Converter

1. A converter comprising:

a bridge circuit having a first leg and a second leg, each leg including a high switch and a low switch, the high switches being connected to a first energy source and the low switches being connected to ground;

a coupling network(s) having a first connection between the switches of the first leg and a second connection between the switches of the second leg; and

a second (or multiple secondary) energy source(s) connected between the coupling network(s) and ground, wherein

the coupling network comprises a first inductive element connected between the second energy source and the switches of the first leg, and a second inductive element connected between the second energy source and the switches of the second leg.

2. The converter of claim 1 , wherein a third energy source is connected in parallel with the coupling network.

3. The converter of claim 2 , wherein the converter is controlled to transfer energy between the second and third energy source to manage efficiency and power transfer of the converter.

4. The converter of claim 2 , wherein the third energy source is an AC energy source, and is the only AC energy source of the converter.

5. A converter comprising:

a bridge circuit having a first leg and a second leg, each leg including a high switch and a low switch, the high switches being connected to a first energy source and the low switches being connected to ground;

a coupling network(s) having a first connection between the switches of the first leg and a second connection between the switches of the second leg; and

a second (or multiple secondary) energy source(s) connected between the coupling network(s) and ground, wherein:

the converter is a boost active bridge converter that includes a capacitor, the capacitor being the first energy source; and

the converter includes a DC energy source having a positive terminal electrically located between the first leg and the second leg, wherein the DC energy source is the second energy source.

6. The converter of claim 5 , wherein the coupling network comprises one or more inductors or capacitors arranged to interface the second or third energy source effectively with the first and second legs.

7. The converter of claim 5 , further comprising a control circuit to control the switches of the converter.

8. The converter of claim 7 , wherein the control circuit is also configured to control the duty cycle and/or phase of the switches.

9. The converter of claim 8 , wherein the control of the duty cycle of the switches can control two output variables of the converter.

10. The converter of claim 7 , wherein the control circuit includes one or more input control variables as inputs for controlling the switches.

11. The converter of claim 7 , wherein the control circuit is configured to control energy transfer between each energy source(s) to optimise the efficiency and power transfer of the converter.

12. The converter of claim 5 , wherein the converter is configured for bi-directional power transfer.

13. The converter of claim 5 , wherein:

the converter is part of an IPT system, wherein the IPT system includes an IPT primary circuit and an IPT secondary circuit, and wherein the converter is part of the IPT secondary circuit.

14. The converter of claim 5 , wherein the coupling network receives direct current from the first leg and the second leg, and wherein input into the bridge circuit is alternating current, and wherein output of the bridge circuit is direct current.

15. The converter of claim 5 , wherein the converter charges the DC energy source.

16. The converter of claim 15 , wherein the converter is an AC-AC converter.

17. The converter of claim 5 , wherein the converter is configured for bi-directional power transfer.

18. The converter of claim 5 , wherein the converter includes the capacitor and a second capacitor, the first leg being electrically connected to the capacitor, and the second leg being electrically connected to the second capacitor.

19. A converter comprising:

a bridge circuit having a first leg and a second leg, each leg including a high switch and a low switch, the high switches being connected to a first energy source and the low switches being connected to ground;

a coupling network(s) having a first connection between the switches of the first leg and a second connection between the switches of the second leg; and

a second (or multiple secondary) energy source(s) connected between the coupling network(s) and ground, wherein

the converter is controlled so that there is a difference in DC voltage on the first leg relative to the second leg, wherein the first leg in combination with the second leg converts AC power to DC power or visa-versa.

20. The converter of claim 19 , wherein the first energy source comprises a capacitive member.

21. The converter of claim 19 , wherein a separate energy source is connected between each high switch and ground.

22. The converter of claim 19 , wherein:

the converter includes only one bridge circuit, the bridge circuit being the only one bridge circuit; and

the first energy source is, in totality, a capacitor.

23. The converter of claim 19 , wherein the converter is part of an LCL tuned system.

24. The converter of claim 19 , wherein:

wherein the first leg in combination with the second leg converts AC power to DC power.

25. The converter of claim 19 , wherein:

wherein the first leg in combination with the second leg converts DC power to AC power.