Murata Manufacturing Co., Ltd.

Seiichi Takahashi

Koji Nishi

Yasuo Ohashi

Takayoshi Nishiyama

Yukio Sakamoto

Tadahiko Matsumoto

Jun Nagai

Hitoshi Tsuji

Eito Moromizato

Yoshihiro Matsumoto

Yoshio Arakawa

Koji Kitamura

A switching power supply circuit reduces the time from start-up driving to normal operation while a soft-start is carried out with an output voltage Vout. A soft-start capacitor is charged during the start-up time. After a soft-start voltage Vz has reached a predetermined signal-output starting voltage Vlow, soft start of the output voltage Vout is carried out by controlling the operation based on the soft-start voltage Vz. A time constant for charging the soft-start capacitor is set as a time constant that causes the charge voltage of the soft-start capacitor to sharply increase at least until the soft-start voltage Vz reaches the signal-output starting voltage Vlow after the circuit has started driving, and is switched to a time constant that causes a rising trend of the charge voltage of the soft-start capacitor to become gentle with a predetermined time-constant switching timing. The start-up time is reduced by an amount equivalent to a reduction in the delay time from the start of driving to the start of voltage output.

Switching power supply circuit with a soft-start function

In a switching power-supply unit in which a series circuit comprising a primary winding of a switching transformer and a switching device is provided across the terminals of an input power supply, a noise-eliminating bypass capacitor is connected across the ends of the series circuit. The bypass capacitor forms a short circuit path for high frequency noise having a frequency higher than the switching frequency of the switching device, thereby reducing high-frequency radiant noise.

Switching power-supply unit

When a multilayer substrate is formed by alternately laminating a plurality of substrates having coil patterns and preimpregs including an epoxy resin, and by pressing in the direction of lamination while heating, the epoxy resin is melted and may leak from between the substrates, and may form voids between the coil patterns so as to render the electrical insulation therebetween unsatisfactory. According to the present invention, a fence pattern or another structure is formed around each coil pattern, which substantially prevents leakage of the melted epoxy resin from between the substrates, and therefore, the spaces between the coil patterns remain securely filled with the epoxy resin.

Multilayer substrate

A current-mode control device for controlling an output voltage of a DC power supply including: a switching element for supplying an output voltage of the DC power supply through an on/off switching action; an output voltage detector circuit for detecting the output voltage of the DC power supply and outputting an output voltage based on the output voltage of the DC power supply; a current sense circuit for converting into a voltage a switching current flowing through the switching element during the switch-on period of the switching element to sense and output the resulting voltage; an integrating circuit for converting the switching current of the switching circuit that increases at a gradient of a straight line linear function with time during of the switch-on period of the switching element into a voltage that increases at a rate defined by a quadratic or higher-order curved line with time by integrating the switching current of the switching circuit at least once and for superimposing the resulting voltage on the output voltage of the current sense circuit; and a switching control circuit for controlling the on/off switching action of the switching element in response to the output voltage of the output voltage detector circuit and the output voltage of the current sense circuit on which the output voltage of the integrating circuit is superimposed such that the output voltage of the DC power supply is stabilized.

Current-mode control device and switching power supply employing same

According to one embodiment of a switching power supply, a superimposition circuit including a resistor is connected in parallel to the primary coil of a transformer. A superimposition current is supplied to a current sensing circuit during a switching-on period of a switching element. The current sensing circuit detects the current flowing through the primary coil during the switch-on period. According to the detected current, a switch control circuit controls switching on and off of the switching element so as to stabilize the output voltage. When the current becomes low in a case in which the circuit has a light load or receives a high input voltage, noise generally causes substantial adverse effects. However, since the detected current in the current sensing circuit is biased to become larger by superimposing the superimposition current of the superimposition circuit on the current flowing through the primary coil, the output voltage is stabilized without receiving adverse effects of noise even if the current passing through the primary coil becomes low.

Switching power supply having current and voltage superimposition

An overcurrent protection circuit provided for a switching power supply has a current detector, voltage superposition device, and circuit for reducing a driving pulse. The current detector detects a circuit current in the switching power supply and converts it to a voltage. The voltage superposition device generates a constant voltage and superposes the voltage onto the detected voltage converted by the current detector. The detected voltage onto which the constant voltage has been superposed is applied between the base and the emitter of a transistor which functions as the circuit for reducing the driving pulse. If an overcurrent flows through the switching power supply, the transistor is turned on and a current flows into the transistor. As a result, a voltage applied to a maximum-duty-cycle setting terminal of a PWM IC provided for the switching power supply and used for pulse-width-modulation control of a switch device is reduced, and the overcurrent is suppressed.

Overcurrent protection circuit

A capacitor arrangement for use in filtering high frequency noises includes a dielectric disc plate and electrodes deposited on opposite flat surfaces of the disc plate. A terminal leg extends from one electrode for the connection with ground, and two terminal legs extend from the other electrode for the connection with consecutive lead lines. The terminal legs connected with the consecutive lead lines are mounted with magnetic elements for increasing the inductance in the terminal legs.

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Sagamihara, Japan

Seiichi Takahashi