Method and apparatus for a control circuit with multiple operating modes
First Claim
1. A method for controlling a power converter switch to regulate power delivered to an output of a power converter, comprising:
- operating the power converter switch in a first duty cycle control mode in response to a feedback signal being between a first feedback signal value and a second feedback signal value, wherein said first duty cycle control mode includes modulating a peak switch current of the power converter switch in response to the feedback signal, and switching the power converter switch at a substantially fixed first switching frequency value;
operating the power converter switch in a second duty cycle control mode in response to the feedback signal being between the second feedback signal value and a third feedback signal value, wherein said second duty cycle control mode includes modulating the switching frequency in response to the feedback signal, and maintaining the peak switch current substantially at a peak switch current threshold value;
operating the power converter switch in a third duty cycle control mode in response to the feedback signal being between the third feedback signal value and a fourth feedback signal value, wherein said third duty cycle control mode includes modulating the peak switch current of the power converter switch in response to the feedback signal and switching the power converter switch at a substantially fixed second switching frequency value; and
transitioning from the first duty cycle control mode to the second duty cycle control mode in response to the peak switch current reaching the peak switch current threshold value.
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Abstract
A method for controlling a power converter switch to regulate power delivered to an output of a power converter includes operating the power converter switch in first, second, and third duty cycle control modes in response to a feedback signal. The first duty cycle control mode includes modulating a peak switch current of the power converter switch in response to the feedback signal, and switching the power converter switch at a substantially fixed first switching frequency value. The second duty cycle control mode includes modulating the switching frequency in response to the feedback signal, and maintaining the peak switch current substantially at a peak switch current threshold value. The third duty cycle control mode includes modulating the peak switch current of the power converter switch in response to the feedback signal, and switching the power converter switch at a substantially fixed second switching frequency value.
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Citations
23 Claims
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1. A method for controlling a power converter switch to regulate power delivered to an output of a power converter, comprising:
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operating the power converter switch in a first duty cycle control mode in response to a feedback signal being between a first feedback signal value and a second feedback signal value, wherein said first duty cycle control mode includes modulating a peak switch current of the power converter switch in response to the feedback signal, and switching the power converter switch at a substantially fixed first switching frequency value; operating the power converter switch in a second duty cycle control mode in response to the feedback signal being between the second feedback signal value and a third feedback signal value, wherein said second duty cycle control mode includes modulating the switching frequency in response to the feedback signal, and maintaining the peak switch current substantially at a peak switch current threshold value; operating the power converter switch in a third duty cycle control mode in response to the feedback signal being between the third feedback signal value and a fourth feedback signal value, wherein said third duty cycle control mode includes modulating the peak switch current of the power converter switch in response to the feedback signal and switching the power converter switch at a substantially fixed second switching frequency value; and transitioning from the first duty cycle control mode to the second duty cycle control mode in response to the peak switch current reaching the peak switch current threshold value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A controller for use in a power converter, the controller comprising:
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an oscillator to be coupled to a switch of the power converter to determine a time at which the switch is turned on at a beginning of a switching cycle of the switch, wherein the oscillator includes a capacitor, a charging current source coupled to charge the capacitor, and a discharging current source coupled to discharge the capacitor, wherein a time period for the capacitor to charge and discharge between first and second voltage levels is a time period of the switching cycle of the switch; a circuit coupled to the oscillator and coupled to capture an oscillator voltage across the capacitor at an end of the time at which the switch is turned on, wherein a value of the discharge current of the discharging current source is responsive to the captured oscillator voltage; and a logic circuit to be coupled to the switch to determine the end of the time at which the switch is turned on in response to a feedback signal of the power converter to regulate power delivered to an output of the power converter, wherein the controller includes first and second duty cycle control modes responsive to a magnitude of a feedback signal to regulate the power delivered to the output of the power converter, wherein during the first duty cycle control mode the oscillator is coupled to generate an output signal to switch the power converter switch at a substantially fixed first switching frequency value, and wherein during the second duty cycle control mode the oscillator is coupled to generate the output signal to vary the time period of the switching cycle of the switch, wherein the controller further includes a third duty cycle control mode responsive to the magnitude of the feedback signal to regulate the power delivered to the output of the power converter, wherein during the third duty cycle control mode the oscillator is coupled to generate the output signal to switch the power converter switch at a substantially fixed second switching frequency value, and wherein the controller is further coupled to transition from the first duty cycle control mode to the second duty cycle control mode in response to a peak switch current of the power converter reaching a peak switch current threshold value. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23)
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Specification