RU2360358C1 - Electronic relay with transformer isolation and protection from current overload - Google Patents

Abstract

FIELD: electronics.

SUBSTANCE: invention relates to electronic engineering and may be used in switching systems with galvanic isolation and overload protection by current. According to the invention, transformer isolation has to be implemented by protecting relay from current overloads both in transient mode when load is switched on, and in stabilised conditions and enabling control of protection parameters depending on load parametres. In order resolve to the above mentioned task, in addition to pulse generator, pulse transformer, rectifying diode, filter capacitor and electronic switch in electronic relay with transformer isolation, the filter capacitor, discharge resistor, stabilised voltage source, load current sensor, operating amplifier, relay element, reference input element for relay element, integrating element and "latch" consisting of n-p-n and p-n-p transistors and load resistor are included in transistor. Time of protection from current surges during load switching is proportional to the integrating element capacity. Threshold of protection actuation may be adjusted changing resistance in reference input element of relay element.

EFFECT: wide functional possibilities of electronic relay.

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Description

The invention relates to the field of electronic technology and can be used in switching devices with galvanic isolation and with protection against overcurrent.

Known electronic relay with transformer isolation, containing a pulse generator, a pulse transformer, a rectifying diode, a filter capacitor and an electronic switch on a transistor [1] (US Patent No. 4346375, G08 21/00 from 08/24/1982).

The closest technical solution to the proposed device is an electronic relay with transformer isolation, containing a pulse generator, a pulse transformer, a rectifier diode, a current limiting resistor, a discharge device and an electronic key on a MOS transistor (US Patent No. 4438356 dated 03.20.1984, H03K 17 / 687) [2].

The lack of overcurrent protection is a significant drawback of the known devices, since if the current exceeds the permissible load, for example, due to a power supply failure, the electronic key transistors or the load may fail.

The second significant drawback of the known devices is that these devices do not disconnect the load from the voltage source, which in many cases is unacceptable due to the high probability of false signals or commands being issued by failed devices.

The objective of the invention is the expansion of the functionality of an electronic relay with transformer isolation due to the protection of the relay against overcurrent both in the transient process when the load is turned on and in the steady state, as well as due to the possibility of regulating the protection parameters depending on the load parameters.

To achieve the above technical result, an electronic relay containing a pulse generator, a pulse transformer, a rectifying diode, a current limiting resistor, an electronic key on a MOS transistor, input and output terminals, the input terminals of the relay being the power supply of the pulse generator, the output of which is connected to the primary winding a pulse transformer, the first output of the secondary winding of which is connected to the anode of the rectifier diode, the cathode of the rectifier diode through a current-limiting rubber the torus is connected to the gate of the MOS transistor of the electronic switch, the drain of which is the first output of the relay, a filter capacitor, a discharge resistor, a stabilized voltage source, a load current sensor, an operational amplifier, a relay element, a relay element adjuster, an integrating link and a “latch” are added from npn and pnp transistors and a load resistor, and the load current sensor with its first output is connected to the source of the MOS transistor of the electronic key, and the second output is connected to the second output relay, second output of the secondary winding of the pulse transformer, first output of the filter capacitor, discharge resistor, master switch of the relay element and the integrating element, emitter npn of the “latch” transistor, negative bus of the stabilized voltage source, negative bus of the relay element, first input of the stabilized voltage source, second input which is connected to the second output of the filter capacitor and the discharge resistor, the cathode of the rectifier diode and the first output of the current-limiting resis ora, the second output of which is connected to the gate of the MOS transistor of the electronic switch, and the output of the stabilized voltage source is connected to the second output of the relay element master, a positive power bus of the relay element and operational amplifier, the inputs of which are connected to the terminals of the load current sensor, and the output to the non-inverting input of a relay element, the inverting input of which is connected to the output of the master of the relay element, the output of the relay element through an integrating link is connected to the base npn and collector p-n-p transistors "latch", and the collector n-p-n transistor is connected to a first terminal of the load resistor and the base of p-n-p transistor, the emitter of which is connected to a second terminal of the load resistor "latch" gate MOS electronic key transistor and the second terminal of the current limiting resistor.

The drawing shows a block diagram of an electronic relay with transformer isolation with overcurrent protection, while in the drawing and further in the text are indicated:

1 - electronic key;

2 - pulse generator;

3 - pulse transformer;

4 - rectifying diode;

5 - current limiting resistor;

6, 7 - input terminals of the relay;

8, 9 - output terminals of the relay;

10 - filter capacitor;

11 - discharge resistor;

12 - source of stabilized voltage;

13 - load current sensor;

14 - operational amplifier;

15 - relay element;

16 - switch relay element;

17 - integrating link;

18 - "latch";

19 - p-n-p transistor;

20 - n-p-n transistor;

21 - load resistor;

22 - primary winding of a pulse transformer;

23 - secondary winding of a pulse transformer;

U _upr - control voltage;

± U _com - switching voltage;

With _I - the input capacitance of the MOS transistor of the electronic key;

I _LOAD - load current.

An electronic relay with transformer isolation and overcurrent protection is as follows.

The input terminals of the relay 6, 7 are the power supply inputs of the pulse generator 2, the output of which is connected to the primary winding 22 of the pulse transformer 3. The first output of the secondary winding 23 of the pulse transformer 3 is connected to the anode of the rectifier diode 4. The cathode of the rectifier diode 4 is connected to the gate through a current limiting resistor 5 MOS transistor of electronic key 1, the drain of which is the first output of relay 8.

The load current sensor 13 with its first output is connected to the source of the MOS transistor of the electronic switch 1, and the second output is connected to the second output of the relay 9, the second output of the secondary winding 23 of the pulse transformer 3, the first conclusions of the filter capacitor 10, the discharge resistor 11, the setter of the relay element 16, integrating link 17, the emitter of the npn transistor 20 of the "latch" 18, the negative power bus of the operational amplifier 14 and the relay element 15 and the first input of the stabilized voltage source 12. The second input of the stabilizer source voltage 12 is connected to the second terminals of the filter capacitor 10, the discharge resistor 11, the cathode of the rectifier diode 4 and the first terminal of the current-limiting resistor 5, the second terminal of which is connected to the gate of the MOS transistor of the electronic switch 1. The output of the stabilized voltage source 12 is connected to the second terminal of the relay element 16, the positive power bus of the relay element 15 and the operational amplifier 14, the inputs of which are connected to the terminals of the load current sensor 13, and the output to the non-inverting input a relay element 15, the inverting input of which is connected to the output of the relay element 16. The output of the relay element 15 is connected to the base npn 20 and the collector pnp 19 of the “latch” transistors 18 through the integrating link 17, and the collector npn of the transistor 20 is connected to the first output of the load resistor 21 and the base pnp of the transistor 19, the emitter of which is connected to the second terminal of the load resistor 21 of the "latch" 18, the gate of the MOS transistor of the electronic key 1 and the second terminal of the current-limiting resistor 5.

The drawing shows the simplest embodiment of the elements of the block diagram of the device. At the same time, the elements of the proposal may have unprincipled differences. So, the load current sensor 13 can be performed using low-resistance, of the order of (1-2) mOhm non-inductive resistors, the trigger threshold 16 of the relay element 15 may have two (R1, R2) resistors or a potentiometer. Instead of the integrating link 17 in the form of the simplest R3C1 chain, two-link ones can be used.

As elements for the implementation of the device, serial microcircuits can be used, for example, microcircuits of the 1467 series for the implementation of operational amplifier 14 and relay element 15, 142EP2N4IM for a stabilized voltage source. As a pulse transformer 3 can be used transformers type TII4. The pulse generator 2 can be performed on microcircuits of the type 1526LN2 according to the circuit shown in the prototype, or according to another circuit on CMOS microcircuits.

An electronic relay with transformer isolation and with protection against overcurrent operates as follows.

After applying control voltage U to the input terminals of the relay 6, 7, the _control oscillator 2 generates rectangular pulses, which from its output go to the primary winding 22 of the pulse transformer 3. At the secondary winding 23 of the pulse transformer 3, rectangular pulses are also formed, which are rectified by a rectifying diode 4 and are filtered by the filter capacitor 10. The positive voltage from the filter capacitor 10 is supplied to the inputs of the stabilized voltage source 12. From the output of the stabilized voltage source 12 the voltage is supplied to the positive power bus of the operational amplifier 14, the relay element 15 and to the second terminal of the master of the relay element 16, the first terminal of which is connected to the negative power bus of the operational amplifier 14, the relay element 15 and the first output of the filter capacitor 10, the second terminal of the secondary winding 23 of the pulse transformer 3, the second output of the discharge resistor 11, the second output of the load current sensor 13, the second output of the setpoint relay element 16, the first output of the capacitor of the integrating link 17 and Mitter transistor 20 "latch" 18. The current through resistor R1 setpoint threshold triggering relay element 16 generates on the inverting input of the relay member 15 (on the resistor R2) blocking voltage.

At the same time, the voltage filtered by the filter capacitor 10 through a current-limiting resistor 5 charges the input capacitance of the MOS transistor of the electronic switch 1.

After charging the input capacitance C _in above the threshold voltage of the MOS transistor, the electronic switch 1 switches to the on state, creating a low resistance for the load current to flow I _heat through

open MOS transistor.

When the flow of the load current I _LOAD via an outdoor electronic key MOS transistor 1 and connected to it a load current sensor 13, at the last a voltage drop proportional to the load current I _LOAD. This voltage, which is a unit of millivolts, is fed to the input of the operational amplifier 14, amplified by it and, from its output, is fed to the non-inverting input of the relay element 15.

The voltage supplied to the inverting input of the relay member 15 from the output setpoint relay element 16, sets the maximum load current I _LOAD relay at which the electronic key disabling MOS transistor 1.

If at some point in time or at the moment the relay is turned on, the current does not exceed the limit value, then the relay element 15 remains in a state when the signal log is at its output. "0", which through the integrating link 17 enters the base n-p-n of the transistor 20 of the "latch" 18 and saves the state of the "latch" as off.

If at some point in time or at the moment when the relay load current I _LOAD relay exceeds a predetermined value at which the overload protection is triggered, the output of the operational amplifier 14 will form a voltage greater than the voltage output from the set point relay element 16. The output of the relay element 15 is formed a signal log. "1", which through the integrating link 17 enters the base npn of the transistor 20 of the "latch" 18 and opens it. Through an open npn transistor 20, the collector - emitter base connects the base of the pnp transistor 19 to the negative power bus of the operational amplifier 14, relay element 15, to the output terminal of the relay 9 (-U _com ), the second terminal of the secondary winding 23 of the pulse transformer 3, the first terminal of the capacitor a filter 10, a discharge resistor 11, a setter of a relay element 16, and an integrating link 17.

Through the open npn transistor 20, pnp transistor 19 "latch" 18 the gate of the MOS transistor of the electronic key 1 is connected to the negative bus -U _com (pin 9) and the electronic key is closed. The open state of transistors 19, 20 of the "latch" 18 is maintained after turning off the MOS transistor of the electronic key 1, reliably holding the MOS transistor of the electronic key 1 in the off state.

By changing the resistance R2 in the setpoint of the relay element 16, it is possible to rebuild the protection thresholds both during switching-on and in the steady-state load mode, always preserving the specified margin of protection against overload.

The response time of the overload protection against inrush currents when the load is turned on is proportional to the capacitance C1 of the integrating link 17, therefore, the capacitance C1 of the integrating link 17 filters and does not pass short interference signals to the input of the “latch” 18 when the load is turned on.

The relay is turned off both in the relay overload mode and in the nominal mode by disconnecting the control voltage U _control from the input terminals of the relay 6, 7. The pulse generator 2 is turned off, the filter capacitor 10 is smoothly discharged through the discharge resistor 11, and the input capacitance C _in - through the resistor discharge 11 and current-limiting resistor 5, thereby eliminating surges in the load when the relay is turned off.

Compared with the known relay with transformer isolation [2], the present invention extends the functionality by providing protection against overcurrent both in transition mode when the load is connected to the relay, and in steady state.

The time of inrush protection when the load is switched on is proportional to the capacitance C1 of the integrating link 17.

The protection threshold can be tuned by changing the resistance R1 in the setpoint of the relay element 16.

Claims (1)

An electronic relay with transformer isolation and overcurrent protection, comprising a pulse generator, a pulse transformer, a rectifier diode, a current limiting resistor, an electronic switch on a MOS transistor, input and output terminals, the input terminals being power supply inputs of the pulse generator, the outputs of which are connected to the primary winding of a pulse transformer, the first output of the secondary winding of which is connected to the anode of the rectifier diode, the cathode of the rectifier diode through a current-limiting re the source is connected to the gate of the MOS transistor of the electronic switch, the drain of which is the first output of the relay, characterized in that it is additionally equipped with a filter capacitor, a discharge resistor, a stabilized voltage source, a load current sensor, an operational amplifier, a relay element, a relay element regulator, an integrating element and a “latch” consisting of npn and pnp transistors and a load resistor, and the load current sensor is connected by its first output to the source of the MOS transistor of the electronic key, and by the second the house is connected to the second output of the relay, the second output of the secondary winding of the pulse transformer, the first output of the filter capacitor, the discharge resistor, the setpoint of the relay element and the integrating element, the emitter npn of the “latch” transistor, the negative bus of the relay element, the first input of the stabilized voltage source, the second input of which connected to the second output of the filter capacitor and the discharge resistor, the cathode of the rectifier diode and the first output of the current-limiting resistor, and the output of the stabilization source voltage is connected to the second terminal of the relay element master, the first terminal of which is connected to the negative power bus of the operational amplifier, and the positive power bus of the relay element and operational amplifier, whose inputs are connected to the terminals of the load current sensor, and the output to the non-inverting input of the relay element, inverting the input of which is connected to the output of the master of the relay element, the output of the relay element through an integrating link is connected to the base npn and collector pnp transistors Christmas tree ”, the collector of the n-pn transistor connected to the first output of the load resistor and the base of the pnp transistor, the emitter of which is connected to the second output of the load resistor“ latch ”, the gate of the MOS transistor of the electronic key and the second output of the current-limiting resistor.