1.25 ~ 37V LM317 adjustable power supply configuration

The adjustable power supply circuitry operates within a voltage range of 1.25 to 37V. It utilizes a three-terminal regulator, which is known for its good performance and stability. The compact size of the design facilitates easy installation, and it can deliver a maximum output current of 1.5A with a continuously adjustable output voltage. This power supply is particularly suitable for experimental applications. A filtering capacitor (C3) is included to eliminate ripple and enhance the stability of the output voltage. In the event of a short circuit between the output terminal and the input of the LM317, capacitor C2 can discharge through the internal damage of the LM317 chip, while diode VD6 serves as a discharge path for C2. Capacitor C4 is implemented to prevent self-excitation at the output, and diode VD5 acts as a protective component to prevent damage from short-circuit conditions caused by capacitive load charging at the LM317 input. To ensure reliable operation of the LM317, a resistor (Rl) of typically 120Ω or 240Ω is used. The output voltage (Vo) can be expressed by the formula: Vo = 1.25V (1 + R2/Rp).

The adjustable power supply circuit described utilizes the LM317 voltage regulator, which is a popular choice for providing stable output voltages in various applications. The circuit is designed to allow users to adjust the output voltage within a specified range, making it versatile for different experimental setups.

The three-terminal design of the LM317 simplifies the integration of the regulator into various circuits, providing a straightforward means of adjusting voltage levels. The output voltage is determined by the resistors R2 and Rp, which form a voltage divider. The formula for output voltage indicates that by varying the resistance values, the output can be fine-tuned to meet specific requirements.

The inclusion of capacitors C3 and C4 plays a critical role in maintaining the stability of the power supply. C3 filters out any high-frequency noise or ripple that may be present in the output, ensuring a clean and stable voltage is delivered to the load. C4 prevents potential oscillations that could arise from feedback in the circuit, thus protecting the integrity of the output voltage.

Diodes VD5 and VD6 provide essential protection mechanisms for the LM317. VD5 safeguards against back-emf and voltage spikes that could occur during capacitive load discharges, while VD6 ensures that any excess charge from C2 is safely diverted, preventing damage to the LM317 regulator.

Overall, this adjustable power supply circuit is well-suited for experimental applications, offering a reliable and stable source of power with adjustable voltage levels and built-in protection features. Its compact design and ease of installation make it an excellent choice for various electronic projects.1.25 ~ 37V as shown for the adjustable power supply circuitry. It is adjustable three-terminal regulator typical application circuit, characterized by good performance, stable, small size, making installation easy, the maximum output current of l.5A, the output voltage between 1.25 ~ 37V continuously adjustable. It is best suited to experiment with power.FIG C3 for filtering out the ripple on the RP, improve the stability of power supply output voltage.

For some reason when the output terminal and the input of LM317 short, C2 will discharge through internal damage LM317 chip, VD6 provides for the discharge circuit C2. C4 is used to prevent the output of self-excitation. VD5 as protection diodes to prevent the accumulation of short-circuit on the input of the capacitive load charge to the LM317 discharge.

In order to ensure reliable operation LM317. Rl resistance and generally 120 (or 240 ). Expression of the output voltage Vo: Vo 1.25 (1 + R2/Rp) V.