Selection method and key considerations for optocoupler withstand voltage value

Definition and importance of optocoupler withstand voltage value
The voltage withstand value of an optocoupler refers to the external voltage strength that its output side optocoupler can withstand when the input is turned off. This parameter directly affects the anti-interference ability of the optocoupler against noise or sudden pulse changes. The higher the withstand voltage value, the stronger the anti-interference performance. In practical applications, due to differences in processes and raw materials, even mass-produced optocouplers may have slight differences in their voltage resistance indicators. Therefore, it is necessary to choose the appropriate voltage resistance level 1 based on specific scenarios.
Basis for selecting withstand voltage value
How to choose the optocoupler withstand voltage value?
1. Voltage requirements for application scenarios
AC load scenario: The thyristor optocoupler should pay special attention to VDRM (repetitive peak voltage), and should be selected based on the peak value of the AC load voltage to ensure that VDRM is 1.5-2 times higher than the actual working voltage to leave room for margin. For example, the peak voltage of a 220V AC circuit is about 311V, and it is recommended to choose a model with VDRM ≥ 400V.
Isolation protection scenario: In industrial equipment or high-voltage circuits, it is necessary to refer to the insulation withstand voltage parameters of optocouplers (such as 3750V of TLP1085M) to ensure compliance with system safety isolation requirements
2. Testing methods and quality control requirements
Traditional destructive testing methods, such as continuous voltage boosting, may result in overestimation of the withstand voltage value. However, the optimized gradient pulse testing method detects the critical voltage through instantaneous avalanche breakdown, which can accurately obtain the withstand voltage value without damaging the device. If the application requires high precision in withstand voltage (such as laboratory precision index control), it is necessary to choose optocouplers that support non-destructive testing and pay attention to the stability of their withstand voltage range
Steps and precautions for selection
Determine system voltage parameters
Calculate the peak value of the actual working voltage (such as converting AC voltage to effective value? √ 2), and reserve a safety margin of 20% -50%.
Match optocoupler type
Choose non-linear optocoupler (such as PC817) for switch power supply, linear optocoupler (such as TLP521) for analog signal transmission, and high-speed optocoupler (such as 6N135) for high-frequency scenarios.
Verify compatibility testing
If you need to accurately test the withstand voltage value in bulk, prioritize optocouplers that support gradient pulse testing method to avoid a decrease in yield due to destructive testing
Environmental adaptability considerations
Select models with temperature resistance of -40~125 ℃ (such as square crystal optocouplers) for high temperature environments (such as industrial furnaces), and pay attention to the product's moisture resistance for humid environments