Method and apparatus for time-differential comparison of an analog signal
First Claim
1. A time-differential analog comparator, comprising:
- a variable frequency signal source coupled to provide a repeating signal having a plurality of periods, wherein each period has a frequency corresponding to a value of an analog input;
a counting circuit coupled to count the periods of the repeating signal, wherein the counting circuit is coupled to count in a first direction for a first time interval and coupled to count in a second direction opposite to the first direction for a second time interval that occurs after an end of the first time interval;
a timing circuit coupled to the counting circuit, wherein the first time interval and the second time interval are determined by the timing circuit, and wherein the timing circuit is further coupled to generate a mode select signal at a time between the first time interval and the second time interval to stimulate a change in the analog input; and
an evaluation circuit coupled to the counting circuit and the timing circuit, wherein the evaluation circuit is responsive to a count of the periods of the repeating signal after an end of the second time interval.
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Abstract
A time-differential analog comparator is disclosed. An example apparatus according to aspects of the present invention includes a source of a variable frequency signal having a frequency responsive to an analog input. A counting circuit is coupled to count cycles of the variable frequency signal. The counting circuit is coupled to count in a first direction for a first time interval and is coupled to count in a second direction opposite to the first direction for a second time interval that occurs after an end of the first time interval. An evaluation circuit is coupled to the counting circuit. The evaluation circuit is responsive to the count of the cycles of the variable frequency signal after an end of the second time interval.
8 Citations
24 Claims
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1. A time-differential analog comparator, comprising:
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a variable frequency signal source coupled to provide a repeating signal having a plurality of periods, wherein each period has a frequency corresponding to a value of an analog input; a counting circuit coupled to count the periods of the repeating signal, wherein the counting circuit is coupled to count in a first direction for a first time interval and coupled to count in a second direction opposite to the first direction for a second time interval that occurs after an end of the first time interval; a timing circuit coupled to the counting circuit, wherein the first time interval and the second time interval are determined by the timing circuit, and wherein the timing circuit is further coupled to generate a mode select signal at a time between the first time interval and the second time interval to stimulate a change in the analog input; and an evaluation circuit coupled to the counting circuit and the timing circuit, wherein the evaluation circuit is responsive to a count of the periods of the repeating signal after an end of the second time interval. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 21, 22, 23)
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9. A method of performing a time-differential comparison of an analog signal, comprising:
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generating a repeating signal having a plurality of periods, wherein each period has a frequency corresponding to a value of the analog signal; counting in a first direction during a first time interval in response to the periods of the repeating signal; generating a mode select signal at a time between the first time interval and a second time interval to stimulate a change in the analog signal; counting in a second direction during the second time interval in response to the periods of the repeating signal; and evaluating a count of the periods of the repeating signal after an end of the second time interval. - View Dependent Claims (10, 11, 12, 24)
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13. A time-differential analog comparator, comprising:
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a source of a variable frequency signal having a frequency corresponding to an analog input, wherein the analog input is an electrical signal representative of a temperature of a switched mode power supply; a counting circuit coupled to count cycles of the variable frequency signal, wherein the counting circuit is coupled to count in a first direction for a first time interval and coupled to count in a second direction opposite to the first direction for a second time interval that occurs after an end of the first time interval; a timing circuit coupled to generate a mode select signal to change a mode of the switched mode power supply to improve an efficiency of the switched mode power supply; and an evaluation circuit coupled to the counting circuit, wherein the evaluation circuit is responsive to the count of the cycles of the variable frequency signal after an end of the second time interval. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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Specification