JPH0229810A - Constant current/constant voltage circuit - Google Patents

Abstract

PURPOSE:To stably supply a constant voltage and a constant current to a load independently of the characteristics of transistors(TRs) and the variation of power supply voltage by forming the 1st and 2nd feedback loops in the 1st and 2nd TRs having different capacity and stabilizing the constant current sources and common base potential of the 1st and 2nd TRs. CONSTITUTION:The bases of the 1st and 2nd TRs 7, 8 having different driving capacity are connected in common, the 3rd and 4th TRs 11, 12 which are different kind from the TRs 7,8 are connected to the collectors of respective TRs 7, 8 form the 1st and 2nd feedback loops and the constant current source of collector currents I1, I2 in th 1st and 2nd TRs 7, 8 and the base potential values of the TRs 7, 8 are controlled so that the constant current and constant voltage can be extracted to the load. Consequently, the collector currents and the base voltages of the TRs 7, 8 are stabilized respectively at fixed values and the fixed values can be maintained in spite of variation in the power supply voltage or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a constant current/constant voltage circuit that supplies constant current and constant voltage to a load.

[Conventional technology]

Figure 6 shows, for example, "Analog integrated circuit" pages 119-12.
0 (published by Kindai Kagakusha on September 15, 1975). In the figure, 1 is a positive voltage power supply, 2 is a negative voltage power supply, 3 is a load, and 4 and 5 are loads. A transistor controls the current to 3, and 6 is a resistor.

Next, the operation will be explained. If the voltage between the base and emitter of the transistor 4 is vBE and the value of the resistor 6 is r6, then the current 11 flowing through the resistor 6 is 11=
(V VBE) / r6. From Figure 6, the base-emitter voltage VBE of transistors 4 and 5
are equal, so if the transistors are the same, the current I2 flowing through the load 3 will be I2 = 11.

In addition, the driving ability of transistor 5 is
If the transistor 5 is constructed by arranging N transistors 4a identical to the transistor 4 and connecting their emitters, collectors, and bases as shown in FIG. I2-1! It becomes X11.

In this way, in this constant current circuit, VB of transistor 4
Using E as a reference voltage, the transistor 5 supplies a constant voltage application 2 corresponding to the constant voltage application 1 to the load 3.

[Problem to be solved by the invention]

Since the conventional constant current circuit is configured as above,
Constant voltage construction 1 is the characteristic of transistor 4.

There was a problem that the resistor 6 easily fluctuated due to changes in the resistor 6, changes in the power supply voltage, etc., and the value of the resistor 6 became very large when the current of the resistor 1 was low.

This invention was made in order to solve the above-mentioned problems, and it is possible to reduce the influence of circuit element characteristics and power supply voltage fluctuations on the constant current value flowing through the transistor, and also to reduce the influence of changes in the power supply voltage and the constant current flowing through the transistor. The purpose of this invention is to obtain a constant current/constant voltage circuit that can also provide constant voltage.

[Means to solve the problem]

The constant current/constant voltage circuit according to the present invention has first and second circuits having different driving capacities. The base of the second two transistors is common, and the collector of each transistor is connected to the third transistor of a different type. The fourth transistor is connected to the first transistor.
forming a second feedback loop; A constant current source for the collector current If + I2 of the second transistor and the first transistor. controlling the potential of the pace of the second transistor;
It is designed to take out constant current and constant voltage to the load.

[For production]

First in this invention. The second feedback loop connects the first. A constant current source for each collector current flowing through the second transistor and the first transistor. By applying feedback control to the base potential of the second transistor, the collector current and the first
．． The pace voltage of the second transistor becomes stable at a certain constant value, and operates to maintain a constant value even when the power supply voltage changes.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, numerals 1 to 3 are the same or equivalent positive voltage power source, negative voltage power source, and load as in the conventional device described above. 7.8
are NPN first transistor and second transistor, 9 to 13 are PNP transistors, and 11 of these are PNP transistors.
12 is a fourth transistor forming a second feedback loop, and 14 to 19 are resistors. One end of the resistor 14 is connected to the emitter of a second transistor 8 which has n times the driving ability of the first transistor 7, and the other end is connected to the emitter of the transistor 7, and this second connection point If the voltage between the emitters of the first and second transistors 7.8 and the first connection point (2) is VAB, then the relationship between VAB and the collector current Ic of the transistors 7.8 is as shown in Figure 2. It becomes a characteristic curve.

Next, transistor 9, resistor 16 and transistor 1
0 and resistor 17, respectively. second transistor 7
．． 8, and these constant current sources are controlled by the emitter of a third transistor 11 connected to the transistor 9,100 pace, whose pace is connected to the collector of the first transistor T. , and this forms the first feedback loop.

Furthermore, the base of the fourth transistor 120 is connected to the collector of the second transistor 8 to form a current amplification circuit, and the collector of the fourth transistor 12 is connected to the connection point
By supplying a current to , the second feedback loop is formed, and the potential at the connection point (2) is also determined.

Next, the operation will be explained. In FIG. 1, transistors 9 and 10 and resistors 16 and 17 that constitute a constant current source are shown.
are the same, the first and second transistors 7
．． The collector current 11+I2 of 8 becomes equal. From Figure 2, 1. The reason why the collector currents of the second transistor 8 coincide with each other is that the two characteristic curves Q1. There is only one point where Q2 intersects, and vAB=vAB1. ! 1=I2=Ic
1, the circuit of FIG. 1 is stable.

1st. In the second feedback loop, for example, when the potential at the connection point 0 changes to the positive (-1-1 side), the potential at the collectors of the first and second transistors 7.8 initially changes to the negative H side; Due to the first feedback loop, the voltage changes to the -H side.

The second feedback loop, in which the impedance seen from the collector side of the second transistor 8 is higher than the impedance seen from the collector side of the first transistor 7, and has a smaller degree of feedback than the first feedback loop, When the collector of transistor 12 changes to the + side, the potential of the collector of the transistor 12 changes to the H side, and the transistor 12 operates to return the potential of the connection point (2) to its original state.

Utilizing such constant current and constant voltage characteristics, the emitter of the third transistor 11 is connected to the transistor 13. resistance 1
8, etc., and supplies constant current and constant voltage to the load 3.

Note that in the above embodiment, the first. second transistor 7.8
The same transistors 9, 10 and resistor 1 are used as a constant current source.
6.17, but it may be different. For example, in FIG.
If there is twice the driving capacity and the value of the resistor 17 is 1/1602, then the collector current II * I2 is Iz = 2X
It can be That is, as shown in the characteristic curve of FIG. 3, vAB=vAB1111=IC1,
It is stable at only one point on each characteristic curve where l2=Ic2, and the same effect as the above embodiment is achieved.

Further, although FIG. 1 shows the case where the fourth transistor 12 is PNP, it may be NPN, and in this case, as shown in FIG. Transistors 21 and 22 are replaced between the emitter of this transistor 20 and the power supply.
．． 23 is connected to perform circuit conversion, and from the collector of the second transistor 8 and the different type of transistor 22, the connection point ■
By supplying current to , the same effect as the embodiment shown in FIG. 1 can be achieved. Note that 24 is a capacitor placed in the collector of the transistor 22.

Furthermore, in FIGS. 1 and 4, 1. Although the case where the second transistor 7.8 uses an NPN transistor is shown, it can also be configured using a PNP transistor, for example,
In the circuit shown in Fig. 4, the first. PN the second transistor 7.8
P transistor 25°26 is replaced with the fifth transistor.
If the circuit is converted using transistors 27 to 34 as shown in the figure, the same effects as the embodiments of FIGS. 1 and 4 can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, the first
．． The second transistor is connected to the first transistor. A second feedback loop is provided for these first and second feedback loops. Since the configuration is configured to stabilize the constant current source of the second transistor and the common pace potential, a highly accurate reference voltage can be obtained, and a constant voltage for the load can be obtained despite fluctuations in transistor characteristics and power supply voltage. This has the effect of being able to stably supply a constant current.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a constant current/constant voltage circuit according to an embodiment of the present invention, and FIGS. A characteristic curve diagram of the collector current of the second transistor, FIG. 4 is a circuit diagram showing a constant current/constant voltage circuit according to another embodiment, and FIG. 5 is a circuit diagram showing a constant current constant voltage circuit according to another embodiment. ,
FIG. 6 is a circuit diagram showing a conventional constant current circuit, and FIG. 7 is a circuit diagram showing a transistor circuit whose driving capacity is doubled. 3 is a load, 7 is a first transistor, 8 is a second transistor, 11 is a third transistor, 12 is a fourth transistor, 14 is a resistor, 22 is a fourth transistor, 2
5 is a first transistor, 26 is a second transistor,
2S is a third transistor, and 33 is a fourth transistor. In addition, the same symbols in the figures indicate the same or equivalent parts. Patent Applicant Mitsubishi Electric Corporation 7 +1 Transistor 8 +2 Transistor 9 11 Near 3 Transistor 9 12, +4 Transistor 7 14゛K To 1 Friend 22: +4 Self-Turn Z Figure 2 ■ABI → VA8 Figure 3 ABI->VAa 6゜The description of the amendments will be corrected as follows. Procedural amendment Showa (voluntary) 63, '+'! , month, day, 10

Claims (1)

[Claims] a first transistor whose respective bases are connected at a first connection point; a second transistor of the same type having n times the driving capacity of the first transistor; the voltage between the resistor connected between each emitter of the transistor, the second connection point connecting the resistor and the emitter of the first transistor, and the first connection point and the second connection point; a first feedback loop that controls each collector current of the first transistor and the second transistor by a third transistor of a different type from the first transistor, the base of which is connected to the collector of the first transistor; A second feedback loop for controlling the voltage at the first connection point by a fourth transistor of a different type from the second transistor, the base of which is connected to the collector of the second transistor; A constant current/constant voltage circuit that is equipped with a load that is supplied with constant current and constant voltage according to the operation of the constant current/constant voltage circuit.