Adaptive rectifier architecture and method for switching regulators
First Claim
1. A control system for turning off a synchronous rectifier in an inductor-based power converter, comprising:
- a comparator having an input coupled to an inductor in the power converter to obtain an indication of substantially zero inductor current, and having an output coupled to the synchronous rectifier to switch off the synchronous rectifier to reduce or eliminate negative inductor current;
an adjustable compensation offset voltage source coupled to an input of the comparator;
a compensation offset voltage source controller operating only in a discontinuous or transition mode coupled to the output of the comparator and to the compensation offset voltage source and being operable to adjust an output value of the compensation offset voltage source for an offset voltage of the comparator and propagation delays in the control system by determining a timing relationship between a transition of the output of the comparator and the indication of substantially zero inductor current; and
an up/down counter provided as the compensation offset voltage source.
1 Assignment
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Accused Products
Abstract
An adjustable compensation offset voltage is applied to a comparator to vary turn-off timing of a synchronous rectifier. A comparator output indicates when current through an inductor coupled to the synchronous rectifier should be approaching zero. If the synchronous rectifier is turned off before the current through the inductor reaches zero, the compensation offset voltage is adjusted to delay the synchronous rectifier turn-off for the next switching cycle. If the synchronous rectifier is turned off after the current through the inductor reaches zero, the compensation offset voltage is adjusted to advance the synchronous rectifier turn-off for the next switching cycle. An up/down counter, in conjunction with a digital to analog converter, may be used to provide the adjustment to the compensation offset voltage. The adjustable compensation offset voltage improves the accuracy of synchronous rectifier turn-off in relation to a zero inductor current, thereby improving power converter efficiency.
36 Citations
19 Claims
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1. A control system for turning off a synchronous rectifier in an inductor-based power converter, comprising:
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a comparator having an input coupled to an inductor in the power converter to obtain an indication of substantially zero inductor current, and having an output coupled to the synchronous rectifier to switch off the synchronous rectifier to reduce or eliminate negative inductor current; an adjustable compensation offset voltage source coupled to an input of the comparator; a compensation offset voltage source controller operating only in a discontinuous or transition mode coupled to the output of the comparator and to the compensation offset voltage source and being operable to adjust an output value of the compensation offset voltage source for an offset voltage of the comparator and propagation delays in the control system by determining a timing relationship between a transition of the output of the comparator and the indication of substantially zero inductor current; and an up/down counter provided as the compensation offset voltage source. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for controlling a synchronous rectifier in an inductor-based power converter, the method comprising:
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turning the synchronous rectifier off in order to reduce or eliminate negative inductor current; obtaining an indication of substantially zero current in an inductor in the power converter; if the indication shows that the power converter is in discontinuous or transition mode, comparing the indication to a compensation offset voltage; and modifying the compensation offset voltage using an up/down counter for an offset voltage of the comparator and propagation delays in the control system by determining a synchronous rectifier turn-off timing in relation to a predetermined value of the indication. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15)
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16. A control system for turning off a synchronous rectifier in an inductor-based power converter, comprising:
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comparator means having an input coupled to an inductor in the power converter for obtaining an indication of substantially zero inductor current, and for determining a direction of inductor current by monitoring a switch node when the synchronous rectifier is turned off and having an output coupled to the synchronous rectifier to switch off the synchronous rectifier; an adjustable compensation offset voltage source coupled to an input of the comparator; a compensation offset voltage source controller operating only in a discontinuous or transition mode coupled to the output of the comparator means and to the compensation offset voltage source and being operable to adjust an output value of the compensation offset voltage source for an offset voltage of the comparator and propagation delays in the control system by determining a timing relationship between a transition of the output of the comparator and the indication of substantially zero inductor current; and an up/down counter provided as the compensation offset voltage source. - View Dependent Claims (17)
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18. A method for controlling a synchronous rectifier in an inductor-based power converter, the method comprising:
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turning the synchronous rectifier off; obtaining an indication of substantially zero current in an inductor in the power converter and a direction of current flow when the synchronous rectifier is turned off from comparator means; if the indication shows that the power converter is in discontinuous or transition mode, comparing the indication to a compensation offset voltage; and modifying the compensation offset voltage using an up/down counter for an offset voltage of the comparator and propagation delays in the control system by determining a synchronous rectifier turn-off timing in relation to a predetermined value of the indication. - View Dependent Claims (19)
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Specification