Subway train digital quantity acquisition circuit
By introducing wet current control circuit into the digital acquisition circuit of subway trains, and using components such as current limiting resistor, optocoupler and NPN transistors, the output of high-precision and controllable wet current is achieved, solving the problems of small wet current and large power consumption, and meeting the acquisition needs of subway trains.
Patent Information
- Application Number
- CN202510291686.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-12
- Publication Date
- 2025-07-11
AI Technical Summary
The digital acquisition circuit of subway trains has problems such as small wet current, unstable wet current and large collection power consumption, which cannot meet the constant wet current requirements and heat dissipation needs.
A digital quantity acquisition circuit for subway trains is designed, combined with digital quantity acquisition circuit and wet current control circuit, and actively trigger the wet current control circuit through IN_CTR to form a controllable high-precision wet current, and the current control is achieved using components such as current limiting resistors, optocouplers, NPN transistors and controllable precision voltage stabilization sources.
Without reducing the sampling rate, the stability of wet current and the reduction of power consumption are achieved, meeting the wet current requirements and constant current requirements for digital acquisition of subway trains.
Smart Images
Figure CN120295265A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of control circuits in subway trains, and particularly to a digital quantity acquisition circuit for subway trains. Background Art
[0002] There are a large number of digital quantity acquisition circuits in subway trains. Considering the power consumption problem of the digital quantity acquisition circuit, the general acquisition current is designed to be about 1 mA. The digital quantities inside the vehicle are generally output by relays. In order to prevent the contacts of the relays from oxidizing, there is a requirement for wet current of the contacts, which is generally greater than 5 mA. If the digital quantity acquisition circuit is designed with an acquisition current of more than 5 mA, the power consumption of a single channel will increase sharply, and the heat dissipation requirement cannot be met. At the same time, in the current wet current circuit, when the voltage changes, the magnitude of the wet current will also change accordingly, and the requirement for a constant wet current cannot be met.
[0003] Among them, a conventional digital quantity acquisition circuit of a subway train is as Figure 1 shown. The circuit is composed of T1, D2, R1, D1, U1, and R2. The functions of each component and interface in the schematic diagram are as follows: IN is the external digital quantity voltage input terminal, generally the external input voltage of a subway vehicle, and V_GND is the ground of the external digital quantity voltage. T1 is a TVS diode for overvoltage protection, which performs voltage clamping when the circuit withstands overvoltage and pulls the voltage down to a fixed value for the protection of the interface circuit. D2 is a rectifier diode, which makes the current of the circuit can only be input from the IN terminal. R1 is a current limiting diode, generally limiting the conduction current to about 1 - 2 mA. D1 is a zener diode, which is used to set the conduction threshold voltage. U1 is an optocoupler, which optically isolates the input side and the output side. R2 is a pull-down resistor, and VCC3V3 is the DC 3.3 V power supply for the output terminal. OUT is the low-voltage output terminal, generally directly connected to the controller. When U1 is not conducting, OUT outputs 0, and after U1 conducts, OUT outputs DC 3.3 V. The digital quantity acquisition circuit of the subway train currently cannot meet the wet current requirement. In order to meet the wet current requirement and at the same time reduce the acquisition power consumption of the circuit, some digital quantity acquisition circuits of subway trains adopt a time-sharing acquisition strategy.
[0004] Although the time-sharing acquisition can meet the wet current requirement, since the circuit is in the off state most of the time, this will reduce the resolution of the digital quantity acquisition result, and at the same time, it is very difficult to ensure that an effective wet current can be obtained at the moment when the relay contact is opened. At the same time, in the current wet current circuit, when the voltage changes, the magnitude of the wet current will also change accordingly, and the requirement for a constant wet current cannot be met. Summary of the Invention
[0005] In view of the problems existing in the prior art, the present invention solves the problems of small and unstable wet current and high acquisition power consumption of the digital quantity acquisition circuit in the subway train without reducing the sampling rate. The specific technical solution is a digital quantity acquisition circuit for a subway train, including:
[0006] A digital quantity acquisition circuit for acquiring digital quantity signals on a subway train based on small current;
[0007] A wet current control circuit that is actively triggered by IN_CTR to form a controllable wet current when a wet current is required;
[0008] When the input voltage of the external digital quantity voltage input terminal IN is at a low level, the digital quantity acquisition circuit is not turned on, the low-voltage output terminal OUT outputs 0V, the digital quantity acquisition result is 0, IN_CTR is given 3.3V, and the wet current control circuit is not turned on;
[0009] When the IN input voltage is at a high level, the digital quantity acquisition circuit is turned on, the low-voltage output terminal OUT outputs 3.3V, and the digital quantity acquisition result is 1; IN_CTR is given 0V, the wet current control circuit is turned on to generate the required wet current. When the current output meets a certain time, IN_CTR is given 3.3V to turn off the wet current control circuit.
[0010] The digital quantity acquisition circuit includes a TVS diode T1 for overvoltage protection, a rectifier diode D2, a current-limiting diode R1, a voltage-regulating diode D1, an optocoupler U1, and a pull-down resistor R2. One end of the TVS diode T1 for overvoltage protection is grounded and the other end is connected to the rectifier diode D2. The rectifier diode D2 is connected to the current-limiting diode R1. The current-limiting diode R1 is connected to the voltage-regulating diode D1. The voltage-regulating diode D1 is connected to the input end of the optocoupler U1. The output end of the optocoupler U1 is connected to the pull-down resistor R2. The fourth pin of the output end of the optocoupler U1 is connected to the 3.3V power supply voltage, and the third pin of the output end of the optocoupler U1 is the output signal of the digital quantity acquisition circuit; when the circuit withstands overvoltage, the TVS diode T1 for overvoltage protection clamps the voltage to a fixed value for protecting the interface circuit, and the voltage-regulating diode D1 is used to set the conduction threshold voltage.
[0011] The wet current control circuit includes a current-limiting resistor R3, an optocoupler U2, a voltage-dividing resistor R5, an NPN transistor Q1, a precision voltage reference source D3, and a current-limiting resistor R4. One end of the current-limiting resistor R3 is connected to the control terminal IN_CTR of the wet current, and the other end is connected to the optocoupler U2. The third pin of the output terminal of the optocoupler U2 is connected to the voltage-dividing resistor R5. The first pin of the input terminal of the optocoupler U2 is connected to a 3.3V power supply voltage. The third pin of the output terminal of the optocoupler U2 is connected to the voltage-dividing resistor R5. One end of the voltage-dividing resistor R5 is connected to the base of the NPN transistor Q1 and is also connected to the precision voltage reference source D3. The emitter of the NPN transistor Q1 and the precision voltage reference source D3 are connected to the current-limiting resistor R4, and the other end of the current-limiting resistor R4 is grounded. The current-limiting resistor R3 is used to limit the input current of the optocoupler U2. The NPN transistor Q1 operates in the amplification region and is used for current setting and current bearing of the wet current circuit. When the circuit is turned on, the main wet current generated flows through the NPN transistor Q1. The voltage-dividing resistor R5 is used to bear the excess voltage across the precision voltage reference source D3. The voltage across the current-limiting resistor R4 is the reference voltage generated by the precision voltage reference source D3, and the current is the wet current of the circuit.
[0012] The current-limiting diode R1 limits the conduction current to 1 - 2 mA. The rectifier diode D2 is of the GS1010FL model, making the current of the circuit can only enter from the digital quantity voltage input terminal IN.
[0013] The TVS diode T1 for overvoltage protection is of the SMCJ36CA model, and the zener diode D1 is of the 1SMA4733 - 5.1V model. When the voltage is lower than 5.1V, the circuit will not conduct.
[0014] The optocouplers U1 and U2 are of the TLP183 model, which optically isolate the input side and the output side.
[0015] The NPN transistor Q1 is of the 2N3904 model, and the precision voltage reference source D3 is of the TLP431 model. When a positive power supply is applied to pins 2 and 1, pin 3 outputs a high-precision reference voltage of 2.5V.
[0016] Due to the adoption of the above technical solution, a digital quantity acquisition circuit for a subway train provided by the present invention, based on the mutual cooperation of the digital quantity acquisition circuit and the wet current control circuit, through the above circuit and control logic, can solve the problems of small wet current, unstable wet current, and large acquisition power consumption in the digital quantity acquisition circuit of the subway train without reducing the sampling rate. Description of the Drawings
[0017] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.
[0018] Figure 1 It is the circuit schematic diagram introduced in the background art;
[0019] Figure 2 It is the structure diagram of a digital quantity acquisition circuit for a subway train of the present invention;
[0020] Figure 3 It is a schematic diagram of an embodiment of a digital quantity acquisition circuit for a subway train of the present invention. Detailed implementation manners
[0021] To make the technical solutions and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention:
[0022] As Figure 1 shown, a digital quantity acquisition circuit for a subway train, the circuit includes a digital quantity acquisition circuit and a wet current control circuit; among them, the digital quantity acquisition circuit is the same as the conventional digital quantity acquisition circuit of the subway train, and can collect digital quantity signals of the subway train in real time with a relatively small current. In the case of needing wet current, the wet current control circuit can be actively triggered through IN_CTR to form a high-precision and controllable wet current.
[0023] When the IN input voltage is at a low level, the digital quantity acquisition circuit is not turned on, and the OUT terminal outputs 0V, that is, the digital quantity acquisition result is 0. When IN_CTR gives 3.3V, the wet current control circuit is not turned on.
[0024] When the IN input voltage is at a high level, the digital quantity acquisition circuit is turned on, and the OUT terminal outputs 3.3V, that is, the digital quantity acquisition result is 1. At this time, when IN_CTR gives 0V, the wet current control circuit is turned on to generate the required high-precision wet current. When the current output meets a certain time, IN_CTR gives 3.3V to turn off the wet current control circuit.
[0025] Further, the digital quantity acquisition circuit includes a TVS diode T1 for overvoltage protection, a rectifier diode D2, a current-limiting diode R1, a voltage-regulating diode D1, an optocoupler U1, and a pull-down resistor R2. One end of the TVS diode T1 for overvoltage protection is grounded and the other end is connected to the rectifier diode D2. The rectifier diode D2 is connected to the current-limiting diode R1. The current-limiting diode R1 is connected to the voltage-regulating diode D1. The voltage-regulating diode D1 is connected to the input end of the optocoupler U1. The output end of the optocoupler U1 is connected to the pull-down resistor R2. The fourth pin of the output end of the optocoupler U1 is connected to a 3.3V power supply voltage, and the third pin of the output end of the optocoupler U1 is the output signal of the digital quantity acquisition circuit.
[0026] The high level of the external digital quantity voltage input terminal IN is DC24V, and the low level is 0V. 24V_GND is the ground of the external digital quantity voltage. The model of the TVS diode T1 for overvoltage protection is SMCJ36CA, which performs voltage clamping when the circuit withstands overvoltage and pulls the voltage down to a fixed value of 36V for the protection of the interface circuit. The model of the rectifier diode D2 is GS1010FL, which enables the current of the circuit to only input from the IN terminal. The value of the current-limiting diode R1 is 20K, and the on-current of the acquisition circuit is limited to less than 1mA through this resistor, about 0.9mA in this circuit. The model of the voltage-regulating diode D1 is 1SMA4733-5.1V, which is used to set the conduction threshold voltage. When the voltage is lower than 5.1V, the circuit will not conduct. The model of the optocoupler U1 is TLP183, which performs optoelectronic isolation between the input side and the output side. The model of the pull-down resistor R2 is 4.7K ohms, and VCC3V3 is the DC3.3V power supply for the output terminal.
[0027] Further, the wet current control circuit includes a current-limiting resistor R3, an optocoupler U2, a voltage-dividing resistor R5, an NPN transistor Q1, a precision voltage regulator D3, and a current-limiting resistor R4. One end of the current-limiting resistor R3 is connected to the control terminal IN_CTR of the wet current, and the other end is connected to the optocoupler U2. The third pin of the output terminal of the optocoupler U2 is connected to the voltage-dividing resistor R5. The first pin of the input terminal of the optocoupler U2 is connected to the 3.3V supply voltage. The third pin of the output terminal of the optocoupler U2 is connected to the voltage-dividing resistor R5. One end of the voltage-dividing resistor R5 is connected to the base of the NPN transistor Q1 and is also connected to the precision voltage regulator D3. The emitter of the NPN transistor Q1 and the precision voltage regulator D3 are connected to the current-limiting resistor R4, and the other end of the current-limiting resistor R4 is grounded. Here, OUT is the low-voltage output terminal and is directly connected to the microcontroller. When the optocoupler U1 is not conducting, OUT outputs 0, and when the optocoupler U1 conducts, OUT outputs DC3.3V. IN_CTR is the control terminal of the wet current. When IN_CTR is given DC3.3V, the wet current control circuit fails, and when IN_CTR is given 0V, the wet current control circuit is effective. The value of the current-limiting resistor R3 is 1K ohm, which is used to limit the input current of the optocoupler. The model of the NPN transistor Q1 is 2N3904, which operates in the amplification region and is used for current setting and current bearing of the wet current circuit. When the circuit conducts, the main wet current generated passes through Q1. The value of the voltage-dividing resistor R5 is 10K ohm, which is used to bear the excess voltage across D3. The precision voltage regulator D3 can output a precise reference power supply, and its model is TLP431. When a positive power supply is applied to pins 2 and 1, pin 3 can output a high-precision reference voltage of 2.5V. The value of the current-limiting resistor R4 is 250 ohm, and the voltage across both ends of this resistor is the reference voltage of 2.5V generated by D3, that is, the wet current of this circuit is 2.5V / 250R = 10mA.
[0028] A digital quantity acquisition circuit for a subway train disclosed by the present invention has the following specific working logic:
[0029] When the input voltage of IN is DC24V, the digital quantity acquisition circuit conducts, and the conduction current of the acquisition circuit is less than 1mA. The OUT terminal outputs 3.3V, that is, the digital quantity acquisition result is 1. At this time, IN_CTR is given 0V, the wet current control circuit conducts, generating the required high-precision wet current. When the current output meets a certain time, IN_CTR is given 3.3V to disconnect the wet current control circuit.
[0030] A digital quantity acquisition circuit for a subway train disclosed by the present invention. The wet current control circuit comprises an optocoupler U2, an NPN triode Q1, a voltage-dividing resistor R5, a controllable precision voltage stabilizer D3, and a current-limiting resistor R4. The optocoupler U2 is used for the optoelectronic isolation of control signals and external signals. The NPN triode Q1 operates in the amplification region and is used for the current setting and current bearing of the wet current circuit. When the circuit is turned on, the main wet current generated all flows through the NPN triode Q1. The controllable precision voltage stabilizer D3 can output a precise reference power supply, and when a positive power supply is applied, it can output a high-precision reference voltage. The voltage-dividing resistor R5 is used to bear the redundant voltage across the controllable precision voltage stabilizer. The current-limiting resistor R4 is used to control the circuit current.
[0031] As described above, only the preferred specific embodiments of the present invention are provided, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered by the protection scope of the present invention.
Claims
1. A digital quantity acquisition circuit for a subway train, characterized in that Including: A digital quantity acquisition circuit for acquiring digital quantity signals on a subway train based on small current; A wet current control circuit, which is actively triggered by IN_CTR to form a controllable wet current when wet current is required; When the input voltage of the external digital quantity voltage input terminal IN is at a low level, the digital quantity acquisition circuit is not turned on, the low-voltage output terminal OUT outputs 0V, the digital quantity acquisition result is 0, IN_CTR gives 3.3V, and the wet current control circuit is not turned on; When the input voltage of IN is at a high level, the digital quantity acquisition circuit is turned on, the low-voltage output terminal OUT outputs 3.3V, and the digital quantity acquisition result is 1; IN_CTR gives 0V, the wet current control circuit is turned on to generate the required wet current. When the current output meets a certain time, IN_CTR gives 3.3V to turn off the wet current control circuit.
2. The digital quantity acquisition circuit of a subway train according to claim 1, characterized in that: The digital quantity acquisition circuit includes a TVS diode T1 for overvoltage protection, a rectifier diode D2, a current-limiting diode R1, a voltage-regulating diode D1, an optocoupler U1, and a pull-down resistor R2. One end of the TVS diode T1 for overvoltage protection is grounded and the other end is connected to the rectifier diode D2. The rectifier diode D2 is connected to the current-limiting diode R1. The current-limiting diode R1 is connected to the voltage-regulating diode D1. The voltage-regulating diode D1 is connected to the input end of the optocoupler U1. The output end of the optocoupler U1 is connected to the pull-down resistor R2. The fourth pin of the output end of the optocoupler U1 is connected to the 3.3V power supply voltage, and the third pin of the output end of the optocoupler U1 is the output signal of the digital quantity acquisition circuit; when the circuit withstands overvoltage, the TVS diode T1 for overvoltage protection clamps the voltage to a fixed value for protecting the interface circuit, and the voltage-regulating diode D1 is used to set the conduction threshold voltage.
3. The digital quantity acquisition circuit of a subway train according to claim 2, characterized in that: The wet current control circuit includes a current-limiting resistor R3, an optocoupler U2, a voltage-dividing resistor R5, an NPN transistor Q1, a controllable precision voltage regulator D3, and a current-limiting resistor R4. One end of the current-limiting resistor R3 is connected to the control end IN_CTR of the wet current and the other end is connected to the optocoupler U2. The third pin of the output end of the optocoupler U2 is connected to the voltage-dividing resistor R5. The first pin of the input end of the optocoupler U2 is connected to the 3.3V power supply voltage. The third pin of the output end of the optocoupler U2 is connected to the voltage-dividing resistor R5. One end of the voltage-dividing resistor R5 is connected to the base of the NPN transistor Q1 and is also connected to the controllable precision voltage regulator D3. The emitter of the NPN transistor Q1 and the controllable precision voltage regulator D3 are connected to the current-limiting resistor R4. The other end of the current-limiting resistor R4 is grounded; the current-limiting resistor R3 is used to limit the input current of the optocoupler U2. The NPN transistor Q1 operates in the amplification region for current setting and current bearing of the wet current circuit. When the circuit is turned on, the main wet current generated flows through the NPN transistor Q1. The voltage-dividing resistor R5 is used to bear the excess voltage across the controllable precision voltage regulator D3. The voltage across the current-limiting resistor R4 is the reference voltage generated by the controllable precision voltage regulator D3, and the current is the wet current of the circuit.
4. The digital quantity acquisition circuit of a subway train according to claim 2, wherein: The current-limiting diode R1 limits the conduction current to 1 - 2 mA. The rectifier diode D2 is of the GS1010FL model, enabling the current of the circuit to only input from the digital voltage input terminal IN.
5. The digital quantity acquisition circuit of a subway train according to claim 2, characterized in that: The TVS diode T1 for overvoltage protection is of the SMCJ36CA model, and the voltage-regulator diode D1 is of the 1SMA4733 - 5.1V model. When the voltage is lower than 5.1V, the circuit will not conduct.
6. The digital quantity acquisition circuit of a subway train according to claim 3, characterized in that: The optocouplers U1 and U2 are of the TLP183 model, providing optoelectronic isolation between the input side and the output side.
7. The digital quantity acquisition circuit of a subway train according to claim 3, characterized in that: The NPN transistor Q1 is of the 2N3904 model, and the controllable precision voltage reference source D3 is of the TLP431 model. After applying a positive power supply to pins 2 and 1, pin 3 outputs a high-precision reference voltage of 2.5V.