A circuit for switching CAN and DAC based on MOS switch

Abstract

The utility model discloses a kind of circuit based on MOS tube switch realization CAN and DAC switching, including MCU, electronic switch, heating module, temperature sampling module, calibration data storage module, CAN module and DAC module composition, the electronic switch is connected DAC module by DAC0 port, DAC1 port;The electronic switch is connected CAN module by CANH port, CANL port;The CAN module, DAC module connect MCU;The MCU is connected heating module, temperature sampling module, calibration data storage module respectively.The utility model aims at the problem that the CAN communication 2P interface of sensor and DAC output 2P interface share 2P output terminal conflict, will adopt electronic switch to realize two single-pole double-throw, and whether common terminal is connected to CAN communication interface or DAC output interface is selected by control signal.

Description

Technical Field

[0001] This utility model relates to the field of nitrogen and oxygen sensor technology, specifically a circuit based on MOS transistor switching to achieve CAN and DAC switching. Background Technology

[0002] Nitrogen oxide sensors are primarily used in the automotive industry to measure nitrogen and oxygen concentrations in engine exhaust, meeting the requirements of closed-loop control in engine aftertreatment systems and on-board diagnostic (OBD) systems. However, nitrogen oxide sensors also have industrial applications.

[0003] Due to different application scenarios, the output interfaces of nitrogen and oxygen sensors also differ. Compared to sensors used in the automotive industry, most industrial sensors do not use CAN communication, but instead use DAC output analog voltage or RS-485 communication. Therefore, a DAC circuit needs to be added to the nitrogen and oxygen sensors used in automobiles to represent the concentration of nitrogen and oxygen with an output voltage of 0-10V.

[0004] In automotive sensor manufacturing, product testing and calibration rely on CAN communication for data exchange. Therefore, a CAN communication interface is essential during the production phase. Consequently, both a CAN communication interface and a DAC output interface are required. However, adding two interface terminals to the existing circuit board necessitates adjustments to the sensor's structural components. This leads to lower product compatibility and repeatability, resulting in significant overall sensor modifications and increased costs. If the CAN communication interface is pre-installed on the circuit board, and the output terminal is changed to a DAC output, it was found that the industrial nitrogen oxide production process is incompatible with existing nitrogen oxide production procedures, making it unsuitable for mass production.

[0005] To address this, a circuit based on MOSFET switching to switch between CAN and DAC is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a circuit for switching between CAN and DAC based on a MOS transistor switch. To address the conflict between the CAN communication 2P interface and the DAC output 2P interface of the sensor sharing the same 2P output terminal, an electronic switch will be used to implement two single-pole double-throw circuits, and a control signal will be used to select whether the common terminal is connected to the CAN communication interface or the DAC output interface.

[0007] To achieve the above objectives, this utility model provides the following technical solution:

[0008] A circuit for switching between CAN and DAC based on a MOSFET switch comprises an MCU, an electronic switch, a heating module, a temperature sampling module, a calibration data storage module, a CAN module, and a DAC module. The electronic switch is connected to the DAC module through DAC0 port and DAC1 port.

[0009] The electronic switch is connected to the CAN module via the CANH port and the CANL port.

[0010] The CAN module and DAC module are connected to the MCU;

[0011] The MCU is connected to the heating module, the temperature sampling module, and the calibration data storage module, respectively.

[0012] Furthermore, the electronic switch includes two N-channel enhancement-mode field-effect transistors (X1, X2), and the two together constitute a selection control circuit.

[0013] Furthermore, the electronic switch includes two N-channel junction field-effect transistors (J1, J2), which together constitute a selection output circuit.

[0014] Furthermore, the N-channel junction field-effect transistor J1 is connected to the DAC0 port, and the N-channel junction field-effect transistor J2 is connected to the CANH port.

[0015] Furthermore, the electronic switch includes N-channel junction field-effect transistors (J3, J4), with the N-channel junction field-effect transistor J3 connected to the DAC1 port and the N-channel junction field-effect transistor J4 connected to the CANL port.

[0016] Furthermore, the MCU is connected to a DC-DC 5V module, and the DAC module is connected to a DC-DC 12V module.

[0017] Furthermore, the DC-DC 5V module and the DC-DC 12V module are connected to a reverse connection protection module.

[0018] Compared with the prior art, the beneficial effects of this utility model are:

[0019] 1. Minimal modifications and low cost; no changes are required beyond the circuit board, and no adjustments are needed to the production process.

[0020] 2. High flexibility; it can select between CAN communication and DAC output via control signals in different scenarios.

[0021] 3. Good compatibility: a single circuit board can be used for both automotive exhaust emission testing and industrial applications.

[0022] 4. Purely hardware implementation, stable and reliable. Control signals are controlled by external interface hardware, and no software changes are required. Attached Figure Description

[0023] Figure 1 This is a schematic diagram illustrating the principle and structure of this utility model;

[0024] Figure 2 This is a schematic diagram of the electronic switch structure of this utility model. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention.

[0026] Example 1:

[0027] Please see Figure 1-2 This utility model provides a technical solution:

[0028] A circuit for switching between CAN and DAC based on a MOSFET switch includes an MCU, an electronic switch, a heating module, a temperature sampling module, a calibration data storage module, a CAN module, and a DAC module. The electronic switch is connected to the DAC module through DAC0 and DAC1 ports, and the electronic switch is connected to the CAN module through CANH and CANL ports. The CAN module and DAC module are connected to the MCU.

[0029] Connect the MCU to the heating module, temperature sampling module, and calibration data storage module respectively. Connect the MCU to the DC-DC 5V module, the DAC module to the DC-DC 12V module, and connect the DC-DC 5V module and the DC-DC 12V module to the reverse connection protection module.

[0030] like Figure 2 As shown:

[0031] The electronic switch includes two N-channel enhancement-mode field-effect transistors (X1, X2), which together form a selection control circuit. The electronic switch also includes two N-channel junction field-effect transistors (J1, J2), which together form a selection output circuit. The N-channel junction field-effect transistor J1 is connected to the DAC0 port, and the N-channel junction field-effect transistor J2 is connected to the CANH port.

[0032] The electronic switch includes N-channel junction field-effect transistors (J3 and J4). N-channel junction field-effect transistor J3 is connected to the DAC1 port, and N-channel junction field-effect transistor J4 is connected to the CANL port.

[0033] Working principle:

[0034] The electronic switch uses a two-way single-pole double-throw design, connecting the DAC module output and the CAN module output to the corresponding electronic switch. By controlling the opening and closing of the switch, the DAC output or CAN communication can be achieved.

[0035] The circuit of the electronic switch mainly consists of two N-channel enhancement-mode field-effect transistors and two N-channel junction field-effect transistors, which respectively constitute the selection control circuit and the selection output circuit.

[0036] Two N-channel enhancement-mode MOSFETs (X1, X2) at the control terminal form the selection control circuit, and two N-channel junction field-effect transistors (J1, J2) at the output terminal form the selection output circuit. By controlling the voltage at the CON port of the control terminal, the output terminal controls whether it outputs from the DAC port or the CAN port. The N-channel junction field-effect transistor (J1) at the output terminal is connected to the DAC0 port, the N-channel junction field-effect transistor (J3) is connected to the DAC1 port, the N-channel junction field-effect transistor (J2) is connected to the CANH port, and the N-channel junction field-effect transistor (J4) is connected to the CANL port.

[0037] VCC represents a negative voltage. When the CON port is -VCC, the gate-source voltage difference of the N-channel enhancement-mode MOSFET X1 at the control terminal is equal to 0 and it is turned off. The gate-source voltage difference of the N-channel enhancement-mode MOSFET X2 is greater than 0 and it is turned on. The gate-source voltage difference of the N-channel junction MOSFET J1 at the output terminal is 0V, so the N-channel junction MOSFET J1 is turned on. The gate voltage difference of the N-channel junction MOSFET J2 is less than Vp (Vp is the gate voltage) and it is not turned on. At this time, the DAC port and the OUT port are connected.

[0038] When the CON port is 0V, the N-channel junction field-effect transistor X1 at the control terminal is turned on, while the N-channel junction field-effect transistor X2 is not turned on. At the output terminal, the N-channel junction field-effect transistor J1 is turned off, while the N-channel junction field-effect transistor J2 is turned on. At this time, the CANH port and the OUT port are connected. In short, the voltage at the CON port can be used to control whether the OUT0 / 1 output is DAC0 / 1 or CANH / L.

[0039] Example 2 differs from Example 1 in that:

[0040] Using positive voltage control, you only need to replace the two N-channel enhancement-mode MOSFETs in the electronic switching circuit with two P-channel enhancement-mode MOSFETs, and the two N-channel junction MOSFETs with two P-channel junction MOSFETs.

[0041] If -VCC is a positive voltage, such as 12V; when the CON port is 12V, the gate-source voltage difference of X1 at the control terminal is equal to 0 and it does not conduct, while the gate-source voltage difference of X2 is greater than 0 and it conducts. At the output terminal, the gate-source voltage difference of the upper transistor J1 is 0V, so the upper transistor J1 conducts, and the gate-source voltage difference of the lower transistor J2 is greater than Vp and it does not conduct. At this time, the DAC port and the OUT port are connected.

[0042] When the CON port is 0V, X1 on the control terminal is turned on and X2 is turned off; the upper transistor J1 on the output terminal is turned off and the lower transistor J2 is turned on. At this time, the CAN port and the OUT port are connected.

[0043] Comparison between Example 1 and Example 2:

[0044] The control voltage is different. If an N-channel junction MOSFET is used, a negative voltage is required, so an additional charge pump chip is needed to generate the negative voltage.

[0045] If a P-channel junction MOSFET is used, a negative voltage is not required, but the control voltage must be greater than the input voltage. Since the maximum input voltage of this product is 10.8V, and it also has a 12V option, option two can also be used.

[0046] The control logic is the same. Regardless of whether a positive or negative voltage is used, the control effect is the same when the voltage at the CON port is 0V.

[0047] In terms of cost, Example 2 has one less charge pump negative voltage chip than Example 1, so Example 2 is cheaper, but the P-channel junction field-effect transistor used is not commonly used.

[0048] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A circuit for switching between CAN and DAC based on a MOSFET switch, comprising an MCU, an electronic switch, a heating module, a temperature sampling module, a calibration data storage module, a CAN module, and a DAC module, characterized in that: The electronic switch is connected to the DAC module through DAC0 port and DAC1 port; The electronic switch is connected to the CAN module via the CANH port and the CANL port. The CAN module and DAC module are connected to the MCU; The MCU is connected to the heating module, the temperature sampling module, and the calibration data storage module, respectively.

2. The circuit for switching between CAN and DAC based on a MOSFET switch according to claim 1, characterized in that: The electronic switch includes two N-channel enhancement-mode field-effect transistors (X1, X2), which together form a selection control circuit.

3. The circuit for switching between CAN and DAC based on a MOSFET switch according to claim 2, characterized in that: The electronic switch includes two N-channel junction field-effect transistors (J1, J2), which together form a selection output circuit.

4. The circuit for switching between CAN and DAC based on a MOSFET switch according to claim 3, characterized in that: The N-channel junction field-effect transistor J1 is connected to the DAC0 port, and the N-channel junction field-effect transistor J2 is connected to the CANH port.

5. The circuit for switching between CAN and DAC based on a MOSFET switch according to claim 4, characterized in that: The electronic switch includes N-channel junction field-effect transistors (J3 and J4), with N-channel junction field-effect transistor J3 connected to the DAC1 port and N-channel junction field-effect transistor J4 connected to the CANL port.

6. The circuit for switching between CAN and DAC based on a MOSFET switch according to claim 1, characterized in that: The MCU is connected to a DC-DC 5V module, and the DAC module is connected to a DC-DC 12V module.

7. The circuit for switching between CAN and DAC based on a MOSFET switch according to claim 6, characterized in that: The DC-DC 5V module and DC-DC 12V module are connected to the reverse connection protection module.

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