Matsushita Electric Industrial Co., Ltd.

Mitsubishi Denki Kabushiki Kaisha

Masafumi Nakamura

Tatsuo Maeoka

Tosiaki Tsuruoka

Shintaro Mori

Toshiaki Tsuruoka

An AC power source apparatus to be used in an AC corona generator necessary for a de-electrification/separation process, which is one of electrographic image forming processes, or in a case where a low frequency AC power source is required, has a construction such that a high-frequency pulse, whose time ratio is modulated trapezoidally with time, is applied to switching elements connected in inverse-series across a primary winding of a transformer, an inductance element having a regenerative diode and a reset winding is inserted between an intermediate tap of the primary winding of the transformer and a DC power supply input terminal, and an LC filter is formed by stray capacitance of a secondary winding of the transformer, whereby a desired output waveform can be produced with a simple circuit construction. A trapezoidal wave used in the AC power source apparatus is generated by an amplitude-controlled trapezoidal wave generator which includes a wave-forming capacitor which is charged and discharged by two variable current sources under control of a timing circuit.

Amplitude-controlled trapezoidal wave generating circuit

Respective current supply means (I.sub.A, I.sub.B) control conducting periods of corresponding transistors (Q.sub.3, Q.sub.4), whereby conducting periods of driving transistore (Q.sub.6, Q.sub.7) are also controlled. Thus, periods in which both of the driving transistors (Q.sub.6, Q.sub.7) simultaneously enter ON states are reduced and through current (I.sub.S) flowing to the ground level GND through the driving transistors (Q.sub.6, Q.sub.7) is reduced. A pull-down transistor (Q.sub.8) controls a conducting period of the driving transistor (Q.sub.7), whereby periods in which both of the driving transistors (Q.sub.6, Q.sub.7) simultaneously enter ON states are reduced and the through current (I.sub.S) is reduced.

Switching output circuit with high speed operation and low power

An AC power source apparatus to be used in an AC corona generator necessary for a de-electrification/separation process, which is one of electrographic image forming processes, or in a case where a low frequency AC power source is required, has a construction such that a high-frequency pulse, whose time ratio is modulated trapezoidally with time, is applied to switching elements connected in inverse-series across a primary winding of a transformer, an inductance element having a regenerative diode and a reset winding is inserted between an intermediate tap of the primary winding of the transformer and a DC power supply input terminal, and an LC filter is formed by stray capacitance of a secondary winding of the transformer, whereby a desired output waveform can be produced with a simple circuit construction.

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Tsu, Japan

Masafumi Nakamura