(BMS) lies in the crucial role MOSFETs play in protecting lithium batteries. BMS is an electronic device capable of monitoring and managing batteries, serving as a link between the battery and the user. The main function of a lithium battery management system is to achieve intelligent management and maintenance of battery units, monitoring battery status through functions such as state monitoring and abnormal fault protection.

In this regard, MOSFETs play a significant role in protecting lithium battery boards. The main function of MOSFETs is to detect overcharging, overcurrent during charging and discharging, and short circuits. NMOS products are widely used in battery management systems, serving as the main switch for the battery pack. Additionally, NMOS types are also used in high-end switches through charge pumps. In a battery management system, MOSFETs' switch characteristics are typically utilized to control the connection and disconnection of the battery's main circuit to external power supply. In scenarios requiring uninterrupted power supply, the battery management system needs to ensure that the MOSFET's conduction state remains unchanged during microcontroller restarts or upgrades, maintaining the original state.

For such a critical circuit design in the battery management system, correct charging circuit design and component selection are crucial for prolonging the rechargeable battery's lifespan.

MOSFETs, or Metal-Oxide-Semiconductor Field-Effect Transistors, differ from diodes and bipolar transistors. While diodes only allow current in one direction and cut off in the reverse direction, and bipolar transistors amplify small currents into controlled large currents, MOSFETs control current with small voltages.

In metals, the electron density is so high that an external field can only penetrate a short distance into the material. However, in semiconductors, the lower-density electrons (and possibly holes) can respond to an external field, allowing it to penetrate deeply into the material.

The main function of MOSFETs is to amplify electrical signals, used in electronic devices for switch control, power management, data transmission, etc. The principle of MOSFETs is based on the reverse bias effect of PN junctions, where the resistance is very high and the current is almost zero when the PN junction is in reverse bias.

The working principle of a MOSFET is to control the voltage and current between the source and drain. It is a type of FET (Field-Effect Transistor) with an insulated gate, where the voltage determines the device's conductivity. MOSFETs were invented to overcome the drawbacks of FETs, such as high drain resistance, medium input impedance, and slow operation.

In a MOSFET, the isolation between the connection pole and the P-channel region means that current does not directly pass through. The voltage on the connection pole affects the current in the N-channel region. When the voltage on the connection pole rises, the current in the N-channel region increases, and the current flows from the source to the drain.

BMS distinguishes between charging and discharging MOSFETs in a car. There are two working modes: discharge and charge, where charging is further divided into fast charging and slow charging. The way to determine the working mode is which 24V power supply is supplied to the BMS. T15/fast charging/slow charging is allowed to apply high voltage only after self-test passes, i.e., closing the corresponding relay.

BMS detects pre-charge current through internal resistance, which is divided into two types: direct current internal resistance, generally discharged/charged with a constant current for 10S/30S, etc., and then calculated by dividing the voltage change by the current value to obtain the direct current internal resistance value.

A lithium battery protection board consists of 3 MOS tubes, which are used for current and power calibration. The lithium battery protection board protects the series-connected lithium battery pack during charging to ensure that the voltage difference between each single battery is less than the set value (generally ±20mV), achieving balanced charging of each single battery in the battery pack and effectively improving the charging effect under series charging mode.

For such a critical circuit design in the battery management system, it is important to choose a stable and high-quality MOSFET to replace models such as VBA1210 and VB1330, which can improve the stability of portable electronic products.

VBsemi's MOS products can be widely used in lithium battery protection boards, DC-DC conversion circuits in computers, servers, and all-optical networks, and battery management products for portable devices.

Products Packaging

VBsemi's products include SOT23, DFN, SOT-89, SOP-8, TO-92, TO-251, TO-252, TO-220, TO-220F, TO-263, TO-247, SOT-223, TO3P, TO262, SOT669, TSSOP8, SC70, DIP8, SC75, SOT725 and other series packaging products, which can meet the needs of various users.

Application Fields

VBsemi's products are widely used in the automotive field: electronic control, battery management, vehicle inverters, vehicle electronic products, charging piles, etc.; communication field: various power supplies, switches, etc.; industrial field: inverters, frequency converters, electric tools, etc.; home appliance field: fans, washing machines, sweeping robots, refrigerators, air conditioners, etc.; consumer electronics field: lighting lamps, medical equipment, wireless charging, mobile power supplies, etc., and the product quality has always been at the top level in the industry.