Transition smoothing apparatus for reducing spurious input to a system under feedback control

Patent metadata

Field	Value
Publication number	US-12081228-B2
Application number	US-202217934601-A
Country	US
Kind code	B2
Filing date	Sep 23, 2022
Priority date	Sep 29, 2021
Publication date	Sep 3, 2024
Grant date	Sep 3, 2024

Abstract

Transition smoothing apparatus for reducing spurious input to a system under feedback control connected to a control loop. The apparatus includes a loop filter to integrate an error between an input signal applied to the loop filter and an output signal of the system under feedback control, an analog-to-digital converter to provide digitized integrated error values, a controller to generate output values supplied to the system under feedback control in response to the digitized integrated error values and in a start-up sequence to control a feedback digital-to-analog converter according to the digitized integrated error values to supply a first control signal to the loop filter and control the system under feedback control to generate a second control signal, and an alignment detector to detect phase alignment between the first control signal and the second control signal to control a smooth transition into closed loop operation of the control loop.

First claim

What is claimed is:

1. A transition smoothing apparatus for reducing spurious input to a system under feedback control connected to a control loop of the transition smoothing apparatus comprising:
a loop filter to integrate an error between an input signal applied to the loop filter and an output signal of the system under feedback control;
an analog-to-digital converter to digitize the integrated error every loop cycle of the control loop to provide a digitized integrated error value;
a controller to generate in a normal operation mode output values supplied to the system under feedback control in response to the digitized integrated error values and adapted in a start-up sequence to control a feedback digital-to-analog converter of the control loop according to the digitized integrated error values to supply a first control signal to the loop filter of the control loop and to control the system under feedback control to generate an independent second control signal; and
an alignment detector to detect a phase alignment between the first control signal provided by the feedback digital-to-analog converter of the control loop and the second control signal provided by the system under feedback control to control a smooth transition into a closed loop operation of the control loop in the normal operation mode during the start-up sequence with reduced spurious input to the system under feedback control.

2. The transition smoothing apparatus according to claim 1 wherein the alignment detector is integrated in the controller of the control loop of the transition smoothing apparatus.

3. The transition smoothing apparatus according to claim 1 wherein the loop filter includes an analog low pass filter.

4. The transition smoothing apparatus according to claim 1 wherein the analog-to-digital converter of the control loop is adapted to supply the digitized integrated error value every sample period to a digital input of the controller of the control loop.

5. The transition smoothing apparatus according to claim 4 wherein the digitized integrated error value supplied by the analog-to-digital converter to the digital input of the controller comprises an ADC code with an offset binary format.

6. The transition smoothing apparatus according to claim 1 wherein the controller includes a supply voltage monitoring and prediction circuit adapted to maintain a target voltage.

7. The transition smoothing apparatus according to claim 1 wherein the controller includes a common mode control circuit adapted to maintain a set-point common mode voltage.

8. The transition smoothing apparatus according to claim 1 wherein the system under feedback control is an H-bridge driver of a class D-amplifier including a positive H-bridge driver circuit having a positive output terminal and a negative H-bridge circuit having a negative output terminal.

9. The transition smoothing apparatus according to claim 8 wherein a loudspeaker is connected to the positive output terminal and to the negative output terminal of the H-bridge driver of the class D-amplifier.

10. The transition smoothing apparatus according to claim 8 wherein the controller is adapted to supply a first gray coded output value to the positive H-bridge driver circuit of the H-bridge driver and a second gray coded output value to the negative H-bridge driver circuit of the H-bridge driver of said class D-amplifier.

11. The transition smoothing apparatus according to claim 1 wherein the system under feedback control includes a Phase Locked Loop circuit.

12. The transition smoothing apparatus according to claim 1 wherein the analog-to-digital converter comprises a SAR analog-to-digital converter.

13. The transition smoothing noise reduction apparatus according to claim 1 wherein a control block of the transition smoothing apparatus is adapted to generate at least one start-up control signal applied to the controller to initiate during the start-up sequence a transition from an idle operation mode to the normal operation mode.

14. The transition smoothing apparatus according to claim 1 wherein the alignment detector is adapted to detect a phase alignment between a second fixed pattern control signal provided by the system under feedback control during the start-up sequence and the first control signal provided by the feedback digital-to-analog converter during the start-up sequence used to control during the start-up sequence a smooth transition from an idle operation mode to the normal operation mode with a reduced spurious input to the system under feedback control.

15. The transition smoothing apparatus according to claim 1 wherein a control block of the transition smoothing apparatus is adapted to generate a shutdown control signal applied to the controller to initiate in a shutdown sequence a transition from the normal operation mode to an idle operation mode.

16. The transition smoothing apparatus according to claim 1 wherein the controller is adapted to generate in the normal operation mode in response to the digitized integrated error values gray-coded output values supplied to the system under feedback control.

17. The transition smoothing apparatus according to claim 1 wherein the control loop of the transition smoothing apparatus comprises a PWM control loop including the loop filter, the analog-to-digital converter, the controller and the feedback digital-to-analog converter.

18. The transition smoothing apparatus according to claim 1 wherein the transition smoothing apparatus comprises a noise reduction apparatus adapted to reduce acoustic start-up noise forming spurious input to the system under feedback control.

19. An alignment detector adapted to detect a phase alignment between a first control signal provided by a feedback digital-to-analog converter of a control loop and a second control signal provided by a system under feedback control to control a smooth transition into a closed loop operation of the control loop in a normal operation mode during a start-up sequence with reduced spurious input to the system under feedback control.

20. The alignment detector according to claim 19 wherein the system under feedback control comprises an H-bridge driver of a class D-amplifier including a positive H-bridge driver circuit having a positive output terminal and a negative H-bridge circuit having a negative output terminal, wherein a loudspeaker is connected to the positive output terminal and to the negative output terminal of the H-bridge driver of said class D-amplifier.

21. The alignment detector according to claim 19 wherein the system under feedback control comprises a Phase Locked Loop circuit.

22. A class D-amplifier including a transition smoothing apparatus having a system under feedback control connected to a control loop, the transition smoothing apparatus comprising:
a loop filter to integrate an error between an input signal applied to the loop filter and an output signal of the system under feedback control;
an analog-to-digital converter adapted to digitize the integrated error every loop cycle of the control loop to provide a digitized integrated error value;
a controller to generate in a normal operation mode in response to the digitized integrated error values output values supplied to the system under feedback control and in a start-up sequence to control a feedback digital-to-analog converter of the control loop according to the digitized integrated error values to supply a first control signal to the loop filter of the

Assignees

• Skyworks Solutions Inc

Inventors

• Lee Wai Laing

Classifications

• H03M1/181

  in feedback mode, i.e. by determining the range to be selected from one or more previous digital output values · CPC title

• H03F3/2173 Primary

  of the bridge type · CPC title

• H03M3/346

  by suppressing active signals at predetermined times, e.g. muting, using non-overlapping clock phases · CPC title

• H03M3/426

  the quantiser being a successive approximation type analogue/digital converter · CPC title

• H03M3/432

  the quantiser being a pulse width modulation type analogue/digital converter, i.e. differential pulse width modulation · CPC title