1.What is load dumping
Load dump, English for load dump, refers to the moment of disconnecting the power supply from the load, due to the sudden change of load voltage caused by the sudden change of the power supply. In the field of automotive electronics, load dumping refers to the threat of damage to other equipment connected to the generator power supply when the battery is charged, which causes the connection between the motor and the battery to cause a large voltage spike in the generator output.
The car throws the load into single throwing and double throwing, and only cutting off the generator is the single throwing of the load; Only cut off the battery for the battery single throwing; Cutting off the generator and battery at the same time is called double throwing. Due to the high reliability of the automobile operation process, the load dumping test formulated by the ISO organization must have its inherent rationality. The load dump test is a very severe destructive test.
2.When to throw the load 7637-5a 5b
Automobile load dumping is mainly affected by three factors, such as maximum voltage, internal resistance and duration, and how to control the comprehensive impact between the three is the key to our automobile load dumping protection.
Specifies the test level and measurement method for electrical conduction disturbance and immunity of road vehicles along the power line with 12V electrical system and 24V electrical system. Among them, the two standard tests of pulse waveform 5a and 5b are the most destructive test tests and the most difficult test standards.
The 7637-5A standard is an unsuppressed waveform, and the 7637-5B is a waveform with voltage suppression at the front end of the generator.
Shanghai Leimao has its own laboratory, which can help customers do load dumping testing, and the picture below shows Shanghai Leimao helping customers do 5B testing.
3.Energy Suppression Design for 7637-5A 5B.
In the case of 5A, the test pulse provides the worst-case scenario. In the case of 12V, it is specified that the range of its US is 79 volts to 101 volts, while the range of internal resistance is 05 ohms to 4 ohms, surge voltage action time 40ms to 400ms. If the load dump protection has been tested 10 times under the specified pulse, then it proves that the protection is qualified.
Shanghai Leimao is an EMC solution design and device manufacturer, we have verified a variety of solutions for this test, and provide you with a variety of solutions one by one, engineers can choose by themselves.
4.A simple TVS protection solution.
Shanghai Leimao launched a simple structure load throwing protection scheme, as long as one TVS
1) Protection against 7637-5A
Test TVS data against 24V systems.
2) Protection scheme against 7637-5B.
Many cars come with their own limiters, which can ensure that the output surge does not exceed the 5B set value, which further reduces the risk of load dumping, for such requirements, we can choose cheap solutions, such as Shanghai Leimao's SM5S24CA series car TVS and 66smdj24ca。
2.What are the design considerations for DC-DC?
Due to the characteristics of the TVS itself, there will be a range between the clamping voltage and the working voltage, so the DCDC withstand voltage of the 12V system is selected as 40V, and the DCDC withstand voltage of the 24V system is selected as 60V.
For the above explanation of load dumping or specific circuit design requirements, you can consult with Shanghai Leimao EMC brother who specializes in electromagnetic compatibility.
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