Hi everybody,
I'm working on a high voltage LED indicator installed on a main circuit which charges a capacitors bank.
The indicator is simply a combination of a zener diode (which sets reference voltage), a pair of voltage dividers (one for voltage sensing, the other for voltage reference) and a comparator at the output of which is connected an LED with its balancing resistor (see schematic...VDCin is about 850 volts).
The purpose of all this is to turn on the LED when the charging voltage reaches (and stays above) a certain threshold (around 650 volts).
Now, while the voltage between the LED pins (1.2 volts) is well under the spec limit and the behaviour of the comparator is as expected (a surge without hysteresis when the voltage reaches the target threshold), the current flowing out of the comparator is absolutely not enough to continually and sensibly light on the LED, in fact it lays in the range of the MICRO amperes (see graphs).
I tried to change the configuration feeding the comparator with a 9 volts battery but the same problem arised: very tiny amperage at the output still. However I'd like to keep feeding the comparator without recurring to an external supply.
Are the voltage dividers not so well configured? (not enough current through them...)
Is the type of comparator which is not suited for this application?
(though I think that a comparator is still better than a transistor given the voltages involved...I was thinking to an LM339)
Maybe a neon lamp replacing the LED would be better? (what type of lamp...)?
Or...what else?
Thank you for taking the time to answer me.
I'm working on a high voltage LED indicator installed on a main circuit which charges a capacitors bank.
The indicator is simply a combination of a zener diode (which sets reference voltage), a pair of voltage dividers (one for voltage sensing, the other for voltage reference) and a comparator at the output of which is connected an LED with its balancing resistor (see schematic...VDCin is about 850 volts).
The purpose of all this is to turn on the LED when the charging voltage reaches (and stays above) a certain threshold (around 650 volts).
Now, while the voltage between the LED pins (1.2 volts) is well under the spec limit and the behaviour of the comparator is as expected (a surge without hysteresis when the voltage reaches the target threshold), the current flowing out of the comparator is absolutely not enough to continually and sensibly light on the LED, in fact it lays in the range of the MICRO amperes (see graphs).
I tried to change the configuration feeding the comparator with a 9 volts battery but the same problem arised: very tiny amperage at the output still. However I'd like to keep feeding the comparator without recurring to an external supply.
Are the voltage dividers not so well configured? (not enough current through them...)
Is the type of comparator which is not suited for this application?
(though I think that a comparator is still better than a transistor given the voltages involved...I was thinking to an LM339)
Maybe a neon lamp replacing the LED would be better? (what type of lamp...)?
Or...what else?
Thank you for taking the time to answer me.
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