SU1690071A1 - Device for protection of electronic key - Google Patents

Abstract

The invention relates to electrical engineering. The aim of the invention is to increase the efficiency and reliability during long-term overloads and short circuits. The voltage on the key 1 and the threshold element 10 decreases slightly, and the key 1 remains in the locked state. In the overload mode, the current is determined by the resistance value of the resistor 3 during the time determined by the charging time of the capacitor 16. If during the charging time of the capacitor 16 the overload current does not decrease completely to the load current, the key 1 does not open and at the same time the key element 4 is closed .1 il.

Description

The invention relates to electronics and can be used to protect semiconductor switching devices in an electric drive, electrical technology, and in power supplies of radio equipment.

The purpose of the invention is improving efficiency and reliability during prolonged overloads. and with a short circuit.

The drawing shows a schematic diagram of a device for protecting an electronic key.

The device for protecting the electronic key contains a key 1, a shunt circuit 2, made on a series-connected current-limiting resistor 3 and a key element 4, the input of which is shunted by a resistor 5. Resistors 7 and 8 are connected to the output of the control signal source 6, the last of which is connected to the auxiliary collector the key made on the transistor 9, the base of which is connected to the output of the threshold element 10. made on a series-connected zener diode 11, a limiting resistor 12 and a resistor e 13. The load 14 is connected to the positive terminal of the power source 15, to which is also connected a circuit consisting of a series-connected capacitor 16, a resistor 17 and a collector-emitter junction of the transistor 18. the base of which is connected to the base of the transistor 19 and through the resistor 20 with the output of the element AND-NOT 21, both inputs of which are connected to the output of the AND-NOT 22 element, one of the outputs of which is connected to the resistor 23.

The device operates as follows.

In the absence of the unlocking signal of the source 6, the key 1 and the key element 4 are locked, the load 14 is disconnected from the power supply 15, the voltage on the key 1 and on the threshold element 10 connected in parallel to it is equal to the supply voltage. Thus through the zener diode 11 current flows, creating a resistor. 13 voltage drop. This voltage is applied to the base of the transistor 9 and keeps it open. Thus, the transistor 9 bypasses the input of the key 1 and thereby prevents the passage of the unlocking cwt cash to the net о οι of the source 6. The voltage from the resistor 13 also goes to one of the inputs of the INE 22. The second input of which has a low voltage level from the source 6. Thus, a high voltage level and, accordingly, is present at the output of the e / 'e-mail AND-NOT 22. at the output of the AND-NOT 21 element there is a low voltage level that keeps the transistor 19 open and the transistor 18 closed. The key element 4 is locked.

When the unlocking signal from source 6 appears, key 1 remains in the locked state, a high voltage level is present at both inputs of the AND-NOT 22 element. a low voltage level appears at the output of an AND-NOT 22 element, respectively, a high voltage level appears at the output of an AND-NOT 21 element, by which the transistor 18 is unlocked and the transistor 19 is locked. The key element 4 is opened by the transistor 18 and connects the load 14 through a current-limiting resistor 3 to a negative the clamp of the power source 15. The voltage on the key 1 and the threshold element 10 decreases and its value is determined by the value of the load resistance 14 and the limiting resistor 3. If the value of the load resistance 14 is more than acceptable, then the voltage at the output of the threshold element 10 is not enough to maintain the transistor 9 in the open state, it closes , which leads to the unlocking of the key 1, which connects the load to the source 15 PIUaniya.

As a result of switching on the key 1, the voltage at the output of the threshold element 10 decreases and the state at the output of the AND-21 element changes from a high voltage level to a low voltage level. Thus, the transistor 18 is locked and the transistor 19 is unlocked. An open transistor 19 provides a discharge of the capacitor 16. which is charged in the process of starting the key 1.

If there is an overload or short circuit, the voltage on the key 1 and the threshold element 10 will decrease slightly. and key 1 will remain locked. In overload mode, the current will be determined by the resistance value of the resistor 3 for a time determined by the duration of the charge of the capacitor 16. If during the charge of the capacitor 16 the overload current does not completely decrease to the value of the load current, key 1 will not open and at the same time key 4 will close. The capacitance of the capacitor 16 is selected based on the duration of the inrush currents that occur in the load.

Claims (1)

Claim A device for protecting an electronic key, comprising a shunt circuit made on a series-connected current-limiting resistor and a key element and designed to be connected in parallel with the electronic key, a control signal source, the output of which is shunted with an auxiliary key and designed for 5 connecting to the input of the electronic key, and a threshold element, the input of which is designed to be connected in parallel with the electronic key, and the output is connected to the input of the auxiliary key, distinguishing - 10 s I mean, in order to increase efficiency and reliability during prolonged overloads and short circuits, two transistors of different types of conductivity, a capacitor, two NAND elements and two resistors are introduced into it, and the emitter of the first transistor is connected to the input of the key element of the shunt circuit, the collector of the first transistor through the first resistor is connected to the collector of the second transistor and one terminal of the capacitor, the other terminal of which is connected to the emitter of the second transistor and to the terminal for connecting the positive output of the source Itani electronic key, inputs of first AND-NO element are connected respectively to the source of the control signal and the output of the threshold element, an output of first AND-NO element are connected in series through the second AND-NO element 15 and a second resistor connected to the bases of the two transistors combined.