Kimihiro Nishijima

A novel control method of boost and buck-boost converters with a hysteretic PWM controller

A new control method for boost and buck-boost converters employing a hysteretic PWM controller is presented. The triangular voltage obtained from a simple RC network connected to an auxiliary winding of the inductor is superimposed to the output voltage and fed to a hysteretic comparator as a feedback signal. The presented control method provides no steady-state error voltage on the output and excellent dynamic performances for the variations of the input voltage and the load current

A Novel Tapped-Inductor Buck Converter for Divided Power Distribution System

A novel tapped-inductor converter which has similar characteristics to a typical buck converter is proposed. A high step-down conversion ratio is achieved, and the magnetic core size of the tapped-inductor is minimized. The high side switch is easily driven by a usual driver IC without a pulse transformer. The over voltage load protection is inherently realized without any additional components. Furthermore a divided power distribution system with the proposed tapped-inductor converter is discussed for supplying the power to the digital applications.

Analysis of Double Step-Down Two-Phase Buck Converter for VRM

A novel two-phase buck converter suitable to apply the power supplies for MPU is proposed. Compared to conventional two-phase buck converter, the proposed converter essentially has double step-down ratio as Eo/Ei = D/2 and high efficiency is realized by reducing the switching loss of the switching elements. In addition the current ripple of the output smoothing capacitor is improved to the same value as that of conventional four-phase buck converter. Moreover the current unbalance between two inductors in each phase is removed automatically without any current sensing means. The above fine characteristics are simply achieved an additional capacitor

A Novel Three-Phase Buck Converter with Bootstrap Driver Circuit

Analysis and design consideration of the novel three phase converter with new bootstrap driver circuit for the mobile micro processor in the laptop PC are presented. The voltage conversion ratio of the proposed converter is one third of the duty cycle. The voltage across the switches during switching operation is one-third of the input source voltage. The current ripple of the output smoothing capacitor is the same as that of conventional five-phase buck converter. The current balance of the respective phases is automatically achieved without any current sensing means. The above fine characteristics are simply achieved with two additional capacitors.

A two-phase high step down coupled-inductor converter for next generation low voltage CPU

In this paper, a novel two-phase high step down coupled-inductor converter for next generation low voltage CPU is proposed. This converter has a very high step down characteristic as Vo/Vi = D/4. The switching loss and noise of all switching elements are sufficiently reduced because the drain-source voltages at switching periods are reduced to a quarter of the input source voltage. Low withstand voltage MOSFETs with low on resistance and low Qg(total gate charge) characteristics are possible to use for the all switching elements because the maximum voltage stresses of the main switches and the synchronous rectifier switches are reduced to a half and a quarter of the input source voltage respectively. Further, the branch currents flowed through the paralleled converters are automatically and mostly balanced without the current detection and balance control. The above fine characteristics are simply achieved with three additional capacitors.

High efficiency operation for H-Bridge DC-DC converter

This paper presents two methods of switching operation for higher conversion efficiency and seamless control for wide range of the input voltage in a H-Bridge DC-DC Converter. This converter consists of buck and boost blocks and a feedforward control from the input voltage is employed for the boost block to realize seamless transition between step down and step up operation mode. From the view point of the conduction loss and the switching loss, two methods of the desirable duty ratio of the boost section and different switching frequencies are examined. As a result, higher efficiency was obtained by minimizing the duty ratio of the boost block for wide range of the input voltage and by decreasing the switching frequency of the buck block without increasing output ripple voltage.

Hysteretic PWM control method for all types of DC-to-DC converters

A new control method of a hysteretic PWM controller for all types of DC-to-DC converters are proposed. The triangular voltage obtained from a simple RC network connected between hysteretic comparator output and converter output is superimposed to the output voltage and fed to the hysteretic comparator as a feedback signal. Since the hysteretic PWM controller essentially has derivative characteristics and has no error amplifier, the presented method provides no steady-state error voltage on the output and excellent dynamic performances for the load current transient by choosing proper values of time constants in the RC network. Performances of the proposed controller are experimentally verified for the buck, buck-boost and boost converters.

Multi-Phase Converter Controlled by Hysteretic PWM Method

A multi-phase dc-to-dc converter controlled by hysteretic PWM method is presented in this paper. An and-gated logic circuit is employed for the synchronization and its operating principle is described. A 5 V to 1.5 V prototype buck converter of two-phase is implemented for a POL power supply. From the experiments, it is confirmed that the proposed method can be well synchronized, and an excellent dynamic performance is archived for the large load current transients. In addition, improved power efficiency and a good current sharing characteristic is derived.

DC-DC Converters with a Novel Hysteretic PWM Controller

DC-DC converters with a novel hysteretic PWM controller are presented. A novel feedback network is proposed which behaves as a PID controller. Fast transient response and no steady state error of the output voltage are achieved. Steady state and dynamic analysis are performed and confirmed by experimental results for a 5 V to 1.5 V prototype buck converter. As a result, no steady state error on the output voltage and excellent dynamic performances are derived for the large load current transients. The proposed controller is applicable not only to the buck converter but also to any other types of converters

Constant frequency hysteretic PWM controlled buck converter

This paper presents a constant frequency hysteretic PWM controlled buck converter. In order to have good transient responses for input voltage and load current changes, a new PWM control method with inherent derivative characteristics is proposed. The proposed PWM controller consists of a comparator, a simple RC network and operational amplifier, and it can be synchronized with an external clock signal. Since the converter operates at a constant frequency, it is easy not only to design an output filter but also to apply to multi-phase converters. The theoretical and experimental verification of the proposed method are presented and excellent steady state, dynamic performances, and transient characteristics are realized.