SU1555785A1 - Method of converting ac voltage to dc voltage - Google Patents

Abstract

The invention relates to electrical engineering, in particular, to the field of secondary power supply of electronic equipment. The purpose of the invention is the elimination of pulsations accompanying the transformation process. The method is based on the phase modulation of the input sinusoidal voltage U tion _Rin = U _vh.maks SIN (ΩT + φ). If at the moment of time corresponding to the initial phase shift Θ, we begin to shift the phase ϕ of the voltage U _in , in the direction of the lag at a speed equal to its circular frequency ω, i.e. the law ϕ = ΩT ± Θ, then the result of the transformation is a constant voltage U _out . The magnitude and sign of the voltage U _out are determined by the selected angle Θ. 4 il.

Description

The invention relates to electrical engineering and is intended for use in the construction of sources of secondary power supply for electronic equipment.

The purpose of the invention is to improve the quality of the conversion by eliminating pulsations at a constant voltage.

Figures 1 and 2 show, respectively, the structural and basic electrical circuits of the device, realizing the proposed method of converting an alternating voltage to a constant; 3 and 4 are timing diagrams of signals illustrating its operation.

The device contains a phase modulator 1 (Fig.1 and 2), (phase shifting

node 2 and sawtooth driver 3. The signal inputs of the phase modulator 1 and the phase-shifting node 2 are connected to the terminals for connecting a source of input (convertible) UK alternating voltage, for example, through a network transformer. The control input of the phase-shifting unit 2 is connected to the terminals for connecting the source of the control voltage IL to the direct current, and the output to the input of the former 3 of the sawtooth voltage. The control input of the phase modulator 1 is connected to the output of the former 3 of the sawtooth voltage, and the output is connected to the terminals for connecting the load.

Phase modulator 1 is two serially connected

JV SL

-vl

00

ate

bridge bridge shifters (figure 2). Bipolar transistors included in the diagonal of diode bridges are used as adjustable resistances. Phase-shifting unit 2 is a phase-shifting amplifier. In this case, the role of an adjustable resistance is played by a field effect transistor connected at the input. The saw-voltage generator 3 includes an amplifier-limiter, a counter trigger, an integrator with a discharge transistor switch, a comparator controlled by a sinusoidal reference voltage Uon, synchronized with a voltage UM, and an output bipolar transistor, not marked in the circuit, powered by auxiliary constant voltage Un.

The method is carried out as follows.

The input alternating voltage UM (Fig. 3 and 4) 8, which is fed to the signal inputs of the phase modulator 1 and the phase-shifting node 2, varies according to the law

and „„ andЈ

Where

B

J & .M "KC-einfct-K,

, W and H - amplitude, circular frequency and phase, respectively.

In the phase-shifting unit 2 under the influence of a constant control

stress

stress

Ua phase shift occurs

U,

4jt on the corner

at

Change

the voltage Uy, you can adjust the angle (initial phase shift) 9 from 0 to 180. Shaper 3 perceives the signal from the output of phase-shifting node 2 and generates a sawtooth voltage U3, which is modulating.

In the phase modulator 1, by means of the voltage Us, the phase of the sinusoidal voltage continuously shifts towards the lag with a speed equal to the circular frequency CJ, i.e. according to law . The phase shift created by each cascade of modulator 1 is proportional to the modulating sawtooth voltage 1 and increases linearly over a period. The total two-cascade phase shift is 360 °.

As can be seen from the diagrams of FIG. 3 and 4,

you

as a result, the bottom voltage U is constant. In this case, the magnitude and sign of U6fe | X depend on the value of the angle 8. For example, angle 6, (fig.Z) corresponds to positive U6fcvҐ, and angle 92 (FigoA) corresponds to negative ie)

The proposed technical solution almost completely excludes the presence of higher harmonics in the output

he senses their absence from the current network.

Claims (1)

Invention Formula A method of converting an alternating voltage into a constant, based on phase modulation of an alternating voltage, characterized in that, in order to improve the quality of the conversion by eliminating pulsations in a constant voltage, from a priori selected instantaneous value of an alternating voltage corresponding to the required level constant voltage, change the modulation depth with the frequency of the alternating voltage according to a linear law. FIG. g four frNy / N - / - v Zfr "r " v / / / t OfcteJ a) t " F1 / & 4 at