JPS59220657A - Hysteresis voltage comparator circuit - Google Patents

Abstract

PURPOSE:To realize desired hysteresis characteristics, by constituting the titled comparator circuit from a voltage comparator circuit for comparing input voltage and reference voltage while outputting the comparison result, a non-linear element inserted into the current supply path of said circuit in series and a reference voltage generating circuit for generating reference voltage while dividing power source boltage actually applied to the voltage comparator circuit in a constant ratio. CONSTITUTION:Input voltage Vin is inputted to the inverse phase terminal (-) of a CP amplifier 3 from an input terminal 1 through an input resistor 2 and a current is supplied to a reference voltage generating circuit constituted of voltage dividing resistors 6, 7 and the OP amplifier 3 through a Zener diode 8 connected to a power source -VEE. Voltage obtained by adding Zener voltage Vz to the power source voltage -VEE is inputted to the positive phase input terminal (+) of the OP amplifier 3 while divided by the voltage dividing resistors 6, 7. When the input voltage Vin is low, slightly high reference voltage Vrefo is obtained and, when the input voltage Vin becomes higher than the reference voltage Vrefo at one, slightly low reference voltage Vrefl is obtained thereafter.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a voltage comparison circuit having hysteresis characteristics, and particularly to a voltage comparison circuit suitable for realizing a minute hysteresis voltage width. It is something.

[Background of the invention]

First, a conventional example will be explained according to the drawings.

FIG. 1 is a circuit diagram of an example of the conventional hysteresis sleep pressure comparison circuit.

This conventional example uses an operational amplifier (hereinafter referred to as
(referred to as an OP amplifier) 3 is used, and its power supply is a single negative power supply -VEE from a power supply terminal 5. In addition, the voltage of the power supply -V B E is divided by the voltage dividing resistors 6 and 7.
is used as a reference voltage for comparison, the output voltage of the OP amplifier 3 is divided by resistors 8A and 8B having a sufficiently large resistance value compared to the resistor 7, and this is applied to the positive phase input terminal of the ○P amplifier 3 (- By providing positive feedback to I→, it becomes an I-heat with hysteresis characteristics.

When the input voltage VIn applied to the input terminal 1 becomes lower than the direct voltage of the positive phase input terminal ('→), the output terminal of this circuit;
The voltage becomes close to -VEE, and current flows through the load resistor 9.

However, the normally required hysteresis voltage width must be very small in many cases, and in order to provide a very small hysteresis voltage width in this circuit type, the resistance value of the resistor 8B must be much larger than the resistance value of the resistor 8A. It is necessary to make it a thing. Further, the resistor 8A must be made sufficiently thicker than the resistor 7 so as not to disturb the voltage of the reference voltage generating circuit composed of the resistors 6 and 7.

On the other hand, since the tm and i voltages VEE are always applied to the resistors 6 and 7, it is disadvantageous to reduce their resistance values excessively from the viewpoint of power consumption of the circuit.

Therefore, according to the resistance value conditions described above, the resistance 8
Unless the resistance value of B is set to an extremely large value, it is difficult to realize a minute hysteresis magnetic pressure width.

In other words, in order to use such a large resistance box,
The input bias current of the OP amplifier 3 used as a voltage comparison circuit must be small, which makes it expensive and economically disadvantageous.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the conventional circuits as described above and to provide a detailed hysteresis voltage comparison circuit.

[Summary of the invention]

The configuration of the hysteresis voltage comparison circuit according to the present invention includes a voltage comparison circuit that compares an input voltage with a reference voltage and outputs the result, a nonlinear element inserted and connected in series in the current supply path, and the voltage comparison circuit that compares the input voltage with a reference voltage and outputs the result. The reference voltage generation circuit generates and supplies the reference voltage by dividing the power supply voltage actually applied to the circuit at a fixed ratio.

The following is a supplementary explanation of this.

A nonlinear element such as a Zener diode is inserted in series with the power supply, and a reference voltage generation circuit is connected in series with a resistor to divide the voltage into resistors.
Connect the power supply terminal of a voltage comparison circuit such as an amplifier.

The reference voltage input to the voltage comparison circuit is taken from the reference voltage generation circuit. As a result, the power supply current flowing through the voltage comparator circuit changes according to the input terminal voltage, and the current change is converted into a voltage change by the nonlinear element, so there is no possibility that the reference voltage will also change. By appropriately selecting various constants, desired hysteresis characteristics can be realized.

[Embodiments of the invention]

Embodiments of the present invention will be described below based on the drawings.

FIG. 2 is a circuit diagram of an embodiment of the hysteresis voltage comparison circuit according to the present invention, FIG. 3 is a voltage/current characteristic diagram of the Zener diode, and FIG. 4 is an operation time chart of the circuit.

Here, 1 is an input terminal, 2 is an input resistor, 3 is an OP amplifier related to a voltage comparison circuit, 4 is an output terminal, 5 is a power supply terminal, 6
, 7 is the voltage dividing resistor (resistance value RA
, Rn), 8 is a Zener diode related to the nonlinear element, and 9 is a load resistance (resistance value R17).

The input voltage V'+n is input from the input terminal 1 through the input resistor 2 to the negative phase input terminal (-) of the OI amplifier 3.

A reference voltage generation circuit consisting of voltage dividing resistors 6 and 7 through a Zener diode 8 connected to the power supply -Vgg;
Power is supplied to the OP amplifier 3.

The positive phase input terminal (+) of the OP amplifier 3 is connected to the power supply voltage VE.
The voltage obtained by adding the Zener voltage Vz to E is the voltage that is applied to the voltage dividing resistors 6 and 7.
The voltage is divided and input by .

The fact that a load resistor 9 is connected to the output terminal 4 of the OP amplifier 3 is the same as in the conventional circuit shown in FIG.

Now, the input voltage V 1n to the OP amplifier 3 is the voltage vre f applied to the positive phase input terminal (+) of the OP amplifier 3.
When the voltage is also small, the voltage at the output terminal 4 of the OP amplifier 3 is 1l-j:O, and no current flows through the load resistor 9.

The current flowing through the Zener diode 8 at this time is IZO
Then, the voltage across the Zener diode 8 is VZO due to the voltage/current characteristics shown in FIG.

If the reference voltage applied to the positive phase input terminal (+) of the OP amplifier 3 at that time is Vre'IQ, and the resistance values of the voltage dividing resistor 6゜7 are RA and 几B, then Rn V"°' .=RA+Rn ”■+VzO) =゛(1
).

Next, the input voltage V+□ is applied to the positive phase input terminal of the OP amplifier 3 (
g) voltage V,. When f is also small, oP amplifier 3
The low voltage at output terminal 4 is close to -VEE, and the load resistance 9
A current represented by VEE/RL flows through.

Here, assuming that the current consumption inside the OP amplifier 3 does not change with respect to changes in the input voltage Van, and in this case, if the current flowing through the Zener diode 8 is Izl, then Iz+ = Izo + VEE/R1,・・・・・・
...(2), and as shown in FIG. 3, the voltage Vz across the Zener diode 8 at this time becomes Vz4.

Therefore, the voltage at the positive phase input terminal (+) of the OP amplifier 3 is as follows.

In equations (1) and (3), as is clear from Fig. 3, there is a relationship of V2, ) Vzo −・−−(4), so Vrsfl > ■ro f Q pa'...
...(5) holds true.

That is, as shown in FIG. 4, the voltage comparison operation by this circuit results in a high reference voltage VrafQ, and once the input voltage Vtn becomes the reference voltage ■1°! . After that, the reference voltage Vrsfl becomes slightly lower. In this way, a hysteresis characteristic is achieved.

By using a Zener diode or a normal diode as the nonlinear element, the hysteresis/smear pressure width can be changed.

〔Effect of the invention〕

As described above in detail, according to the present invention, a hysteresis voltage comparator circuit that particularly requires a minute hysteresis voltage width can be realized without using an OP amplifier with low input bias melting or a high resistance. can be done, and the effect is remarkable.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an example of a conventional hysteresis voltage comparison circuit, FIG. 2 is a circuit diagram of an embodiment of a hysteresis voltage comparison circuit according to the present invention, and FIG. 3 is a diagram showing the voltage and current of the Zener diode. The characteristic diagram, FIG. 4, is an operation time chart of this circuit. DESCRIPTION OF SYMBOLS 1... Input terminal, 2... Input resistance, 3... OP amplifier, 4... Output terminal, 5... Power supply terminal, 6, 7...
...Divider resistance, 341- 1st diagram 2nd rod 3rd 40th (a) (()

Claims (1)

[Claims] 1. A voltage comparison circuit that compares the input terminal with a reference voltage and outputs the result, a nonlinear element inserted and connected in series to the current supply path, and a voltage that is actually applied to the voltage comparison circuit. A hysterinos voltage comparator circuit comprising a reference voltage generation circuit that generates and supplies the reference voltage by dividing the power supply voltage at a constant ratio.