Methods and circuits for programmable current limit protection
First Claim
Patent Images
1. A current limit circuit for protecting a power converter, the current limit circuit coupled to (1) an inductor through which inductor current flows, the inductor current having instantaneous and average inductor current values;
- (2) a switch having at least one switch element and a duty cycle; and
(3) a filtering component having an adjustable filtered signal, the current limit circuit comprising;
a steady-state current limit circuit that reduces average inductor current value to a steady-state threshold during a transient phase and regulates average inductor current value approximately at the steady-state threshold responsive to an over-current condition; and
a cycle-by-cycle current limit circuit that commands reduction of instantaneous inductor current value after the instantaneous inductor current value equals or exceeds a maximum instantaneous threshold during the transient phase.
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Accused Products
Abstract
The present invention provides methods and circuits for protecting power converters from over-current conditions that, in one embodiment, (1) reduce average inductor current to a steady-state threshold during a transient phase and regulate average inductor current in steady-state regulation approximately at the steady-state threshold; and (2) reduce instantaneous inductor current after the instantaneous inductor current exceeds a maximum instantaneous threshold during the transient phase.
163 Citations
42 Claims
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1. A current limit circuit for protecting a power converter, the current limit circuit coupled to (1) an inductor through which inductor current flows, the inductor current having instantaneous and average inductor current values;
- (2) a switch having at least one switch element and a duty cycle; and
(3) a filtering component having an adjustable filtered signal, the current limit circuit comprising;a steady-state current limit circuit that reduces average inductor current value to a steady-state threshold during a transient phase and regulates average inductor current value approximately at the steady-state threshold responsive to an over-current condition; and a cycle-by-cycle current limit circuit that commands reduction of instantaneous inductor current value after the instantaneous inductor current value equals or exceeds a maximum instantaneous threshold during the transient phase. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
- (2) a switch having at least one switch element and a duty cycle; and
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18. A current limit circuit for protecting a power converter that delivers output current to a load, the current limit circuit coupled to (1) an inductor through which inductor current flows, the inductor current having instantaneous and average inductor current values;
- (2) a switch having at least one switch element and a duty cycle; and
(3) a filtering component having an adjustable filtered signal, the current limit circuit comprising;a steady-state current limit circuit that reduces output current to a steady-state threshold during a transient phase and regulates output current approximately at the steady-state threshold responsive to an over-current condition; and a cycle-by-cycle current limit circuit that commands reduction of instantaneous inductor current value after the instantaneous inductor current value equals or exceeds a maximum instantaneous threshold during the transient phase.
- (2) a switch having at least one switch element and a duty cycle; and
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19. A current limit circuit for protecting a power converter, the current limit circuit coupled to (1) an inductor through which inductor current flows, the inductor current having instantaneous and average inductor current values;
- (2) a switch having at least one switch element and a duty cycle; and
(3) a filtering component having an adjustable filtered signal, the current limit circuit comprising;an amplifier that generates a control signal that commands reduction of average inductor current value to a steady-state threshold during a transient phase and regulation of average inductor current value approximately at the steady-state threshold responsive to an over-current condition; and a cycle-by-cycle comparator that commands reduction of instantaneous inductor current value after the instantaneous inductor current value equals or exceeds a maximum instantaneous threshold during the transient phase.
- (2) a switch having at least one switch element and a duty cycle; and
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20. A current limit circuit for protecting a power converter, the current limit circuit coupled to (1) an inductor through which inductor current flows, the inductor current having instantaneous and average inductor current values, and (2) a switch having at least one switch element and a duty cycle, the current limit circuit comprising:
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a filtering component having an adjustable filtered signal; an amplifier that adjusts the stored energy during an adjustment period responsive to average inductor current value being greater than a steady-state threshold; and a cycle-by-cycle comparator that commands reduction of instantaneous inductor current value after the instantaneous inductor current value equals or exceeds a maximum instantaneous threshold during at least part of the adjustment period.
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21. A power converter comprising:
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an inductor through which instantaneous inductor current flows; a switch having at least first and second active switch elements, the first active switch element configured to be turned ON to conduct increasing instantaneous inductor current, the second active switch element configured to be turned ON to conduct decreasing instantaneous inductor current; and a comparator coupled to the second active switch element to sense a signal indicative of instantaneous inductor current during at least a portion of the time the second active switch element is ON, the comparator configured to command the second active switch element to be kept ON for a duration after instantaneous inductor current exceeds a maximum instantaneous threshold, the duration being a function of a period of time in which instantaneous inductor current compares in a predetermined manner to a minimum instantaneous threshold. - View Dependent Claims (22, 23)
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24. A method for limiting current in a power converter, the power converter having (1) an inductor through which inductor current flows, the inductor current having instantaneous and average inductor current values;
- (2) a filtering component having an adjustable filtered signal; and
(3) a switch having at least one switch element and a duty cycle, the method comprising;reducing average inductor current value to a steady-state threshold during a transient phase responsive to an over-current condition; regulating average inductor current value approximately at the steady-state threshold; and reducing instantaneous inductor current value after the instantaneous inductor current value equals or exceeds a maximum instantaneous threshold during the transient phase. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37)
- (2) a filtering component having an adjustable filtered signal; and
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38. A method for limiting current in a power converter that delivers output current to a load, the power converter having (1) an inductor through which inductor current flows, the inductor current having instantaneous and average inductor current values;
- (2) a filtering component having an adjustable filtered signal; and
(3) a switch having at least one switch element and a duty cycle, the method comprising;reducing output current to a steady-state threshold during a transient phase responsive to an over-current condition; regulating output current approximately at the steady-state threshold; and reducing instantaneous inductor current value after the instantaneous inductor current value equals or exceeds a maximum instantaneous threshold during the transient phase.
- (2) a filtering component having an adjustable filtered signal; and
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39. A method for limiting current in a power converter, the power converter having (1) an inductor through which inductor current flows, the inductor current having instantaneous and average inductor current values;
- (2) a filtering component having an adjustable filtered signal; and
(3) a switch having at least one switch element and a duty cycle, the method comprising;providing the adjustable filtered signal; adjusting the adjustable filtered signal to reduce average inductor current value to a steady-state threshold during a transient phase responsive to an over-current condition; regulating the adjustable filtered signal approximately at a level indicative of the steady-state threshold to regulate average inductor current value approximately at the steady-state threshold; and reducing instantaneous inductor current value after the instantaneous inductor current value equals or exceeds a maximum instantaneous threshold during the transient phase.
- (2) a filtering component having an adjustable filtered signal; and
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40. A method for limiting current in a power converter, the power converter having (1) an inductor through which instantaneous inductor current flows;
- (2) a switch having at least first and second active switch elements, the first active switch element configured to be turned ON to conduct increasing instantaneous inductor current and the second active switch element configured to be turned ON to conduct decreasing inductor current; and
(3) a first comparator, the method comprising;sensing a signal indicative of instantaneous inductor current from the second active switch element during at least a portion of the time the second active switch element is ON; comparing instantaneous inductor current to a maximum instantaneous threshold; commanding the second active switch element to be kept ON for a duration after instantaneous inductor current exceeds the maximum instantaneous threshold; and comparing instantaneous inductor current to a minimum instantaneous threshold in a predetermined manner for a period of time, the duration being a function of the period of time. - View Dependent Claims (41, 42)
- (2) a switch having at least first and second active switch elements, the first active switch element configured to be turned ON to conduct increasing instantaneous inductor current and the second active switch element configured to be turned ON to conduct decreasing inductor current; and
Specification