# US 2021/0239774 A1 · Current sensor, magnetic sensor and circuit > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0239774 A1 - Document ID: US20210239774A1 - Status: Published application - Kind: A1 - Application number: 17/155,307 - Filed: 2021-01-22 - Published: 2021-08-05 - Earliest claimed: 2020-01-31 - Assignees: TDK Corporation - Applicants: TDK Corporation - Inventors: Yuta SAITO; Yoshihiro KUDO; Daisuke MIYAUCHI; Satoshi ABE - Web page: https://patentgrep.com/patent/US20210239774A1 ## CPC - G01R 33/09: Magnetoresistive devices - G01R 1/203: {Resistors used for electric measuring, e.g. decade resistors standards, resistors for comparators, series resistors, shunts (resistors in general H01C; microwave or radiowave terminations H01P1/26; coupling devices H01R)} - G01R 15/205: {using magneto-resistance devices, e.g. field plates} - G01R 33/0017: {Means for compensating offset magnetic fields or the magnetic flux to be measured; Means for generating calibration magnetic fields} - G01R 15/207: {Constructional details independent of the type of device used} - G01R 33/093: {using multilayer structures, e.g. giant magnetoresistance sensors (thin magnetic films H01F10/00)} - G01R 33/098: {comprising tunnel junctions, e.g. tunnel magnetoresistance sensors} - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) ## Abstract The current sensor comprises: a magnetic detecting device that is arranged in the vicinity of a conductor, to which a magnetic field to be measured induced by a current flowing through the conductor is applied, and that changes an electrical resistance in response to a change in the magnetic field to be measured; two coils that generate a canceling magnetic field to cancel the magnetic field to be measured and that are arranged in the vicinity of the magnetic detecting device; a shunt resistor, that is connected in series between the two coils, for detecting a current flowing through the coils; a first differential amplifier that amplifies the output signal of the magnetic detecting device and that supplies the current to induce the canceling magnetic field to the coils; and a second differential amplifier that amplifies the voltage across the shunt resistor and that outputs a measured voltage proportional to the current flowing through the conductor. ## Claims ### Claim 1 A current sensor comprising: a magnetic detecting device that is arranged in the vicinity of a conductor, to which a magnetic field to be measured induced by a current flowing through said conductor is applied, and that changes an electrical resistance in response to a change in said magnetic field to be measured; two coils that generate a canceling magnetic field to cancel said magnetic field to be measured and that are arranged in the vicinity of said magnetic detecting device; a shunt resistor, that is connected in series between said two coils, for detecting a current flowing through said coils; a first differential amplifier that amplifies the output signal of said magnetic detecting device and that supplies the current to induce said canceling magnetic field to said coils; and a second differential amplifier that amplifies the voltage across said shunt resistor and that outputs a measured voltage proportional to the current flowing through said conductor. ### Claim 2 (depends on 1) The current sensor according to claim 1, wherein said magnetic detecting device, said two coils and said shunt resistor are formed on the same substrate. ### Claim 3 (depends on 1) The current sensor according to claim 1, wherein said two coils are respectively formed in a toroidal shape. ### Claim 4 (depends on 1) The current sensor according to claim 1, wherein said magnetic detecting device comprises a magneto-resistance effect element, and said magneto-resistance effect element is a tunnel magneto-resistance effect element. ### Claim 5 A magnetic sensor comprising: a magnetic detecting device that changes the electrical resistance in response to a change in a magnetic field to be measured; two coils that generate a canceling magnetic field to cancel said magnetic field to be measured and that are arranged in the vicinity of said magnetic detecting device; a shunt resistor, that is connected in series between said two coils, for detecting a current flowing through said coils; a first differential amplifier that amplifies the output signal of said magnetic detecting device and that supplies the current to induce said canceling magnetic field to said coils; and a second differential amplifier that amplifies the voltage across said shunt resistor and that outputs a measured voltage proportional to the current flowing through said conductor. ### Claim 6 (depends on 5) The magnetic sensor according to claim 5, wherein said magnetic detecting device, said two coils and said shunt resistor are formed on the same substrate. ### Claim 7 (depends on 5) The magnetic sensor according to claim 5, wherein said two coils are respectively formed in a toroidal shape. ### Claim 8 (depends on 5) The magnetic sensor according to claim 5, wherein said magnetic detecting device comprises a magneto-resistance effect element, and said magneto-resistance effect element is a tunnel magneto-resistance effect element. ### Claim 9 A circuit comprising: a magnetic detecting device that changes the electrical resistance in response to a change in a magnetic field to be measured; two coils that generate a canceling magnetic field to cancel said magnetic field to be measured and that are arranged in the vicinity of said magnetic detecting device; a shunt resistor, that is connected in series between said two coils, for detecting a current flowing through said coils; a first differential amplifier that amplifies the output signal of said magnetic detecting device and that supplies the current to induce said canceling magnetic field to said coils; and a second differential amplifier that amplifies the voltage across said shunt resistor and that outputs a measured voltage proportional to the current flowing through said conductor. ### Claim 10 (depends on 9) The circuit according to claim 9, wherein said magnetic detecting device, said two coils and said shunt resistor are formed on the same substrate. ### Claim 11 (depends on 9) The circuit according to claim 9, wherein said two coils are respectively formed in a toroidal shape. ### Claim 12 (depends on 9) The circuit according to claim 9, wherein said magnetic detecting device comprises a magneto-resistance effect element, and said magneto-resistance effect element is a tunnel magneto-resistance effect element.