Control for regulator fast transient response and low EMI noise

A method of controlling a conversion of power from an input source into a regulated output voltage at an output terminal, the method comprising:

• a) controlling an active switch to connect said input source to a filter network, said filter network having an inductor and a capacitor coupled to said output terminal, said active switch periodically operating between an on state and an off state over a switching period;
• b) comparing an output feedback signal based on said output voltage, a hysteresis signal, and a reference level, and providing a first control signal therefrom, wherein a duty cycle of said on state relative to said switching period is modulated based on said first control signal for regulating said output voltage;
• c) generating second control signal from said first control signal for controlling said duty cycle of said active switch;
• d) receiving said second control signal in a hysteresis programming circuit, and generating said hysteresis signal and a ramp control signal therefrom, said ramp control signal being coupled to said output feedback signal;
• and
• e) programming said hysteresis signal based on conditions at said input source and said output voltage to achieve a pseudo constant frequency operation.

An apparatus for controlling a conversion of power from an input source into a regulated output voltage at an output terminal, the apparatus comprising:

• a) means for controlling an active switch to connect said input source to a filter network, said filter network having an inductor and a capacitor coupled to said output terminal, said active switch periodically operating between an on state and an off state over a switching period;
• b) means for comparing an output feedback signal based on said output voltage, a hysteresis signal, and a reference level, and providing a first control signal therefrom, wherein a duty cycle of said on state relative to said switching period is modulated based on said first control signal for regulating said output voltage;
• c) means for generating second control signal from said first control signal for controlling said duty cycle of said active switch;
• d) means for receiving said second control signal in a hysteresis programming circuit, and generating said hysteresis signal and a ramp control signal therefrom, said ramp control signal being capacitively coupled to said output feedback signal;
• and
• e) means for programming said hysteresis signal based on conditions at said input source and said output voltage to achieve a pseudo constant frequency operation.