Gate-Voltage Frequency-to-Voltage Conversion for Lossless Oscillator Sensing
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Solution Overview
Problem
Existing methods for measuring oscillator frequency in control systems, such as those used in engine control modules for fuel-injected internal combustion engines, are costly and inefficient, as direct measurement of high output currents or voltages introduces losses and requires expensive components like sense resistors or Hall sensors.
Innovation Solution
A frequency-to-voltage conversion module comprising a pulse shaping module, an edge-to-pulse conversion module, and an integrator module, utilizing a comparator, exclusive OR gate, and resistor-capacitor filtering to generate an output voltage based on the oscillator frequency, eliminating the need for direct current or voltage measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct measurement of oscillator output current or voltage is used, then frequency measurement is achieved, but measurement losses occur and expensive components are required
Solution Approach 1:
The patent uses an intermediary approach by measuring the gate voltage of the power oscillator instead of directly measuring the high-power output current or voltage. The gate voltage is a low-power control signal that correlates with the oscillator frequency but requires no power extraction from the main oscillator output. This intermediary measurement point eliminates the need for sense resistors or Hall sensors in the high-power path, thereby avoiding measurement losses while still providing accurate frequency information.
2Measurement precision
If sense resistors or Hall sensors are used for current measurement, then frequency measurement is achieved, but component cost increases
Solution Approach 1:
The patent measures an intermediary signal (gate voltage) rather than the main oscillator output current, which eliminates the need for expensive sense resistors or Hall sensors. The gate voltage can be measured using simple voltage divider circuits and standard ADC components already present in the engine control module, significantly reducing component costs while maintaining measurement accuracy.
Solution Approach 2:
The patent creates a copy of the frequency information by measuring the gate voltage waveform, which contains the same frequency characteristics as the oscillator output but requires much less power and simpler measurement circuitry. This copied signal can be processed through standard voltage division and ADC conversion using inexpensive components.
3Measurement precision
If complex circuitry such as charge-pump or PLL integrated circuit is used, then frequency-to-voltage conversion is achieved, but device complexity increases
Solution Approach 1:
The patent breaks down the frequency-to-voltage conversion process into simple sequential stages: voltage division to scale down the gate voltage, ADC conversion to digitize the signal, and software-based frequency calculation. This segmentation replaces complex analog PLL or charge-pump circuits with simpler digital processing steps that can be implemented using existing microcontroller resources.
Solution Approach 2:
The patent replaces complex analog frequency-to-voltage conversion circuitry (mechanical/electrical systems like PLLs and charge-pumps) with digital signal processing. The frequency measurement is performed by digitizing the gate voltage waveform and calculating frequency in the digital domain, eliminating the need for complex analog conversion circuits.
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 solution provides a cost-effective and efficient method for converting oscillator frequency to voltage, enabling precise control of inductive fuel heaters without introducing measurement losses, thus improving fuel atomization and reducing hydrocarbon emissions.
Implementation Method 1
The pulse shaping module comprises a comparator. The F2V conversion module includes a digital to analog conversion module that generates a reference voltage for the comparator.
Implementation Method 2
The edge to pulse conversion module comprises an exclusive OR (X-OR) gate. The pulse train is coupled to one input of the X-OR gate and a delayed version of the pulse train is coupled to a second input of the X-OR gate.
Implementation Method 3
The F2V conversion module includes a filter that provides the delayed version of the pulse train.
Implementation Method 4
The integrator module comprises a capacitor that charges through a resistor.
Implementation Method 5
The integrator module comprises a capacitor that charges through a resistor.
Implementation Method 6
The oscillator powers an inductive heater that is incorporated into the fuel injector. The inductive heater heats the fuel during predetermined conditions, such as cold starts, to improve fuel atomization from the injector.
Data Source
AI summary
A frequency-to-voltage (F2V) conversion module includes a pulse shaping module that generates a square wave signal based on an oscillator signal, an edge to pulse conversion module that generates a pulse train based on corresponding rising and falling edges of the square wave signal, and an integrator module that generates an output voltage based on the pulse train. The output voltage is based on a frequency of the oscillator signal.