High power battery powered RF amplifier topology
View Patent ↗The design of high-power RF amplifiers, specifically the design of the output transformer, is complicated by the relatively low voltage provided by battery packs that are practical for handheld devices meant for possibly delicate uses. Provided is an RF amplifier with one or more taps on the primary coil, wherein each tap is controlled by a half bridge driver. The output transformer primary winding may be driven between any two half bridge drivers, with the number of turns between the half bridge drivers and the fixed output winding determining the overall turns ration for the transformer.
1. A current amplifier, comprising a transformer, the transformer comprising:
a first tap including a first half bridge driver;
a second tap including a second half bridge driver;
a third tap including a third half bridge driver;
a first portion of a primary coil located between the first tap and the second tap;
a second portion of the primary coil located between the second tap and the third tap; and
a secondary coil, wherein the first, second, and third half bridge drivers are configured to selectively turn on or turn off the first, second, and third taps, respectively,
wherein two of the first, second, and third taps are selected to drive the primary coil between the two selected taps, which allows the transformer to provide a plurality of winding ratio values,
wherein a number of coil turns of the primary coil between the two selected taps and a number of coil turns of the secondary coil determine an overall winding ratio value of the transformer, wherein the overall winding ratio value is one of the plurality of winding ratio values provided by the transformer.
2. The current amplifier of claim 1 , wherein at least one of the first, second, and third half bridge drivers comprises an upper switch element and a lower switch element, a high-side drive input connected to an input of the upper switch element, a low-side drive input connected to an input of the lower switch element, wherein the upper and lower switch elements are connected in a cascade arrangement and an output of the at least one of the first, second, and third half bridge drivers is taken from a node between the upper and lower switch elements.
3. The current amplifier of claim 2 , wherein the upper and lower switch elements comprise solid-state switching elements.
4. The current amplifier of claim 3 , wherein the solid-state switching elements comprise MOSFETs.
5. The current amplifier of claim 2 , wherein the upper and lower switch elements comprise IGBTs.
6. The current amplifier of claim 2 , wherein the upper and lower switch elements comprise mechanical relays.
7. The current amplifier of claim 1 , comprising a parallel capacitor on the secondary coil, such that an output produced by the current amplifier is a sine wave.
8. The current amplifier of claim 1 , wherein a minimum overall winding ratio value is 4:1.
9. The current amplifier of claim 1 , wherein a maximum overall winding ratio value is 15:1.
10. A medical instrument comprising:
a radio frequency (RF) generation circuit coupled to and operated by a battery and operable to generate an RF drive signal and to provide the RF drive signal to at least one electrical contact, wherein the RF generation circuit comprises:
a current amplifier, comprising a transformer, the transformer comprising:
a first tap including a first half bridge driver;
a second tap including a second half bridge driver;
a third tap including a third half bridge driver;
a first portion of a primary coil located between the first tap and the second tap;
a second portion of the primary coil located between the second tap and the third tap; and
a secondary coil, wherein the first, second, and third half bridge drivers are configured to selectively turn on or turn off the first, second, and third taps, respectively,
wherein two of the first, second, and third taps are selected to drive the primary coil between the two selected taps, which allows the transformer to provide a plurality of winding ratio values,
wherein a number of coil turns of the primary coil between the two selected taps and a number of coil turns of the secondary coil determine an overall winding ratio value of the transformer, wherein the overall winding ratio value is one of the plurality of winding ratio values provided by the transformer.
11. The medical instrument of claim 10 , wherein at least one of the first, second, and third half bridge drivers comprises an upper switch element and a lower switch element, a high-side drive input connected to an input of the upper switch element, a low-side drive input connected to an input of the lower switch element, wherein the upper and lower switch elements are connected in a cascade arrangement and an output of the at least one of the first, second, and third half bridge drivers is taken from a node between the upper and lower switch elements.
12. The medical instrument of claim 11 , wherein the upper and lower switch elements comprise solid-state switching elements.
13. The medical instrument of claim 12 , wherein the solid-state switching elements comprise MOSFETs.
14. The medical instrument of claim 11 , wherein the upper and lower switch elements comprise IGBTs.
15. The medical instrument of claim 11 , wherein the upper and lower switch elements comprise mechanical relays.
16. The medical instrument of claim 10 , comprising a parallel capacitor on the secondary coil, such that an output produced by the current amplifier is a sine wave.
17. The medical instrument of claim 10 , wherein a minimum overall winding ratio value is 4:1.
18. The medical instrument of claim 10 , wherein a maximum overall winding ratio value is 15:1.
19. A current amplifier, comprising:
a transformer comprising:
a first tap including a first half bridge driver;
a second tap including a second half bridge driver;
a third tap including a third half bridge driver;
a first portion of a primary coil located between the first tap and the second tap;
a second portion of the primary coil located between the second tap and the third tap; and
a secondary coil, wherein the first, second, and third half bridge drivers are configured to selectively turn on or turn off the first, second, and third taps, respectively,
wherein two of the first, second, and third taps are selected to drive the primary coil between the two selected taps, which allows the transformer to provide a plurality of winding ratio values,
wherein a number of coil turns of the primary coil between the two selected taps and a number of coil turns of the secondary coil determine an overall winding ratio value of the transformer, wherein the overall winding ratio value is one of the plurality of winding ratio values provided by the transformer,
wherein at least one of the first, second, and third half bridge drivers comprises an upper switch element and a lower switch element, a high-side drive input connected to an input of the upper switch element, a low-side drive input connected to an input of the lower switch element, wherein the upper and lower switch elements are connected in a cascade arrangement and an output of the at least one of the first, second, and third half bridge drivers is taken from a node between the upper and lower switch elements; and
a parallel capacitor on the secondary coil, such that an output produced by the current amplifier is a sine wave;
wherein a minimum overall winding ratio value is 4:1; and
wherein a maximum overall winding ratio value is 15:1.
20. The current amplifier of claim 19 , wherein the upper and lower switch elements comprise solid-state switching elements.