JPS61226981A - Hall element circuit - Google Patents

Abstract

PURPOSE:To obtain a Hall output having high reliability by providing a Hall element, a waveform converting means converting an output from the Hall element into output voltage having a rectangular wave and a means comparing rectangular-wave output voltage with comparison voltage and making output voltage and comparison voltage to satisfy specific conditions. CONSTITUTION:A Schmitt trigger extracted from a transistor Q2 and comparison voltage VR are fed to a comparator C1. Comparison voltage VR having predetermined magnitude can be set between the H level and L level of a Schmitt trigger circuit in the circuit, and the comparator C1 for the output circuit inverts outputs first when output voltage from the Schmitt trigger circuit reaches comparison voltage VR. When the maximum voltage width of the variation of each output voltage at H and L levels to several output voltage VH and VL at the H and L levels of the Schmitt trigger circuit is represented respectively by VHN and VLN, comparison voltage VR is determined so as to hold VL+VLN<VR<VH-VHN, thus extracting comparison outputs from the comparator C1. Accordingly, digitized Hall outputs having no chattering and high reliability are outputted.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a Hall element circuit such as a Hall IC suitable as a magnetic sensor, and particularly relates to a Hall element circuit such as a Hall IC suitable as a magnetic sensor, and in particular a circuit that passes an output from a Hall element through a hysteresis circuit such as a Schmitt trigger circuit. The present invention relates to a Hall element circuit configured to prevent chattering that occurs when a rectangular output obtained by a process is taken out to the outside.

[Prior Art] Conventionally, this type of circuit is often configured as a digital output type Hall IC, but the output circuit is, for example, a second
It is configured as shown in the figure. In Fig. 2, old is a Hall element, A1 is an amplifier that amplifies the output of the Hall element,
Vcc is a power supply voltage.

Transistor Q1. ! l: Q2 and resistors R1, R2 and R3 constitute a customary Schmitt)) rigging circuit;
The Hall output from the amplifier A1 as shown in Figure (A) is waveform-shaped at the threshold values υ^ and υB, and as shown in Figure 3 (
Obtain a square wave Schmitt trigger circuit output as shown in B).

In Figure 3 (A), υA indicates the input voltage at which the Schmitt trigger circuit output changes from high level () to low level (L), and υB similarly changes from low level (L) to high level (H). Shows changing input voltage.

Such a Schmitt trigger circuit is originally used to eliminate chattering caused by fluctuations in the input magnetic signal when the output is reversed when converting the analog Hall element output into a rectangular pulse, that is, a digital signal. . In other words, Hall ICs are used for key switches, position detection, etc., but the detection output from the Hall element itself is not necessarily output without fluctuation. It is necessary to obtain a well-shaped rectangular digital output even from such an uncertain Hall element output.
As mentioned above, a Schmitt trigger circuit is used. However, in order to output a digital signal to the outside, the output of the Schmitt trigger circuit cannot be used as is, so an output circuit for amplifying this digital signal is added.

That is, the Schmitt trigger circuit output is supplied to an emitter follower consisting of a transistor Q3 and a resistor R4 to directly take out a current, and the current output is sent to a transistor Q.
4, and then taken out from the output terminal 01.

[Problems to be Solved by the Invention] In FIG. 2, the two states of the H level and L level of the output of the Schmidt trigger circuit correspond to the cut-off state and the saturated state of the transistor Q2, so the output is at the H level. An active state exists when inverting from to L level. For this reason, a second circuit that directly extracts current from the Schmitt trigger circuit using an emitter follower, amplifies it, and outputs it to the outside.
In the illustrated conventional output circuit, there is an intermediate state in which the current drawn as the output of the Schmitt trigger circuit changes completely between the H level and the L level.

Therefore, the output circuit operates before the output of the Schmitt trigger circuit is completely inverted, and instead of becoming as shown in Figure 3 (C), only the output of the output circuit becomes as shown in Figure 3 (D). It is possible that there is a state in which the is reversed first. In this state, if the input signal to the Schmitt trigger circuit fluctuates as shown in Figure 3 (E), the output voltage will not change, but the current flowing to the emitter follower will fluctuate, and as a result, as shown in Figure 3 (F ), there is a possibility that chattering will occur in the output of the output circuit taken out from the output terminal 01, and there is no point in using a hysteresis circuit such as a Schmitt trigger circuit.

[Means for Solving the Problem] Therefore, an object of the present invention is to solve the above-mentioned conventional drawbacks and prevent chattering. Another object of the present invention is to provide a Hall element circuit that is appropriately constructed and arranged to perform inversion.

In order to achieve such an object, the present invention compares a Hall element, a waveform conversion means that has input/output characteristics with hysteresis and converts the output from the Hall element into a square wave output voltage, and a square wave output voltage. and a comparison means for comparing with the voltage VR, and when the maximum width of fluctuation for each high level and low level output voltage VH and v of the output voltage in the waveform conversion means is VHN and VLN, respectively,
It is characterized in that the comparison voltage VR is set to V+VLN<VR<VH-V)IN.

[Function] In the present invention, the output of the Schmitt trigger circuit is delivered in the form of voltage before being delivered in the form of current to the subsequent stage, and the voltage level is compared with the comparison voltage, so that the output voltage of the Schmitt trigger circuit is completely Since the output circuit performs a change operation such as inversion only when a change such as inversion occurs, no chattering occurs in the output from the output circuit even if there is fluctuation in the Hall element output. This provides highly reliable digitized Hall output.

[Example] The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a circuit configuration of an embodiment of the present invention.

Here, the same parts as in FIG. 2 are given the same reference numerals. In the present invention, the Schmitt trigger output taken from transistor Q2 and the comparison voltage VR are supplied to comparator C1. With this circuit configuration, a comparison voltage VR of a predetermined magnitude can be set between the H level and L level of the Schmitt trigger circuit, and only when the output voltage of the Schmitt trigger circuit reaches the comparison voltage VR, Comparator C1 of the output circuit inverts the output.

That is, as shown in FIG. 4(A), the H and L level output voltages VH and VL of the Schmitt trigger circuit
When the maximum voltage width of the fluctuation of each of these H and L level output voltages is VHN and VLN, respectively, the comparison voltage VR is expressed as VL +VLN<VR<
By setting VH-VHN, a comparison output as shown in FIG. 4 (CB) is taken out from the comparator C1.

In a Schmitt trigger circuit, the output does not fluctuate at a value intermediate between the H level and L level, so by determining the comparison voltage VR and transferring signals in the form of voltage as described above, digital It is possible to prevent chattering from occurring in the output.

Note that the present invention is not limited to the above-described embodiments, and instead of the Schmitt trigger circuit, an operational amplifier may be provided with feedback to provide hysteresis characteristics, and a waveform shaping circuit with hysteresis in the input/output characteristics may be used. It may be of any form.

[Effects of the Invention] As is clear from the above, according to the present invention, the output of a waveform shaping circuit having hysteresis is passed to the subsequent stage in the form of a voltage, so that the output voltage is applied to the output characteristics of the waveform shaping circuit. By comparing with a comparison voltage determined in relation to A highly reliable digitized Hall output is output. Moreover, the circuit arrangement of the present invention is suitable for integration,
There is also the advantage that the entire device can be configured as a so-called Hall IC.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing an example of a conventional Hall-E C. 3(A) to 3(F) are signal waveform diagrams of each part, and FIGS. 4(A) and 4(B) are signal waveform diagrams of each part in the circuit arrangement shown in FIG. 1. Old...Hall element, AI...amplifier, R1-R3...resistance, Ql, Q2...transistor for Schmitt trigger circuit, Vcc...power supply voltage, VR...comparison voltage, CI...・Comparator, 01...output terminal.

Claims (1)

[Scope of Claims] A Hall element; a waveform conversion means having an input/output characteristic having hysteresis and converting the output from the Hall element into a rectangular wave output voltage; and converting the rectangular wave output voltage into a comparison voltage V_R. and a comparison means for comparing, where the maximum width of fluctuation of the output voltage in the waveform conversion means with respect to the high level and low level output voltages V_H and V_L is respectively V_H_N and V_L_N, the comparison voltage V_R is V_L+V_L_N
A Hall element circuit characterized in that <V_R<V_H−V_H_N.