What are the working principles of TVS diodes?

What are the working principles of TVS diodes?

A TVS diode is a semiconductor device used to protect electronic circuits from transient voltage shocks. It plays a critical role in the protection of the circuit, responding quickly to voltage surges and preventing damage to the sensitive components in the circuit

1. The basic structure and characteristics of TVS diodes

The basic structure of TVS diodes is similar to that of ordinary diodes, which are composed of P-N structures, but their design is more focused on suppressing voltage surges. It is capable of withstanding transient voltages of up to hundreds to thousands of volts in a very short period of time and disperses voltage surges by turning on large currents, protecting subsequent circuits from overvoltage damage.

TVS diodes have the following characteristics:

Fast response time: Typically at the picosecond level, voltage surges can be suppressed instantaneously.

High Power Handling Capability: Able to absorb extremely transient energy without damage.

Low leakage current: Under normal working voltage, the leakage current of the TVS diode is very small and will not affect the normal operation of the circuit.

Second, the working principle of TVS diode

The working principle of TVS diodes is mainly based on their response characteristics to transient voltages, which are divided into the following operating states:

Normal operating state: Within the normal operating voltage range, the TVS diode behaves in a high-impedance state and is almost non-conductive. At this time, the influence of the TVS diode on the circuit is negligible, and the circuit can work normally.

Transient voltage surge state: When there is a transient voltage surge in the circuit, such as lightning strike, power surge, or electrostatic discharge (ESD), etc., causing the voltage to exceed the breakdown voltage of the TVS diode, the TVS diode immediately enters the conduction state. At this point, the P-N junction breaks down rapidly, forming a low-impedance channel, and a large amount of current passes through the TVS diode, discharging transient energy to ground or power line, preventing the components in the subsequent circuit from being overvoltaged.

Recovery state: After the transient voltage disappears, the voltage drops below the breakdown voltage, and the TVS diode automatically returns to the high impedance state, stops conduction, and resumes normal operation. Due to the extremely short response time of the TVS diode, this process has little to no impact on the normal operation of the circuit.

3. Key parameters of TVS diode

When selecting and using TVS diodes, there are a few key parameters that design engineers must focus on:

Breakdown voltage (V_BR): This is the voltage at which the TVS diode starts to turn on. When the voltage in the circuit exceeds this value, the TVS diode will break down and protect the circuit.

Clamping Voltage (V_C): When the TVS diode is turned on, the device clamps the transient voltage around this value to ensure the safety of subsequent circuitry. The clamping voltage should be slightly higher than the normal operating voltage, but lower than the withstand voltage value of the components in the circuit.

Peak Pulse Current (I_PP): This is the maximum transient current that a TVS diode can withstand at a specified clamping voltage. The higher the value, the stronger the protection of the TVS diode.

Response time: Typically in the picosecond to nanosecond range, which is the time it takes for a TVS diode to move from a high-impedance state to a conduction state. The shorter the response time, the better the protection.

Fourth, the practical application of TVS diodes

TVS diodes are widely used in a variety of electronic devices that need to be protected against transient voltage surges, including:

Communication equipment: In telephone and network communication equipment, TVS diodes are used to protect interface circuits against transient shocks such as lightning strikes and electromagnetic interference (EMI).