Abstract: Disclosed are example efficient circuits that produce spark discharges for hydrocarbon conversion (or treatment of other mixtures) using a high-voltage rectified DC supply to discharge a capacitor (either internal or external) across a two-electrode gap, optimized to minimize waste energy by operating in a constant current, approximately-constant current, or constant power mode. The circuits may operate off of a standard electrical supply line (e.g. 120 VAC or 240 V AC, 60 Hz, single-phase or multi-phase). The disclosed approach is scalable to any number of discharge gaps while maintaining similar pulse characteristics and electrical efficiency.