In a switching power supply, an optocoupler provides feedback on the output voltage to the preceding control circuit. A damaged optocoupler can cause abnormal output voltage and potentially cause the circuit to enter overvoltage or overcurrent protection, resulting in no voltage output. A switching power supply utilizes modern power electronics technology to control the on/off time ratio of a switching transistor to maintain a stable output voltage. Switching power supplies typically consist of a pulse-width modulation (PWM) control IC and a MOSFET.

A damaged optocoupler in a switching power supply can cause the power supply circuit to lose voltage regulation, and in severe cases, even cause the power supply to cease operation.

With the development and innovation of power electronics technology, switching power supply technology is also undergoing continuous innovation. Currently, switching power supplies are widely used in nearly all electronic devices due to their compact size, lightweight weight, and high efficiency. They are an indispensable power supply for the rapidly developing electronic information industry.

What role does an optocoupler play in a circuit?
Optocouplers are often found in circuits, generally serving as isolation devices. Today, we will discuss some of their characteristics and uses.
An optocoupler is a conversion device that converts electricity to light and back to electricity. This conversion isolates the front-end and back-end stages, providing protection.

To manufacture an optocoupler, a light-emitting diode (LED) and a phototransistor (PTD) are typically packaged together, with the LED serving as the input and the phototransistor as the output.
Commonly used circuits require electrical insulation to prevent high-voltage interference from the back-end circuit or weak current from the front-end, which could damage the stability of components within the circuit.
Drive circuits are also commonly used. A small current drives the LED, which then amplifies the weak light received by the phototransistor into a larger voltage signal to drive related devices.

To drive larger devices or higher voltages, optocouplers alone are insufficient; they often require further amplification with relays or other devices to control the high voltage.
The above are some common applications for optocouplers. They are also commonly used in some instruments and for level conversion. There are also several other applications that require further attention and summary.