A system for plasma-based processing, comprising: a plasma processing chamber configured to contain a plasma; a substrate support positioned within the plasma processing chamber and disposed to support a dielectric or semiconductor substrate, an ion-energy control portion, the ion-energy control portion including a controllable DC voltage source, wherein the output voltage of the DC voltage source is controllable to establish two or more separate concentrations of ion energies at the surface of the substrate; a switch-mode power supply coupled to the substrate support and the ion-energy control portion, the switch-mode power supply including at least two switching components configured to convert the output voltage of the DC voltage source into a particular voltage waveform and apply the particular voltage waveform to the substrate support to produce a substantially constant negative voltage at the surface of the substrate between short positive voltage pulses; a controller coupled to each of a first and a second of the at least two switching components of the switch-mode power supply by a corresponding one of a first and second separate drive-control-signal lines, the controller providing a first and second drive-control signals, respectively, to separately open and close the first and second of the at least two switching components to generate the particular voltage waveform and modulate the output voltage of the DC voltage source to effectuate the two or more separate concentrations of ion energies at the surface of the substrate; and a waveform memory coupled to the controller, the waveform memory including timing information for the drive-control signals. a plasma processing chamber configured to contain a plasma; a substrate support positioned within the plasma processing chamber and disposed to support a dielectric or semiconductor substrate, an ion-energy control portion, the ion-energy control portion including a controllable DC voltage source, wherein the output voltage of the DC voltage source is controllable to establish two or more separate concentrations of ion energies at the surface of the substrate; a switch-mode power supply coupled to the substrate support and the ion-energy control portion, the switch-mode power supply including at least two switching components configured to convert the output voltage of the DC voltage source into a particular voltage waveform and apply the particular voltage waveform to the substrate support to produce a substantially constant negative voltage at the surface of the substrate between short positive voltage pulses; a controller coupled to each of a first and a second of the at least two switching components of the switch-mode power supply by a corresponding one of a first and second separate drive-control-signal lines, the controller providing a first and second drive-control signals, respectively, to separately open and close the first and second of the at least two switching components to generate the particular voltage waveform and modulate the output voltage of the DC voltage source to effectuate the two or more separate concentrations of ion energies at the surface of the substrate; and a waveform memory coupled to the controller, the waveform memory including timing information for the drive-control signals.