In the car door system, common locks include the door lock, the door handle lock and the child lock. The number of locks that need to be unlocked in CPM depends on the system architecture. If it is a centralized architecture, then one CPM needs to drive all locks, including four door locks, two child locks and four door handle locks. If it is distributed architecture, each CPM only needs to drive one door lock, one child lock and one door handle lock. The number of locks is different, the energy required is different.

During the unlocking process, the operating voltage of the motor is generally set to 12V, and the current changes over time, divided into startup stage, steady-state stage and stall stage. Figure 3-2 shows the current changes during the operation of a typical car door unlocking motor. During startup stage, the counter electromotive force has not been established, and the current rapidly rises to 2 times the rated current, reaching up to 5A, forming a transient surge spike. This stage lasts for only 10ms short time. After the inrush current, the motor's back electromotive force is established, the current quickly falls back and stabilizes in the rated current range, generally around 3A, with a duration of 150ms. The worst case is motor stall, with current reaching 8A and lasting for 50ms. Therefore, the total energy required to unlock this motor is:

If a CPM is needed to unlock all the doors, considering the number of locks is 10 and the rounds is 2, the total energy required is:

Figure 3-2 Typical Diagram of Current Change Over Time During the Operation of a Car Door Lock Motor