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Engineers working on electronic product circuit design are aware that transient voltage suppression diodes are very commonly used components for surge suppression; they are typically employed to protect secondary power supplies and signal circuits. Operation principle of the surge suppression diode: The surge suppression device is connected in parallel with the circuit. When the circuit is operating normally, it remains in a cut-off state (high-impedance state), without affecting the normal operation of the circuit. When abnormal overvoltage occurs and reaches its breakdown voltage, it quickly changes from a high-impedance state to a low-impedance state, providing a low-impedance path for the surge current while simultaneously clamping the abnormal high voltage at a safe level, thereby protecting the protected IC or circuit. Once the abnormal overvoltage disappears, it returns to its high-impedance state, allowing the circuit to operate normally again. Effect of suppression on transient voltage suppression diodes: Suppression (1) Involves placing TVS diodes on the signal and power lines, which helps to prevent microprocessors or microcontrollers from failing due to sudden surges such as those caused by electrostatic discharge, spikes in AC power supplies, and noise from switching power supplies. Suppression suppression (2): The electrostatic discharge effect can generate pulses exceeding 10,000 V and 60 A, which can last for 10 ms; whereas ordinary TTL devices will be damaged when exposed to a 10 V pulse lasting more than 30 ms. By using TVS diodes, pulses that could cause equipment damage can be effectively absorbed, and the interference (crosstalk) caused by switches between buses can be eliminated. Suppression suppression (3): Placing a TVS diode between the signal line and ground prevents the data and control buses from being affected by unnecessary noise. Selection of suppressor transient voltage suppression diodes: For suppression purposes, ① TVS diodes are generally connected in parallel with the circuit that needs protection. To prevent the current flowing through the TVS diode from exceeding its allowable peak current IPP, a current-limiting element such as a resistor, a self-resetting fuse, or an inductor should be connected in series in the circuit. Selection of the breakdown voltage VBR for suppression②: The breakdown voltage of the TVS diode should be determined based on the highest operating voltage UM of the circuit, using the formula: VBRmin≥1.2 UM or VRWM ≥1.1 UM. Communication: UM=1.414Uac. For example, for a communication voltage of 220V, UM=1.414*220=311(V); for direct current: UM=Udc