Minimizing crossover distortion in a class B current driver
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.
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.