Methods and apparatus for peak-voltage measurement of AC signals

Patent metadata

Field	Value
Publication number	US-10107841-B2
Application number	US-201615172403-A
Country	US
Kind code	B2
Filing date	Jun 3, 2016
Priority date	Jul 24, 2015
Publication date	Oct 23, 2018
Grant date	Oct 23, 2018

Abstract

In described examples, an apparatus includes: an input terminal for receiving an alternating current voltage signal; a clamping circuit coupled to the input terminal outputting a clamped voltage signal that is constrained in magnitude; a first comparator coupled to the clamped voltage signal outputting a first compare signal when the clamped voltage signal is a positive voltage that exceeds a positive threshold; and a second comparator coupled to the clamped voltage signal outputting a second compare signal when the clamped voltage signal is a negative voltage that exceeds a negative threshold. The apparatus includes a timer circuit coupled to the first and second compare signal outputting a time duration signal corresponding to a time between the first and second compare signals; and a logic circuit coupled to the time duration output signal determining a peak voltage of the alternative current voltage signal responsive to the time duration output signal.

First claim

What is claimed is:

1. An apparatus, comprising: an input terminal for receiving an alternating current voltage signal; a clamping circuit coupled to the input terminal, the clamping circuit configured to output a clamped voltage signal that is constrained between a positive voltage magnitude and a negative voltage magnitude; a first comparator coupled to the clamped voltage signal, and configured to output a first compare signal when the clamped voltage signal is a positive voltage that exceeds a positive threshold reference voltage; a second comparator coupled to the clamped voltage signal and configured to output a second compare signal when the clamped voltage signal is a negative voltage that exceeds a negative threshold reference voltage; a timer circuit coupled to the first compare signal and coupled to the second compare signal and coupled to a clock signal, and configured to output a time duration output signal corresponding to a time interval between the first and second compare signals; and a logic circuit coupled to the time duration output signal and configured to determine a slew rate of the alternative current voltage signal responsive to the time duration output; wherein the logic circuit is configured to perform the calculation: Slew Rate=2*Vth/delta t; where Vth equals the positive threshold voltage, and delta t is equal to a ratio of the time duration output signal divided by the frequency of the clocked signal.

2. The apparatus of claim 1 , wherein the logic circuit is further configured to perform the calculation: Vpeak=Slew Rate*T/4; where T is the period of the alternating current voltage signal.

3. The apparatus of claim 1 , wherein the clamping circuit further includes one or more diodes.

4. The apparatus of claim 1 , wherein the clamping circuit further includes a first diode that is forward biased with respect to a positive voltage and a second diode arranged in parallel to the first diode that is forward biased with respect to a negative voltage, relative to a ground terminal.

5. The apparatus of claim 1 , wherein the first and second comparators each further include a hysteretic comparator.

6. The apparatus of claim 1 , wherein the logic circuit is arranged to output a signal indicating the voltage Vpeak exceeds a predetermined threshold.

7. The apparatus of claim 1 , wherein the predetermined threshold is greater than 100 Volts.

8. The apparatus of claim 1 , further comprising an impedance series coupled between the input terminal and the clamping circuit.

9. The apparatus of claim 8 , wherein the impedance further includes a resistor.

10. The apparatus of claim 8 , and further comprising a second impedance coupled between the output of the first impedance and a ground terminal.

11. The apparatus of claim 10 , wherein the logic circuit is further configured to perform the calculation:
V peak=(1+value of the first impedance/value of the second impedance)*Slew Rate* T/ 4; where T is the period of the alternating current voltage signal.

12. The apparatus of claim 1 , wherein the alternating current voltage signal has a peak voltage that exceeds a maximum input voltage.

13. The apparatus of claim 12 , wherein the alternating current voltage signal has a peak voltage greater than 40 Volts.

14. A method, comprising: receiving an alternating current voltage signal; forming a clamped voltage signal from the alternating current voltage signal, wherein the clamped voltage signal is constrained to a predetermined maximum positive voltage and a predetermined negative voltage that are less than a peak voltage of the alternating current voltage signal; comparing the clamped voltage signal to a positive reference threshold voltage, and outputting a set signal when the clamped voltage signal exceeds the positive reference threshold voltage; comparing the clamped voltage signal to a negative threshold voltage, and outputting a reset signal when the clamped voltage signal exceeds the negative reference threshold voltage; forming a timer duration signal indicating a time between the set and reset signals; and using the timer duration signal, determining a slew rate in the alternating current voltage signal; wherein determining a slew rate in the alternating current voltage signal includes performing the calculation of: Slew Rate of the alternating current voltage signal=2*Vth/delta t; where Vth equals the positive threshold voltage, and delta t is equal to a ratio of the output of the timer circuit divided by the frequency of the clocked signal.

15. The method of claim 14 , wherein determining a peak voltage in the alternating current voltage signal includes performing the calculation of: Vpeak=Slew Rate*T/4; where T is the period of the alternating current voltage signal.

16. The method of claim 15 , and further comprising:
outputting a signal indicating when the calculated peak voltage is greater than a predetermined threshold.

17. An integrated circuit for monitoring an alternating current voltage signal, comprising: an input terminal coupled to receive the alternating current voltage signal; a clamping circuit coupled to the input terminal and having a clamped output voltage, the clamping circuit configured to limit the output voltage signal between a predetermined positive voltage magnitude and a predetermined negative voltage magnitude; a first comparator coupled to the clamped output voltage and coupled to a positive threshold reference voltage, and configured to output a set signal responsive to a positive magnitude of the output voltage signal exceeding the positive threshold reference voltage; a second comparator coupled to the clamped output voltage and coupled to a negative threshold reference voltage, and configured to output a reset signal responsive to a negative magnitude of the output voltage signal that exceeding the negative threshold reference voltage; a timer circuit coupled to the set signal and coupled to the reset signal and configured to sample the set signal and the reset signal responsive to a clock signal, and to output a time duration signal corresponding to the time between set and reset signals; and a logic circuit coupled to the timer circuit and configured to determine a peak voltage in the alternating current voltage signal responsive to the time duration signal; wherein the logic circuit is configured to perform the calculations of: Slew Rate of the alternating current voltage signal=2*Vth/delta t; where Vth is the positive threshold voltage, and delta t is equal to a ratio of the output of the timer circuit divided by the frequency of the clocked signal, and Vpeak=Slew Rate*T/4; where T is the period of the alternating current voltage signal.

Assignees

• Texas Instruments Inc

Inventors

• Tasevski Viktor
• Demirci Kemal S

Classifications

• G01R19/04 Primary

  Measuring peak values {or amplitude or envelope} of AC or of pulses · CPC title