EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: derGoldstein on March 22, 2017, 07:45:43 am
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I have a circuit with an input voltage of between 5V to 20V, which I want to add reverse-polarity protection to. Attached is the circuit that I'm going to try.
If the power is connected correctly the mosfet allows the current through and the led on the right (which is green) turns on. If it's connected in reverse then the current is blocked and the led on the left (which is red) turns on.
Firstly -- will this work the way I described above?
Second, I want to make sure that I'm using the right mosfet. What I'm looking for is a logic-level mosfet (turns completely on by the time Vgs reaches 5V) which can also tolerate Vgs going up to 20V+. Here are some that I've found:
http://www.mouser.co.il/ProductDetail/Diodes-Incorporated/DMG7430LFG-7/?qs=sGAEpiMZZMshyDBzk1%2fWi4P4wC6csLMYIC%252bvOe09BV0%3d (http://www.mouser.co.il/ProductDetail/Diodes-Incorporated/DMG7430LFG-7/?qs=sGAEpiMZZMshyDBzk1%2fWi4P4wC6csLMYIC%252bvOe09BV0%3d)
http://www.mouser.co.il/ProductDetail/Diodes-Incorporated/DMN3018SSS-13/?qs=sGAEpiMZZMshyDBzk1%2fWi4P4wC6csLMY9iJ21xVc378%3d (http://www.mouser.co.il/ProductDetail/Diodes-Incorporated/DMN3018SSS-13/?qs=sGAEpiMZZMshyDBzk1%2fWi4P4wC6csLMY9iJ21xVc378%3d)
http://www.mouser.co.il/Search/ProductDetail.aspx?R=BSC100N06LS3_Gvirtualkey63830000virtualkey726-BSC100N06LS3G (http://www.mouser.co.il/Search/ProductDetail.aspx?R=BSC100N06LS3_Gvirtualkey63830000virtualkey726-BSC100N06LS3G)
http://www.mouser.co.il/ProductDetail/ROHM-Semiconductor/RQ3E100BNTB/?qs=sGAEpiMZZMshyDBzk1%2fWi5brl1xcCtmLSztafmJM%252bzn0STSOkcaEpQ%3d%3d (http://www.mouser.co.il/ProductDetail/ROHM-Semiconductor/RQ3E100BNTB/?qs=sGAEpiMZZMshyDBzk1%2fWi5brl1xcCtmLSztafmJM%252bzn0STSOkcaEpQ%3d%3d)
The maximum current that will flow into the circuit is around 5A, but I want to avoid heat buildup so I looked for mosfets that can handle over 10A, though I understand that some of those are going to be overkill.
Lastly, is there a reason to use a p-channel mosfet instead? Many example circuits opt for a p-channel mosfet connected to the positive input rather than an n-channel mosfet connected to the negative input. But n-channel mosfets are a lot cheaper and there's a much wider range of them. Is using a p-channel mosfet more efficient in some way?
Thanks in advance.