Murata Manufacturing Co., Ltd.

Hisashi Takiguchi

Nobuaki Imamura

Tadao Nagai

Kenji Naito

Masaru Omura

Masahiko Kitamoto

Yasunobu Saida

Yasuhiko Toda

Tsuyoshi Umemoto

Haruo Takahashi

An igniter transformer includes a secondary coil and a primary coil which are closely coupled. A plurality of round single-core wires disposed substantially parallel to one another in a common plane are bonded side by side to form a flat multicore wire that is substantially rectangular in cross-section. The secondary coil includes the flat multicore wire which is edgewise wound such that the larger surfaces of the flat multicore wire face each other in the turns while standing upright. The primary coil includes a wide thin metal sheet wound substantially perpendicularly to an axis of the secondary coil.

Igniter transformer

A flyback transformer has a winding portion. The winding portion includes a low-voltage bobbin, a high-voltage bobbin, low-voltage winding, and high-voltage winding, each of which having a flattened substantially circular cross-section. The high-voltage winding is wound so as to have a film-layer winding structure. Diodes are provided such that each diode is coupled between two corresponding winding elements provided in the layers. A high-voltage capacitor and a high-voltage resistance substrate are connected to the output of the high-voltage winding. The diodes, the high-voltage capacitor, and the high-voltage resistance substrate are arranged in the longitudinal direction of the flattened substantially circular cross-section of the winding portion.

Flyback transformer

The number of layers of a secondary winding of a flyback transformer for use in a PWM controlled high-tension voltage generator is increased to six or higher. The distributed capacitance of the flyback transformer is thus decreased, the frequency of ringing is increased, and the pulse width of a flyback pulse is narrowed. The timing of the on-operation of a control FET is expedited, and the input current to the flyback transformer is lowered. A compact and power-saving flyback transformer thus results.

A high voltage generation circuit including a transformer, the transformer having a primary winding having a primary inductance; a power supply for supplying a voltage to the primary winding of the transformer; a switching element for controlling current flowing through the primary winding of the transformer from the power supply; and a resonance capacitor which resonates with the primary winding of the transformer when the switching element is off, so that a flyback pulse is generated. The circuit has a distributed inductance and a resonance capacitance. The switching element is controlled so as to be switched on nearly at the bottom of a quiescent ringing pulse which is produced by a resonance of the primary inductance of the transformer with a capacitance included in a circuit connected to the primary winding of the transformer, after the flyback pulse is generated.

High voltage circuit

A high-voltage generating circuit includes a high-voltage production circuit, a high-voltage detecting circuit, and a control circuit. The high-voltage detecting circuit has a high-voltage circuit section to which a voltage of 1 kV to several tens of kilovolts is applied and a low-voltage circuit section to which a voltage of several tens of volts is applied. In the high-voltage circuit section, a parallel circuit formed of a first voltage-dividing resistor and a part of a second voltage-dividing resistor and a speed-up capacitor, and another parallel circuit formed of the remaining part of the second voltage-dividing resistor and a third voltage-dividing resistor and another speed-up capacitor are connected in series to form a two-stage parallel circuit.

High-voltage generating circuit

A high-voltage generating circuit includes a high-voltage production circuit, a high-voltage detecting circuit and a control circuit. The high-voltage production circuit includes clamping diodes to provide a good response for stabilizing a high voltage. The control circuit applies pulse-width control to a power source voltage. The high-voltage detecting circuit has a high-voltage circuit section to which a voltage of 1 kV to several tens of kilovolts is applied and a low-voltage circuit section to which a voltage of several tens of volts is applied. The high-voltage circuit section comprises a parallel circuit including voltage-dividing resistors and a speed-up capacitor. The speed-up capacitor is set to 1000 pF or less.

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Omihachiman, Japan

Hisashi Takiguchi