Electric bicycle circuit structure and application characteristics

by:CTECHi     2021-07-30

With the development of science and technology, countries all over the world have higher and higher requirements for environmental protection. Therefore, as a new type of environmental protection battery, lithium iron phosphate batteries have begun to be gradually applied to electric vehicles and will become the head of the battery industry. The trend of future development. Generally, due to the characteristics of lithium iron phosphate batteries, the charging and discharging process needs to be protected in applications to avoid overcharging, overdischarging or overheating, so as to ensure the safe operation of the battery. Lithium iron phosphate batteries are used as a new energy source in the electric bicycle industry, which is inseparable from our lives. Our understanding of the circuit structure and application characteristics of electric bicycles is imminent. Structure and application characteristics.

The simplified model of the discharge circuit of the lithium iron phosphate battery protection board of the electric bicycle is shown in Figure 1. Q1 is a discharge tube and uses an N-channel enhancement MOSFET. In actual work, according to different applications, multiple power MOSFETs are used in parallel to reduce the on-resistance and enhance the heat dissipation performance. RS is the equivalent internal resistance of the battery, and LP is the lead inductance of the battery.

During normal operation, the control signal controls the MOSFET to turn on, and the terminals P+ and P- of the battery pack output voltage for the load. At this time, the power MOSFET is always in the on state, and the power loss is only the conduction loss, and there is no switching loss. The total power loss of the power MOSFET is not high, and the temperature rise is small, so the power MOSFET can work safely. However, when the load is short-circuited, because the loop resistance is very small and the battery's discharge capacity is very strong, the short-circuit current suddenly increases from tens of amperes in normal operation to hundreds of amperes. In this case, the power MOSFET is easily damaged.

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