SU1457114A1 - Single-end d.c. voltage converter - Google Patents

Abstract

The invention relates to the field of electrical engineering and can be used in secondary power supply sources. The goal is to increase reliability by simplifying the circuit. The device contains a key transistor 1, a current transformer 2, a measuring resistor 5, an additional transistor 6, a capacitor 7 and a diode 8. During operation of the voltage converter, by connecting the windings 4, 13 of the current transformer 2 through a diode 8 to the collector of the additional transistor 6, the reverse half-wave voltage is limited. This allows adjusting the amplitude of the reverse half-wave and the magnitude of demagnetization of the core of the current transformer 2 and the duration of the working half-period of the voltage converter. The control of the amplitude of the limitation of the reverse half-wave is made by a signal from the measuring resistor 5 connected in parallel with the base-smitter transition of the additional transistor 6. 3 Cp f-ly, 4 ill. with e (L - oo and i 7Z hall c. I

Description

The invention relates to the field of electrical engineering and can be used in the sources of secondary power supply of radio engineering, automation and computer systems.

The aim of the invention is to increase the reliability of a single-ended DC / DC converter by simplifying the circuit

FIG. 1 shows the electrical circuit of the proposed single-ended converter; in fig. 2 and 3 are embodiments of a current limiting circuit; in fig. 4 - oscillograms of voltages on circuit elements.

The single-ended DC-DC converter contains a key transistor 1, a current transformer 2 with a collector 3 and a base 4 winding, a measuring resistor 5 to which an additional trans input of the 6 is connected, the collector of which is connected to a capacitor 7 and a diode.

The secondary winding of the power transformer 9 through the diode 10 is connected to the output capacitor 11, and the base of the transistor 1 is connected to the generator 12 trigger pulses. The control winding 13 is connected in parallel to the capacitor 7, a series of diodes and a capacitor 14 can be connected in series with the base winding 4 of the current transformer 2 (figure 2).

The collector of the transistor 6 is connected to the capacitor 7 through the transistor 15 (FIG. 3).

The device works as follows.

The base of transistor 1 receives start-up pulses from generator 12. Each pulse opens transistor 1. Due to positive feedback through current transformer 2, transistor 1 blocks itself in the open state for a time determined by the saturation of the core of current transformer 2 current, after which the transistor 1 is closed and the transformer 2 is demagnetized, in a steady-state voltage, (FIG. 4). The voltage across the capacitor 7 when this is great.

As the load current increases, the voltage across the measuring resistor 5 increases, providing an open

0 5

0

Q

0

Transistor 6. When gsm capacitor 7 is discharged, and the voltage to which the capacitor is discharged depends on the load resistance. Now, at the stage of demagnetization of the current transformer, the demagnetization voltage decreases due to the opening of diode 8, what. allows current to flow through the discharged capacitor 7. As a result, the voltage-to-voltage integral of the reverse voltage (Fig. 4) on the winding 13 is small. The volt-second integral of the direct voltage should also be small, which follows from the property of a core transformer and a ferromagnetic material. This means that the duration of the direct pulse is reduced in proportion to the decrease in voltage on the capacitor 7, therefore, PWM modulation is provided, leading to stabilization of the current consumed.

The minimum reverse voltage of the winding 4 is equal to the voltage at the forward shifted transition of the diode 8, which limits the range of current stabilization with decreasing load resistance. The expansion of the range is achieved by connecting the diode 8 to the additional winding (Figures 2 and 3) with an increased number of turns, as well as the inclusion of a bias voltage in the base circuit, for example, using a circuit consisting of a resistor and a capacitor (Figure 2).

The combination of the base winding 4 of the current transformer 2 with the additional winding (Figures 2 and 3) allows to simplify the current transformer 2.

Connecting an additional transistor 15 of FIG. 3 allows an instantaneous response to a short circuit in the load circuit, providing a forced closing of the transistor 1, which is significant, for example, in converters with a direct switching on of the rectifier diode.

The use of the invention makes it possible to increase the reliability of power supply devices by simplifying the circuit, as well as to increase the speed of protection in the event of an overcurrent.

Claims (4)

1. Single-ended DC / DC converter containing 3 power transformer, the secondary winding of which is connected via a rectifier and filter with output terminals, and the primary winding is connected in series with the key transistor to the input terminals, a saturable current transformer, the collector winding of which is connected to the collector current circuit of the key transistor, the base circuit of which is connected to to the first output of the base winding of the current transformer and to the output of the trigger pulse generator, the control winding of the current transformer, distinguished by the fact that, in order to increase by simplifying the circuit, a measuring resistor, an additional transistor, a capacitor, and a diode are connected between the first output winding terminal of the current transformer and the collector circuit of the additional transistor, the base-emitter junction is connected in parallel with the measuring resistor, the first output of which is connected to the emitter key tran1 144 the second terminal to the second terminal of the base winding and the control winding of the current transformer, with the capacitor connected between the collector circuit and the emitter of the additional transistor. 2. The converter according to claim 1, characterized in that The base of the key transistor is connected to a parallel diode-capacitor bias circuit. 3. The converter according to claim 1, characterized in that the control winding of the current transformer is combined with the base winding. 4. The converter according to p. 3, t is characterized in that, in order to increase the response speed of the protection, a second additional transistor is introduced, the base-emitter junction of which is included in the collector circuit of the first additional transistor, and the collector of the second additional transistor is connected to the base circuit key transistor. at f Jl yy (/:  Jff / r FIG. g D.ph