I'm not well-versed in the domain of electrical engineering, so please bear with me if this question is too basic.
I'm putting together an automatic watering system for my greenhouse. Basically, it's a solar panel > voltage regulator > schottky diode > battery > timer > water pump.
The Schottky diodes I've used so far came with the solar panels. However, I need extra ones. This is where the problem arise. What type of Schottky diode do I need?
I'm using two 9V/2W/~200mAh solar panels connected in series (18V) and I've been looking at a 40V 3A (1N5822) Schottky diode. Would this be a reasonable Schottky diode to use? The panels are connected in series in order to trickle charge a 12V lead acid battery at 13.8V.
- How do I know which Schottky diode is the right one for my use?
- What considerations do I need to take?
- How do I see what the voltage drop for this type of diode is?
Best Answer
A 'feature' of Schottky diodes is high reverse leakage (when compared to ordinary diodes).
The part you have chosen has 20mA of reverse leakage (max) at 100C ambient
In reverse, if you had that amount of leakage at that temperature, there would be up to 276mW of power dissipation in the device nd this would lead to a further 11 degrees of temperature rise. This would cause increased leakage.
In this particular case, the part does indeed look suitable provided you can live with a few mA of leakage.
You can see the exponential nature of leakage current vs. temperature for these devices in the graph from the datasheet:
Always check for the reverse performance for a Schottky device; under some reverse bias conditions, they can go into thermal runaway.