Power converter with improved transient load response
A power converter which converts between a first current at a first voltage provided at a first node and a second current at a second voltage provided at a second node. The power converter has a flying capacitor, an inductor and five switches. Furthermore, the power converter has a control unit to control four switches during steady state operation within a sequence of different operations states, in order to set the second voltage or the second current to a target level. In addition, the control unit detects the occurrence of a load transient at the second node, and in reaction to detecting occurrence of a load transient, to at least partially close a bypass switch, in order to provide additional current from the flying capacitor to the second node or in order to divert current from the inductor towards the reference potential.
1. A power converter configured to convert between a first current (IN) at a first voltage provided at a first node and a second current (IouT) at a second voltage provided at a second node; wherein the first voltage and the second voltage are relative to a reference voltage; wherein the power converter comprises
a flying capacitor;
an inductor; wherein a second port of the inductor is coupled to the second node;
a first switch configured to couple or to decouple a first port of the flying capacitor to or from the first node;
a second switch configured to couple or to decouple the first port of the flying capacitor to or from a first port of the inductor;
a third switch configured to couple or to decouple a second port of the flying capacitor to or from the first port of the inductor;
a fourth switch configured to couple or to decouple the second port of the flying capacitor to or from the reference potential;
a bypass switch configured to couple or to decouple the second port of the flying capacitor to or from the second node; and
a control unit configured to
control the first, second, third and fourth switch during steady state operation within a sequence of different operations states, in order to set the second voltage or the second current to a target level;
detect occurrence of a load transient at the second node; and
in reaction to detecting occurrence of a load transient, at least partially close the bypass switch, in order to provide additional current from the flying capacitor to the second node or in order to divert current from the inductor towards the reference potential.
2. The power converter of claim 1 , wherein the control unit is configured to control the first, second, third and fourth switch during steady state operation in order to
set the second voltage to the target level; and
set a capacitor voltage across the flying capacitor to the difference between the first voltage and the target level for the second voltage minus a delta voltage.
3. The power converter of claim 2 , wherein
the delta voltage is 20%, 10% or less of the difference between the first voltage and the target level for the second voltage; and/or
the delta voltage is 1%, 2%, 5% or more of the difference between the first voltage and the target level for the second voltage.
4. The power converter of claim 1 , wherein the control unit is configured to control the first, second, third and fourth switch during steady state operation such that a capacitor voltage across the flying capacitor in combination with the first voltage is
higher than the target level for the second voltage;
high enough to allow current from the flying capacitor to flow to the second node, when the bypass switch is at least partially closed; and/or
sufficiently low to avoid conduction of a body diode of the bypass switch.
5. The power converter of claim 1 , wherein the bypass switch is maintained open during steady state operation.
6. The power converter of claim 1 , wherein the control unit is configured to
detect that the second voltage is at or below a lower voltage threshold and/or that the second current is at or above a higher current threshold; and
in reaction to this, at least partially close the bypass switch in order to provide additional current from the flying capacitor to the second node; and/or
detect that the second voltage is at or above a higher voltage threshold and/or that the second current is at or below a lower current threshold; and
in reaction to this, at least partially close the bypass switch in order to divert current from the inductor towards the reference potential.
7. The power converter of claim 1 , wherein
the control unit is configured to transition towards a current delivery operation state, subject to detecting a load increase; and
during the current delivery operation state the first switch is closed, the second switch is closed, the third switch is open, the fourth switch is open, and the bypass switch is at least partially closed; and/or
the control unit is configured to transition towards a current sink operation state, subject to detecting a load decrease; and
during the current sink operation state the first switch is open, the second switch is open, the third switch is open, the fourth switch is closed and the bypass switch is at least partially closed.
8. The power converter of claim 7 , wherein the control unit is configured to maintain the power converter in the current delivery operation state or in the current sink operation state until it is detected that the load transient at the second node has been overcome, notably until it is detected that the second voltage is at or above a lower voltage threshold and at or below a higher voltage threshold.
9. The power converter of claim 1 , wherein the control unit is configured to
detect that the load transient at the second node has been overcome; and
in reaction to this, resume steady state operation.
10. The power converter of claim 1 , wherein the control unit is configured to
operate the bypass switch in a linear mode with a variable on-resistance, notably in dependence of a level of the second voltage and/or in dependence of a level of a current through the bypass switch; or
operate the bypass switch in a pulse width modulation mode, with the bypass switch being either fully closed or fully open.
11. The power converter of claim 1 , wherein the sequence of operation states comprises
a first operation state, during which the first switch is closed, the second switch is open, the third switch is closed and the fourth switch is open; and
a second operation state, during which the first switch is open, the second switch is closed, the third switch is open and the fourth switch is closed.
12. The power converter of claim 11 , wherein the control unit is configured to adapt a duty cycle of the first and/or second operation states in order to regulate a capacitor voltage across the flying capacitor to a capacitor target level.
13. The power converter of claim 1 , wherein the sequence of operation states comprises
a third operation state, during which the first switch is closed, the second switch is closed, the third switch is open and the fourth switch is open; and/or
a fourth operation state, during which the first switch is open, the second switch is open, the third switch is closed and the fourth switch is closed.
14. The power converter of claim 13 , wherein the control unit is configured to adapt a duty cycle of the third and/or fourth operation states in order to regulate the second voltage or the second current to the target level.
15. The power converter of claim 1 , wherein the control unit is configured to
repeat the sequence of operation states during steady state operation at a cycle rate; and/or
determine an indication of a level of the second voltage using differential Kelvin contacts at a load which is supplied by the power converter; and/or
detect occurrence of a load transient at the second node based on an indication of a level of the second voltage.
16. A method for operating a power converter; wherein the power converter is configured to convert between a first current at a first voltage provided at a first node and a second current at a second voltage provided at a second node; wherein the first voltage and the second voltage are relative to a reference voltage; wherein the power converter comprises a flying capacitor and an inductor; wherein a second port of the inductor is coupled to the second node; wherein the power converter comprises a first switch configured to couple or to decouple a first port of the flying capacitor to or from the first node; a second switch configured to couple or to decouple the first port of the flying capacitor to or from a first port of the inductor; a third switch configured to couple or to decouple a second port of the flying capacitor to or from the first port of the inductor; a fourth switch configured to couple or to decouple the second port of the flying capacitor to or from the reference potential; and a bypass switch configured to couple or to decouple the second port of the flying capacitor to or from the second node; wherein the method comprises
controlling the first, second, third and fourth switch during steady state operation within a sequence of different operations states, in order to set the second voltage or the second current to a target level;
detecting occurrence of a load transient at the second node; and
in reaction to detecting occurrence of a load transient, at least partially closing the bypass switch in order to provide additional current from the flying capacitor to the second node or in order to divert current from the inductor towards the reference potential.
17. The method of claim 16 , wherein the control unit controls the first, second, third and fourth switch during steady state operation comprising the steps of:
setting the second voltage to the target level; and
setting a capacitor voltage across the flying capacitor to the difference between the first voltage and the target level for the second voltage minus a delta voltage.
18. The method of claim 17 , wherein
the delta voltage is 20%, 10% or less of the difference between the first voltage and the target level for the second voltage; and/or
the delta voltage is 1%, 2%, 5% or more of the difference between the first voltage and the target level for the second voltage.
19. The method of claim 16 , wherein the control unit controls the first, second, third and fourth switch during steady state operation such that a capacitor voltage across the flying capacitor in combination with the first voltage is
higher than the target level for the second voltage;
high enough to allow current from the flying capacitor to flow to the second node, when the bypass switch is at least partially closed; and/or
sufficiently low to avoid conduction of a body diode of the bypass switch.
20. The method of claim 16 , wherein the bypass switch is maintained open during steady state operation.
21. The method of claim 16 , using the control unit comprising the steps of:
detecting that the second voltage is at or below a lower voltage threshold and/or that the second current is at or above a higher current threshold; and
in reaction to this, at least partially closing the bypass switch in order to provide additional current from the flying capacitor to the second node; and/or
detecting that the second voltage is at or above a higher voltage threshold and/or that the second current is at or below a lower current threshold; and
in reaction to this, at least partially closing the bypass switch in order to divert current from the inductor towards the reference potential.
22. The method of claim 16 , wherein
the control unit transitions towards a current delivery operation state, subject to detecting a load increase; and
during the current delivery operation state the first switch is closed, the second switch is closed, the third switch is open, the fourth switch is open, and the bypass switch is at least partially closed; and/or
the control unit transitions towards a current sink operation state, subject to detecting a load decrease; and
during the current sink operation state the first switch is open, the second switch is open, the third switch is open, the fourth switch is closed and the bypass switch is at least partially closed.
23. The method of claim 22 , using the control unit comprising the step of:
maintaining the power converter in the current delivery operation state or in the current sink operation state until it is detected that the load transient at the second node has been overcome, notably until it is detected that the second voltage is at or above a lower voltage threshold and at or below a higher voltage threshold.
24. The method of claim 16 , using the control unit comprising the steps of:
detecting that the load transient at the second node has been overcome; and
in reaction to this, resuming steady state operation.
25. The method of claim 16 , using the control unit comprising the steps of:
operating the bypass switch in a linear mode with a variable on-resistance, notably in dependence of a level of the second voltage and/or in dependence of a level of a current through the bypass switch; or
operating the bypass switch in a pulse width modulation mode, with the bypass switch being either fully closed or fully open.
26. The method of claim 16 , wherein the sequence of operation states comprises
a first operation state, during which the first switch is closed, the second switch is open, the third switch is closed and the fourth switch is open; and
a second operation state, during which the first switch is open, the second switch is closed, the third switch is open and the fourth switch is closed.
27. The method of claim 26 , using the control unit comprising the step of:
adapting a duty cycle of the first and/or second operation states in order to regulate a capacitor voltage across the flying capacitor to a capacitor target level.
28. The method of claim 16 , wherein the sequence of operation states comprises
a third operation state, during which the first switch is closed, the second switch is closed, the third switch is open and the fourth switch is open; and/or
a fourth operation state, during which the first switch is open, the second switch is open, the third switch is closed and the fourth switch is closed.
29. The method of claim 28 , using the control unit comprising the step of:
adapting a duty cycle of the third and/or fourth operation states in order to regulate the second voltage or the second current to the target level.
30. The method of claim 16 , using the control unit comprising the steps of:
repeating the sequence of operation states during steady state operation at a cycle rate; and/or
determining an indication of a level of the second voltage using differential Kelvin contacts at a load which is supplied by the power converter; and/or
detecting the occurrence of a load transient at the second node based on an indication of a level of the second voltage.