# US 10,122,217 B2 · In-band signaling within wireless power transfer systems > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,122,217 B2 - Document ID: US10122217B2 - Status: Granted - Kind: B2 - Application number: 15/152,444 - Filed: 2016-05-11 - Published: 2017-03-30 - Granted: 2018-11-06 - Earliest claimed: 2015-09-28 - Assignees: Apple Inc. - Applicants: Apple Inc. - Inventors: Stephen Hrinya; Parin Patel - Web page: https://patentgrep.com/patent/US10122217B2 ## CPC - H02J 50/12: of the resonant type - H02J 7/42: with electronic devices having internal batteries, e.g. mobile phones - H02J 50/80: involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices - H04B 5/266: {One coil at each side, e.g. with primary and secondary coils} - H04B 5/79: for data transfer in combination with power transfer - H04B 5/24: Inductive coupling - H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY - H04B: TRANSMISSION ## Abstract Systems and methods for in-band communication across a wireless power interface from a load device to a source device. The load device selectively modifies the timing of switches within a voltage rectifier coupled to an output of a receive coil within the load device that receives power from a transmit coil within the source device. The source device detects changes in the power transfer (or in the relative timing of a voltage or a current) as digital information received from the load device. ## Claims ### Claim 1 A method of operating a wireless power transfer system comprising a source device and a load device, the method comprising: transferring power from the source device to the load device; and during power transfer from the source device to the load device: determining, by the load device, a data signal comprising a series of digital bits to be communicated to the source device; and modifying a timing, by the load device, of a switch of a synchronous rectifier within the load device to desynchronize the synchronous rectifier in a pattern corresponding to the series of digital bits. ### Claim 2 (depends on 1) The method of claim 1, wherein the modification of the timing of the switch of the synchronous rectifier is a timing adjustment and comprises delaying a turn-off of the switch until after a zero-crossing of an induced current. ### Claim 3 (depends on 2) The method of claim 2, wherein the timing adjustment comprises delaying a turn-off time of the switch so that current through the switch reverses. ### Claim 4 (depends on 2) The method of claim 2, wherein the timing adjustment is configured to suppress a voltage spike associated with current conduction through a diode within the load device. ### Claim 5 (depends on 4) The method of claim 4, wherein the diode is coupled in parallel with the switch. ### Claim 6 (depends on 4) The method of claim 4, wherein: the switch is a transistor; and the diode is a body diode incorporated within the transistor. ### Claim 7 (depends on 4) The method of claim 4, wherein: the switch is a transistor; and the diode is a Schottky diode coupled across a source and a drain of the transistor. ### Claim 8 (depends on 2) The method of claim 2, wherein the timing adjustment is performed by a timing adjuster. ### Claim 9 A method for operating a wireless power transfer system that includes a source device and a load device, the method comprising: transferring power from the source device to the load device; and during power transfer from the source device to the load device: determining, by the source device, whether a current threshold crossing has occurred or has not occurred within an electronic element of the source device at a time corresponding to an edge of one half-cycle of an inverter of the source device; and buffering, by the source device, a series of digital bits corresponding to a data signal sent from the load device to the source device, each digital bit of the series of digital bits corresponding to a respective determined occurrence or a respective determined absence of occurrence of a respective current threshold crossing. ### Claim 10 (depends on 9) The method of claim 9, wherein the source device comprises a bridge inverter; and the operation of determining, by the source device, whether the current threshold crossing has occurred within the electronic element of the source device comprises monitoring a switch of the bridge inverter for a drop in current. ### Claim 11 (depends on 10) The method of claim 10, wherein the operation of monitoring the switch of the bridge inverter for the drop in current comprises: measuring a current through the switch; and comparing the current to a threshold value. ### Claim 12 A method for operating a wireless power transfer system that includes a source device and a load device, the method comprising: transferring power from the source device to the load device; and during power transfer from the source device to the load device: determining, by the source device, whether a phase shift has occurred in an alternating current passing through an electronic element of the source device; and buffering, by the source device, a digital bit for each determined phase shift and a complimentary digital bit for each determined absence of phase shift. ### Claim 13 (depends on 12) The method of claim 12, wherein the source device comprises a bridge inverter; and the operation of determining, by the source device, that the phase shift has occurred in the alternating current passing through the electronic element of the source device comprises: monitoring a phase of current passing through the bridge inverter for a change. ### Claim 14 (depends on 13) The method of claim 13, wherein the operation of monitoring a phase of current passing through the bridge inverter for the change comprises: measuring a phase of alternating current passing through the bridge inverter; and comparing the phase to a threshold value. ### Claim 15 A wireless power transfer system, comprising: a source device comprising: a bridge inverter comprising a first set of switches; a transmit coil coupled to an output of the bridge inverter; and a first processor configured to monitor a first electrical characteristic of the bridge inverter during operation of the bridge inverter; and a load device aligned with the source device, the load device comprising: a receive coil; a bridge rectifier coupled to an output of the receive coil, the bridge rectifier comprising a second set of switches; and a second processor coupled to the bridge rectifier; wherein the second processor is configured to perform a sequence of timing modifications, each timing modification comprising a delay of a turn-off of at least one switch of the second set of switches and based, at least in part, on a digital bit of a data signal to be communicated to the source device. ### Claim 16 (depends on 15) The wireless power transfer system of claim 15, wherein the first electrical characteristic comprises a voltage spike across at least one switch of the first set of switches. ### Claim 17 (depends on 15) The wireless power transfer system of claim 15, wherein the first electrical characteristic comprises a phase shift in at least one of a voltage or a current across at least one of the switches of the first set of switches. ### Claim 18 (depends on 15) The wireless power transfer system of claim 15, wherein the first processor is configured to obtain the data signal by monitoring the first electrical characteristic. ### Claim 19 (depends on 15) The wireless power transfer system of claim 15, wherein at least one switch of the first set of switches is a transistor that incorporates a body diode. ### Claim 20 (depends on 15) The wireless power transfer system of claim 15, wherein the load device is a wearable electronic device.