Zero-crossing detection circuit and sensor device

Abstract

Provided is a zero-crossing detection circuit capable of detecting zero-crossing with high accuracy without being influenced by noise. The zero-crossing detection circuit includes a first comparison circuit, a second comparison circuit having a hysteresis function, and a logic circuit. The first comparison circuit is configured to output a zero-crossing detection result of a first input signal and a second input signal. The second comparison circuit is configured to output a comparison result of the first input signal and the second input signal. The logic circuit includes a unit configured to determine whether to reflect the zero-crossing detection result to output of the logic circuit based on the zero-crossing detection result and the comparison result.

What is claimed is: 
     
         1 . A zero-crossing detection circuit, comprising:
 a first comparison circuit configured to receive a first input signal and a second input signal as input;   a second comparison circuit having a hysteresis function and being configured to receive the first input signal and the second input signal as input; and   a logic circuit,   the first comparison circuit being configured to output a first comparison result of the first input signal and the second input signal,   the second comparison circuit being configured to output a second comparison result of the first input signal and the second input signal,   the logic circuit being configured to determine whether to reflect the first comparison result to output of the logic circuit based on the second comparison result.   
     
     
         2 . A zero-crossing detection circuit according to  claim 1 ,
 wherein, under a first condition in which the second comparison result has a first level and the output of the logic circuit has a first output level, transition of the first comparison result from the first level to a second level causes transition of the output of the logic circuit to a second output level,   wherein, under a second condition in which the second comparison result has the second level and the output of the logic circuit has the second output level, transition of the first comparison result from the second level to the first level causes transition of the output of the logic circuit to the first output level, and   wherein the output of the logic circuit is prevented from being changed under a state other than the first condition and the second condition.   
     
     
         3 . A zero-crossing detection circuit according to  claim 1 , wherein the first comparison circuit has a hysteresis width that is smaller than a hysteresis width of the hysteresis function of the second comparison circuit. 
     
     
         4 . A zero-crossing detection circuit according to  claim 1 ,
 wherein the first comparison circuit and the second comparison circuit are constructed of the same comparison circuit, and   wherein the zero-crossing detection circuit further comprises means for switching operation states of the first comparison circuit and the second comparison circuit.   
     
     
         5 . A zero-crossing detection circuit according to  claim 1 ,
 wherein the first comparison circuit and the second comparison circuit are constructed of the same comparison circuit, and   wherein the zero-crossing detection circuit further comprises voltage addition means for switching a voltage to be added to at least one of the first input signal or the second input signal.   
     
     
         6 . A zero-crossing detection circuit according to  claim 1 , wherein the first input signal and the second input signal comprise voltages. 
     
     
         7 . A zero-crossing detection circuit according to  claim 1 , wherein the first input signal and the second input signal comprise currents. 
     
     
         8 . A sensor device, comprising:
 a sensor element configured to output a signal based on an intensity of a physical amount applied to the sensor element; and   the zero-crossing detection circuit of  claim 1 , which is configured to detect zero-crossing of the signal output from the sensor element.   
     
     
         9 . A sensor device according to  claim 8 ,
 wherein the first input signal comprises an output signal of a first sensor element, and   wherein the second input signal comprises an output signal of a second sensor element.   
     
     
         10 . A zero-crossing detection circuit, comprising:
 a first comparison result signal representing magnitudes of a first input signal and a second input signal; and   a second comparison result signal representing whether a difference between the first input signal and the second input signal is larger or smaller than a predetermined value,   the zero-crossing detection circuit being configured to output, based on the second comparison result signal, a signal that is based on the first comparison result signal to an output signal.   
     
     
         11 . A zero-crossing detection circuit according to  claim 10 , wherein the first input signal and the second input signal comprise voltages. 
     
     
         12 . A zero-crossing detection circuit according to  claim 10 , wherein the first input signal and the second input signal comprise currents. 
     
     
         13 . A sensor device, comprising:
 a sensor element configured to output a signal based on an intensity of a physical amount applied to the sensor element; and   the zero-crossing detection circuit of  claim 10 , which is configured to detect zero-crossing of the signal output from the sensor element.   
     
     
         14 . A sensor device according to  claim 13 ,
 wherein the first input signal comprises an output signal of a first sensor element, and   wherein the second input signal comprises an output signal of a second sensor element.