Coupling circuit using a photocoupler
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorsMamoru Seo, Akio Uenishi
Life of this patent
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Abstract
A solid state relay is arranged in high density to connect a first circuit comprising an outer signal source to a second circuit for driving a load by a photocoupler. A diode or a capacitor is connected in parallel to the light-receiving element of the photocoupler to maintain the voltage between the terminals of the light-receiving element to less than the reverse breakdown voltage of the light-receiving element when a surge voltage having rapid rise time is applied between the input side and the output side of the photocoupler. A transistor which causes the reverse breakdown prior to the reverse breakdown of the light-receiving element can be connected in parallel to the light-receiving element.
Claims9
A coupling circuit for connecting a first circuit and a second circuit comprising:
- a photocoupler including a light emission element whose light emission is controlled by the first circuit and a light receiving element for driving the second circuit by receiving the light from the light emission element to be turned on;
- the light emission element and the light receiving element being electrically connected through a stray capacitance arising between the first circuit and the second circuit so that a reverse breakdown of the light receiving element can be produced by a surge voltage applied through the stray capacitance to the light receiving element;
- and
- means connected in parallel to the light receiving element for blocking the reverse breakdown of the light receiving element.
Dependencies are inferred from the claim text.