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Forum section: electronics / beginners

author: pranav
author_rank: Contributor
timestamp: April 30, 2017, 04:01:27 am
content: ...

author: ataradov
author_rank: Super Contributor
timestamp: April 30, 2017, 04:48:30 am
content: It looks like OP is asking how to apply diodes to the flyback transformer. If it is the case, then you need to clarify what you are doing exactly.

author: pranav
author_rank: Contributor
timestamp: April 30, 2017, 04:53:31 am
content: Quote from: ataradov on April 30, 2017, 04:48:30 amThis is schematic of circuit of my single transistor flyback driverSent from my Lenovo S850 using Tapatalk

author: ataradov
author_rank: Super Contributor
timestamp: April 30, 2017, 04:58:07 am
content: That's a very-very simplified schematic. It is basically useful for teaching purposes only. I would not use that in anything real, especially dealing with high voltages.But if you really want, then connect this diode across the primary winding. But your main concern here is flyback voltage. You need to design a proper conditioning circuit, and not just feed it into the base of that poor transistor.

author: Seekonk
author_rank: Super Contributor
timestamp: April 30, 2017, 11:30:20 am
content: Put a diode across the primary of your cars ignition coil and see how far you get, literally. The primary of an ignition coil peaks around 300V, it has to. You haven't listened to what was said before, you need a better transistor.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 30, 2017, 02:17:00 pm
content: I posted one picture and one link in the last thread. Did you read them?Tim

author: Zero999
author_rank: Super Contributor
timestamp: April 30, 2017, 04:02:26 pm
content: Quote from: pranav.appu.472 on April 30, 2017, 04:01:27 amAnother common beginner error here, seems to be making too many darn threads on the same topic. You'll find it easier, if you keep all of your questions about the same circuit/project to one thread. Before going any further, please check all of your replies to your other threads:https://www.eevblog.com/forum/profile/?area=showposts;sa=topics;u=136909With a flyback converter, you want the back-EMF to generate a very high voltage, which is transferred to the secondary by the turns ratio of the transformer. You may need suppression but it's no good limiting it to 0.7V as you would with a relay driver.I didn't bother with suppression. When I made this circuit, I used a high voltage transistor which could easily handle the high voltage spikes with no trouble.

author: pranav
author_rank: Contributor
timestamp: May 09, 2017, 10:50:04 am
content: I've connected a diode across the primary but now I can hear a high pitch noise from the load. Is it normal? Is it done?Sent from my Lenovo S850 using Tapatalk

author: danadak
author_rank: Super Contributor
timestamp: May 09, 2017, 11:15:26 am
content: These might be useful -https://www.circuitlab.com/circuit/t67g8z/mosfet-switching-inductive-loads/http://www.nxp.com/video/driving-inductive-loads-with-mosfets-nxp-quick-learning-44-part-1:MOSFETS-INDUCTIVE-LOADS-1Regards, Dana.

author: oldway
author_rank: Super Contributor
timestamp: May 09, 2017, 11:40:50 am
content: Do not forget that the free wheeling diode must be a fast recovery one.

author: Ian.M
author_rank: Super Contributor
timestamp: May 09, 2017, 01:54:15 pm
content: For a flyback converter you *NEED* that inductive spike. If you damp it out with an anti/parallel diode, you are limiting the dI/dt which is directly proportional to the rate of change of flux and thus the voltage induced in the secondary.The classic diode snubber circuit for flybacks has a fast diode in series with a parallelled resistor and capacitor D-(R|C). The resistor is chosen to discharge the capacitor sufficiently between pulses to keep the voltage below the max Vcbo of the transistor (assuming a low impedance base drive, otherwise Vceo), and the capacitor is chosen as a compromise between size/cost, minimising the voltage swin during a pulse so it can operate closer to max Vcbo, and the startup load due to the flyback having to charge the snubber cap to its intended voltage before the secondary output will reach its design value.For initial experimentation, replace the resistor with a series string of a much smaller resistor that will drop approx 10% of the max Vcbo if the maximum inductor current is passed through it and one or more reverse biassed Zener diodes, to make up the bulk of the snubber discharge voltage drop, of 70% of max Vcbo. That configuration although a lot more expensive is far more forgiving if the back-EMF spike is larger than expected, or the load on the secondary is varying and once the mean discharge current has been determined, you *may* then be able to replace it with a simple D-(R|C) snubber.

author: pranav
author_rank: Contributor
timestamp: May 27, 2017, 05:12:25 am
content: Will S2000N transistor will withstand the spikes?Sent from my Lenovo S850 using Tapatalk

author: Ian.M
author_rank: Super Contributor
timestamp: May 27, 2017, 05:42:16 am
content: Quote from: pranav.appu.472 on May 27, 2017, 05:12:25 amWith a 12V supply, probably, with only a minimal RC snubber to round off the spike a bit to keep it under 700V, but its a real bitch to drive - it needs >2A into the base to get the saturation voltage down to 1V, then you have to slam the base negative by a volt or so to get it to turn off quickly.See fig1 in its datasheet. Note the second 3TH41 diode to the right of the transistor under test (the S200N), going to a 1Meg resistor and 0.1uF cap, thats the D-(R|C) snubber network I mentioned above.

author: pranav
author_rank: Contributor
timestamp: May 27, 2017, 06:56:45 am
content: Quote from: Ian.M on May 27, 2017, 05:42:16 amMmm...that means I could probably drive it with a 12V 600VA battery...With a 47 ohm series resistor b/w primary & base of transistor, is there anything else I need to do...?Sent from my Lenovo S850 using Tapatalk

author: Ian.M
author_rank: Super Contributor
timestamp: May 27, 2017, 07:46:28 am
content: If the feedback winding has enough turns to get enough drive through the 47R resistor to get it to saturate, it willl exceed its 5V reverse Vbe limit when it cuts off.

author: pranav
author_rank: Contributor
timestamp: June 03, 2017, 11:32:37 am
content: I've used a ballast circuit and it's now working properly. Thanks to everyone..!Sent from my Lenovo S850 using Tapatalk

author: Zero999
author_rank: Super Contributor
timestamp: June 03, 2017, 03:52:14 pm
content: You're lucky to still be alive.

author: pranav
author_rank: Contributor
timestamp: June 04, 2017, 10:58:29 am
content: Quote from: Hero999 on June 03, 2017, 03:52:14 pmI know the seriousnessSent from my Lenovo S850 using Tapatalk

author: Le_Bassiste
author_rank: Frequent Contributor
timestamp: June 04, 2017, 11:26:31 am
content: "Herr, vergib ihnen, denn sie wissen nicht, was sie tun."

author: pranav
author_rank: Contributor
timestamp: June 05, 2017, 07:56:28 am
content: I'm still alive and my experiments of lichtenberg figures:Sent from my Lenovo S850 using Tapatalk

author: Zero999
author_rank: Super Contributor
timestamp: June 05, 2017, 08:15:53 pm
content: Quote from: pranav.appu.472 on June 05, 2017, 07:56:28 amWow, more proof you're completely incapable of following basic safety procedure.