RU2465628C1 - Microenergy converter of unipolar voltage into bipolar - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: microenergy converter of unipolar voltage into bipolar one is proposed, comprising an input voltage divider from serially connected first and second resistors, an operational amplifier, the inverting input of which is connected with the middle point of the divider, and also with an output of the operational amplifier via the third resistor, and the output of the operational amplifier is connected via an inductor, to the output of the converter, besides, the output of the converter is connected to a non-inverting input of the operational amplifier, and the output of the converter is connected to poles of the input voltage source via the first and second filtering capacitors, at the same time it additionally comprises a logical element-CMOS inverter, at the same time the output of the operational amplifier is connected to the inverter input, and the inverter output is connected to the point of connection of the third resistor and the inductor, at the same time the inverting input of the operational amplifier is connected with the middle point of the divider and the output of the inverter via the third resistor, and the non-inverting input of the operational amplifier is connected to the converter output.

EFFECT: development of a converter of unipolar voltage into bipolar one, which has high efficiency that does not depend on load current, also in microenergy mode of consumption.

2 dwg

Description

The invention relates to the field of electrical engineering and can be used in sources of secondary power supply of electronic equipment.

Often when powering electronic devices from a unipolar voltage source, it becomes necessary to obtain two voltages that are symmetrical with respect to a common point (earth). Especially often, such cases arise if galvanic cells and batteries are used as sources. Balanced voltage is needed to power operational amplifiers, which typically should amplify input signals of both polarities. Power amplifiers, DC amplifiers, symmetric keys, integrated circuits of analog-to-digital and digital-to-analog converters, and other elements and devices of electronic equipment may also need bipolar power. In such cases, converters of unipolar voltage to bipolar ("artificial midpoints") are used.

The simplest and most widely used analog of such a converter is a resistive voltage divider, the middle point of which is connected to a common point (ground). The scheme and principle of operation of such a converter are trivial and repeatedly described in the literature, for example, in [1]. It is well known that the values of both resistors included in the divider must be the same. However, such circuits have significant drawbacks that arise from the fact that in order to ensure the symmetry of the two resulting voltages, an exact division of the input voltage in half is required. To fulfill this condition, it is necessary that the current taken by the load from the divider be many times less than the current flowing through the divider itself. In this case, a significant part of the power consumed from the power source is lost uselessly for heating the resistors of the divider. This drawback is especially acute when using autonomous power supplies of limited capacity (galvanic cells and batteries). In addition, the stability of the symmetry of the resulting stresses in such a circuit is very low, because To obtain high stability, it is necessary to pass a very large current through the divider, which is impossible. Therefore, in practice, the accuracy of voltage symmetry usually does not exceed a few percent, which is clearly not enough, for example, when used in measuring instruments.

In order to reduce useless power losses on the divider, active dividers are used, containing a resistive divider and a voltage follower based on an operational amplifier (OA), the output current of which is amplified by a symmetric emitter follower on a complementary pair of transistors. In this case (given the high input impedance of the op-amp), the resistors of the divider can choose very large ratings and the power loss on them will be negligible. The own power consumption of modern op-amps is also very small. The accuracy and stability of maintaining the symmetry of the output voltages in such schemes can be very high.

Closest to the proposed invention is [2] including an input voltage divider from series-connected resistors R1 and R2, an operational amplifier, the non-inverting input of which is connected to the midpoint of the divider and to the emitters of transistors through resistor R3, and the output is connected to the bases of transistors VT1 and VT2 of types npn and pnp, respectively, and the emitters of these transistors are connected through an inductance to the output of the converter, the output of the converter being connected to the inverting input of the operational amplifier, and the collector ry n-p-n and p-n-p transistors are respectively connected to positive and negative poles of a source of input voltage and the inverter output is connected to the poles of a source of input voltage through C1 and C2 are filter capacitors. The circuit of this converter is shown in figure 1.

However, such a converter is also not without drawbacks, which are a consequence of the use of bipolar transistors in it, which require a certain power for control, which leads to a decrease in the efficiency (efficiency). This drawback is especially noticeable in micropower mode, i.e. at low power taken from the converter, in this case, the power spent on controlling the transistors can become the main component in the total consumption of the converter from the power source.

The aim of the present invention is to provide a converter of unipolar voltage to bipolar, which has a high efficiency that does not depend on the load current, including in micropower consumption mode.

This goal is achieved by the fact that in the known circuit of the converter of unipolar voltage to bipolar, including an input voltage divider from series-connected resistors R1 and R2, an operational amplifier, the non-inverting input of which is connected to the midpoint of the divider and to the transistor emitters through resistor R3, and the output is connected to the bases of transistors VT1 and VT2 of types npn and pnp, respectively, and the emitters of these transistors are connected through an inductance to the output of the converter, and the output of the converter is connected to to the operating input of the operational amplifier, and the collectors of npn and pnp transistors are connected respectively to the positive and negative poles of the input voltage source, and the output of the converter is connected to the poles of the input voltage source through filter capacitors C1 and C2, the bipolar transistors VT1 and one logical inverter element are replaced CMOS DD1, while the output of the operational amplifier is connected to the inverter input, where the transistor bases were previously connected, and the inverter output is connected to the connection point ineniya of resistor R3 and inductance L, where transistor emitters had previously been connected, and the inverting and non-inverting inputs of the operational amplifier were interchanged. (The power circuits of the DD1 inverter are not shown in the diagram: the inverter is powered by an input voltage source.)

A distinctive feature of the proposed device is the replacement of a composite emitter follower (EF) with a CMOS inverter, which allows to increase the efficiency of the converter in micropower consumption mode.

The principle of operation of the Converter consider the scheme shown in figure 2.

In the prototype op-amps, together with the EF, they operate in the comparator mode with hysteresis. The hysteresis zone of small width (of the order of several units or tens of mV) is created due to the positive feedback, which covers the op-amp together with the electromotive force through resistor R3. In this case, the transistors of the EP work in key mode. The average value of the pulse voltage at the output of the EM will be equal to the voltage at the output of the resistive divider half the voltage of the input source. The inductance L together with the capacitors C1 and C2 form a filter that smooths out the pulsation of the pulse voltage, as a result of which the voltage at the midpoint of the converter will pulsate relative to half the voltage of the input source with a full amplitude equal to the width of the hysteresis zone, i.e. very slightly. The generation frequency depends on the width of the hysteresis zone and on the filter parameters, i.e. from the values of L, C1, C2, as well as from the load current. When using a modern op-amp with such a high input impedance and low intrinsic consumption in such a circuit, the main power consumed by the converter at idle and at micropower load will consist of the cost of power for controlling the transistors of the electric power.

In the proposed circuit, instead of a composite electromotive force on a complementary pair of bipolar transistors, which performs the function of an op amp current amplifier, a CMOS logic inverter is used (for example, from 561 or 564 series integrated circuits). This inverter contains complementary insulated gate field effect transistors (MOS transistors), which practically do not require power consumption for control. For this reason, the intrinsic consumption of such an inverter is very small and significantly less than that of the electronic devices on bipolar transistors. Since the logic element DD1 inverts the output signal of the op-amp, i.e. essentially interchanges the purpose of the inverting and non-inverting inputs of the op-amp, then to preserve the operability of the converter, the specified inputs of the op-amp are interchanged with respect to the prototype.

As a result, the proposed micropower converter of unipolar voltage to bipolar can significantly increase the efficiency, as well as reduce the size and weight of the converter by replacing two transistors with one integrated logic element.

Information sources

1. Shustov M.A. Practical circuitry. Voltage converters. Book 3. M.: DODEKA XXI century, 2007.

2. Zaitsev M.A., Matsykin S.V., Sukhov A.V. Unipolar to bipolar voltage converter. Patent No. 2850217, 2008.

Claims (1)

A micropower converter of unipolar to bipolar voltage, including an input voltage divider from series-connected first and second resistors, an operational amplifier whose inverting input is connected to the midpoint of the divider, as well as to the output of the operational amplifier through a third resistor, and the output of the operational amplifier is connected through inductance, to the output of the converter, and the output of the converter is connected to a non-inverting input of the operational amplifier, and the output of the converter is connected to the poles of the input voltage source through the first and second filtering capacitors, characterized in that it additionally contains a CMOS inverter logic element, while the output of the operational amplifier is connected to the inverter input, and the inverter output is connected to the connection point of the third resistor and inductance, while the inverting input of the operational amplifier is connected to the midpoint of the divider and the inverter output through a third resistor, and the non-inverting input of the operational amplifier is connected to the output of the converter.

Images