PWM Reference AC Voltage Measurement Without Wide-Temp ADCs
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Solution Overview
Problem
Aircraft voltage measurement systems face challenges in achieving accurate AC voltage measurement over extended temperature ranges (-55°C to +100°C) due to the high costs and limited availability of analog-to-digital converters (ADCs) required for wide temperature operating conditions, which also impose computational burdens and increase verification and certification scrutiny.
Innovation Solution
A voltage measurement system that uses a comparator, processor, digital isolation circuits, and RC circuits to calculate AC peak voltage without relying on ADCs, utilizing a pulse width modulation reference voltage and leveraging field programmable gate arrays (FPGAs) or digital signal processors (DSPs) to execute the computation, thereby eliminating the need for premium ADCs and simplifying the design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If analog-to-digital converters (ADCs) are used for wide temperature operating ranges, then voltage measurement accuracy is improved, but system cost increases
Solution Approach 1:
The patent extracts the ADC component from the voltage measurement system and replaces it with a comparator-based peak detection circuit. The comparator compares the input voltage signal with a reference voltage to generate timing signals, which are then processed by a microprocessor to determine the peak voltage value, thereby eliminating the need for expensive wide-temperature ADCs
Solution Approach 2:
The patent uses a pulse width modulation (PWM) signal as a reference voltage that is iteratively adjusted to match the input voltage waveform. By copying the characteristics of the input signal through PWM duty cycle adjustment and using this as a reference for comparison, the system can determine peak voltage without requiring high-precision ADC conversion
2Measurement precision
If analog-to-digital converters (ADCs) are used for wide temperature operating ranges, then voltage measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent removes the ADC from the measurement chain and replaces it with simpler comparator-based peak detection circuitry. The comparator generates timing signals when the input voltage crosses reference levels, and a microprocessor processes these timing signals to calculate peak voltage, reducing overall system complexity
Solution Approach 2:
The patent substitutes the electronic ADC conversion process with a timing-based measurement approach. By measuring the duration of comparator output signals (time-of-flight measurement principle) and processing these time intervals digitally, the system replaces complex analog-to-digital conversion with simpler timing and digital processing
3Measurement precision
If analog-to-digital converters (ADCs) are used for wide temperature operating ranges, then voltage measurement accuracy is improved, but verification and certification scrutiny increases
Solution Approach 1:
The patent extracts the ADC component that requires extensive verification and certification for wide-temperature operation. By replacing it with comparators and digital processing, the system uses components with simpler certification requirements while maintaining measurement accuracy through timing-based peak detection
Solution Approach 2:
The patent uses PWM signals to replicate the input voltage characteristics and compares these copied waveforms to determine peak values. This approach uses well-understood PWM and comparator technologies that have established verification procedures, reducing certification scrutiny compared to ADC-based solutions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for accurate AC voltage measurement on aircraft without the need for expensive ADCs, reduces computational burdens, and simplifies verification and certification processes by using common-off-the-shelf components, ensuring reliable operation across extended temperature ranges.
Implementation Method 1
a comparator having a positive input terminal and a negative input terminal, a processor configured to supply a reference voltage signal to the negative input terminal of the comparator, wherein the positive input terminal of the comparator receives an input voltage
Implementation Method 2
a resistor capacitor (RC) circuit connected between a reference signal output of the processor and the negative input terminal of the comparator
Data Source
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AI summary
A voltage measurement system (200) and method (400) is provided. Aspects include a comparator (204) having a positive and a negative input terminal, a processor (202) configured to supply a reference voltage signal (212) to the negative input terminal, wherein the positive input terminal receives an input voltage (210), setting the reference voltage signal to a zero voltage signal, determine a line frequency of the input voltage based on a timing signal from the comparator and determining a first pulse width of the input signal based on the timing signal, set the reference voltage to a PWM signal (214) with a fixed duty cycle, receive the timing signal from the output of the comparator, determine a rising edge and a falling edge associated with the input voltage based on the timing signal, and determine a peak value of the input voltage based on a second pulse width between the rising and falling edge.