# US 11,451,200 B2 · Low pop-click noise class-D amplifier > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,451,200 B2 - Document ID: US11451200B2 - Status: Granted - Kind: B2 - Application number: 17/132,166 - Filed: 2020-12-23 - Published: 2021-08-26 - Granted: 2022-09-20 - Earliest claimed: 2020-02-25 - Assignees: Mediatek Inc. - Applicants: Mediatek Inc. - Inventors: Fong-Wen Lee; Kuan-Ta Chen - Web page: https://patentgrep.com/patent/US11451200B2 ## CPC - H03F 3/183: with semiconductor devices only - H03F 3/2171: {with field-effect devices (H03F3/2173 - H03F3/2178 take precedence)} - H03F 1/26: Modifications of amplifiers to reduce influence of noise generated by amplifying elements - H03F 1/305: {in case of switching on or off of a power supply} - H03F 1/342: {in field-effect transistor amplifiers} - H03F 3/2173: {of the bridge type} - H03F 3/72: Gated amplifiers, i.e. amplifiers which are rendered operative or inoperative by means of a control signal - H03G 3/348: {Muting in response to a mechanical action or to power supply variations, e.g. during tuning; Click removal circuits} - H04R 3/02: for preventing acoustic reaction {, i.e. acoustic oscillatory feedback (specially adapted for hearing aids H04R25/453)} - H03F 2200/03: the amplifier being designed for audio applications - H03F 2200/156: One or more switches are realised in the feedback circuit of the amplifier stage - H03F 2200/351: Pulse width modulation being used in an amplifying circuit - H03F: AMPLIFIERS - H03G: CONTROL OF AMPLIFICATION - 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 class-D amplifier with low pop-click noise is shown. A loop filter, a control signal generator, a first power driver, and a first feedback circuit are provided within the class-D amplifier to establish a first loop for signal amplification. The class-D amplifier further has a settling circuit and a pre-charging circuit. The settling circuit is configured to be combined with the loop filer and the control signal generator to establish a second loop to settle the loop filter and the control signal generator before the first loop is enabled. The pre-charging circuit is configured to pre-charge a positive output terminal and a negative output terminal of the first power driver. ## Claims ### Claim 1 A class-D amplifier, comprising: a loop filter, a control signal generator, a first power driver, and a first feedback circuit, configured to establish a first loop for signal amplification; a settling circuit, configured to be combined with the loop filer and the control signal generator to establish a second loop to settle the loop filter and the control signal generator before the first loop is enabled; a pre-charging circuit, configured to pre-charge a positive output terminal and a negative output terminal of the first power driver which are a first positive feedback terminal and a second negative feedback terminal, respectively; wherein: the pre-charging circuit pre-charges the positive output terminal and the negative output terminal of the first power driver to a common voltage; the second loop is disabled when the first loop is enabled; the settling circuit includes a second power driver and a second feedback circuit; the second power driver is controlled by the control signal generator when the second loop is enabled, to output a second feedback signal; and the second feedback circuit couples the second feedback signal to the loop filter when the second loop is enabled. ### Claim 2 (depends on 1) The class-D amplifier as claimed in claim 1, wherein: via the pre-charging circuit, a common-mode terminal of the second power driver is coupled to the positive output terminal and the negative output terminal of the first power driver to pre-charge the positive output terminal and the negative output terminal of the first power driver to the common voltage. ### Claim 3 (depends on 2) The class-D amplifier as claimed in claim 2, wherein the second power driver comprises: a second positive feedback terminal and a second negative feedback terminal, operative to output the second feedback signal to be transferred by the second feedback circuit; and a first resistor and a second resistor, coupled in series between the second positive feedback terminal and the second negative feedback terminal, wherein a connection terminal between the first resistor and the second resistor is the common-mode terminal of the second power driver. ### Claim 4 (depends on 3) The class-D amplifier as claimed in claim 3, wherein: the first power driver comprises a first metal-oxide-silicon transistor, a second metal-oxide-silicon transistor, a third metal-oxide-silicon transistor, and a fourth metal-oxide-silicon transistor; when the first loop is enabled, the first metal-oxide-silicon transistor is controlled according to a first control signal generated by the control signal generator to couple the positive output terminal of the first power driver to a power supply terminal; when the first loop is enabled, the second metal-oxide-silicon transistor is controlled according to a second control signal generated by the control signal generator to couple the positive output terminal of the first power driver to a ground terminal; when the first loop is enabled, the third metal-oxide-silicon transistor is controlled according to a third control signal generated by the control signal generator to couple the negative output terminal of the first power driver to the power supply terminal; and when the first loop is enabled, the fourth metal-oxide-silicon transistor is controlled according to a fourth control signal generated by the control signal generator to couple the negative output terminal of the first power driver to the ground terminal. ### Claim 5 (depends on 4) The class-D amplifier as claimed in claim 4, wherein: the second power driver comprises a fifth metal-oxide-silicon transistor, a sixth metal-oxide-silicon transistor, a seventh metal-oxide-silicon transistor, and an eighth metal-oxide-silicon transistor; when the second loop is enabled, the fifth metal-oxide-silicon transistor is controlled by the first control signal to couple the second positive feedback terminal to the power supply terminal; when the second loop is enabled, the sixth metal-oxide-silicon transistor is controlled by the second control signal to couple the second positive feedback terminal to the ground terminal; when the second loop is enabled, the seventh metal-oxide-silicon transistor is controlled by the third control signal to couple the second negative feedback terminal to the power supply terminal; and when the second loop is enabled, the eighth metal-oxide-silicon transistor is controlled by the fourth control signal to couple the second negative feedback terminal to the ground terminal. ### Claim 6 (depends on 5) The class-D amplifier as claimed in claim 5, wherein: the second feedback circuit comprises a third resistor and a fourth resistor; when the second loop is enabled, the third resistor couples the second positive feedback terminal to a negative input terminal of the loop filter, and the fourth resistor couples the second negative feedback terminal to a positive input terminal of the loop filter; and a positive input terminal of the class-D amplifier is coupled to the positive input terminal of the loop filter, and a negative input terminal of the class-D amplifier is coupled to the negative input terminal of the loop filter. ### Claim 7 (depends on 1) The class-D amplifier as claimed in claim 1, wherein: the second power driver comprises a second positive feedback terminal and a second negative feedback terminal, operative to output the second feedback signal to be transferred by the second feedback circuit; and after the positive output terminal and the negative output terminal of the first power driver are pre-charged to the common voltage, if the control signal generator operates the second power driver to set the second positive feedback terminal and the second negative feedback terminal both to the common voltage, the first loop is enabled and the second loop is disabled. ### Claim 8 (depends on 1) The class-D amplifier as claimed in claim 1, wherein: the first power driver comprises a first metal-oxide-silicon transistor, a second metal-oxide-silicon transistor, a third metal-oxide-silicon transistor, and a fourth metal-oxide-silicon transistor; when the first loop is enabled, the first metal-oxide-silicon transistor is controlled according to a first control signal generated by the control signal generator to couple the positive output terminal of the first power driver to a power supply terminal; when the first loop is enabled, the second metal-oxide-silicon transistor is controlled according to a second control signal generated by the control signal generator to couple the positive output terminal of the first power driver to a ground terminal; when the first loop is enabled, the third metal-oxide-silicon transistor is controlled according to a third control signal generated by the control signal generator to couple the negative output terminal of the first power driver to the power supply terminal; and when the first loop is enabled, the fourth metal-oxide-silicon transistor is controlled according to a fourth control signal generated by the control signal generator to couple the negative output terminal of the first power driver to the ground terminal. ### Claim 9 (depends on 8) The class-D amplifier as claimed in claim 8, wherein the second power driver comprises: a second positive feedback terminal and a second negative feedback terminal, operative to output the second feedback signal to be transferred by the second feedback circuit; an impedance device, coupled between the second positive feedback terminal and the second negative feedback terminal; and a fifth metal-oxide-silicon transistor, a sixth metal-oxide-silicon transistor, a seventh metal-oxide-silicon transistor, and an eighth metal-oxide-silicon transistor, wherein: when the second loop is enabled, the fifth metal-oxide-silicon transistor is controlled by the first control signal to couple the second positive feedback terminal to the power supply terminal; when the second loop is enabled, the sixth metal-oxide-silicon transistor is controlled by the second control signal to couple the second positive feedback terminal to the ground terminal; when the second loop is enabled, the seventh metal-oxide-silicon transistor is controlled by the third control signal to couple the second negative feedback terminal to the power supply terminal; and when the second loop is enabled, the eighth metal-oxide-silicon transistor is controlled by the fourth control signal to couple the second negative feedback terminal to the ground terminal. ### Claim 10 (depends on 9) The class-D amplifier as claimed in claim 9, wherein: by operating the pre-charging circuit, the positive output terminal and the negative output terminal of the first power driver are coupled to the power supply terminal for pre-charging; and after the pre-charging, the first loop is enabled if the first, second, third and fourth control signals all are low. ### Claim 11 (depends on 10) The class-D amplifier as claimed in claim 10, wherein the pre-charging circuit comprises: a first switch, coupled between a gate of the first metal-oxide-silicon transistor and the ground terminal; and a second switch, coupled between a gate of the third metal-oxide-silicon transistor and the ground terminal, wherein the first switch and the second switch are turned on when the positive output terminal and the negative output terminal of the first power driver are pre-charged. ### Claim 12 (depends on 10) The class-D amplifier as claimed in claim 10, wherein: the second feedback circuit comprises a third resistor and a fourth resistor; when the second loop is enabled, the third resistor couples the second positive feedback terminal to a negative input terminal of the loop filter, and the fourth resistor couples the second negative feedback terminal to a positive input terminal of the loop filter; and a positive input terminal of the class-D amplifier is coupled to the positive input terminal of the loop filter, and a negative input terminal of the class-D amplifier is coupled to the negative input terminal of the loop filter. ### Claim 13 (depends on 9) The class-D amplifier as claimed in claim 9, wherein: by operating the pre-charging circuit, the positive output terminal and the negative output terminal of the first power driver are coupled to the ground terminal for pre-charging; and after the pre-charging, the first loop is enabled when the first, second, third and fourth control signals all are high. ### Claim 14 (depends on 13) The class-D amplifier as claimed in claim 13, wherein the pre-charging circuit comprises: a first switch, coupled between a gate of the second metal-oxide-silicon transistor and the power supply terminal; and a second switch, coupled between a gate of the fourth metal-oxide-silicon transistor and the power supply terminal, wherein the first switch and the second switch are turned on when the positive output terminal and the negative output terminal of the first power driver are pre-charged. ### Claim 15 (depends on 13) The class-D amplifier as claimed in claim 13, wherein: the second feedback circuit comprises a third resistor and a fourth resistor; when the second loop is enabled, the third resistor couples the second positive feedback terminal to a negative input terminal of the loop filter, and the fourth resistor couples the second negative feedback terminal to a positive input terminal of the loop filter; and a positive input terminal of the class-D amplifier is coupled to the positive input terminal of the loop filter, and a negative input terminal of the class-D amplifier is coupled to the negative input terminal of the loop filter.