RU1829094C - Single-cycle d c/d c converter - Google Patents

Abstract

Usage: DC voltage conversion in secondary power systems and automation. Summary of the invention: transistor 2 is opened by a charge pulse of capacitor 8 when a positive voltage appears on the positive feedback winding 7 of output transformer 3. Transistor 2 remains open for the absorption of excess carriers in its base, which is determined by the current in the auxiliary winding circuit 9 output transformer 3. The closed time of the transistor 2 exceeds the time of its open state, thereby reducing the voltage at the closed transistor. 2 ill.

Description

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The invention relates to electrical engineering and is intended for use in secondary power sources of electronic equipment.

The purpose of this technical solution is to increase reliability by reducing the relative duration of the open state of the transistor.

In FIG. 1 shows a diagram of a device; figure 2 - diagrams of voltages and currents.

The device consists of a primary power source, to which a transistor 2 and an output transformer 3 are connected, the primary winding of which 4 is connected in series to the power source 1, the secondary winding 5 is connected to a load 6, the positive feedback winding (base) 7 is connected to the common terminal point of the power source 1, and the other through the capacitor 8 to the base of the transistor 2, the additional winding with one output is connected to a common point of the power source 1, and the other to the diode 10 and the resistor 11 connected in series. the capacitor 8 is shunted by the resistor 12, the start-up RC circuit 13 is connected to the output of the power source 1 and the base of the transistor 2.

The device operates as follows.

When the primary power source 1 is turned on, the start pulse through the RC circuit 13 unlocks the transistor 2. Due to the positive connection, the base current of the transistor 2 starts flowing through the windings 4 and 7 of the transformer 3, and the latter enters the saturation. In this case, the main part of the base current flows through the capacitor 8. Since the additional base winding 9 is turned on according to the base winding 7, a negative voltage occurs at the cathode of the diode 10. Capacitor 8 starts charging in the circuit: winding 7, capacitor 8, resistor 11. diode 10, winding 9.

The current flowing into the base of transistor 2 decreases. At the time when transistor 2 goes out of saturation, a regenerative process of turning it off occurs.

Voltage across windings 7.9 change sign. In this case, the diode 10 prevents the unlocking of the transistor 2 by the voltage of the winding 9. The capacitor 8 is charged with the winding 7 in reverse polarity.

The parameters of resistors 11,12 and capacitor 8 are selected so that the recharge time ensures that the core of the transformer is not saturated and provides the required pulse duty cycle.

The stability of the switching frequency of the converter is determined by the stability of the input characteristic of the transistor 2, It turns out to be higher than in the prototype converter, because in the latter, stability is determined by the characteristics of two transistors.

A modification of the processes in the Converter using an additional base circuit 9 is shown in figure 2.

Protection of the converter against overcurrent and load short circuits, as in any converter with self-excitation, is provided by breaking the positive connection of the collector and base winding during overload. The presence of an RC starter circuit 13 eliminates the risk of the transistor 2 being unlocked after failure.

The converter has an increased

reliability and a simpler circuit, because contains only one transistor, and higher efficiency due to the exclusion of the resistive current sensor.

An additional advantage of the converter is the frequency stability and its independence from fluctuations in the voltage of the primary power source 1. As the voltage of the primary power source 1 increases, the voltage across the base winding 7 increases, i.e. the voltage applied to the capacitor 8. However, the voltage across the winding 9 also increases, which leads to a faster recharging thereof. Thus, the switching frequency is constant.

Claims (1)

SUMMARY OF THE INVENTION Single-phase DC / DC converter comprising an output a transformer whose primary winding is first connected to the first input terminal of the converter, and the end to the collector of the transistor, the emitter of which is connected to the second input terminal converter, and the positive feedback winding is connected through the capacitor to the base of the transistor and the end to the emitter of the transistor, characterized in that, in order to increase reliability by reducing the relative duration of the open state of the transistor, introduced the first and second resistors, a diode and an additional winding of the output transformer, the first the resistor is connected in parallel with the capacitor, an additional winding of the output transformer is connected to the base with an end. transistor through a series-connected second resistor and diode, and the beginning - with the emitter of the transistor. U ih 7l W l aj M I1 Without of pots zs about pot koi 9 Figure 1 tt fKi in M I1 J