SU1656564A1 - Transistorized current limiter - Google Patents

Abstract

The transistor current limiter relates to automation and computing. The purpose of the invention is to expand the functionality by increasing the range of limiting currents. The goal is achieved by the fact that the emitter is the output of the current limiter and, through a current-creating resistor, is connected to the emitter of the current-limiting transistor, a thermal reverse element is inserted into the current limiter containing the compensating transistor, the emitter is the current limiter output. connection, made of heat-conducting insulating material and in direct contact with external terminals of the current-limiting and base-collector compensating transistors. 2 Il.

Description

yo

This invention relates to automation and computing.

The purpose of the invention is to expand the scope by increasing the range of current limited.

Figure 1 is a schematic diagram of a current limiter; Fig. 2 shows a thermal feedback element.

The current limiter contains an input resistor 1, an emitter follower (current-limiting transistor) 2 with a current generator 3 in the emitter circuit, a current-setting resistor 4 and a compensating Toazistor 5. The load resistance is indicated by position 6. And the current limiter output is position 7. Between the current-limiting collector area the transistor 2 and the transition region of the base emitter of the compensating transistor 5 include a thermal feedback element 8 made of thermally conductive insulating material, such as mica, heat thickness conductive insulating element 0.1-0.3 mm, and the length is determined by the mutual arrangement of transistors.

Transport current limiter works as follows.

When current is supplied, the output current of the current-limiting transistor 2 does not exceed a certain specified value (max, the voltage drop across resistor 4 is not enough to unlock transistor 5 and the device operates as a linear emitter follower. But if the output current reaches the Output level (max, at which life on resistor 4 exceeds oo

ate about

the horn of unlocking the Vo transistor 5 (Vo - 0.7 V for silicon transistors), the transistor 5 is unlocked and its collector circuit shunts the input of the emitter follower, limiting its output current to I max.

In the short-circuit mode, due to an increase in the voltage across the current-limiting transistor, the power dissipated by it increases sharply. This leads to an increase in its temperature and due to thermal coupling to an increase in the temperature of the compensating transistor, which causes a decrease in its threshold for unlocking Vo, and consequently, reduces the power in the short-circuit mode. In this way, the ratio Δfma is reduced (hp / pmaxi, which allows the use of less powerful transistors or the selection of a larger value (max.

The efficiency of the device is higher, the lower the resistance of the thermal coupling element 8, i.e. the greater the temperature change of the transistor 5 under the effect of a change in power on the transistor 2. Go

Bh

However, regardless of the amount of thermal resistance, the introduction of a thermal feedback element provides a positive effect.

Claims (1)

Invention Formula A transistor current limiter containing a compensating transistor, the collector and base of which are connected respectively to the base and emitter of the current-limiting transistor, and the emitter is the output of the current limiter and is connected to the emitter through the current-emitting resistor current-limiting transistor, characterized in that, in order to expand the scope of application by increasing the range of limited currents, an element of thermal reverse connection, made of heat conducting insulating material and in direct contact with the terminals of the current-limiting collector and the base of the compensating transistors. 6 7yb 1