US 11,929,223 B2
Abnormality detection circuit and abnormality detection method
Toshihiko Katayama, Yamagata (JP)
Assigned to SEIKO EPSON CORPORATION, (JP)
Filed by Seiko Epson Corporation, Tokyo (JP)
Filed on Dec. 23, 2021, as Appl. No. 17/560,766.
Claims priority of application No. 2020-215218 (JP), filed on Dec. 24, 2020.
Prior Publication US 2022/0208492 A1, Jun. 30, 2022
Int. Cl. H01H 47/00 (2006.01); H01H 47/22 (2006.01)
CPC H01H 47/002 (2013.01) [H01H 47/223 (2013.01)] 3 Claims
OG exemplary drawing
 
1. An abnormality detection circuit comprising:
an AC power source coupled to a load via a first wiring line and a second wiring line;
a first relay contact disposed in a middle of the first wiring line;
a second relay contact disposed in a middle of the second wiring line;
a first comparative voltage detection circuit to which a voltage is applied from the AC power source irrespective of whether the first relay contact and the second relay contact are open or closed, both ends of the first comparative voltage detection circuit being connected to the first and second wiring lines, respectively;
a second comparative voltage detection circuit to which a voltage is applied from the AC power source irrespective of whether the first relay contact and the second relay contact are open or closed, both ends of the second comparative voltage detection circuit being connected to the first and second wiring lines, respectively;
a first voltage detection circuit to which a voltage is applied from the AC power source when the first relay contact is closed, one end of the first voltage detection circuit being connected to the AC power source via the second wiring line while passing through no other switch;
a second voltage detection circuit to which a voltage is applied from the AC power source when the second relay contact is closed, one end of the second voltage detection circuit being connected to the AC power source via the first wiring line while passing through no other switch; and
an abnormality detector that detects abnormalities of the first relay contact by comparing the voltage applied to the first comparative voltage detection circuit with the voltage applied to the first voltage detection circuit and detects abnormalities of the second relay contact by comparing the voltage applied to the second comparative voltage detection circuit with the voltage applied to the second voltage detection circuit.