RU2210852C1 - Single-phase bridge-type transistor inverter with inverse diode bridge - Google Patents

Abstract

FIELD: electrical engineering; single-phase bridge-type inverters. SUBSTANCE: novelty is that known device widely used in miscellaneous secondary power supplies for power capacities from tens of watt (domestic video and audio appliances) to several kilowatts (inverter-type electric welding machines, small plasmatrons, and the like) is provided with single-phase bridge-type transistor inverter with inverse diode bridge. Inverter is connected across diagonally opposite dc terminals to power supply and across diagonally opposite ac terminals, to primary winding of matching power transformer through in-series-connected capacitor. Secondary winding of mentioned matching power transformer is coupled with load through diode rectifier and smoothing choke. Mentioned transformer is provided with auxiliary winding whose turn number is twice as small as that of primary winding. Mentioned auxiliary winding is connected across diagonally opposite ac terminals of inverse diode bridge isolated from diagonally opposite ac terminals of bridge-type transistor inverter. Such design has made it possible to return reactive power to power supply during each half-cycle of inverter bypassing capacitor thereby eliminating voltage resonance at any combination of parameters of matching power transformer and capacitor. EFFECT: ability of eliminating voltage resonance in single-phase bridge-type inverter. 1 cl, 3 dwg

Description

 The present invention relates to the field of electrical engineering, namely to single-phase bridge inverters with transistors. Single-phase inverters are widely used in various secondary power sources in the power range from tens of watts (household video and audio equipment) to several kilowatts (inverter-type electric welding machines, small plasma torches, etc.).

 Known single-phase bridge inverters containing a transistor bridge of four power transistors connected by a diagonal of direct current to the power source, and by a diagonal of alternating current to the load. The power source is usually a network diode or diode-thyristor bridge rectifier with a filter capacitor at the output, and the load contains a power matching transformer, the secondary winding of which is connected to the load itself through a diode rectifier and a smoothing inductor. To return reactive power, the transistor bridge is shunted by a reverse diode bridge (see p. 317, Fig. 29.5 in the book by V. A. Pryanishnikov. Electronics. St. Petersburg "Crown Print", 1998, 400 pp., Sources secondary power supply. Edited by Yu.I. Konev. M: Radio and communications, 1983).

 The high frequency at the inverter output can dramatically reduce the dimensions of the power matching transformer. Modern manufacturers of inverter-type power supplies bring the frequency of inverters to 100 kHz [3] (see "Transpoket" - Austria, Catalog 1995-6, "DC200 A1 - Technotron" - Russia, "Invertec V-130- S "- Linkoln - USA).

 However, increasing the frequency of the inverter causes a number of problems: switching losses in power transistors and other semiconductor elements of the inverter increase; requirements for the frequency characteristics of the element base are growing and, therefore, its cost is growing; Due to the inevitable asymmetry in the diagonal of the alternating current of the transistor bridge, a constant component appears, which makes the bridge circuit ineffective. The transformer must be performed with a gap in the core and used only on the private hysteresis loop. It is the last of these problems that led to the transition from the "classical" bridge inverters to single-cycle inverters [3].

 The closest device of the same purpose to the claimed invention in terms of features is a device in which a capacitor is connected in series with the primary winding of the power matching transformer and, thus, the DC component in the output voltage of the inverter is excluded (see RF patent 2131640, B.I. 16 , 1999, prototype).

 The reasons that impede the achievement of the technical result indicated below when using the prototype include the fact that a known device may cause voltage resonance in the diagonal of an alternating current of a single-phase bridge inverter.

A simplified circuit of the prototype is shown in figure 1 and contains a transistor bridge 1, 2, 3, 4 of four power transistors connected by a diagonal of a direct current to a power source, and a diagonal of an alternating current through a power matching transformer 5, a diode rectifier 6 and a smoothing inductor 7 directly to the load 8. A capacitor 10 is connected in series with the primary winding 9 of the power matching transformer 5. The secondary winding 11 of the power matching transformer 5 is connected to the input of the said rectifier 6. Trans The bridge 1, 2, 3, 4 is shunted by the reverse diode bridge 12, 13, 14, 15. The capacitor 10 does not pass the DC component, so the transformer 5 can be closed-core, used on a full hysteresis loop, which allows 2-4 times , depending on the parameters of the core, reduce its overall dimensions at a given frequency or maintain these indicators, reducing the frequency, respectively, by 2-4 times. However, the presence of a series LC circuit, where L is the inductance of transformer 5 and C is the capacitance of capacitor 10, can lead to voltage resonance at one of the harmonics, even if X _L ≠ X _C at the fundamental, where X _L and X _C are transformer reactants and capacitor.

 EFFECT: elimination of voltage resonance in a single-phase bridge inverter with a capacitor in the power matching transformer circuit.

 The specified technical result during the implementation of the invention is achieved by the fact that in a known device containing a single-phase bridge transistor inverter with a reverse diode bridge, connected by a diagonal of a direct current to a power source, and by a diagonal of an alternating current connected through a series-connected capacitor to the primary winding of the power matching transformer, the secondary winding which is connected to the load through a diode rectifier and a smoothing inductor. Said power matching transformer is equipped with an additional winding with a number of turns half as large as that of the primary winding, with the additional winding connected to the diagonal of the alternating current of the reverse diode bridge, not connected to the diagonal of the alternating current of the bridge transistor inverter.

 This made it possible to carry out the return of reactive energy in each half-cycle of the inverter operation back to the power source, bypassing the capacitor and, thus, eliminating voltage resonance for any combination of parameters of the power matching transformer and capacitor.

 The analysis of the prior art by the applicant, including a search by patent and scientific and technical sources of information and identification of sources containing information about analogues of the claimed invention, allowed to establish that the applicant did not find an analogue characterized by features identical to all the essential features of the claimed invention. The definition from the list of identified analogues of the prototype as the closest in the set of essential features of the analogue made it possible to identify the set of essential distinguishing features in relation to the applicant's technical result in the claimed device set forth in the claims.

 Therefore, the claimed invention meets the condition of "novelty."

To verify the compliance of the claimed invention with the condition "inventive step", the applicant conducted an additional search for solutions to identify signs that match the distinctive features of the claimed device from the prototype. The search results showed that the claimed invention does not derive explicitly from the prior art for the specialist, since the influence of the transformations provided for by the essential features of the claimed invention on the achievement of the technical result is not revealed from the prior art determined by the applicant, in particular, the following transformations are not provided for by the claimed invention:
- addition of a known product by any known part (s) attached to it according to known rules to achieve a technical result in respect of which the effect of such additions is established;
- replacement of any part (s) of a known product with another known part to achieve a technical result, in respect of which the effect of such a replacement is established;
- the exclusion of any part (element) of the product with the simultaneous exclusion of the function due to its presence and the achievement of the usual result for such exclusion (simplification, reduction of mass, dimensions, material consumption, increased reliability, etc.);
- an increase in the number of elements of the same type to enhance the technical result due to the presence in the tool of just such elements;
- the implementation of a known tool or part (s) of a known material to achieve a technical result due to the known properties of this material;
- the creation of a tool consisting of known parts, the choice of which and the relationship between them are based on known rules, recommendations, and the technical result achieved in this case is due only to the known properties of the parts of this tool and the relationships between them.

 The described invention is not based on a change in a quantitative sign (s), the presentation of such signs in relationship or a change in its form. This refers to the case when the fact of the influence of each of these characteristics on the technical result is known and new values of these signs or their relationship could be obtained on the basis of known dependencies and patterns.

 Therefore, the claimed invention meets the condition of "inventive step".

 The invention is illustrated by drawings, where figure 2 presents a diagram of a single-phase bridge inverter, figure 3, a, b, c - timing diagrams, and figure 3, d - dependence of voltage on current.

 The device contains a transistor bridge of four power transistors 1, 2, 3, 4, connected by a diagonal of direct current to the power source, and by an diagonal of alternating current through a power matching transformer 5, a diode rectifier 6 and a smoothing inductor 7 to the load 8. In series with the primary winding 9 The power matching transformer 5 includes a capacitor 10. The secondary winding 11 of the power matching transformer 5 is connected to the input of the diode rectifier 6. The reverse diode bridge 12, 13, 14, 15 with a diagonal of direct current li ne to a power source, and the diagonal ac, non-diagonal AC bridge transistor inverter to the additional winding 16 of the power matching transformer 5.

The device operates as follows. If there is a voltage of the power supply U ₁ * (Fig. 3, a) and the inclusion of one of the diagonal pairs of power transistors, for example 1 and 4, through the capacitor 10, the voltage of the power supply plus the voltage of the capacitor 10 is applied to the primary winding 9 of the power matching transformer 5. idling, when only the magnetizing current of the power matching transformer 5 flows through the capacitor 10, the voltage amplitude U _c * on the capacitor 10 is small (Fig. 3, b). With an increase in the load current, the voltage amplitude across the capacitor 10 increases accordingly. When the power transistors 1 and 4 are locked, the electromagnetic energy stored in the power matching transformer 5 through the additional winding 16 and the reverse diode bridge 12, 13, 14, 15 is discharged to the power source. For better magnetic coupling, this winding is wound into the primary winding 9 of the power matching transformer 5, and the number of its turns is half that of the number of turns of the primary winding 9. This condition requires that the voltage transformed into an additional winding 16 with the power transistors of any diagonal pair turned on is no more in amplitude of the voltage of the power source.

Thus, the return of reactive energy to the power source is possible only during pauses when switching diagonal pairs of power transistors 1, 2, 3, 4. When the load current I _d reaches a certain "critical" value I _d = I _kp (Fig.3, g ) the amplitude of the voltage U _c * on the capacitor 10 reaches a maximum, that is, the voltage of the power source. The voltage on the primary winding 9 at the moments of switching the next diagonal pair of power transistors reaches the double voltage of the power source. A further increase in the voltage amplitude across the capacitor 10 and, accordingly, on the primary winding 9 of the power matching transformer 5 is impossible, therefore, with a further increase in the load current I _d > I _kp in the rectified voltage U _2d * (Fig. 3, c), sections of zero value appear, and in the current of the power matching transformer - pauses. The average rectified voltage U _d * begins to decrease (Fig. 3, d) and the external characteristic of the inverter turns from linear to hyperbolic: U _d * • I _d = const. It is worth noting that if the linear section of the external characteristics of the device (in Fig. 3d, this section is shown absolutely rigid for simplicity, that is, without taking into account the impedance of the device) is suitable for most electrical and electrotechnological installations, then the section of constant power U _d * • I _d = const is ideal, for example, for electric arc welding in air. As mentioned, the capacitor 10 eliminates the constant component in the current of the power matching transformer 5, and the additional winding 16 of this transformer performs a cyclic return of reactive energy to the source, thereby eliminating voltage resonance. The power transmitted by the additional winding 16 to the power source is very small, especially if the transformer core is made of iron with a rectangular hysteresis loop and a small magnetizing current, so the additional winding 16 practically does not increase the copper volume of the power matching transformer. The necessary technical result is achieved by a simple means.

Thus, the above information indicates the following conditions are met when using the claimed device:
- a tool embodying the claimed device in its implementation, is intended for use in industry, namely in the field of electrical engineering;
- for the claimed device in the form as described in the independent clause of the claims, the possibility of its implementation using the means and methods described in the application is confirmed;
- a tool embodying the claimed invention in its implementation, is able to ensure the achievement of the perceived by the applicant technical result.

 Therefore, the claimed invention meets the condition of "industrial applicability".

Claims (1)

 A single-phase bridge transistor inverter with a reverse diode bridge, connected by a diagonal of a direct current to a power source, and a diagonal of an alternating current through a series-connected capacitor, to the primary winding of a power matching transformer, the secondary winding of which is connected to a load through a diode rectifier and a smoothing inductor, characterized in that said power matching transformer is equipped with an additional winding with a number of turns half as small as that of the primary winding, and The winding is connected to the diagonal of the alternating current of the reverse diode bridge, which is not connected with the diagonal of the alternating current of the bridge transistor inverter.

Images