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Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062
Hi all.
Has anyone had any luck increasing the output on these chips?
I noticed that the topology involves charging the EL up in one direction and then the other, so connecting a C/W multiplier should generate a higher voltage. The HV852 generates +180V off load so two stages should be enough.
Intended application is to generate +375V for a small Geiger tube. Doesen't need much current, but the voltage needs to be stable over time.
Registered Member #580
Joined: Mon Mar 12 2007, 03:17PM
Location: Melbourne, Australia
Posts: 410
i can not get the chip to even light a single neon bulb and the EL wire you gave me lights VERY VERY dimly when powered from this chip. when put though a fullwave voltage doubler, I get got 88v. putting 2 chips in series (with common clocks) gives some weird and changing waveform until it stabilises and then its just left with something weird, not any better than just a single chip. i am trying to drive a 140v 1.8pf ultrasonic transducer (the chip can drive up to 5nF), and i cant get a usable voltage across it, and i have no idea why, or why it cant drive a neon.
Conundrum, could you try to drive some sort of lamp with your chips if you have any still?
EDIT: on closer inspection, the chip is only rated to drive the h bridge at 500Hz max, and it will light a neon lamp ONLY with the doubler, using 4nf caps and now the output is half dead after some time of letting that run, and the neon can not light anymore (i didn't use a series resistor to the neon, it was quite dim to begin with)
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062
I had that happen to one of my chips due to an output side short.
Sorry to hear you are experiencing problems with these chips. If its any help I still have two HV852s and eight HV850s and some HV5523s.
For low power applications its better to drive the chip at lower frequencies as it draws much less quiescent current.
Avi, will do.
if its any help I can do the piezo experiment here, as i have plans to use this effect to drive a small laser scanner. If driven at resonance with a pair of bent sprung brass pieces the typical cheap disk piezo can move a wing as much as +/- 15 mm at under 100V input.
For those who want to try this, Avi has discovered that the chips do have their limits. best to put a low value resistor in series with each output and accept the loss of performance than risk frying the chip(s). Also its a wise move to add an 82V zener pair in inverse series across the pins. If you don't have any of these a 2M2 resistor can be used, this will drop Vout by about 8V or so.
Also, the HV850 draws 3.12mA at 5V (out of spec), and 2.6mA at 3.95V which is typical for a nearly charged LiPo. This is with 1 M R_EL and a 100uF tantalum across the Vcc and gnd pins.
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Double or triple output on HV852 / HV850 ?
