Phase-locked voltage-to-digital converter

Claim 2

A voltage conversion circuit comprising: a. first circuit means having an input responsive to a voltage for generating an output signal having a frequency that is a function of the voltage at its input, said output signal frequency being substantially equal to the frequency of a first reference signal when a quiescent voltage is present at the first circuit means input; b. second circuit means responsive to the first reference signal and to the first circuit means output signal for generating a signal having a first time duration proportional to the phase difference between the first reference signal and the first circuit means output signal and a second time duration inversely proportional to said phase difference; c. input impedances means for coupling an unknown input voltage to the first circuit means input; d. feedback impedance means for negatively feeding back the output signal of the second circuit means to the input of the first circuit means, whereby said phase difference is made a function of the unknown input voltage when the first circuit means input has the quiescent voltage thereat; and e. output counter means responsive to the first time duration of the second circuit means output signal and to the frequency of a second reference signal for counting the number of cycles of said second reference signal that occur during said first time duration whereby the counter generates a digital number that is a function of the unknown input voltage.

Claim 3

A voltage conversion circuit as recited in claim 1 additionally comprising third circuit means responsive to a reference voltage for generating the first reference signal.

Claim 4

A voltage conversion circuit as recited in claim 1 additionally comprising: a. signal generating means responsive to a reference voltage for generating a third reference signal; and b. counter means responsive to the frequency of the third reference signal for generating said first reference signal.

Claim 5

A voltage conversion circuit as recited in claim 1 wherein the first circuit means comprises: a. signal generating means having an output responsive to a voltage for generating an output frequency that is a function of its input voltage; and b. counter means responsive to the signal generating means output frequency for generating said output signal.

Claim 6

A vOltage conversion circuit as recited in claim 1 additionally comprising a filter circuit for filtering the input voltage of the first circuit means.

Claim 7

A voltage conversion circuit as recited in claim 1 additionally comprising: a. a holding register for storing the digital number generated by the output counter; and b. readout means responsive to the holding register for providing a visual display of the number stored in the holding register.

Claim 8

A voltage conversion circuit as recited in claim 1 wherein the second circuit means includes switch means for connecting a first reference voltage to the feedback impedance means during the first time duration and a second reference voltage to the feedback impedance means during the second time duration.

Claim 9

A voltage conversion circuit as recited in claim 1 additionally comprising circuit means for compensating for any drift of said quiescent voltage including means for storing in the output counter prior to a voltage conversion a number representative of a reference voltage so that the number generated by the output counter indicates the difference between the unknown voltage and the reference voltage.

Claim 10

A voltage conversion circuit as recited in claim 1 additionally comprising: a. counter means responsive to the frequency of the second reference signal for generating the first reference signal.

Claim 11

A voltage conversion circuit as recited in claim 9 wherein the first circuit means comprises: a. signal generating means having an output responsive to a voltage for generating an output frequency that is a function of its input voltage; and b. counter means responsive to the signal generating means output frequency for generating said output signal.

Claim 12

A voltage conversion circuit as recited in claim 10 additionally comprising: a. a holding register for storing the digital number generated by the output counter; an b. readout means responsive to the holding register for providing a visual display of the number stored in the holding register.

Claim 13

A voltage conversion circuit as recited in claim 11 wherein the second circuit means includes switch means for connecting a second reference voltage to the feedback impedance means during the first time duration and a third reference voltage to the feedback impedance means during the second time duration.

Claim 14

A voltage conversion circuit as recited in claim 12 additionally comprising a filter circuit for filtering the input voltage of the first circuit means.

Claim 15

A voltage conversion circuit as recited in claim 13 additionally comprising circuit means for compensating for any drift of said quiescent voltage including means for storing in the output counter prior to a voltage conversion a number representative of a reference voltage so that the number generated by the output counter indicates the difference between the unknown voltage and the reference voltage.

Claim 16

A voltage conversion circuit as recited in claim 14 additionally comprising an oscillator for generating the second reference signal.

Claim 17

A circuit for use in a voltage converter for generating a digital number that is a function of an unknown voltage including an input impedance and a feedback impedance comprising: a. first circuit means having an input responsive to a voltage for generating an output signal having a frequency that is a function of the voltage at its input, said output signal frequency being substantially equal to the frequency of a first reference signal when a quiescent voltage is present at the first circuit means input; b. second circuit means responsive to the first reference signal and to the first circuit means outward signal for generating a signal having a first time duration proportional to the phase difference between the first reference signal and the first circuit means output signal and a second time duration inversely proportional to said phase difference said first circuit means being adapted to be connected to the input imPedance so that the unknown voltage is coupled to the first circuit means input and wherein the first circuit means input and the second circuit means output are adapted to be connected across the feedback impedance, whereby said phase difference is made a function of the unknown input voltage when the first circuit means input has the quiescent voltage thereat; and c. output counter means responsive to the first time duration of the second circuit means output signal and to the frequency of a second reference signal for counting the number of cycles of said second reference signal that occur during said first time duration whereby the counter generates a digital number that is a function of the unknown input voltage.

Claim 18

A circuit for use in a voltage converter for generating a digital number that is a function of an unknown voltage including an input impedance and a feedback impedance comprising: a. first circuit means having an input responsive to a voltage for generating an output signal having a frequency that is a function of the voltage at its input, said output signal frequency being substantially equal to the frequency of a first reference signal when a quiescent voltage is present at the first circuit means input; b. second circuit means responsive to the first reference signal and to the first circuit means outward signal for generating a signal having a first time duration proportional to the phase difference between the first reference signal and the first circuit means output signal and a second time duration inversely proportional to said phase difference said first circuit means being adapted to be connected to the input imPedance so that the unknown voltage is coupled to the first circuit means input and wherein the first circuit means input and the second circuit means output are adapted to be connected across the feedback impedance, whereby said phase difference is made a function of the unknown input voltage when the first circuit means input has the quiescent voltage thereat; and c. output counter means responsive to the first time duration of the second circuit means output signal and to the frequency of a second reference signal for counting the number of cycles of said second reference signal that occur during said first time duration whereby the counter generates a digital number that is a function of the unknown input voltage.

Claim 19

A circuit as recited in claim 16 additionally comprising: a. counter means responsive to the frequency of the second reference signal for generating the first reference signal.

Claim 20

A circuit as recited in claim 17 wherein the first circuit means comprises: a. signal generating means having an output responsive to a voltage for generating an output frequency that is a function of its input voltage; and b. counter means responsive to the signal generating means output frequency for generating said output signal.

Claim 21

A circuit as recited in claim 18 additionally comprising: a. a holding register for storing the digital number generated by the output counter.

Claim 22

A circuit as recited in claim 19 additionally comprising: a. readout means responsive to the holding register for providing a visual display of the number stored in the holding register.

Claim 23

A circuit as recited in claim 19 wherein the second circuit means includes switch means for connecting a second reference voltage to the feedback impedance means during the first time duration and a third reference voltage to the feedback impedance means during the second time duration.

Claim 24

A circuit as recited in claim 19 additionally comprising a filter circuit for filtering the input voltage of the first circuit means.

Claim 25

A circuit as recited in claim 19 additionally comprising circuit means for compensating for any drift of said quiescent voltage including means for storing in the output counter prior to a voltage conversion a number representative of a reference voltage so that the number generated by the output counter indicates the difference between the unknown voltage and the reference voltage.

Claim 26

A circuit as recited in claim 19 additionally comprising an oscillator for generating the second reference signal.