UA79964C2 - Method of regulated conversion of direct voltage - Google Patents

Abstract

This invention relates to electrical engineering, in particular to a regulated transistor resonant high-frequency voltage converter with excellent efficiency, high power and low in cost, which can be used in different fields, with direct and alternating high-frequency voltage output. The regulated resonant voltage converter comprises two circuits for the simultaneous flowing of direct and indirectcurrents of the half-bridge transistors. A method of the resonance conversion is carried out at the expense of use of the second resonant choke that consumes power from the resonant capacitor and transmits a part of power to the rectifying load. Due to the above during all modes of operation the transistors provide for commutation at zero currents and the current amplitude does not exceed the nominal value at the expense of power interchange thatparticularly excludes the dynamic overloads and losses.

Description

Description of the invention

The invention relates to electrical engineering and is intended for the implementation of powerful, cheap and effective 2 adjustable transistor high-frequency resonant voltage converters for various applications, in particular - cathodic protection stations operating at elevated temperatures and natural cooling, welding converters, induction heating installations, radio transmitting devices.

There is a known method |(| Romash Z.M., Drabovich Yu.Y., Yurchenko N.N., Shevchenko P.N. High-frequency transistor converters, - M; Radio and communication, 1988, 288 p.| regulated resonant conversion of 70 constant voltage, which consists in: - creating oscillations with its own period To and the switching period of the keys T, using a capacitive and inductive energy store that is powered by a source of constant voltage and transfers part of the energy to the rectifier load, - adjusting the load voltage due to arrangement from resonance ( period of natural oscillations T o) period Tu, close to To.

The disadvantages of the above-mentioned method include the fact that the arrangement leads to a significant increase in losses and a decrease in reliability due to the loss of the main advantage of resonant converters - switching at zero currents. Therefore, this method is used only in low-power converters.

The closest to the proposed invention is the method (PCT UuUOSZ4A/14230, 23.06.94. НО2М3/3351) of adjustable resonant conversion of constant voltage, which consists in: - creating oscillations with its own period To and the switching period of keys Tu (T2To) using capacitive and inductive stored energy with power from a source of constant voltage and transfer of part of the energy to the rectifier load, - return of the excess energy of the capacitive storage back to the voltage source, c - regulation of the load voltage due to changes in Tk, Ge) - limiting the front of the current pulses of key elements with the help of additional inductive storage devices

This method preserves the main advantage of resonant converters - zero-current switching. A feature of the method is that the regulation effect (change in load voltage or current) is associated with the return of energy to the power source due to the discharge of the capacitive storage device to the power source Ge) through the load.

The main disadvantage of the above method is unacceptable overloads (increased key currents) in case of overloads or short circuits in the load circuit at the nominal or maximum Ф frequency. In this case, a large amount of energy accumulates in inductive storage devices, which does not have time to return to the power source in a short period of time (T - To)/2. This is due to the fact that there is a forced interruption of the current through the keys, although with a set edge. Thus, in this method, it is necessary to take measures to protect the keys, which complicates it, narrows the range of adjustment and limits the scope of application. "

The device that implements this method of conversion is a classic half-bridge serial C 50 resonant converter with a capacitive voltage divider (capacitive storage), an inductive storage with a load included between the half-bridge transistor rack and the middle output of the capacitive divider.

From" Additional inductive accumulators are included in the branches or circuits of each transistor.

The task of the proposed invention is to provide a large range of regulation and to expand the field of application.

The task is achieved by creating a method of adjustable resonant transformation of constant 7 voltage, which consists in: (se) - creating oscillations with its own period To and commutation period TU (Tu To) using capacitive and inductive energy storage with power from a source of constant voltage and transmission of part energy to the rectifier load, b 20 - return of the excess energy of the capacitive storage back to the voltage source, - regulation of the load voltage due to the change in T,,

T" - created simultaneously with these or the first oscillations of the second oscillations with their own period To and commutation period Tu using the same capacitive storage and the second inductive storage with power from the capacitive storage and transferring part of the energy to the rectifier load. 29 A feature of the proposed method is the simultaneous flow of key currents (without interruption), which allows

HF) to return the accumulated energy of inductive storage devices at maximum frequency even with a short circuit. At the same time, the amplitude of the currents of the keys remains at the level of the nominal value. Thus, the method allows to work in the entire range of frequency and loads, which solves the problem of the invention.

The invention is explained by the drawings in figures 1-14, which show: 60 - Fig. 1 - scheme of the proposed device; - Fig. 2 - graphs of currents and voltages; - Fig. 3 - fragments of the equivalent circuit of the device, explaining the processes in the time interval 4-6; - Fig. 4 - fragments of the equivalent circuit of the device, explaining the processes in the time interval i5-b; - Fig. 5 - elements of the equivalent circuit of the device, explaining the processes in the time interval i3-i/; bo - Fig. 6 - fragments of the equivalent circuit of the device, which explain the processes in the time interval and -i5;

- Fig. 7 - fragments of the equivalent circuit of the device, explaining the processes in the time interval (5-6; - Fig. 8 - fragments of the equivalent circuit of the device, explaining the processes in the time interval i8; - Fig. 9 - fragments of the equivalent circuit of the device explaining the processes in the time interval y.-(d; - Fig. 10 - fragments of the equivalent circuit of the device explaining the processes in the time interval iv-(9; - Fig. 11 - fragments of the equivalent circuit of the device explaining the processes in the interval of time (5-ЦЧ0о; - Fig. 12 - fragments of the equivalent circuit of the device explaining the processes in the time interval (0-4; - Fig. 13 - fragments of the equivalent circuit of the device explaining the processes in the time interval (4-(Ц ТК) ; - Fig. 14 - a family of control characteristics. 70 The device that implements the proposed method contains a controlled generator that sets pulses 1, the outputs of which are connected to the gates of transistors 2 and 3, which form a half-bridge rack. The emitter of transistor 2 is output 1 of this rack, and the collector of transistor Z is the output of rack 2. An typeparallel diode 4 is connected to the collector and emitter of transistor 3. The common point of transistors 2 and Z is the collector of transistor 2 and the emitter of transistor Z (the middle terminal of the rack) through a capacitive storage (resonant capacitor) 5 is connected to 7/5 of one of the terminals of the transformer rectifier load 6. Inductive accumulators (resonant chokes) 7, 8 are connected in series, while their common point is connected to another terminal of the load 6. Power supply 9 is connected to the lower terminal of the choke 7 and the emitter of the transistor 2. The upper terminal of the choke 8 connected to the collector of transistor 3. Anti-parallel diode 10 is connected to transistor 2.

The method of resonance transformation is carried out as follows. The pulse generator 1 generates control pulses (Fig. 2a, b) with a duration of T 0/2 and an adjustable switching period Tu, which alternately open transistors 2, 3. In the steady state, at the moment of time u/, a control pulse is applied to the lower at the same time, transistor 2 begins to flow a sinusoidal pulse of current I (Fig. 2c) through this transistor (first oscillations).

Also, the current Io continues to flow through the anti-parallel diode 4 of the upper transistor Z (second oscillations).

Time interval Ts-5 is the first characteristic cycle of work. The corresponding fragment of the equivalent circuit is shown in Fig. 3. Resonant capacitor 5 (with a voltage Shv, see Fig. 2d) is recharged through the transformer-rectifier load 6, which includes a transformer 6.1, a rectifier 6.2 and actually i) a load 6.3 and the first resonant choke 7, which accumulates energy. At the same time, the resonant capacitor 5 is discharged through the second resonant choke 8 (with a voltage in, see Fig. 2e), which accumulates energy according to the indicated polarity. "h zo The y-yz time interval is the second characteristic cycle of work. The corresponding fragment of the equivalent circuit is shown in Fig.4. The resonant capacitor 5 continues to be recharged through the transformer-rectifier x, the load b and the first resonant choke 7. The resonant capacitor 5 is discharged through the second resonant choke 8, which already gives off energy according to the indicated polarity.

The time interval Sh3-id4 is the third characteristic cycle of work. The corresponding fragment of the equivalent circuit me) c5 is shown in Fig. 5. The resonant capacitor 5 continues to be charged through the transformer-rectifier load b and the first resonant choke 7 (with voltage Ш 7, see Fig. 2e). At the same time, the resonant capacitor 5 is already charged from the second resonant choke 8, which continues to give off energy according to the indicated polarity.

The time interval (/-5) constitutes the fourth characteristic cycle of operation. The corresponding fragment of the equivalent circuit is shown in Fig. At the same time, the resonant capacitor 5 continues to be charged from the second resonant choke 8. The time interval (5) is the fifth characteristic cycle of operation. The corresponding fragment of the equivalent circuit is shown in Fig. 7. The resonant capacitor 5 is charged through the transformer-rectifier load 8 and the first resonant choke 7. - And the time interval 0-1 is the sixth characteristic cycle of operation. The corresponding fragment of the equivalent circuit is shown in Fig. 83. The resonant capacitor 5 already gives energy through the transformer-rectifier IC of the load b and the first resonant choke 7 to the power source 9. At the same time, its current changes its direction.

The time interval Y-y3 is the seventh characteristic cycle of work. The corresponding fragment of the equivalent circuit

Me, shown in Fig.9. The control pulse is applied to the upper transistor 3. At the same time, a sinusoidal pulse of current I" (Fig. 2.c) begins to flow through this transistor (second oscillations). Current I also continues to flow through the anti-parallel diode 10 of the lower transistor 2 (first oscillations). The resonant capacitor 5 gives energy through the transformer-rectifier load 6 and the first resonant choke 7 to the source of the power supply 9 and to the second resonant choke 8.

The i-th time interval is the eighth characteristic cycle of work. The corresponding fragment of the equivalent circuit

F) is shown in Fig. 10. The resonant capacitor 5 and the first resonant choke 7 give energy through the transformer-rectifier load b to the power source 9, and the resonant capacitor 5 also gives energy to the second resonant choke 8. The time interval (5) is the ninth characteristic cycle of operation. The corresponding fragment of the equivalent circuit is shown in Fig. 11. All storage devices provide energy.

The time interval Ts0-ts4 is the tenth characteristic cycle of operation. The corresponding fragment of the equivalent circuit is shown in Fig. 12. The resonance capacitor 5 is recharged due to the energy of the second resonance choke 8. 65 The time interval (4-4 is the final cycle of operation. The corresponding fragment of the equivalent circuit is shown in Fig. 13. The resonance capacitor 5 is discharged. Then the processes are repeated.

Thus, at the time interval (-th), energy is returned to the power source (change in the direction of the current 11). At the same time, the negative amplitude of the current I- is determined by the value of the load, and when decreasing

Tk, when Her; approaching is, energy return takes place.

This determines the additional advantages of the method - the positive amplitude of the current does not increase until the load is short-circuited. There is also no problem of through currents, which simplifies and makes reliable control of transistors.

An example of a specific implementation of the invention. A voltage converter for a cathodic protection station with a power of 1.v6kW, powered by the "2208" network, IKORSZOSHYUO transistors, resonance capacitor 5 with a capacity of 0.15μF, /o resonance chokes 7.8 by 25μH, period of natural oscillations To-12μs, transformation coefficient of the transformer 6, 1 is equal to 1/2, which determines the range of the nominal load of the order of 0.8-20m. For the minimum value of the commutation period T-1Zmks ((-77kHz) and a load of 1Ω, the amplitudes of the current I are equal to 29A and -TA, respectively. For a load of O0.5Ω, the amplitudes of the current I 4 are equal to 29A and -14A, respectively. In the case of a short circuit: 29A and - 21A.

Fig. 14 shows a family of control characteristics that confirm the invention.

Claims (1)

The formula of the invention is the method of regulated resonant conversion of constant voltage, which consists in creating oscillations with a natural period To and a commutation period Tk (Tk»To) using capacitive and inductive energy storage devices with energy consumption from a source of constant voltage and transfer of part of the energy to the rectifier load, return the excess energy of the capacitive storage back to the voltage source, the regulation of the load voltage due to the change in Tk, which differs in that, simultaneously with these or with the first oscillations, the second oscillations with their own period T o and the commutation period Tk are created using the same capacitive storage and of the second inductive storage with energy consumption from the capacitive (o) storage and transfer of part of the energy to the rectifier load. « (Se) (o) (o) and - - and? -i se) se) (o) s» ime) 60 b5