Thanks for the detailed description, John. I will do some experiments
with the module I have here and report back. I am quite busy at
university at the moment so that may take a couple of weeks.
Thanks again!
Jens
Am 10.09.2014 03:15, schrieb taylorjpt:
>>Now that I have you here, can you answer me another question? I was
wondering if the circuitry could be tweaked as to allow a maximum
output voltage of 250V or even 300V. I will only need a maximum
current of 10mA since I want to build a testing stand for single Nixie
tubes.<<
If you replace the 30.1K Radj resistor on the module with a 15K
resistor (Or put another 30K resistor in parallel) this will change
the max feedback current from 165uA (Rbottom = 10K || 30.1K = 7.5K) to
about 200uA (Rbottom = 10K || 15K = 6K) or Vmax goes from 200V to
250V. The main output capacitor is rated 250V and since it is a good
quality part you should have no problem operating it at 250V. 300V is
pushing it but for a test fixture you should be OK for short periods.
To get 300V, replace the 30.1K resistor with 10K (Rbottom = 10K || 10K
= 5K) to push the feedback current to 240uA. In all cases, the
Radj=Open voltage will be about 150V.
At 300V the output diode will be seeing about 420V (600V limit) for a
12V input and the main switch will be seeing about 42V (60V limit).
At voltages above 200V both the transistor and diode will incur higher
switching losses (The diode because of itself and the transistor
because of the diode) so keep an eye on the dissipation of both those
devices.
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