Frequency jittering control for varying the switching frequency of a power supply

A method for generating a switching frequency in a power conversion system, comprising:

• generating a primary current;
• cycling one or more secondary current sources to generate a secondary current which varies over time;
• and
• combining the secondary current with the primary current to be received at a control input of an oscillator for generating a switching frequency which is varied over time.

A method for generating a switching frequency in a power conversion system, comprising:

• generating a primary voltage;
• cycling one or more secondary voltage sources to generate a secondary voltage which varies over time;
• and
• combining the secondary voltage with the primary voltage to be received at a control input of a voltage-controlled oscillator for generating a switching frequency which is varied over time.

A frequency jittering circuit for varying a power supply switching frequency, comprising:

• an oscillator for generating a signal having a switching frequency, the oscillator having a control input for varying the switching frequency;
• and
• means coupled to the control input for varying the switching frequency, including:
• one or more current sources coupled to the control input;
• and
• a counter coupled to the output of the oscillator and to the one or more current sources.

A power supply having a transformer coupled to an input voltage, the transformer having a primary winding, the power supply comprising:

• an oscillator for generating a signal having a frequency, the oscillator having a control input for varying the frequency of the signal, the oscillator including:
• a primary current source coupled to the control input;
• a differential switch coupled to the primary current source;
• a capacitor coupled to the differential switch;
• and
• a comparator coupled to the differential switch;
• a digital to analog converter coupled to the control input, the digital to analog converter having one or more current sources, wherein the primary current source generates a current I and each of said one or more current sources generates a current lower that I;
• a counter coupled to the output of the oscillator and to the current sources of the digital to analog converter;
• and
• a power transistor coupled to the oscillator and to one terminal of the primary winding, the power transistor modulating its output in providing a regulated power supply output.

A power supply having a transformer coupled to an input voltage, the transformer having a primary winding, the power supply comprising:

• an oscillator for generating a signal having a frequency, the oscillator having a control input for varying the frequency of the signal, the oscillator including:
• a primary current source coupled to the control input;
• a differential switch coupled to the primary current source;
• a capacitor coupled to the differential switch;
• and
• a comparator coupled to the differential switch
• a circuit for varying the frequency, the circuit coupled to the control input, including:
• a capacitor;
• a current source adapted to charge and discharge the capacitor;
• one or more comparators coupled to the capacitor and coupled to the current source for alternatingly charging and discharging the capacitor;
• and
• a power transistor coupled to the oscillator and to one terminal of the primary winding, the power transistor modulating its output in providing a regulated power supply output.