What is a rectifier diode?

A rectifier diode is an electronic component that utilizes the unidirectional conductivity of semiconductor materials to convert alternating current (AC) into direct current (DC). Its core function is to allow current to pass in one direction, thereby "rectifying" AC signals, and it is widely used in power circuits, battery chargers, motor drives, and other fields.
1、 Definition and core functions
The rectifier diode operates based on the unidirectional conductivity of the PN junction. When forward biased (with the P region connected to the positive electrode and the N region connected to the negative electrode), the PN junction conducts and current can pass through; When reverse biased, the PN junction is cut off and current can hardly pass through. Through this characteristic, rectifier diodes can respectively conduct and cut off the positive and negative cycles of AC power, thereby outputting pulsating DC power.
2、 Working principle
Forward bias: When the voltage in the P region is higher than that in the N region, the PN junction narrows, carriers diffuse to form a current, and the diode conducts.
Reverse bias: When the voltage in the N region is higher than that in the P region, the PN junction widens, carriers cannot diffuse, and the diode is turned off.
Rectification process: During the positive half cycle of AC power, the diode conducts and current passes through; In the negative half cycle, the diode is turned off and the current is blocked. By combining multiple diodes (such as bridge rectification), full wave rectification can be achieved to output smoother DC power.
3、 Key parameters
Maximum Reverse Voltage (VRRM): The maximum reverse voltage that a diode can withstand, exceeding which may cause breakdown.
Maximum Forward Current (IFM): The maximum forward current that a diode can continuously pass through, which is related to its packaging and heat dissipation capabilities.
Forward voltage drop (VF): The voltage drop during forward conduction, which affects power consumption and efficiency. The VF of silicon rectifier diodes is usually 0.6-1V.
Reverse recovery time (trr): The time required from reverse bias to complete cutoff, which affects the switching frequency. The TRR of high-speed rectifier diodes can be as low as tens of nanoseconds.
Surge current (IFSM): The maximum instantaneous current that a diode can withstand, which is related to its resistance to impact.
4、 Type and Characteristics
Silicon rectifier diode:
Features: High voltage resistance, high reliability, but slow switching speed (TRR about a few hundred nanoseconds).
Applications: power adapters, motor drivers.
Schottky rectifier diode:
Features: Low forward voltage drop (0.2-0.4V), ultra fast switching speed (trr<1ns), but low reverse withstand voltage.
Application: High frequency rectification, low dropout linear regulator (LDO).
Fast Recovery Rectifiers (FRDs):
Features: TRR ranges from tens of nanoseconds to hundreds of nanoseconds, balancing speed and voltage resistance.
Application: Switching power supply, inverter.
Ultra fast recovery rectifier diode (UFRD):
Features: TRR<50ns, suitable for high-frequency rectification.
Application: Communication equipment, high-frequency induction heating.
Silicon carbide (SiC) rectifier diode:
Features: High voltage resistance (up to several thousand volts), high switching speed, high temperature stability.
Applications: Electric vehicle charging stations, solar inverters.
5、 Application Fields
Power circuit: Convert AC power to DC power to supply power to electronic devices.
Battery charger: Control the charging current to prevent overcharging of the battery.
Motor drive: Provides DC power to the motor, controls speed and direction.
Communication equipment: Rectify in RF power supply to ensure signal stability.
Automotive electronics: Rectify in car chargers and LED lighting to improve efficiency.
6、 Development Trends
High speed: With the development of 5G and the Internet of Things, there is an increasing demand for ultrafast rectifier diodes with TRR<1ns.
Miniaturization: Adopting SOT-23, DFN and other packaging, the size is reduced to 1mm × 0.6mm, suitable for portable devices.
Integration: Integrating with power devices such as MOSFETs and IGBTs to form power modules and simplify circuit design.
Low power consumption: By optimizing materials such as SiC and GaN, the forward voltage drop and switching loss are reduced.
High temperature stability: Develop high-temperature resistant (>200 ℃) rectifier diodes to adapt to harsh environments.
7、 Typical application cases
1N4007: Universal silicon rectifier diode, VRRM=1000V，IFM=1A， Widely used in power adapters.
MBR10100: Schottky rectifier diode, VF=0.5V，trr=5ns， Suitable for high-frequency switching power supplies.
C3D10060: Silicon carbide rectifier diode, VRRM=600V，IFM=10A， Used for electric vehicle charging stations.
Rectifiers play a crucial role in electronic circuits due to their unique rectification characteristics. With the continuous advancement of technology, its performance will continue to improve and its application fields will further expand.