RU2568655C1 - Key element with real-time diagnostic function - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: key element is made as in-series circuit of at least two controlled keys represented by field effect transistors and power supply source. The device comprises pair-wise comparison unit for the controlled keys, which is designed to control and compare voltage drop at open in-series controlled keys.

EFFECT: improved authenticity of the keys control, continuous control is provided.

4 cl, 3 dwg

Description

The invention relates to automation and telemechanics and can be used as a highly reliable switching element with a short switching time, in particular, in systems with safety units for monitoring the health of power controlled keys.

A device is known that contains controlled keys, the outputs of which are connected via actuators to diodes, which also contains a control device, a first switching unit through which common points of controlled keys are connected to the first bus of the power supply, a second switching unit connected in series to the communication circuit of common points executive bodies with a second bus of the power source, and current-setting elements, for example, resistors, connected by one output to the outputs of controlled keys, and by other outputs to the second the power supply bus, the input of the control device is connected in parallel with the first switching unit. The device allows you to check the operability of each of the output stages without disrupting the functioning of the control system in which it is installed. At the same time, the control system itself is indirectly checked (see RF patent 2101748, G05B 23/00, G05B 23/02, 1996).

After turning on the power before the test, all keys in the known device are closed. In this case, the current does not flow through the controlled keys of the device, the actuators are turned off, the circuits of the current-sensing elements are open, the voltage at the input of the fixing device is zero and there is no signal at its output. In this case, the absence of a signal at the output of the locking device indicates the absence of a malfunction of the type of short-circuited key.

To control the controlled keys, it is necessary to form commands to open them one by one and not to send control signals to open the switching units. In this case, current will flow through the corresponding current-collecting element and the open controlled key to the control circuit of the fixing device, which will work for the time the command is issued to the key and turn off after it is removed (while the breakdown of any key of the fixing device will generate an output signal continuously).

Thus, the known device for checking keys requires translating them into test mode, which significantly limits the scope of its application. In particular, its use for monitoring normally closed keys of a security unit is possible only when the unit is turned off during testing. The same circumstance reduces the reliability of the control, since the latter is not carried out continuously, but only periodically, when the safety device is put into test mode.

Closest to the proposed one is a key element of a high-voltage valve converter, into which a resistor block, a signal measuring unit are inserted for diagnostics, and the power switches of the high-voltage valve are divided into two parts, forming a midpoint connected to a common power bus of the signal measuring unit. On the one hand from the midpoint, current-limiting resistors are connected to the first terminals of the power switches of the high-voltage valve, and on the other, to their second terminals. The first conclusions of each of the resistors of the resistor block are connected to a common power supply bus of the signal measuring unit, and their second conclusions are connected respectively to the second conclusions of current-limiting resistors and the inputs of the signal measuring unit, the outputs of which are connected to the inputs of the optical transmitter (see RF Patent 2417498, H02H 7/10 04/05/2010).

In this device, the power switches of the high-voltage valve are closed and an alternating voltage is present on them, which is supplied to the inputs of the signal measuring unit through current-limiting resistors, where it is limited by the resistors of the resistor block, which form the so-called voltage dividers with current-limiting resistors. With a “broken” power key of a high-voltage valve, the voltage is zero. If the power switch of the high-voltage valve is operational, the voltage value is non-zero. The signal measuring unit measures the voltage across the power switches of the high voltage valve connected directly to the midpoint of the high voltage valve. The signal measurement unit determines the voltage value on the remaining power switches of the high-voltage valve through the voltage difference between adjacent voltage dividers, performing in this mode the functions of a comparison unit with a midpoint.

This device can be used to control the keys of safety blocks, but in it the state of power switches is monitored under certain conditions: before and after operation of the converter, when voltage is applied, but the power switches of the high-voltage valve are turned off (or during operation of the converter when the power is off) key). During operation of the converter, the power switches of the high-voltage valve are in the open state, therefore, the mode of monitoring their health and measuring their heating by the claimed device are blocked in this case.

Thus, this device essentially has the same drawback: in the working state, the key is not controlled, its serviceability is monitored only in test mode.

The disadvantages of the known device should also include a limited scope of use - a number of measurements are possible only for blocks containing many identical power keys.

The technical result expected from the use of the invention is to increase the reliability of key control, which is crucial for the keys of security units due to the implementation of continuous monitoring during operation. In addition, the proposed device is applicable for single keys, which is also very important for use in safety units, which, as a rule, have a control key at the output, in a safe state, open and closed only when an emergency occurs.

This result is achieved by the fact that in the key element with real-time diagnostics, made in the form of a serial circuit of at least two monitored keys and a power source and containing a pairwise voltage comparison unit for the monitored keys, the latter is configured to control and compare the voltage drop in open series-connected controlled keys, which are made in the form of field-effect transistors.

In addition, the pairwise voltage comparison unit on the controlled keys can be configured to control the total voltage at the last and / or outputs of the key element.

In this case, the input circuit of the pairwise voltage comparison unit on the controlled switches can be configured to adjust the input current.

And finally, the input circuits of the pairwise voltage comparison unit on the controlled keys can be made in the form of a sampling unit equipped with a sampling regulator that provides the ability to adjust the input current by changing the sampling frequency or the accumulation interval, the input and output of which is connected to the output of the sampling unit and its control the entrance, respectively.

Consider first the simplest implementation of the proposed device, and then explain the possible options.

A schematic diagram of the proposed device is shown in FIG. 1, where indicated:

1, 2, 3 - key management circuits,

4 - power source,

5 - additional field effect transistor (key),

6, 7 - controlled field effect transistors (keys),

8 - load

9, 10 - terminals that are the outputs of the key element,

11 - block pairwise comparison of voltages on the controlled keys with an additional input 12.

The controlled field effect transistors 6 and 7 are connected in series with the transistor 5 and the load 8. The inputs of the block 11 for pairwise comparison of voltages on the controlled keys in this example are connected to the drain and source of each of the field effect transistors 6, 7, made as identical as possible, and block 11 performed with the possibility of pairwise comparison of the input voltages on the public keys 6, 7, for example, in the form of two input differential amplifiers, the outputs of which are connected to the inputs of the comparison circuit, the output of which is swing block 11 pairwise comparison voltages controlled switches.

In FIG. 2 shows an example of a circuit diagram of the input circuit of block 11 for pairwise comparison of voltages on controlled keys, for which the input current is determined by the sampling frequency. In FIG. 2 is indicated: 13 - feedback resistor, 14 - input capacitance, 15 - key, 16 - output integrator.

The input capacitance (input measuring capacitor) 14 is connected through a switch 15 alternating with a frequency F to the measured circuit (i.e., the input of block 11, not shown in Fig. 2) and to the input of the output integrator 16. The input resistance of such an input circuit is determined by the expression R = 1 / (CF), where C is the capacitance of the capacitor 14.

In this case, when measuring voltage drops on the channels of transistors 6 and 7 in FIG. 1 on open channels and high currents, there is practically no influence of the sampling frequency F. Whereas on closed channels, leakage currents become comparable with the input currents of the measuring inputs of block 11, and by changing the sampling frequency F, one can select the input measurement current, which ensures that the voltage at the inputs is in the measured range and thus, in particular, control the leakage of the closed field-effect transistor 5 ( Fig. 1) (i.e., the divider is changed, consisting of the leakage resistance of the upper key element and the parallel resistance of the field keys and the input resistance of the measuring circuit oka 11). This allows you to evaluate with the necessary accuracy the leakage current of the investigated key element (in this case, field-effect transistor 5). The frequency F is changed, for example, by a control processor or microcontroller (not shown in Fig. 1), which controls the operation of block 11 so that the measured voltage drops on the switches 6, 7 in the closed and open state are in the optimal range. The information input of the microcontroller is connected to the output of the integrator 16. The microcontroller measures the output voltage of the integrator 16 and at the same time, by changing the frequency F, ensures that the measured voltage is in the optimal range of characteristics. The closure of the key 15 can be carried out with a constant frequency, and the pulse duration, i.e. the accumulation interval, can be adjusted. The discretization block in this case is formed by a key 15, a capacitor 14, an integrator 16 and a microcontroller.

It should be borne in mind that the implementation of the input circuits of block 11 with the possibility of adjusting the input current can be carried out using a controlled resistive voltage divider. Corresponding voltage dividers are installed at the inputs of block 11 and are controlled by a microcontroller connected in the manner described above and operating according to the above-described algorithm.

However, adjusting the input currents of block 11 using a sampling block is schematically simpler, more reliable, and more efficient.

An ADC or a sampling-storage circuit may be used in the sampling unit. An example of constructing a sampling unit is shown in FIG. 3, which depicts a microcontroller 17 that controls the sampling frequency f _{CLK of the} ADC 18, whose input current is proportional to this frequency due to the use of the charge transfer circuit. For simplicity, an ADC 18 with two differential inputs is shown, as well as a measurement unit 11 in FIG. 1. The control criterion is simple: until the input current i _in exceeds the leakage current of the controlled private key (transistor 5 in Fig. 1) by a sufficient amount described (see earlier) the resistive divider from the resistance of the closed transistor and the input resistance will the measuring circuit supply too much of the supply voltage to the inputs of the measuring circuit? and the ADC 18 will be “off scale” - i.e. give the maximum code on both channels. The task of the microcontroller 17 is to increase the sampling frequency f _CLK until reasonable non-encapsulating codes appear in the channels - with some margin (for example, half a scale or 1/3 of a scale). This solution allows you to use the same measuring circuit to control the identity and, accordingly, the health of open transistors 6, 7, and, after closing them, measure the leakage current of transistor 5 (or, with transistor 5 open, another key in series in this chain).

It must be emphasized that field-effect transistors 6, 7 can relate to one functional unit as well as different ones, in particular, a controlled automatic control system, a control unit, or a safety unit in any combination. The additional field effect transistor 5 can also relate to a control system or a security unit, that is, to a chain of N controlled keys, or to be isolated, providing control and better performance when switching the chain.

In the case when the key element or part of it is a series-connected channels of field-effect transistors, and the safe state is open, the method of monitoring operability is usually a short-time opening of the keys with checking the status of the circuit. At the same time, in many cases, frequent complete shutdown is undesirable (due to the operation of the safety circuits controlled by a key element), and short-term shutdown without triggering of the main systems is difficult. In this case, a normally closed key element in the intervals between outages may be uncontrollable, which is unacceptable for security systems.

So, for example, a complete short circuit of the low-resistance channel of a field-effect transistor due to electrical breakdown or mechanical displacement of the conductors may not be detected due to the fact that the current in the circuit does not change significantly. Meanwhile, this is a very real situation, for example, during power surges or voltage discharges in the surrounding power circuits (including those having a capacitive or inductive constructive connection with the key element circuits). The proposed device allows to eliminate this situation by continuously monitoring the equality or a given proportionality of voltage drops on the channels of both switches 6, 7 (in case of partial breakdown, a significant leakage current may occur that violates this equality), as well as the immunity of the resistance of the channels of both transistors (in case of partial breakdown or full short circuit, this value immediately changes).

The implementation of the block 11 pairwise comparison of voltages on the controlled keys with high-impedance inputs does not allow breakdown at voltages significantly higher than those used in the key circuits.

As already noted, in real-time key monitoring, the fact is used that the open channel resistances of the monitored transistors 6 and 7 are either known, and the measuring circuit, when comparing the voltages, takes into account their ratio or are equal, which, when connected in series, ensures equal voltages. In the simplest case, when the resistances of the keys 6 and 7 (transistor channels) are equal (i.e., the transistors are technologically identical), and block 11 is made in the form of a simple automaton with a logic output, block 11 depending on the module of the difference between the two input voltages and the selected allowable threshold (unbalance) generates, for example, a logical "0" for the difference is less than the threshold and a logical "1" with a more significant imbalance. The latter indicates a malfunction. With the key elements 6, 7 open, this measuring circuit actually controls itself and, in addition, the equality of the leakage currents of the two transistors (6 and 7), which with a positive control result also corresponds to a logical “0” at the output, and if the circuit is unbalanced, to a logical "one".

When block 11 is executed on the basis of, for example, an ADC with multichannel synchronous UVX (UVX or SVX is a device or sampling-storage scheme, respectively, and synchronization of measurements is necessary to compensate for current surges in the load circuit) and the microcontroller, the latter not only compares the voltage in the channels, but, in accordance with the range of measured values, it can also perform tuning of the sampling frequency for the ADC and I / O with a corresponding change in the input currents of the measuring circuits. In this case, the output of block 12 in this case is a digital interface for transmitting more complete diagnostic information about the status of each key according to the measurement results and depending on the operating mode.

It should be noted that when changing the polarity of the power source 4, respectively, semiconductor devices of opposite conductivity are used. If N> 2 field-effect transistors are used in the serial circuit of the power supply 4, load 8, field-effect transistor 5, then with an even number of them, block 11 performs pairwise comparison of voltages, for example, on neighboring field-effect transistors: first and second, third and fourth, etc. d. If N is odd, one of the monitored field effect transistors is used twice during the control: the first with the second and the first with the third, for example, with N = 3.

If block 11 is configured to control the voltage across field-effect transistors 6, 7, then no additional connections are required, but if it is possible to control the total drop across the entire key element, that is, including an additional field-effect transistor 5, terminal 9 is connected to the additional input of block 11.

Block 11 for N> 2 is performed with the ability to compare voltages not only on adjacent switches (field effect transistors), but also on their other pairs, which contributes to a significant increase in the reliability of control and operation of the circuit as a whole. For example, with N = 3, comparing the voltages at pairs 1-2, 2-3 and 1-3, as well as between terminals 9, 10, we are able to not respond to random surges of leakage currents (for example, key 1 in pair 1- 2, if the same throw is not fixed in pair 1-3, etc.).

This solution is intended primarily for use in those safety keys where the load is connected in series and the open state is safe (i.e. the load is de-energized). A feature of this option is that most of the working time the key is in a closed state, and opening it for testing at the right frequency is impossible or undesirable. While all diagnostic measures should be carried out in real time and provide the required high probability of opening the key with the appropriate command to implement the security function. The situation is further complicated by the fact that during operation and in emergency situations, load circuits can be subjected to short-term exposure to high voltages and currents, after which information about the key's operability is most relevant.

The presence of an additional transistor 5, which is not covered by the measurement circuit, as one of the key power elements can solve the problem of independence from an insufficiently high breakdown voltage of the input circuits of the measuring unit 11. In this case, the key is controlled in such a way that the transistor 5 takes on the main problems of the power difference and voltage during switching, and its control occurs only by leakage in the closed state by measuring the sum of the voltage drops on transistors 6 and 7. Then in this circuit the greatest probability s degradation falls on FET 5, which should be selected with a large safety margin and preferably of the types exhibiting namely gradual degradation during impacts, and transistors 6 and 7 are operated in the power saving mode, is controlled by their safety and their guaranteed unlocking security key. Moreover, the degradation process of transistor 5 is controlled by increasing the leakage current in the closed state (with known voltage in the circuit and temperature), which is estimated by the sum of the voltage drop across the channels of the field effect transistors. Closed-circuit voltage distribution during the highest voltage and emergency conditions (lightning strike, hitting the highest power voltage present in the system, etc.), based on which transistor types are selected according to the limit values, is determined by leaks in the circuits and can regulated by the addition of appropriate high voltage resistors.

For field-effect transistors 6 and 7, similar in structure, under the same operating conditions (at the same current and with identical control), the temperature dependence of the channel resistance is manifested equally with high accuracy. An important point is the positive temperature coefficient of resistance for both most silicon structures and copper contact conductors, which causes a corresponding positive feedback on power and facilitates the detection of even initial defects (with increasing temperature, resistance and power increase at a stable current, which additionally increases the temperature). Thus, the recorded voltage difference between the channels or for one channel relative to the other clearly indicates a malfunction: breakdown or degradation of the transistor structure or irregularities in the control circuit. All this makes the proposed solution, with all its simplicity, highly reliable for real-time diagnostics of security keys (as well as other sequential multi-transistor key circuits).

With any other key element (for example, also with a complex circuit) connected in series between the load and our switch, the proposed measurement circuit for closed (locked) field effect transistors of the voltage difference switch allows us to judge their leaks or malfunctions in their control circuit. But now, the sum of all these voltages is no longer equal to the supply voltage and, in turn, indicates the magnitude of the leakage of the closed external key element (since the leakage current passes through the input resistance of the measuring channels in series and is easily measured by the voltage drop across them). Moreover, it can be controlled by either an external key element or any of the field-effect transistors located “above” (if there are a lot of them) - simply by analyzing the sum of the voltages on those closed ones that are included “below” it (and if it is turned on in the middle, then it is possible to judge transistors above and below).

This is done by the same circuit, but here (on open keys, i.e. - closed channels of field-effect transistors), dealing with low leakage currents, we adjust to their measurement in a wide range, changing the sampling frequency F.

Thus, the claimed device allows you to effectively control the working condition of the keys related, as noted above, to the monitored unit, including security, especially in the closed state, that is, the state of high conductivity. But with its help, the key can also be diagnosed by leaks of its elements and in the open state with a low conductivity of the key element.

Claims (4)

1. The key element with real-time diagnostics, made in the form of a serial circuit of at least two monitored keys and a power source and containing a pairwise voltage comparison unit for the monitored keys, characterized in that the latter is configured to control and compare the voltage drop on open series included controlled keys, which are made in the form of field effect transistors. 2. The key element according to claim 1, characterized in that the pairwise voltage comparison unit on the monitored switches is configured to control the total voltage at the last and / or outputs of the key element. 3. The key element according to claim 1, characterized in that the input circuits of the pairwise voltage comparison unit on the monitored switches are configured to adjust the input current. 4. The key element according to claim 3, characterized in that the input circuits of the pairwise voltage comparison unit on the monitored switches are made in the form of a sampling unit equipped with a sampling regulator that allows you to adjust the input current by changing the sampling frequency or the accumulation interval, the input and output of which are connected to the output of the discretization block and its control input, respectively.

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