Cheap, high voltage class D amp?

Discussion in 'General Electronics Chat' started by wayneh, Feb 25, 2015.

  1. wayneh

    Thread Starter Expert

    Sep 9, 2010
    Do you know where to find one?

    I'm still screening ideas for powering some EL tape, which needs ~400Hz-2kHz at ~120V rms. Power in the 10W or more range would be fine.

    Since the required frequency is in the audio range, I'm wondering if a cheap class D audio amp might do the job for me. I could feed it 165V DC and use a signal generator to provide a line-level signal at the desired frequency. I don't care about fidelity so much as power efficiency.

    Most class D boards I've seen on e-bay and elsewhere are meant for lower rail voltages, ±35V and less. Automotive, I guess. The chip makers like TI and IR have literature on ICs that can handle 200V or more but I don't see devices anywhere that take advantage of that. Maybe they're not in the cheap range.

    Any ideas where to look?
  2. BobTPH

    Active Member

    Jun 5, 2013
    Does EL wire require a sine wave? If not, why not just run an H-bridge with a square wave? Perhaps an LC filter to smooth it out.

  3. wayneh

    Thread Starter Expert

    Sep 9, 2010
    It's hard to say. EL tape or wire is described as a leaky capacitor, with part of the power leakage being the light that is produced. Once the voltage exceeds a minimum, the intensity of light is said to be proportional to both voltage and frequency. Aging of the EL material is inversely proportional to V and ƒ also. If I recall correctly, age is extended by minimizing voltage and using frequency to get the brightness but don't quote me on that.

    Everything I've considered so far would produce a square wave, more or less, and it concerns me that the edges of the square wave might be hard on the EL material. I frankly have no idea if that matters, but I'd feel better if I could supply a sine wave or maybe even experiment with different wave shapes.

    I've consider feeding a 12V square wave into a (capacitively coupled) wall wart transformer run in reverse, to generate >120V AC. Another option is chopping DC at ~160V into a square wave. I'm confident that both of these will work, but I'm still looking for more options. The transformer may suffer from saturation at higher frequencies.