SU1690140A1 - Constant voltage/preset form alternate voltage converter - Google Patents

Abstract

The invention relates to electrical engineering, in particular to sources of secondary power supply. The goal is to increase the reliability of work. The device contains pulse-width modulators 1.1-1.2M (Figs 1, 2), key amplifiers 2.1-2.2N of power, low-pass filters 3.1-3N, sources 4.1-4.N of power supply, differential amplifiers 5.1-5. N, current sensors 6.1-6.N. Pulse width modulators 1.1-1.2N form sawtooth-like elements. The invention relates to electric welding and is intended for use in controlled power supply systems for electric drives, vibration shakers, etc. large and medium power. The purpose of the invention is to increase the reliability of work. FIG. Figures 1 and 2 are respectively a structurally and partially functional diagram of the described DC / DC converter to an alternating voltage of a given shape; Fig. 3, with a time shift DgT / 2, with the modulators of the adjacent (paired) key transformation channels saw-tooth voltages being in antiphase. Key power amplifiers 2.1-2.2N included on bridge circuits. When successively adding pulse signals in a bridge circuit, the total pulse voltage has a switching frequency; twice as high as the switching frequency of the individual channels. In connection with this, the combinational components of the pulse voltages connected in parallel to the load 9 are grouped in the high frequency range, which allows for a wide frequency range of signal conversion. The possible imbalance of the output currents of the bridge circuits is reduced by using the negative current feedback implemented by current sensors and differential amplifiers 5.1-5 N. 6. .N 5 Il. - time diagrams of signals, explaining the principle of multichannel pulse-width modulation; in fig. 4a, b shows the equivalent circuit; Fig. 5 is a timing diagram of the voltages illustrating the addition of the signals used in the device. The device contains pulse-width modulators (PWM) 1.1-1.2N (Fig. 1, 2), key amplifiers 2.1-2.2N of power (KUM) on transistors, throttle filters 3.1-3.2N of low frequencies (LPF), source s o y o Ј o

Description

4.1-4.N power supplies, 5.1-5.N differential amplifiers, 6.1-6.N current sensors, 7, 8 terminals for connecting a load 11. In each lth of 2N key conversion channels, direct and inverse PWM 1 outputs I are connected to the corresponding control inputs of CUM 2.I, and the output terminal of the latter through the low-pass filter 3.I is connected to the channel output bus (not shown). The outputs of the sources 4.1-4.N of the power supply are connected to the supply busses of KUM 2.1 and 2.2, 2.3 and 2.42.2N - 1 and 2.2N, pairwise grouped,

The output 7 for connecting the load is connected to the output buses of the even channels of the key transformation. Each 6.2 - 1 current sensor is connected to the output bus of the 2nd - 1st (odd) channel of the key conversion and one of the current terminals is connected to terminal 8 for connecting the load. The outputs of the differential amplifiers 5.1-5.N are connected to the inputs of the PWM 1.1 and 1.2 pairwise grouped together,

1,3 and 1.4 1. (2N - 1) and 1.2N, first inputs

- to the input of the source of the control signal with the potential output terminal 11, and the second inputs to the outputs of the current 6.1-6.N sensors with the same sequence numbers.

PWM 1.1-1.2N is designed to form 2N pulse-width modulated pulse sequences. Multi-channel pulse-width modulation is provided by generating in the PWM of each channel a key sawtooth voltage conversion with a predetermined time shift At T0 / 2N. For example, for four-channel pulse-width modulation (Fig. 3), four reference voltages Uni-Un4 are used, which corresponds to the formation of four pulse voltages e- | -E4 with uniform phase shift at the switching frequency.

KUM 2.1-2.2N serve for highly efficient power amplification of pulse signals generated by PWM 1.1-1.2N.

KUM 2.1-2.N is performed by half-bridge circuits (Fig. 2), in which transistors are controlled anti-phase by signals from the direct and inverse outputs of PWM 1.1-1.2N. The upper transistors KUM 2.2I - 1 of odd channels are connected to the forward outputs of PWM 1.21 - 1, and the upper transistors of even channels KUM 2.2I of even channels - to the inverse outputs of PWM 1.21. At the same time, for the supply voltage E0 and the control signal Uy, the output pulse voltage KUM is defined in odd channels as 62.0 - 1) Eo 1 + sign (Uy-Un2 (i - 1) / 2, (1)

and in even channels like

where sign x

62 I Ео 1 sign (Uy-Un2 (i - 1) / 2, 1 at x О

1 at x O

For even 21 and odd 2 (- 1) key transformation channels, PWM is used with a relative time shift To / 2 of the reference sawtooth voltage Una and Un (2i-i), which ensures a 180 ° phase shift at the switching frequency of the pulse-width-pulsed pulses generated by them. sequences.

KUM 2.2I and 2.2I - 1 of even and odd key conversion channels are pairwise connected to a power supply 4.1, electrically isolated from other sources, which ensures pairwise sequential addition of signals in a bridge circuit. The resulting voltage applied through the corresponding PFM 3.21 and 3.21-1 to the load 9 from each pair of QM is defined as the difference of their output voltages.

thirty

62 (I - 1), 2 i 62 (i - 1) - 62 i

(2)

FIG. Figure 3 shows the pulse voltages ei, 2 ei - 62 and ez, 4 ez - 64, generated in the four-channel device for each bridge circuit.

Low-pass filters 3.1-3.2N are designed to isolate at the load 9 the useful low-frequency components of the total pulse voltage resulting from the parallel addition of the output pulse voltages of a bridge circuit. The low-pass filter 3.1-3.2N in the particular case is performed on drossel x, the inductance of which is determined from the desired cut-off frequency of the device’s frequency response. For the total impulse voltage, the reduced value of the equivalent choke of the low-pass filter for the N-channel system

U

(3)

The presence of the low pass filter 3.1-3.2N allows parallel addition of the high frequency components of the pulse voltages of the channels connected to pins 11 and 7. For such components, the reactance of the series connected choke and the low pass filter is very large. Parallel addition of high-frequency components of voltage pulses

It is not related to a large amount of high-frequency components of the output current of channels, the amplitude of which does not exceed 5 ... 10% of the current amplitude of the low-frequency components of the signal.

The 6.1-6.N current sensors are used to isolate a signal proportional to the current flowing in the diagonal bridge circuits formed by the corresponding KUM 2.2I and 2.2I - 1 even and odd channels.

The use of galvanically isolated power sources for each bridge circuit ensures that the output currents of the key conversion channels included in each bridge circuit are equal.

Differential amplifiers 5.1-5.N are designed to form voltages at the PWM 1.1-1.2N inputs proportional to the differences of the control signal Uy and feedback signals from current 6.1-6.6N sensors.

The device works as follows. The control signal Uy through differential amplifiers 5.1-5N is fed to the inputs of the PWM 1.1-1.2N of even and odd channels of the key transformation, which are pairwise grouped together. The use of electrically isolated sources 4.1-4.N of power supply for each bridge circuit formed by even and odd KUM 2.2I and 2. (2i - 1) provides, as already noted, the same output currents in pairs of key transformation channels.

The outputs of the bridges are connected to the output buses in parallel, which ensures the parallel addition of their output signals 62.i - 1, еa i, defined by expression (1).

PWM 1.2i and 1.2i - 1, which are part of the adjacent key conversion channels connected in a bridge circuit, generate pulse signals that are antiphase at the switching frequency (180 ° phase shift) with a pulse duration determined by the output signal of the corresponding differential amplifier from aggregates 5.1-5.N. When successively adding the pulse signals 62.1-1, 62.1 in a bridge circuit, the total pulse voltage e2.i-1, 2.1 has a switching frequency twice as high as the switching frequency oto of a separate channel of the key transformation. Indeed, as illustrated in FIG. 3 for the four-red circuit, as a result of subtracting the voltages ei and 62, the alternating voltage ei is formed, 2 ei - 62 s more

high (twice) switching frequency.

With electrically isolated sources 4.1-4.N of the power supply of individual bridge circuits, the contour currents between the key conversion channels connected to any of the pins 11, 7 are absent. The equivalent circuit of the impulse voltages in this device for the four channels of the key gain is shown in FIG. 4 and can be converted to the circuit shown in FIG. 46. Pulsed voltages of each bridge circuit ei, 2. Ez, 4 (Fig. 5) are fed through chokes F. Phase 3.1-3.4 and current sensors 6.1, 6.2 to load 9.

Since the switching frequency of the output pulse voltage of each bridge circuit is twice as high as the switching frequency of the individual channels of the key conversion, in the described device, for a given value of O, the combination components of the pulse voltages connected in parallel to the load are grouped into higher frequencies. This advantage allows for a wide frequency range of signal conversion.

The possible imbalance of the output currents of the bridge circuits, due to the flow of the loop current to (Fig. 4, a), in the technical solution under consideration is reduced by using negative current feedback in each bridge circuit. The depth of this feedback is provided in the order of 20-30 dB, which makes it possible to significantly reduce the imbalance of the output currents of bridge circuits, due to the difference in the low-frequency components of their output voltages.

Thus, the practical application of this device allows to ensure the equality of the output power of the individual channels of the key conversion in the higher frequency range and, thereby, significantly increase the reliability of the voltage converter.

Claims (1)

Invention Formula A constant-voltage converter into an alternating voltage of a given shape containing 2N key conversion channels, in each of which the direct inverse outputs of the pulse-width modulator are connected to the corresponding control inputs of the key power amplifier, and the output output of the latter through the lower filter frequency is connected to the channel output bus, the power source, the output of which is connected to the supply buses of the key amplifiers of the first and second channels of the key conversion, Nickname of the control signal, terminals for connecting the load, the first of which is connected to the output buses of the even-numbered key conversion channels, characterized in that, in order to increase the reliability of operation, N-1 additional power sources, N current sensors and N differential amplifiers are inserted into it moreover, supply buses of key power amplifiers of the third and subsequent channels of the key conversion by five pairwise connected to the outputs of additional power sources, each current sensor is connected to the output bus of the corresponding odd channel key conversion and one of the current terminals is connected to the second terminal for connecting the load, the output of each differential amplifier is connected to the inputs of the odd-even-even pair the key conversion channels, the first input to the output of the control signal source, and the second input to the output of the current sensor related to this pair key converting channels. FIG. 2 a 9 t Uni U / n Un2 Urw e about % about er about ets. oh, er about about e 0 one one Ju u u and and and P Ohno AI and about y pp Fig.Z L L, p p, f A pppp dll /. H pn and and 6 M l p n p Puf.5 S) and and