SU1292148A1 - D.c.voltage converter - Google Patents

Abstract

The invention relates to converter equipment and can be used in the development of secondary power sources. The goal is to improve weight and size indicators. The device comprises a power amplifier, made on power transistors 1 and 2, controlled by a control unit using current feedback. The circuit implements a current overload protection mode using a protection node whose output is connected to the output of control unit 16, and the input is connected to the output of an overload current sensor whose input is connected to the middle point of control winding 10, which provides indirect information about overloads in the circuit. 1 il. with S cl

Description

The invention relates to a conversion technique and can be used in the development of secondary power sources.

The purpose of the invention is to improve the overall dimensions.

The drawing shows a schematic diagram of the converter.

The device contains power transistors 1, 2 and capacitors 3 and 4, forming a half-bridge power amplifier with a load 5 included in its diagonal. The power transistors are controlled by a common current transformer 6, the winding 7 of which is included in the output load circuit, windings 8 and 9 are connected to the control junctions of the power transistors, and the midpoint control winding 10 is connected to the first input power terminal through the control transistors 11 and 12, shu} 1tirovanny 11th diodes 13 and 14.

The middle point of the control winding of the current transformer is connected to the second input power terminal through a current limiting element 15, in particular, through a resistor. The transistors 11 and 12 are controlled by the control unit 16, the rectified voltage on the winding 10 of the current transformer, used as an input signal of the overload current sensor, which provides indirect current information through the power transistors, is fed to the input of the overcurrent sensor, the output of which is connected with node protect against overload with

Resistors 17 and 18, reference voltage source 19 and threshold element 20, made with a resetting delay, the output of which is connected to control inputs of control transistors and matching circuits (diodes 21, 22 and resistors 23 and 24) enter the composition of the node overload protection 25,

Similarly, a converter can be made using separate current transformers for each power transistor.

The inverter works as follows.

Let transistor 1 be in the conducting state, which corresponds to

the open state of the transistor 12, the load current flows through the transistor 1, the winding 7 of the current transformer 6, the load 5 and the capacitor 4,

After the end of the half-period of the operating frequency, the action of the signal of the control unit 16 causes the opening of the transistor 11 and the locking

transistor 12. In this case, half of the winding 10 of the current transformer 6 is short-circuited through transistor 11 and diode 14. This leads to the disappearance of the base current in transistor 1 and its locking after the resorption time of the excess carriers.

At the same time, the resistor 15, the left half of the winding 10 of the current transformer 6 and the transistor 11 are flowing from the power source and the current is sufficient to turn on the power transistor 2, the latter is unlocked as soon as the transistor 1 is locked, then the load current flows through the capacitor 3 and load 5, the winding 7 of the current transformer 6 and the transistor 2. After the half period expires, the processes in the circuit are repeated,

In this mode of operation, the voltage drop across the resistor 18 is less than the voltage of the reference source 19 and the operation of the threshold element

20 does not occur. For this reason, security features do not affect her work,

In current overload mode, instantaneous voltages at all,

The windings of the current transformer increase in proportion to the collector currents of the power transistors, which is explained by the type of volt-ampere input characteristic of the power transistors and the presence of active resistance of the base windings of the current transformer.

When the voltage on the resistor 18 reaches the reference source 19, the threshold element 20 is triggered, and a positive signal is generated at its output through the matching circuits (in this case, the diodes 21, 22

and resistors 23, 24) and, if necessary, through an amplifier to the control electrodes of transistors 11 and 12, this signal causes the switching on of both transistors 11, 12 and, respectively

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Specifically, the switching off of the power transistors 1 and 2. Thus, their current protection in the overload mode is ensured. When the collector current drops below a predetermined level, the threshold element 20 returns to its initial state after a predetermined time determined by the delay, and the switching of the power transistors resumes. The required level of protection performance is established by selecting the appropriate resistances of the resistors 17 and 18.

Thus, the proposed device allows, without an additional current sensor, to provide protection of the power transistors against overcurrent, which significantly improves the overall dimensions of the circuit in a given temperature range.

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Claims (1)

Invention Formula A DC converter containing a power amplifier with power transistors, the inputs of which are connected to one of the windings of a current transformer, the second winding of which is connected to the output circuit of the power amplifier, and the control winding is connected to the collectors of control transistors, the bases of which are connected to the outputs of the control unit inputs connected to the output of the protection node overload, the input of which is connected to the output of the overload current sensor, characterized in that, in order to improve the weight and size of azateley, overload current sensor input connected to the secondary winding of the control point.