Question about zvs drivers and tv fly-back transformers  - Page 1
Forum section: electronics / beginners

author: DarkZero
author_rank: Regular Contributor
timestamp: May 17, 2015, 09:17:01 am
content: Hello all !Out of interest i would like to know whats the working frequency of those fly-back transformers found in old TV and whats the frequency of those zvs driver circuits. im seeking to build car amplifier and im planing to use core from an old TV fly-back transformer and zvs driverThanks in advance

author: tron9000
author_rank: Frequent Contributor
timestamp: May 17, 2015, 09:22:28 am
content: For flyback converters, Typically 10's to 100's of kHz. Depends on application.

author: Isad
author_rank: Frequent Contributor
timestamp: May 17, 2015, 10:10:36 am
content: Quote from: DarkZero on May 17, 2015, 09:17:01 amYou could google zvs frequency usally zvs are around 24-75khz depends on what your using it oni have one for my self but i forogt what the frequency were i was getting.Btw dont try anything stupid with flyback and a zvs they are more dangerus than u thinktry a 555 timer first.ZVS are great and such but can give you a nice shock and proably some heart problems.Dont try andto much

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 17, 2015, 10:29:38 am
content: NTSC TV, 15.7kHz. But that has little to do with the core. The core itself can be used to as low a frequency as you care to wind it for, and will still be useful at over 200kHz (with some derating).A car amplifier requires circuitry very different from either a TV horizontal deflection circuit or a ZVS driver. What circuit were you thinking of?Tim

author: DarkZero
author_rank: Regular Contributor
timestamp: May 17, 2015, 11:05:01 am
content: Hey all !OK. guess i need to give you guys some more info to get my problem solved.my first post regarding this was this onehttps://www.eevblog.com/forum/beginners/sg3525-cant-make-it-work/i got that figured out as you can see in the post then i went and used this schematichttp://translate.google.com.tr/translate?hl=tr&sl=auto&tl=tr&u=http%3A%2F%2Felectrodb.ro%2Fatelier%2Fauto%2Famplificator-auto%2F(second picture with the mosfets) Then i said cool everything works i made transformer from and old fly-back tv core 4/4 2.5mm² wire and 100/100 0.5mm² i have set oscillator to about 100Khz i put 10k loads on both secondaries turn it on primary side gives me nice square waves secondary give me spikes at about 1vi have made a lots of iron core transformers but in this project i cant seem to go past transformer ^^

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 17, 2015, 05:15:09 pm
content: That circuit doesn't give turns ratio or a rectifier and filter...It has no current sense, so it's very likely to explode at... anything. It has no regulation, it runs fully open loop. The only reason it even starts up in the first place is because of soft start, which is very wishful thinking.The gate driver circuit is also inconsistent, but it'll probably go slow enough you won't notice.Given the voltages in the text, I would guess it needs a full wave rectifier, 1:4 turns ratio. A typical FBT core has probably a 13mm peg, or 132 mm^2 cross section, which will handle 0.2-0.3T being ferrite. With a maximum 16VDC input, you need 2.4 turns minimum per half of the primary winding. 3 or 4 turns would be fine.So your winding should be: 4+4 turns primary, 16+16 turns secondary.For the primary, wind one flat layer of many wires in parallel, or copper strip (wrapped with tape for insulation). It is better to use many thinner wires in parallel, than one single solid piece rated for the current.For the secondary, use fewer pieces of wire, and wind the 16+16 turns directly on top of the primary as closely as possible.With center taps, the primary and secondary are themselves composed of halves. These should be interleaved as layers, too.So you should have:4 turns primary half16 turns secondary half4 turns primary other half16 turns secondary other halfand connect the halves in series, finish to start, so the wire is always going around the same direction.The switching layout has to be extremely dense and low inductance, otherwise you'll have transistors blowing up themselves, not sharing current evenly, oscillating, etc.You should have an oscilloscope to measure these waveforms as well.Tim