Optocoupler high-temperature transmission ratio improvement technology

Optocoupler is a device that uses optical signals for electrical signal isolation and transmission, widely used in various electronic devices. In high-temperature environments, the performance of optocouplers may be affected, especially the current transfer ratio (CTR) may decrease. Here are several techniques to improve the transmission ratio of optocouplers at high temperatures:
1. Choose a high temperature resistant optocoupler
Firstly, optocouplers designed to withstand higher temperatures can be chosen. These optocouplers typically have better thermal management designs that can maintain stable performance at high temperatures. For example, some high-speed optocouplers such as 6N135/6N136, 6N137/6N138, etc., although mainly emphasizing high-speed performance, may also have good high-temperature stability.
2. Optimize circuit design
In circuit design, the transmission speed and stability of optocouplers can be optimized by adjusting the resistance of the load resistor. Reasonable load resistance can reduce signal attenuation and phase delay, and maintain good performance even at high temperatures. In addition, using complementary push-pull circuits can reduce transmission delay and signal distortion, and improve the frequency characteristics of optocouplers.
3. Add positive feedback circuit
Adding a positive feedback circuit to the photosensitive base of a phototransistor can significantly improve the switching speed of the optocoupler, thereby enhancing the transmission ratio. This method is particularly effective at high temperatures as it can compensate for the prolonged response time caused by temperature increases.
4. Reduce distributed capacitance
The distributed capacitance of optocouplers can affect their transmission speed and stability. Reducing distributed capacitance is particularly important at high temperatures, as larger distributed capacitance can lead to greater signal attenuation and phase delay. Measures such as using high impedance phototransistors and reducing the distance between LEDs and phototransistors can effectively reduce the distributed capacitance.
5. Improve the luminous efficiency of LED
The luminous efficiency of LED has a significant impact on the performance of optocouplers. At high temperatures, improving the luminous efficiency of LEDs can shorten response time and thus enhance transmission ratio. This can be achieved by selecting high-quality LEDs or increasing the driving current of the LED, but it is important to be careful not to exceed the rated current of the LED by 2.
6. Choose the appropriate packaging form
The packaging form of optocouplers can also affect their transmission speed and stability. The miniaturized and flattened packaging form can reduce the distributed capacitance and parasitic inductance of optocouplers, thereby improving their performance at high temperatures.
7. Temperature compensation technology
To cope with the impact of temperature changes on optocoupler performance, temperature compensation technology can be used. For example, adjusting the operating point of the transmitter through negative feedback control, or using a temperature sensor to monitor the ambient temperature and automatically adjust the gain of the receiver to maintain stable signal transmission performance