# US 10,483,924 B2 · Systems and methods for predictive switching in audio amplifiers > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,483,924 B2 - Document ID: US10483924B2 - Status: Granted - Kind: B2 - Application number: 15/925,469 - Filed: 2018-03-19 - Published: 2018-07-19 - Granted: 2019-11-19 - Earliest claimed: 2016-04-22 - Assignees: Cirrus Logic, Inc. - Applicants: Cirrus Logic International Semiconductor Ltd. - Inventors: Tejasvi Das; John L. Melanson; Eric J. King - Web page: https://patentgrep.com/patent/US10483924B2 ## CPC - H03F 3/183: with semiconductor devices only - H02M 3/07: using capacitors charged and discharged alternately by semiconductor devices with control electrode {, e.g. charge pumps} - H03F 1/0227: {using supply converters} - H03F 1/025: {by using a signal derived from the input signal} - H03F 3/187: in integrated circuits - H03F 3/21: with semiconductor devices only {(H03F3/245 takes precedence)} - H03F 3/213: in integrated circuits - H03F 2200/03: the amplifier being designed for audio applications - H03F 2200/511: Many discrete supply voltages or currents or voltage levels can be chosen by a control signal in an IC-block amplifier circuit - H03F: AMPLIFIERS - 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 An audio amplifier circuit for providing an output signal to an audio transducer may include a power amplifier and a control circuit. The power amplifier may include an audio input for receiving an audio input signal, an audio output for generating the output signal based on the audio input signal, and a power supply input for receiving a power supply voltage, wherein the power supply voltage is variable among at least a first supply voltage and a second supply voltage greater than the first supply voltage and wherein the power supply voltage is generated by a configurable charge pump power supply. The control circuit may be configured to predict, based on one or more characteristics of a signal indicative of the output signal, an occurrence of a condition for changing the power supply voltage, and responsive to predicting the occurrence of the condition, change, at an approximate zero crossing of the signal indicative of the output signal, the power supply voltage. ## Claims ### Claim 1 An audio amplifier circuit for providing an output signal to an audio transducer, the audio amplifier circuit comprising: a power amplifier having an audio input for receiving an audio input signal, an audio output for providing the output signal, and a power supply input for receiving a power supply voltage, wherein the power amplifier generates the output signal based on the audio input signal, wherein the power supply voltage is variable among at least a first supply voltage and a second supply voltage greater than the first supply voltage, and wherein the power supply voltage is generated by a configurable charge pump power supply; and a control circuit configured to: predict, based on one or more characteristics of a signal indicative of the output signal, an occurrence of a condition for changing the power supply voltage; and responsive to predicting the occurrence of the condition, change, at an approximate zero crossing of the signal indicative of the output signal, the power supply voltage. ### Claim 2 (depends on 1) The audio amplifier circuit of claim 1, wherein: the condition for changing the power supply voltage comprises the magnitude of the signal indicative of the output signal crossing a predetermined threshold magnitude; and wherein the signal indicative of the output signal is an electrical parameter associated with the charge pump power supply. ### Claim 3 (depends on 2) The audio amplifier circuit of claim 2, wherein the electrical parameter comprises one of: a voltage of a voltage source supplying power to the charge pump power supply, a current delivered by the voltage source, a fly capacitor voltage associated with a fly capacitor coupled to the charge pump power supply, a fly capacitor voltage associated with a fly capacitor coupled to the charge pump power supply, and a current associated with a switch of the charge pump power supply. ### Claim 4 (depends on 2) The audio amplifier circuit of claim 2, wherein the control circuit is configured to predict the condition of the signal indicative of the output signal crossing the predetermined threshold magnitude responsive to the magnitude of the signal indicative of the output signal decreasing below a second predetermined threshold magnitude greater than the predetermined threshold magnitude. ### Claim 5 (depends on 2) The audio amplifier circuit of claim 2, wherein the control circuit is configured to predict the condition of the signal indicative of the output signal crossing the predetermined threshold magnitude by: tracking signal peaks of the signal indicative of the output signal; extrapolating from the signal peaks a future value of the magnitude of the signal indicative of the output signal; and predicting that the magnitude of the signal indicative of the output signal will cross the predetermined threshold magnitude based on the future value. ### Claim 6 (depends on 2) The audio amplifier circuit of claim 2, wherein the control circuit is configured to predict the condition of the signal indicative of the output signal crossing the predetermined threshold magnitude by: tracking a signal envelope of the signal indicative of the output signal; extrapolating from the envelope a future value of the magnitude of the signal indicative of the output signal; and predicting that the magnitude of the signal indicative of the output signal will cross the predetermined threshold magnitude based on the future value. ### Claim 7 (depends on 2) The audio amplifier circuit of claim 2, wherein the condition for changing the power supply voltage comprises the magnitude of the signal indicative of the output signal lacking a persistent pattern of magnitude relative to the predetermined threshold magnitude. ### Claim 8 (depends on 7) The audio amplifier circuit of claim 7, wherein the control circuit is further configured to detect the persistent pattern. ### Claim 9 (depends on 1) The audio amplifier circuit of claim 1, wherein the control circuit is configured to detect the approximate zero crossing based on an electrical parameter associated with the charge pump power supply. ### Claim 10 (depends on 9) The audio amplifier circuit of claim 9, wherein the electrical parameter comprises one of: a voltage of a voltage source supplying power to the charge pump power supply, a current delivered by the voltage source, a fly capacitor voltage associated with a fly capacitor coupled to the charge pump power supply, a fly capacitor voltage associated with a fly capacitor coupled to the charge pump power supply, and a current associated with a switch of the charge pump power supply. ### Claim 11 (depends on 1) The audio amplifier circuit of claim 1, wherein the control circuit is further configured to: predict, based on a magnitude of a signal indicative of the output signal, an occurrence of a second condition for changing the power supply voltage; and responsive to predicting the occurrence of the second condition, change, at an approximate zero crossing of the signal indicative of the output signal, the power supply voltage to be equal to a third supply voltage. ### Claim 12 (depends on 11) The audio amplifier circuit of claim 11, wherein: the condition for changing the power supply voltage comprises the magnitude of the signal indicative of the output signal increasing from below a predetermined threshold magnitude to above the predetermined threshold magnitude; and the second condition for changing the power supply voltage comprises the magnitude of the signal indicative of the output signal increasing from below a second predetermined threshold magnitude to above the second predetermined threshold magnitude, wherein the second predetermined threshold magnitude is greater than the predetermined threshold magnitude. ### Claim 13 (depends on 12) The audio amplifier circuit of claim 12, wherein the control circuit is further configured to: predict, based on a magnitude of a signal indicative of the output signal, an occurrence of a third condition for changing the power supply voltage, wherein the third condition for changing the power supply voltage comprises the magnitude of the signal indicative of the output signal decreasing from above the predetermined threshold magnitude to below the predetermined threshold magnitude; and responsive to predicting the occurrence of the third condition, change, at an approximate zero crossing of the signal indicative of the output signal occurs, the power supply voltage to the first supply voltage. ### Claim 14 (depends on 13) The audio amplifier circuit of claim 13, wherein the control circuit is further configured to: predict, based on a magnitude of a signal indicative of the output signal, an occurrence of a fourth condition for changing the power supply voltage, wherein the fourth condition for changing the power supply voltage comprises the magnitude of the signal indicative of the output signal decreasing from above the second predetermined threshold magnitude to below the second predetermined threshold magnitude; and responsive to predicting the occurrence of the fourth condition, change, at an approximate zero crossing of the signal indicative of the output signal occurs, the power supply voltage to the second supply voltage. ### Claim 15 (depends on 1) The audio amplifier circuit of claim 1, wherein the condition for changing the power supply voltage comprises the magnitude of the signal indicative of the output signal refraining from crossing a predetermined threshold magnitude for a period of time. ### Claim 16 (depends on 15) The audio amplifier circuit of claim 15, wherein the control circuit is further configured to: initialize a timer of a predetermined duration responsive to the magnitude of the signal indicative of the output signal decreasing from above the predetermined threshold magnitude to below the predetermined threshold magnitude; responsive to the magnitude of the signal indicative of the output signal increasing from below a second predetermined threshold magnitude lesser than the predetermined threshold magnitude to above the second predetermined threshold magnitude before expiration of the timer, reinitialize the timer for the predetermined duration; and responsive to the expiration of the timer, change the power supply voltage at an approximate zero crossing of the signal indicative of the output signal. ### Claim 17 (depends on 15) The audio amplifier circuit of claim 15, wherein the control circuit is further configured to: initialize a timer of a predetermined duration responsive to the magnitude of the signal indicative of the output signal decreasing from above the predetermined threshold magnitude to below the predetermined threshold magnitude; and responsive to the expiration of the timer prior to the signal indicative of the output signal increasing from below the predetermined threshold magnitude to above the predetermined threshold magnitude, change the power supply voltage at an approximate zero crossing of the signal indicative of the output signal. ### Claim 18 (depends on 15) The audio amplifier circuit of claim 15, wherein the control circuit is further configured to: initialize a timer of a predetermined duration responsive to the magnitude of the signal indicative of the output signal crossing the predetermined threshold magnitude; and responsive to the expiration of the timer prior to the signal indicative of the output signal again crossing the predetermined threshold magnitude, change the power supply voltage at an approximate zero crossing of the signal indicative of the output signal. ### Claim 19 A method comprising: in an audio amplifier circuit including a power amplifier having an audio input for receiving an audio input signal, an audio output for generating an output signal based on the audio input signal, and a power supply input for receiving a power supply voltage wherein the power supply voltage is variable among at least a first supply voltage and a second supply voltage greater than the first supply voltage, and wherein the power supply voltage is generated by a configurable charge pump power supply: predicting, based on one or more characteristics of a signal indicative of the output signal, an occurrence of a condition for changing the power supply voltage; and responsive to predicting the occurrence of the condition, changing, at an approximate zero crossing of the signal indicative of the output signal, the power supply voltage. ### Claim 20 (depends on 19) The method of claim 19, wherein: the condition for changing the power supply voltage comprises the magnitude of the signal indicative of the output signal crossing a predetermined threshold magnitude; and wherein the signal indicative of the output signal is an electrical parameter associated with the charge pump power supply. ### Claim 21 (depends on 20) The method of claim 20, wherein the electrical parameter comprises one of: a voltage of a voltage source supplying power to the charge pump power supply, a current delivered by the voltage source, a fly capacitor voltage associated with a fly capacitor coupled to the charge pump power supply, a fly capacitor voltage associated with a fly capacitor coupled to the charge pump power supply, and a current associated with a switch of the charge pump power supply. ### Claim 22 (depends on 20) The method of claim 20, further comprising predicting the condition of the signal indicative of the output signal crossing the predetermined threshold magnitude responsive to the magnitude of the signal indicative of the output signal increasing above a second predetermined threshold magnitude less than the predetermined threshold magnitude. ### Claim 23 (depends on 20) The method of claim 20, further comprising predicting the condition of the signal indicative of the output signal crossing the predetermined threshold magnitude responsive to the magnitude of the signal indicative of the output signal decreasing below a second predetermined threshold magnitude greater than the predetermined threshold magnitude. ### Claim 24 (depends on 20) The method of claim 20, further comprising predicting the condition of the signal indicative of the output signal crossing the predetermined threshold magnitude by: tracking signal peaks of the signal indicative of the output signal; extrapolating from the signal peaks a future value of the magnitude of the signal indicative of the output signal; and predicting that the magnitude of the signal indicative of the output signal will cross the predetermined threshold magnitude based on the future value. ### Claim 25 (depends on 20) The method of claim 20, further comprising predicting the condition of the signal indicative of the output signal crossing the predetermined threshold magnitude by: tracking a signal envelope of the signal indicative of the output signal; extrapolating from the envelope a future value of the magnitude of the signal indicative of the output signal; and predicting that the magnitude of the signal indicative of the output signal will cross the predetermined threshold magnitude based on the future value. ### Claim 26 (depends on 20) The method of claim 20, wherein the condition for changing the power supply voltage comprises the magnitude of the signal indicative of the output signal lacking a persistent pattern of magnitude relative to the predetermined threshold magnitude. ### Claim 27 (depends on 26) The method of claim 26, further comprising detecting the persistent pattern. ### Claim 28 (depends on 19) The method of claim 19, wherein detecting the approximate zero crossing comprises detecting the approximately zero crossing based on an electrical parameter associated with the charge pump power supply. ### Claim 29 (depends on 28) The method of claim 28, wherein the electrical parameter comprises one of: a voltage of a voltage source supplying power to the charge pump power supply, a current delivered by the voltage source, a fly capacitor voltage associated with a fly capacitor coupled to the charge pump power supply, a fly capacitor voltage associated with a fly capacitor coupled to the charge pump power supply, and a current associated with a switch of the charge pump power supply. ### Claim 30 (depends on 19) The method of claim 19, further comprising: predicting, based on a magnitude of a signal indicative of the output signal, an occurrence of a second condition for changing the power supply voltage; and responsive to predicting the occurrence of the second condition, changing, at an approximate zero crossing of the signal indicative of the output signal, the power supply voltage to be equal to a third supply voltage. ### Claim 31 (depends on 30) The method of claim 30, wherein: the condition for changing the power supply voltage comprises the magnitude of the signal indicative of the output signal increasing from below a predetermined threshold magnitude to above the predetermined threshold magnitude; and the second condition for changing the power supply voltage comprises the magnitude of the signal indicative of the output signal increasing from below a second predetermined threshold magnitude to above the second predetermined threshold magnitude, wherein the second predetermined threshold magnitude is greater than the predetermined threshold magnitude. ### Claim 32 (depends on 31) The method of claim 31, further comprising: predicting, based on a magnitude of a signal indicative of the output signal, an occurrence of a third condition for changing the power supply voltage, wherein the third condition for changing the power supply voltage comprises the magnitude of the signal indicative of the output signal decreasing from above the predetermined threshold magnitude to below the predetermined threshold magnitude; and responsive to predicting the occurrence of the third condition, changing, at an approximate zero crossing of the signal indicative of the output signal occurs, the power supply voltage to the first supply voltage. ### Claim 33 (depends on 32) The method of claim 32, further comprising: predicting, based on a magnitude of a signal indicative of the output signal, an occurrence of a fourth condition for changing the power supply voltage, wherein the fourth condition for changing the power supply voltage comprises the magnitude of the signal indicative of the output signal decreasing from above the second predetermined threshold magnitude to below the second predetermined threshold magnitude; and responsive to predicting the occurrence of the fourth condition, changing, at an approximate zero crossing of the signal indicative of the output signal occurs, the power supply voltage to the second supply voltage. ### Claim 34 (depends on 32) The method of claim 32, wherein the condition for changing the power supply voltage comprises the magnitude of the signal indicative of the output signal refraining from crossing a predetermined threshold magnitude for a period of time. ### Claim 35 (depends on 34) The method of claim 34, further comprising: initializing a timer of a predetermined duration responsive to the magnitude of the signal indicative of the output signal decreasing from above the predetermined threshold magnitude to below the predetermined threshold magnitude; responsive to the magnitude of the signal indicative of the output signal increasing from below a second predetermined threshold magnitude lesser than the predetermined threshold magnitude to above the second predetermined threshold magnitude before expiration of the timer, reinitializing the timer for the predetermined duration; and responsive to the expiration of the timer, changing the power supply voltage at an approximate zero crossing of the signal indicative of the output signal. ### Claim 36 (depends on 34) The method of claim 34, further comprising: initializing a timer of a predetermined duration responsive to the magnitude of the signal indicative of the output signal decreasing from above the predetermined threshold magnitude to below the predetermined threshold magnitude; and responsive to the expiration of the timer prior to the signal indicative of the output signal increasing from below the predetermined threshold magnitude to above the predetermined threshold magnitude, changing the power supply voltage at an approximate zero crossing of the signal indicative of the output signal. ### Claim 37 (depends on 34) The method of claim 34, further comprising: initializing a timer of a predetermined duration responsive to the magnitude of the signal indicative of the output signal crossing the predetermined threshold magnitude; and responsive to the expiration of the timer prior to the signal indicative of the output signal again crossing the predetermined threshold magnitude, changing the power supply voltage at an approximate zero crossing of the signal indicative of the output signal.