Performance changes of optocouplers at high temperatures

The performance of optocouplers (optocouplers) may be significantly affected in high-temperature environments, mainly reflected in the following aspects:
1. Changes in feedback characteristics
The feedback characteristics of optocouplers will change with the increase of usage time and ambient temperature, which will affect the output characteristics of the entire driver, leading to a decrease in its reliability and working life. This change is mainly due to the unstable performance of the optical and electrical components inside the optocoupler at high temperatures.
2. Decreased transmission ratio
In high temperature environments, the current transfer ratio (CTR) of optocouplers will significantly decrease. For example, there are cases showing that under high temperature conditions, the transmission ratio of optocouplers may decrease from 200-400% at room temperature to around 40%. This will weaken the signal transmission capability of the optocoupler, affecting communication quality and system stability.
3. Decreased output current capability
The output current capability of optocouplers at high temperatures will also be affected. Excessive output current may cause the optocoupler to heat up or even damage. Therefore, in high-temperature environments, it is necessary to ensure that the output current of the optocoupler is within its safe range and leave sufficient margin.
4. Extended response time
High temperature may also prolong the response time of optocouplers, affecting their performance in high-speed signal transmission. Response time refers to the time required for an optocoupler to change from the input signal to the corresponding output signal, which is particularly important in high-speed applications.
5. Heat dissipation performance and stability issues
The heat dissipation performance and stability of optocouplers in high-temperature environments are also key issues. If the heat dissipation is poor and the internal temperature of the optocoupler continues to rise, it will further exacerbate the above performance problem 3.
Improvement measures
The following measures can be taken to improve the performance changes of optocouplers at high temperatures:
Adjusting the driving resistor: Properly adjusting the driving resistor of the optocoupler, such as changing the original 2.7k driving resistor to 1.8k, can improve the performance of the optocoupler at high temperatures.
Using optocouplers with temperature compensation function: Choosing optocouplers with temperature compensation function can reduce the impact of temperature changes on performance to a certain extent.
Choose optocouplers with good high-temperature resistance: Optocouplers that work in high-temperature environments need to have good high-temperature resistance to ensure long-term stable operation.
Improved heat dissipation design: Optimize the heat dissipation design of the optocoupler, such as adding heat sinks or using thermal conductive materials, to improve the heat dissipation efficiency of the optocoupler and reduce its operating temperature