Quasi-resonant plasma voltage generator
Traditional plasma voltage generator circuits consist mainly of fly-back or pulse forming networks. These systems tend supply plasma generating pulses to plasma reactors at frequencies less than 30 kHz with most being less than 5 kHz. In addition these traditional plasma voltage generators are limited in the ability to adjust to dynamic reactor conditions, are energy inefficient and are limited in the amount of material ionized. An innovative drive system is presented herein that is energy efficient, can operate at frequencies below and well above 30 kHz, and can react to dynamic conditions in the plasma reactor allowing much greater flexibility and enhanced operating capabilities.
1. A method of generating a plasma voltage sufficient to initiate and sustain a plasma in a plasma reactor consisting of the steps of:
providing an electrical power source;
providing a transformer consisting of at least one primary winding and one secondary winding;
connecting said transformer primary winding to said electrical power source;
providing a polarity sensitive device including a blocking diode;
connecting said polarity sensitive device in series with the transformer secondary winding;
providing a switch connected in series with the transformer secondary winding and the polarity sensitive device;
detecting a rising voltage in the transformer secondary winding with a phase detector;
providing a zero cross detection circuit and connecting said zero cross detection circuit to said switch; and
opening and closing said switch in response to a zero cross condition detected by said zero cross detection circuit.
2. The method of claim 1 , which includes the additional steps of:
providing a switch driver connected to said switch;
providing a duty cycle controller connected to said switch driver; and
said duty cycle controller signaling said switch driver and controlling cycles with said switch in a respective open and closed conditions.
3. The method in claim 1 , which includes the additional steps of: providing an impedance matching network and connecting said impedance matching network with the plasma reactor.
4. The method of claim 1 , which includes the additional steps of: providing a timing circuit in place of the zero cross detector; and selectively closing the switch with the timing circuit.
5. The method of claim 1 , which includes the additional steps of: providing a timing circuit in place of the phase detector; and selectively closing the switch with the timing circuit.
6. The method of claim 1 , which includes the additional steps of: providing timing control circuits in place of the zero cross detector and the phase detector; and selectively closing the switch with the timing circuits.
7. The method of claim 1 , which includes the additional steps of: sensing a value of a switch voltage with the phase detector; and opening the switch in response to a sensed voltage increase.