Sanyo Electric Co., Ltd.

Tadao Mandai

Kenji Ikeda

Kenichi Hosaka

Provided is a switching element including: first switching element primarily used for formation of a two-way current path; a second switching element that forms, at the time when the first switching element is turned off, a current path by switching a parasitic diode from another; and a third switching element. The second and third switching elements may be of smaller chip size because they allow a current to flow through them only while the current path of the first switching element is being switched. This contributes miniaturization of the switching element as well as reduction in the ON resistance. Moreover, adoption of the switching element to a protection circuit realizes miniaturization of the protection circuit.

Switching element and protection circuit using the same

A current control circuit controls a current from a current drawing circuit to which a primary coil of a transformer is connected. A first N channel transistor has a source connected to the current drawing terminal and has a body diode that directs a current from the source to a drain. A second N channel transistor has a drain connected to the drain of the first N channel transistor and a source connected to a ground. The second N channel transistor has a body diode that directs a current from the source to the drain. The first and second N channel transistors are turned on to direct a current from the current drawing terminal to the ground via the first and second N channel transistors. The first and second N channel transistors are turned off to stop the current from the current drawing terminal. Further, the body diode of the first N channel transistor inhibits current flowing from the ground to the primary coil of the transformer.

Current control circuit

Provided is a switching element including: a first switching element primarily used for formation of a two-way current path; and a second switching element that interrupts a parasitic diode at the time when the first switching element is turned off. The second switching element may be of smaller chip size because it assists the operation of the first switching element, thereby contributing miniaturization of the switching element and reduction in an ON resistance. Furthermore, adoption of the switching element to a protection circuit realizes reduction in the size of the protection circuit.

This invention includes a square wave signal generating circuitfor generating a square wave signal whose frequency changes; a MOS transistorwhich is turned on/off on the basis of the square wave signal to supply a driving current to a vibrator; and a frequency shift detecting circuitfor detecting a frequency shift between the square wave signal from the square wave generating circuit and a resonance frequency of the vibrator. The shift in the frequency generated by the square wave generating circuit is trimmed by a signal detected by the frequency shift detecting circuit.

Vibrator controlling circuit

In order to quickly stop vibration of a vibrator of a vibrator controlling circuit, according to the present invention, an intermittent signal is generated by a spring vibration control integrated circuit, a switching element is turned on/off based on the intermittent signal from the spring vibration control integrated circuit, an intermittent electric current is supplied to a spring vibrator by switching of the switching circuit and the spring vibrator is vibrated. When vibration of the spring vibrator is stopped, a signal opposite to that when the spring vibrator is vibrated is applied from the spring vibration control integrated circuit to the switching element so as to cause the spring vibrator to generate a force to attenuate vibration and to stop the vibrator from vibrating.

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Gunma, Japan

Tadao Mandai