Frequency to voltage converter using gate voltage sampling of power oscillator

Abstract

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.

What is claimed is: 
     
         1 . A method of controlling an inductive fuel heater, comprising:
 generating a square wave signal based on an oscillating signal of an oscillator that controls an inductive fuel heater, wherein the square wave signal has rising and falling edges which are faster than rising and falling edges, respectively, of the oscillating signal, and the square wave signal has a pulse frequency which is the same as a pulse frequency of the oscillating signal;   generating a pulse train based on the rising and falling edges of the square wave signal, comprising delaying the square wave signal to generate a delayed square wave signal, and providing the square wave signal and the delayed square wave signal to a logic gate, an output of the logic gate corresponding to the pulse train; and   generating an output voltage based on the pulse train, wherein the output voltage is based on a frequency of the oscillator, generating the output voltage comprises integrating the pulse train to generate the output voltage; and   controlling the inductive fuel heater based on the output voltage.   
     
     
         2 . The method of  claim 1 , wherein generating the square wave signal comprises comparing the oscillating signal to a reference signal. 
     
     
         3 . The method of  claim 2 , wherein generating the square wave signal further comprises generating the reference signal based on a digital signal. 
     
     
         4 . The method of  claim 2 , wherein generating the square wave signal further comprises converting a digital signal to an analog signal, the analog signal comprising the reference signal. 
     
     
         5 . The method of  claim 1 , wherein the logic gate is an exclusive OR gate such that generating the pulse train comprises performing an exclusive OR operation on the square wave signal and the delayed square wave signal, an output of the exclusive OR gate corresponding to the pulse train. 
     
     
         6 . The method of  claim 5 , wherein delaying the square wave signal comprises filtering the square wave signal to provide the delayed square wave signal. 
     
     
         7 . The method of  claim 1 , wherein the oscillating signal corresponds to a control signal appearing at a control terminal of a transistor in the oscillator. 
     
     
         8 . A method of controlling an inductive fuel heater, comprising:
 receiving a signal from an oscillator that controls the inductive fuel heater;   generating a square wave signal based on the signal received from the oscillator that controls an inductive fuel heater, wherein the square wave signal has rising and falling edges which are faster than rising and falling edges, respectively, of the signal received from the oscillator, and the square wave signal has a frequency which is the same as a frequency of the signal received from the oscillator;   generating a pulse train based on the rising and falling edges of the square wave signal, comprising delaying the square wave signal to generate a delayed square wave signal, and performing a logic operation on the square wave signal and the delayed square wave signal, an output of logic operation corresponding to the pulse train;   generating an output voltage based on the pulse train, wherein the output voltage is based on a frequency of the oscillator, generating the output voltage comprises integrating the pulse train to generate the output voltage; and   controlling the inductive fuel heater based on the output voltage.   
     
     
         9 . The method of  claim 8 , wherein generating the square wave signal comprises comparing the signal received from the oscillator to a reference signal. 
     
     
         10 . The method of  claim 9 , wherein generating the square wave signal further comprises generating the reference signal based on a digital signal. 
     
     
         11 . The method of  claim 9 , wherein generating the square wave signal comprises converting a digital signal to an analog signal, the analog signal comprising the reference signal. 
     
     
         12 . The method of  claim 8 , wherein the logic operation is an exclusive OR logic operation, an output of the exclusive OR operation corresponding to the pulse train. 
     
     
         13 . The method of  claim 8 , wherein delaying the square wave signal comprises filtering the square wave signal to provide the delayed square wave signal. 
     
     
         14 . The method of  claim 8 , wherein the signal received from the oscillator comprises a control signal appearing at a control terminal of a transistor in the oscillator. 
     
     
         15 . The method of  claim 8 , wherein a linear relationship exists between the output voltage and the frequency of the oscillator when the output voltage is less than a predetermined voltage level corresponding to a time constant associated with integrating the pulse train. 
     
     
         16 . The method of  claim 8 , wherein integrating the pulse train comprises charging and discharging a capacitive element based upon the output of the logic operation, and the method further comprises discharging the capacitive element at a predetermined rate to prevent saturation associated with integrating the pulse train.