UA15199U - Device for protecting electric circuits against short circuits - Google Patents

Abstract

The proposed device for protecting electric circuits against short circuits contains a thyristor switch with a control circuit for the thyristor, a control unit, an input switch, and additionally, a testing unit and a differentiator. The switch is inserted between the power-supply source and the load. The input of the control unit is connected to the thyristor control circuit. The testing unit is connected in parallel to the switch. The output of the testing unit is connected to the input of the control unit. The input of the differentiator is connected to the control input of the testing unit, and the input is coupled with the input switch.

Description

Description of the invention

The useful model belongs to means of protection of electronic devices, for example devices and systems 2 of automotive electronics, against overload by current. Protection against current overload, and in particular against "short circuits", is an important consumer property during the operation of electronic devices.

Traditionally, fuses are used for this purpose in the supply circuit or in the load circuit.

However, the blowout time of fuses reaches tenths of a second, which can lead to failures of electronic equipment.

The solution to this problem is the application of fast-acting electronic protection circuits, so-called "electronic fuses".

A well-known short-circuit protection device | Aleksandrov I. Zlectronniy fuse // Magazine "Radio". - 2000. - Mo2. - P. 54| made on the basis of a transistor switch with a current sensor in the emitter circuit. Disadvantages of such a schematic solution include additional voltage losses on the current sensor 12 and the large power released by the transistor key during "short circuits" in the load.

Another well-known device for protection against "short circuits" (Nechaev I. Zlektronnyi predokhranitel. // Journal "Radio". - 2005. - Mob. - P. 25| selected as a prototype. The device uses an original schematic solution in which the power the transistor performs the functions of an electronic key and a current sensor at the same time, as such, the resistance of the open channel of the transistor is used. However, this resistance depends on the voltage at the taps of the power transistor and the temperature of the case and can vary within 20...30 95, and this is not in any the second disadvantage of this device can be considered to be non-sustainable disconnection of the load at low triggering current, which will require the introduction of an additional resistor to the load circuit to increase the resistance of the current sensor. This actually means preserving the disadvantages of the previous scheme.

The basis of a useful model is the task of creating such a device for protection against "short circuits", in which additional voltage losses on the current sensor, and with large switching currents - and noticeable power losses - would be excluded. This is possible in case of refusal to use the current sensor, then the losses will be determined only by the residual voltage at the emitter-collector transition of the transistor switch in the saturation mode. at

The problem is solved by the fact that the device protects against "short circuits", according to the useful Ge»! model, contains a transistor key connected between the power source and the load, a protection node, the output of which is connected to the control input of the transistor key, a "start" switch, and additionally contains a testing node that shunts the transistor key, and the output is connected to at the input of the protection node, a differentiating circuit, the output of which is connected to the start input of the testing node, and the input is connected to the "start" switch. 3о The essence of the "short circuit" protection device is shown in the block diagram. --

The short-circuit protection device includes a transistor switch 1, connected between the power source and the load, the input is connected to the output of the protection node 2, with the input of which the testing node 3, the differentiating circuit, 4 and the "start" switch 5 are connected in series , and with its measuring inputs, the testing node C is connected in parallel with the transistor key 1. C 50 The device works in the following way. c In the initial state, transistor switch 1 is closed. When the "start" switch 5 is pressed, the differentiating circuit 4 on the leading edge of its signal produces a short pulse that connects the load to the test node 3. If the load is shorted, the voltage on it is zero and the protection node 2 will be blocked, and transistor switch 1 will remain closed. In the case when there is no "short circuit" in the load, a short test pulse creates a voltage in the load sufficient to unlock - the protection node 2 and the subsequent activation of the transistor key, which will ensure the transmission of the supply voltage to the sl load with minimal losses.

Given the fact that the protection device cannot be disabled during a long "short circuit" in the load, the output switch can be selected without large reserves from the output current. (Te) 20 Thus, the proposed useful model has low losses, increased reliability and economy. 3e)

Claims (1)

The formula of the invention Protection device against short circuits, which contains a transistor key, included between the power source c and the load, a protection node, the output of which is connected to the control input of the transistor key, a start switch, which is distinguished by the fact that in order to minimize losses, it additionally contains a node testing, which shunts the transistor key, and the output is connected to the input of the protection node, a differentiating circuit, the output of which is connected to the start input of the test node, and the input is connected to the start switch. 60 b5