Protective circuit capable of enhancing robustness of control interface circuit

Abstract

The invention provides a protective circuit capable of enhancing robustness of a control interface circuit, so as to enhance the robustness of the control interface circuit and reduce the probability of circuit fault caused by external operations of products. The protective circuit is arranged between a control source and a drive circuit, and comprises a diode and a resistor; a control signal output end of the control source is connected to a control signal input end of the drive circuit through the diode arranged in forward direction; the resistor is used as a logic pull-down resistor, and a negative terminal of the diode is connected to the digital ground through the resistor. The protective circuit has simple structure, skillfully uses the combination of the diode and the resistor, effectively prevents a connection control source chip from being damaged by transient reverse current, enhances the system robustness, ensures the control effectiveness of outputting low level by a TTL (Transistor-Transistor Logic) level control source chip, and successfully solves the technical difficulties which are hard to overcome for a long time in the on-board control circuit field.

Description

technical field [0001] The invention relates to a control circuit design technology, in particular to a protection circuit for enhancing the robustness of a control interface circuit. Background technique [0002] The discrete output interface circuit is a necessary functional circuit in the embedded aviation airborne computer. Its main functions include two aspects: 1. Indicating the working state of the computer itself; 2. Controlling the working state of the target device. The drive output of the discrete output interface can usually be realized by using photoelectric isolation, electromagnetic relay, and power tube. However, due to the large size of these components, it is not suitable to use when there are too many drive output interfaces and the circuit board space is limited. Darlington tubes with high integration can meet the requirements of design factors such as space, quantity, and driving capacity (such as SG2823, see chip structure figure 1 ). The Darlington t...

AI Technical Summary

Problems solved by technology

Failure to connect according to the above requirements will result in abnormal performance or damage to the output port of the TTL level control source

Pay attention to the internal circuit provided by the chip 2823 manual (see figure 1 , figure 2 ): There is a diode between the 'ground' terminal and the TTL control input terminal. Obviously, when the "28V ground" level of the chip 2823 is higher than the output level of the TTL level control source, there will be current flowing to the TTL circuit. The output terminal of the level control source, thus causing the output port of the TTL level control source to fail

The common ground connection ensures that the 28V ground and the digital ground are in an equipotential state, and the separation of the two "grounds" cannot ensure the same potential, which will increase the probability of circuit damage

The assembly environment of the product on the machine is complex. During the disassembly process, it is inevitable that the ground wire is not connected or the ground wire is improperly connected, or the abnormality of the common ground connection on the machine affects the normal common ground, which may cause the discrete output interface. Fault

After the products are delivered in batches for installation and use, such failures occur frequently, which increases the maintenance cost of the products

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