Abstract: With the increasingly widespread application of photovoltaic DC microgrids, end-side loads impose higher requirements on power supply stability and low ripple performance. This paper presents the design of a precision adjustable low-ripple linear DC power supply. The core regulating element of the power supply is the TIP142 Darlington transistor, while a closed-loop control system is constructed using the TL431 reference source and the LM324 operational amplifier, enabling continuously adjustable output in the range of 4–6 V with a rated current of 1 A. In addition, overvoltage, overcurrent, and overtemperature protection circuits are designed to safeguard the core circuitry. Key parameters are analyzed and calculated during the design process. Experimental results show that the proposed power supply features low ripple, high stability, and reliable protection performance, making it suitable for precision load power supply applications in DC microgrids.