Terukazu Sato

Analysis and design considerations of a buck converter with a hysteretic PWM controller

This paper presents an analysis and design considerations of a buck converter with a hysteretic PWM controller consist only of a comparator with a hysteresis. The ramp voltage superimposed on the output is supplied to the comparator from a simple RC network connected in parallel to the inductor winding. The steady-state output voltage and the switching frequency are initially examined taking the propagation delay in the control circuit into account. Next, the transfer functions of the output voltage for the input voltage and the load current are analyzed. The transient response of the output voltage for the step load change is also investigated by using the state equation. Furthermore, the design of the time constant of RC networks as a key parameter is discussed.

Steady-state and dynamic analysis of a buck converter using a hysteretic PWM control

In this paper, steady state and dynamic analysis of a buck converter using a hysteretic PWM control scheme is presented. Since the proposed control scheme only uses a comparator with hysteresis and a feedback resistor, numbers of components in a control circuit are reduced. In addition, no error amplifier is used, thus the stability of the converter becomes excellent. The steady state and dynamic analysis of the proposed converter is performed and verified by experiments. We proved that the proposed control scheme has no phase lag and shows excellent transient response.

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

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

Analysis and optimum design of a buck-type DC-to-DC converter employing load current feedforward

Analytical and experimental considerations of the dynamic characteristics of a voltage controlled buck-type DC-to-DC power converter employing load current feedforward are described. The performance index, integral of the output voltage square error is introduced to evaluate the dynamic behavior of the output voltage by taking a transfer-function of a current transformer into consideration. As a result, optimum conditions of the feedforward parameters that give the excellent dynamic regulation are derived. Furthermore, the effective control region of the feedforward limited by the saturation characteristics of the PWM is discussed.

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.

A new PWM control scheme using a triangle waveform modulated by output voltage

In this paper, a new PWM control scheme using a triangle waveform modulated by output voltage is presented. Since the proposed control scheme only uses a comparator with hysteresis and a feedback resistor, numbers of components in a control circuit are reduced. In addition, because no error amplifier is used, the stability of the converter becomes excellent. The steady-state analysis of the proposed converter is performed and verified by the experiments.

The overload-protection characteristics of the current-mode DC-to-DC converter: analysis and improvement

A technique for overload protection of current-mode DC-to-DC converters is proposed in which output voltage is fed back to control the current. The method, called current limiting by voltage feedback (CLVF), solves two serious problems: inarbitrarity of drooping curve and short-circuit-current runaway. The state and dynamic characteristics of CLVF are analyzed using the state-space-averaging method. The analysis is confirmed by experiments.<<ETX>>

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.