SU813635A1 - Voltage converter - Google Patents

Description

(54) VOLTAGE CONVERTER

one

The invention relates to electrical engineering 5, in particular to static voltage converters, and can be used in the development of power sources for radio electronic devices, inductive sensors and other electrical energy consumers.

Voltage converters are known which have two transistors, a transformer with positive feedback windings and are being set: an RC circuit. Transistors are alternately connected to a constant voltage source of a transformer half winding. The duration of the open state of each transistor is indicated by the parameters of the RC circuit 1 and 2.

The disadvantages of these converters are that, firstly, the load current of the voltage converter has a significant effect on changing the frequency of the output voltage, which limits its application to its intended purpose, secondly, in the absence of load, the switching of transistors occurs due to saturation transformer, and this leads to distortion of the output voltage and the switching of the transistors in the energetic mode due to a significant increase in the current Matora at the time of closing of the next transistor. In one of the known devices these disadvantages are eliminated, however, the converter

The voltage is complex, and because of the existing variation in the parameters of the diodes, asymmetry may occur in the half-switching periods of the transistors. Asymmetry manifests

5 in the additional current load of one of the voltage transistors.

Closest to the proposed is a voltage converter

0 containing two power transistors, the collectors of which are connected to the corresponding primary windings of the output transformer and to one of the ends of the time of the close resistors,

5, the other ends of which are connected with a timeless capacitor, transistors and positive current feedback,

However, this converter has a low load capacity. This is due to the fact that in the device the magnitude of the load current is determined by the value of three parameters: the nominal voltage of the power source, the magnitude of the resistance of the drive resistors and the gain of the transistors. Transistors have a defined final gain value. For a given nominal voltage of the power source, the realization of the required load capacity of the voltage converter is achieved by appropriately choosing the value of the time of the driving resistors where Uj is the voltage of the power source; load current (the magnetizing current of the transformer is not taken into account due to its smallness); gain transistors. The amount of power dissipated at the time of the setting resistors, and, therefore, their weight and dimensions are determined by the values of the supply voltage and load current:) nD 2 and „„ itz. If R-iB 2 where is the current in the base of the transistor Therefore the maximum the load of the voltage converter, in the first, is limited by the size of the time of the setting resistors. In the known device, when the supply voltage is 10–5 V, the negative influence of a branch of a portion of the capacitor recharge current from the base circuit of the open transistor to its collector circuit through the time that the open transistor drops is noticeable. The voltage in the collector-emitter circuit is less than in the base-emitter circuit. The lower the voltage of the power source, the greater the portion of the branch current from the base circuit. This leads to a decrease in the base current, and therefore, the load of the transducer. The purpose of the invention is to increase the load capacity of the voltage converter. This goal is achieved by the fact that in a voltage converter, the time of the capacitor is connected with the other ends of the time of the closest resistors and with one of the ends of the above-mentioned feedback windings, the other ends of which are connected to the bases of the transistors directly. FIG. 1 shows a voltage converter circuit; in fig. 2 time diagrams of voltages and currents on the main elements of the device in the course of its operation. The circuit (Fig. 1) contains the windings 2 and 3 of the positive feedback of the transformer 1, the time setting resistors 4 and 5 / transistors 6 and 7, the time of charging the capacitor 8, the source 9 of constant voltage, the circuit 10 of the main load of the device. The diagrams (fig. 2) designate the voltage across the switching capacitor, the voltage at the collector-emitter junction of transistor b (7), the voltage at the base-emitter junction of transistor b (7),) g is the current in the base circuit of transistor b ( 7). The semi-windings of transformer 1 are periodically connected to the source 9 of the constant voltage by transistors 6 and 7. The base circuits of the transistors include windings 2 and 3 of the positive feedback of transformer 1. Condenser 8 is connected in series with windings 2 and 3, its plates are additionally connected through time, the setting resistors 4 and 5 to the collectors of transistors 6 and 7. When the supply voltage is applied to the voltage converter, the transistors 6 and 7 begin to open across the base circuit with current flowing through the resistors 4 and 5 from the source Nickname 9 DC 9. Due to the existing variation in the frequency characteristics of the transistors, one of the transistors, for example 6, opens more quickly, which in the presence of windings 2 and 3 of the positive feedback leads to the regenerative process of opening the transistor 6 and closing the transistor 7. From this point on time begins charging the capacitor 8 through the circuit: a source of constant voltage 9, a transformer 1, a resistor 5, a capacitor 8, a winding 2 and the base-emitter junction of the transistor 6. The charging current of the capacitor 8 pi the emitter base of the transistor 6, the latter, in addition, a current from the winding 2 of the positive feedback flows through the base of the transistor, limited by the resistance of the resistor 4. When charging the capacitor 8 to a voltage equal to the sum of the voltages to the windings 2 and 3 positive feedback, the current flowing through the resistor 5 is switched from the base circuit of transistor 6 to the base circuit of transistor 7. Transistor 7 opens, and transistor 6 closes. Due to the positive feedback windings, the switching process of the transistors is regenerative. Upon completion of the switching process of the transistors, the polarity of the voltages on the transformer windings is reversed and the capacitor begins to recharge across the circuit: a source of constant voltage 9, a semi-winding of the transformer 1, a resistor 4, a capacitor 8, a winding 3 and the base-emitter junction of transistor 7 .

After a time equal to the half-period of the output voltage frequency, the voltage on the capacitor 8 again reaches a value equal to the sum of the voltages on the windings 2 and 3, as a result of which the switching process of the transistors begins again. Transistor 7 closes and transistor b opens. In this state cxehtti, the next recharging of the capacitor occurs during the second half-cycle of the frequency of the output voltage. The process then repeats in the sequence described.

In the voltage converter, by changing the circuit interconnections, not only is there no current branch from the transistor base circuit for any value of the power supply voltage occurring in the known device, but rather the sum of currents through the open transistor base circuit: capacitor overcharge current and current , created by the winding of the transformer in a closed circuit: the base-collector transition of the open transistor, the time of the resistor and the winding of the transformer. In connection with G, the value of the base current of the open transistor in the proposed device is greater than in the known, and therefore, its load capacity. At the expense of this, it is possible to increase the resistance value of the time setting the resistor and, thus, reduce the dissipation of them, and consequently, reduce the weight and dimensions of the device

Such a voltage converter, a number of positive qualities, such as increased load capacity, frequency stability, facilitated switching mode of the transistor due to the absence of transformer saturation, high reliability (the device is operational even when one of the transistors goes off) the development of high-frequency alternating voltage sources or DC / DC converters.

The device provides the greatest effect in the development of low-power low-voltage power sources.

Claims (3)

1.Lovushkin V.N. DC Power Transistors. Energy, 1967, p. nineteen. 2.Lovushkin V.N. DC Power Transistors. Energy, 1967, p. 20. five 3. Authors certificate of the USSR 479243, cl. H 03 K 13/02, 1975. t at and - f