Dual Power Supply Module

Working

The Linear Dual Power Supply Module operates on the principle of linear voltage regulation. The input AC voltage, typically supplied by a 12-0-12 V transformer, undergoes rectification and filtering to produce a stable DC voltage. This voltage is then regulated using linear voltage regulators to provide a precise +5V and -5V output.

The current capacity of 1A ensures that the module can deliver sufficient power to your circuits, while the inclusion of an unregulated output adds versatility to accommodate projects that may benefit from a non-regulated power source.

Theory

Bridge Rectifier and Filter Circuit:

            The power supply module begins its operation with a bridge rectifier circuit. The 12-0-12 V AC input from the transformer is fed into the bridge rectifier, which converts the AC voltage into pulsating DC voltage. The bridge rectifier, typically composed of diodes arranged in a bridge configuration, ensures that the output remains positive regardless of the input polarity.

Diode specifications :

  • Junction Capacitance: 15pF
  • Power Dissipation: 1W
  • Reverse Recovery Time: 2.5µs
  • Forward Voltage: 1.1V
  • Forward Impulse Current: 27A
  • Reverse Voltage: 50 to 1000V
  • Operating Temperature: -65 to 150°C
  • Package: SMD plastic type, SMA-L
  • Mounting: Surface mount.

               Following rectification, the voltage undergoes filtration through a capacitor filter circuit. This circuit, consisting of capacitors, helps smooth out the pulsating DC waveform, reducing ripple and ensuring a more stable DC voltage.

Linear Voltage Regulators (LM7805 and LM7905):

            The filtered DC voltage is then directed to two linear voltage regulators: the LM7805 for the positive output (+5V) and the LM7905 for the negative output (-5V). Here’s how these regulators work:

1. LM7805 (Positive Regulator):
                  The LM7805 is a positive voltage regulator that maintains a constant output voltage of +5V. It achieves this by comparing the output voltage to a stable internal reference voltage. Any deviation from the desired +5V output results in an adjustment of the regulator to bring the output back to the specified voltage level.

  • Input Voltage Range: The LM7805 can accept an input voltage ranging from 7V to 25V
  • Output Voltage: The output voltage is a fixed +5V
     
  • Output Current: It can deliver an output current of up to 1.5A
     
  • Operating Temperature: The recommended operating temperature range is typically from 0°C to 125°C
     
  • Package Type: The LM7805 is available in various package types, including TO-220, SOT-223, and TO-263
     
  • Features: It includes internal thermal overload protection, high power-dissipation capability, internal short-circuit current limiting, and output transistor safe-area compensation
     

2. LM7905 (Negative Regulator):
                  The LM7905 is a negative voltage regulator that performs a similar function for the -5V output. It regulates the output voltage by comparing it to a fixed reference and adjusts the internal circuitry to maintain a steady -5V.

features:

  • Output Voltage: -5V
  • Input Voltage Range: 7V to 25V
  • Output Current: Up to 1.5A
  • Operating Temperature: Typically from 0°C to 125°C
  • Package Type: TO-220, TO-263, SOT-223
  • Features: Internal thermal overload protection, high power-dissipation capability, internal short-circuit current limiting, and output transistor safe-area compensation.

Current Limiting and Heat Dissipation:

          The linear regulators also provide a degree of current limiting. If the load attempts to draw more current than the regulators can supply, they will limit the output, preventing damage to the module.

Key features:

Voltage output options:

    • Regulated +ve 5V
    • Regulated -ve 5V
    • Unregulated output

Input voltage range:  6-0-6 to 15-0-15  

Recommend  : 12-0-12
Output Current : upto 3A
recommend : 2A

Benefits :

   Reliability:

    • High quantity
    • 3 step checking process

    Versatility:

    • Wide range of input voltages.

    Energy efficiency:

    • Less energy loss as heat.

    Easy integration:

    • Wide application

    Compact Design:

    • 65 x 30 x 36mm

    Ease of Use:

    • easy to operate and troubleshoot

    Longevity:

    • value for the long term use.

Applications

  • Electronics Prototyping
  • Laboratory Experiments
  • Audio Equipment
  • Robotics
  • DIY Projects
  • College projects
  • Automation