A digital output circuit

Abstract

The utility model discloses a digital quantity output circuit, including including: power input module is used for accessing system power voltage, voltage conversion circuit, its input end is connected with the output of power input module, is used for to power voltage is reduced pressure or pressure processing to provide the working voltage required by DO output circuit, DO output circuit, its power end is connected with the output of voltage conversion circuit, is used for realizing the output of digital quantity signal, current sampling and monitoring circuit, is connected in series in the main stem power supply path between power input module and DO output circuit, is used for to the main stem circuit current is sampled and monitors current state, when sampling current exceeds the preset value, to the external MCU output overcurrent signal, to shut off the output of DO output circuit through the control signal that MCU sent. The circuit simple structure adopts the building of discrete component, and can realize the large current carrying capacity, and its carrying capacity is completely dependent on the carrying capacity of the input power, is not limited by component.

Description

Technical Field

[0001] This utility model belongs to the technical field of digital circuits, and particularly relates to a digital output circuit. Background Technology

[0002] A common type of industrial I / O is the digital output module (DO module), which is widely used in various fields, such as the injection molding industry and the textile industry in manufacturing. The main industrial application of DO modules is to turn industrial control devices, such as relays, actuators, and various valves, on and off.

[0003] Standard industrial DO modules typically output 24V or 48V standard signals, and their load capacity varies depending on the application. Some DO modules also lack current monitoring functionality. Utility Model Content

[0004] The purpose of this invention is to provide a digital output circuit with a current monitoring DO circuit, which has a simple structure, a concise BOM, and low cost.

[0005] To solve the above problems, the technical solution of this utility model is as follows: A digital output circuit, comprising: Power input module, used to connect to the system power supply voltage; A voltage conversion circuit, whose input terminal is connected to the output terminal of the power input module, is used to step down or step up the supply voltage to provide the operating voltage required by the DO output circuit. The DO output circuit has its power supply terminal connected to the output terminal of the voltage conversion circuit, and is used to realize the output of digital signals. A current sampling and monitoring circuit is connected in series on the main power supply path between the power input module and the DO output circuit. It is used to sample the current of the main circuit and monitor the current status. When the sampled current exceeds a preset value, it outputs an overcurrent signal to the external MCU so that the output of the DO output circuit can be turned off by the control signal issued by the MCU.

[0006] According to one embodiment of the present invention, the current sampling and monitoring circuit includes a current sampling resistor, a voltage comparator, and a voltage reference component; One end of the current sampling resistor is connected to the output terminal of the power input module, and the other end is connected to the negative input terminal of the voltage comparator. One end of the voltage reference component is connected to the output terminal of the power input module, and the other end is connected to the positive input terminal of the voltage comparator; The voltage comparator compares the voltage at the negative input terminal with the reference voltage at the positive input terminal and outputs a level signal to the MCU.

[0007] According to one embodiment of the present invention, the voltage reference component includes a Zener diode, a first resistor, a second resistor, and a third resistor; The first resistor and the second resistor are connected in series and then connected in parallel across the Zener diode; One end of the third resistor is connected to the positive terminal of the Zener diode, and the other end is connected to a power supply. The negative terminal of the Zener diode is connected to the output terminal of the power input module, and the series connection point of the first resistor and the second resistor is connected to the positive input terminal of the voltage comparator.

[0008] According to one embodiment of the present invention, the current sampling resistor is connected in series with a current limiting resistor and then connected to the negative input terminal of the voltage comparator.

[0009] According to one embodiment of the present invention, the output terminal of the voltage comparator is connected to a pull-up resistor to stabilize the output level.

[0010] According to one embodiment of the present invention, the DO output circuit includes: The control signal terminal is used to receive digital control signals from the MCU. The first voltage terminal is boosted by the voltage conversion circuit to be higher than the supply voltage, so as to provide the gate drive voltage for the subsequent drive stage. The second voltage terminal serves as the main voltage to be output, and its voltage value determines the DO output level. The first transistor has its base connected to the control signal terminal via a first base current limiting resistor, its emitter grounded, and its collector connected to the first voltage terminal via a first collector load resistor. The base of the second transistor is connected to the collector of the first transistor via a second base current limiting resistor, the emitter is grounded, and the collector is connected to the first voltage terminal via a second collector load resistor. The first diode has its anode and cathode shorted together and connected to the collector of the second transistor; The anode of the second diode is connected to the collector of the second transistor, and the cathode is connected to the gate of the MOSFET. The gate voltage divider network includes a sixth resistor and a seventh resistor connected in series between the first voltage terminal and ground, and their common node is connected to the gate of the MOS transistor; A Zener diode is connected in parallel between the gate and source of the MOSFET to clamp the gate-source voltage. The MOS transistor has its drain connected to the second voltage terminal and its source grounded. When it is turned on, it outputs the voltage of the second voltage terminal as DO_Output, and when it is turned off, it makes DO_Output low. Specifically, when the control signal terminal is at a high level, the first transistor and the second transistor are turned on in sequence, pulling down the gate voltage of the MOS transistor to turn it off; when the control signal terminal is at a low level, the first transistor and the second transistor are turned off, and the first voltage terminal raises the gate voltage of the MOS transistor to above the conduction threshold through the gate voltage divider network, turning it on, thereby realizing the isolation control output of a small current digital signal to a large current main voltage.

[0011] According to one embodiment of the present invention, the voltage of the second voltage terminal is any one of 0 V, 12 V, 24 V, 30 V, and 48 V to adapt to different industrial digital signal standards.

[0012] According to one embodiment of the present invention, the high level of the control signal terminal is 3.3 V or 5 V to be compatible with the IO levels of different MCUs.

[0013] According to one embodiment of the present invention, the voltage regulation value of the Zener diode is selected to be less than the maximum gate-source rated voltage of the MOSFET, so as to protect the MOSFET from being overvoltage-damped.

[0014] Because of the adoption of the above technical solution, this utility model has the following advantages and positive effects compared with the prior art: A digital output circuit in one embodiment of this utility model includes: a power input module for connecting to the system power supply voltage; a voltage conversion circuit, whose input terminal is connected to the output terminal of the power input module, for stepping down or boosting the power supply voltage to provide the operating voltage required by the DO output circuit; a DO output circuit, whose power supply terminal is connected to the output terminal of the voltage conversion circuit, for outputting digital signals; and a current sampling and monitoring circuit, connected in series in the main power supply path between the power input module and the DO output circuit, for sampling the current of the main circuit and monitoring the current status. When the sampled current exceeds a preset value, an overcurrent signal is output to an external MCU, so that the output of the DO output circuit is shut off by a control signal issued by the MCU. This circuit has a simple structure, is built with discrete components, and can achieve a high current carrying capacity. Its carrying capacity depends entirely on the carrying capacity of the input power supply and is not limited by the components. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a digital output circuit in one embodiment of the present invention; Figure 2 This is a schematic diagram of a current sampling and monitoring circuit in one embodiment of the present invention; Figure 3 This is a schematic diagram of the DO output circuit in one embodiment of the present invention. Detailed Implementation

[0016] The digital output circuit proposed in this utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of this utility model will become clearer from the following description and claims.

[0017] This embodiment provides an industrial digital output circuit with power supply current sampling and monitoring functions. The circuit has a simple structure, is built with discrete components, and can achieve a large current carrying capacity. Its carrying capacity depends entirely on the carrying capacity of the input power supply and is not limited by the components.

[0018] Please refer to Figure 1 The digital output circuit includes: a power input module for connecting to the system power supply voltage; The voltage conversion circuit, whose input terminal is connected to the output terminal of the power input module, is used to step down or step up the supply voltage to provide the operating voltage required by the DO output circuit. The DO output circuit has its power supply terminal connected to the output terminal of the voltage conversion circuit, and is used to realize the output of digital signals. The current sampling and monitoring circuit is connected in series on the main power supply path between the power input module and the DO output circuit. It is used to sample the current of the main circuit and monitor the current status. When the sampled current exceeds the preset value, it outputs an overcurrent signal to the external MCU, so that the output of the DO output circuit can be turned off by the control signal issued by the MCU.

[0019] The power input module and voltage conversion circuit in this digital output circuit both use existing conventional technologies. The innovation of this digital output circuit lies in the current sampling and monitoring circuit and the DO output circuit. The two circuits will be introduced in detail below.

[0020] Please refer to Figure 2 The current sampling and monitoring circuit includes a current sampling resistor R8, a voltage comparator U29, and a voltage reference component. One end of the current sampling resistor R8 is connected to the output terminal of the power input module, and the other end is connected to the negative input terminal of the voltage comparator U29. One end of the voltage reference component is connected to the output terminal of the power input module, and the other end is connected to the positive input terminal of the voltage comparator U29. The voltage comparator U29 compares the voltage at the negative input terminal with the reference voltage at the positive input terminal and outputs a level signal to the MCU.

[0021] The current sampling resistor R8 is a high-power, low-resistance precision resistor, such as 5mΩ / 2W / 1%. The sampled current is converted into a voltage signal and input to the negative input terminal (mV level voltage) of the voltage comparator (U29).

[0022] This embodiment uses a precision sampling resistor to sample the main current and transmits the monitoring results to the MCU through a voltage comparator to monitor the supply current. When the current exceeds a preset threshold, the MCU shuts off the DO output and disconnects the connection with the load.

[0023] Furthermore, the voltage reference component includes a Zener diode U5, a first resistor R42, a second resistor R91, and a third resistor R40. The first resistor R42 and the second resistor R91 are connected in series and then in parallel across the Zener diode U5. One end of the third resistor R40 is connected to the anode of the Zener diode U5, and the other end is connected to a power supply. The cathode of the Zener diode U5 is connected to the output terminal of the power input module, and the series connection point of the first resistor R42 and the second resistor R91 is connected to the positive input terminal of the voltage comparator.

[0024] U5, along with R42, R91, and R40, together form the reference voltage (mV level) at the positive input of the comparator. The voltage at the negative input of the comparator, which is being sampled, is compared with the reference voltage at the positive input. If V+ is greater than V-, the comparator outputs a high level; if V- is greater than V+, the comparator outputs a low level. This high and low level signal is directly sent to the MCU. When V- is greater than V+, it indicates that the sampled current in the main circuit exceeds the threshold current corresponding to the originally set reference voltage V+. Therefore, when the MCU detects a low level output from the comparator, it indicates an overcurrent in the circuit, and the MCU outputs a DO control signal to turn off the DO output.

[0025] Furthermore, the current sampling resistor is connected in series with a current-limiting resistor R41 and then connected to the negative input terminal of the voltage comparator. The output terminal of the voltage comparator U29 is connected to a pull-up resistor R92 to stabilize the output level.

[0026] Figure 2 The POWER_TO_DO (24V in the example) can be a standard industrial digital signal such as 0V, 24V, or 48V, or a non-standard signal such as 12V or 30V, which can be flexibly adapted according to the power supply of the system.

[0027] Please refer to Figure 3 The DO output circuit in this embodiment includes: The control signal terminal V3 is used to receive digital control signals from the MCU. The first voltage terminal V1 is boosted by the voltage conversion circuit to be higher than the supply voltage, so as to provide the gate drive voltage for the subsequent drive stage. The second voltage terminal V2 serves as the main voltage to be output, and its voltage value determines the DO output level. The first transistor Q1 has its base connected to the control signal terminal V3 via the first base current limiting resistor R1, its emitter grounded, and its collector connected to the first voltage terminal V1 via the first collector load resistor R2. The base of the second transistor Q2 is connected to the collector of the first transistor Q1 via the second base current limiting resistor R3, the emitter is grounded, and the collector is connected to the first voltage terminal V1 via the second collector load resistor R5. The anode and cathode of the first diode Q3 are shorted together and connected to the collector of the second transistor Q2; The anode of the second diode Q4 is connected to the collector of the second transistor Q2, and the cathode is connected to the gate of the MOSFET M1. The gate voltage divider network includes a sixth resistor R6 and a seventh resistor R7 connected in series between the first voltage terminal V1 and ground, and their common node is connected to the gate of the MOS transistor M1. Zener diode D2 is connected in parallel between the gate and source of MOSFET M1 to clamp the gate-source voltage; The drain of the MOSFET M1 is connected to the second voltage terminal V2, and the source is grounded. When it is turned on, it outputs the voltage of the second voltage terminal V2 as DO_Output, and when it is turned off, it makes DO_Output low. Specifically, when the control signal terminal V3 is high, the first transistor Q1 and the second transistor Q2 are turned on in sequence, pulling down the gate voltage of the MOSFET M1 to turn it off; when the control signal terminal V3 is low, the first transistor Q1 and the second transistor Q2 are turned off, and the first voltage terminal V1 raises the gate voltage of the MOSFET M1 above the conduction threshold through the gate voltage divider network, turning it on, thereby realizing the isolation control output of the small current digital signal to the large current main voltage.

[0028] The DO output circuit is built using low-cost resistors, transistors, and MOSFETs to achieve high-speed switching of large current with small current control, saving costs and simplifying the circuit BOM.

[0029] This DO output circuit is the first to employ two integrated transistors. One transistor is short-circuited between its collector and base, functioning as a conventional diode for control signal transmission. The other transistor is used as a conventional transistor to provide the gate-source voltage for the MOSFET in the subsequent circuit, enabling it to conduct. This approach saves on materials and components, simplifies the BOM, and reduces packaging and PCB space. Furthermore, the two transistors share the same temperature coefficient, which is superior to a combination of a single transistor and a single diode, thus improving circuit stability.

[0030] In this embodiment, a MOSFET (M1) is selected as the switch for the DO output. It uses a small current to control a large current, effectively isolates the control signal part and the load part, and can realize high-speed switching control, achieving efficient and safe DO output.

[0031] Specifically, V1 is the voltage output by the voltage conversion circuit for the DO output circuit. It is used to turn on the transistor Q1 and provide the turn-on voltage for the subsequent MOSFET. Its voltage must be increased by a certain voltage drop based on the supply voltage. The purpose is to make the MOSFET have a sufficient turn-on voltage drop and be fully turned on.

[0032] V3 is the control signal output by the analog microcontroller. V3 can be understood as the control signal of the microcontroller's output DO, which controls the output or disconnection of DO. Here it is represented by a 5V voltage, or 3.3V voltage, indicating that this is a digital signal.

[0033] V2 = POWER_TO_DO, the voltage of the main line, that is, the final output DO signal. In this embodiment, it is 24V, but it is not limited to 24V in practice.

[0034] R1, R2, R3: Their function is to provide a voltage divider to turn on the transistors, allowing Q1 and Q2 to conduct and operate as switches in the saturation region.

[0035] R5, R6, and R7: Their function is to provide the turn-on voltage for MOSFET M1.

[0036] Q3 and Q4 are a dual-diode device, which can be understood as the same chip containing two independent transistors. Here, the collector and base of Q3 are shorted, and it is used as a regular diode to save on BOM and space. Q4 operates in the cutoff region under normal conditions, and its function is to quickly turn off MOSFET M1 when power is off.

[0037] D2: Zener diode, which stabilizes the gate-source voltage of the MOSFET, i.e., the turn-on voltage, and protects the MOSFET M1. Its Zener voltage is selected to be less than the maximum gate-source rated voltage of the MOSFET M1 to protect the MOSFET from overvoltage breakdown.

[0038] M1: This is an N-channel MOSFET, used here as a switch. Its advantages include the ability to handle large currents, high-frequency switching operation, and effective isolation between the control circuit and the load circuit. The 5V input signal on the left is the control signal, effectively isolated from the 24V (POWER_TO_DO) signal, enabling small current to control large current. Compared to mechanical switches, it has a longer lifespan and faster speed.

[0039] This digital output circuit is based on the supply voltage. It raises the level and uses it for the DO output circuit, so as to effectively turn on the MOSFET. At the same time, it physically isolates the control circuit (MCU) from the DO output circuit, effectively protecting the MCU circuit and truly achieving isolated power supply.

[0040] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, if these changes fall within the scope of the claims of the present invention and their equivalents, they shall still fall within the protection scope of the present invention.

Claims

1. A digital output circuit, characterized in that, include: Power input module, used to connect to the system power supply voltage; A voltage conversion circuit, whose input terminal is connected to the output terminal of the power input module, is used to step down or step up the supply voltage to provide the operating voltage required by the DO output circuit. The DO output circuit has its power supply terminal connected to the output terminal of the voltage conversion circuit, and is used to realize the output of digital signals. A current sampling and monitoring circuit is connected in series on the main power supply path between the power input module and the DO output circuit. It is used to sample the current of the main circuit and monitor the current status. When the sampled current exceeds a preset value, it outputs an overcurrent signal to the external MCU so that the output of the DO output circuit can be turned off by the control signal issued by the MCU.

2. The digital output circuit as described in claim 1, characterized in that, The current sampling and monitoring circuit includes a current sampling resistor, a voltage comparator, and a voltage reference component; One end of the current sampling resistor is connected to the output terminal of the power input module, and the other end is connected to the negative input terminal of the voltage comparator. One end of the voltage reference component is connected to the output terminal of the power input module, and the other end is connected to the positive input terminal of the voltage comparator; The voltage comparator compares the voltage at the negative input terminal with the reference voltage at the positive input terminal and outputs a level signal to the MCU.

3. The digital output circuit as described in claim 2, characterized in that, The voltage reference component includes a Zener diode, a first resistor, a second resistor, and a third resistor; The first resistor and the second resistor are connected in series and then connected in parallel across the Zener diode; One end of the third resistor is connected to the positive terminal of the Zener diode, and the other end is connected to a power supply. The negative terminal of the Zener diode is connected to the output terminal of the power input module, and the series connection point of the first resistor and the second resistor is connected to the positive input terminal of the voltage comparator.

4. The digital output circuit as described in claim 2, characterized in that, The current sampling resistor is connected in series with a current-limiting resistor and then connected to the negative input terminal of the voltage comparator.

5. The digital output circuit as described in claim 2, characterized in that, The output of the voltage comparator is connected to a pull-up resistor to stabilize the output level.

6. The digital output circuit as described in claim 1, characterized in that, The DO output circuit includes: The control signal terminal is used to receive digital control signals from the MCU. The first voltage terminal is boosted by the voltage conversion circuit to be higher than the supply voltage, so as to provide the gate drive voltage for the subsequent drive stage. The second voltage terminal serves as the main voltage to be output, and its voltage value determines the DO output level. The first transistor has its base connected to the control signal terminal via a first base current limiting resistor, its emitter grounded, and its collector connected to the first voltage terminal via a first collector load resistor. The base of the second transistor is connected to the collector of the first transistor via a second base current limiting resistor, the emitter is grounded, and the collector is connected to the first voltage terminal via a second collector load resistor. The first diode has its anode and cathode shorted together and connected to the collector of the second transistor; The anode of the second diode is connected to the collector of the second transistor, and the cathode is connected to the gate of the MOSFET. The gate voltage divider network includes a sixth resistor and a seventh resistor connected in series between the first voltage terminal and ground, and their common node is connected to the gate of the MOS transistor; A Zener diode is connected in parallel between the gate and source of the MOSFET to clamp the gate-source voltage. The MOS transistor has its drain connected to the second voltage terminal and its source grounded. When it is turned on, it outputs the voltage of the second voltage terminal as DO_Output, and when it is turned off, it makes DO_Output low. Specifically, when the control signal terminal is at a high level, the first transistor and the second transistor are turned on in sequence, pulling down the gate voltage of the MOS transistor to turn it off; when the control signal terminal is at a low level, the first transistor and the second transistor are turned off, and the first voltage terminal raises the gate voltage of the MOS transistor above the conduction threshold through the gate voltage divider network to turn it on, thereby realizing the isolation control output of the small current digital signal to the large current main voltage.

7. The digital output circuit as described in claim 6, characterized in that, The voltage at the second voltage terminal is any one of 0 V, 12 V, 24 V, 30 V, or 48 V to adapt to different industrial digital signal standards.

8. The digital output circuit as described in claim 6, characterized in that, The high level of the control signal terminal is 3.3V or 5V to be compatible with the I / O levels of different MCUs.

9. The digital output circuit as described in claim 6, characterized in that, The voltage regulation value of the Zener diode is selected to be less than the maximum gate-source rated voltage of the MOSFET, so as to protect the MOSFET from being damaged by overvoltage.

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