Resonant converter tuning for maintaining substantial constant phaco handpiece power under increased load
View Patent ↗A phacoemulsification system includes a phacoemulsification handpiece including a cutting tip ultrasonically vibrated by an ultrasonic transducer. A power supply is provided for driving the ultrasonic transducer at a resonant frequency of the transducer and cutting tip and varying power to the transducer, in response to loading of the cutting tip, by phase shifting voltage and current supplied to the transducer.
1. A phacoemulsification system comprising:
a phacoemulsification handpiece including a cutting tip ultrasonically vibrated by an ultrasonic transducer;
a power supply for driving said ultrasonic transducer by phase shifting voltage and current supplied to the transducer based on an amplitude command and a frequency command.
2. The system according to claim 1 wherein said power supply comprises:
a resonant output circuit connected to the ultrasonic transducer and having an output voltage and an output current oscillating therethrough;
a current sensor for providing a current signal corresponding to said output current;
a voltage sensor for providing a voltage signal corresponding to said output voltage;
a bridge driver for controlling said resonant output circuit, said bridge driver being responsive to driver signals;
control circuitry for producing the amplitude command in response to the current and voltage signals and the frequency command; and
phase shift circuitry responsive to the frequency and amplitude commands for producing the driver signals by phase shifting the output voltage of one side of the bridge driver with respect to another side of the bridge circuit.
3. The system according to claim 2 wherein said resonant output circuit is tuned to enhance open loop load response of the transducer.
4. The system according to claim 2 wherein said bridge driver provides a square wave to said resonant output circuit.
5. The system according to claim 4 wherein said bridge driver comprises a full-bridge inverter.
6. The system according to claim 5 where said resonant output current includes a step-up transformer.
7. The system according to claim 6 wherein said step-up transformer includes a primary winding connection to said bridge driver.
8. The system according to claim 7 where said step-up transformer includes a secondary winding connected to an inductor of a parallel resonant circuit in order that any transformer leakage adds to the total inductance.
9. The system according to claim 8 wherein said phase shift circuitry produces a copy of the frequency command which is shifted in phase based on the amplitude commands and inverted to produce four driver signals.
10. The system according to claim 9 wherein said copy of the frequency command is shifted between 0 and 180 degrees based on the amplitude command of 0 to 100 percent from said control circuitry.
11. The system according to claim 1 wherein system maintains a constant phase between the voltage and current supplied to the transducer.
12. The system according to claim 1 wherein system is tuned with a center frequency that is near or at an operating frequency of the phacoemulsification handpiece.
13. A phacoemulsification system comprising:
a phacoemulsification handpiece including a cutting tip ultrasonically vibrated by an ultrasonic transducer;
a power supply for driving said ultrasonic transducer at a resonant frequency of the transducer and cutting tip by phase shifting current supplied to the transducer based on an amplitude command and a frequency command.
14. A phacoemulsification system comprising:
a phacoemulsification handpiece including a cutting tip ultrasonically vibrated by an ultrasonic transducer;
a power supply for driving said ultrasonic transducer at a resonant frequency of the transducer and cutting tip by phase shifting current supplied to the transducer;
a resonant output circuit connected to the ultrasonic transducer and having an output voltage oscillating therethrough;
a voltage sensor for providing a voltage signal corresponding to said output voltage;
a bridge driver for controlling said resonant output circuit, said bridge driver being responsive to driver signals;
control circuitry for producing an amplitude command in response to the voltage signals and a frequency command; and
phase shift circuitry responsive to the frequency and amplitude commands for producing the driver signals by phase shifting the output voltage of one side of the bridge driver with respect to another side of the bridge circuit.