Path: ...!weretis.net!feeder9.news.weretis.net!feeder8.news.weretis.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Klaus Vestergaard Kragelund Newsgroups: sci.electronics.design Subject: Re: CCFL transformer Date: Fri, 26 Apr 2024 00:49:52 +0200 Organization: A noiseless patient Spider Lines: 94 Message-ID: References: <1eil2jpdp2tnumqb7snfj04o1ip1oud9ks@4ax.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Fri, 26 Apr 2024 00:49:54 +0200 (CEST) Injection-Info: dont-email.me; posting-host="e4641593304cf59b54bfa46688de6c8b"; logging-data="3425716"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX19H6fTwXjl1eIuVjRyijsKq4g8RAVKZJvI=" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:zrktS7RBpBVu1bSLrmqqFcBI754= In-Reply-To: <1eil2jpdp2tnumqb7snfj04o1ip1oud9ks@4ax.com> Content-Language: en-US Bytes: 4687 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.