Patent ID: 7180722

Claim:
An ionizer comprises: an alternating current (AC) voltage source having an output outputting a waveform with a positive half-cycle ant a negative half-cycle; an electrode electrically coupled to the output of the AC voltage source; a reference proximate the electrode; and a sensing circuit including: a return current nulling node electrically coupled to the output of the AC voltage source and the reference; a ground node separately electrically coupled to ground; a positive ion current sensor having a positive ion current sense node and being coupled between the return current nulling node and the ground node, the positive ion current sense node being configured to output a positive ion signal proportionate to a sensed positive ion current; a negative ion current sensor having a negative ion current sense node and being coupled between the return current nulling node and the ground node, the negative ion current sense node being configured to output a negative ion signal proportionate to a sensed negative ion current; and a feedback control circuit coupled to at least one of the positive ion current sense node and the negative ion current sense node, the feedback control circuit being coupled between the AC voltage source and the electrode, the feedbaek control circuit being configured to control the AC waveform being applied to the electrode based upon at least one of the positive ion signal and the negative ion signal.