Circuits

Power Supplies (5)

  • A transformer operating at 50Hz can be bulky and heavy;  Power Supply Unit (PSU) can be inefficient;  ripple needs large capacitors to filter
  • The switched mode power supply does this.  The mains drives an oscillator or chopper directly (not isolated) to generate a voltage at 50-200kHz.  This is then transformed to near required voltage by a much smaller, lighter transformer, (smaller core useable at higher frequency) rectified, smoothed by smaller value components
  • Efficient but Electrically noisy, can give EMC (ElectroMagnetic Compatability) problems due to switching/oscillator harmonics if not properly shielded