The MK I (one), MK1.5 (one-point-five), and MK II (two), refer to ways of driving the FET, in a MC34063 based switching supply. Here is a drawing showing some preliminary tests done years ago:
<https://lh3.googleusercontent.com/-eCGO167pdmQ/VtqFvC9Xx-I/AAAAAAAAX9c/EV9ayAhexxg/s1600/MC34063_drive.gif> The MKI, is the oldest and only actively pulls up the FET gate. Turning it off is passive thru a resistor. MK1.5, uses the MC34063 to turn ON the FET, thru the diode, then actively turns it off by way of a PNP. MKII uses a complimentary NPN/PNP buffer to both actively turn ON and OFF the FET. After a bit of tweeking, I managed to get 80% efficiency out of the MK1.5 design. The buzzing is coming off the coil, and will be a problem with all these designs. Its just the way the MC34063 works. It may be improved by choosing a different coil, or even potting one in epoxy resin. Usually, I find the worst buzzing under light loads. If you draw more current, you will get a continuous pulse train, as opposed to a burst of pulses here and there, creating the audible buzz. On Friday, March 4, 2016 at 3:19:39 PM UTC-8, Luka C wrote: > > Reading about the power supplies for the clock, I found the MK 1.5 power > supply (schematic: > https://threeneurons.files.wordpress.com/2011/08/mc34063_mk15cm1.gif) and > have already built a clock based on it, but the coil seems to be buzzing > pretty noticeably, especially when all the tubes turn OFF -> ON or change > numbers at the same time, you can hear the buzzing frequency change at > those moments. I suppose that changing the inductor could fix it so I'll > give it a try. But, on multiple threads I saw people mentioning MK.II > version of the power supply but wasn't able to find the schematic for it. > So, does anyone have the schematic for it and would be kind to share it or > was it never even made publicly available? > > Thanks in advance :) > -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/95861de1-c346-4e89-a1cd-278ccb42ecb6%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
