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| High voltage/low current Power supply |
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| H713:
Capacitive dropping would also allow you to use a relatively small 60Hz transformer designed for a 240V input. Such transformers can be quite small. |
| Zero999:
--- Quote from: H713 on April 08, 2020, 07:13:15 pm ---Capacitive dropping would also allow you to use a relatively small 60Hz transformer designed for a 240V input. Such transformers can be quite small. --- End quote --- Be careful. A mains transformer is inductive, especially when lightly loaded and connecting a capacitor in series with it won't necessarily drop the expected voltage. The wrong value will form a resonant circuit with the transformer, causing a high current to flow, a high voltage across the transformer, some sparks and smoke. |
| Red_Micro:
I was also looking into off-line-switchers like this approach: ti.com/tool/PMP11302 |
| jbb:
So 600V L-L... +20% for high line *sqrt(2) for rectifier = 1018V DC This might be doable with a 1700V SiC (Silicon Carbide) MOFET flyback converter. Several companies make parts exactly for low power flyback work. Despite the high peak voltage stress, flyback is a strong contender because it can be designed for really wide input voltage range. I expect that someone, somewhere makes a suitable product already. Options: * Make your own: you'll learn a lot but it will take ages * Can you go single phase to neutral? * Maybe you can find a wide input range DC DC converter (they make them for PV equipment) and deploy your own rectifier? |
| Red_Micro:
--- Quote from: jbb on April 09, 2020, 12:48:12 am ---So 600V L-L... +20% for high line *sqrt(2) for rectifier = 1018V DC This might be doable with a 1700V SiC (Silicon Carbide) MOFET flyback converter. Several companies make parts exactly for low power flyback work. Despite the high peak voltage stress, flyback is a strong contender because it can be designed for really wide input voltage range. I expect that someone, somewhere makes a suitable product already. Options: * Make your own: you'll learn a lot but it will take ages * Can you go single phase to neutral? * Maybe you can find a wide input range DC DC converter (they make them for PV equipment) and deploy your own rectifier? --- End quote --- Flyback is a good approach for handling wide input voltage range. But the fact that I may not strictly need isolation, and considering the high price of SiC FETs, made me think about a buck converter like this TI App Note (ti.com/tool/PMP11302). Unfortunately, I can't go single phase to neutral. Just Line to Line in this application. And of course, this will be a good a experience where I expect to learn a lot. |
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