SU1744775A1 - Single-ended voltage converter - Google Patents

Abstract

Use: sources of secondary power supply. The essence of the invention: the device contains a power transformer 1 with a primary winding, a transistor switch 7 and the primary winding 9 of the control transformer 8, the secondary winding 10 of which is connected in parallel to the control transition of the switch 7 and is bridged by a reverse diode 12. The secondary winding of the power transformer is connected through the rectifier and the output filter to the output pins. The feedback loop is formed by an output voltage deviation meter 15 and an amplifier 16 connected to its output, the output of which is connected to the bias winding 11 of the control transformer. Improving the noise immunity of the converter is achieved by adjusting the current in the bias winding, proportional to the deviation of the output voltage, and intended to change the magnetic properties of the control transformer core. The inductance of the magnetizing circuit of this transformer, depending on the bias current, determines the shape of the base current of the transistor switch and the duration of its saturated state. 2 h. the item of f-ly, 4 ill. with C

Description

The invention relates to converter equipment and can be used in power supplies.

A single-ended voltage converter is known, which contains a power transformer, a rectifier, a filter, a transistor switch with a proportional current control, and a feedback loop in the form of a collector -.ok limiting unit. The output voltage of the converter is stabilized by means of a feedback loop due to the pulse-width modulation (PWM) of the rectangular voltage on the windings of the power transformer.

The disadvantages of this device are low efficiency and unstable frequency conversion

Closest to the image is a single-ended voltage converter containing a power transformer, a rectifier filter transistor switch with proportional current control, and a feedback loop in the form of a measuring amplifier, a comparator, an integrating circuit, and two switching transistors. In this converter, the output voltage is stabilized by PWM, carried out using a comparator (comparing) pi

4X

4 vj

1 SP

lo-shaped voltage at the output of the integrating circuit with the output voltage of the converter.

However, the complex circuit design of the feedback channel causes a low reliability of the known device,

The purpose of the invention is to increase the reliability of the device by simplifying the circuit.

FIG. 1, 2 depict single-phase voltage converter circuits; in fig. 3 - time diagrams of processes in its chains; in fig. 4 is a diagram of a single-ended prototype converter.

The single-ended voltage converter (Fig. 1) includes a power transformer 1 with demagnetization winding 2, primary 3 and secondary 4 windings, degaussing diode 5, input filter 6, transistor switch 7, control transformer 8 with primary 9 and secondary 10 windings and winding 11 bias, additional diode 12, rectifier 13, output filter 14, measuring amplifier 15, amplification 16, and the control transformer 9 can be made on two cores 17 and 18 with half windings 19 and 20.

In the power transformer 1, the demagnetization winding is connected through the demagnetization diode 5 to the output terminals to which the secondary winding 4 is connected via the rectifier 13 and the output filter 14 The primary winding 3 of the power transformer 1 is connected to the input filter 6 through the series-connected transistor switch 7 and the primary winding 9 control transformer 8, the secondary winding 10 of which is connected by one of the leads to the base of the transistor switch 7 connected by its emitter with the anode of the additional diode 12. To the output of the The converter is connected to the input of the measuring amplifier 15, and its output is connected to the input of the amplifier 16, which is connected to the biasing winding of the control transformer 8, the secondary winding 10 of which is connected to the emitter of the transistor switch 7 by its second output diode 12 and is a clock input.

When the control transformer 8 is performed on two cores 17 and 18, one of the half windings 19 and 20 is located on each of them, which, in a series-opposite connection, winding 11 bias, and the primary

9 and the secondary 10 windings are common to both cores 17 and 18.

The Converter operates as follows.

A sequence of short trigger pulses is input to the converter sync input, which determines the conversion frequency. With this frequency, the transistor switch 7 connects the primary winding 3 of the power transformer 1 to the input filter 6 and converts the constant supply voltage into rectangular pulses that follow from the secondary winding 4 to the rectifier 13 and

5, after smoothing by the output filter 14, is converted to a constant voltage applied to the output terminals. This voltage is stabilized by the PWM of the rectangular voltage on the power transformer 1, i.e. by adjusting the time of the saturated state of the transistor switch 7 with a constant switching period

When a short starting pulse arrives (Fig. 3A), the process of turning on the transistor switch 7 starts and a collector current flows through the primary winding 9 of the control transformer 8 and the primary winding 3.

0 of a power transformer 1 (Fig. H) This current is transformed into a secondary winding 10, through which it flows into the base of a transistor switch 7, which is fully opened by an avalanche

5 of the base current rise process associated with the collector current (proportional current control). The collector current of the saturated transistor switch 7 is determined by the load and

0 its value can be considered constant, i.e. the current in the secondary winding 10, which is the sum of the base current of the transistor switch 7 and the magnetizing current of the control transformer 8, will be constant.

5 Due to the gradual increase of the magnetizing current, the base current decreases (Fig Zv), which after reverse through the zero value becomes reverse. As a result, the transistor switch

0 7 in goes from saturation (goes into active mode), the voltage on the windings of the control transformer 8, and with it the voltage on the base-emitter junction changes polarity and a key will be locked (Fig. 36). Immediately, the magnetization reversal of the cores of the power 1 and the control 8 transformers begins. The first of them gives the accumulated energy through the winding 2 demagnetization and diode 5

demagnetization of the load. The control transformer 8 is re-magnetized by the current flowing through the additional diode 12 from the secondary winding 10 (Fig. 3G).

The decay rate of the base current of the transistor switch 7 is determined by the inductance of the magnetizing circuit of the control transformer 8. For this reason, the time the key is saturated will depend on the inductance of the magnetizing circuit, with decreasing which the current decreases more sharply and the duration of the saturation interval decreases. The saturation state of the transistor switch 7 is controlled by means of a magnetising winding 11, through which a direct current flows, changing the magnetic permeability of the core and, as a result, the magnetizing circuit inductance of the control transformer 8. converter voltage. So, if this voltage increased, the voltage at the output of measuring amplifier 15 and the current at output of amplifier 16 will increase, the magnetizing core of control transformer 8 is stronger than the magnetic permeability of the core and inductance of the magnetizing circuit will decrease, the base current will decrease more sharply and the saturation interval The state of transistor switch 7 is reduced. The duration of the pulses on the windings of the power transformer 1 decreases and the output voltage of the converter decreases to the same level.

A control transformer 8, made on two cores 17, 18, makes it possible to similarly stabilize the output voltage by biasing both cores with the help of a half-wrap 19 and 20.

Thus, improving the reliability of the device is achieved by simplifying the circuit (eliminating the integrating circuit, comparator, and switching transistors), as well as improving noise immunity, since the device does not have a process for comparing the output voltage containing pulsations and noise with sawtooth voltage removed from the integrating chains. And with such a comparing, failures were possible in the process of switching a transistor switch, which reduced the reliability of the converter. Counter

switching on the half-windings in the biasing winding of the control transformer compensates for the variable components of the voltage on these half-windings and eliminates interference from the base circuit

Claims (2)

1. Single-phase voltage converter containing a power transformer with demagnetization winding connected to a demagnetization diode and with the primary winding connected to the input filter in series the connected transistor switch and the primary winding of the control transformer, the secondary winding of which is connected by one of the leads to the base of the transistor switch connected by its emitter to the anode of the additional diode, and the secondary winding of the power transformer is connected through a rectifier and output filter to the output terminals to which is connected The input of the measuring amplifier, characterized in that, in order to increase the reliability of the device by simplifying the circuit, the converter is equipped with an amplifier connected by its input m with the output of the measuring amplifier, and the output is with a biasing winding of the control transformer, the secondary winding of which is connected to another emitter of a transistor switch, the base of which, being a synchronization input, is connected to the cathode of an additional diode, to secondary winding of the same transformer. 2. Converter pop. 1, that is, with the fact that the control transformer contains two cores, each of which are arranged along one semi-winding, which are connected in series with a parallel connection by a bias winding, and the primary and secondary windings are common to both cores. -bo-pYh tie. and to transistor key FIG. 2 Ј ± L / k 0 ztfj A 0