First, the classification of diodes
â— Diodes can be divided into:
★ ordinary diodes and special diodes.
â—Ordinary diode:
★ Rectifier diodes, fast diodes, Zener diodes, detector diodes, switching diodes, etc.
â—Special diode:
★ Photodiode, varactor diode, tunnel diode, trigger diode, etc.
★ This article mainly introduces rectifier diodes, fast diodes and Zener diodes.
Second, the understanding of the specification
â—Rectifier diodes and fast diodes
★ Rectifier diode structure is mainly planar contact type, which is characterized by allowing relatively large current to pass, reverse breakdown voltage is relatively high, but PN junction capacitance is relatively large, and is generally widely used in circuits with low processing frequency. For example, a rectifier circuit, a clamp circuit, a protection circuit, and the like. The main considerations for rectifier diodes in use are that the maximum rectified current and the highest reverse operating voltage should be greater than the actual operating value.
★ The working principle of the fast diode is the same as that of the ordinary diode. However, since the reverse recovery time of the ordinary diode working in the switching state is long, generally greater than 500 nS, it cannot meet the requirements of the high frequency switching circuit. Fast diodes are mainly used in high-frequency rectifier circuits, high-frequency switching power supplies, high-frequency RC absorption circuits, inverter circuits, etc., and their reverse recovery time can reach 10nS. Fast diodes mainly include fast recovery diodes (FRD) and Schottky diodes (SBD for short).
★ The common specifications of rectifier diodes and fast diodes are as follows:
â— fast diode
★Fast recovery diode (FRD) is a kind of semiconductor diode with good switching characteristics and short reverse recovery time. It is mainly used in electronic circuits such as switching power supply, PWM pulse width modulator and inverter as high frequency rectification. Used as a diode, freewheeling diode or damper diode.
★ Fast recovery diodes are manufactured by gold doping, simple diffusion, etc., which can achieve higher switching speeds and higher pressure resistance. The internal structure of the fast recovery diode is different from that of a normal PN junction diode. It belongs to a PIN junction diode, which adds a base region I between the P-type silicon material and the N-type silicon material to form a PIN silicon wafer. Since the base region is thin and the reverse recovery charge is small, the reverse recovery diode has a short reverse recovery time, a low forward voltage drop, and a high reverse breakdown voltage (withstand voltage value).
★ Schottky diode, also known as Schottky barrier diode (SBD), is a diode based on the barrier layer formed by the contact of metal and semiconductor. Its main feature is that the forward voltage drop is small (about 0.45V), short reverse recovery time and low switching loss, is a low-power, ultra-high-speed semiconductor device widely used in switching power supplies, inverters, drivers and other circuits for high-frequency, low-voltage, high-current rectifier diodes, Freewheeling diodes, protection diodes, or rectifier diodes, small signal detection diodes used in circuits such as microwave communications.
★ Schottky diode is structurally different from PN junction diode. Its interior is made of anode metal (barrier layer made of molybdenum or aluminum), silicon dioxide (SiO2) electric field elimination material, N An epitaxial layer (arsenic material), an N-type silicon substrate, an N+ cathode layer, and a cathode metal. A Schottky barrier is formed between the N-type substrate and the anode metal. When a forward bias is applied to both ends of the barrier (anode metal is connected to the positive pole of the power supply, and the N-type substrate is connected to the negative pole of the power supply), the barrier layer is narrowed and the internal resistance is reduced; otherwise, the opposite ends of the barrier are added When biased, the barrier layer becomes wider and its internal resistance becomes larger.
â— Specifications of rectifier diodes and fast diodes
★ The volt-ampere characteristic curve of the rectifier diode and the fast diode is as follows.
â— Specifications of rectifier diodes and fast diodes
★1N4001～1N4007 as an example to introduce common specifications of diodes
★Maximum difference points: Trr, Irr and Qrr (reverse recovery charge)
â— Zener diode
★ Zener diode is a device made by the voltage regulation performance exhibited by the reverse breakdown characteristics of the PN junction. Zener diodes, also known as Zener diodes or reverse-breakdown diodes, act as a stabilizing voltage in the circuit. It is characterized by the fact that the reverse voltage does not change with the reverse current in a certain reverse current range after the diode is reversely broken down. Zener diodes are typically fabricated from silicon semiconductor materials by alloying or diffusion methods. It has both the unidirectional conduction characteristics of ordinary diodes and the reverse breakdown state. When the reverse voltage is low, the Zener diode is turned off; when the reverse voltage reaches a certain value, the reverse current suddenly increases, and the Zener diode enters the breakdown region, even if the reverse current changes over a wide range. The reverse voltage across the Zener diode can also remain essentially unchanged. However, if the reverse current increases to a certain value, the Zener diode will be completely broken down and damaged.
★ The volt-ampere characteristic curve of the Zener diode is as follows.
★General specifications of Zener diodes
★Specification specifications of Zener diode
★ Comparison of current characteristics of series Zener diodes
★ Zener diode temperature characteristics and Derating
Third, common parts packaging
â—Axial
â—SMD
â—TO
â—Bridge
Fourth, the application in switching power supply
â—Example 1
â—Example 2
New Arrival Linear LED Driver(Slim Driver)
Fahold has been specializing in LED Driver for 10 years. This new arrival linear led driver version, is combination of new market needs and fahold's powerful techniology.
This new version led linear drivers, has completely new function compare to fahold old one, it is much cost-effective, and adding Dali dimming; output current changeable by dip switch.
Dimming Linear Driver,Switching Power Supply, Linear LED Driver
ShenZhen Fahold Electronic Limited , https://www.fahold.net