JPS62182818A - Constant voltage power supply circuit - Google Patents

Abstract

PURPOSE:To produce the stable output voltage which is free from the effect of loads regardless of the number of these loads, by stabilizing the base input voltage of the 4th transistor where the output voltage is taken out through the emitter with the negative feedback function of the 3rd transistor for feedback. CONSTITUTION:A diode D4 and transistors TR Q5 and Q6 from a current mirror circuit 6 serving as an example of a constant current circuit. The current supplied to each collector of both TR Q5 and Q6 is equal to the current flowing to the collector of a TR Q1. Then the base of a pnp TR Q7 is connected to a common joint among a constant voltage element 1, the base of the TR Q1 and the collector of the TR Q5. The collector of the TR Q7 is grounded with the emitter connected in common to an input terminal 2 for power supply voltage together with collectors of the TR Q3, Q41 and Q42 respectively. Here the TR Q7 and a resistance R4 form a start circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a constant voltage power supply circuit, and more particularly to a constant voltage power supply circuit suitable for distributing an arbitrary constant voltage to multiple systems.

Conventional technology FIG. 2 shows a circuit diagram of an example of a conventional constant voltage power supply circuit.

As shown in the figure, the base of the NPN transistor Q8 is connected to a constant voltage element 1 consisting of diodes D+, D2 and Zener dimer D3 connected in series, and is also connected to the power supply voltage input terminal 2 via a resistor R7, and the collector of Q8. It is connected with.

Also, the emitter of transistor Q8 is connected to resistors R5 and R6.
is connected in series to ground.

According to this conventional circuit, a current is flowed into the constant voltage system element 1, and the constant voltage obtained thereby is passed through the base and emitter of the 1-hylang resistor Q8. t2 Bl: Take out as V J, and further this voltage V4 is applied to the resistor Rs.

Divide the resistance using the resistance divider circuit of R6 and use the following formula % formula % (
1) Output the bean paste voltage 5 shown by as the power supply voltage to the output terminal 3.

FIG. 3 shows a circuit diagram of another example of the conventional constant voltage power supply circuit. In the same figure, the same components as in FIG. 2 are given the same reference numerals.
The explanation will be omitted. In FIG. 3, resistors R5 and R
The voltage V5 taken out from the connection point of No. 6 is branched into two, and voltage j1 (after being non-invertingly amplified with a gain of "1" by operational amplifiers 14a and 4b constituting the lower section), the voltage V5 is output to the output terminal 3.
To a and 3b, respectively'? It is output as the ifi source voltage. Similar to the conventional circuit shown in FIG. 2, the output voltage V5 can be set to any value by appropriately setting the ratio of the resistors Rs and R6.

Problems to be Solved by the Invention However, in the conventional circuit shown in FIG. 2, equation (1) does not actually hold due to the input impedance of the load connected to the output terminal 3, and the transistor Q8, Resistance R
5, the voltage drop F of the resistors Rs and Rs changes depending on the load, and as a result, the output voltage V
5 was easily affected by load.

In contrast, the conventional circuit shown in Fig. 3 has an operational amplification of 1W4.
a, 4b are used as high input impedance voltage links, and output type Ti-, Vs are supplied from there to the load. Therefore, the output voltage V5 is not affected by the load. This can be prevented. However, on the other hand, when this conventional circuit is used for distributing the output voltage to multiple systems, the number of operational amplifiers increases according to the number of loads, which makes the circuit complex and expensive.
It was disadvantageous for things such as development.

Therefore, the present invention solves the above problems by stabilizing the output voltage through the negative feedback effect of a feedback transistor, and provides a simple system that can separate and supply the same output voltage to multiple loads. The purpose of the present invention is to provide a constant voltage power supply circuit of the following configuration.

Means for Solving the Problems A constant voltage power supply circuit according to the present invention includes a first transistor whose base is connected to a constant voltage element, and a first transistor connected in series between the emitter of the first transistor and ground. and a second resistor, a second transistor whose emitter is connected to the connection point of the first and second resistors, and a collector of the constant voltage element and the first and second transistors, respectively. a constant current circuit through which current flows; a base thereof is connected to a connection point between the collector of the second transistor and the constant current circuit, and
a third transistor whose emitter is connected to the base of the second transistor; and a third transistor whose base is connected to the connection point between the base of the second transistor and the emitter of the third transistor; It consists of 4 transistors.

The output constant voltage of the working constant voltage element is supplied to the base of the first transistor, is taken out from its emitter, and then resistance-divided by the first and second resistors to be applied to the emitter of the second transistor. is input. The constant voltage input to the emitter of the transistor Q2 is taken out from its base and output to the load on one or two pairs via the base and emitter of the fourth transistor located roughly one or two pairs above.

Meanwhile, the third transistor supplies its emitter output voltage to the base of the second transistor, and controls the second transistor such that the collector current of the second transistor is equal to the constant current of the constant current circuit. do.

As a result, even if the number of fourth transistors is increased to correspond to the number of loads (1=1), the base voltage of the fourth transistor is always stabilized due to the negative feedback effect of the third 1-transistor. Therefore, the emitter output voltage of the fourth transistor is stabilized.

Example An embodiment of the present invention will be described below.

FIG. 1 shows a circuit diagram of an embodiment of a constant voltage power supply circuit according to the present invention. In the figure, the same components as in FIGS. 1 and 2 are denoted by the same reference numerals. In Figure 1, the first N
The base of the PN transistor Q1 is connected to the constant voltage element 1, and the emitter is connected to the first and second resistors R1 and R.
2 is grounded through the j'i column. Resistance R1 and R
The connection point of 2 is connected to the emitter of the second NPN transistor Q2, and the base of Ql is connected to the connection point of the emitter of the third NPN transistor Q3 and the non-grounded terminal of the third resistor R3. I'm here. The connection point between the base of transistor Q2 and the emitter of transistor 03 is commonly connected to the bases of two fourth transistors Q41 and Q42. Each emitter of transistors Q41 and Q42 is connected to loads 51 and 52 via separate output terminals 31,32.

How to use, both emitters of PNP transistor 05 and Qe and the anode of diode D4 are the power supply voltage input terminal 2
The bases of the PNP transistors Q5 and Qe and the cathode of the diode D4 are respectively commonly connected.

As a result, the diode D4, the t'' transistors Q5 and Qe are connected to the current mirror circuit 6 as an example of a constant current circuit.
Configure. The collector of the transistor Q5 is connected to the connection point between the base of the transistor Q1 and the anode of the diode D1 in the voltage regulator 1, and the collector of the transistor Q6
The collector is! The collector of the helangistor Q2 is connected to the connection point with the base of the transistor Q3, and the cathode of the diode D4 is connected to the collector of the transistor Q1. As a result, the constant currents supplied to the collectors of transistors Qs and Qe each become equal to the current flowing to the collector of transistor Q1 according to the well-known principle of a current mirror circuit.

Further, the base of a PNP transistor Q7 is connected to a common connection point between the constant voltage element 1, the base of the transistor Q1, and the collector of the transistor Q5, the collector of the transistor Q7 is grounded, and the emitter is connected to the Transistors Q3, Q41, Q4! It is commonly connected to the power supply voltage input terminal 2 together with the respective collectors of the power supply voltage input terminal 2. This] transistor Q7 and resistor R4 constitute a starting circuit.

Next, the operation of the circuit having the above configuration will be explained.

In the following description, transistors Q1 to Q3゜Qa+
It is assumed that the forward junction voltage between the base and emitter of each of Q42 and Q42 is equal to VBE, and the forward voltage of the diodes D+ and D2 is expressed by Vo, respectively, and the Zener voltage of the Zener diode D3 is expressed by Vz. . The current taken out from the collector of the transistor Q5 in the jJ rent mirror circuit 6 flows through the diodes D+ and D2.
and D3 in series, and generates a constant voltage V1 between both ends of the constant voltage element 1 as expressed by the following equation.

V+ = Vz +2Vo ・・・・・・・・・
. . . ■ This constant voltage v1 is supplied to the base of the transistor QI, and further taken out from its emitter. The emitter voltage ff of this transistor Q1,
If Vε1 is Ve E =VD, then from formula 0 ■ε+ =V+ -VB E =Vz +Vo ・・・・・・・・・・・・・・・
・・・・・・・・・■.

On the other hand, transistor 03 is a feedback transistor that controls transistor Q2 so as to balance the nodal current in the collector of transistor Q2. That is, transistor Q3 has emitter voltage V2 of transistor Q2.
Since the base voltage of the transistor Q2 is controlled based on , the collector current IC2 of the transistor Q2 becomes equal to the output constant current (collector current of the transistor Q6) Ic of the current mirror circuit 6, and IC2=IC... ...1 old... (4
). At this time, the base voltage of transistor Q2 is
3 is V3=V2+Ve E・・・・・・・・・・・・
・・・・・・・・・・・・■ Howl. Note that the resistor R3 is used to allow an appropriate emitter current to flow through the transistor Q3, and may be omitted depending on the case.

In addition, since the collector current of the transistor Ql is harmful to the output constant current ICL of the current mirror circuit 6, (4)
According to the formula, the collector currents of transistors QI and Ql are both equal, and therefore, the emitter current 11 of transistor Q1 and the emitter current I2 of transistor Q2 are both equal. That is, 1+ = 12
・・・・・・・・・・・・・・・・・・・・・(6) Here, if the current flowing through resistor R2 is 13, then 13 =
Il +I2 ・・・・・・・・・・・・
It is... Further, the current 11 flowing through the resistor R1 and the current 13 flowing through the resistor R2 are as shown by the following equations.

[+ = (VEI -V2)/R+...
・・・・・・・・・e13=V2/Rz
・・・・・・・・・・・・・・・・・・・・・0) Therefore, substitute formula 0 into formula 6, and then apply it to formula 6) and (9)
Substituting the equation into the ω equation and solving for v2, we get V2 =
(2R2/(R1+2R2))・(Vz 10Vo)
...(10) is obtained.

The base voltage v3 of transistor Q2 is
41 and Q42, where the impedance is converted and applied to loads 51 and 52 via output terminals 31 and 32 as output line voltage Vo. This voltage Vo is V3-Ve E, and to this, equation 0 and (1
0), the following equation is obtained.

VO=V3-Ve E=Vz=(2R2/(R1-1-2R21)・(Vz+V
o)...(11) That is, 1V for the output power supply. As can be seen from equation (11), is determined by the resistors R+, R2, the Tsebu voltage Vz, the forward drop F voltage Vo of the diode, etc., and remains constant regardless of the number and type of loads. Also, from equation (11), the output power supply voltage ■. It can be seen that the value of can be arbitrarily set by selecting the values of the resistors R+ and R2, regardless of the value of (1).

According to this embodiment, since the number of loads is two, the transistor Q41. Q42 is set up, but if the number of loads is 1 =
1, a fourth transistor is provided whose base is connected to the base of transistor Q2.

Note that the present invention is not limited to the above-mentioned embodiments; for example, the number of loads may be one;
Ql, Q41, and Qu may be composed of PNP transistors, and the transistors Q5 to Qy may be composed of NPN transistors. However, in that case, it goes without saying that the voltage at the power supply voltage input terminal must be negative and the direction of the diode D+-Da must be reversed to that in FIG.

Effects of the Invention As described above, according to the present invention, the base input voltage of the fourth transistor from which the output voltage is taken out from the emitter is
Since it is stabilized by the negative feedback effect of the third transistor for feedback, it is possible to generate a stable output voltage that is not affected by the load regardless of the number of loads, and it is possible to generate a stable output voltage that is not affected by the load. Prepare the fourth transistor of
Therefore, compared to the conventional circuit shown in Fig. 3, which increases the number of voltage followers, the circuit can be configured at low cost without requiring many parts, and furthermore, it is possible to construct a circuit at a low cost with a constant voltage. It has many features such as being able to generate any constant output voltage regardless of the voltage value of the element.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of the circuit of the present invention, and FIGS. 2 and 3 are circuit diagrams showing each of five conventional circuits. 1... Constant voltage element, 6... Current mirror circuit, Q
+...first NPN transistor, Q2...second NPN transistor, Q3...third NPN synristor, Q41. Q42... Fourth NPN transistor, 05-Q7... PNP transistor, D+, D2
. D4...Diode, D3...Zener diode.

Claims (1)

[Claims] A first transistor whose base is connected to a constant voltage element, first and second resistors connected in series between the emitter of the first transistor and ground, and a connection between the first and second resistors. a second transistor whose emitter is connected to a point; a constant current circuit that flows a current through the constant voltage element and the collectors of the first and second transistors; The base is connected to the connection point with the constant current circuit, and the emitter is connected to the base of the second transistor so that the collector current of the second transistor is equal to the constant current of the constant current circuit. a third transistor that controls the base voltage of the second transistor; and one or more fourth transistors whose bases are connected to a connection point between the base of the second transistor and the emitter of the third transistor. 1. A constant voltage power supply circuit comprising a fourth transistor, and configured to extract an output voltage from the emitter of the fourth transistor.