JPH0648280B2 - Current detection circuit - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention is used in, for example, a tuning state indicating circuit of a radio receiver, a level meter circuit, or the like, and current detection for determining whether or not an input current is a reference value or more. The present invention relates to a circuit, and more particularly to a current detection circuit which is integrated into a monolithic integrated circuit.

[Technical background of the invention]

A conventional example of this type of current detection circuit is shown in FIG.
That is, Q _P1 and Q _P2 are PNP type transistors and form the first current mirror circuit 1, and Q _N1 and Q _N2 are NPN type transistors and form the second current mirror circuit 2. is doing. Then, the input side of the first current mirror circuit 1 is connected to the input current terminal 3, and the constant current source 4 of the reference current value I _R is connected to the input side of the second current mirror circuit 2, and both the current mirror circuits are connected. Output side 1 and output side 2 are collectively connected to the current output terminal 5.

Therefore, when the input current I _in flowing through the input current terminal 3 is smaller than the reference current value I _R , the current (= I _in ) of the transistor Q _P2 becomes smaller than the current (= I _R ) of the transistor Q _N2 . A current (I _in −I _R ) flows from the current output terminal 5. On the other hand, when I _in becomes larger than I _R , the current (I _in −I _R ) flows out from the current output terminal 5. Therefore, paying attention to the outflow current I _O from the current output terminal 5, when the input current I _in is larger than the reference current value I _R , a current change corresponding to the change in I _in can be detected.

[Problems of background technology]

By the way, when the circuit of FIG. 1 is formed on a chip of a monolithic integrated circuit, the following problems occur. That is, the constant current source 4 for the reference current is required in addition to the current mirror circuits 1 and 2 for current detection, and the pattern area becomes large. In addition, on the pattern of the current detection circuit, it is not always possible to form a circuit (for example, a constant voltage circuit) necessary to configure the constant current source 4 for the reference current near the second current mirror circuit 2. Not limited to this, in this case, it may be necessary to increase the chip size by arranging the wiring between the constant current source 4 and the second current mirror circuit 2.

[Object of the Invention]

The present invention has been made in view of the above circumstances, and provides a current detection circuit which has a simple circuit configuration and requires a small chip occupying area when a monolithic integrated circuit is formed.

[Outline of Invention]

That is, the current detection circuit of the present invention is more preferable than the first and second power supply terminals, the first conductivity type first transistor to which the emitter is connected to the first power supply terminal, and the first transistor. A second transistor of the first conductivity type, whose emitter area is large and whose base is DC-connected to the base of the first transistor, and the emitter of the second transistor are connected to the first power supply terminal. Resistor means, first and second current sources connected between the collectors of the first and second transistors and the second power supply terminal and supplying currents of the same value according to the input current from the input terminal. And is provided.

Example of Invention

An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 2 shows the basic configuration of the current detection circuit.
Reference numeral 0 is a current mirror circuit composed of PNP type transistors Q _{1 to} Q ₃ . In the current mirror circuit 20, the transistor Q ₁ has an emitter connected to the first power supply + V _c , a base and a collector connected to each other, and an input current terminal 21, and the transistor Q 1.
₂ and Q ₃ have their respective emitters connected to the power source + V _c , their respective bases connected to the base of the transistor Q ₁ by direct current, and their respective collectors connected to the first output terminal N ₁ and the second output terminal N ₂ . I'm running. On the other hand, NP
The bases of the N-type transistor Q ₄ and the NPN-type multi-emitter transistor Q ₅ are DC-connected to each other. The emitter of the transistor Q ₄ is connected to the second power source (ground potential in this example), the collector and the base are connected to each other, and the first output terminal N ₁ of the current mirror circuit 20 is connected. ing. The emitter of the multi-emitter transistor Q ₅ is grounded through the resistor R, and the collector of the multi-emitter transistor Q ₅ is connected to the second output terminal N ₂ of the current mirror circuit 20 and the output terminal 22.

In the current detection circuit, the emitter area ratio of the transistors Q _{1 to} Q ₃ is 1: 1: 1, the emitter area ratio of the transistors Q ₄ and Q ₅ is 1: A, and the current input terminal 2
The input current flowing through 1 (in this example, the current drawn to the input current source side) is represented by I _in . It was but connexion, the collector current _{I 1} flows equal to I _in each of the respective transistors _Q 1 to Q ₃ in the current mirror circuit 20, also flows collector current becomes _{I 1} to the transistor _{Q 4.} And
The collector current of the multi-emitter transistor Q ₅ is set to I ₂
The emission potential I ₂ R can be expressed by the following equation.

Here, when the relationship between the currents I ₁ and I ₂ is graphed,
As shown in FIG. Therefore, the input current I _in (= I
₁ ) becomes larger than the current I ₂ of the multi-emitter transistor Q ₅ , the current (I ₁ −I ₂ ) of the difference between the _two flows out as the output current I ₀ from the output terminal 22 to the outside. The current detection level can be displayed using the current or the output voltage of the output terminal 22.

That is, in the current detection circuit, an input current source is connected to the input side of the current mirror circuit 20, and the current of the first output terminal N ₁ of the two output terminals of the current mirror circuit 20 is used as a reference current for the transistor Q. fed to _4, the collector-base of the transistor Q ₄ mutually DC connected to the base of the multi-emitter ivy transistor Q ₅ with connecting, insert a resistor in the emitter circuit of the multi-emitter ivy transistor Q _5, the collector The current mirror circuit 20
Is connected to the second output terminal N ₂ . Therefore,
According to the above circuit, the constant current source for the reference current (FIG. 1), which is required separately from the current mirror circuit in the conventional current detection circuit, and the wiring between the constant current source and the constant current source are not required.
The area occupied on the chip can be made small when a monolithic integrated circuit is formed.

FIG. 4 shows a specific example of the current detection circuit of FIG. 2 and a specific example of a light emitting display circuit for controlling lighting of, for example, a light emitting diode by a current detection output. That is, in the current detection circuit 40, Q ₁ , Q ₂ , and Q ₃ are lateral PNP transistors for the current mirror, and the emitter area ratio is 1: 1: 1. Q ₆ is a PNP type transistor for the base current compensation of the transistor Q ₁ to Q _3. Q ₄ and Q ₅ are NPN type transistors, and their emitter area ratio is 1: 4. R _{1 to} R
₃ is a resistor inserted in the emitter circuit of the lateral PNP type transistors Q _{1 to} Q ₃ , R ₄ is a resistor inserted in the emitter circuit of the multi-emitter transistor Q ₅ , 41 is an input current terminal, and 42 is an output terminal. is there. On the other hand, in the light emitting display circuit 43, Q ₇ and Q ₈ are current amplifying NPN transistors, the collector of the transistor Q ₇ is connected to the first power source + V _c , and the base is connected to the output terminal 42. Is connected to the base of the transistor Q ₈ via a current limiting resistor R ₅ . Emitter of the transistor Q ₈ is connected to the second power supply (e.g., ground potential), the collector and the first
A light emitting diode 44 and a current limiting resistor R ₆ are connected in series between the power source + V _c . D ₁ and D ₂ are diodes connected in series between the base of the transistor Q ₇ and one end of the resistor R ₅ of the emitter circuit to limit the current of the transistor Q ₇ .

The operation of the current detection circuit 40 is similar to that described above with reference to FIG. 2, and the current I _{1 of the} transistor Q ₃ that is equal to the input current I _in is the multi-emitter transistor Q.
_When it becomes larger than the current (reference current) I _{2 of 5} , both currents I
The output current I _{0, which} is the difference between ₁ and I ₂ , is obtained. Here, the value of the resistor R ₄ connected to the emitter of the multi-emitter transistor Q ₅ is set so that I ₀ is output when I _in > 5 μA is detected, for example. The light emitting display circuit 43 uses the current I ₀ from the current detection circuit 40.
Is input, it is amplified and the light emitting diode 44 is driven to light.

In the current detection circuit of the above embodiment, the input current I _in is a negative current flowing out to the input current source.
_{If in} is a positive current flowing from the input current source, a circuit-modified current detection circuit as shown in FIG. 5 may be used. Here, Q ₅₁ and Q ₅₂ are NPN transistors, Q ₅₃ is an NPN type multi-emitter transistor, Q ₅₄ and Q ₅₅ are PNP transistors, and R _{51 to} R ₅₃ are resistors, and the transistors Q _{51 to} Q ₅₃ and The resistor R ₅₃ forms the current mirror circuit 50. The input current from the input current terminal 51 is I _in , the currents of the transistors Q ₅₁ , Q ₅₂ , Q ₅₄ , and Q ₅₅ are I ₁ (= I _in ), and the current of the transistor Q ₅₃ is I ₂ ,
If the output current from the output terminal 52 is represented by I ₀ , the relationship between I ₀ and I _in is the same as _in the circuit of FIG.

〔The invention's effect〕

As described above, according to the current detection circuit of the present invention, the circuit configuration is simplified, and there is an advantage that the chip occupying area is small when the monolithic integrated circuit is formed.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a conventional current detection circuit, FIG. 2 is a circuit diagram showing an embodiment of the current detection circuit according to the present invention, and FIG.
2 is a characteristic diagram showing operation characteristics of the circuit of FIG. 2, FIG. 4 is a circuit diagram showing a specific example of the circuit of FIG. 2, and FIG. 5 is a circuit diagram showing another embodiment of the present invention. . _{Q 1 ~Q 5, Q 51 ~Q} 55 ...... transistor, 20, 50
...... Current mirror circuit 21,51 …… Input current terminal.

Claims (2)

[Claims] 1. A first conductivity type first transistor having first and second power supply terminals, an emitter connected to the first power supply terminal and a base and a collector connected to the first power supply terminal, and the first transistor. A second transistor of a first conductivity type having a large emitter area and a base connected to the base of the first transistor, and a resistance means for connecting the emitter of the second transistor to the first power supply terminal. And first and second current sources connected between the collectors of the first and second transistors and the second power supply terminal and supplying currents of the same value according to the input current from the input terminal. Be equipped with
The first and second current sources include third to fifth transistors of the second to fifth conductivity type, the emitters of which are connected to the second power supply terminal and the bases of which are connected to each other to form a current mirror circuit. The base and collector of the third transistor are connected to the input terminal, and the collectors of the fourth and fifth transistors are connected to the collectors of the first and second transistors, respectively. The first and second current sources are configured to output the detected output current from the collector of the second transistor, and the reference current, which is the current of the first current source, and the second transistor From the flowing direction of the detected output current determined by the magnitude relationship with the collector current,
A current detection circuit comprising a detection means for knowing a range of a current value of the input current. 2. A first and a second power supply terminals, a first conductivity type first transistor having an emitter connected to the first power supply terminal, and an emitter area larger than that of the first transistor. And a second transistor of the first conductivity type whose base is connected to the base of the first transistor, resistance means for connecting the emitter of the second transistor to the first power supply terminal, and the first transistor. A current mirror that allows the same current to flow in both the input-side path connected between the collector of the transistor and the second power supply terminal and the output-side path connected between the collector of the second transistor and the second power supply terminal The current mirror circuit is configured such that the emitters of the third and fourth transistors of the second conductivity type are connected to the second power supply terminal, respectively.
The bases and collectors of the transistors are connected to each other, the bases of the third and fourth transistors are connected to each other, and the collectors of the third and fourth transistors are connected to the collectors of the first and second transistors, respectively. On the other hand, there is further provided a fifth transistor of the first conductivity type which is diode-connected and whose base is connected to the bases of the first and second transistors and whose emitter is connected to the first power supply terminal. The base and collector of the diode-connected fifth transistor are connected to the input terminal, and the collector outputs of the third and fourth transistors are currents to the collector side of the first and second transistors, respectively. It serves as a power source and takes out the detected output current from the collector of the second transistor. A detection means for knowing the range of the current value of the input current from the direction in which the detected output current flows, which is determined by the magnitude relationship between the reference current, which is the collector output current of the star, and the collector current of the second transistor. A current detection circuit characterized in that