Basic knowledge and application of diode — SUNMATE
Basic knowledge and application of diode
Main parameters of diode: forward current Forward pressure drop Reverse breakdown voltage Reverse leakage current Junction capacitance, etc.
Main characteristics of diode: forward conduction and reverse cut-off.
The main function of diode: rectification Voltage stabilization Freewheeling Amplitude check Switch Luminescence, etc.
Diode classification:
1. According to the installation method, there are patch and plug-in. The difference is: a. the patch diode can be pasted on the PCB by the patch machine or manually welded on the PCB by soldering iron. The type of patch varies according to the current, and the packaging size varies, such as ll34 LL41. SOD123 SOD323 SOD523. DO-213AA. DO214-AC.SMA. SOT23, etc., B. the plug-in diode is either manually welded or inserted on the circuit board first, and then fixed on the PCB through wave soldering. The size of the plug-in varies according to the current, such as DO-35 DO-41. TO-220, etc. from the design point of view, if the space and function meet the premise, the patch components are preferred to reduce the product cost.
2. Type of diode: A. working in the forward conduction state, such as ordinary rectifier diode Ultrafast recovery diode Schottky diode. LED, B. working in reverse breakdown state, such as zener diode TVs tube (transient suppression diode), etc.
3. Selection of diode: A. due to low response speed, ordinary rectifier diode can make a large current flow and a large reverse voltage. It is generally suitable for rectifier circuits with low frequency, large current and high voltage (50Hz / 60Hz). B. Ultrafast recovery diode due to its fast reaction speed The current is high The reverse voltage is large, which is mostly used in high voltage and high frequency High current rectifier circuit. C. Schottky diode, low power consumption Fast The current is high The reverse withstand voltage is slightly lower, which is mostly used in the output rectifier and freewheeling circuit of switching power supply. D. The voltage stabilizing tube is used to stabilize a certain point voltage, while TVs is mainly used as circuit instantaneous impact protection, with fast response speed and strong bearing capacity.
4. Diode selection: mainly according to circuit characteristics, such as voltage Frequency electric current. Select the appropriate components according to the working environment.
5. Diode measurement: the multimeter only makes a simple good and bad measurement: for example, when the multimeter is turned to the diode measurement gear, use the meter to contact both ends of the diode respectively. When the meter is connected in the forward direction, it will display a value, but there is no value in the reverse connection. If you want to test specific parameters, you have to use special instruments, which is not available in many companies, Therefore, we should choose brands and high-quality suppliers when selecting models.