Range-switchable current acquisition circuit
By integrating a range-switchable current acquisition circuit into the camera power supply circuit, the problem of large and unstable current range of the camera is solved, achieving high-precision current monitoring and anti-interference capability, and ensuring circuit safety.
Patent Information
- Application Number
- CN202512015061.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-29
- Publication Date
- 2026-02-24
AI Technical Summary
Existing cameras have a wide and unstable current range, making it difficult to simultaneously guarantee measurement range and accuracy, especially when using nighttime lighting, which requires high-precision current monitoring.
Design a range-switching current acquisition circuit, integrated into the camera power supply circuit, including front-end filtering, sensor driving, light driving and current sampling circuits. It uses voltage follower and differential amplifier circuits for self-sampling, and realizes automatic switching of amplification resistor through range switching circuit to adapt to different range requirements.
Stable monitoring of camera current was achieved, improving measurement accuracy and anti-interference capability, ensuring that circuit design complies with safety specifications, and preventing equipment damage and electromagnetic interference.
Smart Images
Figure CN121559149A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a range-switching current acquisition circuit. Background Technology
[0002] To enhance driving safety, many vehicles nowadays are equipped with cockpit monitoring cameras. These cameras not only monitor the driver's work status in real time but also provide emergency warning lights. However, due to the variability of the driving environment and the unpredictable lighting conditions inside the cockpit, the camera's lighting requirements vary depending on the environment, especially at night when supplemental lighting is needed. For stable camera operation, real-time monitoring of the camera's current parameters is crucial. Load current monitoring allows for real-time monitoring of the power consumption of the electronic control system, ensuring that the circuit design complies with safety regulations. Detecting abnormal current fluctuations can quickly identify potential faults such as short circuits and overloads, preventing equipment damage or electromagnetic interference affecting other systems due to unstable current.
[0003] Traditional camera lighting equipment uses 940nm infrared LEDs, which have high power, high luminous efficiency, and strong anti-interference capabilities, but their operating current is generally above 1A. When the LEDs are not in use, the camera module has a very low operating current, typically around 50mA. Therefore, the DMC camera module has a wide operating current range (50mA to over 1A), and ensuring both the measurement range and accuracy of the current has become a challenge for the industry. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide a range-switching current acquisition circuit, which realizes automatic acquisition through a self-sampling mode of the circuit, and at the same time uses a range-switching circuit to automatically switch the resistor of the amplifier circuit for different ranges, thereby meeting the sampling requirements of different ranges.
[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: A range-switchable current acquisition circuit is integrated into a camera power supply circuit, which includes a front-end filter circuit, a sensor driving circuit, and a light driving circuit. The sensor driving circuit and the light driving circuit are connected in parallel to the front-end filter circuit. A current sampling circuit is provided between the sensor driving circuit, the light driving circuit, and the front-end filter circuit for current sampling. The current sampling circuit includes a sampling circuit, a voltage follower circuit, a differential amplifier circuit, and a range switching circuit. The sampling circuit contains a sampling resistor connected in series in the camera power supply circuit. The voltage follower circuit is connected in parallel with the sampling resistor, and two operational amplifiers are connected externally to the differential amplifier circuit. The differential amplifier circuit has an amplifier connected to the output terminals of the operational amplifiers in the voltage follower circuit. The range switching circuit is connected in parallel to one side of the current sampling amplifier circuit and is used to switch the sampling range.
[0006] Furthermore, the voltage follower circuit includes a first operational amplifier and a second operational amplifier, wherein the first operational amplifier is connected to the positive terminal of the sampling resistor, and the second operational amplifier is connected to the negative terminal of the sampling resistor.
[0007] Furthermore, the positive terminal of the amplifier in the differential amplifier circuit is connected in series with a first resistor and then connected to the first operational amplifier of the voltage follower circuit; the negative terminal of the amplifier in the differential amplifier circuit is connected in series with a second resistor and then connected to the second operational amplifier of the voltage follower circuit; simultaneously, the range switching circuit is connected in parallel to the negative terminal of the amplifier.
[0008] Furthermore, the range switching circuit includes multiple switching resistors and an analog switch; the multiple switching resistors are connected in parallel and connected to the analog switch.
[0009] Furthermore, the resistance value of each of the aforementioned switching resistors is different, and they are proportionally amplified by a factor of ten.
[0010] Furthermore, the analog switch is connected to a control chip, which controls the opening and closing of the analog switch.
[0011] Furthermore, the control chip is connected to the vehicle bus.
[0012] Furthermore, the positive terminal of the amplifier is also connected to a third resistor, which is connected to ground.
[0013] Furthermore, the switching resistors are set to no fewer than four, with resistance values of 1KΩ, 10KΩ, 100KΩ and 1MΩ respectively.
[0014] Furthermore, the differential amplifier circuit is connected to an external digital converter to convert the current signal into a digital signal, which is then connected to the vehicle bus to achieve automatic current sampling.
[0015] Compared with existing technologies, this invention provides a range-switchable current acquisition circuit, built into an in-vehicle camera, achieving current "self-sampling" and actively transmitting sampling results in real time via the vehicle bus. The control chip's software reads the sampled voltage in real time and compares it with the digital converter. By changing the operational amplifier configuration resistor, the voltage amplification factor can be automatically switched to an appropriate range. A voltage follower circuit isolates the measured current loop, ensuring no impact on the measured current. The sampling circuit is placed after the in-vehicle camera's filtering circuit to filter out noise interference, ensuring test stability. Differential operational amplifiers are used for amplification, filtering out common-mode interference and improving measurement accuracy. Attached Figure Description
[0016] Figure 1 This is a sampling flowchart of the present invention.
[0017] Figure 2 This is a circuit diagram of the camera of the present invention.
[0018] Figure 3 This is a circuit diagram of the current sampling circuit of the present invention.
[0019] Figure 4 This is a schematic diagram of the vehicle bus of the present invention.
[0020] The components include: 1. Front-end filter circuit, 2. Sensor drive circuit, 3. Light drive circuit, 4. Current sampling circuit, 5. Sampling circuit, 6. Voltage follower circuit, 7. Differential amplifier circuit, 8. Range switching circuit, 9. Amplifier, 10. First operational amplifier, 11. Second operational amplifier, 12. First resistor, 13. Second resistor, 14. Third resistor, 15. Switching resistor, 16. Analog switch, 17. Control chip, and 18. Digital converter. Detailed Implementation
[0021] In one embodiment, such as Figure 1 and 4As shown, the current sampling process is as follows: a sampling resistor is connected in series in the camera power supply circuit. When the current passes through the sampling resistor, it flows through the voltage follower circuit 6 composed of the first transistor 10 and the second transistor 11 to the differential amplifier circuit 7. The differential amplifier circuit 7 amplifies the current and inputs it to the digital converter 18 (ADC converter). The ADC converter 18 converts the current into a digital signal and sends it to the vehicle bus for the vehicle bus to retrieve at any time. The control chip 17 (MCU) connected to the vehicle bus reads the sampling voltage and the real-time voltage on the switching range circuit from the ADC converter 18. The two are compared, and then the analog switch 16 on the switching range circuit is controlled to select the appropriate switching resistor 15, thereby adjusting the amplification factor of the differential amplifier circuit 7 and ensuring the adaptability of the sampling range.
[0022] like Figure 2 As shown, a range-switching current acquisition circuit is integrated into a camera power supply circuit. The camera power supply circuit includes a front-end filter circuit 1, a sensor drive circuit 2, and a light drive circuit 3. The sensor drive circuit 2 and the light drive circuit 3 are connected in parallel to the front-end filter circuit 1. A current sampling circuit 5 is provided between the sensor drive circuit 2 and the light drive circuit 3 and the front-end filter circuit 1 for current sampling. like Figure 3 As shown, the current sampling circuit 4 includes a sampling circuit 5, a voltage follower circuit 6, a differential amplifier circuit 7, and a range switching circuit 8. The sampling circuit 5 contains a sampling resistor connected in series in the camera power supply circuit. The voltage follower circuit 6 is connected in parallel with the sampling resistor and is connected to the differential amplifier circuit 7 by two operational amplifiers. The differential amplifier circuit 7 has an amplifier 9, which is connected to the positive and negative stages of the operational amplifiers of the voltage follower circuit 6. The range switching circuit 8 is connected in parallel on one side of the differential amplifier circuit and is used to switch the sampling range.
[0023] In one embodiment, the voltage follower circuit 6 includes a first operational amplifier 10 and a second operational amplifier 11. The first operational amplifier 10 is connected to the positive terminal of the sampling resistor, and the second operational amplifier 11 is connected to the negative terminal of the sampling resistor. The positive terminal of amplifier 9 in the differential amplifier circuit 7 is connected in series with a first resistor 12 and then connected to the first operational amplifier of the voltage follower circuit 6. The negative terminal of amplifier 9 in the differential amplifier circuit 7 is connected in series with a second resistor 13 and then connected to the second operational amplifier of the voltage follower circuit 6. Simultaneously, the negative terminal of amplifier 9 is connected in parallel to the range switching circuit 8. The range switching circuit 8 includes multiple switching resistors 15 and an analog switch 16. The multiple switching resistors 15 are connected in parallel and then connected to the analog switch 16. Each switching resistor 15 has a different resistance value, amplified proportionally by a factor of ten. The analog switch 16 is connected to a control chip 17, which controls the opening and closing of the analog switch 16. The control chip 17 is connected to the vehicle bus. The positive terminal of the amplifier 9 is also connected to a third resistor 14, which is then connected to ground. At least four switching resistors 15 are provided, with resistance values of 1KΩ, 10KΩ, 100KΩ, and 1MΩ respectively. The differential amplifier circuit 7 is connected to a digital converter 18 to convert the current signal into a digital signal, which is then connected to the vehicle bus to achieve automatic current sampling.
[0024] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.
Claims
1. A range-switchable current acquisition circuit, integrated into a camera power supply circuit, wherein the camera power supply circuit includes a front-end filter circuit, a sensor driving circuit, and a light driving circuit; wherein the sensor driving circuit and the light driving circuit are connected in parallel to the front-end filter circuit, and a current sampling circuit is provided between the sensor driving circuit, the light driving circuit, and the front-end filter circuit for current sampling; characterized in that, The current sampling circuit includes a sampling circuit, a voltage follower circuit, a differential amplifier circuit, and a range switching circuit. The sampling circuit contains a sampling resistor connected in series in the camera power supply circuit. The voltage follower circuit is connected in parallel with the sampling resistor, and two operational amplifiers are connected externally to the differential amplifier circuit. The differential amplifier circuit has an amplifier connected to the output terminals of the operational amplifiers in the voltage follower circuit. The range switching circuit is connected in parallel to one side of the current sampling amplifier circuit and is used to switch the sampling range.
2. The range-switchable current acquisition circuit according to claim 1, characterized in that, The voltage follower circuit includes a first operational amplifier and a second operational amplifier. The first operational amplifier is connected to the positive terminal of the sampling resistor, and the second operational amplifier is connected to the negative terminal of the sampling resistor.
3. The range-switchable current acquisition circuit according to claim 1, characterized in that, The positive terminal of the amplifier in the differential amplifier circuit is connected in series with a first resistor and then connected to the first operational amplifier of the voltage follower circuit; the negative terminal of the amplifier in the differential amplifier circuit is connected in series with a second resistor and then connected to the second operational amplifier of the voltage follower circuit; at the same time, the range switching circuit is connected in parallel to the negative terminal of the amplifier.
4. The range-switchable current acquisition circuit according to claim 1, characterized in that, The range switching circuit includes multiple switching resistors and an analog switch; the multiple switching resistors are connected in parallel and connected to the analog switch.
5. A range-switchable current acquisition circuit according to claim 4, characterized in that, Each of the aforementioned switching resistors has a different resistance value, and they are scaled up proportionally by a factor of ten.
6. The range-switchable current acquisition circuit according to claim 1, characterized in that, The analog switch is connected to a control chip, which controls the opening and closing of the analog switch.
7. A range-switchable current acquisition circuit according to claim 6, characterized in that, The control chip is connected to the vehicle bus.
8. A range-switchable current acquisition circuit according to claim 3, characterized in that, The positive terminal of the amplifier is also connected to a third resistor, which is connected to ground.
9. A range-switchable current acquisition circuit according to claim 4, characterized in that, The switching resistors are set to no fewer than four, with resistance values of 1KΩ, 10KΩ, 100KΩ and 1MΩ respectively.
10. A range-switchable current acquisition circuit according to claim 1, characterized in that, The differential amplifier circuit is connected to an external digital converter to convert the current signal into a digital signal, which is then connected to the vehicle bus to achieve automatic current sampling.