CN117368798A - Fault detection circuit and related circuitry - Google Patents
Fault detection circuit and related circuitry Download PDFInfo
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/52—Testing for short-circuits, leakage current or ground faults
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
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Abstract
The present disclosure provides a fault detection circuit and related detection circuitry. The fault detection circuit includes: a channel unit configured to supply a drive signal to a load via a switching element, the channel unit comprising the following components connected in series in order: a parallel combination of a sampling resistor, the switching element, and a bypass resistor, and a diode, wherein a negative terminal of the diode is connected to a load; a disconnection detecting unit configured to determine whether the load is disconnected via a first voltage across the sampling resistor, regardless of whether the switching element is turned on; and a short-circuit diagnosis unit configured to determine whether the load is shorted via a second voltage of a node between the parallel combination and the diode, regardless of whether the switching element is turned on.
Description
Technical Field
The present disclosure relates to fault detection circuits, and more particularly to a fault detection circuit for short circuit and wire break detection and related circuitry.
Background
The digital quantity output system is widely used in a Programmable Logic Controller (PLC) and a Distributed Control System (DCS). The traditional digital quantity output system is incomplete in diagnosis in application, cannot be effectively positioned when faults occur, and is easy to cause long-time disease-carrying work, so that faults are diffused.
In summary, when a load breaks and/or short-circuit faults occur, effective diagnosis, alarm and protection cannot be performed.
Disclosure of Invention
It is an object of the present disclosure to provide an improved fault detection circuit which is adapted to perform both wire break and short circuit detection simultaneously and which allows for an efficient diagnosis.
According to a first aspect of the present disclosure, a fault detection circuit is provided. The fault detection circuit includes: a channel unit configured to supply a drive signal to a load via a switching element, the channel unit comprising the following components connected in series in order: a parallel combination of a sampling resistor, the switching element, and a bypass resistor, and a diode, wherein a negative terminal of the diode is connected to a load; a disconnection detecting unit configured to determine whether the load is disconnected via a first voltage across the sampling resistor, regardless of whether the switching element is turned on; and a short-circuit diagnosis unit configured to determine whether the load is shorted via a second voltage of a node between the parallel combination and the diode, regardless of whether the switching element is turned on.
It will be appreciated that by using the fault detection circuit of the present disclosure, the detection of the disconnection and short circuit of the load of the switching element in the ON and OFF states can be effectively realized, and the diagnostic scheme has wide applicability, and the problem that the intermittent pulse detection scheme in the prior art is difficult to match with the capacitive load and the inductive load is solved. In addition, when short circuit occurs, the fault detection circuit can also respond rapidly to the switching of the closed channel to detection in an OFF state, so that the system is effectively protected. In addition, the scheme of the present disclosure can be realized by adopting conventional components and parts, and is easy to popularize.
In some embodiments, the disconnection detecting unit may include an amplifier circuit adapted to amplify the first voltage and output a disconnection detecting signal via a first isolation circuit, and the first isolation circuit may be connected in series.
In some embodiments, the amplifier circuit is a differential amplifier circuit, a positive input of an operational amplifier in the differential amplifier circuit is connected to one end of the sampling resistor via a first resistor, a negative input of the operational amplifier is connected to the other end of the sampling resistor via a second resistor, a positive input of the operational amplifier is also connected to ground via a third resistor, and an output of the operational amplifier is connected to the negative input via a feedback path including a fourth resistor.
In some embodiments, the differential amplifier circuit has a magnification of at least 1500 times, and the third resistor has a resistance value of not more than 1mΩ.
In some embodiments, the first resistor and the second resistor have the same resistance, and the third resistor and the fourth resistor have the same resistance.
In some embodiments, the amplifier circuit is connected to the first isolation circuit via a current limiting resistor having a resistance on the order of kiloohms.
In some embodiments, the short circuit diagnosis unit may include a comparison circuit and a second isolation circuit connected in series, the comparison circuit configured to receive the second voltage and output a short circuit detection signal via the second isolation circuit.
In some embodiments, the comparison circuit may include a comparator having a positive input connected to the node, thereby causing the short circuit diagnosis unit to implement short circuit detection in a positive logic manner.
In some embodiments, the comparison circuit may include a comparator or an operational amplifier, a negative input of which is connected to the node, thereby causing the short circuit diagnosis unit to implement short circuit detection in a negative logic manner.
In some embodiments, the comparison circuit may further include a reference circuit for providing a reference voltage to the comparator or operational amplifier, the reference voltage being set based on a voltage drop of the diode under a load short.
In some embodiments, the fault detection circuit may further include: an output control unit comprising a third isolation circuit, the output control unit being adapted to provide a switching control signal to the switching element via the third isolation circuit.
In some embodiments, the switching element is a MOS transistor, bipolar transistor, or other type of switching element.
In some embodiments, the resistance of the sampling resistor is an ohm-level resistor and the resistance of the bypass resistor is a 10K ohm-level resistor.
In some embodiments, the disconnection detection is performed in a polling or triggering manner, and the short circuit detection is performed in a triggering manner.
According to a second aspect of the present disclosure, a circuit system is provided. The circuitry may include the aforementioned fault detection circuit; an output control unit configured to generate a switching control signal that controls a switching element in the failure detection circuit; and a processor configured to output a control instruction to cause the output control unit to generate the switch control signal.
In some embodiments, the processor is further configured to: outputting a control instruction to put the switching element in an off state in response to receiving a short-circuit diagnosis signal indicating that the load is short-circuited; and outputting a control instruction to cause the switching element to switch from the off state to the on state in response to receiving the short circuit diagnosis signal when the short circuit diagnosis signal is shifted from short circuit to normal.
It should also be appreciated that the descriptions in this summary are not intended to limit key or critical features of embodiments of the disclosure, nor are they intended to limit the scope of the disclosure. Other features of embodiments of the present disclosure will become apparent from the following description.
Drawings
The above and other features, advantages and aspects of embodiments of the present disclosure will become more apparent by reference to the following detailed description when taken in conjunction with the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements.
Fig. 1 shows a circuit diagram of a fault detection circuit according to an example embodiment of the present disclosure.
Detailed Description
Embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While certain embodiments of the present disclosure have been shown in the accompanying drawings, it is to be understood that the present disclosure may be embodied in various forms and should not be construed as limited to the embodiments set forth herein, but are provided to provide a more thorough and complete understanding of the present disclosure. It should be understood that the drawings and embodiments of the present disclosure are for illustration purposes only and are not intended to limit the scope of the present disclosure.
As previously mentioned, conventional digital quantity output systems are not fully diagnosed in application, and are prone to failure to effectively locate when a fault occurs, resulting in long-term sickness, and/or spread of the fault. Typically, the drawbacks or deficiencies of conventional systems can be summarized as follows:
failure to achieve both wire break and short circuit diagnostics;
the diagnosis can be basically only detected when the switch element is in an ON state, and the OFF state can not acquire the system state in real time, so that the system works with diseases when the OFF-ON state is converted, and the fault is diffused again;
part of methods can realize short circuit and disconnection detection in an OFF state, but the method has insufficient universality and low practical applicability, and especially aims at capacitive or inductive load application;
without an effective short-circuit protection mechanism, system damage is easily caused.
For example, application number CN115865062a discloses a digital quantity output module capable of realizing a diagnosis of a short circuit of a load in a state where a switching element is ON, but for a diagnosis of an OFF state, a method of transmitting a momentary pulse is adopted. However, in practical use, the pulse width of the transient pulse is related to the load, so that the universality is poor, and particularly for inductive load or capacitive load, the pulse signal is easy to distort due to the charge and discharge phenomenon, and the pulse size is difficult to accurately adjust; if the pulse width is too small, then an effective diagnosis is not possible; if the pulse width is too large, the load is easily erroneously driven, resulting in malfunction.
For another example, application number CN114879086a discloses a disconnection detecting circuit and system of a digital quantity output circuit, in which a diode drop in an output loop is used for resolution. However, the system can only distinguish the current with great change, and the broken wire or normal state is not well distinguished when the system is used for small current driving; meanwhile, for high-current application, short circuit or normal state is not well resolved, and diagnosis of the load in the OFF state of the switching element cannot be performed.
It is an object of the present disclosure to provide an improved fault detection circuit that can provide (real-time) load disconnection and short circuit detection both when the switching element is in an ON and OFF state. In addition, the fault detection circuit disclosed by the invention can also perform effective system protection in the case of short-circuit faults and has a recovery function. Specifically, the fault detection circuit of the present disclosure may include: a channel unit configured to supply a drive signal to a load via a switching element, the channel unit comprising the following components connected in series in order: a parallel combination of a sampling resistor, the switching element, and a bypass resistor, and a diode, wherein a negative terminal of the diode is connected to a load; a disconnection detecting unit configured to determine whether the load is disconnected via a first voltage across the sampling resistor, regardless of whether the switching element is turned on; and a short-circuit diagnosis unit configured to be able to determine whether the load is open or not via a second voltage of a node between the parallel combination and the diode, regardless of whether the switching element is on or not. It will be appreciated that the fault detection circuit of the present disclosure may be particularly applicable to digital quantity output systems and find application in the industrial control industry.
To facilitate understanding of the above-described fault detection circuit, fig. 1 shows a circuit diagram of the fault detection circuit according to an example embodiment of the present disclosure.
As shown in fig. 1, the fault detection circuit 1 may include a channel unit 2, a disconnection detection unit 3, and a short circuit diagnosis unit 4.
The channel unit 2 functions to supply a drive signal to the load RL via the switching element U1. In some embodiments, the channel unit 2 may comprise the following components connected in series in order: a parallel combination of both the sampling resistor R1, the switching element U1 and the shunt resistor R2, and a diode D1, wherein the negative terminal of the diode D1 can be connected to the load RL. In some embodiments, one end of the sampling resistor R1 may be connected to the power supply VCC, and the other end of the load RL may be grounded.
The switching element U1 may be in an ON or OFF state by a switching control signal. When the switching element U1 is in the ON state, the power supply VCC will provide a driving signal for the load RL, and when the switching element U1 is in the OFF state, the driving signal will be removed.
In some embodiments, the switching element U1 may be a MOS transistor, where a gate of the MOS transistor may be configured to receive the switching control signal. Typically, the MOS transistor may be a PMOS transistor. It will be appreciated that in embodiments where the digital quantity output system is an active module, the use of MOS transistors is particularly advantageous because MOS transistors consume large power, which facilitates large flow drive capability. However, this is not limiting, and in some embodiments it is also possible that the switching element U1 is another type of switching element, such as a bipolar transistor, wherein the base of the bipolar transistor may be used to receive the above-mentioned switching control signal.
In some embodiments, to provide the above switch control signal, the fault detection circuit 1 may further include an output control unit 5, where the output control unit 5 is configured to receive an external control instruction to generate a switch control signal for controlling the on/off of the switching element U1. In some embodiments, for anti-interference purposes (e.g., of industrial control industry), the output control unit 5 may further include an isolation circuit OPT1, where a primary side of the isolation circuit OPT1 may be connected to the power supply VDD via a resistor R15, and a secondary side may be connected to ground via a current limiting resistor R14. In the case that the switching element U1 is a MOS transistor or a bipolar transistor, a gate or a base of the switching element U1 may be connected to a node between the isolation circuit OPT1 and the current limiting resistor R14 to receive the switching control signal. Typically, implementations of the isolation circuit OPT1 may include, but are not limited to: optical coupling isolation, magnetic isolation, or capacitive isolation.
In the above example, the output control unit 5 may receive an instruction CH1-CON from the processor, for example, when CH1-CON is at a high level, the isolation circuit OPT1 is opened, and U1 is closed; when CH1-CON is low, the isolation circuit OPT1 is closed and U1 is opened. What needs to be explained here is: when VCC is greater than V of U1 GS At threshold value, V GS And a protection tube is added at two ends for voltage limiting protection.
The function of the above-mentioned sampling resistor R1 is to collect the current flowing through the channel unit 1 for collection by the disconnection detecting unit 3, as will be described in further detail later. In some embodiments, the sampling resistor R1 is a high-power resistor with a small resistance value and capable of bearing a large current. The bypass resistor R2 serves to provide a certain current path when U1 is in the OFF state, thereby allowing the disconnection detecting unit 3 and the short circuit diagnosing unit 4 to detect in the OFF state.
As an example, the resistance values of R1 and R2 described above may be set, for example, according to the leakage current allowed by the load RL, for example, based on 50% of the leakage current. Here, it is assumed that the load RL allows a leakage current of 4mA, while the bypass current in the OFF state is estimated to be approximately 2 mA. Assuming that VCC is 24V, there are:
24V=2mA*（R1+R2）+V D （1）
wherein V is D The voltage drop for diode D1.
Suitable values for R1 and R2 may be selected based on equation (1) above. For example, in some examples, the resistance of the sampling resistor R1 may be selected to be in the ohmic level, and the resistance of the shunt resistor R2 may be selected to be in the 10K ohmic level.
In the case of the above-mentioned suitable resistance values of R1 and R2, when the switching element U1 is in the ON state, the impedance of U1 may be much smaller than R2, and at this time, the channel current flows through U1, and the shunt resistor R2 will not be affected; when the switching element U1 is in the OFF state, a low-current channel, that is, VCC-R1-R2-D1-RL, can be established through the shunt resistor R2, so that the disconnection and short circuit detection to be described further below can be realized under the condition that the switching element U1 is OFF, intermittent detection is not required to be performed by sending a pulse signal, and the problem of detection failure caused by pulse signal distortion due to charge and discharge of capacitive and inductive loads is solved.
The broken line detection unit 3 amplifies the voltages at two ends of the sampling resistor R1, and drives the isolation circuit OPT2 to perform logic signal transmission. Note that: the isolation circuit OPT2 is typically introduced for interference immunity, and in some embodiments, it is possible to have no isolation circuit OPT2. In particular, the disconnection detecting unit 3 is configured to be able to determine whether the load RL is disconnected via the first voltage across the sampling resistor R1, regardless of whether the above-described switching element U1 is turned ON (or in an ON state).
In some embodiments, the disconnection detecting unit 3 may include an amplifier circuit 31 and an isolation circuit OPT2 connected in series, and the amplifier circuit 31 may amplify the voltage across the sampling resistor R1 and then output a disconnection detecting signal via the isolation circuit OPT2.
The type and amplification factor of the amplifier circuit 31 described above may be designed according to the application requirements. Here, assuming that the switching element U1 is in an OFF state and that about 50% of the leakage current (e.g., 1mA or 2 mA) is the basis for the disconnection determination, if the sampling resistor R1 is 1 ohm, the voltage drop of the sampling resistor R1 is 0.001V to 0.002v, and since the driving optocoupler is at least about 3V, at least 1500 times or 3000 times of amplification is required.
In some embodiments, the above-mentioned amplifier circuit 31 may be, for example, a differential amplifier circuit in which the positive input terminal of the operational amplifier U1A may be connected to one end of the sampling resistor R1 via the first resistor R3 and the negative input terminal of the operational amplifier U1A may be connected to the other end of the sampling resistor R1 via the second resistor R4. In addition, the positive input terminal of the operational amplifier U1A may be further connected to the ground via the third resistor R5, and the output of the operational amplifier U1A may be connected to the negative input terminal thereof via a feedback path including the fourth resistor R6.
As an example, for the sake of calculation, the resistances of the first resistor R3 and the second resistor R4 may be the same, and the resistances of the third resistor R5 and the fourth resistor R6 may be the same, and then the output voltage of the amplifier circuit 31= (R5/R3) ×vr1, where VR1 is the voltage drop across R1.
In some embodiments, in order to match the impedance of the operational amplifier U1A, the third resistor R5 is preferably not more than 1 mohm. In addition, if the operational amplifier U1A uses the same power supply VCC as the channel unit 1, a rail-to-rail operation is required; otherwise the common mode input range has to be considered and the supply of the operational amplifier adjusted accordingly.
In some embodiments, the amplifier circuit 31 is connected to the isolation circuit OPT2 via a current limiting resistor R7. Typically, implementations of the isolation circuit OP2 may include, but are not limited to: optical coupling isolation, magnetic isolation, or capacitive isolation. In the embodiment where the isolation circuit OPT2 is an optocoupler, considering that a minimum 3V driving voltage is required to turn on the optocoupler and at the same time, at the maximum 24V, no overcurrent is caused between the optocoupler and the current limiting resistor R7, a larger package resistor of about 1K may be selected. In addition, the secondary-side current limiting resistor R8 of the isolation circuit OPT2 may be set so that the isolation circuit OPT2 can be in a saturated state when the primary-side driving voltage is 3V.
The short-circuit diagnosis unit 4 functions to diagnose whether the load RL is in a short-circuit state. In particular, the short-circuit diagnosis unit 4 is configured to be able to determine whether the load RL is short-circuited via the above-described parallel combination of both the switching element U1 and the shunt resistor R2 and the second voltage of the node between the diodes D1, regardless of whether the switching element U1 is on or not.
Therefore, the short-circuit diagnosis unit 4 will collect the second voltage between the switching element U1 and the diode D1. In some embodiments, the short circuit diagnosis unit 4 may include a comparison circuit 41 and an isolation circuit OPT3 connected in series, the comparison circuit 41 being configured to receive the second voltage and output a short circuit detection signal via the isolation circuit OPT3. Note that: the isolation circuit OPT3 is typically introduced for interference immunity, and in some embodiments, it is possible to have no isolation circuit OPT3. Typically, implementations of the isolation circuit OPT3 described above may include, but are not limited to: optical coupling isolation, magnetic isolation, or capacitive isolation.
In some embodiments, the comparison circuit 41 may include a comparator or an operational amplifier U1B. It should be appreciated that the comparator or operational amplifier U1B may implement the collection of the second voltage in either positive logic or negative logic.
As an example of the positive logic scheme, the positive input terminal of the comparator or the operational amplifier may be connected to a node between the diode D1 and the parallel combination of the switching element U1 and the shunt resistor R2. As an example of the negative logic method, the negative input terminal of the comparator or the operational amplifier may be connected to the node between the parallel combination and the diode D1. Whether positive or negative, the comparator circuit 41 may also include a reference circuit that is intended to provide a reference voltage to one input of the comparator or op-amp U1B, which may be set based on the voltage drop of the diode D1 under a short circuit of the load RL.
As an example, the above-mentioned reference circuit may be constituted by a series combination of a fifth resistor R9 and a sixth resistor R10, one end of which is connected to the power supply VCC, and the other end of which is connected to the ground. In addition, a node between the fifth resistor R9 and the sixth resistor R10 may be connected to one input terminal of the above-mentioned comparator U1B, thereby providing an appropriate reference voltage to the comparator or operational amplifier U1B.
The reference voltage may be set according to the second voltage of the load RL in the OFF state of the switching element without a short circuit.
For example, when the load RL is short-circuited, the voltage between the switching element U1 and the diode D1 is theoretically about 0.7V of the forward voltage drop of the diode D1; when the load RL is not shorted, the second voltage in the OFF state will be smaller than that in the ON state, and here, for example, assuming that the minimum resistance of the load RL in the non-shorted state is about 200 ohms, the second voltage in the OFF state may reach at least about 24V (200/10K) +0.7v=1.18V, so it is sufficient to distinguish from 0.7V in the case of a short circuit. Therefore, the reference voltage is preferably set at about 1V, and if the second voltage is less than 1V, it is determined that the circuit is shorted, otherwise it is determined that the circuit is not shorted.
In some embodiments, the comparison circuit 41 may further include a pull-up resistor R11, which may be connected between the output of the comparator U1B and its power supply VCC. Further, similar to the disconnection detecting unit 3 described above, in some embodiments, the above-described comparison circuit 41 may also be connected to the isolation circuit OPT3 via the current limiting resistor R12. In addition, the secondary side of the isolation circuit OPT3 may be further provided with a current limiting resistor R13 so as to enable the isolation circuit OPT3 to be in a saturated state when the primary side driving voltage is 3V.
Here, assuming that the comparator U1B adopts positive logic acquisition (positive input acquisition in fig. 1), the output is low, the isolation circuit OPT3 is turned off, and the short circuit diagnosis signal is 1; if the second voltage is greater than 1V, the short circuit is not generated, and at the moment, if the comparator U1B adopts positive logic acquisition, the output is high, the optocoupler OPT3 is closed, and the short circuit diagnosis signal is 0. If U1B employs negative logic acquisition, the logic is reversed.
To facilitate an understanding of the aspects of the present disclosure, the following is a truth table for fault detection circuitry of the present disclosure to make wire break and short circuit diagnostics.
Specific embodiments of the various components of the fault detection circuit of the present disclosure for detecting wire breaks and shorts have been described in detail above. It will be appreciated that the fault detection circuit of the present disclosure may enable detection of wire breaks and short circuit conditions in real time and is particularly advantageous for digital quantity output systems. In some embodiments, the wire break may be performed in a round robin or triggered fashion, while the short circuit detection may be performed in a triggered fashion. It will be appreciated that the trigger mode response time is fast and the priority is higher.
In some embodiments, the disconnection diagnosing signal and/or the short-circuit detecting signal may further trigger a processor (not shown) in the detecting circuitry to perform related processing, and the processor may send the aforementioned CH1-CON command, for example, so as to disconnect the switching element U1 from the U1, thereby preventing the devices on the channel unit from being damaged due to excessive current, and meanwhile, the system performs a channel short-circuit alarm.
In some embodiments, when it is detected that the channel unit changes from short-circuited to non-short-circuited, the processor may attempt to turn on the switching element U1 according to the pre-fault state. By the method, the ON state of the channel unit in the short circuit condition can be timely converted into the OFF state for fault detection, the continuous influence caused by the short circuit is effectively prevented, and the channel state can be automatically recovered in fault recovery. Thus, in these embodiments, the above-described processor may be configured to perform the following operations: outputting a control instruction to put the switching element (U1) in an OFF or OFF state in response to receiving a short-circuit diagnosis signal indicating that the load is short-circuited; and outputting a control instruction to cause the switching element (U1) to switch from the OFF or OFF state to an ON or ON state in response to receiving the short circuit diagnosis signal when transitioning from short circuit to normal.
Further, it will be appreciated that the present disclosure may relate not only to the above-described fault detection circuit, but also to detection circuitry including the above-described fault detection circuit, wherein the circuitry may include a processor to process a wire break or short circuit diagnostic signal output by the above-described fault detection circuit.
It will be appreciated that the technical solution of the present disclosure may have the following advantages:
the diagnostic coverage is complete, and the detection of the disconnection and short circuit of the load of the switching element in the ON and OFF states can be effectively diagnosed;
the diagnostic scheme has wide applicability, and solves the problem that the intermittent pulse detection scheme and the capacitive load are difficult to match in the prior art;
when a short circuit occurs, the detection can be quickly responded when the closed channel is turned into an OFF state, so that the system is effectively protected;
the scheme of the present disclosure is implemented by conventional components, and is easy to popularize.
While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.
In the claims, the word "comprising" does not exclude other elements, and the indefinite article "a" or "an" does not exclude a plurality. A single element or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain features are recited in mutually different embodiments or in dependent claims does not indicate that a combination of these features cannot be used to advantage. The scope of the present application encompasses any possible combination of the features recited in the various embodiments or the dependent claims without departing from the spirit and scope of the present application.
Furthermore, any reference signs in the claims shall not be construed as limiting the scope of the invention.
Claims (10)
1. A fault detection circuit (1), characterized by comprising:
a channel unit (2) configured to provide a drive signal to a load (RL) via a switching element (U1), the channel unit (2) comprising the following components connected in series in order: -a parallel combination of a sampling resistor (R1), the switching element (U1) and a shunt resistor (R2), and-a diode (D1), wherein the negative terminal of the diode (D1) is connected to a load (RL);
a disconnection detecting unit (3) configured to be able to determine whether the load (RL) is disconnected via a first voltage across the sampling resistor (R1) regardless of whether the switching element (U1) is turned on; and
a short-circuit diagnosis unit (4) configured to determine whether the load (RL) is short-circuited via a second voltage of a node between the parallel combination and the diode (D1) regardless of whether the switching element (U1) is on.
2. The circuit according to claim 1, characterized in that the disconnection detection unit (3) comprises an amplifier circuit (31) and a first isolation circuit (OPT 2) connected in series, the amplifier circuit (31) being adapted to amplify the first voltage and to output a disconnection detection signal via the first isolation circuit.
3. The circuit according to claim 2, characterized in that the amplifier circuit (31) is a differential amplifier circuit, in which the positive input of an operational amplifier (U1A) is connected to one end of the sampling resistor (R1) via a first resistor (R3), the negative input of the operational amplifier (U1A) is connected to the other end of the sampling resistor (R1) via a second resistor (R4),
the positive input of the operational amplifier (U1A) is also connected to ground via a third resistor (R5), and the output of the operational amplifier (U1A) is connected to the negative input via a feedback path comprising a fourth resistor (R6).
4. A circuit according to any one of claims 1 to 3, characterized in that the short circuit diagnosis unit (4) comprises a comparison circuit (41) and a second isolation circuit (OPT 3) connected in series, the comparison circuit (41) being configured to receive the second voltage and to output a short circuit detection signal via the second isolation circuit (OPT 3).
5. The circuit according to claim 4, characterized in that the comparison circuit (41) comprises a comparator or an operational amplifier (U1B), the positive input of which comparator (U1B) or operational amplifier is connected to the node, whereby the short-circuit diagnosis unit (4) implements short-circuit detection in a positive logical manner.
6. The circuit according to claim 4, characterized in that the comparison circuit (41) comprises a comparator or an operational amplifier (U1B), the negative input of which comparator or operational amplifier (U1B) is connected to the node, whereby the short-circuit diagnosis unit (4) implements short-circuit detection in a negative logic manner.
7. The circuit according to claim 5 or 6, characterized in that the comparison circuit (41) further comprises a reference circuit for providing a reference voltage to the comparator or operational amplifier (U1B), the reference voltage being set based on a voltage drop of the diode (D1) under load short-circuiting.
8. A circuit according to any one of claims 1 to 3, wherein the disconnection detection is performed in a polling or triggering manner, and the diagnosis of the short circuit is performed in a triggering manner.
9. A detection circuitry, comprising:
the fault detection circuit (1) according to any one of claims 1-8;
an output control unit (5) for generating a switch control signal for controlling a switching element (U1) in the fault detection circuit (1); and
and a processor configured to output a control instruction to cause an output control unit (5) to generate the switch control signal.
10. The detection circuitry of claim 9, wherein the processor is further configured to:
outputting a control instruction to put the switching element (U1) in an off state in response to receiving a short-circuit diagnosis signal indicating that the load is short-circuited; and
a control instruction for causing the switching element (U1) to switch from the off state to the on state is output in response to receiving the short circuit diagnosis signal when the short circuit diagnosis signal is changed from short circuit to normal.
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