Digital quantity input circuit

Abstract

The utility model relates to the technical field of power electronics, in particular to a digital quantity input circuit, which comprises a direct-current power supply VCC15, a direct-current power supply VCC, a resistor R1, a voltage-regulator tube D2, a resistor R2, a triode Q1, a resistor R3, a resistor R4, a photoelectric coupler O1, a low-pass filtering module, a reference terminal voltage 110GND and a digital ground DGND. According to the utility model, the current passes through the resistor R1, the voltage-regulator tube D2, the resistor R2 and the triode Q1, so that the base current of the triode Q1 is increased to a certain degree, and the triode Q1 reaches the condition of saturated conduction. At the moment, the base current of the triode Q1 generally does not reach 1mA, the current flows through the resistor R1, and the generated heat is low, so that the heating degree of the resistor can be effectively reduced, and the total heating value of the whole circuit board is well controlled.

Description

Technical Field

[0001] This utility model relates to the field of power electronics technology, and more specifically, to a digital input circuit. Background Technology

[0002] In the rail transit field, 110VDC power supply is widely used in conventional trains, high-speed trains, and urban rail trains. Many electromechanical devices on these trains, such as the door system, typically use 110VDC voltage levels for their digital input signals. Some of these digital input signals cross multiple carriages, such as door opening and closing signals, directly affecting the control logic of the electromechanical equipment. However, these signals may be subject to various electromagnetic interferences during transmission across carriages. If the controller erroneously detects these digital signals, it could potentially cause serious consequences. Therefore, the detection of these digital signals places high demands on the system. In existing digital input circuits, I1 is the external input signal, which passes through power resistor R1, ceramic capacitor C1, the LED side of optocoupler O1, and finally returns to the 110VDC reference ground. Diode D1 prevents voltage breakdown of the unidirectional optocoupler's LED when the signal is reverse-connected. Resistor R2 is a pull-up resistor, and resistor R3 and ceramic capacitor C2 form a low-pass filter to filter the input signal. If sufficient current flows through the LED side of the optocoupler, the transistor side of the optocoupler conducts, and the I1_CPU signal output is low; if no current flows through the LED side of the optocoupler, the transistor side is cut off, and the I1_CPU signal output is high. The I1_CPU signal is connected to the CPU's I / O port, and the CPU reads this input signal. However, when a 110VDC signal is continuously input externally, the power resistor will heat up significantly, thus affecting the normal operation of the circuit.

[0003] Existing technology discloses a digital input circuit and device. This digital input circuit includes a first port and a second port as input terminals; a reverse voltage divider module connected between the first and second ports, comprising a first voltage divider circuit and a second voltage divider circuit connected in parallel; a rectifier module having a first pin and a third pin as inputs, and a second pin and a fourth pin as outputs; the first pin of the rectifier module is connected to the output terminals of the first and second voltage divider circuits, and the third pin is connected to the second port; an isolation output module has two input terminals connected between the second and fourth pins of the rectifier module, isolating the electrical signal output by the rectifier module before outputting it through its two output terminals. However, this circuit still suffers from the problem that when a continuous 110VDC signal is input externally, the power resistor heats up severely, affecting the normal operation of the circuit. Utility Model Content

[0004] The purpose of this invention is to publicly disclose a digital input circuit with lower heat generation.

[0005] To achieve the above objectives, this utility model provides a digital input circuit, comprising:

[0006] The circuit consists of a DC power supply VCC_15, a DC power supply VCC, a resistor R1, a Zener diode D2, a resistor R2, a transistor Q1, a resistor R3, a resistor R4, an optocoupler O1, a low-pass filter module, a reference voltage 110_GND, and digital ground DGND. One end of resistor R1 serves as the signal input terminal, and the other end of resistor R1 is connected to the cathode of Zener diode D2. One end of resistor R2 is connected to the anode of Zener diode D2, and the other end of resistor R2 is connected to the reference voltage 110_GND. The base of transistor Q1 is connected to the cathode of Zener diode D2, and the emitter of transistor Q1 is connected to the reference voltage 110_GND. Connect the transistor Q1 to GND. Connect the collector of transistor Q1 to optocoupler O1. Connect one end of optocoupler O1 to the collector of transistor Q1 and resistor R3 respectively. Connect the other end of optocoupler O1 to the low-pass filter module and digital ground DGND respectively. Connect one end of resistor R3 to DC power supply VCC_15. Connect the other end of resistor R3 to optocoupler O1. Connect one end of resistor R4 to DC power supply VCC and the other end to low-pass filter module. Connect one end of low-pass filter module to resistor R4 and optocoupler O1 respectively. Connect the other end of low-pass filter module to digital ground DGND.

[0007] Furthermore, it also includes: a varistor V1, one end of which serves as a signal input terminal, and the other end of which is connected to the reference terminal voltage 110_GND.

[0008] Furthermore, it also includes: capacitor C1 and capacitor C2, one end of capacitor C1 serves as the signal input terminal, and the other end of capacitor C1 is connected to capacitor C2 and the metal casing of the device respectively; one end of capacitor C2 is connected to capacitor C1 and the metal casing of the device respectively, and the other end of capacitor C2 is connected to the reference terminal voltage 110_GND.

[0009] Furthermore, it also includes: diode D1, the cathode of diode D1 is connected to the other end of resistor R1, and the anode of diode D1 is connected to the reference terminal voltage 110_GND.

[0010] Furthermore, it also includes: capacitor C3, one end of which is connected to the other end of resistor R1, and the other end of capacitor C is connected to the reference terminal voltage 110_GND.

[0011] Furthermore, the optocoupler O1 includes an LED side and a transistor output side. The LED side of the optocoupler O1 is connected to the collector of the transistor Q1 and the resistor R3 respectively. The transistor output side of the optocoupler O1 is connected to the low-pass filter module and the digital ground DGND respectively.

[0012] Furthermore, the low-pass filter module includes: resistor R5 and capacitor C4. One end of resistor R5 is connected to resistor R4 and optocoupler O1 respectively, and the other end of resistor R5 is connected to capacitor C4. The other end of capacitor C4 is connected to digital ground DGND. The end of resistor R5 connected to capacitor C4 serves as the external output signal connection terminal.

[0013] Furthermore, resistor R1 is a power resistor, resistor R2 is a bias resistor, resistor R3 is a current-limiting resistor, and resistor R4 is a pull-up resistor.

[0014] Furthermore, the DC power supply VCC_15 is a 12VDC or 15VDC DC power supply, and the DC power supply VCC is a 5VDC or 3.3VDC DC power supply.

[0015] Furthermore, resistor R1 has a resistance of 100kΩ and a power of 1W; varistor V1 has a maximum continuous operating voltage of 150V, a varistor voltage of 180V, and a maximum clamping voltage of 320V; Zener diode D2 has a Zener voltage of 68V.

[0016] Compared with the prior art, the beneficial effects of this utility model's technical solution are:

[0017] In this invention, current flows through resistor R1, Zener diode D2, resistor R2, and transistor Q1, increasing the base current of transistor Q1 to a certain level, thus bringing transistor Q1 to saturation conduction. At this point, the base current of transistor Q1 generally does not reach 1mA. This current flowing through resistor R1 generates relatively little heat, effectively reducing the degree of resistor heating and thus controlling the total heat generation of the entire circuit board. Attached Figure Description

[0018] Figure 1 This is a digital input circuit diagram as described in Embodiment 1; Detailed Implementation

[0019] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the scope of this patent.

[0020] The technical solution of this utility model will be further described below with reference to the accompanying drawings and embodiments.

[0021] Example 1:

[0022] This embodiment provides, as follows: Figure 1The circuit shown includes: a DC power supply VCC_15, a DC power supply VCC, a resistor R1, a Zener diode D2, a resistor R2, a transistor Q1, a resistor R3, a resistor R4, an optocoupler O1, a low-pass filter module, a reference voltage 110_GND, and a digital ground DGND; one end of resistor R1 serves as the signal input terminal, and the other end of resistor R1 is connected to the cathode of the Zener diode D2; one end of resistor R2 is connected to the anode of the Zener diode D2, and the other end of resistor R2 is connected to the reference voltage 110_GND; the base of transistor Q1 is connected to the anode of the Zener diode D2, and the emitter of transistor Q1 is connected to the reference voltage 110_GND. The terminal voltage 110_GND is connected, and the collector of transistor Q1 is connected to optocoupler O1. One end of optocoupler O1 is connected to the collector of transistor Q1 and resistor R3 respectively, and the other end of optocoupler O1 is connected to the low-pass filter module and digital ground DGND respectively. One end of resistor R3 is connected to DC power supply VCC_15, and the other end of resistor R3 is connected to optocoupler O1. One end of resistor R4 is connected to DC power supply VCC, and the other end is connected to the low-pass filter module. One end of the low-pass filter module is connected to resistor R4 and optocoupler O1 respectively, and the other end of the low-pass filter module is connected to digital ground DGND.

[0023] In this embodiment, if a rated voltage of 110VDC is applied between the digital signal input terminal I1 and the reference terminal 110_GND, the current flows through resistor R1, Zener diode D2, resistor R2, and transistor Q1, causing transistor Q1 to conduct. By appropriately selecting the parameters of resistors R1, R2, and Zener diode D2, the base current of transistor Q1 is increased to a certain extent, thus achieving the saturation conduction condition of transistor Q1. At this time, the base current of transistor Q1 generally does not reach 1mA. This current flows through the current-limiting resistor R1 without generating high heat, thereby effectively reducing the heat generation of the power resistor and controlling the total heat generation of the entire circuit board. Since transistor Q1 is saturated and conducting, the DC power supply VCC_15 flows through resistor R3, optocoupler O1, and the collector and emitter of transistor Q1, finally returning to the common terminal 110_GND. Adjust the current-limiting resistor R3 according to the selected optocoupler O1 model to adjust the current flowing through the LED side of the optocoupler, so that the transistor output side is saturated and turned on.

[0024] Example 2:

[0025] This embodiment further discloses information based on Embodiment 1:

[0026] Furthermore, it also includes: a varistor V1, one end of which serves as a signal input terminal, and the other end of which is connected to the reference voltage 110_GND. The varistor V1 is used to protect against external spike pulse interference signals. When an external high-voltage spike pulse interference signal appears, the varistor V1 will conduct, reducing the spike pulse voltage transmitted to the subsequent stage.

[0027] Furthermore, it also includes capacitors C1 and C2. One end of capacitor C1 serves as the signal input terminal, and the other end of capacitor C1 is connected to both capacitor C2 and the metal casing of the device. One end of capacitor C2 is connected to both capacitor C1 and the metal casing of the device, and the other end of capacitor C2 is connected to the reference voltage 110_GND. Capacitors C1 and C2 are connected to the metal casing of the device, and the casing is connected to the earth grounding point EARTH to eliminate high-frequency common-mode interference signals.

[0028] Furthermore, it also includes: diode D1, with the cathode of diode D1 connected to the other end of resistor R1, and the anode of diode D1 connected to the reference voltage 110_GND. The function of diode D1 is to prevent voltage breakdown of the unidirectional optocoupler's LED when the signal is reversed.

[0029] Furthermore, it also includes: capacitor C3, one end of which is connected to the other end of resistor R1, and the other end of capacitor C3 is connected to the reference terminal voltage 110_GND.

[0030] Furthermore, the optocoupler O1 includes an LED side and a transistor output side. The LED side of the optocoupler O1 is connected to the collector of the transistor Q1 and the resistor R3 respectively. The transistor output side of the optocoupler O1 is connected to the low-pass filter module and the digital ground DGND respectively.

[0031] Furthermore, the low-pass filter module includes a resistor R5 and a capacitor C4. One end of resistor R5 is connected to resistor R4 and optocoupler O1 respectively, and the other end of resistor R5 is connected to capacitor C4. The other end of capacitor C4 is connected to digital ground DGND. The end where resistor R5 and capacitor C4 are connected serves as the external output signal connection terminal. It is used to filter out high-frequency interference signals.

[0032] Furthermore, resistor R1 is a power resistor, resistor R2 is a bias resistor, resistor R3 is a current-limiting resistor, and resistor R4 is a pull-up resistor.

[0033] In this embodiment, the voltage level of the digital signal input terminal I1 is 110VDC, and the reference terminal is 110_GND. If the voltage at the input terminal I1 is high enough, the current flows through resistor R1, Zener diode D2, resistor R2, and transistor Q1, and finally returns to the reference terminal 110_GND. On the transistor output side of optocoupler O1, resistor R4 is a pull-up resistor, and resistor R5 and ceramic capacitor C4 form a low-pass filter. The output I1_CPU signal will directly enter the CPU or internal circuitry. Varistor V1 is used to protect against external spike pulse interference signals. When an external high-voltage spike pulse interference signal appears, varistor V1 will conduct, reducing the spike pulse voltage transmitted to the subsequent stage. Capacitors C1 and C2 are connected to the metal casing of the device, and the casing is connected to the earth grounding point EARTH to eliminate high-frequency common-mode interference signals. The function of diode D1 is to prevent voltage breakdown of the unidirectional optocoupler's LED when the signal is reversed.

[0034] If a rated voltage of 110VDC is applied between the digital signal input terminal I1 and the reference terminal 110_GND, the current flows through resistor R1, Zener diode D2, resistor R2, and transistor Q1, turning on transistor Q1. By properly selecting the parameters of resistors R1, R2, and Zener diode D2, the base current of transistor Q1 can be increased to a certain extent, thus achieving the saturation conduction condition for transistor Q1. At this time, the base current of transistor Q1 generally will not reach 1mA. This current flows through the current-limiting resistor R1 without generating high heat, effectively reducing the heat generation of the power resistor and controlling the total heat generation of the entire circuit board. Because transistor Q1 is saturated and conducting, the power supply VCC_15 flows through the current-limiting resistor R3, the LED side of optocoupler O1, and the collector and emitter of transistor Q1, finally returning to the common terminal 110_GND. Adjust the current-limiting resistor R3 according to the selected optocoupler model O1 to adjust the current flowing through the LED side of the optocoupler, thus saturating and conducting the transistor output side. Resistor R5 and ceramic capacitor C4 form a low-pass filter to filter out high-frequency interference signals. Note that C4 should not be too large when the input signal frequency is high, otherwise the rising and falling edges of the signal waveform will be distorted.

[0035] Example 3:

[0036] This embodiment further discloses information based on Embodiment 2:

[0037] Furthermore, the DC power supply VCC_15 is a 12VDC or 15VDC DC power supply, and the DC power supply VCC is a 5VDC or 3.3VDC DC power supply.

[0038] Furthermore, resistor R1 has a resistance of 100kΩ and a power of 1W; varistor V1 has a maximum continuous operating voltage of 150V, a varistor voltage of 180V, and a maximum clamping voltage of 320V; Zener diode D2 has a Zener voltage of 68V.

[0039] In this embodiment, the voltage level of the digital signal input terminal I1 is 110VDC, and the reference terminal is 110_GND. If the voltage at the input terminal I1 is high enough, the current flows through resistor R1, Zener diode D2, resistor R2, and transistor Q1, and finally returns to the reference terminal 110_GND. On the transistor output side of optocoupler O1, resistor R4 is a pull-up resistor, and resistor R5 and ceramic capacitor C4 form a low-pass filter. The output I1_CPU signal will directly enter the CPU or internal circuitry. Varistor V1 is used to protect against external spike pulse interference signals. When an external high-voltage spike pulse interference signal appears, varistor V1 will conduct, reducing the spike pulse voltage transmitted to the subsequent stage. Capacitors C1 and C2 are connected to the metal casing of the device, and the casing is connected to the earth grounding point EARTH to eliminate high-frequency common-mode interference signals. The function of diode D1 is to prevent voltage breakdown of the unidirectional optocoupler's LED when the signal is reversed.

[0040] If a rated voltage of 110VDC is applied between the digital signal input terminal I1 and the reference terminal 110_GND, the current flows through resistor R1, Zener diode D2, resistor R2, and transistor Q1, turning on transistor Q1. By properly selecting the parameters of resistors R1, R2, and Zener diode D2, the base current of transistor Q1 can be increased to a certain extent, thus achieving the saturation conduction condition for transistor Q1. At this time, the base current of transistor Q1 generally will not reach 1mA. This current flows through the current-limiting resistor R1 without generating high heat, effectively reducing the heat generation of the power resistor and controlling the total heat generation of the entire circuit board. Because transistor Q1 is saturated and conducting, the power supply VCC_15 flows through the current-limiting resistor R3, the LED side of optocoupler O1, and the collector and emitter of transistor Q1, finally returning to the common terminal 110_GND. Adjust the current-limiting resistor R3 according to the selected optocoupler model O1 to adjust the current flowing through the LED side of the optocoupler, thus saturating and conducting the transistor output side. Resistor R5 and ceramic capacitor C4 form a low-pass filter to filter out high-frequency interference signals. Note that C4 should not be too large when the input signal frequency is high, otherwise the rising and falling edges of the signal waveform will be distorted.

[0041] In this embodiment, the power resistor R1 has a resistance of approximately 100kΩ and a power rating of 1W. The varistor V1 is used for overvoltage protection. Since the upper limit of the 110VDC power supply voltage for rail transit vehicles is 137.5V, the varistor V1 is selected with a maximum continuous operating voltage of 150V, a varistor voltage of 180V, and a maximum clamping voltage of 320V. The Zener diode D2 has a Zener voltage of 68V. If the hard-wired signal is interfered with by fast pulse groups or surge signals during transmission, these interference signals are applied between the input signal terminal I1 and 110_GND via spatial radiation coupling or conduction coupling. If the interference voltage reaches the operating value of the varistor V1, V1 will quickly conduct, limiting the voltage transmitted to the subsequent circuitry within a certain range. The power resistor R1 is located after the varistor V1. Compared to the resistance of the bias resistor R2 and the Zener diode D2 after they are turned on, the resistance of the power resistor R1 is very large. Therefore, a large portion of the interference signal voltage is distributed across resistor R1, resulting in a very low interference signal voltage transmitted to subsequent stages, which will not adversely affect the subsequent circuits. The low-pass filter circuit composed of resistor R1 and capacitor C3 also plays a role in filtering out interference signals. If the interference signal is applied between the input signal terminal I1 and the metal casing (EARTH) through spatial radiation coupling or conduction coupling, the interference signal will flow to EARTH through the safety Y capacitors C1 and C2, thus not affecting the subsequent stages of the circuit. In addition, unlike voltage-controlled devices such as MOSFETs, the bipolar transistor Q1 is a current-controlled device. The collector and emitter of the transistor can only conduct when the current flowing through the base reaches a certain limit, thus it has a certain degree of electromagnetic interference immunity.

[0042] If interference voltage is generated at the digital signal input terminal due to reasons such as a damaged signal cable, this interference signal will be applied between the input signal terminal I1 and 110_GND. In this embodiment, the Zener diode D2 has a Zener voltage of 68V. Due to the presence of Zener diode D2, current will only flow through the base of transistor Q1 when the interference signal exceeds approximately 70V, causing current to flow through the LED side of optocoupler O1. This, in turn, causes current to flow between the collector and emitter of the transistor side of optocoupler O1, resulting in a change in the output voltage of the optocoupler transistor. Under normal circumstances, interference voltage generated by electromagnetic interference or a damaged signal cable will not reach 70V. Therefore, this circuit has a certain degree of immunity to electromagnetic interference and virtual voltage interference caused by damaged cable insulation, and will not cause misinterpretation of digital input signals.

[0043] Obviously, the above embodiments of this utility model are merely examples for clearly illustrating this utility model, and are not intended to limit the implementation of this utility model. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the protection scope of the claims of this utility model.

Claims

1. A digital input circuit, characterized in that, include: The circuit consists of a DC power supply VCC_15, a DC power supply VCC, a resistor R1, a Zener diode D2, a resistor R2, a transistor Q1, a resistor R3, a resistor R4, an optocoupler O1, a low-pass filter module, a reference voltage 110_GND, and digital ground DGND. One end of resistor R1 serves as the signal input terminal, and the other end of resistor R1 is connected to the cathode of Zener diode D2. One end of resistor R2 is connected to the anode of Zener diode D2, and the other end of resistor R2 is connected to the reference voltage 110_GND. The base of transistor Q1 is connected to the anode of Zener diode D2, and the emitter of transistor Q1 is connected to the reference voltage 110_GND. Connect the transistor Q1 to GND. Connect the collector of transistor Q1 to optocoupler O1. Connect one end of optocoupler O1 to the collector of transistor Q1 and resistor R3 respectively. Connect the other end of optocoupler O1 to the low-pass filter module and digital ground DGND respectively. Connect one end of resistor R3 to DC power supply VCC_15. Connect the other end of resistor R3 to optocoupler O1. Connect one end of resistor R4 to DC power supply VCC and the other end to low-pass filter module. Connect one end of low-pass filter module to resistor R4 and optocoupler O1 respectively. Connect the other end of low-pass filter module to digital ground DGND.

2. The digital input circuit according to claim 1, characterized in that, Also includes: Varistor V1 has one end as a signal input terminal and the other end connected to the reference voltage 110_GND.

3. The digital input circuit according to claim 1, characterized in that, Also includes: Capacitors C1 and C2 are used. One end of capacitor C1 serves as the signal input terminal, and the other end of capacitor C1 is connected to capacitor C2 and the metal casing of the device. One end of capacitor C2 is connected to capacitor C1 and the metal casing of the device, and the other end of capacitor C2 is connected to the reference voltage 110_GND.

4. A digital input circuit according to claim 1, characterized in that, Also includes: Diode D1, the cathode of diode D1 is connected to the other end of resistor R1, and the anode of diode D1 is connected to the reference terminal voltage 110_GND.

5. A digital input circuit according to claim 1, characterized in that, Also includes: Capacitor C3, one end of capacitor C3 is connected to the other end of resistor R1, and the other end of capacitor C3 is connected to the reference voltage 110_GND.

6. A digital input circuit according to claim 1, characterized in that, The optocoupler O1 includes an LED side and a transistor output side. The LED side of the optocoupler O1 is connected to the collector of the transistor Q1 and the resistor R3 respectively. The transistor output side of the optocoupler O1 is connected to the low-pass filter module and the digital ground DGND respectively.

7. A digital input circuit according to claim 1, characterized in that, The low-pass filter module includes: resistor R5 and capacitor C4. One end of resistor R5 is connected to resistor R4 and optocoupler O1 respectively, and the other end of resistor R5 is connected to capacitor C4. The other end of capacitor C4 is connected to digital ground DGND. The end where resistor R5 and capacitor C4 are connected serves as the external output signal connection terminal.

8. A digital input circuit according to claim 1, characterized in that, Resistor R1 is a power resistor, resistor R2 is a bias resistor, resistor R3 is a current limiting resistor, and resistor R4 is a pull-up resistor.

9. A digital input circuit according to claim 1, characterized in that, DC power supply VCC_15 is a 12VDC or 15VDC DC power supply, and DC power supply VCC is a 5VDC or 3.3VDC DC power supply.

10. A digital input circuit according to claim 2, characterized in that, Resistor R1 has a resistance of 100kΩ and a power of 1W; varistor V1 has a maximum continuous operating voltage of 150V, a varistor voltage of 180V, and a maximum clamping voltage of 320V; Zener diode D2 has a Zener voltage of 68V.

Images