ZVS (Zero Voltage Switching) Flyback Driver - Simulation

Schematic for a Zero Voltage Switching (ZVS) Flyback Driver. Simulation shows how it works. Initial pulse is driven into primary, and once the tank capacitor is charged, the LC (Inductor-Capacitor) oscillation starts. When the voltage between the Drain and Source of each MOSFET reaches 0 volts, the MOSFET switches on to reenergize the LC and keep the oscillaton going. Each MOSFET alternates the driving duties, one for each half of the sinewave.

With this driver (provided it is properly built and receives adaquit input power) you can get very high current output from just about any Flyback (or other ferrite transformers) you can find (See my other videos for a ZVS powered Arcs).

The two 470 ohm resistors MUST be 2 Watts or better, the 10k resistors can be 1/4 watt, nothing special. The two Zener Diodes must be 12 to 18 volts, not higher or they will over drive the MOSFET Gates! Also the diode current rating isn't important here. The two normal Diodes MUST be High Speed (120ns recovery time or less) and High Voltage (600v or better), BYV26E's are great for this and current here also isn't important. If you are using more than 48 volts for input power, you will need to increase the resistance of the 470 ohm AND the 10k ohm resistors otherwise you will burn out your zeners and possibly your MOSFETs!

The two Power MOSFETs must be heatsinked even for short use, and the VDS (Voltage Drain Source) must be no less than 60 volts, or 3 x the input voltage (200 volts or more highly suggested). Also the RDS(on) (Resistance Drain Source On) must be 150 mOhm or less! Normal Bipolar Transistors (BJTs) wont work here although IGBTs will work with some modifications (due to their high driving requirements, switching speed fallbacks).

When winding the Primary, you MUST use High Current, heavy gage insulated wire! Automotive wire works great, I use AWG 12 for my primaries. Number of turns isn't important, but I find 5-7 each works well. The two windings MUST be going in the SAME DIRECTION (wind 10 turns and remove some insulation from the middle for the center tap for a 5+5 primary), otherwise one will cancel out the other and your driver will appear dead and will draw lots of current and your MOSFETS will rapidly heat! If your Flyback's core doesnt provide enough clearance to wind heavy gage wire for the primary, go down in gage or use another flyback. If you break your flyback core, just superglue it back together.

When building this circuit, be it on a PCB or just soldered together with wires, you MUST use thick copper wire or heavily tinned tracers on the Ground, V+, MOSFET Drain and Source, and Primary Leads or output power will suffer!

The V+ Inductor (top) MUST be rated for high current (thick wires), around 20-40 turns, round toroidal iron core chokes work best. Inductance value may vary, increase for more voltage (output), decrease for more current (output).

The bipolar capacitor on the primary side must be high voltage (250+ volts, MKP type) and anywhere from 0.68 uF to 4.0 uF. Larger values will result in more output current at the cost of lower resonant frequency and thus lower switching frequency. The large red capacitors found in computer monitors and some CRT TV sets work great for this. Also Power Factor correcting caps found in AC Box Fans work great.

Warning! - Output Current from Flyback will be deadly! DO NOT touch the Ground or HV cable with your bare hands to draw arcs! Use a non conductive object such as a long wooden stick or glass rod to manipulate either wires! You have been warned!

If you want to, you can fiddle with the simulation... It's made with this great Java Applet Simulator, the components are mostly ideal, not real world and the sim wont be dead on but that wasnt the point.

Sim: www.falstad.com/circuit/

To Load: Click File then Import and paste the contents of this file into it: dumped-archives.ath.cx/HV_Driver/ZVS_Driver/zvs.shc2.txt

Видео ZVS (Zero Voltage Switching) Flyback Driver - Simulation канала Doom2pro