I’ve seen these generic CCFL inverters on ebay quite regularly, and wondered how good they would be for running neon-art based on a few short sections of tubing.
The original purpose of these high voltage inverters is to run long thin backlight tubes for LCD panel illumination. They have two control inputs, both of which seem to be designed for logic level. One is the ENABLE input and is basically operated with a high logic level. I found it turned on at about one and a half volts. The ADJUST input controls the intensity over a limited range by varying the voltage from 0V (brightest) to 5V (dimmest).
You can fudge the controllers to run at full intensity by tying the ADJUST wire to the negative supply wire and the ENABLE wire to the positive supply wire, although I’m not sure if it’s really rated to be raised to the full supply voltage.
The circuit uses a common switch-mode control chip to drive the transformer primaries using dual MOSFET packages that are either operating as a push-pull driver (one chip) on a winding centre tapped to the positive rail or ganged up as a pair of double MOSFETs (two chips) doing the same thing.
Each transformer drives a pair of series tubes that are commoned through some sense circuitry at their mid-point on the low voltage side of the circuit. I think this senses tube current for regulation purposes, and also detects if a tube breaks, as the circuit will go into standby mode if a tube is disconnected, although it depends on which tube is disconnected!
On some of the units there is a small capacitor connected between the secondary outputs, possibly to give a small load to limit open circuit voltage if the tubes fail or get damaged.
The modules seem to be able to drive at least a few feet of neon on each output and the current drawn at 12V adjusts to the load. I tried a couple of short 2′ (600mm) argon/mercury tubes and a longer 2.5′ (750mm) neon filled tube and then both in series and it lit them no problem. This suggests it may have an estimated driving ability of about 5′ (1.5m) on each output for 12mm diameter argon/mercury tube and less for neon. Intensity is good for indoor use.
Since the circuit is intended for matched length tubes for current regulation and sensing purposes, it would probably be best to keep all tubes connected to it at a similar length.
