SU738014A1 - Piezoelectric transformer - Google Patents

Description

(54) PIEZOELECTRIC TRANSFORMER

The invention relates to the field of radio electronics and can be used in low-voltage converters DC

Piezoceramic transformers in the form of rectangular plates with active regions (with polarized coatings and electrodes) are known, each about 0.5 times the length of plate 1. The maximum input efficiency of most of them has a significant capacitive reactive component, and therefore, the low ratio of active power consumption to total input (cos). In order to compensate for the input capacitance, inductance is usually used that is connected in parallel or in series with the input. Its use creates additional difficulties associated with the manufacture of high-quality inductances, designed for large currents. If the load deviates from the noxscale, the compensating inductance must be rearranged. The presence of a winding element (which can actually perform the role of a transformer with minor changes (made of

secondary winding) reduces the advantages of piezoelectric transformers as non-winding.

A piezoelectric transformer, containing a rectangular, plate with a transversely polarized piezoactive region, having electrodes deposited on the plate surfaces, and a longitudinally polarized-piezoactive region, which is adjacent to the transversely polarized, has one electrode, located on the end of the plate, perpendicular to the face gran m plate 2.

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The disadvantages of this device are the low efficiencies and the ratio of the active input power to the total input power in a wide range of varying loads.

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The purpose of the invention is to increase efficiency and increase the ratio of active input power to total input power over a wide range of varying loads.

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The goal is achieved by the fact that the plate is made with a passive area located at the end of the plate opposite to the face electrode of the longitudinally polarized area; but

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also by the fact that the plate is made half-wave along the direction of longitudinal polarization, the longitudinally polarized region has a size of 0.2-0.32 plate length in the direction of longitudinal polarization, and the passin region has a size of 0.14-0.23 of the same length ; and the fact that the piezotransformer contains two quarter-wave plates along the longitudinal polarization direction, rigidly connected to each other along the end electrodes of the longitudinally polarized region, the total length of the longitudinally polarized region is 0.10,26 of the plate length in the direction of the longitudinal polarization, and the total length of the passive region is 0.03-0.09 of the same length.

Fig. 1 shows the proposed piezotransformer with a lateral arrangement of a longitudinally polarized region; in fig. 2 - the same with the central; in fig. 3 - hatched areas indicate the limits of variation of the frequency characteristic of the phase ula between current and voltage for a piezotransformer with passive areas (left hatching angle) and traditional, without passive areas (right slope of hatchings), when the load resistance changes; in fig. 4 shows the dependence of the transmission coefficient on voltage and current on frequency; in FIG. Figure 5 shows the experimental dependences of the ratio of the active input power to the total input power (cos P) at the self-compensation frequency of the input capacitance at different values of load resistance.

The piezotransformer (Fig. 1) has a transversely polarized region 1 with electrodes 2 and a longitudinally polarized region 3 with an end electrode 4, the passive region 5 is located at the edge of the plate opposite to the end electrode 4. The longitudinally polarized region Zo The sinusoidal voltage generator is connected to clips b and 7, load - to clips 7 and 8. On fig. Figure 2 shows a piezoelectric transformer consisting of two plates interconnected by an end electrode 4 and a longitudinally polarized region 3. The electrodes of the transversely polarized regions 2 are connected to each other. The purpose of the parts of this piezotransformer is the same as that of the transformer shown in FIG. 1.

After the electrical / voltage is connected to the terminals 6 and 7, a longitudinal wave begins to propagate in the plate in the direction of the longitudinal polarization vector due to the effect of the plasma effect. It creates a potential difference across electrodes 2 of transversely polarized region 1, which is removed from terminals 7 and 8. To maximize the effective coupling factors, it is necessary to adjust the dimensions of the passive and active regions. They are determined by the static, coupling coefficients of the K- and K of the piezomaterial. The selection of the operating frequency of the generator is illustrated by the graph in FIG. 3. On it, the hatched area 9 indicates the limits of the phase angle between the current and the voltage at the input of the piezotransformers shown in FIG. 1 and 2. Area 9 has one point corresponding to the self-compensation frequency indicated on the graph f, in which the phase angle is zero and does not change with load fluctuations. Therefore, the choice of this frequency as a working one is optimal precisely for present piezotransformers because, in a known longitudinal-transverse transformer, the frequency of self-condensation changes with load fluctuations (area 10 in Fig. 3, which determines the limits of change in phase angle φ, in contrast to from region 7 is not staggered to a point on, forward my P O).

It should be noted that the self-compensation frequency is between the maxima of the voltage gain and current (curves And and 12 in Fig. 4),

The results of the experiments showed a higher efficiency of transformers made from various grades of piezoelectric ceramics, the dimensions of which are chosen according to the invention, comparatively, with the known technical solutions.

Claims (3)

1. A piezoelectric transformer containing a rectangular plate with a transversely polarized piezoactive region having electrodes deposited on the plate surface and a longitudinally polarized piezoelectric region that is adjacent to the transversely polarized one has an electrode located at the plate end perpendicular to the side face plate, characterized in that, in order to increase the efficiency and the ratio of the active input power to the total input power in a wide range of varying loads, the plate is made with a passive area located at the end of the plate opposite to the end electrode of the longitudinally polarized region. 2. The transformer according to claim 1, said that the plate The half wavelength along the direction of the longitudinal polarization is made, the longitudinally polarized region has a size of 0.2-0.32 plate length in the direction of the longitudinal polarization, and the passive region has a size of 0.14-0.23 from the same length. 3. A transformer according to claim 1, characterized in that it comprises two plates, made quarter-wave along the direction of the longitudinal polarization of the plate, rigidly interconnected along the end electrodes of the longitudinally polarized region, the total length of the longitudinal but the polarized region (is 0.1-0.26 the length of the plate in the direction of the longitudinal polarization, and the total length of the passive region is 0.03-0.09 of the same length. Sources of information taken into consideration 1. Lavrinenko V.V. Piezoelectric transformers, M., Energie, 1975, p. 19g-27. 2. Magnetic and dielectric. appliances. Ed. G.V. Gatts per. from English M.-L., Energie, 1969, with. 197. F5 Frequency YY.-1