Control and inverter design topologies for electronic medical devices
Examples described herein may include medical devices and electrosurgical generators with resonant isolated transformers to perform filtering and gain functions. An example electrosurgical generator includes a radio frequency (RF) inverter stage configured to receive an input signal and, in response to control feedback signals, to provide an output signal that provides power to a load. The RF inverter stage includes a resonant isolated transformer configured to receive the input signal and to provide gain and filtering adjustments to the input signal to provide the output signal.
1. An electrosurgical generator, comprising: a radio frequency (RF) inverter stage configured to receive a power signal and, in response to control signals, to provide an output signal based on the power signal, wherein the RF inverter stage comprises a resonant isolated transformer circuit configured to receive the power signal and to provide gain and filtering adjustments to the power signal to provide the output signal, wherein the resonant isolated transformer circuit has only one magnetic component, the only one magnetic component being a transformer, wherein the resonant isolated transformer circuit provides multi-stage filtering via the only one magnetic component.
2. The electrosurgical generator of claim 1 , wherein the transformer is a loosely coupled transformer having a coupling coefficient less than 1.
3. The electrosurgical generator of claim 2 , wherein the coupling coefficient of the loosely coupled transformer less than 0.6.
4. The electrosurgical generator of claim 2 , wherein the power signal is an alternating current power signal, wherein the coupling coefficient and inductance values of the loosely coupled transformer are based on direct current signals and harmonics to be filtered from the alternating current power signal.
5. The electrosurgical generator of claim 2 , wherein the loosely coupled transformer has a turns ratio of 1:N.
6. The electrosurgical generator of claim 5 , wherein the turns ratio of the loosely coupled transformer is 1:1.
7. The electrosurgical generator of claim 1 , wherein the resonant isolated transformer circuit has series or parallel capacitance on a primary side and on a secondary side.
8. The electrosurgical generator of claim 1 , wherein the resonant isolated transformer circuit can provide at least one of a resistive, a conductive, a transresistive, or a transconductive gain.
9. The electrosurgical generator of claim 8 , wherein the resonant isolated transformer circuit provides load independent gain.
10. The electrosurgical generator of claim 1 , wherein the power signal is an alternating current power signal, wherein the multi-stage filtering includes circuitry configured to filter direct current signals and harmonics from the alternating current power signal.
11. The electrosurgical generator of claim 1 , wherein the resonant isolated transformer circuit is configured to operate in a frequency range between and including 100 kHz and 30 MHz.
12. The electrosurgical generator of claim 1 wherein: the power signal is received without a buck or boost convertor; the transformer has a coupling coefficient less than 1 and a leakage inductance; and the resonant isolated transformer circuit further comprises a plurality of capacitors electrically coupled to the transformer that provide the multi-stage filtering without an additional magnetic component.
13. A method, comprising: receiving an input signal at a resonant stage of a medical device, wherein the resonant stage has only one magnetic component, the only one magnetic component being a resonant isolated transformer; multi-stage filtering, only via the resonant isolated transformer of the resonant stage, the input signal to provide an output signal, and providing the output signal at an output of the medical device.
14. The method of claim 13 , further comprising setting a coupling coefficient and inductances of the resonant isolated transformer based on desired filtering of the input signal.
15. The method of claim 13 , further comprising setting a coupling coefficient and inductances of the resonant isolated transformer based on desired gain of the input signal.
16. The method of claim 15 wherein the desired gain of the input signal is one of resistive, conductive, transresistive, or transconductive gain, and wherein the desired gain is load independent.
17. The method of claim 13 , further comprising setting a coupling coefficient of the resonant isolated transformer to a value less than 0.6.
18. The method of claim 13 , where the input signal is a voltage signal.
19. The method of claim 13 , where the input signal is a current signal.
20. The method of claim 13 , further comprising: providing a current-based signal as the output signal for a first therapy type; and providing a voltage-based signal as the output signal for a second therapy type.
21. The method of claim 13 wherein: the power signal is received without a buck or boost convertor; the resonant isolated transformer has a coupling coefficient less than 1 and a leakage inductance; and the resonant stage further comprises a plurality of capacitors electrically coupled to the resonant isolated transformer such that the multistage filtering is performed without using an additional magnetic component beyond the resonant isolated transformer.
22. An electrosurgical generator, comprising: a radio frequency (RF) inverter stage configured to receive a power signal and, in response to control signals to provide an output signal based on the power signal, wherein the RF inverter stage comprises a resonant isolated transformer circuit configured to receive the power signal and to provide gain and filtering adjustments to the power signal to provide the output signal, wherein the resonant isolated transformer circuit has only one magnetic component, the only one magnetic component being a transformer, wherein the resonant isolated transformer circuit provides multi-stage filtering via the only one magnetic component; the RF inverter stage having a resonant frequency; and a controller coupled to the RF inverter stage and configured to provide the control signals to the RF inverter stage to control the gain and filtering adjustments to the power signal received at the RF inverter stage based on a selected therapy, wherein the controller is configured to drive the RF inverter stage using subharmonic frequencies of the RF inverter stage resonant frequency to control the gain and filtering adjustments to the power signal.
23. The electrosurgical generator of claim 22 , wherein the controller further uses duty cycle modulation to control the gain and filtering adjustments to the power signal.
24. The electrosurgical generator of claim 22 , wherein the controller comprises a microprocessor and a pulse-width modulation controller.