Electric-supply-switch relay-circuit

• US 5,590,013 A
• Filed: 02/22/1996
• Issued: 12/31/1996
• Est. Priority Date: 11/30/1992
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Harasawa, Shinichiro
• Primary Examiner(s): FLEMING, FRITZ M
• Application Number:
  US08/605,655
• Time in Patent Office: 313 Days
• Field of Search: 361/187, 307/130, 307/131
• US Class Current: 361/187
• CPC Class Codes: H01H 47/32 Energising current supplied by semiconductor device
• CPC Class Codes: H04B 3/44 Arrangements for feeding power to a repeater along the transmission line

Abstract

An electric-supply-switch relay-circuit includes a first switch unit for passing an input current from an electric-supply line as a relay operating current; a relay for performing switching operations in accordance with the relay operating current; and a current detect control unit for detecting the input current. When the input current is found to be equal to or larger than a predetermined value necessary for operating the relay, the current detect control unit turns on the first switch unit to thereby allow the input current to the relay.

Claims

1. An electric-supply-switch relay-circuit, comprising:

first switch means for passing an input current from an electric-supply line as a relay operating current;

a relay for performing switching operations in accordance with said relay operating current provided via said first switch means;

and current detect control means for determining that said relay operating current is present, when an input current from said electric-supply line and flowing therethrough is determined to be equal to or larger than a predetermined value necessary for operating said relay,

said current detect control means turning on said first switch means to thereby pass said relay operating current flowing therethrough before turning on said first switch means to said relay.

2. An electric-supply-switch relay-circuit as set forth in claim 1, wherein said current detect control means includes a current detect circuit for detecting a part of said input current, an amplifier for amplifying a signal detected by said current detect circuit, and a comparator for deciding whether said first switch means must be turned on by comparing a current value applied from said amplifier with a predetermined threshold value which is sufficient to supply an operating current to said relay.

3. An electric-supply-switch relay-circuit as set forth in claim 2, further including a power supply circuit for providing an operation power produced by said input current to said amplifier and said comparator.

4. An electric-supply-switch relay-circuit as set forth in claim 3, wherein said power supply circuit has a zener diode to generate a reference voltage.

5. An electric-supply-switch relay-circuit as set forth in claim 2, wherein said current detect circuit has very small resistance.

6. An electric-supply-switch relay-circuit as set forth in claim 2, wherein said comparator is a schmitt-comparator type comparator.

7. An electric-supply-switch relay-circuit as set forth in claim 1, wherein said first switch means is a semiconductor switch circuit.

8. An electric-supply-switch relay-circuit as set forth in claim 7, wherein said semiconductor switch circuit includes a transistor switch circuit.

9. An electric-supply-switch relay-circuit, comprising:

current detect means for determining that a relay operating current from an electric-supply line is present;

first switch means for passing an input current as said relay operating current provided via said current detect means;

a relay for performing switching operations in accordance with said relay operating current provided via said first switching means; and

switch control means responsive to said current detect means for turning on said first switch means, when said input current detected by said current detect means is determined to be equal to or larger than a predetermined value necessary for operating said relay,

to thereby pass said relay operating current provided via said current detect means and flowing therethrough before turning on said first switch means to said relay.

10. An electric-supply-switch relay-circuit as set forth in claim 9, wherein said current detect means for detecting an input current from a electric-supply line is a current detect resistor.

11. An electric-supply-switch relay-circuit as set forth in claim 9, wherein said first switch means is a semiconductor switch circuit.

12. An electric-supply-switch relay-circuit, comprising:

current detect means for determining that a relay operating current from an electric-supply line is present;

first switch means for passing an input current from said electric-supply line as a relay operating current;

a relay for performing switching operations in accordance with said relay operating current; and

switch control means responsive to said current detect means for turning on said first switch means, when said input current detected by said current detect means is determined to be equal to or larger than a predetermined value necessary for operating said relay, to thereby allow said relay operating current to pass via said current detect means to said relay, only when said input current is equal to or larger than said predetermined value;

wherein said switch control means includes a comparator for turning said first switching means on or off, a threshold and shunt circuit for applying a threshold value to one input terminal of said comparator and providing a shunt path for said input current, and a control circuit for applying a switch change-over signal to another input terminal of said comparator.

13. An electric-supply-switch relay-circuit as set forth in claim 12, wherein said threshold and shunt circuit includes a zener diode for making a reference voltage and bypassing a part of said input current, and divider resistors for producing said threshold value by using said reference voltage.

14. An electric-supply-switch relay-circuit as set forth in claim 12, wherein said control circuit includes a load resistor and a switching part for passing a part of said input current under control of said current detecting means, to produce the switch change-over signal by sensing a part of said input current flowing through said load resistor and said switching part.

15. An electric-supply-switch relay-circuit as set forth in claim 14, wherein said switching part is a transistor switch circuit.

20. An electric-supply-switch relay-circuit as set forth in claim 12, wherein each of said first switch means and said second switch means is a semiconductor switch circuit.

16. An electric-supply-switch relay-circuit, comprising:

current detect means for determining that an input current from an electric-supply line is present;

first switch means for passing an input current from said electric-supply line and said current detect means as a relay operating current;

a relay for performing switching operations in accordance with said relay operating current said relay being operated from the electric supply line without loading said first switch means;

second switch means for passing said relay operating current from said current detect means to an equivalent impedance element of said relay; and

switch change-over means operating in accordance with a current detect signal which is received from said current detect means, said switch change-over means turning on said first switch means and turning off said second switch means when said input current is larger than a predetermined value necessary for operating said relay, said switch change-over means turning off said first switch means and turning on said second switch means when said input current is smaller than said predetermined value.

17. An electric-supply-switch relay-circuit as set forth in claim 16, wherein said switch change-over means includes a differential amplifier for comparing a signal value applied from said current detect means with a predetermined threshold value and thereby controlling said first switch means and said second switch means in a complementary operation, a threshold circuit for generating said predetermined threshold value and providing it to one input terminal of said differential amplifier, and an adjusting circuit for adjusting the value of a signal applied by said current detect means and providing it to another input terminal of said differential amplifier.

18. An electric-supply-switch relay-circuit as set forth in claim 17, wherein said adjusting circuit is a divider resistor circuit.

19. An electric-supply-switch relay-circuit as set forth in claim 16, wherein said equivalent impedance element is a resistor which has the same resistance as the DC resistance of said relay.

21. An electric-supply-switch relay-circuit as set forth in claim 16, wherein said current detect means is a current detect resistor.