TRR: The role of diodes in circuit protection

Basic characteristics of diodes
It is a semiconductor device with unidirectional conductivity, which only allows current to flow from the anode (positive electrode) to the cathode (negative electrode), and is almost non-conductive in the reverse direction. According to their materials and structures, they can be divided into ordinary diodes, Schottky diodes, Zener diodes, and fast recovery diodes.

Ordinary diode
Mainly used in rectifier circuits to convert alternating current into direct current. They have high forward pressure drop and slow reverse recovery time.

Schottky diode
It has low forward voltage drop and fast reverse recovery characteristics, suitable for high-frequency applications and low-voltage circuits.

Zener diode
It can stabilize the voltage under reverse breakdown voltage, so it is commonly used in voltage stabilization circuits.

Fast recovery diode
It has a shorter reverse recovery time and is suitable for circuits that require fast switching.

The role of diodes in circuit protection
Anti reverse connection protection
It is one of the most common applications of diodes in circuit protection. In electronic devices, if the power connection is reversed, it may cause damage to the device. By connecting a diode in series or parallel at the power input end, it can effectively prevent damage to the circuit caused by reverse power supply.

Application case:
In the charging circuit of mobile phones, a Schottky diode is usually connected in parallel at the power input terminal. When the power is connected in the correct direction, the diode does not conduct and the circuit works normally; When the power supply is connected in the wrong direction, the diode conducts, forming a short-circuit protection circuit to prevent damage to the circuit due to reverse power supply.

Overvoltage protection
It is a protective measure to prevent the voltage in the circuit from exceeding the design range. Zener diodes are commonly used in such applications. Zener diodes conduct under reverse breakdown voltage, which can limit excessive voltage within a safe range and protect subsequent circuits.

Application case:
In power adapters, to protect sensitive electronic components, a Zener diode is usually connected in parallel at the power output end. When the output voltage exceeds the breakdown voltage of the Zener diode, the Zener diode conducts, diverting the excess voltage and protecting the subsequent circuit from high voltage impact.

Overcurrent protection
It is a protective measure to prevent the current in the circuit from exceeding the safe range. Although fuses and thermistors are common overcurrent protection components, diodes can also be used for overcurrent protection in certain special applications.

Application case:
In some high-frequency switching power supplies, in order to prevent the transient high current generated by the inductance element during switching from damaging the circuit, a fast recovery diode is often connected in parallel at both ends of the inductance. When a transient high current is generated, the diode conducts, diverting the current and protecting the inductor and subsequent circuits.

Static protection
ESD is a common hazard in electronic devices that may cause permanent damage to sensitive electronic components. In order to prevent static electricity from damaging the circuit, static protection diodes are usually added to the circuit.

Application case:
In computer interface circuits, such as USB and HDMI interfaces, in order to prevent static electricity from entering the internal circuit through the interface, static protection diodes are usually connected in parallel at the interface ports. These diodes have fast response and low capacitance characteristics, which can effectively guide electrostatic currents to ground and protect internal circuits from electrostatic interference.

Specific application case analysis
Application of diodes in solar inverters
In solar inverters, diodes play an important protective role. Solar inverters convert the direct current generated by solar panels into alternating current for household or grid use. In order to improve the reliability and efficiency of the system, various diodes are used in the inverter for circuit protection.

Anti reverse protection: The output terminal of a solar panel is usually connected in series with a Schottky diode to prevent the panel from discharging in reverse at night or on cloudy days.

Overvoltage protection: In DC voltage regulation circuits, a Zener diode is used to clamp the voltage to prevent damage to subsequent circuits caused by excessive voltage.

Electrostatic protection: In the control circuit of the inverter, electrostatic protection diodes are used to protect the microcontroller and other sensitive components from damage caused by electrostatic discharge.

Application of diodes in electric vehicle charging stations
Electric vehicle charging stations are important supporting facilities for electric vehicles, and their safety and reliability are particularly important. Diodes also play an important role in the circuit protection of charging stations.

Anti reverse connection protection: At the power input end of the charging station, a high-voltage Schottky diode is used to prevent power reverse connection and protect the internal circuit of the charging station.

Overvoltage protection: In the charging module of the charging station, a Zener diode is used to clamp the voltage, preventing excessive voltage from causing damage to the charging module and the battery system of the electric vehicle.

Static electricity protection: Install static electricity protection diodes at the charging interface to prevent interference and damage to the charging station control circuit caused by static electricity generated by users when plugging and unplugging the charging gun.

 

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