# US 10,771,021 B2 · Thermal protection of an amplifier driving a capacitive load > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,771,021 B2 - Document ID: US10771021B2 - Status: Granted - Kind: B2 - Application number: 16/269,063 - Filed: 2019-02-06 - Published: 2019-08-22 - Granted: 2020-09-08 - Earliest claimed: 2018-02-20 - Assignees: Cirrus Logic, Inc. - Applicants: Cirrus Logic International Semiconductor Ltd. - Inventors: Eric Lindemann - Web page: https://patentgrep.com/patent/US10771021B2 ## CPC - H03F 1/52: Circuit arrangements for protecting such amplifiers {(monitoring arrangements G01R31/28; increasing reliability in communication systems, e.g. using redundancy H04B1/74)} - H03F 1/30: Modifications of amplifiers to reduce influence of variations of temperature or supply voltage {or other physical parameters (in differential amplifiers H03F3/45479)} - H03F 3/187: in integrated circuits - H03F 3/21: with semiconductor devices only {(H03F3/245 takes precedence)} - H03F 3/213: in integrated circuits - H03H 7/0153: {Electrical filters; Controlling thereof} - H03H 7/54: Modifications of networks to reduce influence of variations of temperature - H03H 11/04: Frequency selective two-port networks - H03H 11/54: Modifications of networks to reduce influence of variations of temperature - H04R 3/06: of electrostatic transducers - H04R 19/04: Microphones (H04R19/01 takes precedence) - H03F 2200/297: the loading circuit of an amplifying stage comprising a capacitor - H03H 2210/012: Centre frequency; Cut-off frequency - H03F: AMPLIFIERS - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) - H04R: LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS (producing sounds with frequency not determined by supply frequency G10K) ## Abstract A system for thermally protecting an amplifier driving a capacitive load may include a low-pass filter configured to filter, with a variable cutoff frequency, an input signal to generate a filtered input signal, wherein the amplifier is configured to receive the filtered input signal and amplify the filtered input signal to generate a driving signal to the capacitive load and a controller configured to receive a real-time estimate of a temperature associated with the amplifier and vary the variable cutoff frequency as a function of the temperature. ## Claims ### Claim 1 A device, comprising: a capacitive load; a low-pass filter configured to low-pass filter, with a variable cutoff frequency, an input signal to generate a filtered input signal; an amplifier configured to receive the filtered input signal and amplify the filtered input signal to generate a driving signal to the capacitive load; and a controller configured to: receive a real-time estimate of a temperature associated with the amplifier; and vary the variable cutoff frequency as a function of the temperature. ### Claim 2 (depends on 1) The device of claim 1, wherein varying the variable cutoff frequency comprises varying the cutoff frequency inversely to the temperature. ### Claim 3 (depends on 1) The device of claim 1, wherein the capacitive load comprises a mechanical transducer. ### Claim 4 (depends on 3) The device of claim 3, wherein the mechanical transducer comprises a piezoelectric transducer. ### Claim 5 (depends on 4) The device of claim 4, further comprising a device housing comprising a surface, wherein the mechanical transducer is mechanically coupled to the surface and configured to cause vibration of the surface to generate playback of audio content in accordance with the driving signal to the mechanical transducer. ### Claim 6 (depends on 5) The device of claim 5, wherein the surface comprises a display screen of the device. ### Claim 7 A method for thermally protecting an amplifier driving a capacitive load, comprising: low-pass filtering, with a variable cutoff frequency, an input signal to generate a filtered input signal, wherein the amplifier is configured to receive the filtered input signal and amplify the filtered input signal to generate a driving signal to the capacitive load; receiving a real-time estimate of a temperature associated with the amplifier; and varying the variable cutoff frequency as a function of the temperature. ### Claim 8 (depends on 7) The method of claim 7, wherein varying the variable cutoff frequency comprises varying the cutoff frequency inversely to the temperature. ### Claim 9 (depends on 7) The method of claim 7, wherein the capacitive load comprises a mechanical transducer. ### Claim 10 (depends on 9) The method of claim 9, wherein the mechanical transducer comprises a piezoelectric transducer. ### Claim 11 (depends on 9) The method of claim 9, wherein the mechanical transducer is mechanically coupled to a surface and configured to cause vibration of the surface to generate playback of audio content in accordance with the driving signal to the mechanical transducer. ### Claim 12 (depends on 11) The method of claim 11, wherein the surface comprises a display screen of a device. ### Claim 13 A system for thermally protecting an amplifier driving a capacitive load, comprising: a low-pass filter configured to filter, with a variable cutoff frequency, an input signal to generate a filtered input signal, wherein the amplifier is configured to receive the filtered input signal and amplify the filtered input signal to generate a driving signal to the capacitive load; and a controller configured to: receive a real-time estimate of a temperature associated with the amplifier; and vary the variable cutoff frequency as a function of the temperature. ### Claim 14 (depends on 13) The system of claim 13, wherein varying the variable cutoff frequency comprises varying the cutoff frequency inversely to the temperature. ### Claim 15 (depends on 13) The system of claim 13, wherein the capacitive load comprises a mechanical transducer. ### Claim 16 (depends on 15) The system of claim 15, wherein the mechanical transducer comprises a piezoelectric transducer. ### Claim 17 (depends on 15) The system of claim 15, wherein the mechanical transducer is mechanically coupled to a surface and configured to cause vibration of the surface to generate playback of audio content in accordance with the driving signal to the mechanical transducer. ### Claim 18 (depends on 17) The system of claim 17, wherein the surface comprises a display screen of a device.