Reasons for Unstable Output Voltage of Linear Adapters

　　Several factors contribute to the unstable output voltage of linear adapters. One primary cause is the degradation of filter capacitors. Over time, the electrolyte inside electrolytic capacitors can dry out, reducing their capacitance value. As a result, they are less effective at smoothing out the pulsating DC output from the rectifier stage. Instead of providing a steady DC voltage, the adapter outputs a fluctuating voltage with significant ripple, which can disrupt the normal operation of connected devices.

　　Another reason lies in the malfunction of the voltage regulation circuit. Linear adapters typically use a voltage regulator IC or a combination of discrete components to maintain a constant output voltage. If the voltage regulator IC is damaged due to overvoltage, overcurrent, or excessive heat, it fails to adjust the output voltage according to changes in the input voltage or load requirements. For example, when the load current increases, a faulty regulator may not be able to increase the output voltage accordingly, leading to a drop in voltage. Similarly, if the input voltage fluctuates, a non - functioning regulator cannot compensate, causing instability.

　　Inadequate heat dissipation can also affect the output voltage stability. When the adapter operates, components like the power transistor generate heat. If the heat sink is not properly attached or has accumulated dust, heat cannot be effectively dissipated. As the temperature of the components rises, their electrical characteristics change. For instance, the resistance of resistors may increase with temperature, altering the biasing of the voltage regulation circuit and resulting in unstable output voltage.

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