JPH09274057A - Comparator circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a miniaturized comparator circuit as a configuration that enables an IC without external parts. [Structure] A chopper comparator 1, a DC component extraction circuit 2, a switching circuit 3, and a control circuit 4 are provided. Specifically, the switches S1 and S3 are closed for a certain period of time, and the DC voltage of "input voltage Vin-reference voltage Vref" is sampled in the capacitor 6. Then switch S1, S
3 is opened and the switch S2 or the switch S4 is closed for a certain period of time to generate the input voltage V2 by increasing or decreasing the input voltage Vin by the hysteresis voltage Vhis. Then, the DC voltage V1 extracted by the DC component extraction circuit 2 and this input voltage V1
2 is compared with the chopper comparator 1, and the input voltage V1
The output voltage Vout of H or L level is output from the chopper comparator 1 depending on whether the input voltage V2 is large or small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a comparator for returning a signal having noise when an analog mobile phone is demodulated to an original signal.

[0002]

2. Description of the Related Art In an analog mobile phone or the like, when data is modulated, transmitted, received, and demodulated, a signal thereof passes through a large number of circuits, so that an arbitrary DC (direct current) offset is added to cause noise. Is mixed in. For this reason, a DC-offset-type hysteresis comparator circuit is used to restore the signal mixed with noise to the original data (rectangular wave). Conventionally, as a comparator circuit of this type, there is a technique as shown in FIG. In this comparator circuit, as shown in FIG. 3, an input terminal 100 for an input voltage Vin is connected to one input terminal of a comparator 102 via a coupling capacitor 101. The resistors 111 to 114 are connected in series to the constant voltage source 110, and the connection point with the resistors 112 and 113 is connected to the output side of the capacitor 101 via the resistor 115. Also, the connection point of the resistors 111 and 112 and the resistors 113 and 11
Each of the four connection points is connected to the other input end of the comparator 102 via the switches S5 and S6. With this configuration, the input voltage Vin having a DC offset
Is coupled by the capacitor 101 and its D
The C offset is removed. And the capacitor 10
When a predetermined voltage Vref is applied to the input voltage Vin from 1,
It is input to one input terminal of the comparator 102. Also,
At the other input end of the comparator 102, a switch S5,
By the opening / closing control of S6, a voltage of "predetermined voltage Vref + hysteresis voltage Vhis" or "predetermined voltage Vref-hysteresis voltage Vhis" is input.
As a result, the input voltage Vin in which noise is mixed is returned to the rectangular wave output voltage Vout.

[0003]

However, in the above-mentioned conventional comparator circuit, the coupling capacitor 101 is provided between the input terminal 100 of the input voltage Vin and the input terminal of the comparator 102. Therefore, there are the following problems. For the input voltage Vin having a high frequency component, the capacitance of the capacitor 101 is several tens p
Can be set to F. Therefore, the capacitor 1
The entire comparator circuit including 01 can be integrated into an IC. However, when the input voltage Vin has a low frequency component of several kHz, the capacitance of the capacitor 101 must be set to the order of μF. Therefore, the capacitor 101 becomes large and the capacitor 1
It becomes impossible to embed 01 in the IC. Therefore, the capacitor 101 must be externally attached to the IC, and the pin terminal for the capacitor 101 must be provided on the IC, which causes a problem that the entire comparator circuit becomes complicated and large. It was

The present invention has been made to solve the above problems, and an object of the present invention is to provide a miniaturized comparator circuit as a configuration that enables an IC without external parts.

[0005]

In order to solve the above-mentioned problems, a comparator circuit according to the invention of claim 1 comprises a DC voltage extraction unit capable of extracting a DC voltage component from an input voltage, and the above-mentioned input voltage, positive A switching unit capable of switching and outputting either a constant voltage or a negative constant voltage, a power storage unit that stores the voltage from the switching unit, a storage voltage of the power storage unit, and a DC voltage component of the DC voltage extraction unit. The output voltage of high level is output when the storage voltage is larger than the DC voltage component, and the output voltage of low level is output when the storage voltage is smaller than the DC voltage component. After the comparison unit capable of holding the level and the input voltage are output from the switching unit, the positive or negative constant voltage is output from the switching unit based on the level held by the comparison unit. And the configuration and a control unit for actuating the serial comparison unit.

According to a second aspect of the present invention, in the comparator circuit according to the first aspect, the control unit controls the negative constant voltage from the switching unit when the level held by the comparison unit is high. When the level held by the comparison section is low, the negative constant voltage is output from the switching section.

According to the first aspect of the present invention, when the input voltage is input to the DC voltage extraction unit, the DC voltage component is extracted and input to the comparison unit. Further, the input voltage output from the switching unit is stored in the power storage unit by the control unit.
In this state, when the positive or negative constant voltage is output from the switching unit, the voltage obtained by adding the positive or negative constant voltage to the input voltage is accumulated in the power storage unit. As a result, the voltage stored in the power storage unit is compared with the DC voltage component in the comparison unit. When the stored voltage is higher than the DC voltage component, a high level output voltage is output from the comparison unit, and when the stored voltage is lower than the DC voltage component, a low level output voltage is output. Further, the comparison unit holds the level. Then, under the control of the control unit, when the input voltage is output again from the switching unit, the input voltage is accumulated in the power storage unit, and thereafter, based on the level held by the comparison unit, a positive or negative constant voltage is generated. It is output from the switching unit.

According to the second aspect of the present invention, when the level held by the comparison unit is high, a negative constant voltage is output from the switching unit under the control of the control unit, so that the storage unit stores it. , A voltage lower than the input voltage by a constant voltage is accumulated. Further, when the level held by the comparison unit is low, a positive constant voltage is output from the switching unit, so that a voltage higher than the input voltage by a constant voltage is stored in the power storage unit.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a comparator circuit according to an embodiment of the present invention. As shown in FIG. 1, the comparator circuit of this embodiment includes a chopper comparator 1 (comparing unit), a DC component extracting circuit 2 (DC voltage extracting unit), a switching circuit 3 (switching unit), and a control circuit 4.
(Control unit) and capacitor 6 (power storage unit).

The chopper comparator 1 is a two-input one-output comparator, amplifies the difference voltage between the voltages V1 and V2 input from the respective input terminals, and outputs this as the output voltage V
It is an element that outputs to the output terminal 11 as out.

The DC component extraction circuit 2 is connected between the input terminal 10 and one input end of the chopper comparator 1, and extracts the DC voltage component from the input voltage Vin offset with the DC voltage component. Is an input voltage V1 and is input to one input end of the chopper comparator 1.

The switching circuit 3 is a circuit for switching the input voltage V2 input to the other input terminal of the chopper comparator 1. Specifically, a resistor 5 is provided between the reference voltage source 5 and ground.
0 and resistors 51 to 53 having the same resistance value are connected in series. The switch S2 is connected to the connection point between the resistors 50 and 51, the switch S3 is connected to the connection point between the resistors 51 and 52, and the switch S4 is connected to the connection point between the resistors 52 and 53. There is. A switch S1 is connected between the input terminal 10 and the other input terminal of the chopper comparator 1. The capacitor 6 is a sampling capacitor, and is connected between the output end of the switch S1 and the connection point of the switches S2 to S4.

The control circuit 4 is a circuit for controlling the chopper comparator 1 and the switching circuit 3 based on the clock signal CLK. Specifically, the switches S1 and S3 of the switching circuit 3 are closed for T0 time (hereinafter referred to as "on state"), and this on state is repeated at T1 time intervals to sample the input voltage Vin. And
When the previous output voltage Vout is at the L level (low level), after opening the switches S1 and S3, the switch S2 of the switching circuit 3 is turned on for the time T2 to output the output voltage Vou.
When t is at H level (high level), the switch S4 is turned on for T2 time. At this time, the result of the output voltage Vout when the switch S2 or the switch S4 is turned on is held in the chopper comparator 1, and as described above, the switch S to be turned on next according to this result.
2 or switch S4 is determined.

Next, the operation of the comparator circuit of this embodiment will be described. FIG. 2 is a time chart of each signal during the operation of the comparator circuit of this embodiment. When the input voltage Vin having the waveform shown in (f) of FIG. 2 is input from the input terminal 10 of FIG.
It is input to the component extraction circuit 2 and the switching circuit 3. And
A DC voltage component is extracted from the input voltage Vin input to the DC component extraction circuit 2, and this DC voltage component is input voltage V1.
Is input to one input terminal of the chopper comparator 1. At this time, by the control of the control circuit 4, (c) of FIG.
As shown in FIG. 5, when the switches S1 and S3 of the switching circuit 3 are turned on, the input voltage Vin is input to the chopper comparator 1 via the switch S1, and the direct current “input voltage Vin−reference voltage Vref” is input. Is applied to the capacitor 6. As a result, “S” in FIG.
As shown in, the input voltage Vin is sampled by the capacitor 6. And, although not shown in FIG.
Assuming that the output voltage Vout when the switch S2 or the switch S4 is turned on before the sampling is at the L level, after the above sampling operation is completed, the control circuit 4 controls the output voltage Vout of FIG. As shown in (d), after the switches S1 and S3 are turned off, the switch S2 is turned on. As a result, “reference voltage Vref + hysteresis voltage Vhis” is applied to the capacitor 6. Here, until just before the switch S2 is turned on, "input voltage Vin-reference voltage Vref
Is held in the capacitor 6, the switch S
When 2 is turned on, "reference voltage Vref + hysteresis voltage Vhis" is added to this voltage. As a result, as shown in (g) of FIG.
2 is DC "input voltage Vin + hysteresis voltage Vhis"
Is input to the chopper comparator 1. That is, the input voltage V2 obtained by applying a positive offset to the final DC voltage of the sampled input voltage Vin by the hysteresis voltage Vhis is input to the chopper comparator 1. This state is "H" in FIG.
As shown in "C", after being held for about T2 time, the input voltage V2 and the input voltage V1 are compared by the control of the chopper comparator 1 of the control circuit 4 at the time indicated by the point P1. The input voltage V2 is the input voltage V1
Therefore, the output voltage Vout at the L level is output from the chopper comparator 1 and the comparison result is held.

Thereafter, the switch S2 is turned off, the switches S1 and S3 of the switching circuit 3 are turned on again, and the input voltage Vin is sampled. The comparison result held in the chopper comparator 1 is L
Since it is at the level, the switch S2 is turned on again. As a result, similarly to the above, the sampled voltage is positively offset by the hysteresis voltage Vhis, which is “input voltage Vin + hysteresis voltage Vhi”.
The input voltage V2 of "s" is input to the chopper comparator 1 and compared with the input voltage V1 at the time indicated by the point P2. In this case, the input voltage V2 is the input voltage V1
Therefore, the output voltage Vout of H level is output from the chopper comparator 1 and the comparison result is held.

After the switch S2 is turned off, the switches S1 and S3 are turned on again, and the input voltage Vin is sampled. Then, since the comparison result held in the chopper comparator 1 is at the H level, the switch S4 is turned on as shown in (e) of FIG. As a result, the "reference voltage Vre
f-hysteresis voltage Vhis "is applied to the capacitor 6. Here, "input voltage Vin-reference voltage Vref" is held in the capacitor 6 until just before the switch S4 is turned on. Therefore, when the switch S4 is turned on, "reference voltage Vref-hysteresis voltage" is added to this voltage. Vhis "will be added. As a result, as shown in (g) of FIG. 2, the input voltage V2 becomes a direct current "input voltage Vin-hysteresis voltage Vhis" and is input to the chopper comparator 1. That is, the input voltage V2 obtained by applying a negative offset to the final voltage of the sampled input voltage Vin by the hysteresis voltage Vhis is input to the chopper comparator 1. This state is maintained for approximately T2 hours, as shown by "HC" in FIG. 2B, and then at the time indicated by the point P3.
The input voltage V2 is compared with the input voltage V1. Since the input voltage V2 is lower than the input voltage V1, the H level output voltage Vout is output from the chopper comparator 1 and the comparison result is held.

Thereafter, the switches S1 and S of the switching circuit 3 are
3 is turned on again, the input voltage Vin is sampled, and the comparison result held in the chopper comparator 1 is at the H level, so the switch S4 is turned on again. As a result, similarly to the above, the input voltage V2 of "input voltage Vin-hysteresis voltage Vhis" obtained by applying a negative offset to the sampled voltage by the hysteresis voltage Vhis is input to the chopper comparator 1 and the P4 point. The input voltage V1 is compared at the time indicated by. In this case, since the input voltage V2 is higher than the input voltage V1, the L-level output voltage Vout is output from the chopper comparator 1 and the comparison result is held.

As described above, the sampling in the capacitor 6 and the comparison in the chopper comparator 1 are repeated, and the rectangular wave output voltage Vout as shown in FIG. 2H can be obtained from the input voltage Vin.

As described above, according to the comparator circuit of this embodiment, the rectangular-wave output voltage Vout is generated by using the sampling capacitor 6 for storing the DC voltage without using the coupling capacitor. Therefore, even if the input voltage Vin is a low frequency, the capacitance of the capacitor 6 can be set in the order of several tens of pF, and as a result, it is possible to achieve high integration of the entire circuit incorporating the capacitor 6 and external parts. It has become possible to manufacture small comparator circuits that do not require pins or pin terminals. Moreover, the input voltage Vin having an arbitrary offset DC voltage V1 can be compared with a certain hysteresis.

[0020]

As described in detail above, according to the comparator circuit of the present invention, the power storage unit is not used for coupling the input voltage, but is used for so-called sampling for storing DC voltage. In addition, the capacity of the power storage unit can be set to a small value regardless of the low-frequency input voltage, and as a result, it is possible to achieve high integration of the entire circuit in which the power storage unit is incorporated and to reduce the size of the external components and pin terminals that are unnecessary. There is an excellent effect that a comparator circuit can be provided.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a comparator circuit according to an embodiment of the present invention.

FIG. 2 is a time chart diagram of each signal during operation of the comparator circuit of FIG.

FIG. 3 is a circuit diagram showing a comparator circuit according to a conventional example.

[Explanation of symbols]

1 ... Chopper comparator, 2 ... DC component extraction circuit, 3 ... Switching circuit, 4 ... Control circuit,
5 ... Reference voltage source, 6 ... Capacitor, S1 to S
4 ... Switch, Vin ... Input voltage, Vout
..Output voltage, Vref ... Reference voltage, Vhi
s ... Hysteresis voltage.

Claims (2)

[Claims] 1. A DC voltage extraction unit capable of extracting a DC voltage component from an input voltage, a switching unit capable of switching and outputting any one of the input voltage, a positive constant voltage, and a negative constant voltage, and the switching unit. Comparing the stored voltage of the storage unit and the DC voltage component of the DC voltage extraction unit, a high-level output voltage when the stored voltage is larger than the DC voltage component. After outputting the output voltage and outputting a low level output voltage when the stored voltage is smaller than the DC voltage component, and outputting the input voltage from the switching unit and the comparison unit capable of holding the level, A comparator circuit comprising: a control unit that outputs the positive or negative constant voltage from the switching unit and operates the comparison unit based on the level held by the comparison unit. 2. The comparator circuit according to claim 1, wherein the control unit causes the switching unit to output the negative constant voltage when the level held by the comparison unit is a high level. A comparator circuit, wherein the negative constant voltage is output from the switching unit when the level held by the unit is low.