# US 8,786,314 B2 · Contactless power transfer system and control method thereof > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,786,314 B2 - Document ID: US8786314B2 - Status: Granted - Kind: B2 - Application number: 13/299,351 - Filed: 2011-11-17 - Published: 2012-05-24 - Granted: 2014-07-22 - Earliest claimed: 2010-11-18 - Assignees: Fuji Electric Co., Ltd. - Applicants: Kouji Maruyama; Akio Toba; Ayako Ichinose; Michio Tamate - Inventors: Kouji Maruyama; Akio Toba; Ayako Ichinose; Michio Tamate - Web page: https://patentgrep.com/patent/US8786314B2 ## CPC - H02J 50/12: of the resonant type - H02M 1/0085: {Partially controlled bridges} - H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY - H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P) ## Abstract A contactless power transfer system, including a coil configured to supply or receive power contactlessly via magnetic coupling, a bridge circuit having two direct current (DC) terminals and two alternating current (AC) terminals, and a smoothing capacitor connected between the DC terminals. A load is connectable to either end of the smoothing capacitor. One of the AC terminals is connected to one end of the coil via a first capacitor. The other of the AC terminals is connected to the other end of the coil. The bridge circuit includes two serially-connected circuits each having upper and lower arms, each arm having a semiconductor switch and a diode in reverse parallel connection. A second capacitor is connected in parallel to the semiconductor switch of an upper arm, or of a lower arm, or to two semiconductor switches respectively of an upper arm and of a lower arms, of the bridge circuit. ## Claims ### Claim 1 A contactless power transfer system, comprising: a coil configured to supply or receive power contactlessly via magnetic coupling; a bridge circuit having two direct current (DC) terminals and two alternating current (AC) terminals, the two AC terminals being respectively connected to two ends of the coil, the bridge circuit including two serially-connected circuits each having an upper arm and a lower arm, each of the upper and lower arms having a semiconductor switch and a diode in reverse parallel connection; a smoothing capacitor connected between the two DC terminals of the bridge circuit, a load being connectable to either end of the smoothing capacitor; a capacitor connected in parallel to the semiconductor switch of one of the upper and lower arms of the bridge circuit; and a control device configured to generate drive signals to control the semiconductor switches of the bridge circuit, based on a DC output voltage of the bridge circuit and a current flowing through the coil, wherein the drive signals include signals that put all of the semiconductor switches of the bridge circuit into an off condition during a period for which a power transfer to the coil is stopped, and that cause each of the semiconductor switches to carry out a switching action after a zero-crossing of the current of the coil is detected when power transfer to the coil is started. ### Claim 2 (depends on 1) The contactless power transfer system of claim 1, wherein the capacitor includes two capacitors respectively connected in parallel to the semiconductor switches of one of the upper arms and of one of the lower arms of the bridge circuit. ### Claim 3 (depends on 1) The contactless power transfer system of claim 1, further comprising another capacitor connecting one of the AC terminals to one of the two ends of the coil. ### Claim 4 (depends on 1) A contactless power transfer system control method for controlling switching actions of the semiconductor switches of the contactless power transfer system according to claim 1, the method comprising: putting all of the semiconductor switches of the bridge circuit into an off condition during a period for which a power transfer to the coil is stopped; and carrying out the switching action for each of the semiconductor switches of the bridge circuit after the zero-crossing of the current of the coil is detected when the power transfer to the coil is started. ### Claim 5 (depends on 1) A contactless power transfer system control method for controlling switching actions of the semiconductor switches of the contactless power transfer system according to claim 1, the method comprising: putting the semiconductor switches of the upper arms or the lower arms of the bridge circuit into an on condition during a period for which a power transfer to the coil is stopped; and carrying out the switching action for each of the semiconductor switches of the bridge circuit after the zero-crossing of the current of the coil is detected when the power transfer to the coil is started. ### Claim 6 (depends on 1) A contactless power transfer system control method for controlling switching actions of the semiconductor switches of the contactless power transfer system according to claim 1, the method comprising: maintaining a same switching condition for each of the semiconductor switches of the bridge circuit as immediately before the current of the coil becomes zero due to a stop of a power transfer to the coil, during a period for which the power transfer to the coil is stopped; and carrying out the switching action for each of the semiconductor switches of the bridge circuit after the zero-crossing of the current of the coil is detected when the power transfer to the coil is started. ### Claim 7 A contactless power transfer system, comprising: a coil configured to supply or receive power contactlessly via magnetic coupling; a bridge circuit having two direct current (DC) terminals and two alternating current (AC) terminals, the two AC terminals being respectively connected to two ends of the coil, the bridge circuit including a first circuit having two serially-connected switching arms each including a semiconductor switch and a diode in reverse parallel connection, and a second circuit having two serially-connected diodes; a smoothing capacitor connected between the two DC terminals of the bridge circuit, a load being connectable to either end of the smoothing capacitor; and a control device configured to generate drive signals to control the semiconductor switches of the bridge circuit, based on a DC output voltage of the bridge circuit and a current flowing through the coil, wherein a connection point of the two switching arms and a connection point of the two diodes form the two AC terminals of the bridge circuit, connection points of the first circuit and the second circuit form the DC terminals of the bridge circuit, and the drive signals include signals that put all of the semiconductor switches of the bridge circuit into an off condition during a period for which a power transfer to the coil is stopped, and that cause each of the semiconductor switches to carry out a switching action after a zero-crossing of the current of the coil is detected when power transfer to the coil is started. ### Claim 8 (depends on 7) The contactless power transfer system of claim 7, further comprising a capacitor connecting one of the AC terminals to one of the two ends of the coil. ### Claim 9 (depends on 7) A contactless power transfer system control method for controlling switching actions of the semiconductor switches of the contactless power transfer system according to claim 7, the method comprising: putting all of the semiconductor switches into an off condition during a period for which a power transfer to the coil is stopped; and carrying out the switching action for each of the semiconductor switches after the zero-crossing of the current of the coil is detected when the power transfer to the coil is started. ### Claim 10 (depends on 7) A contactless power transfer system control method for controlling switching actions of the semiconductor switches of the contactless power transfer system according to claim 7, the method comprising: maintaining a same switching condition for each of the semiconductor switches of the bridge circuit as immediately before the current of the coil becomes zero due to a stop of a power transfer to the coil during a period for which the power transfer to the coil is stopped; and carrying out the switching action for each of the semiconductor switches after the zero-crossing of the current of the coil is detected when the power transfer to the coil is started. ### Claim 11 (depends on 7) The contactless power transfer system according to claim 7, further comprising a capacitor connected in parallel to at least one of the semiconductor switches. ### Claim 12 (depends on 11) A contactless power transfer system control method for controlling switching actions of the semiconductor switches of the contactless power transfer system according to claim 11, the method comprising: putting all of the semiconductor switches into an off condition during a period for which a power transfer to the coil is stopped; and carrying out the switching action for each of the semiconductor switches after the zero-crossing of the current of the coil is detected when the power transfer to the coil is started. ### Claim 13 (depends on 11) A contactless power transfer system control method for controlling switching actions of the semiconductor switches of the contactless power transfer system according to claim 11, the method comprising: maintaining a same switching condition for each of the semiconductor switches of the bridge circuit as immediately before the current of the coil becomes zero due to a stop of a power transfer to the coil during a period for which the power transfer to the coil is stopped; and carrying out the switching action for each of the semiconductor switches after the zero-crossing of the current of the coil is detected when the power transfer to the coil is started. ### Claim 14 A contactless power transfer system, comprising: a coil configured to supply or receive power contactlessly via magnetic coupling; a bridge circuit having two direct current (DC) terminals and two alternating current (AC) terminals, the two AC terminals being respectively connected to two ends of the coil, the bridge circuit including a first circuit having two serially-connected switching arms each including a semiconductor switch and a diode in reverse parallel connection, and a second circuit having two serially-connected resonant capacitors; a smoothing capacitor connected between the two DC terminals of the bridge circuit, a load being connectable to either end of the smoothing capacitor; and a control device configured to generate drive signals to control the semiconductor switches of the bridge circuit, based on a DC output voltage of the bridge circuit and a current flowing through the coil, wherein a connection point of the two switching arms and a connection point of the two resonant capacitors form the two AC terminals of the bridge circuit, connection points of the first circuit and the second circuit form the DC terminals of the bridge circuit, and the drive signals include signals that put all of the semiconductor switches of the bridge circuit into an off condition during a period for which a power transfer to the coil is stopped, and that cause each of the semiconductor switches to carry out a switching action after a zero-crossing of the current of the coil is detected when power transfer to the coil is started. ### Claim 15 (depends on 14) The contactless power transfer system of claim 14, further comprising a capacitor connecting one of the AC terminals to one of the two ends of the coil. ### Claim 16 (depends on 14) The contactless power transfer system according to claim 14, further comprising a capacitor connected in parallel to at least one of the semiconductor switches. ### Claim 17 (depends on 14) A contactless power transfer system control method for controlling switching actions of the semiconductor switches of the contactless power transfer system according to claim 14, the method comprising: putting all of the semiconductor switches into an off condition during a period for which a power transfer to the coil is stopped; and carrying out the switching action of each of the semiconductor switches after the zero-crossing of the current of the coil is detected when the power transfer to the coil is started. ### Claim 18 (depends on 14) A contactless power transfer system control method for controlling switching actions of the semiconductor switches of the contactless power transfer system according to claim 14, the method comprising: maintaining a same switching condition for each of the semiconductor switches of the bridge circuit as immediately before the current of the coil becomes zero due to a stop of a power transfer to the coil during a period for which the power transfer to the coil is stopped; and carrying out the switching action for each of the semiconductor switches after the zero-crossing of the current of the coil is detected when the power transfer to the coil is started.