RU2234805C2 - Pulse generator - Google Patents

Abstract

FIELD: radio engineering; nondestructive inspections.

SUBSTANCE: proposed generator designed to produce positive and negative pulses at repetition frequency of 4 and 8 Hz with output signal voltage of minimum 1000 V at load current of minimum 100 mA has supply mains filter 1, autotransformer 2, isolating transformer 3, bridge rectifiers 4, 5 forming dc voltage supply, as well as verifying measurement unit 6 incorporating current sensor, unit of switching components built around transistors connected into bridge circuit, four-channel amplifier 8, optically-coupled isolator 9 for control circuits of unit 7, low-current power supply 10 for internal circuits, power converter 11 for feeding control circuits, transistor current check comparator 12 incorporated in unit 7, and pulse shaping counter assembled of master oscillator 13, follower 14, dividing counter 15, dividing flip-flops 16,17, control-signal shaping counter 18, and external load 19 with dummy load 20.

EFFECT: enhanced output signal voltage and load current.

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Description

The present invention relates to radio engineering and can be used in the technique of non-destructive testing. In particular, when diagnosing dielectric pipelines through which a layer of a weakly conducting liquid flows, it is necessary to apply a voltage exceeding 1000 V to this layer and provide a current of at least 100 mA; while the frequency of the alternating signal should be in the range of 4-8 Hz. Existing industrial generators do not allow such a high voltage at low frequencies. In addition, the generator must be portable enough to support field work.

To implement non-destructive testing, instead of a low-frequency alternating current generator, a generator can be used that creates a sequence of alternating positive and negative pulses, for example, a generator according to AS No. 1008880. However, this generator does not allow to create a high voltage of about 1000 V at the output at a current of about 100 mA with a pulse repetition rate of 4 or 8 Hz.

The closest technical solution to the invention is a 20 hertz ring generator according to US patent No. 5307407, using low-frequency control of the pulse width. This generator allows at a frequency of 20 Hz to realize the conversion of direct voltage from a source with a voltage of +/- 130 V into an alternating signal. The pulse generator contains a constant voltage source, a block of switching elements on transistors, an optocoupler isolation of control circuits, the output of which is connected to the input of the amplifier, the output of which is connected to the input of the block of switching elements on transistors. However, the generator according to the specified patent does not allow to realize an output voltage of the order of 1000 V at a frequency of 4 Hz or 8 Hz and to provide a load in excess of 100 mA in the load.

The objective of the invention is the ability to create using the generator a set of positive and negative pulses with a repetition rate of 4 and 8 Hz, with an output signal of at least 1000 V and a current in the load of at least 100 mA.

The problem is achieved in that the pulse generator containing a constant voltage source, a block of switching elements on transistors, optocoupler isolation of control circuits of a block of switching elements on transistors, the output of which is connected to the input of an amplifier, the output of which is connected to the input of a block of switching elements on transistors, that the block of switching elements on the transistors is made on transistors connected in a bridge circuit with a load in the diagonal of the bridge, and also a counter-form Two output signals consisting of phase-shifted control pulses, the output of which is connected to the optocoupler input of the control circuits, while the output of the DC voltage source is connected to the block of switching elements on the transistors through a control measurement unit, including a current sensor, a current control comparator of the switching unit elements on transistors, configured to lock the counter-pulse shaper when exceeding the permissible current value in the block switching element s on transistors and with the possibility of a complete reset of the counter-pulse shaper when you turn on the DC voltage source.

In addition, the pulse generator is characterized in that it is configured to alternately generate pulses of positive and negative polarity with a voltage of 800 to 1200 V at a frequency of 4 Hz or 8 Hz at a current of at least 100 mA.

The structural diagram of the generator is shown in figure 1, where 1 is a line filter containing a switch, fuses, an RF interference filter, a pulse noise limiter; 2 - autotransformer with a biscuit switch that controls the output voltage; 3 - isolation transformer with two identical output windings; 4, 5 - bridge rectifiers with voltage-smoothing capacitors; 6 - block control measurements, including a voltage divider, a current sensor, a switch of the kind of measurements with the conclusion to the dial indicator of current and voltage readings; 7 - a block of four switching bipolar transistors connected in a bridge circuit; 8 - a four-channel amplifier for matching with bipolar transistors of block 7 (three inverters in parallel and a transistor to keep the transistors closed (for each channel); 9 - optocoupler isolation of control circuits block of switching transistors: two channels for a “hot pair” of transistors of block 7 (“hot pair” - transistors that are under high voltage); 10 - low-current power source of internal circuits (creating a constant voltage 9 V); 11 - power converter of the control circuits of the “hot pair” of transistors of block 7 (operating frequency 32768 Hz); 12 - comparator for monitoring the current of transistors in block 7, which trips when the permissible current value in the circuit is exceeded: “rectifiers - block 7 - load ”(as a result of operation, it locks the counter 18 in the zero state, in addition, it is possible to disable the comparator, the meters are also completely reset when the power is turned on, comparator 12 also has an external indicator of operation); 13 - master oscillator with a frequency of 32768 Hz; the frequency is stabilized by a quartz resonator in a standard watch design; 14 - repeater, eliminating the influence of external factors on the operation of the master oscillator; 15 - counter-divider with a coefficient of 2 ⁸ = 256, forming a frequency of 32768/256 = 128 Hz; 16 - trigger divider by 2, allowing together with block 17 to choose the frequency of the output signal 4 or 8 Hz; 17 - trigger divider 2, allowing together with block 16 to select the frequency of the output signal 4 or 8 Hz; 18 is a counter-driver of control signals of bipolar transistors in block 7; this node generates two output signals, out of phase with a duty cycle of 3/8; the counter has a division ratio of eight; 19 - external load; 20 - load equivalent (used in tests or in case load parameters 19 are unknown or unpredictable). Blocks 1, 2, 3, 4, 5 form a constant voltage source. Blocks 13-18 are part of the counter-pulse generator.

Figure 2 shows a pulse diagram at the output of block 18 and the output of block 7.

The generator operates as follows. As a result of the operation of blocks 1, 2, 3, 4, 5, a constant high voltage is generated at the output of blocks 4 and 5, which is actually adjustable from 800 to 1200 V. From the outputs of the rectifiers, a high voltage is supplied to the input of the block of switching transistors 7 through the block of control measurements 6. The operation of block 7 is controlled by a four-channel amplifier 8. Block 9 implements optocoupler isolation of the control circuits of the transistors of block 7 in two channels. At the inputs of blocks 8 and 9, rectangular pulses are fed at an operating frequency of 4 Hz or 8 Hz, phase shifted relative to each other and having a duty cycle of 3/8. These pulses are generated by block 18 by sequentially dividing the pulses of the master oscillator 13, the counter of the divider 15, and triggers 16 and 17. As a result, pulses of positive and negative polarity are alternately generated at the output of block 7, which are supplied to the external load 19 directly or through the load equivalent 20 .

Figure 2 shows diagrams explaining the operation of the generator. Low-voltage control pulses from the output of block 18 act through an amplifier 8 on block 7, so that high-voltage pulses of alternating positive and negative polarity with intervals between them equal to 1/8 of the period are formed at its output.

Claims (2)

1. A pulse generator comprising a constant voltage source, a block of switching elements on transistors, optocoupler isolation of control circuits of a block of switching elements on transistors, the output of which is connected to an input of an amplifier, the output of which is connected to an input of a block of switching elements on transistors, characterized in that the block of switching elements on transistors are made on transistors connected in a bridge circuit with a load in the diagonal of the bridge, and a counter-former of two output signals, of phase-shifted control pulses, the output of which is connected to the input of the optocoupler isolation of the control circuits, while the output of the DC voltage source is connected to the block of switching elements on the transistors through the control measurement unit, including a current sensor, a current control comparator of the block of switching elements on the transistors, made with the possibility of locking the counter-pulse shaper when exceeding the permissible current value in the block of switching elements on transistors and with the possibility of lnogo reset pulse shaper-meter when the DC voltage source. 2. The pulse generator according to claim 1, characterized in that it is configured to alternately generate pulses of positive and negative polarity with a voltage of from 800 to 1200 V at a frequency of 4 or 8 Hz at a current of at least 100 mA.

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