ZVS Flyback Driver - 24 volt 17 amp input (408 watts)

Homemade ZVS (Zero Voltage Switching) Flyback Driver running with 24 volts @ 17 amps from two ATX PSU's (12v rails @ 17amps in series). Flyback is from a Computer Monitor or Color TV (don't remember, I have several) with hand wound 6+6 center tapped wound with 14 AWG Automotive wire. ZVS main Capacitor is about 2uF - 250v and another red PP cap (near the flyback) about 2uF 200v. Two toroid inductors pulled from dead ATX PSUs one with 17 turns the other with 40 turns, both high current rated. Currently using 2x 0N05HD High Speed MOSFETs (50v - 60amp - 0.014 ohm rds(on)) which are not high enough voltage (by a longshot) but somehow seem to survive pretty well without blowing. I am going to replace them with High Speed IRFP264 MOSFETs which are 250v 38amp 0.075 ohm rds(on) and are a slightly beefier version of the IRFP250. Google "ZVS Driver" for typical schematic.

In the video is a multimeter set for current which shows the current being drawn by the driver from the 24 volt 17amp supply in real time. The plate I was using as a backdrop explodes at the end from overheating... Whoops!

Category:

Science & Technology

Tags:

• ZVS Driver
• High Voltage
• Flyback
• Zero Voltage Switching
• Arcing
• High Current

[juniortore1]

How do you make a ZVS draw a lot of current at low voltage like in this video? I only get big arcs at higher voltages

[Doom2pro]

@juniortore1 Pick Mosfets with a low RDS(on), and you must use short as possible thick wires for the leads from power fets to primary and capacitor. After that, making sure you have enough inductance in your b+ inductor, and a 0.8-2uF tank capacitor. Don't use a Mosfet in the TO220 package, use TO227 or Super TO227 package mosfets, as their larger size gives you better options in Maximum Continious Current, lower RDS(on), High Voltage and thermal dissipation.

[Doom2pro]

Also, experiment with the primary winding turns, sometimes more turns is better, sometimes not. It really depends on the flyback you are using. Also, use as low a gage wire (thick as possible) for the primary windings as you can get away with (core clearance vs turn count).

[Dri0m]

xD

[Doom2pro]

@juniortore1 One of your MOSFETS may be dead or not capable of driving at such high frequency and current.

[juniortore1]

@Doom2pro yes, when I powered it, it drew like one amp, but the 470 ohm resistor to one of the mosfets gate got hot. So maybe it was that. Today I will test with a new inductor and low power mosfets, if it works, I will go to high power IGBTs

[Doom2pro]

Also, if the windings for the primary are not going in the same direction, they will cancel each other out and your driver will appear dead and draw lots or current.

[Doom2pro]

@juniortore1 Mine has 17 turns, the inductor isn't as critical as you think. Most important things are wire/tracing thickness and input amperage.

[juniortore1]

@Doom2pro I think I had too little windings on the inductor. I used the inductor from a computer PSU with 25 turns. I later read on HV forums that you should have 50-100. Also could have been a bad mosfet. Ill have to get more mosfets

[Doom2pro]

@juniortore1 What's wrong with yours? Does it work at all?