Unmanned system and circuit protection
A UAV design, which emphasizes the UAV manufacturer must be considered in the electrical subsystem design circuit protection for its products to the problem, and for each application to discuss the most common circuit protection components.
Protection of battery and charging circuit
Obviously, the UAV needs an onboard battery to provide power. Compared with other rechargeable batteries, lithium ion polymer battery (LiPo) with its size and weight, high energy density and higher voltage, so the battery core number can reach less system power requirements, and thus become the most commonly used battery type uav. The self discharge rate of the battery is also lower than that of other types of batteries. Nevertheless, if the charging conditions or improper use, will still cause some damage to its performance, and even lead to more serious smoke and fire, etc..
Excessive discharge and overcharge these two conditions will bring problems for lithium-ion batteries. In the event of excessive discharge, if the battery voltage is reduced to about 1.5V, the anode will produce gas. When the voltage continues to fall below 1V, it will cause the current collector copper dissolution, resulting in serious consequences of internal short circuit. Therefore, in practical applications, the need to protect the IC voltage protection. When the battery over charge leads to voltage above 4.6V, it will produce gas and heat in the cathode.
Although the cylindrical lithium ion battery has internal overvoltage protection, can start the current interrupting device (CID) and internal positive temperature coefficient (PTC; heating device; increasing resistance) but not LiPo battery with CID and PTC, thus increasing the external overvoltage and overcurrent and overtemperature protection is particularly important.
At present, there are many kinds of protection elements for the over current and over temperature protection of the unmanned aerial vehicles, including the self recovery fuse with the accurate over temperature protection and the patch self recovery fuse.
GPS, receiver antenna and I/O port protection

As shown above, electrostatic discharge (ESD) is a global positioning system (GPS), receiver antenna and a variety of I/O ports, such as a variety of unmanned systems, a major concern.
When these regions form the electrical path of the high potential current, each of the access points amplified the potential and potential risk of damage. For example, the charging port is suitable for battery charging. Recommended for use as a true DC (DC) circuit for high capacitance suppressors. Since this circuit may also experience higher energy transients (lightning, system shock, EFT), it is recommended to use a multilayer variable resistor, since it can go beyond ESD protection. In addition, if the overcurrent event continues (battery or circuit failure, etc.), the fuse can be used to interrupt the overcurrent condition, thereby protecting the system.
Circuit designers can use a variety of ESD protection for antennas, including ESD suppressors and TVS diodes. Electrostatic suppressor ESD static diode, the use of polymer composites to suppress the rapid rise of ESD transients (described in IEC 61000-4- 2), and almost no increase in the circuit‘s capacitance. This can be used to enhance the protection of the integrated circuit chip, the most suitable for low capacitance to ensure the integrity of the data signal is of great significance for low-voltage, high-speed applications.
TVS (transient voltage suppressor) diodes are designed to protect electronic circuits from transient and overvoltage threats such as EFT and ESD. TVS diodes usually focus on the silicon avalanche elements that are selected for their fast response time (low clamping voltage), lower capacitance and leakage current. They can be used in either one way (Dan Ji) or bidirectional (bipolar) diode circuits. The important parameters to be considered when selecting TVS diodes include the reverse turn off voltage (VR), peak pulse current (IPP) and maximum clamping voltage (VCmax).
I/O port ESD protection
For flight control motors, ESD is also a major concern for flight controllers and electronic speed controller (ESC) I/O ports. The main consideration of the signal port is the data rate of the signal. As the data rate increases, it is also important to consider the capacitance of the selected suppressor. It is necessary to ensure that the integrity of the system will not be affected. For example, low speed circuits in this port should be protected with a high capacitance multilayer variable resistor or TVS diode array. In addition, circuit board designers will decide whether to use a separate MLV or multi wire diode, depending on the location of its choice to maintain the flexibility of the component (separate components) or to reduce the number of components (array products).
For the high data rate agreement, must use almost no capacitor suppressor, in order to make the system to send and receive signal quality under the premise of lossless data, provide far below the 1.0pF capacitance value, and at higher data rates under the operation of polymer ESD suppressor.