Switching methods and apparatus

1. An ablation element power switching apparatus comprising:

a plurality of first switches having an input end to receive a power input signal, each first switch having an output end;

a plurality of second switches, each second switch having an input end coupled to the output end of at least one first switch, each second switch having an output end;

a bypass switch having an input end to receive the power input signal and an output end coupled to the second switches,

wherein in an on position, the bypass switch bypasses the first switches to transmit the power input signal to the second switches;

a plurality of power receiving members, each power receiving member having an input end coupled to the output end of at least one second switch; and

a controller selectively turning on the first switches one at a time in a cyclical manner according to a first switching rate to transmit the power input signal, the controller selectively turning on the second switches one subset of the second switches at a time according to a second switch rate to transmit the power input signal from the first switches to a subset of power receiving members one power receiving member at a time within the subset of power receiving members according to the first switching rate,

wherein the first switching rate is substantially faster than the second switching rate, and

further wherein each fist switch is configured to transmit the power input signal independendent of the switching position of the other of the plurality of first switches.

2. The power switching apparatus of claim 1 , wherein the first switching rate is faster than the second switching rate by at least one order of magnitude.

3. The power switching apparatus of claim 1 , wherein each subset of the second switches are equal in number to the first switches and equal in number to each subset of the power receiving members.

4. The power switching apparatus of claim 1 , wherein the first switches are solid state switches.

5. The power switching apparatus of claim 1 , wherein the second switches are electromechanical relays.

6. The power switching apparatus of claim 1 , wherein the power receiving members are arranged in a closed loop, and wherein each subset of the power receiving members form a group of neighboring power receiving members within a portion of the closed loop.

7. The power switching apparatus of claim 1 , wherein the first switching rate is such that for each first switching cycle, a first switching period is at most about 0.1 seconds and the first switches are each turned on once for about the same duty cycle over the first switching period.

8. The power switching apparatus of claim 1 , comprising three first switches.

9. The power switching apparatus of claim 1 , comprising N power receiving members, M first switches, and at most M×N second switches.

10. The power switching apparatus of claim 1 , comprising N power receiving members, M first switches, and at most M+N second switches.

11. The power switching apparatus of claim 1 , wherein when the bypass switch is in the on position, the controller selectively turns on the second switches to transmit the power input signal to the power receiving members one at a time in a cyclical manner.

12. A power switching apparatus comprising:

a plurality of first switches having an input end to receive a power input signal, each first switch having an output end;

a plurality of second switches, each second switch having an input end coupled to the ouput end of at least one first switch, each second switch having an output end;

a bypass switch having an input end coupled to the power input signal and An output end coupled to the second switches,

wherein in an on position, the bypass switch bypasses the first switches to Transmit the power input signal to the second switches;

a plurality of ablation members, each ablation member having an input end coupled to the output end of at least one second switch; and

a controller selectively turning on the first switches one at a time in a cyclical manner according to a first switching rate to transmit the power input signal, the controller selectively turning on the second switches one subset of the second switches at a time according to a second switch rate to transmit the power input signal from the first switches to a subset of ablation members one ablation member at a time within the subset of ablation members according to the first switching rate,

wherein the first switching rate is such that for each first switching cycle, a first switching period is at most about T seconds during which each first switch is turned on once, and that a rate of tissue ablation of the tissue to be ablated by each ablation member remains substantially constant during the first switching period,

further wherein each first switch is configured to transmit the power input signal independent of the switching position of the other of the plurality of first switches.

13. The power switching apparatus of claim 12 , wherein the first switching rate is such that the rate of tissue ablation of the tissue to be ablated by each ablation member changes at most by about 5% during the first switching period.

14. The power switching apparatus of claim 12 , wherein the first switching period is at most about 0.1 seconds.

15. The power switching apparatus of claim 12 , wherein each subset of the second switches are equal in number to the first switches and equal in number to each subset of the ablation members.

16. The power switching apparatus of claim 12 , wherein for each first switching cycle, each first switch is turned on once for about the same duty cycle over the first switching period.

17. The power switching apparatus of claim 12 , wherein the first switches are solid state switches.

18. The power switching apparatus of claim 12 , wherein the ablation members are arranged in a closed loop, and wherein each subset of the ablation members form a group of neighboring ablation members within a portion of the closed loop.