What is the working principle and effect of transient suppression diodes

What is the working principle and effect of transient suppression diodes

Engineers who design electronic product circuits know that transient suppression diodes are a very commonly used surge suppression component, which is generally used in the maintenance of secondary power supplies and signal circuits.

The working principle of transient suppression diodes:

The equipment is connected in parallel with the circuit. When the circuit is in normal operation, it is in the cut-off state (High impedance), which does not affect the normal operation of the line. When the circuit has abnormal overvoltage and reaches its breakdown voltage, it quickly changes from the High impedance to the low resistance state, supplies the low impedance conduction path to the instantaneous current, clamps the abnormal high voltage together in a safe level, and then maintains the IC or circuit to be maintained; When the abnormal overvoltage disappears, it recovers to the high resistance state and the circuit operates normally.

The effect of transient suppression diode:

(1) Adding TVS diodes to the signal and power lines can prevent the failure of microprocessors or microcontrollers due to transient surges, such as electrostatic discharge effects, communication power surges, and switching power supply noise.

(2) The electrostatic discharge effect can release pulses exceeding 10000V and 60A, and can continue for 10ms; However, ordinary TTL equipment may be damaged when encountering 10V pulses exceeding 30ms. Using TVS diodes can effectively absorb pulses that can cause equipment damage and eliminate crosstalk caused by switches between buses.

(3) Placing the TVS diode between the signal line and ground can prevent unnecessary noise from affecting the data and control bus.

Transient suppression diode selection:

① When using transient suppression diodes TVS s, they are generally connected in parallel to the circuit being maintained. In order to limit the current flowing through the TVS  to not exceed the peak current IPP allowed by the , current limiting elements such as resistors, self-healing fuses, inductors, etc. should be connected in series on the line.

② Selection of breakdown voltage VBR: The breakdown voltage of TVS s should be selected based on the highest operating voltage UM of the line according to the formula: VBRmin ≥ 1.2 UM or VRWM ≥ 1.1 UM. Communication: UM=1.414Uac, for example, regarding 220V communication electricity, its UM=1.414 * 220=311 (V); DC