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265V PS Needed For Braille Display

Posted by Cliff on from the obscure-voltages dept.

Harald Klein writes: "We are developing a cheap braille display for visually impaired people. A big problem is the power supply for the piezo elements. They need 265V DC, 0.5 mA max. The logic needs 5V DC, 15 mA. It is absolutely necessary to provide logic power before providing the high voltage. Even so the high voltage should be removed before logic power and signals. Any power supplies in mind that meet the specs?"

1 of 10 comments (clear)

  1. Power supply design by Anonymous Coward · · Score: 3

    Shouldn't be too hard to make one. Start with a 5V supply capable of giving 1A or so. Have a delayed signal from the "logic voltage" start up a 50Hz (or so) sine wave oscillator (simple 555 circuit + small IC-based audio power amp would do), feeding a mains transformer in reverse. Put the output from the transformer through a suitably-rated full-wave bridge rectifier and smoothing circuit. The input to the transformer will have to be capable of driving at least 0.5*265/x mA, where x is the rms voltage output of the amp.

    You'll have to work out the conversion factors to ensure you can get to 265V output based on oscillator amplitude (make it adjustable), transformer ratio (depends what mains voltage the "primary" (which you are using as a secondary!) is designed for), rectifier ratios and losses. You might need to start with more than 5V to be able to get up there: say 15V perhaps?

    BE CAREFUL: despite the low current capability, 265V can do you serious harm.

    ac.uk