Switched mode power supply with dynamic frequency foldback

A switched mode power converter with frequency foldback, comprising:

• an inductive element having an input for receiving an input voltage, and an output for providing an output voltage;
• a switch having a first current electrode coupled to a terminal of said inductive element, a second current electrode coupled to a power supply terminal, and a control electrode for receiving a drive signal;
• a feedback circuit having an input coupled to said output of said inductive element, and an output for providing a feedback signal;
• and
• a switched mode power supply controller, comprising:
• a pulse width modulator responsive to a clock signal having an output coupled to said control electrode of said switch, wherein said pulse width modulator generates said drive signal with a pulse width that varies in response to said feedback signal;
• and
• a variable frequency oscillator having a first input for receiving said feedback signal, a control input for receiving a control signal defining a foldback starting frequency, a foldback ending frequency, a foldback starting voltage, and a foldback ending voltage, and an output for providing said clock signal having a variable frequency that varies over a range between said foldback starting frequency and said foldback ending frequency as said feedback signal varies between said foldback starting voltage and said foldback ending voltage, respectively,
• wherein said switched mode power converter programs at least one of said foldback starting frequency, said foldback ending frequency, said foldback starting voltage, and said foldback ending voltage through at least one terminal of said switched mode power supply controller.

A method for generating a drive signal for a switch in a switched mode power supply comprising:

• receiving a feedback signal that is representative of an output voltage;
• and
• generating a pulse width modulated signal in response to a clock signal and said feedback signal;
• receiving a programmable control signal for determining a foldback starting frequency, a foldback ending frequency, a foldback starting voltage, and a foldback ending voltage, said receiving comprising receiving at least one of said foldback starting frequency, said foldback ending frequency, said foldback starting voltage, and said foldback ending voltage from a user;
• and
• varying a frequency of said clock signal over a range between said foldback starting frequency and said foldback ending frequency as said feedback signal varies between said foldback starting voltage and said foldback ending voltage, respectively.