RU2821803C1 - Shuvaev's multiphase resonant voltage converter - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: invention relates to the field of electrical engineering, in particular, converting equipment, and can be used in the design and development of secondary power supplies for various purposes. Multiphase resonant converter contains k power cascades, each of which consists of charging and discharging key transistors, resonant capacitor and choke, transformer with charging and discharging primary and secondary windings, as well as a rectifier unit consisting of a set of forward and reverse diodes and a smoothing filter, and a control device. Charging transistor, capacitor, choke and charging primary winding of the transformer are connected in series, connected to the power supply terminals and form an oscillating resonant charging circuit, discharge transistor and discharge primary winding of transformer are also connected in series, connected to terminals of series-connected capacitor and choke and form discharge circuit. Terminals of the rectifier unit are connected to the terminals of the secondary windings of the transformer. Control device consists of the number of channels corresponding to the number of transistors and provides the supply of control pulses to the base of the transistors of the charging and discharging circuits alternately, during each half-period of their on state, time intervals are provided between charging and discharging control pulses and half-periods of natural oscillations of the resonant circuit, control pulses are supplied with time intervals between them, duration of control pulses remains constant in all operating modes of the converter.

EFFECT: reduction of volume and weight and increase of efficiency of resonant voltage converter due to reduction of power losses in key transistors at their switching and improvement of coefficients of using elements by current, voltage and power.

4 cl, 17 dwg

Description

The invention relates to the field of electrical engineering, in particular converter technology, and can be used in the design and development of secondary power supplies for various purposes.

Various resonant voltage converters are known, containing key transistors, a transformer and a resonant circuit consisting of a capacitor and an inductor, providing an almost sinusoidal shape of the current curve in power circuits, switching transistors at a minimum value of the current flowing through them and, as a result, having minimal dynamic power losses [1-6].

The disadvantage of these converters is the large volume and weight of the elements and relatively low efficiency.

The closest to the proposed technical solution, which can be accepted as a prototype, is a half-bridge resonant voltage converter containing two MOS transistors with freewheeling diodes, a resonant capacitor and inductor, a transformer, a rectifier and a smoothing filter [6].

The proposed multiphase resonant voltage converter ensures a reduction in the volume and weight of elements and an increase in efficiency by improving the circuit and further reducing power losses when switching transistors because their switching on and off is carried out at completely zero current in the switching circuit, as well as eliminating through currents when switching transistors.

To achieve the technical result, the proposed converter uses several cascades (conversion cells), consisting of charging and discharging oscillatory resonant circuits, including a key transistor, a resonant capacitor and inductor, and the primary winding of the transformer. The charging circuit ensures the transfer of energy from the power source to the capacitor and the load during the first half-cycle, and the discharge circuit ensures the discharge of the capacitor and also transfers energy to the load during the second half-cycle.

The advantage of the proposed converter is that it transfers energy to the load during both half-cycles of transistor switching when charging capacitors and when discharging them. Unlike known circuits, a unipolar voltage is applied to the resonant capacitors during both half-cycles, which allows the use of polar capacitors that have better volume-mass characteristics compared to non-polar ones.

From the foregoing it can be concluded that the proposed invention allows one to obtain a positive result.

The position numbers of the elements of the converter circuits, the designation of currents, voltages and other parameters of the elements related to the first, second and third stages are marked, respectively, with one, two and three strokes; relating to charging and discharging circuits and transistors, respectively, with the indices “z” and “p”; relating to the primary and secondary windings of transformers, respectively, with indices “1” and “2”.

Elements and components of converter circuits:

1, 2 - charging and discharging key transistors; 3 - resonant capacitor; 4 - resonant choke; 5 - transformer; 6, 7 - charging and discharging primary windings of the transformer; 8, 9 charging and discharging secondary windings of the transformer; 10 - rectifier unit; 11 - set of direct diodes; 12 - set of reverse diodes; 13 - smoothing filter.

Main parameters of the converter and their designation:

U _p - power source voltage;

U _n , I _n - load voltage and current;

k - number of converter stages;

m - number of converter phases;

ϕ is the phase shift angle between the control pulses of the two cascades;

u _uz , u _ur - voltage of charging and discharging control pulses;

u _сз , u _cp - voltage on the capacitor during charge and discharge;

i _1з , i _1p - current of the charging and discharging primary windings of the transformer;

i _2з , i _2p - current of the charging and discharging secondary windings of the transformer;

u _2з , u _2p - voltage on the secondary windings of the transformer;

τ ₁ , τ ₂ - duration of half-periods of natural oscillations of the circuit;

f=1/(τ ₁ +τ ₂ ) - frequency of natural oscillations of the circuit;

Δτ ₁ , Δτ ₂ - time intervals between control pulses and half-periods of the circuit’s own oscillations;

t ₁ , t ₂ - duration of control pulses;

Δt ₁ , Δt ₂ - duration of time intervals between control pulses;

T=(t ₁ +Δt ₁ )+(t ₂ +Δt ₂ ) - switching period of transistors;

F=1/T - switching frequency of transistors.

The application presents circuits of resonant voltage converters with the number of stages k=1, 2, 3 and the number of phases m=2, 4, 6. The main initial data for these converters are given in Table 1.

The block diagram of a single-stage resonant voltage converter with the number of stages k=1 and the number of phases m=2 is shown in Fig. 1. The converter contains the first 1' and second 2' key transistors, a resonant capacitor 3', a resonant choke 4', a transformer 5' with a charging 6' and a discharge 7' primary and 8', 9' secondary windings, as well as a rectifier unit 10 and a control device (not shown in the diagram of Fig. 1).

Transistor 1', primary winding 6' of transformer 5', capacitor 3' and inductor 4' are connected in series, forming an oscillatory resonant charging circuit and connected to the terminals of the power source. The transistor 2' and the primary winding 7' of the transformer 5' are also connected in series, form a discharge circuit and are connected to the free terminals of a series-connected capacitor 3' and inductor 4'. The secondary windings 8', 9' of the transformer 5' are connected in series and in accordance with each other, and their free terminals and the common point are connected, respectively, to the input terminals a, b, 0 of the rectifier unit 10, consisting of a set of forward 11 and reverse 12 diodes and a smoothing filter 13. Rectifier node 10 (Fig. 2) is made according to the rectifier circuit described in [9], and has improved volumetric, mass and energy characteristics compared to traditional rectifiers.

Diagrams of currents and voltages on the elements of the converter, the diagram of which is shown in Fig. 1 are presented in Fig. 3. The duration of the half-cycles of natural oscillations of the charging and discharge circuits depends on the capacitance of the resonant capacitor and the inductance of the resonant choke, which are selected when designing and calculating the converter. The calculated duration of control pulses t ₁ ' and t ₂ ' must be greater than the duration of half-periods of the circuit's natural oscillations τ ₁ ' and τ ₂ ', which ensures the control device of the converter in all modes of its operation. Between the control pulses u _з ' and u _ur ' and the voltage pulses on the capacitor u _сз ' and u _ср ' time intervals Δτ ₁ ' and Δτ ₂ ' are provided in order to exclude the possibility of premature closing of the transistors at a finite (non-zero) circuit current and ensure minimal dynamic power losses when the transistors are turned off. The minimum value of Δτ ₁ ' and Δτ ₂ ' must be sufficient to provide time for carrier resorption in the base junction of the transistors.

Regulation and stabilization of the converter output voltage is carried out by an automatic control system of the control device for changing the time intervals between control pulses Δt ₁ ' and Δt ₂ ', and their minimum value must be no less than Δτ ₁ ' and Δτ ₂ '. With this control method, the period T and switching frequency F of the transistors change.

When the converter operates in output voltage stabilization mode at a minimum power supply voltage U _p and a maximum load current I _n, the time intervals Δt ₁ ' and Δt ₂ ' have a minimum value, and the switching frequency of transistors F has a maximum. At maximum U _p and minimum L, time intervals - maximum, and frequency F - minimum.

A resonant voltage converter, the diagram of which is shown in Fig. 1 works as follows.

The charging and discharging circuits operate alternately with the switching frequency F of the key transistors 1', 2' in accordance with the control pulses u _uz ' and u _ur ' with duration t ₁ and t ₂ supplied by the control device to their bases. The duration of control pulses t ₁ , t ₂ is determined by the parameters of the converter and the nominal switching frequency of the transistors. Control pulses are supplied with time intervals Δt ₁ ' and Δt ₂ ' between them. When the transistor 1' is on, a resonant charge of the capacitor 3' occurs with the voltage of the power source through the specified transistor, the primary winding 6' of the transformer 5' and the resonant inductor 4'. During time t _1, a positive half-wave of current circuit i ₁₃ is formed, having a shape close to sinusoidal. The circuit current is transformed and transmitted to the load through the secondary winding 8' of the transformer 5' and the rectifier unit 10'.

When the transistor 2' is turned on, a resonant discharge of the capacitor 3' occurs. The discharge current of the circuit during time t ₂ flows through the transistor 2', the primary winding 7' and the resonant inductor 4'. In this case, similarly to the positive one, a negative half-wave i _1р is formed, which is also transmitted to the load.

At the beginning and at the end of each half-cycle of switching the transistors during the time intervals Δt ₁ ' and Δt ₂ ', both transistors are closed.

Switching dynamic power losses occur in transistors when they are turned on and off, at the beginning and at the end of each half-cycle of the process of charging and discharging a resonant capacitor. The reduction of these losses in the proposed converter in comparison with the known ones is ensured as follows.

At the beginning of both half-cycles, the circuit current is zero. When the transistor is turned on at the end of the time intervals Δt ₁ ', Δt ₂ ', when a control pulse is applied to the base of the transistor, it opens, its collector current begins to gradually increase and changes along a sinusoid during the duration of the control pulses t ₁ ', t ₂ ', reaches a maximum and begins to decline.

When the transistor is turned off, at the end of the half-periods of sinusoidal oscillations of the circuits τ ₁ ' and τ ₂ ', the voltage on the capacitor reaches a maximum or zero value, the circuit current becomes zero and remains zero during the time intervals Δt ₁ ' and Δt ₂ ', however The control voltage from the base of the transistor is not yet removed. At the end of the time intervals Δτ ₁ ', Δτ ₂ ', the control device removes control pulses from the base of the transistor and it closes at completely zero collector current.

During the described transient processes, the power loss when the transistors are turned on is very insignificant, and when turned off they are zero.

When the voltage converter operates, the sign on the capacitor does not change, which makes it possible to use polar capacitors in the circuit, which have a significantly smaller specific volume and mass than non-polar ones.

If it is necessary to ensure equality of the amplitude of the positive and negative voltage half-waves on the secondary windings of the transformer, its primary windings are made with a different number of turns.

Another version of the single-stage resonant voltage converter circuit is shown in Fig. 4 and fig. 5, and diagrams of currents and voltages on its elements are in Fig. 6. The differences between this converter and the one considered are that the currents and voltages on the charging and discharge windings of the transformer are in phase, one secondary winding of the transformer is used, and a set of direct diodes is excluded from the rectifier unit circuit. The last sign is explained by the fact that a unipolar voltage has already been generated at terminals a, 6 of the secondary winding of the transformer during both half-cycles of transistor switching. The function of direct diodes of the rectifier unit is performed by charging and discharging transistors.

The converter, made according to the circuits of Fig. 4 and fig. 5, works similarly with a converter assembled according to the circuits of Fig. 1 and fig. 2.

The advantages of the latter scheme are a smaller number of elements, their smaller volume and weight, as well as higher efficiency due to the elimination of direct diodes and, accordingly, power losses in them.

In fig. 7 shows a block diagram of a resonant voltage converter, which contains two power stages identical to the power stage, the diagram of which is shown in FIG. 1. Diagrams of the rectifier unit for a two-stage converter are shown in Fig. 8 and fig. 9. The control unit of this converter contains two channels that issue control pulses to switch the charging and discharging transistors of both stages.

In a two-stage converter (Fig. 7), the control pulses can be shifted in phase relative to each other by 180° and 90°. Diagrams of currents and voltages on the converter elements at the indicated phase shifts are shown respectively in Fig. 10 and fig. eleven.

The advantages of two-stage converters over single-stage ones are the uniform consumption of energy from the power source, as well as the fact that it is transferred to the load during both half-periods of the circuits’ operation.

An important advantage of a two-stage converter with a pulse shift of 90° degrees and the number of phases m = 4 is a twice higher frequency and a significantly lower level of ripple of the rectified voltage at the input of the smoothing filter.

Four-phase rectifiers, which have an optimal number of phases and a low ripple level, are practically not used with a sinusoidal alternating supply voltage due to the complexity of creating a system of four vectors shifted in phase by an angle of 90°. In the proposed converter (Fig. 7) this problem is solved quite simply.

Power stages in converters made according to the circuits of Figs. 7 - fig. 9 operate similarly to the converter stage of FIG. 1. Parallel summation of the currents of the charging and discharge circuits of both cascades is carried out in the rectifier units (Fig. 8, Fig. 9).

In fig. 12 and fig. 13 shows block diagrams of another version of a two-stage converter, and FIG. 14 diagrams of currents and voltages on their elements. Unlike the converter of FIG. 7, the currents and voltages of the charging and discharging primary windings of the transformer in this converter are in phase, one secondary winding is used in each stage, and a set of direct diodes is excluded from the rectifier assembly. The operating principle of this converter is similar to the operating principle of the converter in Fig. 4, fig. 5.

The block diagram of a three-stage converter (k=3, m=6) is shown in Fig. 15, and diagrams of its rectifier units are shown in Fig. 16 and fig. 17. In this converter, the phase shift between control pulses is 60°. This ensures the number of converter phases m=6, i.e. high frequency and low level of ripple of the rectified voltage at the input of the smoothing filter.

The invention is new, because no analogues with a similar set of essential features have been found in the available sources of information.

What is new in the invention is the use in a resonant voltage converter of several cascades (cells), consisting of charging and discharging circuits, each of which includes a key transistor, a resonant capacitor, a resonant inductor and a primary winding of the transformer. When charging and discharging a capacitor, energy is converted, transformed and transferred to the load.

The application proposes a new class of voltage converters, which can be developed and expanded using the proposed and other similar power stage circuits.

Literature

1. US Patent No. 4263642.

2. Sources of secondary power supply. Ed. Yu.I. Konev - 2nd ed., revised. and additional - M.: Radio and communication, 1990, p. 118-128.

3. RF patent No. 2110881, N02M 7/523.

4. RF Patent No. 2186452 N02M 7/335.

5. RF Patent No. 2459342 N02M 7/335.

6. Development of a resonant half-bridge LCL converter. Hong Huanq. TI Literature Number: SL U263. Translated for the website http: valvolodin.ru.

7. Shuvaev Yu.N., Vilenkin A.G. Multiphase pulse stabilizers. - On Sat. Electronic technology in automation / Ed. Yu.I. Koneva. - M.: Soviet radio, 1997, issue. 9, p. 70-83.

8. Moeen B.C. Stabilized transistor converters. - M.: Energoatomizdat, 1986, pp. 233-239.

9. RF Patent No. 2788181С1 Н02М 7/06. Low voltage multiphase rectifier. Author Shuvaev Yu.N.

Claims (4)

1. A multiphase resonant voltage converter containing a power cascade consisting of charging and discharging key transistors, a resonant capacitor, a resonant inductor, a transformer with charging and discharging primary and secondary windings, a rectifier unit and a control device, characterized in that the charging transistor, charging primary the transformer winding, capacitor and inductor are connected in series, connected to the terminals of the power source and form an oscillatory resonant charging circuit, the discharge transistor and the discharge primary winding of the transformer are also connected in series and connected to the terminals of the series-connected capacitor and inductor and form a discharge circuit, to the terminals of the secondary windings of the transformer a rectifier unit is connected, consisting of a set of forward and a set of reverse diodes and a smoothing filter, the control device consists of the number of channels corresponding to the number of transistors and provides control pulses to the base of the transistors of the charging and discharge circuits alternately, during each half-cycle of their on state, between charging and bit control pulses and half-periods of natural oscillations of the resonant circuit provide time intervals, control pulses are supplied with time intervals between them, the output voltage of the converter is regulated by changing the time intervals, the minimum duration of the specified time intervals and intervals is ensured not less than the time of carrier resorption in the base junction of the transistor . 2. The converter according to claim 1, characterized in that it contains (k-1) power stages identical to the first stage (k=1, 2, 3, ... - the total number of stages), which together with the first stage form a multiphase converter with the number of phases m=2k (2, 4, 6, ...), the control device contains m channels that output control pulses to the bases of transistors of all stages, and these pulses are phase-shifted relative to each other by an angle equal to 360°/m . 3. Converter according to claims. 1, 2, characterized in that the rectifier unit consists of a set of freewheeling diodes and a smoothing filter. 4. Converter according to claims. 1-3, characterized in that the charging and discharging primary windings of the transformer have a different number of turns.