Current limiting technique for a switching power converter
AssigneeChampion Microelectronic Corp.
InventorJeffrey H. Hwang
Life of this patent
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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.
Claims50
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.
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 by duty cycle limiter that is triggered when the output current exceeds a predetermined level.
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.
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 and wherein the capacitor is charged by constant current source and discharged in response to the duty cycle limiter being triggered.
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;
- a current sensor for sensing a current that is representative of an output current provided to the load;
- 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.
Dependencies are inferred from the claim text.