Power converter modulation sequence

1. A power converter comprising:

a transformer comprising:

a primary winding coupled to a primary side of the power converter; and

a secondary winding coupled to a secondary side of the power converter;

a switching bridge circuit on the primary side and comprising:

a voltage input configured to receive a first voltage; and

a plurality of switches coupled in a full-bridge arrangement, each switch controllable into a conduction mode and into a non-conduction mode;

a resonant tank circuit on the primary side and coupled to the switching bridge circuit;

an output rectifier coupled to the secondary winding and comprising a voltage output configured to output a second voltage; and

a controller configured to:

control the plurality of switches based on a series of phase shift modulation switching cycles, each cycle comprising a control period and a delay period;

wherein, during the control period, the controller is configured to cause the conduction mode of each switch of the plurality of switches to overlap a portion of each conduction mode of two other switches of the plurality of switches, wherein the conduction modes of the two other switches do not overlap in time; and

wherein, during the delay period, the controller is configured to control all of the switches into non-conduction modes overlapping in time.

2. The power converter of claim 1 , wherein the control period begins in response to controlling one of the switches into the conduction mode and ends in response to each switch being simultaneously controlled into the non-conduction mode.

3. The power converter of claim 1 , wherein the series of phase shift modulation switching cycles comprises a first cycle and a second cycle; and

wherein the controller is further configured to:

execute the control period of the first cycle;

execute the delay period of the first cycle after the control period of the first cycle; and

execute the control period of the second cycle after the delay period of the first cycle.

4. The power converter of claim 3 , wherein the controller is further configured to base an execution time of the delay period on a desired value of the second voltage.

5. The power converter of claim 4 , wherein, in response to the execution time of the delay period being set to a first duration, the power converter is configured to output the second voltage at a first value; and

wherein, in response to the execution time of the delay period being set to a second duration longer than the first duration, the power converter is configured to output the second voltage at a second value less than the first value.

6. The power converter of claim 1 , wherein the resonant tank circuit comprises:

a resonant tank inductor; and

a resonant tank capacitor;

wherein the resonant tank inductor, the resonant tank capacitor, and the primary winding of the transformer are coupled in series.

7. The power converter of claim 6 , wherein the plurality of switches comprises a first switch, a second switch, a third switch, and a fourth switch;

wherein, during the control period, the controller is further configured to:

control each of the first, second, and third switches into a single conduction mode period and into at least one non-conduction mode period; and

control the fourth switch into a pair of conduction mode periods and into at least one non-conduction mode period.

8. The power converter of claim 7 , wherein, during the control period, the controller is further configured to set a duration of the single conduction mode period of each of the first, second, and third switches equal to a resonant frequency of the resonant tank circuit in response to the second voltage being greater than twenty percent of the first voltage.

9. The power converter of claim 7 , wherein, during the control period, the controller is further configured to set a duration of the single conduction mode period of each of the first, second, and third switches less than a resonant frequency of the resonant tank circuit in response to the second voltage being less than twenty percent of the first voltage.

10. The power converter of claim 7 , wherein the first and second switches form a first leading leg;

wherein the third and fourth switches form a lagging leg; and

wherein the second and third switches are high-side switches.

11. A method of operating a power converter including a transformer including a primary winding on a primary side of the transformer and a secondary winding on a secondary side of the transformer, a switching bridge, a resonant tank, an output rectifier, and a plurality of switches coupled between the switching bridge and the resonant tank, the method comprising:

operating each switch of the plurality of switches during a period of switch conduction of a phase shift modulation sequence into at least one conduction mode duration and into at least one non-conduction mode duration; and

operating each switch of the plurality of switches during a period of switch non-conduction of the phase shift modulation sequence into overlapping non-conduction mode durations;

wherein the at least one conduction mode duration of each switch of the plurality of switches overlaps a portion of the at least one conduction mode duration of two switches of the plurality of switches.

12. The method of claim 11 , further comprising:

operating the plurality of switches based on a series of switching cycles, each switching cycle comprising the phase shift modulation sequence; and

adjusting an operating frequency of the power converter based on a duration of the period of switch non-conduction between consecutive switching cycles.

13. The method of claim 12 , wherein adjusting the operating frequency comprises shortening the duration of the period of switch non-conduction to increase the operating frequency of the power converter.

14. The method of claim 12 , wherein adjusting the operating frequency comprises shortening the duration of the period of switch non-conduction to increase a power output of the power converter.

15. The method of claim 12 , wherein adjusting the operating frequency comprises lengthening the duration of the period of switch non-conduction to decrease the operating frequency of the power converter.

16. The method of claim 12 , wherein adjusting the operating frequency comprises lengthening the duration of the period of switch non-conduction to decrease the power output of the power converter.

17. The method of claim 11 , wherein the plurality of switches comprises four switches coupled in a full-bridge arrangement; and

wherein, during the period of switch conduction, no more than three switches of the four switches are simultaneously controlled into the non-conduction mode.

18. The method of claim 17 , wherein the full-bridge arrangement comprises:

a first high-side switch in a leading leg;

a first low-side switch in the leading leg;

a second high-side switch in a lagging leg; and

a second low-side switch in the lagging leg;

wherein the at least one conduction mode duration of the first high-side switch overlaps the portion of the at least one conduction mode duration of the second high-side switch and overlaps the portion of the at least one conduction mode duration of the second low-side switch.

19. The method of claim 18 , wherein the at least one conduction mode duration of the first high-side switch does not overlap any portion of the at least one conduction mode duration of the first low-side switch.

20. The method of claim 18 further comprising

setting a duration of the at least one conduction mode duration of each of the first high-side switch, the first low-side switch, and the second high-side switch equal to a resonant frequency of the resonant tank; and

setting a duration of a first conduction mode duration of the at least one conduction mode duration of the second low-side switch equal to half of the resonant frequency.