But where is the DC coming from? If it is a cheap power source (a rectifier plugged or wired into AC), the DC into the lights could be intermittent, and so caus

But where is the DC coming from? If it is a cheap power source (a rectifier plugged or wired into AC), the DC into the lights could be intermittent, and so cause flicker. For true continuous DC, you need a good rectifier or get the current directly from batteries.