MOSFETs and Diodes: Key Components in Reverse Polarity Protection

According to the latest research, the automotive industry is estimated for a significant shift. By 2025, the value of electronic components in high-end vehicles is projected to surpass $6000, driven by the increasing sophistication of vehicle features. This trend is expected to accelerate if the EU successfully bans the sale of internal combustion engine vehicles by 2035, leading to an even higher proportion of electronic components in electric vehicles.

Despite the technological advancements in electric vehicles, the demand for robust and reliable automotive electronic components remains paramount. The failure of electronic control systems during driving can pose serious safety risks to passengers.

A critical component in the vehicle’s electrical system is the reverse polarity protection circuit. This circuit safeguards the battery and other sensitive electronic components from damage caused by reverse current, which can occur due to human error, external forces, or environmental factors. The ISO-16750-2 4.7 standard outlines specific safety requirements for transient reverse voltage testing.

One common design for reverse polarity protection circuits involves a series diode. While this method is simple, it results in significant power dissipation due to the voltage drop across the diode. For higher-power applications, MOSFETs are used to reduce power losses. Figures 2 and 3 illustrate the use of P-channel and N-channel MOSFETs, respectively. Although MOSFETs offer improved efficiency, they typically require more space and increase overall design costs.

When a battery applies reverse polarity, the diode becomes reverse biased, preventing current flow. Similarly, in MOSFET-based circuits, a reverse input voltage causes the MOSFET channel to close, effectively blocking the current.