Electric bicycle is a common traffic work. Usually, electric bicycle uses battery as energy source, and is equipped with motor, controller, handlebar, brake handle and display instrument system on the basis of bicycle, which constitutes a mature control system. This article explains the discrete device products in electric bicycles.

The motor of electric bicycle is the power source of electric two-wheeled vehicle, which is usually installed near the rear wheel. DC brushless motor is commonly used, which has the characteristics of high efficiency, low noise and long life. Battery is an energy storage device, which is usually installed at the bottom of the frame. There are two kinds of batteries: lead-acid battery and lithium battery, among which lithium battery has higher energy density and longer life. The control system is responsible for controlling the operation of the motor and the running state of the vehicle, including controllers, sensors and discrete devices. The braking system is responsible for braking and slowing down when the vehicle is running, and usually includes brakes, brake pads and brake lines. There are also wheels, frames and tires, auxiliary components, etc.

The common BMS architecture of electric bicycle uses bottom-side series architecture, while the mainstream BMS architecture consists of main control, battery, secondary protection and analog front end. This is double protection by using AFE to control the on-off of MOS tube and secondary protection chip to control the three-terminal FUSE.

As a highly integrated and intelligent system, the electric drive system converts the electric energy in the battery into mechanical energy to drive the vehicle forward, and optimizes the performance and safety of the vehicle through various sensors and control systems. Usually, the traditional H6 bridge is used in the electric drive of most electric two-wheeled vehicles in the market, and the FOC control mode is the mainstream, which has the characteristics of small torque fluctuation, high efficiency, low noise and fast dynamic response.

Take the car's lighting system as an example. The backlight driving system of electric bicycle involves voltage conversion, voltage stabilization, LED driving and dimming, etc. It converts high voltage into low voltage, and the voltage stabilizer ensures the stability of the voltage provided to the backlight system to avoid the influence of voltage fluctuation on the backlight effect. The LED driving chip provides constant current or constant voltage driving for the LED backlight system, and the dimming circuit realizes the adjustment of backlight brightness. When the vehicle is powered on, the backlight driving circuit starts to work, converting the battery voltage into a low voltage suitable for the backlight system, and providing a stable current or voltage for the backlight system through the LED driving chip.

Taking the application of MOS tube as an example, its function in the controller of electric bicycle is switching and voltage regulation. Simply put, the motor is driven by the output current of MOS tube. The larger the output current is, the controller usually limits the current protection to prevent the MOS tube from being burnt by overcurrent, so that the motor torque is strong and the acceleration is powerful. Because the driving power of motor is generally more than 100 watts, MOS transistor driver and external MOSFET are widely used in the industry to improve the heat dissipation capacity. Because there is back electromotive force in the motor, this back electromotive force will be superimposed on the battery pack voltage and directly act on the MOSFET during deceleration, so a certain margin should be reserved for the withstand voltage of the MOSFET and the corresponding driver.

As a professional discrete device manufacturer with more than 30 years' experience, Heketai's discrete device models used in electric bicycles are as follows.