JPS58112379A - Circuit for reducing unnecessary voltage in hall element - Google Patents

Abstract

PURPOSE:To allow the reduction of an unnecessary voltage generated in a Hall element, by constituting so as to inverse the polarity of a constant current circuit and an amplifier by an analog switch. CONSTITUTION:This circuit is constituted of a power source part 11, an oscillator 12 constituted of a non-stable multi vibrator 12a and a flip-flop circuit 12b, a constant current circuit 13 for Hall element control current constituted of a reference voltage generator 13a and a voltage-current converter 13b, analog switches 14a-14d and 15a-15h driven by outputs Q and Q of the flip-flop circuit 12b, a high input impedance amplifier 16, and a three terminal Hall element 17. By providing analog switches 15a-15h in this manner, the induction voltage generated between Hall element lead wires is modulated by the excitation frequency which drives the analog switches, and can be removed by being passed through a filter.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a voltage circuit for a Hall element, and more specifically, a residual voltage adjustment circuit for a Hall element that improves voltage fluctuations of a Hall element and reduces unnecessary voltage. It is related to.

As shown in Figure 1 (&) and (b), a conventional circuit for reducing unnecessary voltages such as residual voltage of a Hall element includes a constant current circuit 2 and a high input impedance amplification circuit between two terminals of a 5-terminal Hall element 1. Each circuit 3 is connected to an analog switch 4.
A configuration has been proposed in which fluctuations in residual voltage and unnecessary voltage are reduced by connecting this analog switch via a control oscillator and switching the analog switch using the output of a control oscillator.

However, in this conventional circuit, as shown in Figure 2, when the analog switch 4 is turned to the terminal 6 side, the voltage between terminals a and b is
Hab is F) Since VHab = VHbc holds true, VHa c - VHb c = O, and the residual voltage is calculated to disappear.

However, in this conventional circuit, FIG. 3 (IL), (b
), when looking at the way the current flows during operation, the direction of the current flowing through the internal resistor R island is when the constant current circuit 2 is connected to the terminal 6 side and when the constant current circuit 2 is connected to the terminal 7 side. However, in normal semiconductor resistors, this is caused by the rectification effect due to the current direction K due to the electrode formation and crystal structure, as shown in FIG. 3(a).

The internal resistance R1-RaO value in (6) is often not the same. Therefore, when we examine the voltage drop Vab between terminals a and b, #! There is a drawback that the voltage drops in the current direction in FIG. 3(A) and in the current direction in FIG. 3(b) are not equal.

In addition, when measuring an alternating current magnetic field with this conventional circuit, induced voltages are generated between leads AIIIL and lb and between leads IIL and lb of the Hall element 1 in the magnetic field area A to be measured, as shown in FIG. Sl is the magnetic induction area IS between the lead edges 1a and lb, and IS is the magnetic induction area between the lead wires 1a and 18), and when the analog switch 4°S is operated, the induced voltage fv (Ss) as shown in Fig. 5 is generated. fv (sm
) appears as the output voltage VH1-center. If this induced voltage 'tfV (St) - fv (St), then VHab - VHbc = fv (St) fV (Sm)
Here, if the induced voltages fv(St) and fv(St) are equal, no induced voltage will occur, but normally the induced voltages due to the lead wires cannot be made to the same value, so fv(S+
) fV(St) occurs.

The present invention aims to eliminate the above-mentioned two drawbacks, and is characterized by providing an analog switch that alternately connects a constant current circuit and an amplifier between two terminals of a three-terminal Hall element. By configuring the constant current circuit and the amplifier so that their polarities can be reversed by an analog switch, it is possible to reduce unnecessary voltage generated in the switchhole element. The present invention will be described in detail below with reference to an embodiment shown in FIG.

Figure 6 shows a specific example of this invention. This shows the configuration of the voltage reduction circuit, which is composed of a voltage converter 11, an unstable multivibrator 12&, and a flip-flop circuit 12b, an oscillator 12, a reference voltage generator 13&, and a voltage-current converter 13b. a constant current circuit 13 for element control current, and an output Q of the flip-flop circuit 12b;
Analog switches 1411 to xid and 1511 to 15h driven by Q and high input impedance amplifier 1
6 and a 5-terminal Hall element 17.

The analog switches 15a to 15h select the terminal 18 or 19 of the three-terminal Hall terminal 17, and the terminal 18 or 19 in FIG.
) As shown in K, a constant current circuit 13 is selectively connected between terminals & and C or between terminals and C, and between these, analog switches 141L and 14b are also connected with a period that is an integral multiple of the output of the flip-flop circuit 12b. By applying the output, the residual voltage VH is transferred to 04 voltages, and this average value is calculated by connecting a filter to the output of the amplifier 16 and changing the excitation frequency to the filter as shown in FIG. This can be done by passing.

Further, by providing the analog switch 15+1-15h in this way, the above-mentioned induced voltage fv(St) can be reduced.

fv (st) is also the excitation frequency (analog switch 14
a.

14b) and can be removed by passing it through a filter as shown in FIG.

As described above, the present invention is configured such that an analog switch is provided between two terminals of a three-terminal Hall element to alternately connect a constant current circuit and an amplifier, and the polarity of the constant current circuit and the amplifier can be reversed by the analog switch. By doing this, it is possible to reduce the unnecessary voltage generated in the shear element, so the zero point accuracy is α2 Gauss, and the temperature fluctuation at the zero point is 0016.
Gauss/°C can be easily corrected, fluctuations due to external forces on the Hall element are extremely reduced, and in AC magnetic field measurement, D
It has an effect such that the induced voltage between C and 10KH2t can be reduced to 1X or less of the output voltage without using the correction loop of the lead wire.

[Brief explanation of the drawing]

Figures 1 (a) and (b) are both configuration diagrams of a conventional residual voltage adjustment circuit in a three-terminal Hall element, and Figures 2 to 5 are operation explanatory diagrams of a conventional residual voltage adjustment circuit. FIG. 6 is a specific configuration diagram of a circuit for reducing the construction cost voltage generated in a Hall element according to an embodiment of the present invention, and FIGS. 7 and 8 are both explanatory diagrams of the operation of the reducing circuit shown in FIG. 6. DESCRIPTION OF SYMBOLS 11... Power supply part, 12... Oscillator, 13... Constant current circuit, 14JL, 14b, 15a-15h-.
・Analog switch, 17 ・5-terminal Hall element, 18
, 19...terminal. ET.”

Claims (1)

[Claims] A switching circuit that alternately connects a constant current circuit and an amplifier between two terminals of a three-terminal Hall element is provided, and the polarity of the constant current circuit and the amplifier is configured to be reversed by the switching circuit. A Hall element unnecessary voltage reduction circuit characterized by being able to reduce unnecessary voltage.