SU1755354A1 - Voltage converter - Google Patents

Abstract

Use: secondary power supply. SUMMARY OF THE INVENTION: The device comprises a transistor cell, a control system that includes a trigger pulse shaping unit, a synchronized pulse width modulator with two control inputs, a synchronization generator, a controlled key element, and a saWnpaHliWr e fll li forced gag unit Thus, the duration of the output transformer at a constant repetition frequency is inversely proportional to the value of the input unstabilized DC voltage. The ability to control the output voltage is ensured by using a pulse width modulator to analyze the amplitude of the pulses on the additional winding of the output transformer, convert it to a linearly varying voltage, and compare it with the reference voltage set by the adjustable constant voltage source and at equality signal is given to the forced locking unit, which forcibly locks the power transistors of the inverter cell and controls the key element before the signal arrives pulse generating unit starts. 2 hp f-ly93 ill. Yo

Description

The invention relates to electrical engineering and can be used in secondary power sources of automation, telemechanics and computer equipment and information display devices 4, which require conversion of constant voltage and galvanic separation of input and output circuits.

A voltage converter for information display devices is known, comprising a transformerless network rectifier, a capacitive filter, an adjustable voltage converter and a control device made in the form of a PWM (pulse width modulator) card.

The disadvantages of this converter are the inability to compensate for low-frequency oscillations and, therefore, their magnitude is greater compared to pulsations at twice the switching frequency; the stabilization of the voltsecond of the pulse area of the output transformer is not ensured and, accordingly, the invariance of the output

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converter voltage to input voltage changes during its operation in converter mode: to control the power switches in the control circuit, the voltage of the Meander form is necessary: relatively large power consumption from the auxiliary power source to control the inverter cell transistors. l

The closest in technical essence is a voltage converter containing an inverter cell with an output transformer, the primary winding of which is made with a midpoint for connecting the output terminal, the secondary winding is connected to the output terminals, a switching transformer whose primary winding through a controllable key element connected to one of the windings of the output transformer, and the secondary windings through the base resistors are connected to the inputs of the power transistors of the inverter cell, an oning generator with unipolar short rectangular pulses at the output, the secondary winding of which is connected to the input of the forced locking unit with unipolar locking pulses at each output connected to the input of the corresponding power transistor of the inverter cell, and the output transformer is made with an adjustable nonmagnetic gap, and the switching transformer is designed so that the induction increment in its magnetic core is less than its saturation induction.

The disadvantages of this converter are the inability to control the output voltage; the dependence of the pulse duration of the output transformer on the magnitude of the load current due to the beginning of the blocking process with increasing load; the inability to compensate for low-frequency pulsations; the volt-second pulse area of the output transformer is not stabilized and, accordingly, there is no invariance of the output voltage to changes in the input voltage in case of using the converter in converter mode; limited power transferred to the load due to the presence of a non-magnetic gap in the output transformer magnetic core

The purpose of the invention is to expand the functionality by providing output voltage regulation.

The goal is achieved by additionally introducing a pulse shaping unit for an inverter cell with unipolar short rectangular pulses at its paraphase outputs, a feedback rectifier, a synchronized pulse-width modulator, made with the first and second control inputs and synchronization input, as well as an adjustable source of direct voltage, additional winding in the output transformer, additional winding with a diversion from the midpoint in the switching trans-F The auxiliary output in the forced locking unit, wherein the synchronized pulse-width modulator is connected to the first control input via a feedback rectifier with the auxiliary winding of the output transformer, and the second control input to the output of a controlled constant-voltage source, the synchronization input - output of the synchronizing generator, output - with the input of the forced locking unit, the additional output of which is connected to the input of the controlled key element, output of sync oniziruyuschego generator is also connected to the input of a pulse forming trigger inverter unit cell to paraphase output of which is connected an additional winding of the switching transformer.

A negative feedback circuit is also introduced, the input is connected to the LCD output of the filter, and the output to the control input of an adjustable constant voltage source.

Comparison of the proposed technical solution with the analogs and the prototype shows that the analogs use the traditional principles of voltage conversion, in which the inverter cell serves as an external excitation power amplifier and the general negative feedback is introduced in the prototype to control the output voltage. blocking is a process without adjusting the pulse duration of the output transformer with a fixed pause at zero, but there is no possibility of adjusting the output voltage in the converter.

The invention uses a slightly different principle of voltage conversion and stabilization, namely, the volt-second pulse area is stabilized by changing their duration in inversely proportional to the input voltage, and the pause between the pulses varies in direct proportion to

From the input voltage, the output voltage is controlled by varying the pulse duration. This is achieved by using a fully controlled blocking process during the formation of a pulse and a pause between pulses, the use of which, firstly, allows using energy to control the inverter cell transistors mainly from the inverter cell itself and, secondly, helps to reduce the duration of the fronts when switching transistors of the inverter cell, which helps to reduce the dynamic losses on these transistors

Fig. 1 shows a block diagram of the device: Figures 2 and 3 show timing diagrams of voltages on its elements.

The voltage converter (Fig. 1) contains four power transistors 1,2, 3, 4, the emitters of transistors 2 and 4 are connected and connected to the common bus of the converter, and the emitters of transistors 1 and 3 are connected to the collectors of transistors 2 and 4, respectively. transistors 1, 2 and 3, 4 are connected to the primary winding 5 of the output transformer 6. The collectors of transistors 1 and 3 are combined and connected to the positive terminal of the power source 7 of the constant TOka, for example, a transformerless rectifier, and the negative terminal of this source Inonii common bus voltage converter. The secondary winding 8 of the output transformer 6 is connected to the load 9 via the rectifier unit 10 and the LCD filter 11./

In addition, the device contains a positive feedback circuit connected in parallel to the winding 12 of the output transformer 6 and consisting of a series-connected controlled key element 13 and the primary winding 14 of the switching transformer 15, the secondary windings 16, 17, 18 and 19 of which are connected via basic resistors 20, 21, 22 and 23 to the base-to-emitter junctions of power transistors 1, 2, 3 and 4. A secondary winding 24 with a tap from the midpoint of the switching transformer 15 is connected to the outputs of the starting pulse shaping unit 2 5 with unipolar short rectangular pulses at its paraphase outputs, the input of which is connected to a synchronizing generator 26 with unipolar short rectangular pulses at the output. A synchronization input 27 of a synchronized pulse-width modulator 28 is also connected to it. The first control input 29 via the feedback rectifier 30 is connected to the winding 31 of the output transformer 6. The second control input 32 is connected to the output of a controlled constant source. This voltage is 33, and the output is connected to the input of the forced locking unit 34 with unipolar locking pulses at the outputs. The outputs 35, 36, 37, 38 are connected to the base-emitter junctions of the power transistors 1,2,3,4, respectively. The output 39 of the forced locking unit 34 is connected to the input of the controlled key element 13

The device also contains a common negative feedback circuit 41, shown in dotted line in FIG. 1 and connected via an input to the output of the LCD filter 11, and an output connected to the control input of an adjustable constant voltage source 33.

The synchronization generator 26, the forced locking unit 34, the trigger pulse shaping unit 25, the adjustable DC voltage source 33 and the negative feedback circuit 41 are connected to the auxiliary power supply 40 via power supply.

The device can include a measuring transformer 42, shown in dotted line in Fig. 1, connected by the input to the terminals of the secondary winding 8 of the output transformer 6, and the output to the input of the feedback rectifier 30. When connecting the measuring transformer 42, the feedback rectifier 30 must be disconnected from the secondary winding 31 of the output transformer 6.

In the converter mode in the open circuit of negative feedback, the device operates as follows

When the primary source of electricity is switched on, for example, an AC network, the supply voltage C of the direct current source 7 (U in Fig. 2a) is fed to an inverter cell made on power transistors 1, 2, 3, 4. Auxiliary power supply 40 is supplied from the auxiliary power source 40. voltage (LMo in Fig. 2a) to the synchronization generator 26, the trigger pulse shaping unit 25, the forced locking unit 34 and the adjustable source of constant voltage 33.

The synchronization generator 26 forms a rectangular pulse voltage of a small duty cycle Ucxi (Fig. 2b). On the front of the pulse Ucxi of the synchronization generator 26, the block of formation of starting pulses 25 generates the starting pulses.

Dai and U32 (Figs 2c and d) supplied via the windings 24, 16 and 18 of the switching transformer 15 to the bases of the transistors 3 and 2, respectively, through resistors 21, 22, and using the windings 24, 17 and 19 to the bases of the transistors 1, respectively and 4 through resistors 20 and 23. Obviously, when applying to the bases of transistors 2 and 3, opening pulses, the bases of transistors 1 and 4 receive locking pulses and vice versa (Fig. 2c and d).

At the time point to, the start-up pulse shaping unit 25 generates a triggering pulse Usi (Fig. 2c), which is fed to the bases of the power transistors 1 and 4, the forced lock-up unit 34 removes the blocking signal at the outputs 35 and 37 from the bases of these transistors and at output 39 - from the control input of the controlled key element 13, which thereby are in a conducting state (Fig. 2e). Since at the moment of time to, the potentials 11ke1 and 1) ke4 on transistors 1 and 4 are reduced, the following circuit: the positive output of the DC source 7, the collector-emitter junction of transistor 1, the output winding 5 of the output transformer 6, the junction collector-emitter junction of the transistor 4, the common bus, the negative terminal of the direct current source 7, begins to flow. As a consequence, an emf is induced in the winding 12 of the output transformer 6, which causes a current in the circuit: the winding 12 of the output transformer b, controlled by the key element 13 (as it is open), the primary winding 14 of the switching transformer 15. This current induces in the windings 17 and 19 EMF of such a polarity, which contributes to maintaining the open state of transistors 1 and 4 (lion and T4 in figv); on windings 16 and 18, an electromotive force (EMF) contributing to the locking of transistors 2 and 3. At the same time, an electromotive voltage is induced on the winding 31 of the output transformer 6, proportional to the difference voltage between the direct current source 7 and the voltage drops on open transistors 1 and 4, which is fed through the feedback rectifier 30 (Uyi in Fig. 2e) to the first control input 29 of the synchronized pulse width modulator 28, through which the ramp voltage is generated or controlled, to its synchronization input 27 fromsynchronizing generator 26, a locking impulse Ucx2 is applied (Fig. 2g), which is used to set the instant of the onset of the formation of a linearly varying voltage, each time varying from a voltage close to zero,

The second control input 32 of the synchronized pulse width modulator 28 from the adjustable constant voltage source 33 supplies a constant voltage level Uy2 (FIG. 2h), which is the comparison threshold for the linearly varying voltage, upon reaching which the output signal synchronized pulse width modulator 28 spasmodically varies.

Thus, depending on the voltages Uyi and Ku2, the synchronized pulse width modulator 28 forms

5, the time interval t0-ti, during which a high potential is established at its output (Fig. 2i). At time ti, when a low potential is set at the output of the synchronized pulse-width modulator 28, the forced locking unit 34 generates locking signals at the outputs 35, 36, 37, 38 (Ue and and T4 in Fig. 2b and 1) bT2 and 3) and output 39. The latter closes the controllable key element 13, on which the self-induced EMF of the winding 12 of the output transformer 6 is released (interval ti-t2 in Fig. 2d). Due to this, the transistors 1, 2, 3 and 4 are closed and on the primary winding 5

0 output transformer 6, the current is not leaking. Since in the time interval t0-ti transistors 1 and 4 are open, a current flows through the primary winding 5 of the output transformer 6, which induces a winding 8

5 EMF UH causing current in load 9 through rectifier 10 and LCD filter 11.

Let at time point t2, the trigger pulse shaping unit 25 generates the trigger pulse 11З2, and the forced lock block 34 removes the blocking signal at the outputs 36 and 38 from the bases of these transistors and at output 39 from the controlled key element 13, thereby in conducting

5 state (fig.2d) - for controlled key element 13). Since at the time t2 the potential at the collectors of transistors 2 and 3 decreases, then along the circuit: the positive output of the source 7 of the constant

0 current, the collector-emitter junction of the transistor 3, the primary winding 5 of the output transformer 6, the collector emitter junction of the transistor 2, the common bus, minus output of the DC source 7, begins

5 to flow a current in the direction opposite to the direction of this current at the moment of time That. As a result, an electromotive force is induced in the winding 12 of the transformer 6, which causes a current in the circuit: the winding 12 of the output transformer 6 is controlled by a key

element 13 (since it is open at this point in time), the primary winding 14 of the switching transformer 15, winding 12. This current induces in the windings 16 and 18 an emf of such polarity that contributes to maintaining the open state of transistors 2 and 3,

At time t2, an electromotive voltage (EMF) is induced on the winding 31 of the forward transformer 6, which is fed through the rectifier 30 (Uyi in FIG. 2e) to the first control input 29 of the synchronized pulse-width modulator 28, which has a synchronizing input 27 A shut-off pulse, Ushg (Fig. 2g), is supplied from the clock generator 26. At the second control input 32, as in the previous case, a constant voltage level 1) v2 is set using an adjustable constant voltage source 33 (Fig. 2h) The same as in the time interval t0-t2. depending on voltages Uyi and Uy,: synchronized pulse width modulator 28 forms the time interval t2-t3. during which a high potential is established and maintained at its output (FIG. 2i) At time point 1c, the forced locking unit 34 generates locking signals at the bases of transistors 2 and 3 (U6T2 and mh in FIG. 2d) and at output 39, which close the control This is the key element 13, thereby breaking the positive feedback circuit and a self-induced EMF of the winding 12 of the output transformer 6 is released on it (fig.2d). Since in the time interval t2-t3 a current flows through the primary winding 5 of the output transformer 6, it induces an emf of UH in the secondary winding 8 of this transformer (Fig. 2k), transferring energy from the source 7 of direct current to the load 9 through the rectifier 10 and an LCD filter 11. At time points of step 4 and te, the start-up and 11z2 pulses are again formed, respectively, and the described processes are repeated.

The stabilizing input voltage regulation in a device operating in a converter with an open-circuit negative feedback circuit is performed as follows.

When the primary source of electricity is switched on, for example, an AC network, the unstabilized supply voltage from the DC source 7 (U in FIG. 3A) is fed to an inverter cell made on transistors 1, 2, 3, 4. From auxiliary power source 40 the stabilized supply voltage (LUo in FIG. 3a) is supplied to the synchronization generator 26; the forming unit

start-up pulses 25, forced locking unit 34, adjustable source of constant voltage 33. Then the device operates in the same way as described. The difference is as follows. On the winding 31 of the output transformer 6, the EMF is proportional to the voltage of the DC source 7 (minus the voltage drop across the power transistors) and through

0 a feedback rectifier 30 is provided to a first control input 29 of a synchronized pulse width modulator 28.

Let the second control input 32

5 of the synchronized pulse-width modulator 28 a constant voltage level is applied (FIG. 13), and the synchronization input 27 is the synchronization pulses OX2 from the synchronization generator

0 26 (FIG. 36). In accordance with the described algorithm incorporated in the synchronized pulse width modulator 28, pulses are generated at its output, the duration of which is inversely proportional to

5 the value of the voltage Uyi (figsg). A pulse voltage similar in magnitude and proportional to the voltage of the source 7 of direct current comes from the secondary winding 8 of the output

0 of transformer 6 after rectifier 10 to integrating IR filter 11, after which a smooth DC voltage is applied to load 9, the synchronized pulse-width modulator 28 can be adjusted by the first control unit so that the voltage at load 9 (its value a) did not change with changes in input voltage within the specified limits (Fig. Fig)

0 To reduce the effect of load impedance on the output voltage, a negative feedback circuit can be entered. 41 The principle of operation of this circuit is t Gm, this is the load (or part of it) compared to the reference voltage, the difference signal is amplified and arrives at the control input of an adjustable source of constant voltage 33, the voltage Uy2 at the output

0 which is changed in such a way that the voltage on the load UH is constant within the specified limits for any allowable changes in load resistance

5 With the introduction of a negative feedback circuit, the adjustable DC voltage source 33 can in principle be eliminated and the output of the error amplifier of the negative feedback circuit 41 in this case is connected to the second control input 32 of the synchronized pulse width modulator 28 directly or through galvanic isolation element. Obviously, in this case, the amplified difference signal is changed in such a way that the voltage on the load remains constant,

To reduce the effect of dynamic changes in the load on the output voltage, a measuring transformer 42 can be introduced, the primary winding of which in this case is connected to the terminals of the secondary winding 8 of the output transformer 6, and the secondary winding to the input of the feedback rectifier 30. Moreover, the windings 31 of the output transformer 6 are disconnected from the input of the feedback feedback rectifier 30.

The use of the proposed technical solution will make it possible to virtually eliminate the influence of the load on the volt-second pulse area of the output transformer and ensure their stability, eliminate restrictions in the power transmitted to the load. This contributes to improving the quality of the output voltage, as it provides compensation for input unstabilized voltage pulsations, eliminates through-currents through the power transistors, sets a stable conversion frequency, and improves the dynamic characteristics

Thus, the socially beneficial effect obtained from the invention consists in improving the technical characteristics of voltage converters, for example, in information display or power supply systems for automation, telemechanics and computer systems.

Claims (3)

Claim 1. A voltage converter comprising an inverter cell with an output transformer, the secondary winding of which is connected to the output terminals through a rectifier unit and an LCD filter, a switching transformer whose primary winding is connected to one of the windings of the output transformer via a controllable key element, and the secondary windings of the switching transformer through the base resistors are connected to the inputs of the power transistors of the inverter cell, a synchronizing generator with unipolar cores IMT rectangular pulses at the output, a forced locking unit with unipolar locking pulses at each output connected to the corresponding input of the power transistor of the inverter cell, characterized in that, in order to extend the functionality by ensuring the output voltage is controlled, the unit for forming the starting pulses of the inverter cell with unipolar short rectangular pulses at its paraphase outputs, a feedback rectifier, a synchronized pulse-width modulator, made with the first and second control inputs and the synchronization input, as well as an adjustable constant source voltage, additional winding in the output transformer, additional winding with a tap from the middle point in the switching transformer, additional output in the forced-write unit Ani, with a synchronized the pulse-width modulator is connected to the first control input through the said feedback rectifier with the additional winding of the output transformer, the second control input - with the output of the regulated constant voltage source, the synchronization input, with the output of the synchronizing generator, the output - with the input of the forced locking unit, an additional the output of which is connected to the input of the controlled key element, the output of the synchronizing generator is also connected to the input of the unit for forming the starting pulses of the inverter cell, to the paraphase the outputs of which are connected to the mentioned auxiliary winding of the switching transformer. 2. Converter according to claim 1, about t l and h a yu and with the fact that it additionally a negative feedback circuit is introduced, the input is connected to the output of the LCD filter, and the output is input to the control input of an adjustable constant voltage source. 3. Converter according to claims 1 and 2, which is based on the fact that the feedback rectifier is connected through a measuring pulse transformer to the terminals of the secondary winding connected to the output rectifier pin and LCD filter OIL lA i-i-хll-r-vi -tf / Г1 L .. (4fjT 4g-, l s. / too °; Ucxi & Vjf ) Vxs y L%} f i / a, S & "Y Uf one to.3