Experiments with flybacks

Description: The initial design utilized a small flyback transformer from an old computer, paired with a simple driver circuit based on a 555 integrated circuit (IC). This circuit featured AC coupling to the driver transistor and was assembled on a perforated board within a protective enclosure. The flyback transformer was powered by two potential supply voltages, a discrete 12V voltage regulator, and a 555 astable oscillator, allowing for variable frequency and duty cycle, albeit not independently. The circuit produced sparks between two balls, with the spark length serving as a precise measurement of the available voltage. For testing, a 500 kOhm resistance was placed in series with the output, alongside a 50 pF Leyden jar across the spark gap. Without the Leyden jar, the sparks appeared weaker and exhibited blue or violet coloration, generating approximately 20 kV at a few mA. However, the circuit experienced issues with excessive power dissipation in certain resistors (R1 and R3) and inadequate base drive for the power transistor at high duty cycles with a 50V supply due to AC coupling. Additionally, the small flyback transformer exhibited a tendency to spark to its core, the enclosure, and the heat sink of the power transistor, lacking sufficient power to operate a "lifter." This insulation issue was mitigated by filling the entry point of the output cable into the transformer with silicone glue. The power supply was later capable of powering a Jacob's ladder without complications. The circuit could also generate adequate voltage for a "lifter" by substituting the snubber network with a 4.3 nF 1600V capacitor.

The second iteration featured a larger flyback transformer and an improved method for driving the power transistor from the 555, producing a ramp-shaped base current that followed the ramp-shaped collector current. This was achieved by powering the base through an inductor, the primary coil of a transformer, and employing a MOSFET to interrupt the base current. A direct current connection facilitated uniform operation across various duty cycles. Additionally, a system was implemented to recycle energy stored in the inductor using the transformer’s secondary coil and a fast diode. The 555 was configured to generate a square wave with an adjustable duty cycle, utilizing a binary array of capacitors to set the oscillation frequency, with approximately 5 kHz being the most effective frequency. The flyback transformer was equipped with a capacitor across its output, producing violent and dangerous shocks. An integrated regulator and a single capacitor served as a snubber. Coupled with the diode across the transistor, this configuration allowed for energy recycling from the flyback transformer during light load conditions. The driving transformer was selected from salvaged monitor components, although it could be larger due to nearing saturation at maximum current; nevertheless, it sufficed for this application. This driver demonstrated significantly reduced power consumption compared to the first version while delivering considerably higher power output. The assembly was housed in an open box with ample clearance around the flyback transformer. Testing involved connecting the circuit to a ball electrometer constructed from two 1.4 cm styrofoam balls painted with China ink, suspended from threads and affixed to a metal tube. The estimated voltage at this separation was around 25 kV. A video demonstration was also created. Furthermore, a "lifter" was constructed to operate with these power supplies; these curious devices are capable of lifting their own weight off the ground using ionic wind, featuring a conventional triangular structure.The first attempt used a small flyback from an old computer and a simple driver based on a 555 IC with AC coupling to the driver transistor, with this schematic diagram. It was assembled in a perforated board and put in a box. The circuit has two possible power supply voltages for the flyback, a discrete 12 V voltage regulator, and a 555 astable oscillator where the frequency

and the duty cycle can be varied, although not independently. It is similar to other drivers that can be found in the Internet. I tested it by producing sparks between balls. The spark length between balls is a precise measurement of the available voltage. In these experiments, I put 500 kOhms of resistance (5 1 W 100 kOhms resistors) in series with the output, and a 50 pF Leyden jar across the spark gap. Without the jar, the sparks are weaker an blue or violet. It produces about 20 kV, at a few mA. This circuit had problems with excessive power dissipation in some resistors (R1 and R3) and insufficient base drive for the power transistor when the duty cycle was high with 50 V supply, due to the AC coupling.

The small flyback had also a tendency to spark to its core, to the box, and to the heat sink of the power transistor. It also had not enough power to power a "lifter". The insulation problem was solved by filling the tube where the output cable enters the transformer with silicone glue.

The power supply can now power a Jacob`s ladder without problems. I could also make the circuit generate enough voltage for a "lifter" (see below) by replacing the snubber network by a simple 4. 3 nF 1600 V capacitor: The second version uses a bigger flyback transformer and a better system to drive the power transistor from the 555, producing a base current in the form of a ramp, following the collector current, that is also a ramp in these circuits.

I obtained this by powering the base through an inductor, the primary coil of a transformer, and using a MOSFET to interrupt the base current. A DC connection makes it work uniformly with any duty cycle. A system for recycling the energy stored in the inductor was also implemented, using the secondary coil of the transformer and a fast diode.

The 555 was set to produce a square wave with adjustable duty cycle, and a binary array of capacitors was used to set the oscillation frequency. About 5 kHz works better, and it`s not useful to be able to change it. This flyback transformer has a capacitor across its output. Shocks from it are quite violent and dangerous. I used an integrated regulator, and a single capacitor as snubber. Combined with the diode across the transistor, the circuit recycles the energy stored in the flyback transformer when the load is light.

The driving transformer was simply selected among several salvaged from monitors. It could be bigger, because it almost saturates at the maximum current, but was enough for this use. This driver consumes much less power than the first one, and produces significantly more power. I assembled it in an open box, with more clearance around the flyback. Below it is being tested connected to a ball electrometer: The electrometer is made with two 1. 4 cm styrofoam balls painted with China ink, suspended from threads, taped to a metal tube. I estimate about 25 kV at this separation of the balls. A video. I made a "lifter" to be operated by these power supplies. These curions devices lift their own weight from the ground using ionic wind. It has the conventional triangular structure,