Power supply with active power buffer

An AC-DC converter comprising:

• a rectifier coupled to an AC input of the AC-DC converter;
• a flyback converter having an input coupled to the rectifier and an output coupled to an output of the AC-DC converter;
• an active power buffer coupled to the output of the AC-DC converter, the active power buffer further comprising:
• an energy storage capacitor;
• and
• one or more switching devices selectively coupling the energy storage capacitor to the output of the AC-DC converter so as to alternately store energy in and discharge energy from the energy storage capacitor;
• and
• control circuitry including:
• a flyback converter control loop that operates the flyback converter to regulate an average voltage across the energy storage capacitor of the active power buffer while providing unity power factor at the AC input of the AC-DC converter, the flyback converter control loop comprising a relatively slower control loop that controls the flyback converter during steady state load conditions and at least one relatively faster control loop that controls the flyback converter during transient load conditions;
• and
• an active power buffer control loop that operates the one or more switching devices of the active power buffer to regulate an output voltage of the AC-DC converter.