JPS6221319A - Hysteresis comparator - Google Patents

Abstract

PURPOSE:To improve the accuracy of a reference voltage by obtaining a reference voltage from a constant current source switched in response to an output voltage. CONSTITUTION:A base of a transistor (TR) Q1 is a - input terminal 2 and a base of a TR Q4 is a + input terminal 3, a difference between a signal voltage at the - input terminal 2 and the reference voltage at the + input terminal 3 is amplified to drive a TR Q5. TRs Q7, Q8 are turned on/off by turning on/off a TR Q5 and an output TR Q9 is turned on/off by turning on/off the TR Q3 to obtain an output signal of L/H level. On the other hand, the on/off of TRs Q10, Q11 constituting a switch 13 is changed over by turning on/off the TR Q7, and the constant current source supplying a current to a resistor R10 is obtained switchingly from a constant current source 11 composing of a TR Q13 and a resistor R13 and a constant current source 12 composing of a TR Q14 and a resistor R14. Thus, the accuracy of each reference voltage is increased.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a hysteresis comparator that controls a reference voltage with an output voltage and has hysteresis characteristics in changes in output voltage in response to fluctuations in input voltage. be.

[Conventional technology]

Figure 3 is an explanatory diagram showing an example of a conventional hysteresis comparator. In Figure 2, 1 is a comparator and 2 is ←)
Input end, 3 is (+ input end, 4 is output end, 5 is power supply, 6,
7, 8.9 are resistances.

Comparator 1 is an amplifier with high gain, differential input, and single-ended output, which compares the potential of the reference voltage applied to (+ input terminal 2 and @-) input terminal 3, and outputs a signal. When the voltage is lower than the reference voltage, H is output to output terminal 4.
output a signal.

When it is high, an L signal is output to the output terminal 4.

For example, if the potential of the H signal output to the output terminal 4 is 10V and the open loop gain is 104.

Signal voltage is higher than reference voltage 10V/104 = 10-3
V or higher (or low), output terminal 4 receives L signal and H signal.
Output a signal.

Therefore, for example, if there is noise in the signal, the output signal may malfunction, such as becoming L when it should be H.

In order to prevent the above-mentioned malfunctions, a part of the output voltage is fed back to the gain input terminal 3 to provide hysteresis characteristics, and this is called a hysteresis comparator.

The device shown in the figure has a configuration in which the output terminal 4 and the (+) input terminal 3 are connected through a resistor 8, and a part of the output voltage is fed back to the gain input terminal 3.

For example, if the signal voltage at the (-) input terminal 2 is 1 mV or more lower than the reference voltage at the (+) input terminal 3, the output signal becomes H.
Then, the voltage generated in the resistor 7 due to the current flowing from the output terminal 4 side through the resistor 8 to the resistor 7 is
The output signal will not change unless the signal voltage becomes higher than the added voltage. When the output signal becomes L, the voltage generated in the resistor 7 is subtracted from the reference voltage by the current flowing through the resistor 7 in the opposite direction, and unless the signal voltage becomes lower than the subtracted voltage, the output signal becomes H. It never changes.

In other words, unless the signal voltage becomes a certain potential higher or lower than the trigger level without hysteresis characteristics, the output signal remains unchanged and noise is eliminated.

[Problem that the invention seeks to solve]

A conventional hysteresis comparator is configured as described above, and in order to reduce power consumption, resistors 6, 7, and 8 must be made of high resistance, and the current flowing through resistor 8 is small, so that the reference voltage However, it is difficult to maintain high accuracy due to the influence of current fluctuations due to fluctuations in power supply voltage, and there are also problems in that the load resistor 9 is subject to limitations.

The present invention was made in order to solve the above-mentioned problems, and an object of the present invention is to provide a hysteresis comparator with high accuracy of reference voltage.

[Means for solving problems]

The hysteria 7 Sco/Parator according to this invention is.

The configuration is such that the reference voltage is obtained from a constant current source that switches according to the output voltage.

[Embodiments of the invention]

FIG. 1 is an explanatory diagram showing the basic groove bottom of this invention. In FIG.

10 is a resistor, 11 and 12 are constant current sources, and 13 is a switch.

Constant current sources 11 and 12 connected to a resistor 10 are switched by a switch 13 controlled by the output voltage, and f
It is configured such that a constant reference voltage is applied to each i1 input terminal.

The parts corresponding to the parts indicated by the same reference numerals in FIG. 1 are shown.

PNP) transistor Q1. Q2. Q3. Q4 is connected to Darlington to form a differential amplifier circuit, and the pace of +Ql is (→input terminal 2. The pace of Q4 is (+) input terminal 3. (@signal voltage of input terminal 2 and (+) ) input end 30
The difference in reference voltages is amplified to drive transistor Q5. Transistors jIQ7 and Q8 are turned on and off by turning on and off the transistor Q5.

When the transistor Q8 is turned on or off, the output transistor Q9 is turned on or off, and the output signal increases.

■It becomes.

10,000, by turning on and off transistor Q7.

Transistor Q+o composing switch 13 *
Q.

The constant current source that supplies current to the resistor 10 is connected to the constant current source 11 constituted by the transistor Q13 and the resistor R13, and the transistor Q! 4 and resistor R14
It switches between the constant current source 12 and the constant current source 12 configured by

As described above, when the signal voltage becomes higher (or lower) by a certain voltage than the reference voltage, the output signal increases and becomes H, and the constant current source is selected, and the arrow indicates a certain potential lower or lower than the previous trigger level. High temperature (°C. otherwise the output signal will not change.

Since each reference voltage is formed by a current from a constant current source 11.1.2, the accuracy is high.

〔Effect of the invention〕

As described above, according to the present invention, the accuracy of the reference voltage is increased, the setting of the reference voltage is facilitated, high resistance is not required, and it is possible to obtain an IC ('i: suitable circuit). be.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the basic configuration of the present invention. FIG. 2 is a circuit diagram showing an embodiment of the present invention, and FIG. 3 is an explanatory diagram showing an example of a conventional hysteresis comparator. 1... Comparator, 2... (-) input terminal, 3...
・Soup) input end, 4...output end, 5...power supply, 10.
...Resistance, 11゜12... Constant current source, 13... Switch. Patent applicant New Japan Radio Co., Ltd. Figure 1

Claims (1)

[Claims] In a hysteresis comparator in which the reference voltage is controlled by the output voltage to provide hysteresis characteristics to changes in the output voltage in response to fluctuations in the input voltage, the reference voltage is obtained from a constant current source that switches according to the output voltage. Features a hysteresis comparator.