spark_hands
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Hello all,
I'm building a 7v to 180v supply (for nixies) using a max1771 IC. At 180v, the least amount of current I will draw is 2mA and the most I will draw is 94mA. I've read through the datasheet a few times, but I had a few questions as I am quite a novice when it comes to switching power supplies.
1. The description states it can control 30mA to 2A loads. Is this the output load it can handle (i.e. 2A at 180v) or the load it can handle going into (2A@5v) the circuit? I'm inclined to believe it relates to the output load.
2. In order to choose an inductor, they suggest using the following formula:
L >= (Vin(max) * 2mS) / ILim
Is ILim the current at 7v or 180v? And why? I suppose I do not understand the origins of the formula, but would like to.
2. How do I calculate the inductor current rating and saturation current rating? This person is using a 2A inductor for 50mA loads at 220v:
Nixie HV Switching PSU
This is how I believe they calculated that value, but I am not sure:
Their max output voltage and current is 50mA @ 220v so that's 11W
Their min input voltage is 9v and that would mean at a 11W, a 1.22A inductor is needed. Atop of that, the rating was increased to allow for a safety tolerance and to account for the fact the switcher is not 100% efficient. Is my mindset correct? Now what about the saturation rating?
3. There is an Rsense resistor that limits the current. This seems to be dependent on the input voltage, output voltage and the inductor according to the graphs. I'm completely lost on how to figure this out! :sad:
Any help is appreciated! Thanks all
I'm building a 7v to 180v supply (for nixies) using a max1771 IC. At 180v, the least amount of current I will draw is 2mA and the most I will draw is 94mA. I've read through the datasheet a few times, but I had a few questions as I am quite a novice when it comes to switching power supplies.
1. The description states it can control 30mA to 2A loads. Is this the output load it can handle (i.e. 2A at 180v) or the load it can handle going into (2A@5v) the circuit? I'm inclined to believe it relates to the output load.
2. In order to choose an inductor, they suggest using the following formula:
L >= (Vin(max) * 2mS) / ILim
Is ILim the current at 7v or 180v? And why? I suppose I do not understand the origins of the formula, but would like to.
2. How do I calculate the inductor current rating and saturation current rating? This person is using a 2A inductor for 50mA loads at 220v:
Nixie HV Switching PSU
This is how I believe they calculated that value, but I am not sure:
Their max output voltage and current is 50mA @ 220v so that's 11W
Their min input voltage is 9v and that would mean at a 11W, a 1.22A inductor is needed. Atop of that, the rating was increased to allow for a safety tolerance and to account for the fact the switcher is not 100% efficient. Is my mindset correct? Now what about the saturation rating?
3. There is an Rsense resistor that limits the current. This seems to be dependent on the input voltage, output voltage and the inductor according to the graphs. I'm completely lost on how to figure this out! :sad:
Any help is appreciated! Thanks all