# US 10,309,840 B2 · Determining ambient temperature using transient device characteristics > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,309,840 B2 - Document ID: US10309840B2 - Status: Granted - Kind: B2 - Application number: 14/950,454 - Filed: 2015-11-24 - Published: 2016-05-26 - Granted: 2019-06-04 - Earliest claimed: 2014-11-25 - Assignees: Apple Inc. - Applicants: Apple Inc. - Inventors: Nagarajan Kalyanasundaram - Web page: https://patentgrep.com/patent/US10309840B2 ## CPC - G01K 7/22: the element being a non-linear resistance, e.g. thermistor (G01K7/26 takes precedence) - G01K 7/42: Circuits effecting compensation of thermal inertia; Circuits for predicting the stationary value of a temperature - G01K 13/00: Thermometers specially adapted for specific purposes - G01K 13/02: for measuring temperature of moving fluids or granular materials capable of flow - G01K: MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR (radiation pyrometry G01J5/00) ## Abstract Embodiments described herein are directed to determining an ambient temperature of an environment in which a device is operating. In some embodiments, the ambient temperature of the environment is determined by determining an initial temperature of the device and also determining when the temperature of the device reaches a first temperature threshold. When the temperature of the device reaches the first temperature threshold, the device is allowed to cool for a predetermined amount of time. Upon expiration of the amount of time, a change in temperature of the device over the amount of time is detected. The detected change in temperature is then used to determine an ambient temperature of the environment in which the device is operating. ## Claims ### Claim 1 A method for controlling a temperature of a device, comprising: determining an initial temperature of the device; applying a temperature stimulus to the device; determining when the temperature of the device reaches a first temperature threshold as a result of the applied temperature stimulus; causing the device to cool for a predetermined amount of time by removing the temperature stimulus; determining a change in temperature of the device upon expiration of the predetermined amount of time; determining an ambient temperature of an environment in which the device is operating based, at least in part, on the change in temperature of the device; and adjusting a maximum allowable temperature of the device based, at least in part, on the ambient temperature of the environment. ### Claim 2 (depends on 1) The method of claim 1, wherein the temperature stimulus is a charging operation. ### Claim 3 (depends on 2) The method of claim 2, wherein the charging operation is an inductive charging operation. ### Claim 4 (depends on 2) The method of claim 2, further comprising adjusting a current supplied by the charging operation based on the determined ambient temperature of the environment. ### Claim 5 (depends on 2) The method of claim 2, further comprising enabling the device to reach the adjusted maximum allowable temperature during the charging operation. ### Claim 6 (depends on 1) The method of claim 1, further comprising determining a time period to apply the temperature stimulus based, at least in part, on the determined ambient temperature of the environment. ### Claim 7 (depends on 6) The method of claim 6, wherein the determined time period to apply the temperature stimulus is based, at least in part, on a temperature curve associated with the device. ### Claim 8 A method for controlling a temperature of a device, comprising: determining an initial temperature of the device; applying a temperature stimulus to the device; determining when the temperature of the device reaches a first temperature threshold as a result of the temperature stimulus; causing the device to cool for a predetermined amount of time by removing the temperature stimulus; determining an amount of time to cool the device from the first temperature threshold to a second temperature threshold; determining an ambient temperature of an environment in which the device is operating based, at least in part, on a change in temperature of the device; and adjusting a maximum allowable temperature of the device based, at least in part, on the ambient temperature of the environment. ### Claim 9 (depends on 8) The method of claim 8, wherein the temperature stimulus is a charging operation. ### Claim 10 (depends on 9) The method of claim 9, wherein the charging operation is an inductive charging operation. ### Claim 11 (depends on 9) The method of claim 9, further comprising adjusting a current supplied by the charging operation based on the determined ambient temperature of the environment. ### Claim 12 (depends on 9) The method of claim 9, further comprising enabling the device to reach the adjusted maximum allowable temperature during the charging operation. ### Claim 13 (depends on 12) The method of claim 12, further comprising determining a time period to apply the temperature stimulus based, at least in part, on the determined ambient temperature of the environment. ### Claim 14 (depends on 12) The method of claim 12, wherein the determined time period to apply the temperature stimulus is based, at least in part, on a temperature curve associated with the device. ### Claim 15 A device, comprising: a processing unit; a thermistor; and a memory coupled to the processing unit, the memory for storing instructions which, when executed by the processing unit, performs a method for controlling a temperature of a device, the method comprising: determining, using the thermistor, an initial temperature of the device; causing, using the processing unit, a temperature stimulus to be applied to the device; determining, using the thermistor, when the temperature of the device reaches a first temperature threshold as a result of the applied temperature stimulus; causing, using the processing unit, the temperature stimulus to be removed from the device, thereby causing the device to cool for a predetermined amount of time; determining, using the thermistor, a change in temperature of the device upon expiration of the predetermined amount of time; determining, using the processing unit, an ambient temperature of an environment in which the device is operating based, at least in part, on the change in temperature of the device; and adjusting a maximum allowable temperature of the device based, at least in part, on the ambient temperature of the environment. ### Claim 16 (depends on 15) The device of claim 15, wherein the temperature stimulus is a charging operation. ### Claim 17 (depends on 15) The device of claim 15, wherein causing the temperature stimulus to be applied to the device comprises causing a wireless charging operation to initiate. ### Claim 18 (depends on 16) The device of claim 16, further comprising instructions for adjusting, using the processing unit, a current supplied by the charging operation based on the determined ambient temperature of the environment. ### Claim 19 (depends on 15) The device of claim 15, further comprising instructions for determining, using the processing unit, a time period to apply the temperature stimulus based, at least in part, on the determined ambient temperature of the environment. ### Claim 20 (depends on 19) The device of claim 19, wherein the determined time period to apply the temperature stimulus is based, at least in part, on a temperature curve associated with the device and stored in the memory. ### Claim 21 A method for determining an ambient temperature of an environment in which a device is operating, comprising: determining an initial temperature of the device; determining when a temperature of the device reaches a first temperature threshold; causing the device to cool for a predetermined amount of time; and determining a change in temperature of the device upon expiration of the predetermined amount of time, wherein the change in temperature of the device is used to determine the ambient temperature of the environment in which the device is operating. ### Claim 22 (depends on 21) The method of claim 21, further comprising charging a battery of the device upon determining the initial temperature of the device. ### Claim 23 (depends on 22) The method of claim 22, wherein causing the device to cool comprises ceasing to charge the device. ### Claim 24 (depends on 21) The method of claim 21, further comprising adjusting a maximum allowable temperature of the device based on the determined ambient temperature of the environment in which the device is operating. ### Claim 25 (depends on 24) The method of claim 24, further comprising enabling the device to reach the adjusted maximum allowable temperature during a charging operation. ### Claim 26 (depends on 25) The method of claim 25, wherein the charging operation is a wireless charging operation.