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Dual-Rail DC Power Supply Circuit Diagram: ±2.5V to ±15V
Description
This design was developed as an extension for the Adjustable Direct Current Power Supply, a highly regarded circuit previously featured on this website. This straightforward unit provides a dual-rail adjustable output spanning from ±2.5V to ±15Vdc, maintaining precise tracking of both the positive and negative output voltages while preserving the current limiting and protection features of the primary circuit. Given that the intention of such a dual-rail configuration is to power experimental or repair circuits, the maximum current delivered per rail was intentionally limited to approximately 500 - 600mA, thereby avoiding the utilization of costly power transistors and intricate circuitry.
Circuit Diagram:
Parts:
- R1 = 4.7K - 1/2W
- R2 = 4.7K - 1/2W
- C1 = 100nF - 63V
- C2 = 220µF - 25V
- C3 = 220µF - 25V
- C4 = 100nF - 63V
- C5 = 100nF - 63V
- Q1 = BD437
- Q2 = BD438
- IC1 = LM358
Notes:
- The circuit can be integrated into the existing Adjustable DC Power Supply metal enclosure.
- Q1 and Q2 must be affixed to heat sinks. Securing them to the metal casing (using insulating washers, for example) has generally proven successful.
- The complete ±15V output can only be achieved if the secondary winding of the supply Transformer used within the Adjustable DC Power Supply is rated at a minimum of 48V (center-tapped).
- When operating this circuit, adjust the Current-limit control (P1) of the Adjustable DC Power Supply to any value within the 50mA - 1A range, but not exceeding this value.
- The second operational amplifier (IC1B) contained within the LM358 chip was inactive, with its input pins connected to the negative supply and the output left open.
Operational Amplifiers
The LM358 is a versatile dual operational amplifier integrated circuit. It consists of two independent amplifier stages, each with complementary input characteristics. This allows for applications like differential amplification, instrumentation amplifiers, and precision circuits. The LM358 chip offers a robust solution for low-cost and general-purpose amplification needs, commonly utilized in instrumentation and hobbyist electronics. It typically operates from a single supply, simplifying circuit design and reducing component count. The chip’s operational characteristics contribute to the circuit's accuracy and stability.