Is it urgent to need a light and convenient small fan in hot summer and hot weather? How does this hot-selling small product work and what electronic components it will use? In this issue, Hottech takes you to uncover the mystery of this explosive electronic product.

If you want to understand the small fan deeply, you must first understand its working principle, structure and electronic scheme. The working principle of the best-selling small fan in the market is that the motor drives the blades to rotate, and by accelerating and turning to the air, the air pressure is increased and the air circulation is realized. The small fan uses the power supply to charge the battery, and the battery supplies power to the motor. The speed of the motor is controlled by MCU, and the main control chip controls the speed of the fan through PWM signal to realize the control function of on-low-medium-high-off.

Small fans usually consist of blades, housings, shields, lithium batteries, USB charging cables (or charging bases), motors, circuit boards, etc. Take a customer's product as an example, it uses USB socket, diode, triode, patch resistor, patch capacitor, inductor, lithium battery protection IC, main control chip, switch, LED indicator, motor and other devices. The main board consists of main control circuit, rectifier circuit, lithium battery protection circuit and charging circuit.

The working voltage range of hand-held small fans is mostly between 3V and 6V, and different brands and models of hand-held small fans may be different. Small fans generally use DC motors, which provide electric energy through wires. After passing through the coils of electric rotors, the electric rotors rotate under the action of magnetic fields.

For example, in a customer's product, the working voltage is 4.3V, and in the charging management circuit, the rectification characteristics of Hottech M7 rectifier diode may be used to control the current direction. The main control circuit of the motor modulates the pulse width through the single chip microcomputer, which modulates the bias of the transistor base according to the corresponding load change, thus realizing the change of the transistor conduction time, thus realizing the change of the output of the switching regulated power supply. The S8050 triode product amplifies the signal in the circuit, drives the main control chip to realize the pulse modulation, and controls the speed of the electric fan.

Generally, there are protection chips where there are rechargeable lithium batteries. Among the commonly used small fans, Hottech can also provide lithium battery protection chips DW01 and HKT4056 to protect the battery from charging and discharging. It is also applied to MOS transistors such as SI2302 and AO3401.

Hand-held fan blades are relatively small, the overall volume is also small, and the noise requirements are very low, which requires suppliers' products to have low noise and small volume characteristics. Hottech's SMA and SOT-23 packaged secondary and tertiary tubes are small in size, easy to mount and low in noise, which is very suitable for small fan products.