Delta-based current steering for power converter peak/valley current control
A power converter system for converting an input voltage at an input into an output voltage at an output may comprise a switch network comprising a reactive circuit element and a plurality of switches, switch control circuitry configured to operate the plurality of switch in a plurality of periodic, sequential states to regulate the output voltage, and reference current generating circuitry. The reference current generating circuitry may include a comparator coupled to a sensed switch of the plurality of switches and configured to compare a current flowing through the sensed switch to a reference current and current-steering circuitry coupled to the comparator configured to generate the reference current and alternate the reference current between a first reference current and a second reference current whenever the switch control circuitry changes from one state of the plurality of periodic, sequential states to another state of the plurality of periodic, sequential states.
1. A power converter system for converting an input voltage at an input of the power converter system into an output voltage at an output of the power converter system, the power converter system comprising:
a switch network comprising a reactive circuit element and a plurality of switches;
switch control circuitry configured to operate the plurality of switches in a plurality of periodic, sequential states to regulate the output voltage; and
reference current generating circuitry comprising:
a comparator coupled to a sensed switch of the plurality of switches and configured to compare a current flowing through the sensed switch to a reference current; and
current-steering circuitry coupled to the comparator configured to generate the reference current and alternate the reference current between a first reference current and a second reference current whenever the switch control circuitry changes from one state of the plurality of periodic, sequential states to another state of the plurality of periodic, sequential states.
2. The power converter system of claim 1 , wherein:
the first reference current defines a minimum target current for the current; and
the second reference current defines a maximum target current for the current.
3. The power converter system of claim 1 , further comprising:
a first sensing switch coupled between a first terminal of the sensed switch and a first terminal of the comparator, wherein the first sensing switch is controlled by a control signal that also controls the sensed switch; and
a second sensing switch coupled between a second terminal of the sensed switch and a second terminal of the comparator, wherein the second sensing switch is controlled by the control signal.
4. The power converter system of claim 1 , wherein:
the reactive circuit element comprises a power inductor; and
the current flows through the power inductor.
5. The power converter system of claim 1 , wherein the switch network comprises a multi-level power converter.
6. The power converter system of claim 5 , wherein the switch network comprises:
a switching node, wherein the power inductor is coupled between the switching node and the output;
a flying capacitor having a first flying capacitor terminal and a second flying capacitor terminal;
a first switch coupled between the input and the first flying capacitor terminal;
a second switch coupled between the first flying capacitor terminal and the switching node;
a third switch coupled between the second flying capacitor terminal and the switching node; and
a fourth switch coupled between the second flying capacitor terminal and a ground voltage.
7. The power converter system of claim 6 , wherein the sensed switch comprises the first switch.
8. The power converter system of claim 6 , wherein the sensed switch comprises the fourth switch.
9. The power converter system of claim 1 , wherein the current-steering circuitry is implemented with a current digital-to-analog converter.
10. The power converter system of claim 1 , wherein the current-steering circuitry comprises:
a first current source configured to generate the first reference current;
a second current source configured to generate a ripple reference current equal to a difference between the second reference current and the first reference current; and
a network of current-steering switches configured to:
in at least a first state of the plurality of periodic, sequential states, steer the first reference current generated by the first current source to an electrical node coupled to an input terminal of the comparator; and
in at least a second state of the plurality of periodic, sequential states, steer the first reference current generated by the first current source and the ripple reference current generated by the second current source to the electrical node.
11. The power converter system of claim 1 , wherein the reactive circuit element comprises a power inductor.
12. The power converter system of claim 1 , wherein the reactive circuit element comprises a capacitor.
13. A method, in a power converter system for converting an input voltage at an input of the power converter system into an output voltage at an output of the power converter system, wherein the power converter system comprises a switch network comprising a reactive circuit element and a plurality of switches and switch control circuitry configured to operate the plurality of switches in a plurality of periodic, sequential states to regulate the output voltage, the method comprising:
comparing a current flowing through a sensed switch to a reference current with a comparator coupled to the sensed switch of the plurality of switches; and
generating, with current-steering circuitry coupled to the comparator, the reference current and alternating the reference current between a first reference current and a second reference current whenever the switch control circuitry changes from one state of the plurality of periodic, sequential states to another state of the plurality of periodic, sequential states.
14. The method of claim 13 , wherein:
the first reference current defines a minimum target current for the current; and
the second reference current defines a maximum target current for the current.
15. The method of claim 13 , wherein:
the power converter system further comprises a first sensing switch coupled between a first terminal of the sensed switch and a first terminal of the comparator and a second sensing switch coupled between a second terminal of the sensed switch and a second terminal of the comparator; and
the method further comprising controlling the first sensing switch by a control signal that also controls the sensed switch and controlling the second sensing switch with the control signal.
16. The method of claim 13 , wherein:
the reactive circuit element comprises a power inductor; and
the current flows through the power inductor.
17. The method of claim 13 , wherein the switch network comprises a multi-level power converter.
18. The method of claim 17 , wherein the switch network comprises:
a switching node, wherein the power inductor is coupled between the switching node and the output;
a flying capacitor having a first flying capacitor terminal and a second flying capacitor terminal;
a first switch coupled between the input and the first flying capacitor terminal;
a second switch coupled between the first flying capacitor terminal and the switching node;
a third switch coupled between the second flying capacitor terminal and the switching node; and
a fourth switch coupled between the second flying capacitor terminal and a ground voltage.
19. The method of claim 18 , wherein the sensed switch comprises the first switch.
20. The method of claim 18 , wherein the sensed switch comprises the fourth switch.
21. The method of claim 13 , wherein the current-steering circuitry is implemented with a current digital-to-analog converter.
22. The method of claim 13 , wherein the current-steering circuitry comprises:
a first current source configured to generate the first reference current;
a second current source configured to generate a ripple reference current equal to a difference between the second reference current and the first reference current; and
a network of current-steering switches configured to:
in at least a first state of the plurality of periodic, sequential states, steer the first reference current generated by the first current source to an electrical node coupled to an input terminal of the comparator; and
in at least a second state of the plurality of periodic, sequential states, steer the first reference current generated by the first current source and the ripple reference current generated by the second current source to the electrical node.
23. The method of claim 13 , wherein the reactive circuit element comprises a power inductor.
24. The method of claim 13 , wherein the reactive circuit element comprises a capacitor.
25. A circuit comprising:
a plurality of switches;
switch control circuitry configured to operate the plurality of switches in a plurality of different switch states; and
reference current generating circuitry comprising:
a comparator coupled to a sensed switch of the plurality of switches and configured to compare a current flowing through the sensed switch to a reference current; and
current-steering circuitry coupled to the comparator configured to generate the reference current and alternate the reference current between a first reference current and a second reference current whenever the switch control circuitry changes from one switch state to another switch state.
26. A method, for a circuit comprising a plurality of switches and switch control circuitry configured to operate the plurality of switches in a plurality of different switch states, the method comprising:
comparing a current flowing through a sensed switch to a reference current with a comparator coupled to the sensed switch of the plurality of switches; and
generating, with current-steering circuitry coupled to the comparator, the reference current and alternating the reference current between a first reference current and a second reference current whenever the switch control circuitry changes from one switch state to another switch state.