Switching quantity input signal acquisition circuit with self-checking and low power consumption and method

Abstract

The application relates to a switch quantity input signal acquisition circuit and method with self-checking and low power consumption, which is connected with an MCU, and is characterized in that the acquisition circuit comprises a self-checking loop and at least one acquisition loop connected with the MCU respectively, and the self-checking loop is connected with each acquisition loop respectively. Compared with the prior art, the application has the advantages of AC / DC universality and improved system reliability.

Description

Technical Field

[0001] This invention relates to the technology of acquiring switch input signals, and in particular to a switch input signal acquisition circuit and method that is applicable to both AC and DC signals and features self-testing and low power consumption. Background Technology

[0002] In relay protection or safety automation devices used in power system substations and industrial production sites, it is usually necessary to install switch input circuits to acquire relevant important digital signal states for triggering control actions or recording system status. The input circuits must strictly isolate the internal low-voltage circuits from the external high-voltage circuits. Optocouplers are typically used for isolation and signal transmission. The external high-voltage circuit is connected to the primary side of the optocoupler via a series resistor, while the internal low-voltage circuit is connected to the secondary side. A pull-up resistor converts the current signal on the secondary side of the optocoupler into a voltage level signal that can be read by the MCU. Based on the current transfer ratio characteristics of the optocoupler, a suitable current-limiting resistor is connected in series in the primary high-voltage circuit to adjust the trigger threshold voltage of the input circuit. A typical input circuit consists of... Figure 1 As shown.

[0003] The reliability of input circuits affects the reliability of the protection system's control functions; therefore, it is necessary to perform real-time self-checks on the input circuits. Conventional input self-check methods include... Figure 2 The parallel type shown also includes, for example, the parallel type. Figure 3 The pulse injection type is shown.

[0004] In devices employing a parallel input self-test circuit method, strict isolation between the self-test circuit and the input circuit is not achieved. Interference signals introduced by the input high-voltage circuit can easily damage the internal components of the low-voltage system, affecting the overall reliability of the system. Furthermore, the input self-test signal and the input acquisition signal may be confused and overlapped, which can easily lead to incorrect self-test results or malfunctions in the input circuit.

[0005] Devices employing the pulse injection type input self-test loop method use analog acquisition pins for acquiring input self-test status and input signals, which occupies the number of ADC channels. If the device also needs to acquire external electrical signals, it is necessary to configure an additional ADC chip, which will lead to a significant increase in cost. On the other hand, the MCU's acquisition of the multi-byte digital signal output by the ADC conversion will inevitably be slower than the acquisition of the bit digital signal at the pin level, which will lead to a waste of resources in system configuration. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art by providing a circuit and method for acquiring switch input signals with self-testing and low power consumption.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] According to one aspect of the present invention, a switch input signal acquisition circuit with self-test and low power consumption is provided. The circuit is connected to an MCU. The acquisition circuit includes an input self-test circuit and at least one input acquisition circuit, each connected to the MCU. The input self-test circuit is connected to each input acquisition circuit.

[0009] As a preferred technical solution, the input acquisition circuit includes a first optocoupler OP1, a first transistor Q1, a full-wave rectifier bridge BG, and a second transistor Q2;

[0010] The input terminals of the full-wave rectifier bridge BG are connected to the high-voltage input signal DI_IN and the input power ground DI_GND, respectively, and the output terminals are connected to the collector of the first transistor Q1 and the emitter of the second transistor Q2, respectively.

[0011] The base of the first transistor Q1 is connected to the input terminal DI_EN of the on / off control signal of the input circuit, and the emitter is connected to the base of the second transistor Q2, the first optocoupler OP1, and the input terminal DI_CHECK of the input self-test circuit.

[0012] The first optocoupler OP1 is connected to the emitter of the first transistor Q, the collector of the second transistor Q2, and the low-voltage input signal terminal MCU_DI.

[0013] As a preferred technical solution, the input acquisition circuit further includes resistors R3, R4, and R5 for adjusting the input trigger voltage threshold. Resistor R3 is connected between the input terminal of the full-wave rectifier bridge BG and the high-voltage input signal DI_IN. Resistor R4 is connected between the input terminal of the full-wave rectifier bridge BG and the input power ground DI_GND. Resistor R5 is connected between the emitter of the first transistor Q1 and the emitter of the second transistor Q2.

[0014] As a preferred technical solution, the first transistor Q1 is a high-voltage NPN transistor used to connect and disconnect the high-voltage input acquisition circuit.

[0015] As a preferred technical solution, the second transistor Q2 is an NPN transistor, used to connect and disconnect the input to the self-test circuit.

[0016] As a preferred technical solution, the input self-test circuit includes a second optocoupler OP2, a third optocoupler OP3, a third transistor Q3, and an isolated DC power supply DCDC;

[0017] The second optocoupler OP2 is connected to the isolated DC power supply DCDC, the input circuit on / off control signal input terminal DI_EN, and the weak current side input self-test control signal input terminal MCU_CHECK, respectively.

[0018] The third optocoupler OP3 is connected to the base of the third transistor Q3, the isolated DC power supply DCDC, and the input terminal MCU_EN of the weak current side switch circuit on / off control signal, respectively.

[0019] The collector of the third transistor Q3 is connected to the isolated DC power supply DCDC.

[0020] As a preferred technical solution, the third optocoupler OP3 is connected to the MCU_EN terminal of the weak current side switch circuit on / off control signal input terminal through resistor R8.

[0021] As a preferred technical solution, the third optocoupler OP3 is connected to the isolated DC power supply DCDC through resistor R10.

[0022] As a preferred technical solution, the second optocoupler OP2 is connected to the MCU_CHECK self-test control signal input terminal on the weak current side of resistor R9.

[0023] According to another aspect of the present invention, a method for acquiring the aforementioned switch input signal with self-test and low power consumption is provided, comprising the following steps:

[0024] Step 1: Set the MCU_EN signal to low level to cut off the input acquisition circuit, and then set the MCU_CHECK signal to high level to enable the input self-test circuit. At this time, the MCU reads the level of the MCU_DI input signal corresponding to each input circuit. If it is low level, the input circuit of that channel passes the self-test; otherwise, it fails the self-test and a fault needs to be reported.

[0025] Step 2: Set the MCU_CHECK signal to low level to disable the input self-test loop. At this time, the MCU reads the level of the MCU_DI input signal corresponding to each input loop. If it is high, the input loop of that channel passes the self-test; otherwise, it fails the self-test and a fault needs to be reported.

[0026] Step 3: If all input channels pass the self-test twice, the MCU sets the MCU_CHECK signal to low level and the MCU_EN signal to high level, turning on all input acquisition circuits. At this time, the MCU reads the level of the MCU_DI input signal corresponding to each input circuit. If it is low, it indicates that the input channel has a voltage that exceeds the input trigger threshold. Otherwise, it indicates that the input channel does not exceed the input trigger threshold. This state is written into the buffer.

[0027] Step 4: Finally, the MCU sets the MCU_EN signal to a low level to cut off the input acquisition circuit and reduce the overall power consumption of the system.

[0028] Step 5: Determine whether the current input circuit has a valid digital input by using the proportion of the number of low and high level digital states stored in the sliding buffer within the length of the sliding buffer.

[0029] The criterion formula is N is the length of the sliding buffer, n is the number of low-level digital states stored in the buffer, and k is the criterion coefficient for determining whether a condition is met.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] 1) It can be used with both AC and DC power, and there are no requirements on the type of input power supply.

[0032] 2) Since the input acquisition circuit is only connected during the time period when the MCU is acquiring the status, and is disconnected at other times, it has the characteristics of high power and low power consumption. High power can improve the reliability of the system and avoid input malfunctions caused by external interference, while low power consumption can reduce the load on the input power supply and enhance the stability of the system.

[0033] 3) Strong and weak currents are strictly isolated, and interference from the strong current side will not be transmitted to the weak current side.

[0034] 4) Low cost; the selected components will not significantly increase the cost of the input circuit.

[0035] 5) Input acquisition and input self-test are completely isolated in time, and the results of the two actions exist independently and will not affect each other.

[0036] 6) Whether the input self-test fails or the input self-test circuit fails, the MCU can obtain the fault status in a timely manner by reading the level status. Attached Figure Description

[0037] Figure 1 The circuit diagram is for an existing conventional input circuit;

[0038] Figure 2 The circuit diagram is for an existing parallel-type input circuit.

[0039] Figure 3 The circuit diagram is for an existing pulse injection type open-circuit circuit.

[0040] Figure 4 This is a circuit diagram of the input acquisition loop of the present invention;

[0041] Figure 5 This is a circuit diagram of the self-test circuit of the present invention; Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0043] The present invention discloses a switch input signal acquisition circuit with self-test and low power consumption. The circuit is connected to an MCU. The acquisition circuit includes one input self-test circuit and at least one input acquisition circuit, each connected to the MCU. The input self-test circuit is connected to each input acquisition circuit.

[0044] Input acquisition circuit such as Figure 4 As shown. Q1 is a high-voltage NPN transistor used to connect and disconnect the high-voltage input acquisition circuit, controlled by the MCU via optocoupler isolation. BG is a full-wave rectifier bridge used to rectify the AC input into a positive semi-circular wave. R3, R4, and R5 are used to adjust the input trigger voltage threshold. Q2 is a conventional non-high-voltage NPN transistor used to connect and disconnect the input self-test circuit. DI_CHECK is the self-test circuit control signal, DI_EN is the input circuit on / off control signal, DI_GND is the input power ground, DI_IN is the high-voltage input signal, VCC is the low-voltage system power supply, and MCU_DI is the low-voltage input signal input. OP1 is an optocoupler for input signal isolation and transmission.

[0045] Input self-test circuit such as Figure 5 As shown. OP3 is the input self-test control signal transmission and isolation optocoupler. OP2 is the input loop on / off control signal transmission and isolation optocoupler. DCDC is an isolated DC power supply, used to generate a low-voltage DC power supply isolated from the low-voltage system to drive various control signals. VCHECK is the positive terminal of this power supply, and CHECKGND is the ground terminal. MCU_EN is the low-voltage side input loop on / off control signal input, and MCU_CHECK is the low-voltage side input self-test control signal input.

[0046] The above Figure 5 Multiple input self-test circuits can be used. Figure 4 It is used in the input acquisition circuit.

[0047] The software control described with the above circuit is as follows: Upon initial power-up, the MCU_EN signal must be set low, and a stable timer interrupt is configured within the code. Each time a timer interrupt is triggered, the MCU executes the following steps:

[0048] Step 1: Set the MCU_EN signal to low level to cut off the input acquisition circuit, and then set the MCU_CHECK signal to high level to enable the input self-test circuit. At this time, the MCU reads the level of the MCU_DI input signal corresponding to each input circuit. If it is low level, the input circuit of that channel passes the self-test; otherwise, it fails the self-test and a fault needs to be reported.

[0049] Step 2: Set the MCU_CHECK signal to low level to disable the input self-test loop. At this time, the MCU reads the level of the MCU_DI input signal corresponding to each input loop. If it is high, the input loop of that channel passes the self-test; otherwise, it fails the self-test and a fault needs to be reported.

[0050] Step 3: If all input channels pass the self-test twice, the MCU sets the MCU_CHECK signal to low and the MCU_EN signal to high, turning on all input acquisition circuits. At this time, the MCU reads the level of the MCU_DI input signal corresponding to each input circuit. If it is low, it indicates that the input channel has a voltage exceeding the input trigger threshold at this moment. Conversely, it indicates that the input channel does not exceed the input trigger threshold at this moment. This state is written into the sliding buffer.

[0051] Step 4: Finally, the MCU sets the MCU_EN signal to a low level to cut off the input acquisition circuit and reduce the overall power consumption of the system.

[0052] Step 5: Determine whether the current input circuit has a valid digital input by using the ratio of the number of low and high level digital states stored in the sliding buffer to the length of the sliding buffer.

[0053] The criterion formula is N is the length of the sliding buffer, n is the number of low-level digital states stored in the buffer, and k is the criterion coefficient for determining whether a condition is met. Specific Implementation

[0055] Configure the MCU's internal timer interrupt period to 1000Hz, that is, trigger a timer interrupt once every 1ms. Set the sliding buffer length to 20 and the k coefficient to 0.7.

[0056] Add an external 220V AC input signal and execute steps one and two above. If all input channels pass the self-test, continue to the next step; otherwise, it indicates that one or more input channels have failed the self-test and an alarm operation is required.

[0057] Execute steps three through five, and if the corresponding judgment formula for a certain input channel is... If the condition is met, then the channel is determined to have a valid digital input.

[0058] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A collection method for a switch quantity input signal collection circuit with self-checking and low power consumption, the circuit being connected with an MCU, characterized in that, The acquisition circuit comprises one self-check loop and at least one acquisition loop connected with the MCU respectively. The acquisition method comprises the following steps: Step one: set the MCU_EN signal to low level, cut off the acquisition loop, and then set the MCU_CHECK signal to high level to enable the self-check loop. At this time, the MCU reads the level of the MCU_DI signal of each acquisition loop. If the level is low, the acquisition loop passes the self-check; otherwise, the acquisition loop fails the self-check and needs to be reported as a fault. Step two: set the MCU_CHECK signal to low level to close the self-check loop. At this time, the MCU reads the level of the MCU_DI signal of each acquisition loop. If the level is high, the acquisition loop passes the self-check; otherwise, the acquisition loop fails the self-check and needs to be reported as a fault. Step three: if all the acquisition loops pass the self-check twice, set the MCU_CHECK signal to low level and the MCU_EN signal to high level to connect all the acquisition loops. At this time, the MCU reads the level of the MCU_DI signal of each acquisition loop. If the level is low, it indicates that the acquisition loop has a voltage exceeding the trigger threshold at this moment; otherwise, it indicates that the acquisition loop does not have a voltage exceeding the trigger threshold at this moment. Write the state into the sliding buffer area. Step four: finally, set the MCU_EN signal to low level to cut off the acquisition loop and reduce the overall power consumption of the system. Step five: determine whether the acquisition loop has valid switching quantity input by the proportion of the number of low and high levels stored in the sliding buffer area in the length of the sliding buffer area. The criterion formula is N is the length of the sliding buffer, n is the number of low levels in the digital state stored in the buffer, and k is the criterion coefficient for determining whether.

2. The method of claim 1, wherein, The acquisition loop comprises a first optocoupler OP1, a first transistor Q1, a full-wave rectifier bridge BG, and a second transistor Q2. The input end of the full-wave rectifier bridge BG is connected with a strong current input signal DI_IN and an input power ground DI_GND, the positive output end is connected with the collector of the first transistor Q1, and the negative output end is connected with the emitter of the second transistor Q2. The base of the first transistor Q1 is connected with an input end of an acquisition loop on-off control signal DI_EN, and the emitter is connected with the base of the second transistor Q2, the first optocoupler OP1, and an input end of a self-check loop control signal DI_CHECK. The anode A of the first optocoupler OP1 is connected with the emitter of the first transistor Q1, the cathode K is connected with the collector of the second transistor Q2, the collector C is connected with a weak current input signal input end MCU_DI, and the emitter E is grounded. The first transistor Q1 is a high-voltage NPN transistor used for turning on and off the strong current acquisition loop, and the second transistor Q2 is an NPN transistor used for turning on and off the self-check loop.

3. The method of claim 2, wherein, The opening-in acquisition circuit further comprises resistors R3, R4 and R5 for adjusting the opening-in trigger voltage threshold, the resistor R3 is connected between the positive input end of the full-wave rectifier bridge BG and the strong electric opening-in signal DI_IN, the resistor R4 is connected between the negative input end of the full-wave rectifier bridge BG and the opening-in power supply ground DI_GND, and the resistor R5 is connected between the emitter of the first triode Q1 and the emitter of the second triode Q2.

4. The method of claim 2, wherein, The opening-in self-checking circuit comprises a second optocoupler OP2, a third optocoupler OP3, a third triode Q3 and an isolated direct current power supply DCDC. The anode A of the second optocoupler OP2 is connected with the weak electric side opening-in self-checking control signal input end MCU_CHECK, the cathode K is grounded, the collector C is connected with the isolated direct current power supply DCDC, and the emitter E is connected with the opening-in circuit on-off control signal input end DI_EN. The anode A of the third optocoupler OP3 is connected with the weak electric side opening-in circuit on-off control signal input end MCU_EN, the cathode K is grounded, the collector C is connected with the isolated direct current power supply DCDC, and the emitter E is connected with the base of the third triode Q3. The collector of the third triode Q3 is connected with the isolated direct current power supply DCDC.

5. The method of claim 4, wherein, The anode A of the third optocoupler OP3 is connected with the weak electric side opening-in circuit on-off control signal input end MCU_EN through the resistor R8.

6. The method of claim 4, wherein, The collector C of the third optocoupler OP3 is connected with the isolated direct current power supply DCDC through the resistor R10.

7. The method of claim 4, wherein, The anode A of the second optocoupler OP2 is connected with the weak electric side opening-in self-checking control signal input end MCU_CHECK through the resistor R9.

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