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 representative of the output of the power converter 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; and
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.
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Abstract
A method for controlling a power converter switch includes operating the power converter switch in first, second, and third duty cycle control modes in response to a feedback signal representative of an output of the power converter. 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.
114 Citations
26 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 representative of the output of the power converter 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; and 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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. 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 representative of an output of the power converter and a signal representative of current through the switch to regulate power delivered to the output of the power converter. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26)
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Specification