System and method for active electromagnetic interference reduction for a switching converter

An electronic device, comprising:

• first and second power switches having current terminals coupled in series between a first node and a reference node and coupled together at a phase node;
• an input inductance coupled between an input node for providing an input voltage and said first node;
• a third power switch having current terminals coupled between said first node and a second node;
• a capacitance coupled between said second node and said reference node;
• and
• a controller which provides control signals to switch on and off said first, second and third power switches based on a pulse control signal toggling between first and second states based on pulse-width control, wherein said controller operates to:
• turn on said first power switch after said pulse control signal switches to said second state, and to turn off said first power switch after said pulse control signal switches to said first state;
• turn on said second power switch after said first power switch is turned off and to turn off said second power switch approximately when the voltage on said phase node goes positive while said first power switch is on;
• and
• turn on said third power switch after said second power switch is turned off and to turn off said third power switch after said first power switch is turned off.

A method of operating a controller of a converter, wherein the converter comprises a first inductance coupled between an input voltage node and a first node, a first power switch having current terminals coupled between the first node and a second node, a second inductance coupled between the second node and an output node providing an output voltage, a second power switch having current terminals coupled between the second node and a reference node, a third power switch having current terminals coupled between the first node and a third node, a capacitance coupled between the third node and the reference node, and an error amplifier and comparator network which senses the output voltage and develops a pulse control signal which switches between first and second states during successive power cycles of the converter, said method comprising:

• controlling the first power switch by turning on the first power switch after the pulse control signal switches to the second state, and by turning off the first switch after the pulse control signal switches to the first state;
• controlling the second power switch by turning on the second power switch after the first power switch is turned off, and by turning off the second power switch after the first power switch is turned on approximately when the voltage of the second node goes positive;
• and
• controlling the third power switch by turning on the third power switch after the second power switch is turned off, and by turning off the third power switch after the first power switch is turned off.