RU2432656C1 - Electronic fuse with self-recovery - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: circuit of an electronic fuse is arranged according to the principle of a threshold device in the form of a quadripole. An inlet of an auxiliary power supply source, the outlet of which is connected to power supply inlets of the following components, is connected to inlet poles of the quadripole: a differential amplifier, a voltage comparator, a thyristor switch and a controlled generator of recovery pulses; an inlet of a short-circuit current limiter is connected to the inlet positive pole, and its outlet is connected to a source of a power MIS transistor, a drain of which is connected to the inlet of a start-up current limiter, which is connected to the outlet negative pole. The outlet of the start-up current limiter is connected with the outlet positive pole, and the first inlet of the differential amplifier and the first outlet of the resistive current sensor are connected to the inlet negative pole, and the second outlet of the resistive current sensor is connected to the output negative pole and the second inlet of the differential amplifier.

EFFECT: minimisation of energy released in a spark gap in case of short circuit, increased efficiency, elimination of actuation when connected to a resistive-capacitance load or a load with start-up current.

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Description

The invention relates to devices for protecting loads and output power circuits of secondary power supplies from overloads and short circuits (short circuits) in current. It can be used to protect automation circuits, expensive and explosion-proof electrical equipment.

Known protection device against short-circuit and excess current in the load [Shustov MA Practical circuitry. Book 4. "Control and protection of power sources." M .: Dodeka-XXI Publishing House, Alteks, 2007, p. 50, Fig.5.5], in which a thyristor with a current sensor on a resistor is used. When the current in the load increases, the thyristor turns on, bypassing the control circuit of the transistor, after which the output voltage drops to zero. To restart after eliminating the causes of overload, press the button and unlock the thyristor.

This protection device has limited functionality, since it does not allow redundancy (“hot” reserve) of protection channels, and it does not have an automatic self-healing function. In addition, a relatively high additional power is dissipated on the resistance of the sensor connected directly to the thyristor control electrode.

A device for protecting a power source from a short circuit is known. [Shustov M.A. Practical circuitry. Book 4. "Control and protection of power sources." M .: Dodeka-XXI Publishing House, Altex, 2007, p. 57, Fig. 5.11]. This is a thyristor-transistor circuit, which works as follows: in normal mode, the thyristor is turned off, Darlington transistors are in a saturated state. When short current begins to flow through the load through the thyristor control electrode - it turns on and bypasses the control circuit of the Darlington transistor, the current through which is reduced to a minimum.

This device has limited functionality, since it does not allow redundancy (“hot” reserve) of protection channels, and there is no automatic self-healing function in it. In addition, a significant part of the supply voltage drops on Darlington transistors and a correspondingly large power dissipates.

A protection device (electronic fuse) is known [Patent for the invention No. 2185016 RU], which contains a power MOS transistor, a control transistor, a zener diode, six resistors, a switch, a fuse, a control device, two voltage comparators, a thermistor, a diode for forced discharge of the input capacitor power MOS transistor.

This protection device has limited functionality, since it does not allow redundancy (“hot” reserve) of protection channels, which determines the reliability as insufficient for critical applications (for example, to protect expensive and explosion-proof electrical equipment). In addition, this device is non-self-healing (after eliminating the short circuit or overload, to turn the device into normal operation, turn off / on the power source or press the switch).

The closest to the proposed device in terms of features and the problem to be solved is the protection device [Shustov MA Practical circuitry. Book 4. "Control and protection of power sources." M .: Dodeka-XXI Publishing House, Alteks, 2007, p. 49, Fig. 5.3], containing a power MOS transistor operating in the key mode, a voltage comparator, two resistors connected to the comparator, a resistive current sensor , button. The trip current of the protection is determined by the ratio of the resistances of the resistors and the sensor. After the protection is activated, the button must be pressed to reconnect the load.

This protection device has limited functionality, since it does not allow redundancy ("hot" reserve) of protection channels, it does not have the function of automatically restoring normal operation, in addition, the known device has great limitations on the use of resistive capacitive loads and loads with inrush currents.

The inventive electronic fuse with self-healing ensures the achievement of the following technical result: improving the quality of the device (minimizing short-circuit energy, high efficiency, no tripping when turned on to a resistive-capacitive load or load with inrush current) and expanding functionality (redundancy of protection channels, self-healing).

The invention is illustrated in figure 1 ÷ 3, where figure 1 shows a structural diagram of a single-channel inventive device, figure 2 is a structural diagram of an n-channel inventive device ([n-1] channels - "hot" reserve), in Fig. .3 is a functional diagram of a single channel inventive device.

Figure 1 shows that a single-channel self-healing electronic fuse contains: a power MOS transistor 1 operating in the key mode, a voltage comparator 2, a resistive current sensor 3, and differs from the prototype in that it is made in the form of a four-terminal device (input positive pole 4, input negative pole 5, output positive pole 6, output negative pole 7; the output of the protected power supply is connected to the input poles 4 and 5, the load is connected to the output poles 6 and 7) and composition introduced: auxiliary power supply 8, short-circuit current limiter 9, a differential amplifier 10, a thyristor switch 11, having an installation input “S” and a reset input “R”, a driver 12, a controlled recovery pulse generator 13, a start current limiter 14; at the same time, the input of the auxiliary power supply 8 is connected to the input poles 4 and 5, the output of which is connected to the power supply inputs: differential amplifier 10, voltage comparator 2, thyristor switch 11, a controlled recovery pulse generator 13; to the input positive pole 4 is connected to the input of the current limiter short circuit 9, the output of which is connected to the source of the power MOS transistor 1, the drain of which is connected to the input of the start current limiter 14, which is connected to the output negative pole 7, the output of the start current limiter 14 is connected to the output positive pole 6; connected to the input negative pole 5 is the first input of the differential amplifier 10 and the first output of the resistive current sensor 3, the second output of which is connected to the output negative pole 7 and the second input of the differential amplifier 10, the output of which is connected to the input of the voltage comparator 2, the output of which is connected to the input of the installation “S” of the thyristor switch 11, the output of which is connected to the control input of the recovery pulse generator 13 and the input of the driver 12, which is connected to the input negative pole 5; the first and second outputs of the driver 12 are connected respectively to the gate and source of the power MOS transistor 1, and the output of the recovery pulse generator 13 is connected to the reset input “R” of the thyristor switch 11.

N-channel version of the inventive device in figure 2 ([n-1] channels - "hot" reserve) differs from the single-channel in figure 1 in that additionally introduced [n-1] - resistive current sensors 3 ² , 3 ³ , ... 3 ⁿ , and all sensors (3 ¹ , 3 ² , 3 ³ , ... 3 ⁿ ) are connected in series; contains an OR circuit 15 having n inputs; additionally introduced [n-1] power MOS transistors 1 ² , 1 ³ ... 1 ⁿ , and all power MOS transistors (1 ¹ , 1 ² , 1 ³ ... 1 ⁿ ) are connected in series; introduced [n-1] control channels for power MOS transistors 1 ² , 1 ³ ... 1 ⁿ , for which resistive current sensors 3 ² , 3 ³ , ... 3 ^{n are} connected to the corresponding inputs of differential amplifiers 10 ² , 10 ³ , ... 10 ⁿ the outputs of which are connected to the corresponding inputs of the voltage comparators 2 ² , 2 ³ , ... 2 ⁿ , the outputs of which are connected to the corresponding inputs of the installation "S" of the thyristor switches 11 ² , 11 ³ , ... 11 ⁿ , the outputs of which and the output of the thyristor switch 11 ^{1 are} connected to corresponding inputs of the OR circuit 15 outputs thyristor keys 11 ^2, 11 ^3, ... 11 ⁿ connected with suitable E inputs of drivers 12 ^2, 12 ^3, ... 12 ^n, whose outputs are connected to the sources and gates of the respective power MIS transistor 1 ^2, 1 ^3, ... 1 ^n, the output of OR gate 15 is connected to a control input of the generator of reducing pulse 13, the output of which connected to the combined reset inputs "R" of the thyristor keys 11 ¹ , 11 ² , 11 ³ ... 11 ⁿ . N-protective channels work simultaneously. If any combination of [n-1] channels fails, the protective function is maintained.

The circuit of the inventive electronic fuse with self-healing is made on the basis of a threshold device. The value of the set threshold determines the value of the limiting current during overload or short circuit. load. If the load current exceeds the limiting current, the load is switched off. One of the main parameters — the energy released in the spark gap during a short circuit of the load — is minimized, which is determined by the short time (several microseconds) of the load disconnection and the short-circuit current limitation.

The operation of the claimed device is considered according to the functional diagram in figure 3. The device consists of the following functional units:

8 - auxiliary power supply;

3 - resistive current sensor;

10 - differential amplifier;

9 - short-circuit current limiter (L1, VD1);

2 - voltage comparator (DA1, R1, R2, R3);

11 - thyristor switch (VS1, VT1, VT2, R4, R5, R6, R7);

12 - driver;

1 - power MOS transistor;

13 - controlled generator of regenerating pulses;

14 - start current limiter (VT3, C1, R8, R9).

Reference voltage the non-inverting input of the comparator chip DA1 (node 2) is supplied from a variable resistor R1, the positive feedback voltage is applied to the same input from the output of the comparator via resistor R2, which reduces the response time and eliminates chatter due to hysteresis. The inverting input of the comparator DA1 is external (it receives a signal from the output of the differential amplifier 10).

The matching circuit between the output of the comparator DA1 (node 2) and the control electrode of the thyristor VS1 (node 11) is VT1, R4, R5, R6, the resistor R7 is the anode load of the thyristor, the transistor VT2 performs a shunt function with respect to the turned on thyristor VS1. In the on state, the transistor VT2 shunts the thyristor VS1, and when the transistor VT2 is turned off, the thyristor VS1 will also be in the off state.

Consider the operation of the device in the normal (static) mode, when the load current is less than the limiting current (Iload <Iload). In this case, the voltage at the inverting input of the comparator DA1 (node 2) is less than Uop., The output voltage of the comparator is high, the transistor VT1 (node 11) is turned on, the thyristor VS1 is turned off, the voltage at its anode is high, and the output of driver 12 is low and the power MIS transistor 1 is turned on, the recovery pulse generator 13 is blocked, its output is low and the shunt transistor VT2 (node 11) is turned off.

In case of overload or short circuit (dynamic mode) the load current is greater than the limiting current (Iload> Iload), while the comparator DA1 (node 2) is triggered, the thyristor VS1 (node 11) is turned on, the power MOS transistor 1 is turned off, the current is I load. becomes equal to zero, and the comparator DA1 (node 2) returns to its original state, but the thyristor VS1 (node 11) remains in the on state (“latch”). At the anode of the thyristor VS1 low level and the generator of the regenerating pulses 13 is turned on. Now, to turn off the thyristor, you need to make its anode current less than the holding current. At the output of the regenerating pulse generator 13, when it is turned on, a high-level pulse appears, the transistor VT2 turns on and shunts the thyristor VS1 (node 11), the anode current of which becomes less than the holding current.

Further, the process can develop in two directions. With a short short circuit, when the circuit time is less than the pulse duration at the output of the regenerating pulse generator 13, normal operation will be restored and the thyristor VS1 (node 11) will be in the off state. With prolonged short-circuit at the output of the regenerating pulse generator 13, a sequence of high-level pulses will appear, along the trailing edge of which the thyristor VS1 (node 11) will be off, the power MOS transistor 1 will turn on for a short time. After eliminating the cause of the overload or short circuit normal operation will be restored.

Parameters that determine the operation of the threshold device

- resistance of current sensor 3 Rdatch (Ohm); - gain differential amplifier 10 Piece. (Uout./Uin.); - voltage reference voltage comparator 2 Uoporn. (AT); - current limit during overload or short circuit IGR. (A).

The relationship between the parameters is determined by the formula

Piece. = Uoporn ./ (Rdat. × Iog.).

For example. We set IOGR = 2 A, R sensor = 0.05 Ohm, Uoporn = 0.6 V, then

Piece. = 0.6 / (0.05 × 2) = 6; power allocated to the current sensor 3,

P sensor = I ² og. × R sensor = 4 × 0.05 = 0.2 W.

In the absence of an amplifier or Kus. = 1 R sensor = Uop ./ (Kus. × Iog.) = 0.6 / 1 × 2 = 0.3 Ohm,

P sensor = I ² og. × R sensor = 4 × 0.3 = 1.2 W.

Short-circuit current limiter 9 is made on the inductor L1 and the Schottky diode VD1, limiting the voltage surge on the inductor when the current is suddenly turned off.

The inrush current limiter 14 is made on the field effect transistor VT3. If the load connected to the poles 6, 7 is resistive-capacitive or has a starting current, then when the protected power source is turned on, the inrush of the current in the load may exceed the limiting current and the protection will be triggered. By choosing the time constant of the circuit C1, R9, the internal resistance of the transistor VT3 when the source is turned on will decrease "smoothly" so that the starting current does not exceed the current limiting. Resistor R8 is designed to discharge the capacitor Cl in the gaps between the recovery pulses during a long short-circuit.

The electronic components that come with the device are not scarce. They are commercially available and easy to purchase.

Example. A prototype device was assembled, in the functional units of which are applied:

- high-speed operational amplifier KR544UD2G;

- throttle type SDR1307;

- comparator LM 111;

- MOS transistors IRF7103, IRF4905;

- low-power uncontrolled thyristor KU104 V.

Claims (2)

1. Electronic fuse with self-healing, containing a power MOS transistor operating in the key mode, a voltage comparator, a resistive current sensor, characterized in that it is made in the form of a four-terminal device, to the input poles of which are connected the positive and negative output of the protected power source, and the output the poles - positive and negative are connected to the load, and it includes: auxiliary power supply, short-circuit current limiter, differential amplifier, a source key having a setup input “S” and a reset input “R”, a driver, a controlled recovery pulse generator, a start current limiter, and an auxiliary power input connected to the input poles of a four-terminal network, the output of which is connected to the power inputs: differential amplifier, voltage comparator thyristor switch and a controlled generator of regenerating impulses; connected to the input positive pole is the input of the short-circuit current limiter, the output of which is connected to the source of the power MOS transistor, the drain of which is connected to the input of the start current limiter connected to the output negative pole, the output of the start current limiter is connected to the output positive pole; connected to the input negative pole is the first input of the differential amplifier and the first output of the resistive current sensor, the second output of which is connected to the output negative pole and the second input of the differential amplifier, the output of which is connected to the input of the voltage comparator, the output of which is connected to the installation input "S" of the thyristor switch, the output of which is connected to the control input of the recovery pulse generator and the driver input, which is connected to the input negative pole, the first and second outputs s drivers connected respectively to the gate and source of the power MISFET, and reducing the pulse generator output is connected to the reset input of «R» thyristor key. 2. The electronic fuse according to claim 1, characterized in that it additionally has [n-1] protective channels (“hot” reserve), for which it additionally includes: [n-1] resistive current sensors, all n-sensors current are connected in series; [n-1] power MOS transistors, wherein all n-power MOS transistors are connected in series; OR circuit having n inputs; [n-1] control channels [n-1] power MOS transistors, for which [n-1] resistive current sensors are connected to the corresponding inputs [n-1] of differential amplifiers, the outputs of which are connected to the corresponding inputs [n-1] voltage comparators, the outputs of which are connected to the corresponding inputs of the installation “S” [n-1] of thyristor switches, the outputs of n-thyristor switches are connected: to the n-inputs of the OR circuit and to the corresponding inputs of n-drivers, the outputs of which are connected to the sources and gates of the corresponding n-power MOS transistors; the output of the OR circuit is connected to the control input of the recovery pulse generator, the output of which is connected to the combined reset inputs of the "R" n-thyristor keys.

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