# US 12,224,598 B2 · Wireless power transmission system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,224,598 B2 - Document ID: US12224598B2 - Status: Granted - Kind: B2 - Application number: 18/232,690 - Filed: 2023-08-10 - Published: 2023-11-30 - Granted: 2025-02-11 - Earliest claimed: 2021-02-25 - Assignees: Denso Corporation - Applicants: Denso Corporation - Inventors: Masaya Takahashi; Mitsuru Shibanuma; Kazuyuki Kato; Yusei Nakayashiki; Eisuke Takahashi; Nobuhisa Yamaguchi - Web page: https://patentgrep.com/patent/US12224598B2 ## CPC - H02J 50/12: of the resonant type - B60L 53/12: Inductive energy transfer - B60L 53/122: Circuits or methods for driving the primary coil, e.g. supplying electric power to the coil - B60L 53/39: with position-responsive activation of primary coils - B60M 7/00: Power lines or rails specially adapted for electrically-propelled vehicles of special types, e.g. suspension tramway, ropeway, underground railway - H01F 38/14: Inductive couplings - H02J 7/00: Circuit arrangements for charging or discharging batteries or for supplying loads from batteries - H02J 50/40: using two or more transmitting or receiving devices (H02J50/50 takes precedence) - H02J 50/90: involving detection or optimisation of position, e.g. alignment - H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY - B60L: PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES (arrangements or mounting of electrical propulsion units or of plural diverse prime-movers for mutual or common propulsion in vehicles B60K1/00, B60K6/20; arrangements or mounting of electrical gearing in vehicles B60K17/12, B60K17/14; preventing wheel slip by reducing power in rail vehicles B61C15/08; dynamo-electric machines H02K; control or regulation of electric motors H02P); SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES (electric coupling devices combined with mechanical couplings of vehicles B60D1/64; electric heating for vehicles B60H1/00); ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL (control or regulation of electric motors H02P); MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES - B60M: POWER SUPPLY LINES, AND DEVICES ALONG RAILS, FOR ELECTRICALLY- PROPELLED VEHICLES (control of points and safety arrangements along railway lines B61L; construction of rails and points in general E01B) - H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES ## Abstract A wireless power transmission system is provided which wirelessly transfer electric power from a power transmitter to a power receiver. The wireless power transmission system works to set a capacitance of a primary capacitor of a primary resonant circuit to undergo resonance with a self-inductance of a primary coil at an angular frequency that is an operating frequency. A tertiary capacitor of a tertiary resonant circuit has a capacitance set to undergo resonance with a self-inductance of a tertiary coil. A secondary capacitor of a secondary resonant circuit has a capacitance set to reduce a reactive component of ac power arising from self-inductances and mutual inductances of the primary coil, the secondary coil, and the tertiary coil. ## Claims ### Claim 1 A wireless power transmission system which works to supply electric power wirelessly from a power transmitter to a power receiver, comprising: a power transmitter which includes a primary resonant circuit and an alternating-current source, the primary resonant circuit including a primary coil and a primary capacitor for use in power transmission, the alternating-current source working to apply ac power at a given operating frequency to the primary resonant circuit; a power receiver which includes a secondary resonant circuit, the secondary resonant circuit including a secondary coil and a secondary capacitor for use in a power reception, the secondary coil being to be magnetically coupled with the primary coil; and a tertiary resonant circuit which includes a tertiary coil and a tertiary capacitor, the tertiary coil being arranged to achieve magnetic coupling with the primary coil and the secondary coil, the tertiary capacitor constituting a short-circuit resonant circuit along with the tertiary coil, the primary coil has a self-inductance L1, a capacitance of the primary capacitor is set to a capacitance C1, as given by Eq. (1) below, to cause resonance in the primary capacitor and the primary coil at an angular frequency ω0 that is the operating frequency, C ⁢ 1 = 1 ω ⁢ o 2 · L ⁢ 1 ( 1 ) the tertiary coil has a self-inductance L3, a capacitance of the tertiary capacitor is set to a capacitance C3, as given by Eq. (2) below, to cause resonance in the tertiary capacitor and the tertiary coil at the operating frequency, C ⁢ 3 = 1 ω ⁢ o 2 · L ⁢ 3 ( 2 ) a capacitance of the secondary capacitor is determined to decrease a reactive component of the ac power which arises from the self-inductances and mutual inductances of the primary coil, the secondary coil, and the tertiary coil. ### Claim 2 (depends on 1) The wireless power transmission system as set forth in claim 1, wherein the capacitance of the secondary capacitor is set to a value greater than a capacitance C2r given by Eq. (3) below expressed by the self-inductance L2 of the secondary coil and the angular frequency ω0, C ⁢ 2 ⁢ r = 1 ω ⁢ 0 2 · L ⁢ 2 . ( 3 ) ### Claim 3 (depends on 2) The wireless power transmission system as set forth in claim 2, wherein the capacitance of the secondary capacitor is set to a capacitance C2 given by Eq. (4) below expressed by a self-inductance L2 of the secondary coil, a mutual inductance M12 of the primary coil and the secondary coil, a mutual inductance M13 of the primary coil and the tertiary coil, a mutual inductance M32 of the tertiary coil and the secondary coil, and the angular frequency ω0, C ⁢ 2 = 1 ω ⁢ 0 2 [ L ⁢ 2 - 2 · M ⁢ 12 · M ⁢ 32 M ⁢ 13 ] . ( 4 ) ### Claim 4 (depends on 2) The wireless power transmission system as set forth in claim 2, wherein the capacitance of the secondary capacitor is set in a range of a value of the capacitance C2 and the value of the capacitance C2+25%, the value of the capacitance C2 being given by Eq. (4) below expressed by a self-inductance L2 of the secondary coil, a mutual inductance M12 of the primary coil and the secondary coil, a mutual inductance M13 of the primary coil and the tertiary coil, a mutual inductance M32 of the tertiary coil and the secondary coil, and the angular frequency ω0, C ⁢ 2 = 1 ω ⁢ 0 2 [ L ⁢ 2 - 2 · M ⁢ 12 · M ⁢ 32 M ⁢ 13 ] . ( 4 ) ### Claim 5 (depends on 2) The wireless power transmission system as set forth in claim 2, wherein the tertiary coil connects in series with the primary coil, the tertiary capacitor connects in parallel to the tertiary coil, the capacitance of the secondary capacitor is set to a capacitance C2 given by Eq. (5) below expressed by a self-inductance L2 of the secondary coil, a self-inductance L3 of the tertiary coil, a mutual inductance M12 of the primary coil and the secondary coil, a mutual inductance M13 of the primary coil and the tertiary coil, a mutual inductance M32 of the tertiary coil and the secondary coil, and the angular frequency ω0, C ⁢ 2 = 1 ω ⁢ 0 2 [ L ⁢ 2 - 2 · M ⁢ 12 · M ⁢ 32 L ⁢ 3 + M ⁢ 13 - M ⁢ 32 2 · L ⁢ 3 ( L ⁢ 3 + M ⁢ 13 ) 2 ] . ( 5 ) ### Claim 6 (depends on 2) The wireless power transmission system as set forth in claim 2, wherein the tertiary coil connects in series with the primary coil, the tertiary capacitor connects in parallel to the tertiary coil, the capacitance of the secondary capacitor is set in a range of a value of the capacitance C2 and the value of the capacitance C2+25%, the value of the capacitance C2 being given by Eq. (5) below expressed by a self-inductance L2 of the secondary coil, a self-inductance L3 of the tertiary coil, a mutual inductance M12 of the primary coil and the secondary coil, a mutual inductance M13 of the primary coil and the tertiary coil, a mutual inductance M32 of the tertiary coil and the secondary coil, and the angular frequency ω0, C ⁢ 2 = 1 ω ⁢ 0 2 [ L ⁢ 2 - 2 · M ⁢ 12 · M ⁢ 32 L ⁢ 3 + M ⁢ 13 - M ⁢ 32 2 · L ⁢ 3 ( L ⁢ 3 + M ⁢ 13 ) 2 ] . ( 5 ) ### Claim 7 (depends on 1) The wireless power transmission system as set forth in claim 1, wherein the tertiary coil is arranged in a constant state of coupling with the primary coil. ### Claim 8 (depends on 7) The wireless power transmission system as set forth in claim 7, wherein the primary coil and the tertiary coil are formed integrally in a form of a printed circuit board, and the secondary capacitor and the tertiary capacitor are mounted on the printed circuit board. ### Claim 9 (depends on 7) The wireless power transmission system as set forth in claim 7, wherein the primary capacitor is made of a variable capacitor whose capacitance is variable, and further comprising a capacitance controller which works to measure a coil current flowing through the primary coil and changes the capacitance of the primary capacitor as a function of a value of the coil current, the capacitance controller working to set the capacitance of the primary capacitor to a value lower than the value of the capacitance C1 given by Eq. (1) above when the value of the coil current decreases. ### Claim 10 (depends on 9) The wireless power transmission system as set forth in claim 9, wherein the tertiary capacitor is made of a variable capacitor whose capacitance is variable, and the capacitance controller works to decrease a capacitance of the tertiary capacitor to a value lower than the capacitance C3 given by Eq. (2) above. ### Claim 11 (depends on 10) The wireless power transmission system as set forth in claim 10, wherein the capacitance controller decreases the capacitance of the primary capacitor and then decreases the capacitance of the tertiary capacitor. ### Claim 12 (depends on 7) The wireless power transmission system as set forth in claim 7, wherein the secondary coil moves closer to or away from the primary coil, and the capacitance of the secondary capacitor is determined based on a state of coupling between the primary coil and the secondary coil, a state of coupling between the primary coil and the tertiary coil, and a state of coupling between the tertiary coil and the secondary coil in a condition where a center of the secondary coil lies in one of regions between a first coil end of the primary coil and a position which is one-half of an interval between the center of the primary coil and the first coil end away from the first coil end and between a second coil end of the primary coil and a position which is one-half of the interval away from the second coil end in a direction in which the secondary coil moves closer to or away from the primary coil. ### Claim 13 (depends on 7) The wireless power transmission system as set forth in claim 7, wherein the secondary coil moves closer to or away from the primary coil, and the capacitance of the secondary capacitor is determined based on a state of coupling between the primary coil and the secondary coil, a state of coupling between the primary coil and the tertiary coil, and a state of coupling between the tertiary coil and the secondary coil in a condition where a center of the secondary coil lies in one of regions between a center of the primary coil and a position which is one-half of an interval between the center of the primary coil and the first coil end away from the center of the primary coil and between the center of the primary coil and a position which is one-half of the interval away from the center of the primary coil in a direction in which the secondary coil moves closer to or away from the primary coil.