SU1193609A1 - Apparatus for detecting and localizing short-circuits in electron units - Google Patents

Abstract

1. DEVICE FOR DETECTION AND LOCALIZATION OF SHORT CIRCUITS IN ELECTRONIC BLOCKS, containing a step-changing current sensor, a series-connected generator and pulse distributor, characterized in that, in order to increase the reliability and ensure directional search of a short-circuit location, detectors are inserted into it / detector. -comparator, trigger, match block, Current pulse shaper, logic zero comparator, the output of which is connected to the first input of the match block, the first and second outputs of which are connected to the outputs of the device, the first output of the pulse distributor through the current pulse shaper is connected to the input of the comparator logic zero and probing the output of the device, the second output of the pulse distributor is connected 9 to the second input of the coincidence unit, the third and fourth inputs of which are connected respectively to the forward and inverse outputs of the trigger , the reset input of which is connected to the input of the pulse distributor, and the installation input is through a detector-comparator with a sensor, the stepwise change of the CO OO) current . about f

Description

2. The device according to claim 1, which means that the block of coincidence contains three elements And, the outputs of the first and second elements And are connected to the first and second outputs of the block of coincidence, the first and second inputs of which through the third element And are connected to the first inputs of the first and second elements And, the second inputs of which are connected to the third and fourth inputs of the coincidence unit, respectively.

.3, The device according to claim 1, about tl and - since the coincidence unit contains two elements AND, two elements OR, two frequency dividers, the outputs of which are connected to the first and second outputs of the coincidence unit, the counting inputs of the frequency dividers are connected with the outputs of the first and second elements AND, the first inputs of which are connected to the first input of the coincidence unit, the second input of which is connected to the inverse inputs of the first and second elements OR, the outputs of which are connected respectively to the reset inputs of the first and second frequency dividers, the second inputs of the first and second elements OR are connected respectively to the outputs of the second and first elements AND, the second inputs of which are connected to the third and fourth inputs of the coincidence unit, respectively.

4. The device according to claim 1, characterized in that the current pulse driver is made on a transistor, the base of which is connected via a capacitor to the input of the current pulse former, the output of which is connected via a variable resistor to the collector of the transistor, the base of which is connected to the power bus and the emitter transistor.

one

The invention relates to digital and pulse technology and is intended for use in systems for monitoring and diagnostics of logic blocks.

The purpose of the invention is to increase the reliability due to the possibility of unambiguous detection of the fact of a short circuit in the output circuit of the microcircuit and ensuring directional search of the short circuit location.

In FIG. 1 shows a diagram of the device; in fig. 2 is a schematic of a match block, embodiments; in fig. 3 is a diagram of a current pulse driver; in fig. 4 is a schematic diagram explaining how to use the device; in fig. 5 is a timing diagram of the operation of the device, the coincidence unit of which is configured in FIG. 2a; Fig. 6 is a timing diagram of the operation of the device, the coincidence unit in which is made in Fig. 2S.

The device contains a generator 1, the first output 2 of the distributor 3 pulses, the driver 4 current pulses, the comparator 5 logical zero, the first input 6 of the coincidence unit 7, the second output 8 of the distributor of 3 pulses, the second input 9 of the coincidence unit 7, the direct output 10 of the trigger 11 sensor 12 stepwise, variable current, detector-comparator 13, trigger reset input 14 11, third input 15 of coincidence unit 7, trigger installation input 16, fourth input 17 of coincidence unit 7, inverse output 18 of trigger II, first output 19 of the device, second output of the device 2QJondi ruby output 21 of the device; The output of the sensor 12 is a stepwise varying current connected to the input of the detector-comparator 1 3, the input of which is connected to the input I6 of the trigger 11, the input 14 of the reset of which is connected to the input distribution-. the pulse body 3 and the output of the generator 1, the output 2 of the distributor 3 and pulses are connected to the input of the current pulse driver 4, the output of which is connected to the input of the comparator 5 logical zero and the probe output 21 of the device, the output of the comparator 5 is connected to input 6 of the coincidence unit 7, input 9 of which connected to the outlet 8 of the distributor 3 im3

pulses, inputs 15 and 17 of block 7 coincidence are connected respectively with outputs 10 and 18 of trigger P.

Block 7 matches (Fig. 2a) contains the first element And 22, the second element And 23, the third element And 24, The output of the third element And 24 is connected to the first inputs of the first and second elements. And 22 and 23, the second inputs of which are connected respectively to the third and the fourth inputs of block 7 are matches.

, Block 7 of the match, shown in figure 2b, contains the first element And 22, the second element And 23, the first element OR 25, the second element OR 26, the counting input 27 of the first frequency divider 28, the counting input 29 of the second frequency divider 30, input 31 resets the first frequency divider 28, the input 32 resets the second frequency divider 30. The outputs of the elements And 22 and 23 are connected, respectively. input 27 and 29 frequency dividers 28 and 30, inputs 31 and 32. reset which are connected respectively to the outputs of the elements OR 25 and 26, the inverse inputs of which are connected to the first input of the coincidence unit 7, the second and third inputs of which are connected to the inputs of the first And 22, the second input of AND 23 is connected to the fourth input of the coincidence unit, and the first input is connected to the first input of the first element And 22.

The current pulse shaper (g. Contains a transistor 33, a capacitor 34, a variable resistor 35, and a resistor 36.

Sensor 12 of stepwise varying current can be made, for example, in the form of a coil with a U-shaped ferrite core, near the gap of which the conductor under study is placed. The sensor converts the current drops in this conductor into voltage pulses at the terminals of the coil of positive or negative polarity. The magnitude and polarity of these pulses depends both on the magnitude and steepness of the current drops in the conductor and on the polarity of these jumps and on the orientation of the sensor 12 in steps of the current relative to the direction of the current in the conductor under study.

The numbering of the diagrams in FIGS. 5 and 6 corresponds to the numbers of the elements in FIGS. 1 and 2.

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Let us assume that the test block is made on TTL circuits (although this is also true for IC of other technologies}.

5 A 4-pulse current driver converts a constant signal or a positive differential at the input to the Open circuit, and a negative differential at the input to a positive sawtooth voltage pulse with a steep leading edge and a gentle falling front. When a logical unit at the input capacitor 34 (fig.Z) transistor 33 is locked and the output

5 slots 4 current pulses When a logical zero appears on the rarefied input capacitor 34 at the base of transistor 33, a low potential appears and the transistor 33 opens. A positive potential appears at the output of the current driver 4. The capacitor 34 begins to charge exponentially with a current through a resistor

5, the transistor 33 starts locking up, forming the rear flat front of the Pulse. The appearance of logical unity does not unlock the transistor 33, the capacitor 34 is discharged. The slope of the falling edge is determined by the values of capacitance of the capacitor 34 and the constant resistance of the resistor 36. This pulse does not change the state of the logical unit at the test-point. The unit, to which the zone-output output 2I of the device is connected, and in the case of a logical zero, a current of a sawtooth shape, the value of which op {) is changing in value of variable resistor 35, will flow into this point 1.

A comparator detector 13, which can be executed, for example, on a K554SAZ microcircuit, generates a signal only if a positive polarity signal arrived at its input, the value of which is above a certain threshold. The value of this threshold is chosen such that the detector

0, the comparator 13 does not extract the signal from the sensor 12 by stepwise varying current at a flat front of the current pulse in the studied conductor from the driver 4 current pulses. Due to this form of current probe pulse, the presence of a signal at the output of the detector-comparator 13 at the moment a current pulse passes through the conductor means that there is a certain direction in the current conductor (with a corresponding orientation of the sensor 12, the current varies in the test wire jt. The absence of Sigals at the detector-comp-13 output at the time of the passage of the probe pulse means that the current pulse of the current pulse is not or no current impulse at all, we describe in general the method of detecting and localizing short circuits implemented in the proposed device Figure 4 shows an uncorroded output circuit of the valve 37 and the path of the current probe pulse from the probe output 21 devices (labeled 38) to the oi-open valve 37 output. Sensor 12 of step-changing current is labeled 39. The internal components of the test block are switched by stimulating signals that can either from the test facility, or are operational signals from a system of which the test block is a part. A short circuit at the output of the ventil 37 (Figs. 45 and c) appears only when this valve 37 is set to the closed state (logical unit) when the other valve 41 shorted to it is in the open state (logical zero). In this case, the probe current pulse from the former 4 current pulse generator, when the probe output device 21 is connected to any point of the output circuit of the valve 37, will pass to the output of the valve 41. To detect a short circuit, it is necessary to install the sensor 12 with stepwise variable current directly to the output (output microcircuits) investigated for short circuit of the valve 37 and orienting the sensor so that the 13 13 comparato detector can react to the current pulse flowing into the probe 37 of the probe 37 Connect the probe output 25 of the device to any point of the output circuit of the valve 37. The absence of a probe current pulse passing through the chip on the chip corresponding to the output of the valve 37, with a logical zero in this output circuit, indicates the presence of a short circuit (Fig. 4B). In order to localize the short circuit location, it is necessary to install the probe output 21 of the device directly onto the chip output, corresponding to the output of the valve 37, to the output circuit of which a short circuit has been detected. By examining the output circuit of the valve 37 with a sensor 12 of stepwise varying current, they determine the portion of the output circuit of the valve 37 through which the probe current pulses flow. This area is enclosed between the outlet of the valve 37 and the point of short circuit (point 40, fig.4b). Sensor 12 of step-changing current must be oriented so that detector detector 13 can react to current probing pulses flowing through a conductor. Consider the operation of the device when the coincidence unit 7 is implemented according to the scheme shown in Fig. 2a. In this case, the tested unit must be synchronized with the operation of generator 1, i.e. moments of possible change of signals in the tested block should coincide with generator I pulses (diagrams, figure 5). This option is mainly used when debugging blocks on test setups, when it is easy to synchronize, initiating the next test set with a pulse from generator 1. At the first output 2 of the pulse distributor 3, a negative pulse delayed with respect to the positive generator pulse I appears. This pulse arrives at the input of the former 4 current pulses, at the output of which a sawtooth pulse appears. The diagrams in figure 5 correspond to the situation depicted in figure 46, and the solid lines correspond to the presence of a short circuit, and the dotted lines correspond to its absence. A short circuit somewhat raises the level of the logic nud of the valve 37. At the output of the sensor 12, step-wise current from each differential current in the output circuit of the valve 37 appears positive and negative pulses.

7

(including from the leading edges of current probe pulses). From each positive pulse exceeding a certain threshold, entering the input of the detector-compressor 13, the latter impulses a pulse that sets trigger one 11, previously reset by generator 1 pulses. Since the back edge of the generator 1 impulse arrives, the trigger input 11 later than the pulse received at the input 16 of the trigger setup 11 from the detector-comparator 13

when switching the logical signals of the test unit, the trigger 11 to the moment of appearance of a pulse at the first output 2 of the distributor 3 pulses remains in the reset state and reacts only to the occurrence of current probing pulses

At a logical zero at the probe output 21 of the device, the comparator 5 of the logical zero gives the unit that goes to the first input; element And 24, and a positive pulse at the second output 8 of the distributor 3 pulses, shifted relative to the pulse at the first 1 output 2 of the distributor 3 pulses, is fed to the first inputs of the elements And 22. and 2.3.

When one is in trigger 11, this pulse passes to the first output 19 of the device, to the infection the presence of probing pulses passes to the expected direction, and when zero to the trigger 1 1. the pulse passes to the second output 20 of the device indicating the absence of passage of probing current pulses of the expected direction.

In the absence of a short circuit, the pulses appear only on the first output 19 of the device, and if there is a short circuit in the output circuit of the valve 37, the pulses will also be on the second output 20 of the device.

To find the location of a short circuit, the situation depicted in FIG. 4B is established, and when sensor 12 is installed, the step-changing current outside the section from the outlet of the valve 37 to the topologically first point of the outlet of the valve 37 is short-circuit 40, the pulses will be only on the second output 20 of the device , and when installing the sensor 12 stu36098

If foam current is changed from the outlet of the valve 37 to the point 40, the pulses will also be on the first outlet 19 of the device.

Consider the operation of the device when the coincidence block is executed in the diagram of Figure 2B. In this case, the operation of the generator 1 is not synchronized with the operation of the test block (diagrams of Figure 6). This option is intended for debugging blocks as part of running systems. For this, it is necessary to take quick measures so that the pulses of the detector-comparator 13,

5, which are disconnected from the switching of working currents and appearing anywhere in the timing diagram, did not affect the analysis of the passage of current probe pulses,

0 The oscillator frequency I should more than triple the switching frequency of the signals in the unit under test. The division coefficients of the first 28 and second 30 frequency divider block

5 7 matches are three. In this case, after a reset or zero state, a positive signal at the outputs of the dividers appears on the arrival of two pulses at their countable inputs, and

When the third pulse arrives, the dividers go to the zero state. The difference in the operation of this variant from the previous one consists only in the work of block 7 of coincidence. The logical unit at the output of the comparator 5 logical zero arrives at the inverse first inputs of the first element OR 25 and the second element OR 26 and allows the operation of block 7

1 match, remove the reset signal from the first 28 and second 30 frequency dividers. With a logical unit on the probe output 21 of the device, a zero appears at the output of the comparator 5 of the logical r zero, which through the first element OR 25 and the second element. OR 26 resets the first 28 and second 30 frequency dividers and keeps them in the zero state.

A positive pulse at the second output 8 of the distributor 3 pulses goes to the first inputs of the first 22 and second 23 elements AND, At the unit in trigger 11, this pulse goes through the first element AND 22 to the digital input of the first frequency divider 28 and through the second element OR 26 to the reset input the second frequency divider 30, which is set to

a zero state, and at the output of the first splitter of 28 ca. after the arrival of the second pulse, a single signal appears at its counting input indicating the presence of current probes in the probing conductor of the probing pulses. At zero in trigger 11, a pulse from the second output 8 of the distributor 3 pulses through the second element I 23 passes to the counting input of the second frequency divider 30 and through the first element OR 25 resets the first frequency divider 28. At the output of the second frequency divider 30 after arrival A second sig- nal appears on its counting input, indicating the absence of probing, current pulses of the expected direction.

Thus, for the appearance of a single signal at the outputs of the device, it is necessary that by the time of the appearance of pulses at the second output of 8 spr, the puller of 3 pulses, the trigger 11 is in the same state at least twice a second. If at one time the trigger 11 has been set to one

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switching operating currents at the point of connection of the probe output device 21, the first pulse that passed through the first element 22 And

5 from the second output 8 of the distributor 3 pulses will not cause the appearance of a single signal at the output of the first frequency divider 28.

If in the next cycle the trigger I1 remains in the zero state (no current probing pulses pass through the expected direction), then the pulse from the second output 8 of the distributor 3 im

15 pulses will reset the first frequency divider 28 to the zero state and a single signal will not be output at its output. If the trigger 11 is also set to one in this clock cycle

20 (already from the passage of current probe pulses), then at the output of the first frequency divider 28 there is a single signal that correctly indicates the passage of the probe pulse.

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Claims (4)

1. DEVICE FOR DETECTING AND LOCALIZING SHORT CIRCUITS IN ELECTRONIC UNITS, containing a step-by-step current sensor, serially connected generator and pulse distributor, characterized in that, to provide directional search for a short circuit location, a detector-comparator, trigger, and matching unit are introduced into it , current pulse shaper, logical zero comparator, the output of which is connected to the first input of the coincidence unit, the first and second outputs of which are connected to the outputs of the device, the first output A pulse distributor is connected to the input of a logic zero comparator and a probe output of the device through a current pulse generator, the second output of the pulse distributor is connected to the second input of the coincidence unit, the third and fourth inputs of which are connected respectively to the direct and inverse outputs of the trigger, the reset input of which is connected to the input of the distributor pulses, and the installation input through a detector — a comparator with a sensor, stepwise changing — in order to increase the reliability and current. Figure 1 1 193609 2. The device according to claim 1, characterized in that the coincidence unit contains three AND elements, the outputs of the first and second elements AND are connected to the first and second outputs of the coincidence unit, the first and second inputs of which are connected through the third AND element to the first inputs of the first and second second And elements, the second inputs of which are connected to the third and fourth inputs of the coincidence block, respectively. . 3. The device according to claim 1, wherein the coincidence unit contains two AND elements, two OR elements, two frequency dividers, the outputs of which are connected to the first and second outputs of the coincidence unit, the counting inputs of the frequency dividers are connected respectively to the outputs the first and second elements AND, the first inputs of which are connected to the first input of the coincidence unit, the second input of which is connected to the inverse inputs of the first and second elements OR, the outputs of which are connected respectively to the reset inputs of the first and second frequency dividers, second e inputs of the first and second elements OR are connected respectively to the outputs of the second and first elements AND, the second inputs of which are connected to the third and fourth inputs of the matching unit, respectively. 4. The device according to claim 1, wherein the current pulse generator is made on a transistor, the base of which is connected via a capacitor to the input of the current pulse generator, the output of which is connected through a variable resistor to the collector of the transistor, the base of which is connected through a resistor with power bus and transistor emitter.