SU744876A1 - Two-cycle self-exciting inverter - Google Patents

Description

one

The invention relates to the field of converter technology and can be used in secondary power supply and automation systems to convert DC voltage to AC using transistor inverters.

- Known push-pull self-excited synchronized inverters containing two transistors, an output transformer with positive feedback and coils of winding in synchronization circuit 1 are known. The disadvantage of such inverters is the need to supply half a period to the input of the keys, which also complicates the synchronization circuits .

Also known as a prototype is a self-excited inverter that contains power transistors and an output transformer, the winding of which is connected between the bases of transistors via a saturation throttle and a bi-directional switch made on a full-wave rectifier and Transistor 2.

When sync pulses appear at the input of a bidirectional switch, a U.Kanned chain of windings, throttles, and a key generates a pulse of base current that converts the transistors of the converter to the opposite state. Due to the inductive nature of the resistance of this chain, the base current clock pulses have a gentle front and limited amplitude, as a result of which the switching process

The id transistors are slowed down, dynamic losses increase, synchronization stability decreases, especially when the converter operates on variable load and capacitive load.

The aim of the invention is to increase the clarity of synchronization and increase efficiency by reducing dynamic losses.

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This goal is achieved by the fact that in a two-stroke self-exciting inverter containing transistors, a bidirectional switch and a transformer with a positive reverse signal

25 connection, the indicated winding is connected through the base resistor between the bases of the transistors, the counter-parallel to the input of which the diodes are connected, and the specified switch through the capacitor

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connected between the bases of the transistors, with the point of connection of the key to the capacitor connected to the point of connection of the winding with the base resistor through a charging resistor.

The scheme of the proposed device shown in the drawing.

The inverter is made of transistor 1, 2, connected to the output transformer 3 according to the self-excitation scheme through the primary winding 4 and the positive feedback winding 5. The winding 5 is connected between the bases of the transistors 1, 2 through the base resistor b, which is bounded by the charging resistor 7 and capacitor 8. Cheating point of resistor 7 and capacitor: 8 is connected to the base of transistor 2 via a bi-directional switch 9. Power is fed to the inverter through a current-limiting choke Y. The input circuits of the transistors are shunted by i: 11 and 12.

The device works as follows.

After start-up, the inverter is driven as an ordinary auto-oscillator. At the same time, the capacitor 8 is charged from the winding 5 through a resistor 7 and the input transistors. In the drawing; “all the polarities of the voltages and currents are indicated for the half period when transistor 1 is open and transistor 2 is closed. After the clock pulse arrives at the input of the switch 9, the capacitor 8 is discharged through the switch 9 and the input circuits of the transistors. In this case, the direction of the current in the base circuits is reversed and the transistors are switched to the opposite state (the direction of the discharge current Iposp is indicated in the drawing).

The amplitude of the base current pulse is determined mainly by the initial voltage of the capacitor 8 and the internal resistance of the key 9. To increase the initial voltage of the capacitor in series with the charging resistor 7, the additional winding 13 of the transformer is turned on (shown in dotted lines in the drawing to limit the amplitude of the base current a given level in series with the capacitor 8 and the key 9 should include an additional resistor 14 (shown in dotted lines in the drawing).

In the next half-period, the polarity of the voltages on the transformer windings and the capacitor 8 is reversed, as a result of which at the next sync pulse the discharge current Ifaip. will change the direction and switch the transistors 1.2 volts; the previous state. The choke 10 in the power target serves to limit the current squaw due to the overlap of transistors. In this device, the overlap interval can be reduced to a minimum by increasing the amplitude of the base current pulses to the maximum level allowed by the transistors. This allows the induk to be reduced. The effectiveness and size of the current-limiting droplet, and in some cases, exclude it from the circuit altogether.

The proposed circuit solution of the synchronization circuit can also be used in the bridge version of the inverter.

In the described device, the discharge circuit 8.9 has a low ohmic resistance and does not contain inductive elements. Therefore, the switching pulses of the base current have a steep leading edge, and their amplitude can repeatedly (depending on the circuit parameters) exceed the circulating current 5. Such force of the base current in the switching interval of the transistors accelerates the absorption of the base charge and creates a deep saturation of the newly opening transistor .

The listed properties of the object 5 provide an increase in the synchronization stability and a decrease in the dynamic energy losses in the transistors. Reducing the absorption time of the base charge also allows the frequency range of

converters,

Claims (3)

Invention Formula 1, Push-pull, self-exciting inverter with external pulse synchronization, containing transistors. bidirectional switch and transformer with positive feedback winding. characterized in that, in order to increase the efficiency and synchronization definition, the indicated winding through the base resistor is connected between the bases of the transistors, whose diodes are connected in parallel to the input, and the indicated key through a capacitor connected between the bases of transistors, with the point of connection between the key and the capacitor connected to the point of connection of the base-. with a winding through - charge resistor. 2. The inverter according to claim 1, characterized in that an additional volume of the output transformer is connected in series in the charging resistor circuit. 3. The inverter according to claim 1, characterized in that an additional resistor is sequentially included in the key circuit, Information sources, taken into account in the examination 1. USSR author's certificate number 163264, cl. H 02 M 7/537, 1962. 2. USSR author's certificate number 164057, cl. H 02 M 7/537, 1963.