ruffrecords
Well-known member
I like he shaving transformer idea. Thay also include a thermal fuse to it is not going to burst into flames. 20VA gives you 83mA max secondary current which translates about 50mA dc HT output. Useful for a lot of projects.
I did do some research on generating HT from 12V. I was hoping to avoid using a transformer but it turns out to get 240V out of 12 V you need a very high duty cycle (over 95%) and of course you need 20 times the current at 12V so for 50mA HT you will be drawing 1amp pulses from the 12V supply. You can reduce the duty cycle to a more usable 50% using a transformer but you then end up with2A pulses. If you have to have a transformer then you might as well go the whole hog and make a mains input 250V dc output switcher. At least then the switching currents are a more reasonable. However, nobody seems to make this or supply transformers for it so it went no further.
Cheers
Ian
I did do some research on generating HT from 12V. I was hoping to avoid using a transformer but it turns out to get 240V out of 12 V you need a very high duty cycle (over 95%) and of course you need 20 times the current at 12V so for 50mA HT you will be drawing 1amp pulses from the 12V supply. You can reduce the duty cycle to a more usable 50% using a transformer but you then end up with2A pulses. If you have to have a transformer then you might as well go the whole hog and make a mains input 250V dc output switcher. At least then the switching currents are a more reasonable. However, nobody seems to make this or supply transformers for it so it went no further.
Cheers
Ian
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