CN203617985U - Digital interface circuit for 'ground/ON' discrete signal isolation conversion - Google Patents

Abstract

The utility model provides a "ground/on" discrete signal isolation conversion digital interface circuit, comprising: the negative end of the third diode (VD3) is connected with the discrete input signal, the positive end of the third diode (VD3) is respectively Connect to the lower end of the first capacitor (C1), the lower end of the second resistor (R2) and the negative input of the photocoupler (B1); the 28V power supply is connected to the front end of the first resistor (R1) of the filter circuit, and the first resistor (R1) The back end of the first capacitor (C1) is connected to the upper end of the second resistor (R2) and the positive end of the input of the photocoupler (B1); the emitter of the transistor of the photocoupler (B1) is connected to the digital ground, and the photocoupler The collector of the triode of the device (B1) is connected to the output end of the circuit and the lower end of the third resistor (R3), and the upper end of the third resistor (R3) is connected to the VCC digital power supply; the positive end of the first diode (VD1) is connected to the first Resistor (R1) rear end.

Description

"Ground/Open" discrete signal isolation conversion digital interface circuit

technical field

The utility model relates to a digital interface circuit for converting "ground/open" external discrete signals into TTL levels, which is widely used in various computer application fields in aircraft control systems and airborne electromechanical systems.

Background technique

The flight control computer and the electromechanical management computer, as important components of the aircraft, need to receive a large number of various sensor signals for calculation and processing, logical judgment and issue various instructions through the CPU, so as to realize the functions of automatic flight and comprehensive control of the aircraft.

The power supply used on the aircraft is 28V DC power supply, so most of the "ground/on" external discrete input signals are "28V ground/on", and its signal attributes are: true state: -3.5V～+3.5V; false state : Open circuit (open circuit impedance greater than 1 megohm is considered an open circuit). The characteristic of these "ground/open" external discrete signals is that the 28V uses the primary power supply on the aircraft, and the primary power supply is the main power supply for all electrical equipment on the aircraft, so there are many complex components between the primary power supply and the ground. Signals are likely to increase the bit error rate of the interface, so the 28V ground must be effectively isolated from the computer ground to ensure the safe and reliable operation of the computer. In order to improve mission reliability, safety and maintainability, the input threshold is increased, the anti-jamming function is added, and the BIT (self-test) design is specially added.

Utility model content

The purpose of this utility model is to propose a "ground/open" discrete signal isolation conversion digital interface circuit, which has anti-interference, low power consumption and isolation functions, and can BIT self-test. Solve the problem of interference and heating of the computer by the power supply on the 28V machine, improve the correctness of the circuit, improve the quality of computer acquisition, and reduce the occurrence of bit error rates.

The technical solution adopted by the utility model is, a "ground/open" discrete signal isolation conversion digital interface circuit, including:

The negative end of the third diode (VD3) is connected to the discrete input signal, and the positive end of the third diode (VD3) is respectively connected to the lower end of the first capacitor (C1), the lower end of the second resistor (R2) and the photocoupler (B1) Negative terminal of input; 28V power supply is connected to the front end of the first resistor (R1) of the filter circuit, and the back end of the first resistor (R1) is respectively connected to the upper end of the first capacitor (C1) and the upper end of the second resistor (R2) and the positive terminal of the photocoupler (B1) input; the emitter of the triode of the photocoupler (B1) is connected to the digital ground, and the collector of the triode of the photocoupler (B1) is connected to the output terminal of the circuit and the third resistor (R3 ) lower end, the third resistor (R3) is terminated with VCC digital power supply;

The positive terminal of the first diode (VD1) is connected to the rear end of the first resistor (R1), the negative terminal of the first diode (VD1) is connected to the first set of contacts of the first relay (K1), and the first relay ( The normally open point of the first group of K1) is connected to 28V ground, and the normally closed point of the first group of the first relay (K1) is suspended; the positive terminal of the second diode (VD2) is connected to the third diode (VD3) The positive terminal of the second diode (VD2) is connected to the second group of contacts of the first relay (K1), the normally open point of the second group of the first relay (K1) is connected to 28V ground, the first relay The normally closed point of the second group of (K1) is suspended; the BIT enable low excitation signal (BIT_EN_L) is connected to one end of the coil of the first relay (K1) and the positive end of the fifth diode (VD5), and the first relay (K1 ) The other end of the coil is connected to +5V and the negative end of the fifth diode (VD5);

The negative terminal of the first diode (VD1) is connected to the first group of contacts of the second relay (K2), and the normally open and normally closed points of the first group of the second relay (K2) are suspended; the second diode The negative terminal of (VD2) is connected to the second group of contacts of the second relay (K2), the normally closed point of the second group of the second relay (K2) is suspended, and the normally open point of the second group of the second relay (K2) Connect to 28V ground; BIT enables high excitation signal (BIT_EN_H) to connect one end of the coil of the second relay (K2) and the positive end of the fourth diode (VD4), and connect the other end of the coil of the second relay (K2) to positive 5V and The negative terminal of the fourth diode (VD4).

The utility model has the advantages and beneficial effects: the circuit design of the utility model utilizes the photoelectric characteristics of the light-emitting diode in the photocoupler and the shunting principle of the resistance, so that when the discrete input signal is in the range of -3.5V to +3.5V, the light-emitting diode When the current flows and emits light, the light emitted by the light-emitting diode shines on the base of the triode to turn on the triode, and the output of the triode is low; when the discrete input signal is open, the light-emitting diode is cut off without current, and the triode will also be cut off. The output voltage of the pull-up power supply is high level. In order to improve the reliability of the circuit, a filter circuit (R1 and C1), a shunt circuit (R2), and a reverse protection (VD3) are added, and a self-detection circuit—BIT input circuit (VD1 and VD2) and a BIT excitation control circuit ( K1, K2, VD4 and VD5), used to check the correctness of the circuit before flight to ensure flight safety.

Description of drawings

Fig. 1 is a schematic diagram of an interface circuit for converting one "ground/open" discrete signal into a digital signal of the present invention.

Fig. 2 is a circuit schematic diagram of the utility model applying low excitation to the interface circuit for converting "ground/open" discrete signals into digital signals under BIT conditions.

Fig. 3 is a schematic circuit diagram of the utility model applying high excitation to the interface circuit that converts the "ground/open" discrete signal into a digital signal under the BIT condition.

Fig. 4 is a schematic diagram of an interface circuit for converting the existing basic "ground/on" discrete signal into a digital signal.

Detailed ways

The power supply on the aircraft is 28V DC power supply, so most of the "ground/on" external discrete input signals are "28V ground/on", and its signal attributes are: true state: -3.5V～+3.5V; false state: Open circuit (open circuit impedance greater than 1 megohm is considered an open circuit). The interface circuit for converting the "28V ground/on" discrete signal into a digital signal in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention.

The present invention provides an interface circuit for converting "ground/open" discrete signals into digital signals. Referring to Figures 1 to 3, the circuit relationship is as follows:

The negative end of the third diode VD3 is connected to the discrete input signal, and the positive end of the third diode VD3 is respectively connected to the lower end of the first capacitor C1, the lower end of the second resistor R2 and the negative end of the photocoupler B1 input; 28V power supply Connected to the front end of the first resistor R1 of the filter circuit, the rear end of the first resistor R1 is respectively connected to the upper end of the first capacitor C1, the upper end of the second resistor R2 and the positive end of the input of the photocoupler B1; the emission of the triode of the photocoupler B1 The pole is connected to the digital ground, the collector of the triode of the photocoupler B1 is connected to the output end of the circuit and the lower end of the third resistor R3, and the upper end of the third resistor R3 is connected to the VCC digital power supply;

The positive terminal of the first diode VD1 is connected to the rear end of the first resistor R1, the negative terminal of the first diode VD1 is connected to the first group of contacts of the first relay K1, and the first group of normally open points of the first relay K1 Connect to 28V ground, the normally closed point of the first group of the first relay K1 is suspended; the positive terminal of the second diode VD2 is connected to the positive terminal of the third diode VD3, and the negative terminal of the second diode VD2 is connected to the first The second group of contacts of the relay K1, the normally open point of the second group of the first relay K1 is connected to 28V ground, the normally closed point of the second group of the first relay K1 is suspended; the BIT enable low excitation signal BIT_EN_L is connected to the first relay One end of the coil of K1 and the positive end of the fifth diode VD5, the other end of the coil of the first relay K1 is connected to +5V and the negative end of the fifth diode VD5;

The negative terminal of the first diode VD1 is connected to the first group of contacts of the second relay K2, and the normally open and normally closed points of the first group of the second relay K2 are suspended; the negative terminal of the second diode VD2 is connected to the first group of contacts. The second group of contacts of the second relay K2, the normally closed point of the second group of the second relay K2 is suspended, the normally open point of the second group of the second relay K2 is connected to 28V ground; the BIT enable high excitation signal BIT_EN_H is connected to the second One end of the coil of the relay K2 is connected to the positive end of the fourth diode VD4, and the other end of the coil of the second relay K2 is connected to positive 5V and the negative end of the fourth diode VD4.

The "ground/open" discrete signal provided by the present invention is converted into an interface circuit of a digital signal, and its working principle is as follows:

As shown in Figure 4, it is an interface circuit for converting a basic "ground/on" discrete signal into a digital signal. When the discrete input signal is 2V lower than the 28V power supply, the internal light-emitting diode will flow and emit light. The photoelectric characteristics of the light-emitting diode in the photocoupler (B1), the light emitted by the light-emitting diode is irradiated on the base of the phototransistor to make the phototransistor conduct, and the output of the phototransistor is low; when the discrete input signal is open, the light-emitting diode has no current When it is cut off, the phototransistor will also be cut off, and the output voltage of the phototransistor is a high level for the pull-up power supply;

As shown in Figure 1, on the basis of the basic type, in order to make the output of the optocoupler low when the discrete input signal is in the range of -3.5V to +3.5V, it is specially connected to the input terminal of the optocoupler (B1) A resistor (R2) is added to increase the threshold of discrete input through the voltage division and shunt function of the resistor; in order to improve the anti-interference ability of the circuit, a filter circuit (R1 and C1) and a reverse protection diode (VD3) are added.

As shown in Figure 2, when the BIT enable low excitation signal is at low level, the two sets of contacts of the relay (K1) act together, and the two contacts are respectively connected to the normally open point, and the BIT1 and BIT2 network point levels are both 0V , the input of the optocoupler (B1) is 0V, and the output of the phototransistor is high.

As shown in Figure 3, when the BIT enable high excitation signal is low level, the two sets of contacts of the relay (K2) act together, the contacts are connected to the normally open point, BIT1 is suspended, BIT2 is 0V, and the input of the photocoupler is both It is 28V, and the phototransistor output is low level.

In view of the high reliability of the aircraft, the filter circuit with anti-jamming function is added, and the discrete input circuit self-test function is added, that is, under the BIT chain condition, the computer CPU sends out the BIT command (BIT-EN-H, BIT-EN-L) , add different BIT excitation signals to the discrete input circuit through the relays K1 and K2, so as to fully test the function and performance of the computer interface circuit, which is beneficial to increase the fault detection ability and fault tolerance of the system.

Because the aircraft contains a large number of sensors, the computer will receive a large number of discrete signals. The circuit provided by the utility model is convenient to be integrated into an interface unit of 8 channels, and the BIT excitation control circuit (K1, K2, VD4 and VD5) can be simultaneously Multiple groups of such interface units ("ground/open" discrete signal isolation conversion digital interface circuits) provide BIT input excitation signals. The low power consumption design greatly reduces the power consumption of the power supply for a large number of discrete signal acquisition processes;

In addition, in view of the characteristics of discrete signals, there is no high requirement for resistive capacitance devices in the interface circuit.

The circuit of the utility model has been practically applied in the interface circuit of many subjects, and the performance index meets the needs of various computers.

Claims (1)

1. "/open " a discrete signal isolation converting digital interface circuit, it is characterized in that, comprising:

The negative terminal of the 3rd diode (VD3) is connected with discrete input signal, and the anode of the 3rd diode (VD3) is received respectively the negative terminal of the first electric capacity (C1) lower end, the second resistance (R2) lower end and photoelectrical coupler (B1) input; 28V power supply is received the first resistance (R1) front end of filter circuit, and the anode of the first electric capacity (C1) upper end, the second resistance (R2) upper end and photoelectrical coupler (B1) input is received respectively in the rear end of the first resistance (R1); The emitter of the triode of photoelectrical coupler (B1) connects digitally, and the collector electrode of the triode of photoelectrical coupler (B1) connects output and the 3rd resistance (R3) lower end of this circuit, the upper termination VCC digital power of the 3rd resistance (R3);

Positive termination the first resistance (R1) rear end of the first diode (VD1), the negative terminal of the first diode (VD1) connects first group of contact of the first relay (K1), connect 28V ground the normal battle of first group of the first relay (K1), the normally closed point of first group of the first relay (K1) is unsettled; The anode of positive termination the 3rd diode (VD3) of the second diode (VD2), the negative terminal of the second diode (VD2) connects second group of contact of the first relay (K1), connect 28V ground the normal battle of second group of the first relay (K1), the normally closed point of second group of the first relay (K1) is unsettled; BIT enables low pumping signal (BIT_EN_L) and connects coil one end of the first relay (K1) and the anode of the 5th diode (VD5), another termination+5V of coil of the first relay (K1) and the negative terminal of the 5th diode (VD5);

The negative terminal of the first diode (VD1) connects first group of contact of the second relay (K2), and the normal battle of first group and the normally closed point of the second relay (K2) are unsettled; The negative terminal of the second diode (VD2) connects second group of contact of the second relay (K2), and the normally closed point of second group of the second relay (K2) is unsettled, connects 28V ground the normal battle of second group of the second relay (K2); BIT enables high pumping signal (BIT_EN_H) and connects coil one end of the second relay (K2) and the anode of the 4th diode (VD4), the positive 5V of another termination of coil of the second relay (K2) and the negative terminal of the 4th diode (VD4).

Images