Reverse Polarity Protection Circuit With LED Indicator
Introduction Automotive power systems operate under exceptionally harsh conditions. In particular, the car battery must handle numerous loads, and it can be challenging to determine the state of these loads simultaneously. Designers must consider the possible impact of the various pulses generated by the power line when these loads are under different operating conditions and potential fault states. This is Part I of a two-part series describing how to design a reverse polarity protection circuit. In this article, we will introduce the various pulses on automotive power lines. Then we will discuss the common types of reverse polarity protection circuits, with a focus on a P-channel MOSFET circuit. Part II will discuss a reverse polarity protection circuit design using an N-channel MOSFET and driver IC. Pulse Interferences Figure 1 shows the various types of pulses that may appear on the power line in different application scenarios. For example, if the high-power load suddenly turns off, then the battery voltage can overshoot; if the high-power load suddenly starts up, then the battery voltage drops. When the inductive wiring harness is suddenly loosened, the load has a negative voltage pulse. Meanwhile the AC ripple is superimposed on the battery when the generator operates. When using jumper wires, the backup battery may be applied incorrectly, which causes reverse polarity. This reverse polarity can remain for a significant period of time.
To handle the various pulse interferences that may exist on these automotive power lines, industry associations and major vehicle manufacturers have developed relevant test standards to simulate power line transient pulses. These standards include the ISO 7637-2 and ISO 16750-2, as well as the test standards for Mercedes-Benz and Volkswagen. As the most front-end circuit of the module, the reverse polarity protection circuit must also meet industry test standards.
Reverse Polarity Protection Circuit With LED Indicator
Introduction Automotive power systems operate under exceptionally harsh conditions. In particular, the car battery must handle numerous loads, and it can be challenging to determine the state of these loads simultaneously. Designers must consider the possible impact of the various pulses generated by the power line when these loads are under different operating conditions and potential fault states. This is Part I of a two-part series describing how to design a reverse polarity protection circuit. In this article, we will introduce the various pulses on automotive power lines. Then we will discuss the common types of reverse polarity protection circuits, with a focus on a P-channel MOSFET circuit. Part II will discuss a reverse polarity protection circuit design using an N-channel MOSFET and driver IC. Pulse Interferences Figure 1 shows the various types of pulses that may appear on the power line in different application scenarios. For example, if the high-power load suddenly turns off, then the battery voltage can overshoot; if the high-power load suddenly starts up, then the battery voltage drops. When the inductive wiring harness is suddenly loosened, the load has a negative voltage pulse. Meanwhile the AC ripple is superimposed on the battery when the generator operates. When using jumper wires, the backup battery may be applied incorrectly, which causes reverse polarity. This reverse polarity can remain for a significant period of time.
To handle the various pulse interferences that may exist on these automotive power lines, industry associations and major vehicle manufacturers have developed relevant test standards to simulate power line transient pulses. These standards include the ISO 7637-2 and ISO 16750-2, as well as the test standards for Mercedes-Benz and Volkswagen. As the most front-end circuit of the module, the reverse polarity protection circuit must also meet industry test standards.
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