Path: ...!Xl.tags.giganews.com!local-1.nntp.ord.giganews.com!nntp.supernews.com!news.supernews.com.POSTED!not-for-mail NNTP-Posting-Date: Thu, 25 Apr 2024 21:31:43 +0000 From: John Larkin Newsgroups: sci.electronics.design Subject: Re: CCFL transformer Date: Thu, 25 Apr 2024 14:29:52 -0700 Organization: Highland Tech Reply-To: xx@yy.com Message-ID: <1eil2jpdp2tnumqb7snfj04o1ip1oud9ks@4ax.com> References: X-Newsreader: Forte Agent 3.1/32.783 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 89 X-Trace: sv3-2Dze2N4MQMmBxcVlyZPCLbMMa8ybYfyhCmS9fn33349j69G6zVTeThVqhwVvM7spcuJS9cAoiRpF8ef!qZMpPa8ct3Gswc4eiY8GKCL265dQwAd+B72JWFIVZO7J/WvfQfIUaS9Qp5rRvrjGr0XteNJorEG6!7Rc7rQ== 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: 4291 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. If you need fast rise/fall, or clean pulses, the transformer could be difficult.