A major challenge in automotive design: choosing automotive power line polarity protection diodes

A major challenge in automotive design is protecting electronic components such as control units, sensors and entertainment systems from destructive reverse voltages, voltage transients, electrostatic discharge (ESD) and noise on the power line. interference. Rectifiers are an ideal solution for automotive electrical power line protection. There are several important parameters to consider for these applications, including forward current, repeated reverse voltage, forward surge current, and melt speed.

Automotive electronic equipment test conditions and parameters in the application

The basic circuit for polarity protection is shown in Figure 1. Circuit (A) provides only polarity protection, while circuit (B) provides load dump suppression in addition to polarity protection.

Figure 1: Basic Polarity Protection Circuit

The following is a definition of the main parameters to consider when selecting a power line polarity protection diode for automotive applications.

Maximum Repeated Reverse Voltage (VRRM)

The maximum repeating reverse voltage is the maximum voltage that the diode can withstand in reverse bias mode. In reverse bias mode, leakage current through the diode creates heat in the diode junction and causes thermal runaway. Tests simulating this condition include ISO-7637-2 pulse 1 and 3a in the US and JASO D001-94 standards type B and E.Each in Japan. The peak voltages of these tests are shown in the table below.

Table 1: VRRM for ISO-7637-2 and JASO D001-94 standards