RU2224351C2 - Electronic transformer - Google Patents

Abstract

FIELD: electronic engineering. SUBSTANCE: proposed bidirectional electronic transformer capable of voltage conversion following its waveform has pass-band ranging between dc and high-frequency currents when its equivalent windings are electrically isolated, this pass-band being independent of conversion frequency; it is noted for low dynamic loss and low level of external noise and has two alternately turned on parallel energy transmission channels with spanned on-time; each of them is, essentially, single-ended uncontrolled pulsed transformer converter with energy transferred in active phase (when switches are open) incorporating symmetric or asymmetric switches connected in series with all windings, as well as demagnetizing windings, switching circuits, and common control circuit. EFFECT: improved frequency characteristics, reduced size and mass. 4 cl, 3 dwg

Description

 The invention relates to converters of direct and alternating voltage and can be used in electrical and radio engineering.

 A device of an electric transformer is known that converts an electric current, voltage or resistance from one value to another (A. Losev, "Linear Radio Engineering Circuits", Higher School, 1971), consisting of one primary and one or more secondary windings inductively coupled between themselves.

An electric transformer has features that limit its scope:
1. The transformer operates only on alternating current.

 2. When operating at low frequencies in the magnetic circuit of the transformer, a ferromagnetic core is used, which has significant mass and dimensions.

 3. When working in a wide range of frequencies in signal amplification and conversion devices, it is difficult to ensure uniform transformer parameters across the range.

 Known devices for converting electrical energy from one type and (or) values to another, operating in a pulsed mode (V. Kolosov, "Power supply of stationary electronic equipment", Radio and communication, 1992) and consisting of various combinations of such functional elements, as rectifiers, filters, controlled and uncontrolled inverters, amplifiers, comparators, etc.

The overall dimensions of these devices may be better than those of transformers, but they have one or another of the following disadvantages:
1. Significantly lower efficiency compared to an electric transformer.

 2. Large interference in external circuits.

 3. Significant distortion of the waveform when transmitting AC voltage.

 4. The presence of galvanic communication between input and output.

 Their scope is power transformations of direct and alternating voltage without preserving its shape.

 The closest in technical essence is the device described in the application 93049617/07 (RU) dated 10.27.1993, "Converter (regulator) of an alternating voltage (its variants)" and consisting of a symmetric or asymmetric key connecting the input voltage source and the primary winding a transformer, a secondary winding and a symmetric key shunting the primary winding, and the control terminals of the keys are connected to a source whose output frequency is much higher than the input voltage frequency.

 Such a device is capable of converting both direct and, without directly rectifying, alternating voltage.

 The disadvantages of this device are the inability to convert while maintaining the shape of the input voltage, a narrow frequency range of the input voltage, significant losses.

 The aim of the present invention is the creation by means of pulse technology of a device, hereinafter referred to as electronic transformer (ET), similar in properties to an electric transformer, i.e. bidirectional, with galvanic isolation of equivalent windings, operating in a wide frequency range, preserving the shape of the input voltage and having an increased (with respect to pulsed devices) efficiency, but having better frequency and weight parameters.

 This goal is achieved by the fact that in the known device, consisting of a symmetric or asymmetric electronic key connecting the input voltage source and the primary winding of the transformer, secondary winding, demagnetization circuits and control device, a symmetric or asymmetric key is added in series with the secondary winding, connecting it to the output moreover, there can be several secondary windings, and corresponding keys and outputs, each winding and a key connected to it form an equivalent winding and the transformer together with equivalent windings forms one power block, one or two demagnetizing windings are added, the same power block with demagnetizing windings is added, combined with the inputs and outputs described above in parallel, the keys of both blocks are controlled so that the keys are in open state (active phase) sequentially one after another with the active phases of both blocks overlapping, and the demagnetizing winding of the transformer of each block through a switching circuit connected either with a dissipative device, or with a voltage source.

 Achievement of the goal became possible due to the fact that the conversion of the input voltage to the output is carried out through two parallel channels by two single-cycle unregulated transformer converters with energy transfer in the active phase, having switching elements in all windings and circuits to eliminate magnetization and working sequentially one after another with overlapping active phases.

 Figure 1 shows the block diagram of the ET, figure 2 shows an example of the implementation of a symmetric high-voltage high-current switch on bipolar transistors, figure 3 shows the timing diagrams of the ET.

 ET consists of two identical power units 1 and 2, a control device 3 containing a control circuit for power units 4, and demagnetization circuits 5.

 Power blocks are connected in parallel at inputs 6, 7 and outputs 8, 9.

 Both power units contain identical high-frequency pulse transformers, the primary windings 10 and 11 of which are connected via input keys 12 and 13 to input 6, 7. Secondary windings 14 and 15 are connected via output keys 16 and 17 to output 8, 9.

 The outputs of the control circuit of the power blocks 4 of the control device 3 are connected to the control inputs 18-21 of the electronic keys 12, 13, 16, 17.

 The demagnetization circuits 5 contain demagnetizing windings located on both transformers, which are connected via a switching circuit to a dissipative device or to a voltage source, which can be used as either an additional voltage source or an additional demagnetizing winding of another transformer.

 The device operates as follows.

 The input signal 22 through controlled electronic switches 12, 13 is supplied to the primary windings 10, 11 of the pulse transformers of the power units 1, 2, secondary windings 14, 15 of which are connected to the output 8, 9 through similar keys 16, 17.

The control inputs of the electronic keys 18, 20 of the power unit 1 from the control circuit of the power units 4 of the control device 3 are fed galvanically isolated unlocking pulses 23, 24 with a period T
and duration τ either
τ = T / 2 (meander),
or
τ> T / 2 (overlapping pulses),
the same pulses 25, 26, but with a temporary shift of T / 2, are supplied to the inputs of the keys 19, 21 of the power unit 2, providing for the overlap (simultaneous presence in the active phase) of both channels, resulting in output 8, 9 from the power unit 1 pulses 27 are allocated, and from the power unit 2 pulses 28 are allocated, the envelope of which follows the shape of the input voltage.

 The use of impulses in the form of a meander for key management is possible due to the inertia of the keys, but to ensure guaranteed overlapping of channels, it requires careful selection of the element base and operating modes.

 As a result of combining, by OR, two sequences of overlapping pulses 27 and 28 at the output 8, 9, an undistorted, transformed relative to the input, output signal 29 is extracted, undistorted in the sense that the device assembled on idealized elements when operating from an ideal voltage source for an arbitrary load does not cause distortion. In real conditions, distortions are always present, but can be reduced to the required value by choosing the elemental base and its operating modes.

 During the passive phase of the channel, the primary and secondary windings of the corresponding transformer are turned off and the magnetic induction energy accumulated in its core (magnetization energy) is output through its demagnetizing winding to a voltage source or dissipative device, and by fluctuations of this energy, which can be several orders of magnitude less energy transferred to the load, interference in the external circuits of the converter is determined. Since the time of the passive phase is less than the time of the active phase, for the complete output of the magnetization energy, the voltage of the additional source receiving this energy must be greater than the voltage on the demagnetizing winding during the active phase, and, if an active channel transformer is used to receive energy, it must have a receiving additional demagnetizing winding with a larger than the main number of turns.

 Since a change in the state of one channel occurs when another channel is open and does not cause the switching of the load current, the dynamic losses in the keys are determined only by the discharge of the output capacities when switching on and switching the magnetization currents of the cores upon switching off. An additional reduction in losses is achieved by returning the magnetization energy of the cores during the passive phase to a voltage source operating as a successor. The bandwidth of such a ET is independent of the switching frequency and ranges from DC to a frequency determined by the RF parameters of pulse transformers. The absence of distortion is determined by the constancy of the transmission coefficient of the device at any time. Bidirectionality is related to the symmetry of the transducer. Small dynamic losses allow you to increase the conversion frequency and, as a result, improve overall dimensions.

 Depending on the properties of the keys used in ET (symmetric or asymmetrical), the sign of its valid input signals changes. In ET with asymmetrical keys, constant and unipolar alternating voltage of the corresponding sign are permissible, and in ET with symmetric keys all kinds of signals are permissible.

 Due to the low level of external interference created, in many cases one can dispense with their additional suppression. If necessary, you can use either a simple capacitive filter with preserving the efficiency, but with a narrowing of the passband, or an interference compensation scheme with preserving the passband, but with a decrease in the efficiency. A feature of ET associated with its bidirectionality is that one capacitor connected to any of its equivalent windings will have a filtering effect on all windings.

 If complete symmetry (equality of impedances relative to the common wire) of the terminals of any of the equivalent ET windings is required, then this winding can be made in the form of two sections with an equal number of turns and transfer of the corresponding key to the place of their connection.

 Since the ET is not a fully functional stand-alone device, its block diagram does not show some of the nodes necessary or desirable for its operation, but not directly related to the invention, namely, the power supply, filtering circuits, overload protection device, etc.

Claims (4)

1. Electronic transformer (ET), consisting of a primary winding of a pulse transformer and an electronic key connected in series and connected to the input terminals of ET, secondary windings of a pulse transformer, demagnetization circuits and control circuits, characterized in that an electronic key is introduced in series with each secondary winding connecting this winding to the individual output terminals of the ET, the primary and secondary windings, together with the corresponding keys, form one power unit, to the input and output terminals zhimam ET second parallel connected of the same power unit, and the total control circuit comprises a power generator unit control pulses, the outputs of which are galvanically separated and connected to the inputs of the electronic switches. 2. ET according to claim 1, characterized in that the cores of both pulse transformers have one demagnetizing winding connected by switching circuits to a dissipative device. 3. ET according to claim 1, characterized in that the cores of both pulse transformers have one demagnetizing winding connected by switching circuits to an additional voltage source. 4. ET according to claim 1, characterized in that the cores of both pulse transformers have one demagnetizing winding and one additional demagnetizing winding connected by switching circuits so that the demagnetizing winding of the transformer of each channel is connected to the additional demagnetizing winding of the transformer of the other channel.

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