HALL ELECTROMOTIVE FORCE SIGNAL DETECTION CIRCUIT AND CURRENT SENSOR THEREOF
The present invention relates to a hall electromotive force signal detection circuit and a current sensor thereof each of which is able to achieve excellent wide-band characteristics and fast response as well as high accuracy. A difference calculation circuit ( 15 ) samples a component synchronous with a chopper clock generated by a chopper clock generation circuit ( 14 ), out of an output voltage signal of a signal amplifier circuit ( 13 ), at a timing obtained from the chopper clock, so as to detect the component. An integrating circuit ( 16 ) integrates an output from the difference calculation circuit ( 15 ) in the time domain. An output voltage signal from the integrating circuit ( 16 ) is fed back to a signal amplifier circuit ( 13 ) via a third transconductance element ( 17 ).
1 . A hall electromotive force signal detection circuit configured to suppress an offset signal component in a signal composed of a hall electromotive force signal generated in a Hall element and the offset signal component and amplify the hall electromotive force signal to generate an output signal, the hall electromotive force signal detection circuit comprising:
a signal amplifier circuit configured to amplify an output of the hall element and output a signal having the offset signal component modulated at a frequency of a chopper clock;
a difference calculation circuit configured to sample a component synchronous with the chopper clock out of an output signal from the signal amplifier circuit at a timing synchronous with the chopper clock, and output a difference between sampling results at different time;
an integrating circuit configured to integrate an output from the difference calculation circuit in time domain; and
a feedback circuit configured to feed back an output signal from the integrating circuit to the signal amplifier circuit.
2 . The hall electromotive force signal detection circuit according to claim 1 , comprising:
a first switching circuit configured to perform switching operations on terminal pairs of the Hall element in which a terminal pair for driving a driving current to the hall element and a terminal pair for detecting the hall electromotive force signal are interchanged, and to modulate the hall electromotive force signal generated in the hall element at the frequency of the chopper clock, wherein:
the signal amplifier circuit amplifies an output signal from the first switching circuit and modulates the output signal at the frequency of the chopper clock, so that the hall electromotive force signal is demodulated to a low-frequency component including a direct current component, and outputs a signal having the offset signal component modulated at the frequency of the chopper clock.
3 . The hall electromotive force signal detection circuit according to claim 2 , wherein:
the signal amplifier circuit includes:
a first transconductance element configured to convert an output voltage signal of the first switching circuit into a current so as to generate a first current;
resistors configured to perform voltage-division on a component included in the output voltage signal of the first switching circuit at a predetermined ratio;
a second switching circuit configured to invert the polarity of a voltage generated by the voltage-division according to the chopper clock; and
a second transconductance element configured to convert an output voltage from the second switching circuit into a current so as to generate a second current, wherein, the feedback circuit includes a third transconductance element configured to convert an output voltage from the integrating circuit into a current so as to generate a third current, and
wherein, with regard to a current sum of the first current I 1 , the second current I 2 , and the third current I 3 , the feedback circuit performs feedback operation in which a DC component included in a sum of the first current and the second current in the signal amplifier circuit is added with the third current such that the current sum becomes zero (I 1 +I 2 +I 3 =0).
4 . The hall electromotive force signal detection circuit according to claim 3 , wherein:
a third switching circuit configured to modulate an input signal at the frequency of the chopper clock, and an output stage coupled to the third switching circuit are provided in a subsequent stage of the first transconductance element.
5 . The hall electromotive force signal detection circuit according to claim 4 , wherein:
a fourth transconductance element is provided between a subsequent stage of the third switching circuit and the difference calculation circuit.
6 . The hall electromotive force signal detection circuit according to claim 1 , wherein:
the difference calculation circuit and the integrating circuit are switched capacitor circuits.
7 . The hall electromotive force signal detection circuit according to claim 1 , wherein:
the difference calculation circuit is composed of an AD converter, and the integrating circuit is composed of digital circuits.
8 . The hall electromotive force signal detection circuit according to claim 7 , wherein:
the AD converter is a ΔΣ-modulation AD converter.
9 . The hall electromotive force signal detection circuit according to claim 7 , wherein:
the AD converter is a double-integral AD converter.
10 . A current sensor using the hall electromotive force signal detection circuit according to claim 1 .