Minimizing crossover distortion in a class B current driver

Patent metadata

Field	Value
Publication number	US-11070177-B2
Application number	US-201916562856-A
Country	US
Kind code	B2
Filing date	Sep 6, 2019
Priority date	Sep 6, 2019
Publication date	Jul 20, 2021
Grant date	Jul 20, 2021

Abstract

A system may include an output stage comprising a single-ended driver for driving a load at an output of the output stage, a loop filter coupled at its input to the output of the output stage and configured to minimize an error between a target current signal received by the loop filter and an output current driven on the load, and control circuitry configured to, when the load current is driven in a manner such that the load current changes polarity, reset a state variable of the loop filter.

First claim

What is claimed is:

1. A system comprising:
an output stage comprising a single-ended driver for driving a load at an output of the output stage;
a loop filter coupled at its input to the output of the output stage and configured to minimize an error between a target current signal received by the loop filter and an output current driven on the load; and
control circuitry configured to, when the load current is driven in a manner such that the load current changes polarity, reset a state variable of the loop filter.

2. The system of claim 1 , wherein the loop filter comprises a proportional-integral-derivative controller.

3. The system of claim 1 , wherein the control circuitry is configured to reset the state variable of the loop filter by driving the target current signal to an artificial level outside a normal operating range of the target current signal level.

4. The system of claim 3 , wherein driving the target current signal to the artificial level avoids a discontinuity associated with the loop filter.

5. The system of claim 4 , wherein the discontinuity associated with the loop filter comprises a discontinuity in an input to the loop filter.

6. The system of claim 3 , further wherein driving the target current signal to the artificial level shortens a time required to reset the state variable as compared to absence of driving with the artificial level.

7. The system of claim 4 , further wherein driving the target current signal to the artificial level avoids glitches occurring at the output.

8. A method comprising:
driving a load at an output of an output stage with a single-ended driver of the output stage;
minimizing an error between a target current signal and an output current driven on the load by a loop filter coupled at its input to the output of the output stage; and
when the load current is driven in a manner such that the load current changes polarity, resetting a state variable of the loop filter.

9. The method of claim 8 , wherein the loop filter comprises a proportional-integral-derivative controller.

10. The method of claim 8 , further comprising resetting the state variable of the loop filter by driving the target current signal to an artificial level outside a normal operating range of the target current signal level.

11. The method of claim 10 , wherein driving the target current signal to the artificial level avoids a discontinuity associated with the loop filter.

12. The method of claim 11 , wherein the discontinuity associated with the loop filter comprises a discontinuity in an input to the loop filter.

13. The method of claim 11 , further wherein driving the target current signal to the artificial level shortens a time required to reset the state variable as compared to absence of driving with the artificial level.

14. The method of claim 11 , further wherein driving the target current signal to the artificial level avoids glitches occurring at the output.

15. A device comprising:
a camera; and
a camera module for controlling the camera, the camera module including a control subsystem comprising:
an output stage comprising a single-ended driver for driving a load at an output of the output stage;
a loop filter coupled at its input to the output of the output stage and configured to minimize an error between a target current signal received by the loop filter and an output current driven on the load; and
control circuitry configured to, when the load current is driven in a manner such that the load current changes polarity, reset a state variable of the loop filter.

16. The device of claim 15 , wherein the loop filter comprises a proportional-integral-derivative controller.

17. The device of claim 15 , wherein the control circuitry is configured to reset the state variable of the loop filter by driving the target current signal to an artificial level outside a normal operating range of the target current signal level.

18. The device of claim 15 , wherein driving the target current signal to the artificial level avoids a discontinuity associated with the loop filter.

19. The device of claim 18 , wherein the discontinuity associated with the loop filter comprises a discontinuity in an input to the loop filter.

20. The device of claim 18 , further wherein driving the target current signal to the artificial level shortens a time required to reset the state variable as compared to absence of driving with the artificial level.

21. The device of claim 18 , further wherein driving the target current signal to the artificial level avoids glitches occurring at the output.

Assignees

• Cirrus Logic Int Semiconductor Ltd
• Cirrus Logic Inc

Inventors

• Singh Saurabh
• Parupalli Vamsikrishna
• Kenly Stewart
• Smith Eric B

Classifications

• G03B30/00

  Camera modules comprising integrated lens units and imaging units, specially adapted for being embedded in other devices, e.g. mobile phones or vehicles · CPC title

• G03B3/10

  Power-operated focusing · CPC title

• H03F2200/351

  Pulse width modulation being used in an amplifying circuit · CPC title

• G02B7/04

  with mechanism for focusing or varying magnification · CPC title

• H03F2200/33

  Bridge form coupled amplifiers; H-form coupled amplifiers · CPC title