SU1711135A1 - Dc voltage stabilizer - Google Patents

Abstract

The invention relates to electrical engineering and can be used as a source of reference constant and thermodependent voltages. The purpose of the invention is to improve the accuracy and expansion of functionality. The device contains three transistors matched to each other, five resistors and a differential amplifier. Due to a certain circuit construction on the emitter of the second transistor, the potential is maintained, independent of the magnitude of the supply voltage. And this happens not due to the flow of the output current, but due to the emitter current of the second transistor, which removes the restriction on its value. 1 il.

Description

SP

WITH

The invention relates to electrical engineering and is used in electronic devices as a source of reference constant and thermodependent voltages.

Voltage stabilizer (СН) can be made of water semiconductor chip using standard IC technology using bipolar transistors.

A known DC voltage regulator contains a matched pair of transistors, an operational amplifier, and six resistors 1.

However, such a stabilizer has insufficient accuracy, and there is no source of thermo-dependent current.

Closest to the proposed one is a DC voltage regulator containing three bipolar

transistors, the first two of which are matched to each other, four resistors and a differential amplifier, the emitter of the first transistor is connected to a common bus, its collector is connected to the bases of the first and second transistors, the non-fanning input of the differential amplifier and the first output of the first resistor, the collector of the second the transistor is connected to the first output of the second resistor and the inverting input of the differential amplifier, the output of which is used as the output of the stabilized voltage, while Itter second transistor via a third resistor connected to the common bus, the second terminals of the first and second resistors are connected, the emitter of the third transistor is connected to a first terminal of the fourth resistor, and

WITH

ate

its collector is used as an output of a thermowinding current source 2.

However, the known stabilizer is characterized by insufficient accuracy in the stabilization of the output voltage, as well as the inability to use a source of thermo-dependent current when the supply voltage is less than 1.5-2 V, which leads to a narrowing of the application area of the device.

The purpose of the invention is to increase accuracy and enhance functionality.

This goal is achieved by the fact that in a SN, there are three bipolar transistors, the first two of which form a matched pair, four resistors and a differential amplifier, the emitter of the first transistor connected to the common bus, its collector connected to the bases of the first and second transistors, noninverting input of the differential amplifier and the first terminal of the first resistor, the collector of the second transistor is connected to the first terminal of the second resistor and the inverting input of the differential amplifier, the output of which connected to the output terminal, the emitter of the second transistor through the third resistor is connected to the common bus, the second terminals of the first and second resistors are interconnected, the emitter of the third transistor is connected to the first output of the fourth resistor, and its collector is used as the output of the thermo-dependent current source, the fifth is entered a resistor connected between the output of the differential amplifier and the connection point of the first and second resistors, the second output of the fourth resistor is connected to the common bus, and the base of the third transistor connected to the bases of the first and second transistors, and the third transistor is matched with the first two.

The transistor, the temperature dependence of the emitter-base voltage of which is used to generate a stable voltage, and the transistor-current generator, proportional to temperature, coincide. This leads to an increase in the accuracy of stabilization of the output voltage. In addition, in the proposed device it is possible to lower the voltage at the output of the thermal-dependent current source to 0.6 V without malfunction, unlike the prototype, where this voltage should not be less than 1.2 V). This extends the functionality of the proposed stabilizer.

The drawing shows a schematic diagram of a stabilizer.

The DC voltage regulator contains transistors 1–3 matched with each other, resistors 4–8 and differential amplifier 9, with the emitter of transistor 1 connected to the common bus, its collector to the bases of transistors 1 and 2, the noninverting input of the differential amplifier 9 and the first terminal of the resistor 4, the collector of the transistor 2 is connected to the first terminal of the resistor 5 and the inverting input of the differential amplifier 9, the output of which is used as a stabilized voltage output, while the emitter of the transistor 2 the resistor 6 is connected to the common bus, the second terminals of the resistors 4 and 5 are connected, the emitter of the transistor 3 is connected via the resistor 7 to the common bus, and its collector is used as a current source proportional to temperature, the resistor 8 connects the output of the differential amplifier 9 to the common point of resistors 4 and 5, the base of the transistor 3 is connected to the bases of transistors 1 and 2.

The stabilizer works as follows.

When the power is turned on, the differential amplifier 9 sets its output to a voltage at which the currents flowing through the resistors 4 and 5 create the same voltage drop across them. This is due to the fact that the first terminals of these resistors are connected to the inputs of the differential amplifier (obviously, the potentials of these inputs are equal to the bias voltage of the differential amplifier), and their second terminals are interconnected.

So you can write

And R4 12 RS,

(one)

where And, 2 collector currents of transistors 1 and 2, respectively;

R4, RS - resistance of resistors 4 and 5, respectively.

For currents And and 2, the following formulas are valid:

li lssi-exp (;

2 us2 exp

Ue-ue rt

where Issi, Iss2 are the saturation currents of the emitter transitions of transistors 1 and 2, respectively;

Ue - voltage drop across the resistor

6;

kt temperature potential;

k is the Boltzmann constant; T - absolute temperature; q is the electron charge. Considering that (since the transistors 1 and 2 are matched), get

2 and exp

-Ue fh

Using (1) and conducting a series of simple transformations, get

.

Thus, the circuit operates in such a way that the emitter of transistor 2 maintains a potential independent of the supply voltage proportional to (fh and temperature. The value of Ue is maintained not by the flow of the output current, but by the emitter current of transistor 2, which removes the limitations on its value, and it does not depend on the value of the input voltage. This achieves an increased stability of the output voltage on the voltage in a wide range of supply voltages.

Let us assume that the emitter current of transistor 2 is equal to its collector current. Then, as follows from Ohm’s law and (3),

.. Ue Јg, RS l2-R6 -fe lnRT

Rs, Rs

/ 1 j. R5. ns (1 + Rl) lnRZ

Then the total current flowing through the resistor 8,

 Ј1 l + Rs, PL5 Re I1 + RA) R4

In the known scheme, the temperature coefficient of the voltage emitter — the base of the transistor, the collector current of which is proportional to temperature — is constant over a wide range, and for generating a thermostable output voltage, you can sum up the voltage emitter — the base with a negative temperature coefficient with another, the temperature coefficient

The talent of each is equal to him in size and opposite in sign. In the proposed circuit, such a voltage is the total voltage drop across resistors 4 and 8.

5 As follows from (4), (5) and (6), the current flowing through these resistances is proportional to temperature. In order for the output voltage to be thermally stable, its value must be 1.22 V. It

10 is exposed by adjusting the magnitude of the resistor 8. In this case, the current balance of the circuit does not change.

Transistor 3 can serve as a current generator, proportional to those 15, since (at) its collector current is equal to the collector current of transistor 2. The SN was labeled using the following elements: 1-3 - 198HT1B microcircuit, 9 - operational

20 amplifier KB1409UD1B. The ratings of the resistors 4-8, respectively, 0.91; 9.1; one; 1 kΩ and 200 ohms.

25

Claims (1)

Invention Formula A DC voltage regulator containing three bipolar transistors, the first two of which are matched to each other, four resistors and a differential amplifier, the emitter of the first transistor connected to the common bus, its collector connected to the bases of the first and second transistors, non-inverting . input differential amplifier and with 35 with the first terminal of the first resistor, the collector of the second transistor is connected to the first terminal of the second resistor and the inverting input of the differential amplifier, the output of which is connected to 40 output terminal, the emitter of the second transistor through the third resistor is connected to the common bus, the second terminals of the first and second resistors are connected to each other, the emitter of the third transistor is connected to 45 is the first terminal of the fourth resistor, and its collector is used as the output of a thermo-dependent current source, characterized in that, in order to increase accuracy and expand the functional 50 possibilities, a fifth resistor is inserted in it, connected between the output of the differential amplifier and the connection point of the first and second resistors, the second terminal of the fourth resistor is connected 55 with a common bus, and the base of the third transistor is connected to the bases of the first and second transistors, and the third transistor is matched with the two first transistors. L UOI , ( R 9 ivyh