How does a MOSFET regulator work?

To understand how a MOSFET regulator works, it's important to know be familiar with the different types of powersports voltage regulators. Most manufacturers use what is often called a shunt type regulator, with newer and more expensive models sometimes using a MOSFET regulator.  

A Mosfet regulator is a better Shunt regulator

It is not often explained that both types are shunt regulators, which refers to how the battery voltage regulation is performed.  They both operate the same way, the difference is in the components they use to do so.  The regulator function of a voltage regulator-rectifier works by shunting, or redirecting current from the stator to ground to be dissipated as heat when it senses the battery voltage is high enough, and therefore fully charged.  

Difference between a Shunt regulator and a Mosfet Regulator

A more common shunt-type regulator uses a solid-state electrical component called a Silicon Controlled Rectifier (SCR) as the switch to send stator current to the battery or to ground.  A MOSFET regulator uses its namesake, a Metal Oxide Semiconductor Field Effect Transistor to do the switching.  The main differences are in switching speed and heat generation.  The SCR is very slow to switch, and requires lots of electrical current to complete the switch, resulting in lots of heat and variation in the battery voltage.  The MOSFET regulator is extremely quick to switch positions, and requires much less current to control, resulting in a much cooler unit, and significantly more stable battery voltage.  Heat is the primary killer of voltage regulator-rectifiers, so when you use a part that runs cooler and works better with the same type of connection and mounting package, why not make the change?

RMSTATOR builds high quality MOSFET regulators for many popular makes & models, and offers an excellent all-in-one universal upgrade kit!