How do you protect a Mosfet from a short circuit?
The voltage across the internal resistance can be sensed using simple comparator or even a transistor, which switches on at a voltage of around 0.5V. You can thus avoid the use of a sense resistor (shunt), which usually produces an undesirable extra voltage drop. The comparator can be monitored by a microcontroller.
How much voltage can a Mosfet handle?
Typically, about eight volts will turn on the device completely. When on, the part exhibits a low resistance without any non-linear forward voltage drop as seen in bipolar transistors. Modern MOSFETs can have on resistances of less than 10 milliohms.
How much current is needed to drive a Mosfet?
A mosfet gate looks like a capacitor. It’s a really weird cap, but a cap none the less. It takes essentially zero current to turn it on or off at DC. The only thing you need current for is to charge / discharge the gate capacitance (and the other strange stuff from feedback).
What is inside a Mosfet?
Just like other transistors, such as the BJT, a MOSFET is made of a semiconductor material, most commonly silicon. A semiconductor has very low electrical conductivity (in its pure form), but when you introduce an impurity, the conductivity increases dramatically. Adding an impurity is called doping.
How do I know if my MosFet is bad?
A good MOSFET should have a reading of 0.4V to 0.9V (depends on the MOSFET type). If the reading is zero, the MOSFET is defective and when the reading is “open” or no reading, the MOSFET is also defective. When you reverse the DMM probe connections, the reading should be “open” or no reading for a good MOSFET.
What causes a MosFet to fail?
Fault conditions can be either due to an electrical circuit failure or a mechanical fault with a load such as a seized motor. This leads to Electrical Overstress (EOS). Typically the consequence of EOS is the short circuiting of at least 2 of the 3 MOSFET terminals (gate, drain, source).
How do I know if my alternator diode is bad?
Usually, a bad alternator diode will cause your headlights or instrument panel lights to flicker or dim and, sometimes, drain battery power overnight, or in minutes. * To check for a possible bad alternator diode, switch your voltmeter to a low setting on the AC (alternating current) voltage scale.
Can a bad diode drain a battery?
A malfunctioning diode in the alternator can create a parasitic drain on a car’s battery. Diodes should allow current to pass in only one direction, but a bad diode will keep the charging circuit open even when the engine in not running, allowing the battery to go dead. This often happens overnight.
What causes repeated alternator failure?
Bad diodes are a common cause of alternator failure. The diodes are part of the rectifier assembly that converts the alternator’s AC output to DC. The alternator’s charging output flows through six diodes in the rectifier assembly before it goes to the battery and electrical system.
How do I know if my alternator is draining my battery?
If the engine starts but dies immediately, your alternator probably isn’t keeping your battery charged. If a jump starts and keeps your car running, but the car can’t start again off of its own power, a dead battery is likely your answer.