Path: ...!Xl.tags.giganews.com!local-2.nntp.ord.giganews.com!nntp.supernews.com!news.supernews.com.POSTED!not-for-mail NNTP-Posting-Date: Fri, 26 Apr 2024 18:07:11 +0000 From: John Larkin Newsgroups: sci.electronics.design Subject: Re: CCFL transformer Date: Fri, 26 Apr 2024 11:05:19 -0700 Organization: Highland Tech Reply-To: xx@yy.com Message-ID: References: <1eil2jpdp2tnumqb7snfj04o1ip1oud9ks@4ax.com> X-Newsreader: Forte Agent 3.1/32.783 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 98 X-Trace: sv3-iaidGxbeGQPdG4GFgYj1yECYToMlyH6+nxPeegZTKHJAVBnqvDsdrnV08ug+S4Vfii1K78NPdXNTd2d!egkzM95R8UXRhJECRb66K7QtCHI3zC33ZQzHYz7XuXGK0AcvFE8fN2MLMzBhjdm/NFlJn94V++0y!nGu3SA== X-Complaints-To: www.supernews.com/docs/abuse.html X-DMCA-Complaints-To: www.supernews.com/docs/dmca.html X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly X-Postfilter: 1.3.40 Bytes: 4914 On Fri, 26 Apr 2024 00:49:52 +0200, Klaus Vestergaard Kragelund wrote: >On 25-04-2024 23:29, John Larkin wrote: >> On Thu, 25 Apr 2024 22:23:31 +0200, Klaus Vestergaard Kragelund >> wrote: >> >>> On 25-04-2024 17:08, John Larkin wrote: >>>> On Thu, 25 Apr 2024 10:18:42 +0200, Klaus Vestergaard Kragelund >>>> wrote: >>>> >>>>> On 24-04-2024 16:23, John Larkin wrote: >>>>>> On Wed, 24 Apr 2024 09:37:24 -0400, legg wrote: >>>>>> >>>>>>> On Wed, 24 Apr 2024 01:57:36 +0200, Klaus Vestergaard Kragelund >>>>>>> wrote: >>>>>>> >>>>>>>> Hi >>>>>>>> >>>>>>>> I need a low distributed capacitance winding transformer, for a HV >>>>>>>> stepup function (3.5kV) >>>>>>>> >>>>>>>> I am zeroing in on similar concept as CCFL transformers with >>>>>>>> sectionalized bobbin. >>>>>>>> >>>>>>>> For example: >>>>>>>> >>>>>>>> https://www.coilcraft.com/en-us/products/transformers/power-transformers/ccfl-transformers/fl/ >>>>>>>> >>>>>>>> Possibly using Triple Insulated Wire to create some distance between the >>>>>>>> individual turns. >>>>>>>> >>>>>>>> Not many sells CCFLs these days. >>>>>>>> >>>>>>>> Guess I will keep it alive.... >>>>>>>> >>>>>>>> Regards >>>>>>>> >>>>>>>> Klaus >>>>>>> >>>>>>> When there are a lot of turns, 3xFEP is not the way to >>>>>>> go. Too bulky. The three layers is basically a trick to >>>>>>> avoid creepage requirements for pri-sec safety. That's >>>>>>> not what you need here. >>>>>>> >>>>>>> Anything off the shelf will be a great time saver. >>>>>>> >>>>>>> RL >>>>>> >>>>>> I sometimes use an autoflyback stage with a DRQ-series dual inductor, >>>>>> followed by a c-w multiplier using sot-23 dual HV diodes. That's cheap >>>>>> and easy, given a reasonable supply voltage, like 24. >>>>>> >>>>> >>>>> I cannot use capacitive doubler thingies, there's no output DC voltage. >>>>> >>>>>> You can also just buy a potted HV supply and move on to design >>>>>> something else. >>>>>> >>>>> >>>>> I need it cheap, so cannot buy COTS >>>>> >>>>>> There are also potted c-w bricks, but they are a lot more expensive >>>>>> than buying the diodes and caps. >>>>>> >>>>>> Custom magnetics only makes sense at high volume, or for real exotica >>>>>> like transmission-line transformers. >>>>> >>>>> I have almost never used standard magnetics. Most projects has >>>>> requirements that dictate custom, or in higher volumes price is the key. >>>>> >>>>>> >>>>>> I'm about to embark on a custom tapped inductor and I'm not looking >>>>>> forward to it. Drawings, quotes, revised drawings, more quotes, >>>>>> samples, tests, released drawings, MOQs, all that. >>>>>> >>>>> >>>>> Yeah, boring work. >>>> >>>> What input do you have, and what output do you want? >>>> >>> >>> I have 24VDC in, and 3.5kV peak pulse with 10% duty cycle at 100kHz. I >>> have a working circuit, but just a little too much loss due to the >>> transformer parasitics, so working to change the construction to get the >>> optimum transformer design >> >> You could make 3.5KV DC, and then switch. There are high-voltage fets >> around. >> >I have looked into that. I cannot find resonable valued transistors at >4kV, prices ranges above 20 USD per piece. But maybe I have not searched >in the right place. > >On top of that, I need a positive pulse, 3.5kV, and also a negative >pulse (600V or so). The can be solved with a transformer. Oh.