JPS63236971A - Comparing device - Google Patents

Abstract

PURPOSE:To accurately detect a signal which varies at a high speed in a background signal by obtaining a reference voltage from an input signal by voltage division and removing its fast variation component. CONSTITUTION:The detection signal of a photodiode 1 is supplied to a comparing device 300 through an operational amplifier 7 and a feedback resistance 2. The device 300 obtains the voltage-divided reference voltage by a voltage generating circuit 30 according to the input signal and its high-frequency variation light quantity component is extracted by a capacitor 6 by by-passing to generate a reference signal (b). A comparator 8 compares the input signal (a) with the reference voltage (b) to obtain an output signal (c). This signal is obtained by detecting clearing the part which varies at the high speed in the signal (a) and corresponds to the level of background light.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) This invention is useful for detecting rapidly changing amounts of light, etc.
The present invention relates to a comparison device that can be used when detecting a signal that changes at high speed.

(Prior Art) Conventionally, as shown in FIG. 3, the sterilization comparator W1200 avoids the effects of the offset voltage up to the amplifier 100 in the previous stage, offset voltage fluctuations, and fluctuations in the background signal level due to changes in the amount of background light. Therefore, the configuration was such that the signal was received by the comparator 102 via the capacitor 101.

Therefore, if the change in the amount of background light is sufficiently slow compared to the change in the amount of light to be detected, the capacitor 101 will cut off the signal corresponding to the amount of background light, and the reference voltage will not reflect the amount of background light, resulting in a detection error. It was to occur. Therefore, when such a comparison device is used to detect a rapidly changing light amount signal in background light that changes rapidly, an error occurs.

(Problems to be Solved by the Invention) As mentioned above, the conventional comparison device has a configuration in which the input signal is taken in by capacitor coupling and the reference voltage is created. in the background signal,
When used to detect signals that change at high speed, there is a drawback that errors occur. The present invention was made in view of the shortcomings of the conventional comparison devices, and its purpose is to provide a comparison device capable of accurately detecting a rapidly changing signal in a rapidly changing background signal. It is to provide.

[Configuration of the Invention (Means for Solving Problems)] The present invention includes a reference voltage generation unit that divides an input signal to create a reference voltage, and a reference voltage generation unit that divides an input signal to generate a reference voltage, and a The comparator includes a bypass capacitor that bypasses the high-speed changing component of the input signal, and a comparator that compares the input signal with the reference voltage created by the reference voltage creation section.

(Function) According to this configuration, the reference voltage generation section generates a reference voltage that follows fluctuations in the input signal and that has high-speed change components removed by the bypass capacitor, that is, a reference voltage that changes quickly during comparison. A reference voltage corresponding to the background signal can be obtained, and this reference voltage is compared with the input signal.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a system for detecting a rapidly changing light amount signal using a comparison device according to an embodiment of the present invention. In this embodiment, a signal corresponding to the amount of light detected by the photodiode 1 is amplified by an inverting amplifier circuit consisting of an OP amplifier 7 and a feedback resistor 2, and is sent to a comparator 300.

In the comparator fi 300, the output signal of the inverting amplifier circuit is received at the inverting input terminal of the comparator 8, and is also provided to the reference voltage generator 30. The reference voltage generation unit 30 is a voltage dividing circuit in which resistors 3 to 5 are connected in a T-shape,
The input signal is divided to obtain a reference voltage, which is then applied to the non-inverting input terminal of the comparator 8. A bypass capacitor 6 is connected between the output terminal 30A of the reference voltage generation section 30 and the ground, and a high-speed change component included in the signal arriving from the inverting amplifier circuit to the base tP voltage generation section 30, that is, a high-speed change. The light amount component is configured to flow to the ground via the bypass capacitor 6.

In a system with such a configuration, the signal taken in from the photodiode 1 is amplified and becomes the input signal a of the comparator 300. At this time, as shown in FIG. 2, this input signal a is a signal in which rapidly changing light amount components a'l and a2 are superimposed on the background light level change. On the other hand, the reference voltage S applied to the non-inverting input terminal of the comparator 8 has a waveform obtained by removing a component that changes at high speed by the bypass capacitor 6 from the input signal a (Fig. 2 (b)).
.

Therefore, in the comparator 8, the input signal a and the reference voltage S are compared, and an output signal C as shown in FIG.

In this way, in this embodiment, the reference voltage is generated directly from the input signal a, so that it reflects the background light level. Moreover, since the fast-changing light amount component is bypassed by the bypass capacitor 6, the reference voltage S fluctuates suitably for detecting the fast-changing light amount component, making it possible to perform detection with less error.

Furthermore, it is not affected by the offset voltage fluctuation of the amplifier that occurs before the comparator 8, and moreover, the amount of background light is reduced.

Since the capacitance of the bypass capacitor 6 can be determined by considering the speed of change, the calculation can also be simplified.

[Effects of the Invention] As explained above, according to the present invention, the reference voltage is created by dividing the input signal and removing its high-speed changing components using a bypass capacitor. A reference voltage that follows a rapidly changing signal component can be obtained, and by comparing this with an input signal, a fast changing component signal can be accurately detected.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a system including an embodiment of the present invention, FIG. 2 is a waveform diagram for explaining the operation of FIG. 1, and FIG.
The figure is a diagram for explaining a conventional comparison device. 6...Bypass capacitor 8...Comparator 30...Reference voltage creation section 300...Comparison device agent Patent attorney Nori Chika Ken Shu Kanshu Sanno - Figure 2

Claims (1)

[Claims] a reference voltage creation section that divides an input signal to create a reference voltage; a bypass capacitor that bypasses a high-speed changing component superimposed on the input signal arriving at the reference voltage creation section; A comparison device comprising a comparator for comparing the voltage with a reference voltage created by the section.