SU892628A1 - Dc-to-ac converter - Google Patents

Description

I

The invention relates to converter equipment and is intended for use in power systems of various devices.

DC / AC converters with self-excitation are known, made according to a transformer circuit on two transistors with RC circuits SP and 12.

The disadvantages of these circuits are that they have low efficiency, as well as the possibility of the emergence of the through-current mode, which leads to the failure of transistors, as a result, to an insufficient reliability of the circuit and an increase in power losses in transistors.

The closest in technical essence is a DC / AC converter containing two transistors, the collectors of which are connected to the ends of the primary winding of the transformer, connected by a midpoint to a positive terminal for connecting a power source, and a negative terminal to the emitters of transistors, two RC circuits connected between the collector of one and the base of the other transistor Sz.

A disadvantage of this device is that its principle of operation, IE, makes it possible to avoid a through-current mode. So that the open T13 converter in this circuit could go to the closed

10, the state must first be opened by another transistor, and when it begins to open, the first (for the time of restoring the locking properties) is still in the open state. In re-

15 for some time, both transistors are in the open state. There is a through current mode in which the transistors can fail. In addition, when changing the load over a wide range in a known device, it is possible to change the frequency due to a smooth change in the base current of the open transistor as the capacitor of the RC chain charges.

The purpose of the invention is to stabilize the frequency when the load changes and to increase the reliability of the converter.

The goal is achieved by the fact that in the converter common points of RC circuits are connected via diodes to the midpoint of the transformer primary winding and through a resistor and diode to the collector of the other transistor, and the emitter-base junctions of the transistors are shunted by diodes.

The drawing shows a schematic diagram of the proposed device,

The DC converter contains two transistors 1 and 2, the collectors of which are connected to the ends of the primary winding of the transformer 3. -Two RC circuits, 5 and 6, 7 are connected between the collector of one and the base of the other transistors. Diodes 8 and 9 are connected between the common points of the RC circuits and the midpoint of the primary winding of the transformer. Diode resistor circuits 10-13 are connected between the common points of the RC circuits and with collectors of opposite transistors. Diodes and 1 shunt the base-emitter junction of transistors.

The device works as follows.

If traction resistor 1 is open and transistor 2 is in the closed state, then capacitor 5 is discharged across the circuit, resistor 11, diode 10, transistor 1, negative terminal for connecting the power supply, diode 15A and capacitor 7 are charged along the circuit positive terminal for connecting power supply, right half winding of the primary winding of the transformer 3, resistor 6, emitter-base junction of transistor 1, negative terminal for connecting the power source. Moreover, the EMF, induced in the right half winding, at this moment has a direction consistent with the direction of the EMF of the power source. Therefore, capacitor 7 tends to charge to double the value of the power supply voltage, but after charging only to the power supply voltage, it stops charging, since from this moment diode 9 opens and connects the capacitor 7 to the power supply. The disappearance of the base current of transistor 1 leads to its closing

and the appearance of the base current of the transistor 2 through the capacitor 5, the resistor k and the left half winding of the primary winding of the transformer 3. The transistor 2 opens and the circuit goes into a new stable state, after which the process repeats similarly.

The DC / AC converter is different from the known

the fact that it lacks the possibility of a through-current mode in the transistors. This is because the condition for opening the next transistor is to close the previous transistor. Therefore, the through-current mode is excluded, which leads to an increase in the reliability of the circuit and a decrease in power losses in transistors.

The device is characterized by a significantly lower frequency dependence on the load, i.e. greater frequency stability, and the moment the circuit goes from one steady state to another is determined by unlocking diodes 8 or 9, i.e. does not depend on the load.

The proposed DC-to-AC converter favorably differs from the well-known fact that when the load changes, the voltage at the output of the converter has a stable frequency, and also because it does not have a through-current mode in transistors, which leads to an increase in the reliability of the device and a decrease in power loss on transistors.

Claims (2)

Invention Formula A DC to AC converter containing two transistors, the collectors of which are connected to the ends of the transformer primary winding, connected by a midpoint to a positive terminal for connecting a power source, and a negative terminal to emitters of transistors, two RC circuits connected between a single collector and a base of another transistor, characterized in that, in order to stabilize the frequency when the load changes and increase the reliability of the converter, the common points of the RC circuits are connected via diodes to the common average the primary point of the transformer and 5892628 through a resistor and a diode with a collector1. US patent number 29b3b5b, another transistor, and emitter-ba-cl. 1976. the main transitions of the shunt transistors 2. Japanese Patent f 42-239 6, we are diodes. H03 K 4/52, 1971. Sources of information, S3.Patent of Poland No. 93280, taken into account during examination. Н02 М 7/537, 197В. 4. About f - O9 6 hH