The process of converting a switching power supply to an adjustable voltage requires a certain level of electronic circuit knowledge and skills. Here is a simple step that can help you achieve this goal:

　　Understand the basic principle of switching power supply: Switching power supply regulates the output voltage by controlling the conduction and cutoff of switching elements (such as transistors or MOSFETs). It usually includes basic circuit components such as rectification, filtering, and voltage stabilization.

　　Design feedback loop: In order to achieve adjustable voltage, you need to add a feedback loop to monitor the output voltage and compare it with the set value. A common implementation is to use a comparator to compare the output voltage with an adjustable reference voltage.

　　Choose appropriate regulating components: In order to achieve adjustable voltage, you need to add an adjustable voltage source, such as an adjustable voltage regulator (such as LM317) or an adjustable switching power module. Ensure that the selected components can provide the required output voltage range and current capability.

　　Add regulating circuit: Connect the selected regulating component to the output terminal of the switching power supply, ensure correct connection of input and output voltages, and adjust its parameters as needed, such as output voltage and current limits.

　　Testing and debugging: Before connecting the power supply, be sure to carefully check whether the circuit connection is correct. After connection, gradually adjust the adjustable components, observe the changes in output voltage, and use appropriate testing instruments (such as oscilloscopes or multimeters) to verify the performance and stability of the circuit.

　　Optimization and improvement: Once the basic functions are implemented, you can consider optimizing and improving the circuit, such as adding overvoltage protection, overcurrent protection, or temperature protection, to improve the reliability of the circuit.

　　It should be noted that this is only a brief overview, and actual operation may vary depending on factors such as power supply type, required output range, and accuracy requirements. Before making any changes, please ensure that you have a thorough understanding of the relevant electronic circuit knowledge and operate with caution to avoid damaging the equipment or causing risks.

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