Akihiko Katsuki

Use of ESR for deterioration diagnosis of electrolytic capacitor

A new deterioration diagnosis method for the electrolytic capacitor is proposed for a forward-type converter and a buck-boost converter. It was observed that the ESR (equivalent series resistance) of the electrolytic capacitor increases as it deteriorates, and the knowledge that ripple varies proportionally to the ESR increase was used. With this method, the electrolytic capacitor life-cycle aging rate can be projected for the active circuit over the system life. This approach to deterioration is valid for any load condition, no matter whether the circuit has feedback control or not. >

Characteristics of transmission carrier in a new wire communication system by the use of high-ripple DC-DC converter

In the newly proposed wire communication system, converters are utilized as transmitter as well as power supply. Signal transmission is performed by the use of output voltage ripple. At transmission of a message, the ripple is intentionally increased and modulated by the signal. In this paper, the output filter capacitor of the dc-dc converter is changed according to reception or transmission. At reception, output voltage ripple is made small enough. At transmission, output voltage ripple is enlarged and used as carrier. Output voltage ripple of a buck-type dc-dc converter having small capacitance of the output capacitor becomes almost sinusoidal, when the duty ratio is 0.5. From view point of impedance matching, the output impedance is investigated. Magnitude of ripple voltage is varied by several reasons. Therefore, digital FM (Frequency Modulation), for example, FSK (Frequency-Shift Keying) can be recommended.

Analysis of high frequency gate driver using push-pull LC self-excitation oscillator

The development of techniques for integrated circuits has driven their miniaturization. The reactance components of converters can be miniaturized by using high switching frequency. Therefore the resonant converters are useful because of the low switching loss in semiconductor switches. At the resonant converters, raising or lowering of output voltage is fundamentally controlled by the switching frequency. For high frequency switching in main switch, high frequency driver is required. However, it is difficult to obtain comparators capable of high frequency operation. To overcome this, we have examined the self-excitation LC oscillation circuit for its use in the main switch drive circuit. It is important to consider the Miller effect of MOSFET about the self-excitation LC oscillation circuit analysis. In the practical circuit, variable capacitance diodes can be included in the resonant circuit. The dc voltage from outside can control the output of the converter.

Characteristics of high frequency gate driver by the use of LC self-excitation oscillator

The electronic circuits are miniaturized because the technique on integrated circuits has been developing. The reactance components of converters are miniaturized by using high switching frequency. The resonant converters are useful because of the low switching loss in semiconductor switches. At the resonant converters, raising or lowering output voltage is fundamentally controlled by the switching frequency. For high frequency switching in main switch, high frequency driver circuit is required. However, we have the difficult situation to obtain comparators capable of high frequency operation. Therefore, the self-excitation LC oscillation circuit is examined as the main switch drive circuit. The relatively large gate current must be poured or pulled at turn-on or turn-off. In this case, the capacitance at gate-source should be used as the component of resonant circuit. In the practical circuit, variable capacitance diodes can be included in the resonant circuit. The dc voltage from outside can control the output of the converter. In this paper, we researched about a self-excitation LC oscillation circuit by both the experiment and the simulation.

Signal transmission by high-ripple DC-DC converter in a new wire communication system

New wire communication system proposed by us utilizes converters as transmitter as well as power supply. Communication signal is transmitted by the carrier of output voltage ripple. At transmission of a message, the ripple is intentionally increased and modulated by the signal. The output filter capacitor of the dc-dc converter is changed according to reception or transmission. At reception, output voltage ripple is made small enough. The output voltage ripple of a forward converter having the output capacitor of small capacitance becomes almost sinusoidal under the condition of the duty ratio 0.5. Since magnitude of ripple voltage is varied by several reasons, digital FM (Frequency Modulation) is recommended. In this paper, signal transmission and reception by FSK (Frequency-Shift Keying) is investigated.

A reliable electronic choke with no need of gain adjustment for wire communication system

Metallic communication lines in wire communication systems are usually used as power lines. Ac communication signal and dc supply power are separated at input part of a powered terminal. Conventional well-known separators utilize the combination of inductors and capacitors. When the signal frequency is low, volume of these components increases. A conventional electronic choke circuit using transistors has the disadvantage of high power dissipation. Furthermore, the direction of the dc current is limited to unidirectional. Our original communication system consists of powering terminals and powered terminals. The direction of the dc current in the powering terminals is opposite to that in the powered terminals. Therefore, it is preferable to have a bidirectional electronic choke. With respect to our low-loss electronic choke with small inductors and an amplifier, wide band frequency characteristics can be obtained. In this paper, a new electronic choke with no need of gain adjustment in amplifier is proposed.

A novel two-compensation digital control DC-DC converter

The purpose of this paper is to present a digital control method which suppresses the delay-time for the switching power supplies. The operation part of power supply has two controllers as the fast PD and the conventional PID, which are processed in parallel. Therefore, the fast PD control can improve the transient response of switching pulses. Obtained simulation results show that the proposed method can improve the transient response compared with the conventional PID control method. It is confirmed that 39% and 28% improvements have been obtained for undershoot and convergence time respectively.