection. The VCO is low price and can transform to digital value quickly without complex calculation when the current is detected. Second, the digital feedback value of output voltage can be calculated by the digital PID control with the fast P process. In the digital PID control with the fast P process, P and ID control are parallel processing and the sampling period of P control is shorter than the switching period due to shrink the delay time of output voltage calculation. In this paper, the input voltage or output current fluctuations characteristics of proposed circuit are studied. As results, the proposed method is superior transient response both of input voltage fluctuations and the output current ones in spite of small capacitance when the same coefficient of PID control is used.

A new digital average current-injected control dc-dc converter using VCO

In this paper, a new digital average current-injected control dc-dc converter using the Voltage Controlled Oscillator (VCO) and the PID control with fast P process is proposed. Features of the proposed digital control circuit are using the VCO and the PID control with fast P process. The VCO is a low price and can be fast transform when the reactor current is detected in real time. The VCO converts the analog input signal from the power circuit into the frequency-modulated (FM) pulse. The PID control with fast P process means the P and ID control are processed parallel. The sampling period of P control is shorter than the switching period. The paper studied transient response of the proposed circuit. The proposed digital control circuit shows superior transient characteristics in spite of easy circuit configuration by simulation results.

Transient response of integral gain switchover digital control dc-dc converter in discontinuous conduction mode

This paper presents the parameter design of the integral gain switchover function for the digital control dc-dc converter and its transient response in the DCM. The proposed gain switchover function utilizes the load current to determine the integral gain because the output current is detected in the dc-dc converters for the ICT system. The proposed method uses the hysteresis function around the critical current to avoid the gain oscillation. And then, the influence on the transient response by the integral gain of DCM is discussed in this paper. It is verified that the proposed method shows a superior transient response from the CCM to the DCM by switching to select the appropriate integral gain.

Integral gain changeable digital control DC-DC converter for wide input and load

The purpose of this paper is to present an integral gain changeable digital control dc-dc converter for the wide input and load regulation. The integral gain is switched by an average reactor current value, and its value is determined using the stabilization range of output voltage based on the integral control. Therefore, the proposed method can obtain good regulation characteristics in any input and load conditions. Furthermore, the proposed method shows a superior transient response compared with the conventional P-I-D control. As a result, the over shoot and the convergence time of output voltage can be improved by up to 22% and 75%.

A novel fast response current-mode DC-DC converter using ICO

In this paper, a novel digital fast response current-mode dc-dc converter using the current controlled oscillator (ICO) and the digital fast PID control is proposed. The ICO is a low price and can be transformed to digital value quickly when the reactor current is detected. The digital fast PID control means the P and ID control are processed parallel. The sampling period of P control is shorter than the switching period. The paper studied to the transient response of proposed circuit. The proposed digital control circuit shows superior transient characteristics in spite of simple circuit configuration. As results, in the proposed circuit, the conventional time of output voltage within 1% of desired voltage is shortened to 89% compared with the conventional PID control method. Furthermore, the undershoot of output voltage and the overshoot of reactor current are suppressed to 61% and 30%, respectively.

Stability analysis of digital feedback gain changeable control switching power converter

The dc power feeding system has been attracted attention in recent years. Since the load is dynamically changed in this system, the stability of dc-dc converter is important. This paper presents the stability analysis and the transient response of digital integral gain changeable control dc-dc converter using small output capacitance. The proposed method changes the integral gain with a single logarithm function according to the load current. It is verified the proposed method can obtain a good transient response with high stability even when the output capacitance is small.