An overcurrent protection method with a power output interface

Abstract

The present invention provides an overcurrent protection method with a power output interface, which is applied to the functional circuit BIT system in avionics equipment, and includes: sampling the output interface current of the 28V / open output interface circuit to obtain a sampled current; if the sampled current is greater than a preset fast protection overcurrent value, or less than the preset fast protection overcurrent value but greater than a preset slow protection overcurrent value, then calculate and accumulate the current power in the output loop, and when the current power reaches the preset protection value, turn off the output interface, resample and judge after a set time interval, repeat this mechanism at least 3 times, and when the value of the overcurrent times counter is greater than 3, then permanently turn off the output interface. The overcurrent protection strategy of the present invention is more practical, can better improve the fault tolerance of the output interface, reduce false alarms, and better isolate and judge the inrush current on the aircraft.

Description

Technical Field

[0001] The present invention relates to the technical field of airborne electromechanical systems, and particularly to an overcurrent protection method with a power output interface. Background Art

[0002] In an airborne electromechanical system, a single controller has a dual-channel redundancy design of A and B inside. Each channel can provide 54 28V / open output interfaces. A single-channel power 28V / open discrete quantity consists of a power drive circuit, an I 2 T protection circuit, and a discrete quantity output readback interface. Its system block diagram is as Figure 1 shown. This type of interface circuit provides discrete quantity outputs in two states. One is the high-impedance state (open circuit), and the other is the 28V state. The switch is controlled to switch between the two states by receiving application software commands, and discrete quantity sampling is performed at the output port to implement the BIT function of the circuit.

[0003] When an external short circuit or an abnormal current state occurs, this interface can implement a protection function through the I 2 T mechanism, and cut off the output path to the "open circuit" safe state. The specific implementation is to use a 0.01Ω resistor in series in the output loop as a sampling resistor. The voltage difference across the sampling resistor is amplified by an amplifier with a fixed gain of 60 for the voltage signal. The voltage of all 54 28V / open output interfaces is collected separately through a multiplexed analog switch in sequence, and the current value in this output path is calculated in real time. When the current power (I 2 T) in the output loop reaches the preset protection value, the overcurrent protection function is achieved by controlling the MOS transistor to cut off the external power output. And currently, the protection strategy set by the software is that the output state is locked as an open circuit after protection, and the output lock can be released by powering the product on and off.

[0004] From its own perspective, the controller outputs a relatively large load current as much as possible while ensuring the safety of the internal circuit of the product. The corresponding designed protection action curve is as Figure 2 shown. This part of the function is implemented in the system software and can be optimized and adjusted.

[0005] In the current controller, the overcurrent protection strategy designed by the system software is that once an external short circuit or an abnormal current state occurs, this interface can implement a protection function through the I 2 T mechanism, and cut off the output path to the "open circuit" safe state, so that there is no output at this output interface after overcurrent. This strategy has a high false alarm rate, low robustness, and the output interface protects against large currents on the aircraft too quickly. Summary of the Invention

[0006] In view of this, an overcurrent protection method with a power output interface provided by an embodiment of the present application aims to improve the fault tolerance of the output interface and reduce false alarms.

[0007] The embodiment of the present application provides the following technical solutions: An overcurrent protection method with a power output interface, which is applied to the functional circuit BIT system in avionics equipment, includes:

[0008] Sampling the output interface current of the 28V / open output interface circuit to obtain a sampled current;

[0009] If the sampled current is greater than a preset fast protection overcurrent value, calculate and accumulate the current power in the output loop. When the current power reaches the preset fast protection value, turn off the output interface, set the first overcurrent protection re-output interval time and start counting, and increment the value of the overcurrent count counter by 1; after the first overcurrent protection re-output interval time, turn on the output interface, sample the output interface current again, and repeat this mechanism at least 3 times. When the value of the overcurrent count counter is greater than 3, set the fast protection overcurrent turn-off flag bit to 1 and report it to the upper computer, and permanently turn off the output interface;

[0010] If the sampled current is less than the preset fast protection overcurrent value but greater than the preset slow protection overcurrent value, calculate and accumulate the current power in the output loop. When the current power reaches the preset slow protection value, turn off the output interface, set the second overcurrent protection re-output interval time and start counting, and increment the value of the overcurrent count counter by 1; after the second overcurrent protection re-output interval time, turn on the output interface, sample the output interface current again, and repeat this mechanism at least 3 times. When the value of the overcurrent count counter is greater than 3, set the slow protection overcurrent turn-off flag bit to 1 and report it to the upper computer, and permanently turn off the output interface.

[0011] According to an embodiment, the fast protection overcurrent value is 6A, and the slow protection overcurrent value is 1.8A.

[0012] According to an embodiment, the first overcurrent protection re-output interval time is 6s, and the second overcurrent protection re-output interval time is 0.1s.

[0013] According to an embodiment, if the sampled current is less than the preset slow protection overcurrent value, the output of this interface is normal.

[0014] According to an embodiment, it further includes: before sampling the current of the output interface, judging the state of the current output interface. When the state of the output interface of this channel is 28V output, the overcurrent detection and protection of this output interface are performed; otherwise, the state of this output interface is open, and the overcurrent detection and protection are not performed.

[0015] According to an embodiment, it further includes: before sampling the current of the output interface, determining whether the user instruction output by the host is zero. If it is zero, the corresponding output interface is closed; if it is not zero, the corresponding output interface is opened and the overcurrent detection and protection process is entered.

[0016] According to an embodiment, when the output interface is permanently turned off, the permanent off lock can be released by powering on and off again, and at the same time, the value of the overcurrent count counter is cleared to 0, the value of the counter for the overcurrent protection re-output interval time is cleared to 0, and the overcurrent shutdown flag bit and the over-power shutdown flag bit are cleared.

[0017] Compared with the prior art, the beneficial effects that can be achieved by at least one of the above technical solutions adopted in the embodiments of this specification at least include: Through sufficient experimental verification in the embodiments of the present invention, this overcurrent protection strategy is more practical, can better improve the fault tolerance of the output interface, reduce false alarms, and better isolate and judge the inrush current on the machine. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0019] Figure 1 is a schematic diagram of the principle of the 28V / open output interface circuit;

[0020] Figure 2 is a schematic diagram of the overcurrent protection time;

[0021] Figure 3 is a software flowchart of the overcurrent protection method according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The embodiments of the present application will be described in detail below with reference to the drawings.

[0023] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments. The technical solutions of the present invention are clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0024] With the increase in the power load of multi-point aircraft and electrical equipment and the highly integrated finished products of the system, more and more power output controls are integrated by computer interface products, which are mostly used for motor, contactor control and sensor power distribution in the airborne electromechanical system. In the computer application system, to achieve drive control of the electromechanical system, usually these electromechanical systems are high-power systems. The output digital signal of the computer is converted into an analog signal through D / A, and then the control of the electromechanical system is realized through various drive circuits related to the object.

[0025] As Figure 3 shown, an embodiment of the present invention provides an overcurrent protection method with a power output interface, which is applied to the functional circuit BIT system in avionics equipment, including:

[0026] Sampling the output interface current of the 28V / open output interface circuit to obtain a sampled current;

[0027] If the sampled current is greater than the preset fast protection overcurrent value, calculate and accumulate the current power in the output loop. When the current power reaches the preset fast protection value, turn off the output interface, and at the same time set the first overcurrent protection re-output interval time and start counting, and add 1 to the value of the overcurrent count counter; after the first overcurrent protection re-output interval time, turn on the output interface, sample the output interface current again, and repeat this mechanism at least 3 times. When the value of the overcurrent count counter is greater than 3, set the fast protection overcurrent off flag bit to 1 and report it to the upper computer, and permanently turn off the output interface;

[0028] If the sampled current is less than the preset fast protection overcurrent value and greater than the preset slow protection overcurrent value, calculate and accumulate the current power in the output loop. When the current power reaches the preset slow protection value, turn off the output interface, and at the same time set the second overcurrent protection re-output interval time and start counting, and add 1 to the value of the overcurrent count counter; after the second overcurrent protection re-output interval time, turn on the output interface, sample the output interface current again, and repeat this mechanism at least 3 times. When the value of the overcurrent count counter is greater than 3, set the slow protection overcurrent off flag bit to 1 and report it to the upper computer, and permanently turn off the output interface.

[0029] The controller is equipped with 54 power 28V / open output interfaces, corresponding to various types of power loads in the on-board bleed air subsystem, air conditioning subsystem, pressure regulation subsystem, and anti-icing subsystem. The design requirement is that the power 28V output interface of the controller has an overcurrent protection function. Therefore, from the perspective of the controller itself, while ensuring the safety of the internal circuit of the product, it outputs a relatively large load current as much as possible. In the present invention, the actual current characteristics of the external load currently cross-linked with the controller are maintained with the original current index unchanged. The current locking strategy in the system software is modified, and an output interface retry mechanism after overcurrent protection is added, with a total of 3 retries. If overcurrent protection is still detected after 3 times, the interface is locked and no output is made during this power-on operation. The interface lock state can only be cleared by powering on and off again to improve the fault tolerance of the output interface, reduce false alarms, and resume interface output if there is no overcurrent.

[0030] The design concept of the overcurrent protection function of the controller in the embodiment of the present invention is to maintain the output to the external load as much as possible without damaging the controller itself. Therefore, releasing the interface lock and attempting to output again also needs to be carried out within the safety tolerance of the controller output circuit: the power PMOS transistor (model IRFF9130) in the 28V output circuit has a steady-state output current of 6.5A and a surge current that can reach 25A, but the minimum time interval for withstanding two surge currents is 6s. Therefore, the time interval for overcurrent protection to output again is set to 6s, and the time interval for over-power protection to output again is 0.1s (the current value of over-power output is always within the steady-state output range of the PMOS transistor, so it can output again quickly).

[0031] At the same time, when detecting the current of the output interface protection, the judgment of the current output interface state is added: only when the state of the output interface of this channel is 28V output, the current detection and protection of the output interface are carried out; otherwise, the state of this interface is an air switch, and the current detection and protection of the output are not carried out, improving the robustness of the output interface protection function and further reducing false alarms.

[0032] The specific process in the system software is as Figure 3 shown. The process of the overcurrent protection curve has three steps: 1. First, judge whether the output again time counter is zero. If it is not zero, wait for the corresponding time (6s or 0.1s); 2. Judge whether the user instruction is zero. If it is zero, close the corresponding output interface. If it is not zero, open the corresponding output interface and enter the overcurrent protection judgment process; 3. (1) Judge the magnitude of the output interface current sampled. If it is greater than the preset fast protection overcurrent value (6A), then when the current power in the output loop (I 2When the fast protection preset protection value is reached, the corresponding output interface is turned off. At the same time, the re-output time counter is set to 6 s, and the value of the overcurrent times counter is incremented by 1. (2) Determine the magnitude of the sampled output interface current. If it is greater than the preset slow protection current value (1.8 A) and less than the preset fast protection overcurrent value, then when the current power (I 2 When the slow protection preset protection value is reached, the corresponding output interface is turned off. At the same time, the re-output time counter is set to 0.1 s, and the value of the overcurrent times counter is incremented by 1. (3) Determine the magnitude of the sampled output interface current. If it is less than the preset slow protection current value, the interface outputs normally. 4. If the value of the overcurrent times counter is greater than 3, set the fast protection off flag or the slow protection flag and report it to the host computer, and permanently turn off the output interface until the product is powered on and off again to unlock.

[0033] The software test results of the overcurrent protection method with a power output interface in the embodiment of the present invention are as follows:

[0034] a. Apply an electronic load to the first path of the 28V / open power output interface. First, apply a current of 6.1 A. As Figure 2 shown, according to the corresponding turn-off time in the figure, the first path of the 28V / open power output interface of the controller is immediately turned off, and it is opened again after 6 s. Then, the interface is turned off for the second time, and so on. A total of 3 attempts are made, and then the interface is completely turned off.

[0035] b. Apply an electronic load to the first path of the 28V / open power output interface. First, apply a current of 6.1 A. As Figure 2 shown, according to the corresponding turn-off time in the figure, the first path of the 28V / open power output interface of the controller is immediately turned off, and it is opened again after 6 s. Then, the interface is turned off for the second time, and a current of 1 A is applied again. After the interface is opened again, it outputs normally.

[0036] c. Apply an electronic load to the first path of the 28V / open power output interface. First, apply a current of 2.5 A. As Figure 2 shown, according to the corresponding turn-off time in the figure, the first path of the 28V / open power output interface of the controller is turned off after a period of time, and it is opened again after 0.1 s. Then, the interface is turned off for the second time, and so on. A total of 3 attempts are made, and then the interface is completely turned off.

[0037] d. Apply an electronic load to the first path of the 28V / open power output interface. First, apply a current of 2.5 A. As Figure 2 shown, according to the corresponding turn-off time in the figure, the first path of the 28V / open power output interface of the controller is turned off after a period of time, and it is opened again after 0.1 s. Then, the interface is turned off for the second time, and a current of 1 A is applied again. After the interface is opened again, it outputs normally.

[0038] The input voltage of the chip amplifier in the current sampling circuit was also tested. The allowable reverse input voltage in the chip manual is -0.3V, which is a long-term steady-state value, and the actual value of this chip was tested.

[0039] a. Apply a negative voltage to RS+ of the amplifier. When the RS+ voltage is in the range of 0 to -0.5V, the amplifier output is normal; when the RS+ voltage is -0.6V, the amplifier output is 0.5V; when the RS+ voltage is -0.7V, the amplifier outputs a square wave signal with an amplitude of 2V and a frequency of about 45K, and the output becomes 0 after about 5 seconds; when the RS+ voltage is lower than -0.8V, the amplifier output is 1.7V, and the device returns to normal after the applied negative voltage is removed;

[0040] b. At the same time, extreme tests were carried out. When the negative voltage applied to RS+ is lower than -0.7V, the currents of RS+ and VCC increase. When the negative voltage is applied for a long time, the device will heat up, but the device will not be damaged. The device function returns to normal after the applied negative voltage is removed. When the negative voltage applied to RS+ reaches -4V, the device will be damaged and cannot be restored after the negative voltage is removed.

[0041] As described above, it is only the specific implementation manner of this application, but the protection scope of this application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in this application should be covered by the protection scope of this application. Therefore, the protection scope of this application shall be subject to the protection scope of the claims.

Claims

1. An overcurrent protection method with a power output interface, which is applied to the functional circuit BIT system in avionics equipment, is characterized in that Including: Sampling the output interface current of the 28V / open output interface circuit to obtain a sampled current; If the sampled current is greater than a preset fast protection overcurrent value, calculate and accumulate the current power in the output loop. When the current power reaches the preset fast protection value, turn off the output interface, set the first overcurrent protection re-output interval time and start counting, and increment the value of the overcurrent count counter by 1. After the first overcurrent protection re-output interval time, turn on the output interface, sample the output interface current again, and repeat the above process at least 3 times. When the value of the overcurrent count counter is greater than 3, set the fast protection overcurrent turn-off flag bit and report it to the host computer, and permanently turn off the output interface; If the sampled current is less than the preset fast protection overcurrent value but greater than the preset slow protection overcurrent value, calculate and accumulate the current power in the output loop. When the current power reaches the preset slow protection value, turn off the output interface, set the second overcurrent protection re-output interval time and start counting, and increment the value of the overcurrent count counter by 1. After the second overcurrent protection re-output interval time, turn on the output interface, sample the output interface current again, and repeat the above process at least 3 times. When the value of the overcurrent count counter is greater than 3, set the slow protection overcurrent turn-off flag bit and report it to the host computer, and permanently turn off the output interface; If the sampled current is less than the preset slow protection overcurrent value, the interface outputs normally; Also including: Before sampling the current of the output interface, judge the state of the current output interface. When the state of the current output interface is 28V output, perform overcurrent detection and protection on the output interface; otherwise, the state of the output interface is open and overcurrent detection and protection are not performed; Also including: Before sampling the current of the output interface, judge whether the user instruction output by the host is zero. If it is zero, close the corresponding output interface. If it is not zero, open the corresponding output interface and enter the overcurrent detection and protection process.

2. The overcurrent protection method with a power output interface according to claim 1, wherein The fast protection overcurrent value is 6A, and the slow protection overcurrent value is 1.8A.

3. The overcurrent protection method with a power output interface according to claim 1, wherein The first overcurrent protection re-output interval time is 6s, and the second overcurrent protection re-output interval time is 0.1s.

4. The overcurrent protection method with a power output interface according to claim 1, characterized in that, When the output interface is permanently turned off, the permanent turn-off lock can be released by re-powering on and off, and at the same time, the value of the overcurrent count counter is cleared to 0, the value of the overcurrent protection re-output interval time counter is cleared to 0, and the overcurrent turn-off flag bit and the over-power turn-off flag bit are cleared.

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