Current limiting technique for a switching power converter
First Claim
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1. A switching power converter for providing a load with an output current and voltage, comprising:
- a switch for transferring energy from a source to the load by opening and closing the switch according to a duty cycle; and
a duty cycle limiter coupled to the switch wherein the duty cycle limiter is triggered when the output current exceeds a predetermined level, the duty cycle limiter including a capacitor having a charge that is gradually changed in response to the output current exceeding the predetermined level and wherein the duty cycle is related to a voltage on the capacitor.
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Abstract
An improved technique for limiting current in a switching power converter. The switching power converter includes a soft-start circuit which slowly increases a switching duty cycle upon power-up. Once the converter is operating normally, the duty cycle is controlled to regulate the output voltage. In the event an excessive output current is detected, soft-start circuit is controlled to reduce the switching duty cycle. More particularly, a soft-start capacitor may be discharged during portions of a clock period used to control switching.
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Citations
27 Claims
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1. A switching power converter for providing a load with an output current and voltage, comprising:
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a switch for transferring energy from a source to the load by opening and closing the switch according to a duty cycle; and
a duty cycle limiter coupled to the switch wherein the duty cycle limiter is triggered when the output current exceeds a predetermined level, the duty cycle limiter including a capacitor having a charge that is gradually changed in response to the output current exceeding the predetermined level and wherein the duty cycle is related to a voltage on the capacitor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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- 13. A switching power converter for providing a load with an output current and voltage comprising a switch for transferring energy from a source to the load by opening and closing the switch according to a duty cycle wherein when the output current reaches an excessive level, the duty cycle is limited to an amount that is related to a degree to which the output current is excessive.
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17. A switching power converter for providing a load with an output current and voltage, comprising
a switch for transferring energy from a source to the load by opening and closing the switch according to a duty cycle; - and
a duty cycle limiter coupled to the switch wherein the duty cycle limiter is triggered when the output current exceeds a predetermined level, the duty cycle limiter including a counter and wherein the duty cycle is related to a count of the counter. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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Specification