Hybrid relay circuit having electromagnetic relay for switching AC power supply

Claim 2

A hybrid relay circuit for supplying current to a load with an AC power supply in accordance with an input control signal, comprising: an electromagnetic relay having a contact connected in series to said load and said AC power supply; and a driving circuit, connected to said electromagnetic relay, for driving said electromagnetic relay in accordance with said input control signal.

Claim 3

A circuit as set forth in claim 1, further comprising: a detection circuit, connected to said AC power supply, for detecting whether the potential of said AC power supply is zero; and an opening timing control circuit, linked between said detection circuit and said driving circuit, for turning ON said driving circuit after receiving said input control signal which is turned OFF, so that said contact is opened when the potential of said AC power supply becomes approximately zero.

Claim 4

A circuit as set forth in claim 2, wherein said detection circuit comprises: a rectifier bridge circuit having two pairs of diagonal terminals, one pair of said diagonal terminals being connected to the terminals of said AC power supply; a photocoupler connected to the other pair of diagonal terminals; and a differential circuit linked between said photocoupler and said hold circuit.

Claim 5

A circuit as set forth in claim 2, wherein said detection circuit comprises: a current transformer connected to said AC power supply, said current transformer having first and second windings; a current limiting resistor associated with said second winding of said current transformer, linked between the terminals of said contact; a rectifier bridge circuit having two pairs of diagonal terminals, one pair of said diagonal terminals being connected to said first winding of said current transformer; and a resistor connected to the other pair of diagonal terminals of said rectifier bridge circuit.

Claim 6

A circuit as set forth in claim 2, wherein said opening timing control circuit comprises: a hold circuit, connected to said detection circuit, for holding the output of said detection circuit after said detection circuit detects that the potential of said AC power supply is zero; and an integration circuit, linked between said hold circuit and said driving circuit, for delaying the output of said hold circuit, thereby turning OFF said driving circuit, said hold circuit being operated when said input control signal is turned OFF.

Claim 7

A circuit as set forth in claim 3, further comprising a DC buffer for receiving said input control signal and applying a DC voltage to said hold circuit and to said electromagnetic relay.

Claim 8

A circuit as set forth in claim 3, further comprising a DC power supply connected to said hold circuit and to said electromagnetic relay.

Claim 9

A circuit as set forth in claim 1, further comprising: a detection circuit, connected to said AC power supply, for detecting whether the potential of said AC power supply is zero; and a closing timing control circuit, linked between said detection circuit and said driving circuit, for turning ON said driving circuit after receiving said input control signal which is turned ON, so that said contact is closed when the potential of said AC power supply becomes approximately zero.

Claim 10

A circuit as set forth in claim 8, wherein said detection circuit comprises: a rectifier bridge circuit having two pairs of diagonal terminals, one pair of said diagonal terminals being connected to the terminals of said AC power supply; a photocoupler connected to the other pair of diagonal terminals; and a differential circuit linked between said photocoupler and said hold circuit.

Claim 11

A circuit as set forth in claim 8, wherein said detection circuit comprises: a current transformer connected to said AC power supply, said current transformer having primary. and secondary windings; a current limiting resistor associated with said secondary winding of said current transformer, linked between the terminals of said contact; a rectifier bridge circuit having two pairs of diagonal terminals, one pair of said diagonal terminals being connected to said primary winding of said current transformer; and a resistor connected to the other pair of diagonal terminals of said rectifier bridge circuit.

Claim 12

A circuit as set forth in claim, wherein said closing timing control circuit comprises: a hold circuit, connected to said detection circuit, for holding the output of said detection circuit after said detection circuit detects that the potential of said A C power supply is zero; and an integration circuit, linked between said hold circuit and said driving circuit, for delaying the output of said hold circuit, thereby turning ON said driving circuit, said holding circuit being operated when said input control signal is turned ON.

Claim 13

A circuit as set forth in claim 11, further comprising a DC buffer for receiving said input control signal and applying a DC voltage to said hold circuit, to said integration circuit, and to said electromagnetic relay.

Claim 14

A circuit as set forth in claim 11, further comprising a DC power supply connected to said hold circuit, to said integration circuit, and to said electromagnetic relay.

Claim 15

A circuit as set forth in claim 1, further comprising a closing timing control circuit, connected to said driving circuit, for turning ON said driving circuit after receiving said input control signal which is turned ON, so that said contact is closed when the potential of said AC power supply becomes approximately zero; and an opening timing control circuit, connected to said driving circuit, for turning ON said driving circuit after receiving said input control signal which is turned OFF, so that said contact is opened when the potential of AC power supply becomes approximately zero.

Claim 16

A circuit as set forth in claim 14, further comprising a common detection circuit for said closing timing control circuit and said opening timing control circuit, said common detection circuit detecting whether the potential of said AC power supply is zero.

Claim 17

A circuit as set forth in claim 15, wherein said common detection circuit comprises: a rectifier bridge circuit having two pairs of diagonal terminals, one pair of said diagonal terminals being connected to said contact; a photocoupler connected to the other pair of diagonal terminals; and a differential circuit linked between said photocoupler and said hold circuit.

Claim 18

A circuit as set forth in claim 15, wherein said common detection circuit comprises: a current transformer connected to said AC power supply, said current transformer having first and second windings; a current limiting resistor associated with said second winding of said current transformer, linked between the terminals of said contact; a rectifier bridge circuit having two pairs of diagonal terminals, one pair of said diagonal terminals being connected to said first winding of said current transformer; and a resistor connected to the other pair of diagonal terminals of said rectifier bridge circuit.

Claim 19

A circuit as set forth in claim 15, wherein each of said closing and opening timing control circuits comprises: a hold circuit, connected to said common detection circuit, for holding the output of said common detection circuit after said common detection circuit detects that the potential of said AC power supply is zero; and an integration circuit, connected to said hold circuit and said driving circuit, for delaying the output of said hold circuit; said integration circuit of said closing ,timing control circuit being operated when said input control signal is turned ON, said hold circuit of said opening timing control circuit being operated when said input control signal is turned OFF.

Claim 20

A circuit as set forth in claim 14, further comprising two separate detection circuits for said closing timing control circuit and said opening timing control circuit, each of said detection circuits detecting whether the potential of said AC power supply is zero.

Claim 21

A circuit as set forth in claim 19, wherein one of said detection circuits comprises: a rectifier bridge circuit having two pairs of diagonal terminals, one pair of said diagonal terminals being connected to said contact; a photocoupler connected to the other pair of diagonal terminals; and a differential.circuit linked between said photocoupler and said hold circuit, and wherein the other of said detection circuits comprises: a current transformer connected to said AC power supply, said current transformer having a winding; a rectifier bridge circuit having two pairs of diagonal terminals, one pair of said diagonal terminals being connected to said winding of said current transformer; and a resistor connected to the other pair of diagonal terminals of said rectifier bridge circuit.

Claim 22

A circuit as set forth in claim 14, further comprising a DC buffer for receiving said input control signal and applying a DC voltage to said closing and opening timing control circuits, and to said electromagnetic relay.

Claim 23

A circuit as set forth in claim 14, further comprising a DC power supply connected to said hold circuit, to said closing and opening timing control circuit, and to said electromagnetic relay.

Claim 24

A circuit as set forth in claim 1, wherein said contact is a make contact.

Claim 25

A circuit as set forth in claim 1, wherein said contact is a transfer contact thereby switching the connection of a plurality of loads to said AC power supply in accordance with said input control signal.