The development of automobiles has greatly enhanced our daily lives, offering unparalleled convenience. Modern vehicles are equipped with numerous advanced electronic systems that provide both reliability and comfort. However, beneath this comfort lies a challenging environment where these electronic devices must endure harsh conditions. Ensuring their protection is critical, and one effective method is the implementation of an isolated power supply at the front end of these devices. This isolation helps shield the electronics from severe interference, preventing potential damage.
Due to phenomena such as the ignition of internal combustion engines, the disconnection of inductive loads, or the abrupt interruption of parallel load currents, the actual input voltage waveform can become distorted. The ISO7637-2 standard models these adverse conditions, simulating some of the worst-case scenarios. Below are examples of some of these extreme waveforms:
**Pulse 1:** An instantaneous pulse resulting from the disconnection of an inductive load from the power supply.
**Table 1 - Pulse 1 Parameters:**
From Table 1, we see that voltages as low as -100V can occur on a 12V power supply line, while -600V can appear on a 24V line. Without proper isolation and an EMC filter circuit, sensitive components like MCUs, LCDs, and audio systems could be severely affected.
**Pulse 2a:** A transient pulse caused by a sudden interruption of current in a device connected in parallel with the device under test (DUT), due to harness inductance.
**Table 2 - Pulse 2a Parameters:**
**Pulse 2b:** A transient pulse generated by a DC motor functioning as a generator once the ignition circuit is turned off.
**Table 3 - Pulse 2b Parameters:**
**Pulse 3a:** A negative transient pulse triggered during the switching process.
**Table 4 - Pulse 3a Parameters:**
**Pulse 3b:** A positive transient pulse generated during the switching process.
**Table 5 - Pulse 3b Parameters:**
**Pulse 4:** A voltage drop occurring when starting the engine's starter motor.
**Table 6 - Pulse 4 Parameters:**
**Pulse 5b:** A load-dump transient pulse generated by an alternator when a discharged battery is disconnected, assuming the alternator has automatic protection.
**Table 7 - Pulse 5b Parameters:**
For applications requiring robust performance under such extreme conditions, the E2405ASBD-20W power module is highly recommended. It offers a wide input voltage range of 6V to 63V and delivers a stable 5V/4A output. With just a minimal addition of an EMC filter circuit at the input, it exhibits excellent EMC interference resistance. This ensures that downstream electronic equipment operates consistently even under significant voltage fluctuations.
Another variant, the E240512ASDD4-20W, provides an even wider input voltage range of 6V to 63V, with dual outputs: 5V/3A and 12V/0.4A. The regulated 5V output can power the MCU, LCD, and other critical components, while the unregulated 12V output can support audio systems and other peripherals.
In conclusion, the integration of robust power modules with appropriate filtering solutions is essential for maintaining the integrity and longevity of automotive electronics. These modules provide the necessary protection against harsh electrical environments, ensuring smooth operation across various vehicle systems.
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