RU2014646C1 - Direct voltage regulator with pulse control - Google Patents

Abstract

FIELD: secondary sources of power supply. SUBSTANCE: direct voltage regulator with pulse control has key controlling element, LCD filter, control unit including comparator, RS flip- flop, logic 2AND gate, source of reference voltage, generator, capacitor, two voltage dividers. Controlling element produces stationary control pulses, i.e. of equal duration with invariable output voltage and frequency. Frequency of these pulses is determined by frequency of generator and their duration depends on changes of output voltage. Voltage regulator may have three versions: step-down, step-up and inverting. EFFECT: reduced dimensions, improved operational stability. 2 cl, 2 dwg

Description

 The invention relates to electrical engineering / namely to sources of secondary power supply of electronic equipment / intended for use as part of small-sized equipment.

 Known DC voltage stabilizer / operating in the mode of pulse-width modulation / containing a control transistor. An LCD filter and a control circuit (the basis of which is a K142EP1 microcircuit / containing a differential amplifier / sawtooth driver / working with an external capacitance from an external rectangular voltage generator / pulse-width modulator / matching transistors / and a voltage reference source. The output of the pulse-width modulator is connected to the base of the first matching transistor / emitter of the second matching transistor is connected to the common circuit wire / and the collectors of both matching transistors are connected through the intermediate transistor to the base of the regulating transistor. A differential amplifier compares the output voltage with a reference one, and a pulse-width modulator generates pulses / duty cycle which is proportional to the difference between the input and output voltage of the stabilizer at a certain load current [1].

 The disadvantage of the microcircuit is a low degree of integration / because of which a large number of external attachments is required and the need to connect an external source of rectangular modulation voltage / also isolated to it. The composition of such a source (generator) should include a winding element (transformer) / unacceptable for microcircuit design and technologically complex in the form of a hinged element.

 The closest in technical essence to the proposed technical solution and taken as a prototype is a DC voltage regulator with pulse regulation / consisting of a key regulating element / having at least two npn-type transistors / the base of which is the control input of the regulating element / base the second is connected to the emitter of the first transistor / from the LCD filter connected in series with the output terminals / as well as from the control unit of the regulatory element / on which includes a comparator / RC trigger / the output of which is connected to the control input of the control element / logic element 2I / with one of the inputs connected to the output of the comparator / and the output - to the S-input of the RC trigger / reference voltage source / generator with two outputs / of which the first is connected to the other input of the logic element 2I and the R-input of the RC trigger / and the second to the capacitor / and from the first resistive divider / included in the feedback circuit / connected between the input output and the inverting input of the comparator [2].

 In the prototype, the output of the reference voltage source is directly connected to the non-inverting input of the comparator / and the key regulator is provided in three versions: respectively, for the lowering stabilizer / for the raising and for the inverting. In the first two options, feedback is performed through the first resistive divider from the stabilizer output to the inverting input of the comparator / and in the third (inverting) version, an operational amplifier / operating in the scaled amplifier-inverter mode is included in the feedback circuit between the first resistive divider and the inverting input of the comparator transmission coefficient / equal to one. In each of these options, the feedback voltage (with a certain transmission coefficient) from the output of the stabilizer is fed to the inverting input of the comparator / which compares it with the reference voltage / supplied to the non-inverting input. The RS-trigger is controlled by the R-input from the first output of the generator / on which there are negative (in the form of a logical zero) pulses / whose duration is equal to the relaxation time of the generator / and on the S-input - by pulses of the logic element 2I. Each time / when a logical unit appears at the output of the comparator in a pause between the negative pulses of the first output of the generator / the RS-trigger is switched over to the S-input and both transistors of the control element are switched on / in this state until the end of the current period of the generator.

 So / in the prototype, the control unit compares two constant voltages / one of which (from the feedback side) may contain a component of the ripple of the output voltage. Since this component substantially depends on the load and capacitance of the LCD filter’s capacitor / which, due to the large size of the capacitance, is usually selected as electrolytic / and the capacitance of such a capacitor substantially depends on temperature /, the variable component of the feedback voltage is uncertain and / besides / its form is not strictly sawtooth. As a result of this, the moment of switching the RS-flip-flop on the S-input is determined randomly by the comparator. It changes from period to period of the generator’s operation / which precisely (and constantly) determines only the moment of reset of the RC trigger (at the moment of its relaxation). The random inclusion of the RS-trigger / which may not take place in each generator period / leads to a large ambiguity of the pulses of the key element (at the input of the LCD filter). The stabilizer stabilizes as if "in principle." It can withstand a given output voltage rating and with a given tolerance. But its key element works with any frequency and duration / randomly changing. Under such circumstances, the LCD filter should be designed for the longest and smallest possible pulses. This increases the size and weight of the LCD filter. In addition / if several voltages (including alternating voltages) are required for the powered equipment / then the power inverter / which is required to be used / must be completely autonomous / with its own master (clock) generator / since the pulses of an unsteady-working control unit should be used as clock for the inverter - is not possible.

 The purpose of the invention is the improvement of overall dimensions by ensuring the stationary nature of the operation of the regulatory element / as well as expanding the functionality of the stabilizer by using it in a multi-channel design.

 This is achieved by the fact that in a DC voltage regulator with pulse control / consisting of a key control element / from an LCD filter / output connected to the output terminal / and also from a control unit / including a comparator / RS-trigger / the output of which is connected to the control the input of the regulatory element / logic element 2I / one of the inputs connected to the output of the comparator / and the output to the S-input of the RS-flip-flop / reference voltage source / generator with two outputs / of which the first is connected to another input logic element 2I - to the R-input of the RS-flip-flop / and the second to the capacitor / and from the first resistive divider / included in the feedback circuit / connected between the output terminal and the inverting input of the comparator / a second resistive divider is inserted / connected to the output of the reference source by the extreme terminals voltage and the second output of the generator / a middle output - to the non-inverting input of the comparator.

 The key control element is made of at least two npn-type transistors / the base of the first of which is used as the control input of the key regulatory element / and the base of the second transistor is connected to the emitter of the first transistor / and from the third pn-p-type transistor / emitter and collector which are connected respectively to the input terminal / positive polarity and the input of the LCD filter / and the base through the entered resistor is connected to the collector of the first transistor / the emitter of the second transistor is connected to a common bus / and the open collector of the second transistor is used as a signal output for connecting a voltage converter.

 The essence of the invention lies in the fact that the sawtooth voltage / generated by the generator (at its second output) is mixed with the reference voltage / supplied to the non-inverting input of the comparator of the control unit /. Mixing of both voltages is carried out by a voltage divider / to the extreme terminals of which both of the indicated initial voltages are applied / and the resulting voltage is removed from the output / is the reference voltage / modulated by a "saw" of constant (stable) amplitude. Thus, it becomes possible to obtain a width-modulated signal from the comparator / providing a stationary mode of operation of the regulating power element.

 In FIG. 1 shows a diagram of the proposed stabilizer in a specific embodiment of the lowering type; figure 2 - the same / regulatory element which is made on two n-p-n-type transistors and a third transistor with a p-n-p type of conductivity / wherein the second n-p-n transistor is used to isolate clock pulses to a voltage converter / if the stabilizer has a multi-channel design.

 The stabilizer consists (Fig. 1) of the key control element 1 / including the first 2 and second 3 transistors of npn type / LCD filter 4 / control unit 5 / which includes a comparator 6 with inverting 7 and non-inverting 8 inputs / RC- trigger 9 / logic element 2I 10 / reference voltage source 11 / generator 12 with two outputs 13 and 14 / generating negative clock pulses on the first output 13 / sawtooth voltage / capacitor 15 / and the first 16 and second 17 resistive on the second output 14 dividers. In this particular embodiment, the regulating element 1 is connected in series with the LCD filter 4 between the input and output of the stabilizer and this output is connected through the resistive divider 16 to the inverting input 7 of the comparator 6 / the output of which is connected to one of the inputs of the logic element 2I 10 / output connected to S-input of the RS-flip-flop 9. The first output 13 of the generator 12 is connected to the R-input of the RS-flip-flop and the second input of the logic element 2I 10. A capacitor 15 is connected to the second output 14 of the generator 12. To the output of the reference voltage source 11 and the second output 14 of the generator 12 is connected to the extreme terminals of the divider 17 / the middle output of which is connected to the non-inverting input 8 of the comparator 6. The output of the trigger 9 / which is the output of the control unit 5 / is connected to the base of the transistor 2. The collectors of the transistors 2 and 3 are interconnected and connected to the input terminal of positive polarity. The base of the transistor 3 is connected to the emitter of the transistor 2 / and the emitter of the transistor 3 is used (in a specific implementation example) as the output of the regulating element 1.

 In the stabilizer with the output of the clock pulses to the voltage converter (Fig. 2) in the regulating element 1 there is also a third transistor 18 with pnp-type conductivity and a resistor 19 / connected between the collector of transistor 2 and the base of transistor 18 / whose emitter and collector are connected respectively to the input positive polarity output and LCD filter input 4. The emitter of the transistor 3 of the regulating element 1 is connected to a common bus / and the open collector 20 of this transistor / which is the output of the clock pulses / is loaded on the resistor 21 / connected by another output to the output terminal of the stabilizer of positive polarity (in this example, a specific implementation).

 The stabilizer works as follows.

 The voltage from its output in the feedback circuit passes through the first voltage divider 16 to the inverting input 7 of the comparator 6. The non-inverting input 8 from the second divider 17 receives the divided difference between the two voltages: the reference and sawtooth / present on the extreme terminals of the divider 17. The voltage at the second the output 14 of the generator 12 has the form of a rising saw with relaxation / attributable to the time of the negative voltage drop at the first output 13 of the generator 12. The voltage at the non-inverting input of the comparator 6 essentially remains etsya reference / but provided with sawtooth component. Comparator 6 compares this voltage with the feedback voltage. At the output of the comparator 6, a positive differential is obtained / switching RS-flip-flop 9 at the S-input then / when the voltage at the non-inverting input of the comparator 6 begins to exceed the voltage of the inverting input. If the output voltage of the device decreases (increases) / then the switching moment of the trigger 9 is shifted closer (further) relative to the beginning of the rise of the sawtooth voltage.

 Thus, pulse-width regulation is carried out / and the duty cycle of the pulses of the regulating element 1 is made dependent on the magnitude of the load current / and the frequency of the generated control pulses of the regulating element is equal to the frequency of the generator 12 / set by the capacitor 15.

 The stabilization coefficient of the device depends on the steepness of the sawtooth component of the reference voltage / increasing with decreasing steepness. On the other hand, the instability of the amplitude of the sawtooth voltage is a destabilizing factor introduced into the stabilizer. In order to get rid of it, the sawtooth voltage must be formed stable. In μ A78S40 (KP1156КУ1) this condition is realized. The sawtooth voltage in this chip is stable to the same extent / as the reference voltage (1 / 3V). The maximum and minimum levels of sawtooth voltage of the microcircuit differ in this microcircuit by approximately two times / and the amplitude of the upper level is about 1 / 3V.

 The pulses for converting additional channels / if they are needed (figure 2) / are removed from the collector of the transistor 3.

 Thus / the proposed stabilizer differs from the prototype in that / the control pulses of the key regulatory element in it are generated stationary / i.e. with the same duration and frequency from period to period (with constant load and output voltage). The frequency of these pulses is the same / as the frequency of the generator / and the duration is adequate to the load and the input voltage. The data for calculating the LCD filter becomes certain / its mass and dimensions (throttle / capacitor and stabilizer as a whole) are reduced. It becomes possible to use the pulses of the control unit (as clock pulses) to drive the voltage converter when the need for additional channels of constant or (and) alternating voltage. In the multi-channel version, it turns out / therefore / the gain is also in that / the master oscillator is saved / since the stabilizer control unit along with its regulating element is now able to perform its role along the way (transistors 2 and 3 are part of μ 078S40 and КР1156ЕУ1 microcircuits).

Claims (2)

 1. A DC VOLTAGE STABILIZER WITH PULSE CONTROL, containing a key control element, an LCD filter, the output of which is connected to the output terminal, a control unit including a comparator, an RS trigger, the output of which is connected to the control input of the key control element, logic element 2I, the first whose input is connected to the output of the comparator, and the output to the S-input of the RS-flip-flop, a reference voltage source and a generator that generates negative clock pulses at the first output, and a sawtooth voltage at the second output voltage, the first output is connected to the second input of the 2I logic element and to the R-input of the RS flip-flop, a capacitor connected between the second output of the generator and the common bus, the first resistive divider included in the feedback circuit connected between the output terminal and the inverting input of the comparator, characterized in that, in order to improve the overall dimensions by ensuring the stationary nature of the operation of the key regulatory element, a second resistive divider is inserted into it, with the extreme leads connected respectively with the output of the reference voltage source and a second generator output and the average output - to the inverting input of the comparator.  2. The stabilizer according to claim 1, characterized in that, in order to expand the functionality by using multi-channel performance, the key control element is made of at least two n - p - n-type transistors, the base of the first of which is used as the control the input of the key regulatory element, and the base of the second transistor is connected to the emitter of the first transistor, and from the third transistor is p-n-p type, the emitter and collector of which are connected respectively to the input terminal of positive polarity and to LCD filter input, and the base through the introduced resistor is connected to the collector of the first transistor, the emitter of the second transistor is connected to a common bus, and the open collector of the second transistor is used as a signal output for connecting the voltage converter.

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