SU970610A1 - Two-cycle voltage converter - Google Patents

Description

(B) TWO-TACT VOLTAGE CONVERTER

The device is electrical and can be used as a secondary power source.

Two-stroke voltage converters are known, which are triggered by applying a starting current pulse from the primary power source through a capacitor directly to the base of one of the transistors of the converter 1 or to the special starting winding of the saturating transformer 2.

The lack of these devices is unstable starting, especially in a wide range of variations in ambient temperature and primary supply voltage, as well as with significant technological variations in the parameters of the converter elements and with a smooth supply of primary supply voltage. This is explained by the fact that the amplitude and duration of the starting current pulses are determined mainly by the parameters of the trigger circuit elements, and the converter's output time for stable self-oscillations, both by the parameters of the converter elements and output circuit filters, and by the capacitor capacitance in the starting circuit. Stable triggering of the converter is possible only if the amplitude and duration of the starting current pulse do not noticeably decrease before the converter reaches the steady-state self-oscillation mode.

Two-stroke voltage converters are known in which an additional converter of higher-frequency single-pole pulses 3 is used for starting.

The disadvantages of such devices are unreliable start of the main

15 of the converter, due to the fact that during the start-up the additional converter periodically reduces the starting base current of the transistors of the main oscillator of the core to zero, while as the voltage of the primary power increases, the collector current of the resistors of the main autogenerator increases and for its reliable start

25 increase in the base current of the transistors, as well as a long time for the output of stable oscillations of the main oscillator, which is caused by the discharge of all filter capacitors during

30 time of periodic decreases by the additional converter of the starting base current. Transistors-main converter.

Closest to the proposed by the technical essence is a push-pull voltage self-oscillator, which contains a transformer with switching transistors, a starting transistor-resistor node having a control input, a rectifier whose input is connected to one of the transformer windings, a resistor and a capacitor 4 3.

A disadvantage of the known device is a poor start. This is due to the fact that the capacitor, which is necessarily needed in the locking unit, starts charging from the locking source (from the rectifier connected to one of the transformer spacings) from the very start of the autogenerator and locks the starting node until the autogenerator reaches the stable self-oscillations (regardless of the capacitance of this capacitor, which only affects the time of the oscillator output on the self-oscillation mode). At the same time, the starting current from the primary source is reduced power is supplied through the starting node to the bases of the transistors of the autogenerator, although their collector currents increase as the voltage of the primary supply increases, which leads to oscillations of the aytogenerator. Increasing the base current of the transistors during start-up by increasing the voltage on the windings of the positive feedback or decreasing the resistance of the base circuit leads to an increase in losses in the base circuits of the oscillator in the stable self-oscillation mode, but does not guarantee a reliable start under all operating conditions.

The purpose of the invention is to improve the stability of the launch of the auto-generator in a wide range of changing working conditions. I

The goal is achieved by the fact that in a push-pull voltage converter containing an inverter cell in power transistors, some of the power electrodes of which are combined and connected to the first input terminal, and others are connected to the output transformer having an additional 1/1 winding through a rectifier and capacitive the filter associated with the emitter-base transition of the starting transistor, the base and the collector of which through the corresponding resistors are connected to the second input terminal, and the emitter is connected with the winding atomic connection, parallel to the emitter-base transition of the starting transistor

connected to the power circuit of the input of the locking transistor / emitter of which is connected to the middle point. the feedback coil, and the control emitter-base transition, is shunted;

connected by a zener diode connected to a capacitive filter.

The drawing shows the scheme of the device.

0 The converter contains a transformer 1 with a primary winding 2, a winding 3 with a positive feedback and a winding 4 locking, the switching transistors 5 and. 6, resistors 7-9 in the base circuits, starting node 10, consisting of transistors 11 and 12 and resistors 13-15, rectifier .16, whose input is connected to the winding 4 of transformer 1,

Q and capacitor 17, which is connected via resistor 18 to the output of rectifiers 16 and through zener diode 19 to the control input of the starting node 10.

The device works as follows.

5 way.

 When applied to the input of the power supply device Un (smoothly or abruptly) through the resistor 13, the transition of the base-emitter of the transistor 11 and the resistor 8

0 current will flow. At the same time, the transistor 11 opens and a current flows through the collector-emitter junction and resistors 14 and 8. As the supply voltage U increases, this current increases. This increases the voltage drop across the resistor 8, which through the winding 3 and the resistors 7 and 9 is applied to the base-emitter junctions of the transistors 5 and b. When the scientific research institute has reached this voltage

level one of the transistors 5, 6 on. begins to open (one that has less resistance to the base emitter junction). Let it be a transistor 5. Through the junction of the collector-eg1ter of transistor 11, the resistor 14, half of the winding 3, the resistor 7 and the junction-emitter junction of the transistor 5 the starting current flows. Transistor 5 opens even more. This causes a rise in magnitude of the collector current of the transistor 5 from the primary power source and through the half of the primary winding 2 of the transformer I. An increasing value of voltage begins to appear on all the windings of the transformer I. The current from the positive feedback winding 3, together with the current of the starting node 10, opens the transistor 5 even more until it becomes saturated. At the same time, its increasing collector current causes saturation of the magnet, the lead of the transformer I, which leads to a change in polarity on all its windings. As a result, the voltage of the winding 3 begins to close the transistor 5 and opens the transistor 6. At the same time, currents from the upholstery 3 and from the primary power source Up through the starting node 10 and the resistor 9 simultaneously flow through the base-emitter transistor, which accelerates the process opening the transistor 6 and closing the transistor 5. To limit the through current through the base-emitter junctions of the transistors 5 and 6 arising from the absorption of minority carriers in the base of the closing transistor, and to reduce the reverse aprons at the base-emitter junction of a closed transistor the resistance of the base circuit is divided into three parts of the same magnitude (resistors 7, 8, and 9). Further, the switching process of the transistors 5 and 6 of the converter is periodically repeated.

In contrast to all known devices, in the proposed auto-oscillator, the starting current (through the starting node 10 and alternately the basic circuit. The switching-transistors 5 and b) of the cathode flow through the entire starting process almost until the final output of the auto-generator to the steady auto-oscillation mode. Moreover, as the voltage of the primary supply increases, and consequently, the collector current of the transistors 5 and converter B, the starting current in the device does not decrease, but increases. This ensures reliable start of the converter regardless of the speed and rise time of the primary supply voltage, changes in the wide ambient temperature, and the nature of the load.

The trigger node 10 is shut down over time. 3 of the proposed device, the disconnection of the starting node 10 does not occur until the end of the starting process, but only when the self-oscillator comes out (or almost comes out) into the regime of stable self-oscillations. Only then the voltage Uj will be sufficient (Uj is the voltage rectified by rectifiers 16 with windings 4 of the transformer 1) to break the Siltron 19. The Zener diode 19 penetrates like an avalanche and the current flowing through it opens the transistor 12 it is closed due to the connection of its base with the emitter through a resistor 15 and did not affect the launch at all. Transistor 12 its transition

the collector-emitter shunts the base-emitter junction of the transistor 11. and closes it. At the same time, the voltage at the base-emitter junction of the transistor 11 decreases, which is quite enough for its reliable closing.

Resistor 18 serves to limit the current through Zener diode 19. Unlike the known circuits, capacitor 17. does not affect the start-up process of the auto-oscillator at all and only serves to filter the voltage rectified by the rectifier 16 for only a short time (about 0 , 1 2 µs) switching of the auto generator,

which prevents the start-up of the start-up unit 10 during the operation of the oscillator in the steady self-oscillation mode.

20

Claims (4)

1. US patent 3411108, cl. 331-113, 1967. 2. US patent number 3516020, class. 331-113, 1970. 3. USSR author's certificate No. 452900, cl. H 02 M 1/08, 1975. 4. G. Veresova and Smur Kova, I.L., Stabilized sources of power for electronic equipment. M. Energie, 1978, p. 143-145, rice 614. Y