SLVAFU8 July   2024 TPSI2072-Q1 , TPSI2140-Q1 , TPSI3050 , TPSI3050-Q1 , TPSI3052 , TPSI3052-Q1 , TPSI3100 , TPSI3100-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2What Are Solid-State Relays?
    1. 2.1 History
      1. 2.1.1 Electromechanical Relays
      2. 2.1.2 Solid-State Relays
    2. 2.2 Isolation Technologies
      1. 2.2.1 Isolation Specifications
    3. 2.3 Relay Evolution
  6. 3Failure Mechanisms
    1. 3.1 Arcing in an Electromechanical Relay
    2. 3.2 Photo-degradation in Photo Relays
    3. 3.3 Partial Discharge
    4. 3.4 Time-Dependent Dielectric Breakdown in Capacitive and Inductive Isolation
  7. 4Electromechanical vs. Photo vs. Capacitive or Inductive
    1. 4.1 Electromechanical Relays
      1. 4.1.1 Advantages
        1. 4.1.1.1 No Leakage Current
      2. 4.1.2 Limitations
        1. 4.1.2.1 Switching Speed
        2. 4.1.2.2 Package Size
    2. 4.2 Photo or Optical Relays
      1. 4.2.1 Advantages
        1. 4.2.1.1 Lower EMI
      2. 4.2.2 Limitations
        1. 4.2.2.1 Limited Temperature Range
    3. 4.3 Capacitive or Inductive Based Relays
      1. 4.3.1 Advantages
        1. 4.3.1.1 Auxiliary Power
        2. 4.3.1.2 Bidirectional Communication
      2. 4.3.2 Limitations
        1. 4.3.2.1 EMI
    4. 4.4 Overall Comparison
  8. 5Summary
  9. 6References

3.2 Photo-degradation in Photo Relays

Photo relays experience failure due to potential complications with the internal LED. To elaborate, an LED is subject to light decay, which in the case of a photo relay is the reduction of light output capacity due to extreme conditions, such as over-temperature or over-current. As a result, the LED within a photo relay does not have enough luminosity to drive a gate voltage, which limits the switch functionality of the device.

Optical Relay LED Failure Block Diagram Figure 3-2 Optical Relay LED Failure Block Diagram