Method and apparatus to limit maximum switch current in a switch of a switching power supply
First Claim
1. A switching regulator circuit, comprising:
- a switch to be coupled to an energy transfer element;
a controller coupled to the switch to control switching of the switch to regulate an output of a power supply in response to a feedback signal;
a current sensor included in the controller and including first and second comparators coupled to compare a current in the switch with first and second current limits, respectively, the controller to open the switch for a remainder of a current switching cycle of the switch until a next switching cycle of the switch if the current in the switch is greater than the first current limit, wherein the first and second comparators are coupled to compare the current in the switch with their respective current limits independent of the feedback signal; and
a frequency adjuster included in the controller and coupled to the second comparator, the frequency adjuster to adjust an oscillating frequency of an oscillator included in the controller, wherein the frequency adjustor is coupled to adjust the oscillating frequency by delaying the next switching cycle of the switch by a first amount of time if the current in the switch is greater than the second current limit and by delaying the next switching cycle of the switch by a second amount of time if the current in the switch is greater than the second current limit for a second consecutive switching cycle, wherein the second amount of time is different than the first amount of time.
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Abstract
Techniques are disclosed to limit the current in a switch of a switching power supply. An example switching regulator circuit includes a switch to be coupled to an energy transfer element. A controller is coupled to the switch to control switching of the switch. A current sensor is included in the controller. The current sensor includes first and second comparators coupled to compare a current in the switch with first and second current limits, respectively. The controller is to open the switch for a remainder of a current switching cycle of the switch until a next switching cycle of the switch in response to the first or second comparators. A frequency adjuster is also included in the controller and coupled to the second comparator. The frequency adjuster is to adjust an oscillating frequency of an oscillator included in the controller in response to the second comparator.
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Citations
23 Claims
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1. A switching regulator circuit, comprising:
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a switch to be coupled to an energy transfer element; a controller coupled to the switch to control switching of the switch to regulate an output of a power supply in response to a feedback signal; a current sensor included in the controller and including first and second comparators coupled to compare a current in the switch with first and second current limits, respectively, the controller to open the switch for a remainder of a current switching cycle of the switch until a next switching cycle of the switch if the current in the switch is greater than the first current limit, wherein the first and second comparators are coupled to compare the current in the switch with their respective current limits independent of the feedback signal; and a frequency adjuster included in the controller and coupled to the second comparator, the frequency adjuster to adjust an oscillating frequency of an oscillator included in the controller, wherein the frequency adjustor is coupled to adjust the oscillating frequency by delaying the next switching cycle of the switch by a first amount of time if the current in the switch is greater than the second current limit and by delaying the next switching cycle of the switch by a second amount of time if the current in the switch is greater than the second current limit for a second consecutive switching cycle, wherein the second amount of time is different than the first amount of time. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for regulating a transfer of energy, comprising:
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switching a switch coupled to an energy transfer element to regulate a transfer of energy through the energy transfer element in response to a feedback signal; comparing a current in the switch with a first current limit independent of the feedback signal; comparing the current in the switch with a second current limit independent of the feedback signal; opening the switch for a remainder of a current switching cycle of the switch until a next switching cycle of the switch if the current in the switch is greater than the first or second current limit; delaying the next switching cycle of the switch by a first amount of time if the current in the switch is greater than the second current limit; and delaying the next switching cycle of the switch by a second amount of time if the current in the switch is greater than the second current limit for a second consecutive switching cycle, wherein the second amount of time is different than the first amount of time. - View Dependent Claims (11, 12, 13, 14, 15)
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16. A power supply, comprising:
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an energy transfer element coupled between an input and an output of the power supply; a switch coupled to the input of the energy transfer element to regulate a transfer of energy from the input of the power supply to the output of the power supply in response to a feedback signal; a controller coupled to the switch to control switching of the switch; a current sensor included in the controller and including first and second comparators coupled to compare a current in the switch with first and second current limits, respectively, the controller to open the switch for a remainder of a current switching cycle of the switch until a next switching cycle of the switch if the current in the switch is greater than the first current limit, wherein the first and second comparators are coupled to compare the current in the switch with their respective current limits independent of the feedback signal; and a frequency adjuster included in the controller and coupled to the second comparator, the frequency adjuster to adjust an oscillating frequency of an oscillator included in the controller, wherein the frequency adjustor is coupled to adjust the oscillating frequency by delaying the next switching cycle of the switch by a first amount of time if the current in the switch is greater than the second current limit and by delaying the next switching cycle of the switch by a second amount of time if the current in the switch is greater than the second current limit for a second consecutive switching cycle, wherein the second amount of time is different than the first amount of time. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23)
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Specification