RU2542950C1 - Overcurrent protection device - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: overcurrent protection device comprises in series busbar of input voltage positive potential and an electronic key, which control input is connected to output of the control element by the electronic key and through protective resistor - with input of current sensor, aperiodic link, threshold element, which input is connected through the resistor to the current sensor output and output of the aperiodic link, busbars of negative potential.

EFFECT: reducing actuation time of the overcurrent protection device and load protection from output voltage when its values are below than the permitted ones.

10 dwg

Description

The present invention relates to electronic means and can be used to transfer voltage from a power source to a load unit with protection against overcurrent, as well as to protect against overloading both the power source and the voltage switch itself. In addition, the device protects the load from unacceptably low voltage by completely removing it from the load.

Known compensation voltage stabilizer [1] with overcurrent protection, containing an electronic switch made on a transistor, a limiting resistor and a second transistor controlling the electronic switch.

The disadvantage of this device is the inability to completely disconnect the load from the voltage source during unauthorized lowering of the input voltage, which can lead to unacceptable modes of operation of the load unit. For example, if the load block is an electronic device, then the elements of this device will be under reduced unacceptable voltage.

A number of devices are known - voltage switches [2-5], built on the basis of a series-connected electronic switch and a shunt; to increase the voltage drop on which several times using the comparators and logic elements, the electronic key is controlled (turned off).

The disadvantage of such devices is insensitivity to random significant short-term drops in the input voltage, at which the voltage at the load is not removed, but reaches unacceptably low values.

As a prototype of the claimed device for the construction and functional purpose, you can specify the "Voltage Switch with overcurrent protection" [6].

The prototype device contains a serially connected bus of a positive potential of the input voltage, a load current sensor, an electronic key with a control circuit for turning it on / off, connected to the output of the electronic key through an aperiodic link, a bus of a positive potential of the output voltage, as well as a bus of negative input and output voltage. Buses of positive and negative potentials of the input voltage are the input of the device, buses of positive and negative potentials of the output voltage are the output of the device.

The disadvantages of the known device is the long response time of the overcurrent protection, which leads to significant pulsed emission of power on the electronic key, as well as the ingress of reduced (below the minimum allowable) voltage to the load when the input voltage is lowered (input voltage "dips").

The objective of the invention is the expansion of functionality due to the simultaneous protection against overcurrent, reducing the response time of the protection during overcurrent and protecting the load from the output voltage when its values are below acceptable.

This task is achieved by the fact that in the device of protection against overcurrent, containing a series-connected bus of positive potential of the input voltage, a current sensor, an electronic key, the control input of which is connected to the output of the control element of the electronic key and through a protective resistor to the input of the current sensor, and the bus of the positive potential of the output voltage connected to the input of the aperiodic link, a threshold element is additionally introduced, the input of which is connected through the resistor to the output of the current sensor and the output ohm of the aperiodic link, the common point of which is connected to the input of current sensors, the output of the threshold element is connected to the input of the electronic key control, and the input of the electronic key control is connected to the input and output buses of the negative voltage potential.

The functioning of the claimed device is illustrated in figure 1 ... 10.

Figure 1 shows the device overcurrent protection.

Figures 2 and 3 show embodiments of individual blocks of the overcurrent protection device with the same general logic of its operation and with the same input voltage and load parameters.

Figure 4 ... 10 shows the results of modeling (oscillograms) of processes in the devices shown in figures 1 ... 3.

The diagrams show:

1 - bus positive potential input voltage,

2 - bus negative potential input voltage,

3 - current sensor,

4 - electronic key (4a - input of the electronic key, 4b - output of the electronic key, 4c - control input of the electronic key),

5 - an electronic key control element, hereinafter referred to as block 5 (5a - input of an electronic key control element - input of a block 5, 5b - output of an electronic key control element - output of a block 5, 5c - control input of an electronic key control element - control input block 5)

6 - aperiodic link - consisting of:

15 - input resistor,

16 - output resistors

17 is a capacitor

6a - input aperiodic link, 6b - output aperiodic link

7 - protective resistor,

8 - resistor

9 - threshold element (zener diode in figure 2 and 3),

10 - bus positive potential output voltage,

11 - bus negative potential output voltage,

12 - voltage source,

13 - switch

14 - load unit with an active component (32) and a capacitive component (33).

The electronic key 4 (figure 1) contains a field effect transistor 18 and a protective zener diode 19.

The electronic key 4 (figure 2) contains a push-pull repeater made on transistors 24 and 25 and a resistor 26.

The electronic key 4 (Fig.3) is made on the transistor 31.

Block 5 (figure 1) contains the operating resistors 21, 22 and a protective zener diode 23.

Block 5 (figure 1 and 2) contains the operating resistors 28, 29 and protective

diode 30.

Figure 4 ... 10 shows: + IN (point 1 in figure 1 ... 3) is an example of the shape of the voltage supplied to the input of the device, + OUT (point 10 in figure 1 ... 3) is the voltage at the output of the device, I _H - load current flowing through the bus 10 of the positive potential of the output voltage, I _DOP - an example of load changes (additional current flowing through the device), P is the power dissipated by the electronic key 4.

The graphs shown in figure 4 ... 10 are the result of mathematical modeling of the claimed device.

The device shown in figure 1 ... 3 is as follows.

The bus 1 of the positive potential of the input voltage is connected through the current sensor 3 to the input (4a) of the electronic key 4 and the common point (6c) of the aperiodic link 6. The output (4b) of the electronic key 4 is connected to the bus 10 of the positive potential of the output voltage (device output) and the input (6a) of the aperiodic link 6. The output (6b) of the aperiodic link 6 is connected to the input (9a) of the threshold element 9 and through the resistor 8 to the output of the current sensor 3. The output (9b) of the threshold element 9 is connected to the control (5c) input of the block 5. The input (5a) of block 5 is connected to the negative bus 2 Nogo potential input voltage bus 11 and the negative potential of the output voltage. The output (5b) of block 5 is connected to the control input (4c) of the electronic key 4 and through a protective resistor 7 to the input of the current sensor.

Figure 1 ... 3 shows three options for building an electronic key 4 and two options for building block 5.

In accordance with figure 1, the electronic switch 4 contains a p-channel field effect transistor 18 and a protective zener diode 19 connected between the source and the gate of the transistor 18. The source, drain and gate of the transistor 18 are, respectively, the input (4a), output (4b) and control input (4c) of the electronic key 4.

In accordance with figure 2, the electronic key 4 is made in the form of a push-pull repeater and consists of a power npn transistor 24, the collector of which is the input (4a) of the electronic key, and the emitter is the output (4b) of the electronic key 4. npn transistor 25 is connected by the emitter to the collector npn of transistor 24, the base of which is connected to the collector of npn of transistor 24. The base of npn of transistor 25 is the control input (4c) of electronic key 4. Resistor 10 is connected between the base and emitter of npn of transistor 26.

In accordance with figure 3, the electronic key 4 contains an n-p-n transistor 31. The emitter, collector and base of the transistor 31 are, respectively, the input (4a), output (4b) and the control input (4c) of the electronic key 4.

The aperiodic link 6 is made in the form of a three-terminal network with input (15) and output (16) resistors and a capacitor 17 connected to resistors 12 and 13 with one terminal and a common point (6c) of the three-terminal terminal with another terminal.

Block 5 (in accordance with figure 1) is made on an n-channel field effect transistor 20 with a resistor 21 and a zener diode 23 between the source and the gate. A resistor 22 is connected to the drain of the transistor 20, the second output of which is the output (5b) of block 5. The source of the transistor 20 is the input (5a) of block 5, and the gate is its control input (5c).

Block 5 (in accordance with figures 1 and 2) is made on a bipolar n-p-n transistor 27 with a resistor 29 and a diode 30 between the emitter and the base. A resistor 28 is connected to the collector of the transistor, the second output of which is the output (5b) of block 5. The emitter of the transistor 27 is the input (5a) of block 5, and the base is its control input (5c).

The overcurrent protection device operates as follows.

Let, for example, at time t ₁ (Fig. 4), when the switch 13 is closed between the bus 1 of the positive potential of the input voltage and the bus 2 of the negative potential of the input voltage of the device, + IN is applied for a time from t ₁ to t ₂ . At the input 9a of the threshold element 9, a voltage occurs due to the first current flowing in the circuit: bus 1 of the positive input voltage potential → capacitor 17 → resistor 16 → input resistance of the threshold element 9 and the second current in the circuit: bus 1 of the positive input voltage potential → current sensor 3 → resistor 8 → the input resistance of the threshold element 9. If the voltage at the input 9a of the threshold element 9 exceeds its response threshold, then a voltage appears at its output 9b, opening the transistor 20 of block 5. As a result When current flows through an open transistor 20, a voltage appears between the source and gate of transistor 18, which opens the latter.

A current I _H flows through an open transistor 18 (Fig. 4) along the circuit: bus 1 of the positive potential of the input voltage → current sensor 3 → transistor 18 → bus 10 of the positive potential of the output voltage → load block 14 → bus 11 and 2 of the negative potentials of the output and input stresses.

The purpose of the aperiodic link 6 is a) to protect the signal at the input 9a of the threshold element 9 from the "zero" (low) potential from the moment of closure of the switch 13 to the opening of the transistor 18 and the appearance of voltage on the load 14 (i.e., during the transition rise time current to the nominal value, b) forced supply of voltage to the input 9a of the threshold element 9 through the capacitor 17.

The purpose of the protective zener diodes 19 and 23 is to limit the voltages at the gates of transistors 18 and 20 from unacceptable values (in accordance with the specifications for these transistors). The resistor 21 provides a "binding" of the gate of the transistor 20 to its source.

The ratio of the values of the resistors 7 and 22 is selected from a compromise between the minimum voltage drop on the electronic key 4 and the maximum possible operating current I _H (Fig. 4) to the load (load block 14).

If at some point in time (t ₃ ) the current I _H can reach unacceptable values, i.e. there is an additional current I _ADC , for example, as shown in Fig. 4 (the possible current value is 10A), the current I _H increases to the limits determined by the characteristics of the transistor 18 at the given values of the resistors 7 and 22 (section from t ₃ to t ₄ ) and current through the transistor 20. The resistance of the electronic switch 4 begins to increase, which leads to an increase in the voltage drop across it. In this case, the voltage + OUT on the load block begins to decrease 14 and after a time determined by the time constant τ = R (15) · C (17), the voltage at the input 9a of the threshold element 9 decreases, which leads to its disconnection and, as a result, to the removal of voltage from the input 5c of block 5. In addition, a decrease in the voltage at the input 9a of the threshold element 9 contributes to an increase in the voltage drop at the shunt 3, transmitted through the resistor 8. The action of these factors closes the transistors 20 and 18 and stops the current (voltage) supply per load unit 14. Weight l the process of turning off the electronic key 4 takes place in the range from t ₃ to t ₄ : the current I _H first increases due to the delay associated with the time constant τ, and then stops. The transition process time, depending on the parameters of the device, is from 2 to 8 ms.

As a threshold element 9, a standard threshold microcircuit can be used (for example, a Schmidt trigger) or, in the simplest case, a zener diode, as shown in Figs. 2 and 3. For these cases, zener diodes with a stabilization voltage of 6 to 12 V.

The loss of overload (I _DOP ) at time t ₅ does not turn on the electronic key 4 - its inclusion is possible only when the device is restarted.

The graph "P" (figure 4) shows the pulse power dissipated by the transistor 18. Calculations show that the energy dissipated by the transistor 18 does not exceed 0.2 J, with typical allowable values for field-effect transistors (in this class, for a current of more than 5 A) from 0.4 to 0.7 J.

In the presence of "surges" of the input voltage, the "Overcurrent protection device" responds as follows:

1) Does not respond to excess voltage (in terms of protection operation),

does not respond to undervoltage (in terms of protection operation), if it is within acceptable values (Fig. 5).

2) Turns off if it is below the permissible values (Fig.6).

3) Turns off, and then automatically turns on if the input voltage is below acceptable values (Fig.7).

The setting for modes 2) or 3) is carried out in the manufacture of the device by selecting a resistor 16. For example, with an input voltage of 30 V, mode 2) is performed with the resistance of resistor 16 in the range from 100 to 900 Ohms, and mode 3) is guaranteed to be carried out with the resistance of resistor 16 more than 1 kOhm.

Figure 2 and 3 show the construction options of the inventive device. All processes in them proceed as described above.

Figs. 8 and 9 illustrate the processes in the device of Fig. 2.

On Fig shows an example similar to that shown in Fig.6.

In Fig.9 shows an example similar to that shown in Fig.7.

Figure 10 illustrates the processes in the device of figure 3

Compared with the known device [6], the present invention extends the functionality by simultaneously protecting against overcurrent, reducing the response time of the overcurrent protection and protecting the load from the output voltage when its values are below acceptable.

The proposed set of features in the solutions considered by the authors was not found to solve the problem and does not follow explicitly from the prior art, which allows us to conclude that the technical solution meets the criteria of "novelty" and "inventive step".

Literature

1. Sources of power for electronic equipment. Handbook edited by G.S. Naivelt. Moscow: Radio and Communications, 1986, p. 1896, Fig. 5.19.

2. Description of the invention to the patent of the Russian Federation No. 22010183, H03K 17/08.

3. Description of the invention to the patent of the Russian Federation No. 2258302, H03K 17/08.

4. Description of the invention to the patent of the Russian Federation No. 2240647, H03K 17/08.

5. Description of the invention to the patent of the Russian Federation No. 2208292, H03K 17/08

6. Description of the invention to the patent of the Russian Federation No. 2338843, H03K 17/08

Claims (1)

An overcurrent protection device comprising a series-connected bus of positive potential of the input voltage, a current sensor, an electronic key, the control input of which is connected to the output of the electronic key control element and, through a protective resistor, to the input of the current sensor, and a bus of the positive potential of the output voltage connected with an input of an aperiodic link, characterized in that a threshold element is additionally introduced into it, the input of which is connected through a resistor to the output of the current sensor and the output of ap of a periodic link, the common point of which is connected to the input of current sensors, the output of the threshold element is connected to the input of the electronic key control element, and the input of the electronic key control element is connected to the input and output buses of the negative voltage potential.

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