Methods and apparatus for increasing accuracy of RMS measurements of signals with a high crest factor
First Claim
1. An apparatus for determining a root-mean-square (RMS) voltage of an input voltage signal, comprising:
- an amplifier to modify an amplitude of an input voltage signal, wherein the input voltage signal is a pulse width modulated signal supplied to a lamp driver;
an amplitude detector, coupled to the amplifier, that outputs a normalized signal having an amplitude equal to an amplitude of the input voltage signal, with a longer duration of time than the input voltage signal; and
a root-mean-square (RMS) converter, coupled to the amplitude detector, to determine the RMS voltage of the input voltage signal over the longer duration of time, wherein a bandwidth of the RMS converter includes a desired frequency region, and wherein the bandwidth of the RMS converter is smaller than a frequency range of the input voltage signal and larger than a frequency range of the normalized signal such that RMS voltage calculation error is reduced.
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Abstract
Methods and apparatus for determining the root-mean-square (RMS) voltage of an input voltage are provided herein. In some embodiments, an apparatus for determining the root-mean-square (RMS) voltage of an input voltage includes an amplifier to modify an amplitude of the input voltage signal; an amplitude detector, coupled to the amplifier, to transform the spectrum of the modified input voltage signal so that an increased portion of the signal is disposed within a desired frequency region; and a root-mean-square (RMS) converter, coupled to the amplitude detector, to determine the RMS voltage of the transformed input voltage signal, wherein a bandwidth of the RMS converter includes the desired frequency region.
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Citations
20 Claims
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1. An apparatus for determining a root-mean-square (RMS) voltage of an input voltage signal, comprising:
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an amplifier to modify an amplitude of an input voltage signal, wherein the input voltage signal is a pulse width modulated signal supplied to a lamp driver; an amplitude detector, coupled to the amplifier, that outputs a normalized signal having an amplitude equal to an amplitude of the input voltage signal, with a longer duration of time than the input voltage signal; and a root-mean-square (RMS) converter, coupled to the amplitude detector, to determine the RMS voltage of the input voltage signal over the longer duration of time, wherein a bandwidth of the RMS converter includes a desired frequency region, and wherein the bandwidth of the RMS converter is smaller than a frequency range of the input voltage signal and larger than a frequency range of the normalized signal such that RMS voltage calculation error is reduced. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for determining a root-mean-square (RMS) voltage of an input voltage signal, comprising:
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modifying, using an amplifier, an amplitude of the input voltage signal, wherein the input voltage signal is a pulse width modulated signal supplied to a lamp driver; normalizing a spectrum of the modified input voltage signal to generate a normalized signal with an amplitude equal to an amplitude of the input voltage signal and a longer duration of time than the input voltage signal; and determining, using an RMS converter, the RMS voltage of the input voltage signal over the longer duration of time, wherein a bandwidth of the RMS converter includes a desired frequency region, and wherein the bandwidth of the RMS converter is smaller than a frequency range of the input voltage signal, but larger than a frequency range of the normalized signal such that RMS voltage calculation error is reduced. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
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20. A substrate processing apparatus, comprising:
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a process chamber; a lamp array configured to provide heat to the process chamber to process substrates when disposed therein; a lamp driver that delivers stepped-down power to the lamp array as a pulse width modulated input voltage signal; a power source electrically coupled to the lamp driver to deliver power to the lamp driver; a controller communicatively coupled to the lamp driver to control operation of the lamp driver; and a measuring system coupled to an output voltage of the lamp driver and configured to provide root-mean-square (RMS) voltage information to the controller to control the lamp driver, the measuring system comprising; an amplifier to modify an amplitude of the input voltage signal provided by the lamp driver; an amplitude detector, coupled to the amplifier, that outputs a normalized signal having an amplitude equal to an amplitude of the input voltage signal, with a longer duration of time than the input voltage signal; and a root-mean-square (RMS) converter, coupled to the amplitude detector, to determine the RMS voltage of the input voltage signal over the longer duration of time, wherein a bandwidth of the RMS converter includes a desired frequency region, and wherein the bandwidth of the RMS converter is smaller than a frequency range of the input voltage signal and larger than a frequency range of the normalized signal such that RMS voltage calculation error is reduced.
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Specification