Schematic Rise

This is the Practical Current Limiting Coil Driver schema Diagram. The p-channel devices are switched off by current sensors when the coil current reaches 10 A. The operation is similar to that of a switching-type power supply. The Schottky diodes and resistors are for spike protection.

The LM3410 IC is a constant current LED driver useful in either boost con-verter or SEPIC design applications. A SEPIC (Single Ended Primary Induct-ance Conver ter) design allows the power supply’s output voltage to be set above, below or equal to its input voltage. In this application the chip is configured as a boost-converter (i.e. the output voltage is greater than the input voltage). 

The LM3410 is available in two fixed-frequency variants. Using either the 525 kHz or 1.6 MHz clock version it is possi-ble to build a ver y compact LED driver. The output stage can supply up to 2.8 A, allowing several high-power LEDs to be driven from a rechargeable Lithium cell or several 1.5 V bat-teries. The chip also features a dimmer input giving simple PWM brightness control.Output current is defined by an external shunt resistor. To keep losses low the LM3410 uses an internal voltage reference of just 190 mV.

Power dissipation in the shunt resistor is therefore low. Using the desired value of LED current the value and power dissipation of the shunt resistor is given by:

R_Shunt = 0.19 V/I_LED
P_Shunt = 0.19 V*I_LED 

A 10 µH coil (L1) will be suf ficient for most applications providing it has a suitable satu-ration current rating. The Input and output capacitors should be 10 µF ceramic t ypes with a low value of E SR . Many distributor s including Farnell stock these component s. The Diode should beaSchottky type (as in all switching regulators). The author has developed a PCB for this design; the corresponding Eagle files can be freely downloaded from www.elektor.com/090850. In sum-mar y the most important features of the LM3410 are:

This is a simple Fly back Transformer Driver Circuit Diagram and an efficient flyback driver for modern cylindrical rectified television flybacks. Many sites doesnt provide diagram driving these transformers, they simply say that they are bad.

I dont agree. In fact I built this schema. I spent a lot of time for finding resonant frequency (around 15Khz) and duty cycle. These transformers best work at around 90% duty cycle. You may notice corona breakdown at terminals and pfffff sound (as well as the ozone smell) when adjusting the off time trimmer to near 500-300 ohms. Of course it will work for other tipes of flyback as frequency and duty cycle have a large range.

 Flyback Transformer Driver Circuit Diagram




Frequency range can be increased using multiposition switch for other values of C3 capacitor ,for example 2 nF for 80KHz-200000KHz, but didnt found flybacks with so high resonant frequencies, in addition with higher values of c3 , eg 200nF, 2uF the
frequency will drop making possible the use of ignition coils, and rectified power transformers @50Hz to charge high voltage electrolitic caps at 300-400V). Unfortunately my ignition coil died because insulation breakdown (too long drawn arcs)...
I was able to power a small (20cm) Spark Gap tesla coil Using these dc rectified flybacks to charge primary tank capacitor.

The operation is simple
The 555 is wired as an astable and the capacitor is charged only through the 4,7Kohm trimmer (notice the diode) and discharged only through the 2.2 Kohm trimmer, making the duty cycle full adjustable. The square wave is then feed in a totem pole made up of a 2N3904 and a 2N3906, which are cheap, and easy to find. The totem pole ensures the gate being charged and discharged very fast (approx 50nS i think). The IRF840 is a cheap (i found it for 4euros) reliable and powerful power mosfet, it has current capability of 8 A continuous and 32A pulse, 800V drain source voltage, protecting internal zener diode. There is a snubbing network to ensure that voltage spikes are kept low (unless the insulation of the transformer start to leak) protecting both transistors and 555 IC. 100 ohm is a compromise between decay time and voltage spike.

Comments and specifications:
The 100 ohm snubber must me a 5W resistor, or it will burn at long operations
The led is only for safety purposes
Use a dead man switch (pushbutton) for safety
The power supply must supply at least 2-3 A if you want decent arcs (20000 KV)

Dangers:
The flyback driven in this way can supply a significant current, aldough the heart fibrillation starts at 30mA
I recommend caution to avoid painful arc-burns.
The arc is a hot plasma, never operate the schema in presence of flammable substances.
Charging high voltage capacitors is a serious life threat, so if you arent unexperienced just draw arcs and no more

This device when rectified generates static voltage that can be a little annoying.... (or fun, i sprayed with corona a plastic pen from positive terminal and then i was able to attract little pieces of paper)

Disclaimer:
I dont assume any responsibility of the damages or discruptions dove by this device, to persons or things. Any irresponsable action would be a serios danger. This is high voltage threat it with respect.

author: Jonathan Filippi