Control circuit and method for controlling mode transition in a DC/DC converter

1 . A control circuit for controlling a power converter, wherein the control circuit is configured to:

operate the power converter in a pulse frequency modulation (PFM) mode using a set of activated PFM functional blocks, wherein under the PFM mode, a set of pulse width modulation (PWM) functional blocks for operating the power converter in a PWM mode is inactive; and

enter a handover state, wherein under the handover state:

the power converter is operated in the PFM mode; and

one or more PWM functional blocks of the set of PWM functional blocks are activated.

2 . The control circuit of claim 1 , wherein the control circuit is configured to enter the handover state in preparation of a transition from operating the power converter in the PFM mode to operating the power converter in the PWM mode.

3 . The control circuit of claim 1 , wherein the one or more PWM functional blocks activated in the handover state are configured to perform at least one of:

determine a deviation of an output voltage of the power converter from a target voltage; and

determine an adaptive peak current threshold being used for generating a trigger for turning on or off a power switch of the power converter.

4 . The control circuit of claim 1 , wherein the one or more PWM functional blocks activated in the handover state are configured to compare an inductor current through an inductor of the power converter with a peak current threshold for generating a trigger for turning on or off a power switch of the power converter.

5 . The control circuit of claim 1 , wherein the control circuit is configured to maintain at least one PWM functional block of the set of PWM functional blocks deactivated within the handover state.

6 . The control circuit of claim 5 , wherein the at least one PWM functional block being maintained deactivated within the handover state comprises:

one or more PWM functional blocks for generating a clock signal;

one or more PWM functional blocks for generating a ramp signal; and/or

one or more PWM functional blocks for detecting that the power converter may be put into a sleep condition.

7 . The control circuit of claim 1 , wherein the control circuit is configured to:

determine that a handover condition for entering the handover state is met; and

enter the handover state, in reaction to determining that the handover condition is met.

8 . The control circuit of claim 7 , wherein the handover condition is dependent on at least one of:

a switching frequency at which the power converter is operated within the PFM mode;

a load current which is provided at an output of the power converter; and

an input voltage and/or an output voltage of the power converter.

9 . The control circuit of claim 7 , wherein the control circuit is configured to:

determine that the handover condition is not met anymore; and

in reaction to determining that the handover condition is not met anymore:

deactivate the one or more PWM functional blocks which had been activated within the handover state; and

operate the power converter in the PFM mode, using the set of activated PFM functional blocks, while the set of PWM functional blocks for operating the PWM mode is inactive.

10 . The control circuit of claim 1 , wherein the control circuit is configured to:

compare an inductor current through an inductor of the power converter with a fixed current threshold when operating the power converter in the PFM mode to generate an OFF-trigger for turning off one or more switches of the power converter;

compare the inductor current with an adaptive current threshold when operating the power converter in the PFM mode to generate an OFF-trigger for turning off the one or more switches of the power converter; and

perform a transition from operating the power converter in the PFM mode to operating the power converter in the PWM mode in dependence of the fixed current threshold and the adaptive current threshold.

11 . The control circuit of claim 10 , wherein the control circuit is configured to:

compare the adaptive current threshold with the fixed current threshold; and

perform the transition from operating the power converter in the PFM mode to operating the power converter in the PWM mode, if the adaptive current threshold reaches or exceeds the fixed current threshold.

12 . The control circuit of claim 10 , wherein the control circuit is configured to determine the adaptive current threshold within the handover state using the one or more activated PWM functional blocks.

13 . The control circuit of claim 10 , wherein the control circuit is configured to determine the adaptive current threshold based on a deviation of an output voltage of the power converter from a target voltage.

14 . The control circuit of claim 1 , wherein the control circuit is configured to, in a transition from operating the power converter in the PFM mode to operating the power converter in the PWM mode perform at least one of:

activate the one or more PWM functional blocks from the set of PWM functional blocks that had not been activated in the handover state; and deactivate the set of activated PFM functional blocks.

15 . A power conversion system comprising:

a power converter; and

the control circuit according to claim 1 for controlling the power converter.

16 . A method for controlling a power converter; the method comprising:

operating the power converter in a pulse frequency modulation (PFM) mode using a set of activated PFM functional blocks, wherein under the PFM mode, a set of pulse width modulation (PWM) functional blocks for operating the power converter in a PWM mode is inactive; and

entering a handover state, wherein under the handover state:

the power converter is operated in the PFM mode; and

one or more PWM functional blocks of the set of PWM functional blocks are activated.

17 . The method of claim 16 , wherein the handover state is entered in preparation of a transition from operating the power converter in the PFM mode to operating the power converter in the PWM mode.