RU2808784C1 - Method for measuring tripping time of electronic fuse - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: invention can be used in power electronics to improve the reliability of operation and protect power MOSFET transistors in 310 V DC power circuits from short circuit currents. The technical result is achieved by replacing the operating mode of the bistable multivibrator on transistors VT3 and VT4 with the mode of a pulse generator with external synchronization. The gate of transistor VT7 is connected to the gate of transistor VT6, the source of transistor VT7 is connected to the gate of transistor VT4, the drain of transistor VT7 is connected to the common wire. By simulating a short-circuit mode, an oscillatory process with a frequency f occurs in the circuit, the oscillation period of which is equal to twice the shutdown time of the electronic fuse. The oscillation frequency is measured with a multimeter, and the frequency (shutdown time) is adjusted using resistor R12.

EFFECT: improving the reliability of operation and protect power MOSFET transistors in 310 V DC power circuits from short circuit currents.

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Description

The invention relates to electrical engineering and can be used in power electronics to improve the reliability of power MOSFET transistors in 310 V DC power supply circuits.

Known circuit solutions for measuring the transit time of a pulse along a communication line to a load can be divided into modulation and correlation. The accuracy of time measurement by these methods is characterized by the complexity and duration of the preparation and measurement processes, since for their implementation it is necessary to use variable frequency generators, adjustable delay lines, integrators, analog-to-digital converters, etc., which, in turn, affects the reliability of the results obtained . Such methods are often useful in research laboratories and service centers when developing and configuring modules and instrumentation of modern radio and electrical installations, but are completely unsuitable in general industrial conditions of workshops and factory premises.

A method for recording complex signals is known from the prior art [Dedyukhin A. Using special modes of the synchronization circuit and scanning of digital storage oscilloscopes for recording complex signals. // Components and technologies. - 2006. - No. 7. - P. 172-178.] - prototype. The technical result of the proposed method consists in the use of special synchronization modes of digital storage oscilloscopes for recording and recording single fast or slow signals with subsequent processing. Synchronization modes of a digital oscilloscope can be divided into the following types: according to specified conditions - conditional and unconditional; by the number of input channels involved - into connected and unconnected. Let's consider the unconditional mode of linked synchronization “by quality”. This trigger uses two oscilloscope channels, including the external trigger input. In this case, the positive or negative edge of one signal (channel) (for example, a signal from a current sensor in the case of measuring the shutdown time of an electronic fuse) serves as permission to trigger and measure from another signal (channel) (for example, a shutdown control signal to the gate of a power transistor of an electronic fuse). The measured value of the delay time for the control signal to pass through the circuit is the time it takes to turn off the electronic fuse. The practical value of the method of recording complex signals using a digital storage oscilloscope lies in the ability to see, record and measure the signal in real time. Along with the ease of measurement, the method also has a number of disadvantages. The high cost of an oscilloscope with the declared characteristics and operating conditions does not always allow its use in general industrial conditions of enterprises, and significantly increases the cost of commissioning. In addition, setting the shutdown time of the electronic fuse using the proposed method requires a fairly long period of preparation of the measurement cycle due to a single passage of the pulse through the feedback circuit and a period of equipment downtime, as well as an increase in statistical error with a fairly small number of measurements.

The objective of the present invention is to develop a method for measuring the tripping time of an electronic fuse to protect power MOSFET transistors in 310 V DC power supply circuits from short circuit currents.

The technical result consists in reducing the statistical measurement error of the operating mode of a bistable multivibrator.

The technical result is achieved by replacing the operating mode of the bistable multivibrator as part of the electronic fuse proposed by the authors [Levchenko A.A., Borisenko D.N., Zhokhov A.A. Device for protecting DC power circuits from short circuits. // RF Patent No. 2778553 dated January 20, 2022, Bull. No. 24], on transistors VT3 and VT4 (Fig. 1) to the pulse generator mode with external synchronization by connecting the p-channel MOSFET transistor VT7 to points 5-6: the gate of transistor VT7 is connected to the gate of transistor VT6 (point 5 in Fig. 1 and Fig. 2), the source of transistor VT7 is connected to the gate of transistor VT4 (point 6 in Fig. 1 and Fig. 2), the drain of transistor VT7 is connected to the common wire. By simulating a short circuit mode, an oscillatory process with a frequency f occurs in the circuit, the oscillation period of which is will be equal to twice the tripping time of the electronic fuse The oscillation frequency is measured with a multimeter connected to points 1-2 of the circuit (Fig. 2), the frequency (off time) is adjusted using resistor R12.

Example. The signal from the current sensor RS (Fig. 1) points 3-4 is supplied to the operational amplifier DA2, connected according to an “inverting amplifier” circuit with negative feedback. The threshold value of the inverting input of the comparator DA1 is adjusted using resistor R12 through the value of the reference voltage. To reduce the output signal bounce, the comparator is equipped with positive feedback; the hysteresis value is adjusted by resistor R7. The signal from the comparator DA1 is applied to the gate of transistor VT6, which controls the operation of a bistable multivibrator on transistors VT3 and VT4. Changing the operating mode of the bistable multivibrator to the pulse generator mode with external synchronization is done by connecting the p-channel MOSFET transistor VT7 to points 5-6 in this way, that the gate of transistor VT7 is connected to the gate of transistor VT6 (point 5 in Fig. 1 and Fig. 2), the source of transistor VT7 is connected to the gate of transistor VT4 (point 6 in Fig. 1 and Fig. 2), the drain of transistor VT7 is connected to the common wire . By simulating a short circuit mode, an oscillatory process with a frequency f occurs in the circuit, the oscillation period of which is will be equal to twice the tripping time of the electronic fuse The oscillation frequency was measured with a VC99 digital multimeter, the probes of which were connected to points 1-2 of the circuit (Fig. 2), and the frequency (off time) was adjusted using resistor R12. As a result of direct measurements with a VC99 digital multimeter, it was determined that the response time of the electronic fuse shown in FIG. 1, can be varied in the interval of 2.5 μs, which agrees well with the data obtained from the oscillograms of the control pulses on the VT5 gate at points 1-2 shown in Fig. 3, where t1 is the time during which transistor VT5 opens completely when a voltage of 14 V is applied to it by transistor VT2 and the current in the 310 V circuit reaches the set threshold value; t2 is the time during which a current of the set threshold value flows in the 310 V circuit, and at the same time a control signal is generated in the electronic fuse to turn off transistor VT5 via the feedback circuit RS-DA2-DA1-VT6-VT8-VT5; t3 is the duration of transient processes in transistor VT5.

Claims (1)

A method for measuring the shutdown time of an electronic fuse, which consists in determining the time of passage of a pulse through the feedback circuit, characterized in that it simulates a short circuit in an electronic fuse circuit containing a series-connected power MOSFET transistor and a current sensor connected to the DC power circuit, the signal from which supplied to an operational amplifier, the output of which is connected to the input of the comparator, the signal from the output of which is supplied to the synchronization input of the pulse generator with external synchronization, at the output of which a control signal is generated to turn off the power MOSFET transistor, the pulse repetition rate f is measured with a digital multimeter connected to the transition gate-source power MOSFET transistor, the shutdown time of the electronic fuse is calculated using the formula

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