JP2597302Y2 - Comparison circuit - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a comparison circuit.
The present invention relates to a comparison circuit that monitors a power supply voltage.

[0002]

2. Description of the Related Art FIG. 4 shows a circuit diagram of a comparator. The NPN transistors Q ₁ and Q ₂ are comparison transistors, and the collectors of the NPN transistors Q ₁ and Q ₂ are PNP transistors Q ₃ and Q forming a current mirror circuit.
₄ collectors are connected. PNP transistors Q ₃ ,
A voltage Vcc is applied to the emitter of Q _4. Also, N
The emitters of the PN transistors Q ₁ and Q ₂ are both NPN
The base of the NPN transistor Q ₁ is connected to the constant current circuit 1 consisting of transistors Q _5, Q ₆ is connected to the connection point of the resistors R _1, R ₂ for dividing the voltage Vcc, the base of NPN transistor Q ₂ is a reference voltage source The resistor R ₃ that constitutes 2
And zener diode Dz. The base voltages of the transistors Q ₁ and Q ₂ are compared according to the ratio of the current flowing through the transistor Q ₁ and the transistor Q _2, and the output transistor P is determined according to the comparison result.
NP transistor Q ₇ is operated.

Here, the constant current circuit 1 includes a transistor Q ₅
Using a constant voltage V _BE between the base and emitter to turn on the transistor Q _6, and holds a current I ₁ constant was getting a constant current I ₂ to a current I ₀₁ and ₀ times n by the transistor Q _6.

As a conventional constant current circuit for supplying a bias current used in this type of comparator, a circuit as shown in FIG. 5 has been used.

[0005] Figure 5 resistor R ₁ circuit described above for (A), the resistance R ₄ correspond to R ₂ provided transistor Q
₅ and resistors R ₅ and R ₆ that determine the current amplification factor
₆ , which has a voltage-current characteristic with a slow rise as shown by the broken line in FIG. 2 because the current amplification factor cannot be large.

The circuit shown in FIG. 5B has a resistor R ₇ ,
An NPN transistor Q ₈ having a base connected to a connection point of R ₈ , a resistor R ₇ and a resistor R ₈ is connected in series, and a voltage V
The cc is applied, a configuration obtained by connecting the base of the NPN transistor Q ₉ to which the voltage Vcc is applied between the collector and the emitter and collector of NPN transistor Q _8, relatively since the current amplification factor, can be increased, a point in FIG. 2 As shown by the dashed line, the rise of the voltage Vcc allows the rise of the current to be slightly faster than that of the circuit shown in FIG. But,
When the voltage Vcc increased, the current tended to decrease.

[0007]

However, since the conventional constant current circuit cannot obtain a large current amplification, the rise of the voltage-dependent characteristic is slow. As shown by the broken line in FIG. However, there was a problem that it could not be supplied.

In addition, when the rise of the voltage-dependent characteristic is to be improved, there is a problem that the current decreases at the time of high voltage and a constant current cannot be secured, as shown by a dashed line in FIG.

The present invention has been made in view of the above points, and has a stable voltage monitoring operation regardless of the level of the power supply voltage.
The purpose is to provide a comparison circuit that can perform the operation
I do.

[0010]

According to the present invention, a power supply voltage is reduced.
A reference voltage generating means for generating a reference voltage;
Voltage dividing means for dividing the voltage and the voltage generated by the reference voltage generating means.
The reference voltage is compared with the divided voltage divided by the dividing means.
And an output corresponding to the magnitude relationship between the divided voltage and the reference voltage.
A comparison circuit having a comparison means for outputting a signal;
A current amplifying a first current supplied to the voltage dividing means;
Current amplification means and the first current amplification means.
Second current amplifying means for amplifying the width of the second current;
Amplifying the third current amplified by the second current amplifying means
A third current amplifying means for setting a driving current for the comparing means
And

[0011]

According to the present invention, the first to third current amplifier circuits are provided.
The amplified current is used as the drive current of the comparing means.
This allows a stable comparison regardless of the power supply voltage level.
Since the drive current can be supplied to the stage, the comparison means operates stably.
Can be operated, and when the power supply voltage rises.
The rise of the drive current can be sharp, and the comparison means can be driven instantly.
Power supply voltage can be monitored quickly.
Swell.

[0012]

FIG. 1 is a circuit diagram showing an embodiment of the present invention. In this embodiment, is a description of a constant current circuit that is built in a comparator and generates a bias current? In the figure,
Reference numeral 11 denotes a constant current circuit unit. The constant current circuit section 11 includes current amplifier circuits 11a and 11b and a current mirror circuit 11c.

[0013] current amplification circuit 11a NPN transistor Q ₁₁ becomes a control transistor, consisting of NPN transistors Q _12, resistors R _13, R _14, R ₁₅ serving as an output transistor. The base of the NPN transistor Q ₁₁ is the power supply voltage Vcc via a resistor R ₁₁ and resistor R ₁₂ is connected to the collector via a resistor R ₁₃ together with the applied. The emitter of NPN transistor Q ₁₁ is grounded through a resistor R _14.

[0014] In addition, the resistor R ₁₃ and the NPN transistor Q ₁₁
Connection point between the collector of which is connected to the base of NPN transistor Q _12. The emitter of NPN transistor Q ₁₂ is grounded through a resistor R _15, the collector current amplifying circuit 1
1b.

The current amplifier circuit 11b PNP transistor Q ₁₃ becomes a control transistor, the PNP transistor Q ₁₄ becomes the output transistors, consisting of resistors _{R 16, R 17, R 18} . The emitter of the PNP transistor Q ₁₃ is the power supply voltage Vcc is applied through a resistor R _17, preceding the current amplifier circuit 1 with its collector is connected to the base via a resistor R ₁₆
It is connected to the collector of the transistor Q ₁₂ which is an output of 1a. Connection point between the resistor R ₁₆ the collector of the PNP transistor Q ₁₃ is connected to the base of PNP transistor Q _14. PNP transistor power supply voltage Vcc to the emitter via a resistor R ₁₈ of Q ₁₄ is applied, the collector is connected to the current mirror circuit 11c.

The current mirror circuit 11c includes NPN transistors Q ₁₅ and Q ₁₆ and resistors R ₁₉ and R ₂₀ . The collector of the NPN transistor Q ₁₅ is the base of the PNP transistor Q ₁₅ and the PNP transistor Q ₁₆ is connected with the collector of the PNP transistor Q ₁₄ as an output of the current amplifier circuit 11b is connected. The emitter of the PNP transistor Q ₁₆ is grounded through a resistor R _20. The collector of the PNP transistor Q ₁₆ is connected to the comparison circuit 12 becomes a constant current output terminal.

The comparison circuit section 12 includes PNP transistors Q ₁₇ and Q ₁₈ forming a current mirror circuit, and NPN transistors Q ₁₉ and Q ₂₀ forming a comparison section. The base of the PNP transistor Q ₁₉ is connected to the connection point between the resistor R ₁₁ resistor R _12, the base of the PNP transistor Q ₂₀ is connected to a reference voltage generating circuit 13. Reference voltage generating circuit 13 consists of resistors R ₂₁ and zener diode D _1, resistors R ₂₁
The Zener diode D ₁ is connected between ground and the power supply voltage Vcc in series, and outputs a reference voltage from a connection point,
It is applied to the base of the transistor Q _20. The collector of the NPN transistor Q _19, Q ₂₀ is the emitter of the PNP transistor Q _17, the PNP transistor Q ₁₇ is connected to the collector of Q _18, Q ₁₈ constituting respectively Karen mirror circuit supply voltage Vcc is applied.

The emitters of NPN transistors Q ₁₉ and Q ₂₀ are both connected to the collector of NPN transistor Q ₁₆ forming current mirror circuit 11c.

[0019] The collector of the NPN transistor Q ₁₉ is connected to the base of the PNP transistor Q ₂₁ serving as an output transistor, the power supply voltage Vcc is applied to the emitter of the PNP transistor Q _21, the collector is connected to the drive stage as an output terminal Is done. Next, the circuit operation will be described.
Supply when the voltage Vcc begins to rise from 0 (V) current I ₁₁ flows, the transistor Q _11, Q ₁₂ are turned on, a current I ₁₂ flows. Current I ₁₂ by the transistor Q _15, Q ₁₆ is turned on by a current I ₄ flows as the bias current of the comparator unit 12.

[0020] At this time, the current through the transistor Q ₁₂ I
₁₁ is amplified to a current I ₁₂ multiplied by n ₁₁ , and the current I ₁₂
Changes the current I ₁₂ to n ₁₃ / n ₁₂ by the transistors Q ₁₃ and Q _14.
It is amplified by multiplying the current I _13. Therefore, it is possible to start up the current I ₁₄ in response fast rise of the power supply voltage Vcc as shown by the solid line in FIG. Therefore, the voltage V
A constant voltage can be supplied even when cc is at a low voltage.

As described above, the two-stage current amplifier circuits 11a, 1
By performing the current amplification by 1b, a constant current can be supplied to the comparing section 12 even at a low voltage, and the operation of the comparing section 12 can be stabilized even at a low voltage.

When the voltage rises, the current amplifying circuit 11
a, the output current is output via the
It is hardly affected by cc, and a constant current can be continuously supplied as shown by a solid line in FIG.

FIG. 3 is a circuit diagram of another embodiment of the present invention. In the figure, the same components are denoted by the same reference numerals, and description thereof will be omitted. In the present embodiment, the transistor of FIG. 1 is realized by a transistor of the opposite polarity, the resistors R ₂₁ and R ₂₂ are provided corresponding to the resistors R ₁₁ and R ₁₂ , and the current amplifying circuit 21 a is an NPN transistor of the current amplifying circuit 11 a. Q ₁₁ , Q ₁₂ ,
PNP transistors Q ₃₁ and Q ₃₂ and resistors R ₃₃ , R ₃₄ and R ₃₅ are provided corresponding to the resistors R ₁₃ , R ₁₄ and R ₁₅ , and the current amplifying circuit 21 b is composed of PNP transistors Q ₁₃ and Q ₁₃ of the current amplifying circuit 11 b. ₁₄ , the resistors R ₁₆ , R ₁₇ , R ₁₈
Transistors Q _33, Q _34, and a resistor _{R 36, R 37, R 38} , current mirror circuit 21c is a current mirror circuit 1
1c NPN transistors Q ₁₅ and Q ₁₆ , resistors R ₁₉ and R ₂₀
And the PNP transistors Q ₃₅ and Q ₃₆ and the resistors R ₃₉ and R _40.
Transistors Q ₁₇ and Q ₁₈ , NPN transistors Q ₁₉ and Q
So as to correspond to the _20, NPN transistor Q _37, Q _38, PNP
It comprises transistors Q ₃₉ and Q ₄₀ , and is provided with a PNP transistor Q ₄₁ corresponding to an NPN transistor Q ₂₁ which is an output transistor.

The current characteristics of this embodiment are substantially the same as those shown by the solid lines in FIG. 2, and have the same effects as those of the embodiment of FIG.

[0025]

According to the present invention, first to third current amplifications are provided.
The current amplified by the circuit is compared with the drive current of the comparison means.
To ensure stable operation regardless of the power supply voltage level.
Drive current can be supplied to the comparison means, making the comparison means stable
And the power supply voltage rises.
The rise of the drive current at the time of
At the same time, and monitor the power supply voltage quickly.
It has features such as

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention.

FIG. 2 is a voltage-current characteristic diagram of one embodiment of the present invention.

FIG. 3 is a circuit diagram of another embodiment of the present invention.

FIG. 4 is a circuit diagram of a conventional example.

FIG. 5 is a configuration diagram of a main part of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Constant current circuit part 11a, 11b Current amplifier circuit 11c Current mirror circuit 12 Comparison circuit part

Claims (1)

(57) [Scope of request for utility model registration] 1. A reference voltage generator for generating a reference voltage from a power supply voltage.
Voltage generating means; voltage dividing means for dividing the power supply voltage;
The reference voltage generated by the reference voltage generating means and the voltage dividing means
The divided voltage is compared with the divided voltage, and the divided voltage and the reference voltage are compared.
Comparing means for outputting an output signal according to the magnitude relationship with the pressure;
In the comparison circuit having: a first current that amplifies the first current supplied to the voltage dividing means.
(1) a current amplifying means, and a second current amplified by the first current amplifying means.
A second current amplifying means for amplifying the third current amplified by the second current amplifying means amplifying
A third current amplifying means for setting a driving current for the comparing means
A comparison circuit comprising: