Hall electromotive force signal detection circuit having a difference calculation 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 samples a component synchronous with a chopper clock generated by a chopper clock generation circuit, out of an output voltage signal of a signal amplifier circuit, at a timing obtained from the chopper clock, so as to detect the component. An integrating circuit integrates an output from the difference calculation circuit in the time domain. An output voltage signal from the integrating circuit is fed back to a signal amplifier circuit via a third transconductance element.
1. A hall electromotive force signal detection circuit, comprising:
a hall element that generates a signal, which is composed of a hall electromotive force signal and an offset signal component;
a first switching circuit configured to modulate the hall element the hall electromotive force signal at a frequency of a chopper clock to generate an output voltage signal from the first switching circuit;
a signal amplifier circuit configured to amplify the output voltage signal from the first switching circuit to output a first output signal having the ball electromotive force signal and the offset signal component, the offset signal component being modulated at the frequency of the chopper clock; and
a feedback circuit configured to generate a feedback signal to the signal amplifier circuit,
wherein the signal amplifier circuit comprises:
a first transconductance element configured to convert the output voltage signal from the first switching circuit into a first current;
another switching circuit configured to demodulate the hall electromotive force signal based on a primary current to generate the first output signal having the hall electromotive force signal and the offset signal component, the offset signal component being modulated at the frequency of the chopper clock;
a pair of resistors in series connection and configured to perform voltage-division on a component included in the first output signal at a predetermined ratio to generate a divided voltage;
a second switching circuit directly connected to the pair of the resistors and configured to invert a polarity of the divided voltage generated by the voltage-division based on the frequency of the chopper clock to generate an output voltage; and
a second transconductance element configured to convert the output voltage from the second switching circuit into a second current, and configured to output the second current to the another switching circuit,
wherein the feedback circuit comprises:
a difference calculation circuit configured to sample the first output signal to generate a first sampling result at a first timing synchronous with the chopper clock, and a second sampling result at a second timing synchronous with the chopper clock and different from the first time, and configured to generate a second output signal representing a ripple noise in the first output signal by obtaining a difference between the first sampling result and the second sampling result to cancel the hall electromotive force signal in the first output signal;
an integrating circuit configured to integrate the second output signal in the time domain to generate a third output signal as the feedback signal; and
another transconductance element configured to convert the feedback signal into a third current, and configured to output the third current to the another switching circuit, and
wherein the primary current is a sum of the first current, the second current and the third current.
2. The hall electromotive force signal detection circuit according to claim 1 , wherein
the signal amplifier circuit further includes an output stage coupled to the another switching circuit and provided in a subsequent stage of the first transconductance element.
3. The hall electromotive force signal detection circuit according to claim 1 , wherein the difference calculation circuit is a switched capacitor circuit.
4. The hall electromotive force signal detection circuit according to claim 3 , wherein the switched capacitor circuit is a Peak-To-Peak circuit.
5. The hall electromotive force signal detection circuit according to claim 3 , wherein the integrating circuit is a switched capacitor circuit.
6. A current sensor comprising the hall electromotive force signal detection circuit according to claim 1 , wherein the hall element detects a magnetic field induced by a current flowing in a current conductor.
7. The hall electromotive force signal detection circuit according to claim 1 , wherein the second timing is separated from the first timing at a certain time period.
8. The hall electromotive force signal detection circuit according to claim 1 , wherein the another transconductance element has its output directly connected between the first transconductance element and the another switching circuit.