Transition control in a bias supply
Bias supplies and bias control methods are disclosed. One method comprises applying an asymmetric periodic voltage waveform and providing a corresponding current waveform at an output node relative to a return node; receiving a signal to change from a current state of the asymmetric periodic voltage waveform to a next state of the asymmetric periodic voltage waveform; and adjusting, during a transition from the current state to the next state, at least one portion of the asymmetric periodic voltage waveform and simultaneously adjusting a fundamental frequency of the asymmetric periodic voltage waveform to settle at the next state.
1. A bias supply to apply a periodic voltage comprising:
an output node;
a return node;
a switch network and at least one power supply coupled to the output node and the return node, the switch network and the at least one power supply configured, in combination, to apply an asymmetric periodic voltage waveform and provide a corresponding current waveform at the output node relative to the return node, wherein each cycle of the asymmetric periodic voltage waveform includes a first portion that begins with a first negative voltage and changes to a positive peak voltage during the first portion, the asymmetric periodic voltage waveform also changes from the first portion to a third voltage level during a second portion, and the asymmetric periodic voltage waveform comprises a third portion that includes a voltage ramp from between the third voltage level and a fourth voltage level;
a metrology component configured to receive and sample voltage and current signals indicative of the asymmetric periodic voltage waveform and the corresponding current waveform to provide digital representations of the asymmetric periodic voltage waveform and the corresponding current waveform; and
a controller configured to control the switch network and at least one power supply based upon the digital representations of the asymmetric periodic voltage waveform and the corresponding current waveform, wherein the controller comprises a transition control module configured to:
receive a signal to change from a present state to a next state; and
adjust, during a transition from the present state to the next state, a voltage of the at least one power supply and simultaneously control a switching frequency of the switch network to adjust a fundamental frequency of the asymmetric periodic voltage waveform to settle at the next state after a defined transition.
2. The bias supply of claim 1 , wherein the transition control module comprises a lookup table to access waveform timing parameter values and a corresponding number of pulse width modulated cycles for each timing parameter value.
3. The bias supply of claim 1 , wherein the transition control module comprises a feedback control loop to adjust the fundamental frequency of the asymmetric periodic voltage waveform during the transition.
4. The bias supply of claim 3 , wherein the feedback control loop utilizes a bang-bang control scheme.
5. The bias supply of claim 3 , wherein the feedback control loop utilizes a proportional-integral-derivative control scheme.
6. The bias supply of claim 1 , wherein transition control module is configured to adjust the at least one power supply and the switching frequency of the switch network according to a transition type selected from the group consisting of a linear current ramp transition, an exponentially-decaying current transition, and a concave-parabolic current transition, intentional-overshoot transition type, and intentional-undershoot transition types.
7. The bias supply of claim 1 , wherein the controller is configured to adjust the fundamental frequency according to a predefined transition time using a predefined transition type.
8. A method for applying a periodic voltage comprising:
applying an asymmetric periodic voltage waveform and providing a corresponding current waveform at an output node relative to a return node, wherein each cycle of the asymmetric periodic voltage waveform includes a first portion that begins with a first negative voltage and changes to a positive peak voltage during the first portion, the asymmetric periodic voltage waveform also changes from the positive peak voltage to a third voltage level during a second portion, and the asymmetric periodic voltage waveform comprises a third portion that includes a voltage ramp from between the third voltage level and a fourth voltage level;
receiving a signal to change from a present state of the asymmetric periodic voltage waveform to a next state of the asymmetric periodic voltage waveform; and
adjusting, during a transition from the present state to the next state, at least one of the first, second, and third portions of the asymmetric periodic voltage waveform and simultaneously adjusting a fundamental frequency of the asymmetric periodic voltage waveform to settle at the next state after a predefined transition time using a predefined transition type.
9. The method of claim 8 wherein the adjusting comprises accessing a lookup table to access waveform timing parameter values and a corresponding number of pulse width modulated cycles for each timing parameter value.
10. The method of claim 8 , wherein the adjusting comprises utilizing a feedback control loop to adjust the fundamental frequency.
11. The method of claim 10 , wherein the feedback control loop utilizes a bang-bang control scheme.
12. The method of claim 10 , wherein the feedback control loop utilizes a proportional-integral-derivative control scheme.
13. The method of claim 8 , wherein the adjusting comprising adjusting the fundamental frequency according to a transition type selected from the group consisting of a linear current ramp transition, an exponentially-decaying current transition, and a concave-parabolic current transition, intentional-overshoot transition type, and intentional-undershoot transition types.
14. The method of claim 8 , comprising adjust the fundamental frequency according to a predefined transition time using a predefined transition type.
15. A non-transitory medium encoded with instructions that are executable by a processor and/or are readable by a field programmable gate array, the instructions comprising instructions to:
cause a bias supply to apply an asymmetric periodic voltage waveform and provide a corresponding current waveform during a present state;
process a signal to change from a current state of the asymmetric periodic voltage waveform to a next state of the asymmetric periodic voltage waveform; and
cause the bias supply to adjust, during a transition from the present state to the next state, at least one portion of the asymmetric periodic voltage waveform and simultaneously adjust a fundamental frequency of the asymmetric periodic voltage waveform to settle at the next state, wherein the fundamental frequency during the transition is different than the fundamental frequency during either the present state or the next state.
16. The non-transitory medium of claim 15 , wherein the instructions comprise instructions to:
access a lookup table to access waveform timing parameter values and a corresponding number of pulse width modulated cycles for each timing parameter value to adjust the fundamental frequency.
17. The non-transitory medium of claim 15 , wherein the instructions comprise instructions to adjust the fundamental frequency of the asymmetric periodic voltage waveform during the transition with a feedback control loop.