Adaptive multi-mode digital control improving light-load efficiency in switching power converters

A switch controller controlling on-times and off-times of a switch that electrically couples or decouples a load to or from a power source in a power converter, the controller comprising:

• digital logic generating a pulse signal for controlling on-times and off-times of the switch, the digital logic configured to:
• modulate the width of the pulse signal and maintain the frequency of the pulse signal at a first frequency responsive to the load exceeding a first load level;
• transition to modulating the frequency of the pulse signal and maintain the width of the pulse signal constant responsive to the load decreasing below the first load level but exceeding a second load level;
• and
• transition to modulating the width of the pulse signal and maintain the frequency of the pulse signal at a second frequency lower than the first frequency responsive to the load decreasing below the second load level but exceeding a third load level.

A method of controlling on-times and off-times of a switch by a pulse signal that electrically couples or decouples a load to or from a power source in a power converter, the method comprising:

• modulating a width of the pulse signal and maintain a frequency of the pulse signal at a first frequency responsive to the load exceeding a first load level;
• modulating the frequency of the pulse signal and maintaining the width of the pulse signal constant responsive to the load decreasing below the first load level but exceeding a second load level;
• and
• modulating the width of the pulse signal and maintaining the frequency of the pulse signal at a second frequency lower than the first frequency responsive to the load decreasing below the second load level but exceeding a third load level.