LM317 High-Current Bench Power Supply

This high-current LM317 power supply, offers a universal solution for various applications requiring a reliable, and high-quality DC power source with significant current output. Potential uses include powering car subwoofers, battery chargers, and more.

The design prioritizes versatility while keeping the component count low, making it a cost-effective option for your high-current needs.

LM317-Based Adjustable Power Supply with High Current Option

This design offers a simple and effective adjustable voltage power supply using the LM317 IC. It boasts a maximum current output of up to 10 amps, making it suitable for various applications.

Fixed Voltage Output:

For a fixed voltage output a specific resistance value needs to be calculated for resistor R4.

This is achieved by setting R4 to zero ohms (fully counter-clockwise) with switch S3 in the open position.

Then adjust preset resistor R5 until the circuit outputs your desired voltage (e.g., 12 volts). In this configuration R5 sets the fixed voltage.

Variable Voltage Output:

For variable voltage output, rotate R4 clockwise and close switch S3. R5 is no longer needed, and can be removed from the circuit. The output voltage can now be adjusted solely by varying the resistance of R4

High Current Option (Position 1):

Setting the Single Pole Double Throw (SPDT) switch S2 to position 1 allows for the highest possible current output.

This is achieved by using both halves of transformer T1 to supply current to the filter stage, effectively doubling the overall current capacity.

But this configuration comes at the cost of a 50% reduction in the maximum output voltage. This trade-off is beneficial because, the power transistor experiences less voltage drop, leading to more efficient operation.

Standard Voltage Operation (Position 2):

Setting switch S2 to position 2,, prioritizes voltage output. In this mode the maximum voltage delivered will be close to the specifications of transformer T1 (which is a 24-volt center-tapped transformer in this example).

Protection Diodes:

Diodes D1 and D2, are included to safeguard the LM317 IC. They protect against potential damage caused by an inductive load at the output, whenever the power is switched off.