Over-current recovery including overshoot suppression

1. A method of operating a power converter circuit, comprising:

monitoring a load current;

operating the power converter circuit in a constant-current mode when the monitored output current exceeds a specified over-current threshold;

comparing a value representing an output voltage of the power converter circuit to a soft-start voltage reference value offset by a specified threshold; and

in response, when the soft-start reference voltage exceeds the value representing the output voltage of the power converter by the specified threshold, forcing the soft-start voltage reference value to the value representing the output voltage of the power converter plus a specified offset, using a buffer circuit; and

regulating the output voltage of the power converter using the soft-start voltage reference value as a target voltage including ramping the soft-start voltage reference value.

2. The method of claim 1 , wherein the ramping the soft-start voltage reference value includes injecting a constant current into a soft-start capacitor until the soft-start capacitor is charged to a specified reference voltage.

3. The method of claim 1 , wherein forcing the soft-start voltage reference value

comprises triggering a switching element to couple the buffer circuit between a soft-start voltage reference node and a node carrying a representation of the output voltage of the power converter plus the specified offset.

4. The method of claim 1 , wherein the value representing the output voltage of the power converter comprises a specified proportion of the output voltage.

5. The method of claim 1 , wherein the soft-start voltage reference value is maintained at a value greater in magnitude than the value representing the output voltage of the power converter.

6. The method of claim 1 , comprising operating the power converter circuit in a voltage-regulating mode when the output current is below a specified over-current threshold.

7. The method of claim 1 , comprising suppressing overshoot of the output voltage beyond the specified regulated output voltage value including limiting the output voltage slew rate to a rate defined by the ramping of the soft-start voltage reference value.

8. A power supply control circuit, comprising:

a target voltage generator circuit, the target voltage generator configured to generate a soft-start voltage reference value including ramping the soft-start voltage reference value; and

a current limiter circuit configured to trigger operation of a converter circuit in a constant-current mode in response to an over-current indication;

wherein, in the constant-current mode, the target voltage generator circuit is configured to:

compare a value representing an output voltage of the power converter circuit to a soft-start voltage reference value offset by a specified threshold; and

in response, when the soft-start reference voltage exceeds the value representing the output voltage of the power converter by the specified threshold, set the soft-start voltage reference value to the value representing the output voltage of the power converter plus a specified offset, using a buffer circuit configured to force a soft-start voltage reference node to the value representing the output voltage plus the specified offset.

9. The power supply control circuit of claim 8 , comprising a constant current source and a soft-start capacitor; and

wherein the target voltage generator circuit is configured to ramp the soft-start voltage reference value by injecting a constant current from the constant current source into the soft-start capacitor until the soft-start capacitor is charged to a specified reference voltage.

10. The power supply control circuit of claim 8 , wherein the target voltage generator comprises:

a first comparator configured to compare the value representing the output voltage of the power converter to the soft-start voltage reference value offset by the specified threshold;

and

a switch coupled to the output of the first comparator and configured to force the soft-start voltage reference node to the value representing the output voltage plus the specified offset, using the buffer circuit.

11. The power supply control circuit of claim 8 , wherein the value representing the output voltage of the power converter comprises a specified proportion of the output voltage.

12. The power supply control circuit of claim 8 , wherein the soft-start voltage reference value is maintained at a value greater in magnitude than the value representing the output voltage of the power converter.

13. A DC-to-DC power supply circuit, comprising:

a converter circuit having an input node and an output node, the output node coupleable to an output capacitor;

a current limiter circuit configured to trigger operation of the converter circuit in a constant-current mode in response to an over-current indication;

a target voltage generator circuit, the target voltage generator configured to generate a soft-start voltage reference value including ramping the soft-start voltage reference value;

an error amplifier coupled to the target voltage generator and configured to receive the soft-start voltage reference value and to provide an error signal to the converter circuit in response to comparing the soft-start voltage reference value to a value representing an output voltage of the power converter, the converter circuit configured to provide a regulated output voltage at the output node in response to the error signal; and

wherein the target voltage generator circuit is configured to:

compare a value representing an output voltage of the power converter circuit to a soft-start voltage reference value offset by a specified threshold; and

in response, when the soft-start reference voltage exceeds the value representing the output voltage of the power converter by the specified threshold, set the soft-start voltage reference value to the value representing the output voltage of the power converter plus a specified offset, using a buffer circuit configured to force a soft-start voltage reference node to the value representing the output voltage plus the specified offset.

14. The DC-to-DC power supply circuit of claim 13 , wherein the power converter circuit is configured to operate in a voltage-regulating mode when the output current is below a specified over-current threshold.

15. The DC-to-DC power supply circuit of claim 13 , comprising a constant current source and a soft-start capacitor; and

wherein the target voltage generator circuit is configured to ramp the soft-start voltage reference value by injecting a constant current from the constant current source into the soft-start capacitor until the soft-start capacitor is charged to a specified reference voltage.

16. The DC-to-DC power supply circuit of claim 13 , further comprising the output capacitor coupled to the output node.

17. The DC-to-DC power supply circuit of claim 13 , wherein the target voltage generator comprises:

a first comparator configured to compare the value representing the output voltage of the power converter to the soft-start voltage reference value offset by the specified threshold;

and

a switch coupled to the output of the first comparator and configured to force the soft-start voltage reference node to the value representing the output voltage plus the specified offset, using the buffer circuit.

18. The method of claim 1 , comprising inhibiting the forcing of the soft-start voltage reference value to the value representing the output voltage of the power converter plus a specified offset when the output current is below a specified over-current threshold.

19. The power supply control circuit of claim 8 , wherein the target voltage generator circuit is inhibited from forcing of the soft-start voltage reference value to the value representing the output voltage of the power converter plus a specified offset when the output current is below a specified over-current threshold.

20. The DC-to-DC power supply circuit of claim 13 , wherein the target voltage generator circuit is inhibited from forcing of the soft-start voltage reference value to the value representing the output voltage of the power converter plus a specified offset when the output current is below a specified over-current threshold.