Bidirectional resonant direct current-direct current conversion circuit and uninterruptible power supply

1. A bidirectional resonant direct current-direct current conversion circuit, comprising:

a full-bridge conversion module;

a transformer; and

a half-bridge conversion module, wherein

the full-bridge conversion module is coupled to the half-bridge conversion module via the transformer;

the full-bridge conversion module is configured to convert two-level direct current power into alternating current power, and the half-bridge conversion module is configured to convert the alternating current power outputted by the full-bridge conversion module into three-level direct current power; and

the half-bridge conversion module is further configured to convert three-level direct current power into alternating current power, and the full-bridge conversion module is further configured to convert the alternating current power outputted by the half-bridge conversion module into two-level direct current power.

2. The bidirectional resonant direct current-direct current conversion circuit according to claim 1 , wherein the half-bridge conversion module comprises:

a first switch;

a second switch;

a first bus capacitor;

a second bus capacitor; and

a first resonant capacitor, wherein

the first switch and the second switch are connected in series with each other to form a first branch;

the first bus capacitor and the second bus capacitor are connected in series with each other to form a second branch;

the first branch and the second branch are connected in parallel with each other to form a third branch, one terminal of the third branch is a first three-level direct current side electrode terminal, and the other terminal of the third branch is a second three-level direct current side electrode terminal;

a connection point between the first switch and the second switch is connected to one terminal of the first resonant capacitor, and the other terminal of the first resonant capacitor is a first transformer side terminal of the half-bridge conversion module; and

a connection point between the first bus capacitor and the second bus capacitor is a three-level direct current side neutral terminal and a second transformer side terminal of the half-bridge conversion module.

3. The bidirectional resonant direct current-direct current conversion circuit according to claim 2 , wherein

in a first phase of a process that a power flow is transmitted from two-level direct current side to the three-level direct current side, the first switch is turned on, and the second switch is turned off, wherein a first terminal of a secondary winding of the transformer, the first resonant capacitor, the first switch, the first bus capacitor, and a second terminal of the secondary winding of the transformer form a freewheeling loop, and the first bus capacitor is charged;

in a second phase of the process that the power flow is transmitted from the two-level direct current side to the three-level direct current side, the first switch is turned off, and the second switch is turned on, wherein the second terminal of the secondary winding of the transformer, the second bus capacitor, the second switch, the first resonant capacitor, and the first terminal of the secondary winding of the transformer form a freewheeling loop, and the second bus capacitor is charged;

in a first phase of a process that the power flow is transmitted from the three-level direct current side to the two-level direct current side, the first switch is turned on, and the second switch is turned off, wherein the first switch, the first resonant capacitor, and the secondary winding of the transformer form a resonance loop, and the first bus capacitor is discharged; and

in a second phase of the process that the power flow is transmitted from the three-level direct current side to the two-level direct current side, the first switch is turned off, and the second switch is turned on, wherein the secondary winding of the transformer, the first resonant capacitor, and the second switch form a resonance loop, and the second bus capacitor is discharged.

4. The bidirectional resonant direct current-direct current conversion circuit according to claim 2 , further comprising:

a first resonant inductor, wherein the first resonant inductor and the secondary winding of the transformer are connected in series with each other to form a four branch.

5. The bidirectional resonant direct current-direct current conversion circuit according to claim 2 , wherein the full-bridge conversion module comprises:

a third switch;

a fourth switch;

a fifth switch; and

a sixth switch, wherein

the third switch and the fourth switch are connected in series with each other to form a fifth branch;

the fifth switch and the sixth switch are connected in series with each other to form a sixth branch;

the fifth branch and the sixth branch are connected in parallel with each other to form a seventh branch, one terminal of the seventh branch is a first two-level direct current side electrode terminal, and the other terminal of the seventh branch is a second two-level direct current side electrode terminal; and

a connection point between the third switch and the fourth switch is a first transformer side terminal of the full-bridge conversion module, and a connection point between the fifth switch and the sixth switch is a second transformer side terminal of the full-bridge conversion module.

6. The bidirectional resonant direct current-direct current conversion circuit according to claim 3 , wherein the full-bridge conversion module comprises:

a third switch;

a fourth switch;

a fifth switch; and

a sixth switch, wherein

the third switch and the fourth switch are connected in series with each other to form a fifth branch;

the fifth switch and the sixth switch are connected in series with each other to form a sixth branch;

the fifth branch and the sixth branch are connected in parallel with each other to form a seventh branch, one terminal of the seventh branch is a first two-level direct current side electrode terminal, and the other terminal of the seventh branch is a second two-level direct current side electrode terminal; and

a connection point between the third switch and the fourth switch is a first transformer side terminal of the full-bridge conversion module, and a connection point between the fifth switch and the sixth switch is a second transformer side terminal of the full-bridge conversion module.

7. The bidirectional resonant direct current-direct current conversion circuit according to claim 4 , wherein the full-bridge conversion module comprises:

a third switch;

a fourth switch;

a fifth switch; and

a sixth switch, wherein

the third switch and the fourth switch are connected in series with each other to form a fifth branch;

the fifth switch and the sixth switch are connected in series with each other to form a sixth branch;

the fifth branch and the sixth branch are connected in parallel with each other to form a seventh branch, one terminal of the seventh branch is a first two-level direct current side electrode terminal, and the other terminal of the seventh branch is a second two-level direct current side electrode terminal; and

a connection point between the third switch and the fourth switch is a first transformer side terminal of the full-bridge conversion module, and a connection point between the fifth switch and the sixth switch is a second transformer side terminal of the full-bridge conversion module.

8. The bidirectional resonant direct current-direct current conversion circuit according to claim 5 , further comprising:

a second resonant capacitor, wherein the second resonant capacitor and a primary winding of the transformer are connected in series with each other to form an eighth branch, and the eighth branch is connected between the first transformer side terminal and the second transformer side terminal of the full-bridge conversion module.

9. The bidirectional resonant direct current-direct current conversion circuit according to claim 6 , further comprising:

a second resonant capacitor, wherein the second resonant capacitor and a primary winding of the transformer are connected in series with each other to form an eighth branch, and the eighth branch is connected between the first transformer side terminal and the second transformer side terminal of the full-bridge conversion module.

10. The bidirectional resonant direct current-direct current conversion circuit according to claim 7 , further comprising:

a second resonant capacitor, wherein the second resonant capacitor and a primary winding of the transformer are connected in series with each other to form an eighth branch, and the eighth branch is connected between the first transformer side terminal and the second transformer side terminal of the full-bridge conversion module.

11. The bidirectional resonant direct current-direct current conversion circuit according to claim 5 , further comprising:

a second resonant inductor, wherein the second resonant inductor and a primary winding of the transformer are connected in series with each other to form an eighth branch, and the eighth branch is connected between the first transformer side terminal and the second transformer side terminal of the full-bridge conversion module.

12. The bidirectional resonant direct current-direct current conversion circuit according to claim 6 , further comprising:

a second resonant inductor, wherein the second resonant inductor and a primary winding of the transformer are connected in series with each other to form an eighth branch, and the eighth branch is connected between the first transformer side terminal and the second transformer side terminal of the full-bridge conversion module.

13. The bidirectional resonant direct current-direct current conversion circuit according to claim 7 , further comprising:

a second resonant inductor, wherein the second resonant inductor and a primary winding of the transformer are connected in series with each other to form an eighth branch, and the eighth branch is connected between the first transformer side terminal and the second transformer side terminal of the full-bridge conversion module.

14. The bidirectional resonant direct current-direct current conversion circuit according to claim 5 , further comprising:

a second resonant capacitor and a second resonant inductor, wherein the second resonant capacitor, the second resonant inductor, and a primary winding of the transformer are connected in series with each other to form an eighth branch, and the eighth branch is connected between the first transformer side terminal and the second transformer side terminal of the full-bridge conversion module.

15. The bidirectional resonant direct current-direct current conversion circuit according to claim 6 , further comprising:

a second resonant capacitor and a second resonant inductor, wherein the second resonant capacitor, the second resonant inductor, and a primary winding of the transformer are connected in series with each other to form an eighth branch, and the eighth branch is connected between the first transformer side terminal and the second transformer side terminal of the full-bridge conversion module.

16. The bidirectional resonant direct current-direct current conversion circuit according to claim 7 , further comprising:

a second resonant capacitor and a second resonant inductor, wherein the second resonant capacitor, the second resonant inductor, and a primary winding of the transformer are connected in series with each other to form an eighth branch, and the eighth branch is connected between the first transformer side terminal and the second transformer side terminal of the full-bridge conversion module.

17. The bidirectional resonant direct current-direct current conversion circuit according to claim 1 , wherein a secondary winding of the transformer is a single winding.

18. An uninterruptible power supply, comprising the bidirectional resonant direct current-direct current conversion circuit according to claim 1 .