A rearview mirror anti-dazzle drive system
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- ZHEJIANG LINGAI FUTURE TECHNOLOGY CO LTD
- Filing Date
- 2025-09-04
- Publication Date
- 2026-07-14
Smart Images
Figure CN224503338U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of power electronics technology, specifically to a rearview mirror anti-glare drive system. Background Technology
[0002] Rearview mirrors are tools to provide drivers with a view of what's behind them. However, in dark environments such as basements or at night, the glare of headlights from vehicles behind can be blinding, making it difficult for drivers to accurately judge the situation and affecting driving safety. Currently, more and more smart cars are equipped with rearview mirrors that automatically adjust to prevent glare, providing safety for drivers in dark environments.
[0003] Anti-glare rearview mirrors use lenses with an electrochromic material layer. By adjusting the voltage output to the lens, different reflectivities are achieved. Most commercially available anti-glare rearview mirror lenses operate at a driving voltage below 1.2V, while drawing as much as 200-300 milliamps. Due to the low-voltage adjustable and high-current load characteristics, it is difficult to find suitable step-down driver chips on the market to provide a stable output voltage for anti-glare rearview mirrors. Utility Model Content
[0004] A rearview mirror anti-glare drive system is provided, which can provide a stable output voltage for the rearview mirror anti-glare function.
[0005] In a first aspect, embodiments of this application provide a rearview mirror anti-glare drive system, comprising:
[0006] A filter voltage divider circuit is used to receive the control signal output by the main control unit and output an adjustable voltage according to the control signal.
[0007] The voltage follower circuit includes a first operational amplifier and a Darlington transistor. The non-inverting input of the first operational amplifier is used to connect the adjustable voltage, and the output of the first operational amplifier is used to output a drive signal. The base of the Darlington transistor is used to receive the drive signal, and the emitter of the Darlington transistor is used to connect an external load and the negative inverting input of the first operational amplifier to output a regulated signal.
[0008] In one embodiment of this application, a discharge control circuit is further included, which is used to receive a discharge control signal and discharge the external load according to the discharge control signal.
[0009] In one embodiment of this application, the discharge control circuit includes a discharge chip and a discharge switch. The discharge chip is connected between the external load and ground. The control terminal of the discharge chip is used to receive the discharge control signal. The discharge chip can controllably switch the grounding loop of the external load on and off based on the discharge control signal.
[0010] The discharge switch is connected between the non-inverting input terminal of the first operational amplifier and ground. The control terminal of the discharge switch is used to receive the discharge control signal. Based on the discharge control signal, the discharge switch can controllably switch the grounding loop of the non-inverting input terminal of the first operational amplifier on and off.
[0011] In one embodiment of this application, the discharge chip has a fault diagnosis unit for identifying and reporting fault information.
[0012] In one embodiment of this application, the filter voltage divider circuit includes a filter section and a voltage divider section. The filter section is used to receive the control signal and output a filtered signal according to the control signal. The voltage divider section is used to receive the filtered signal and output the adjustable voltage according to the filtered signal.
[0013] In one embodiment of this application, the filtering unit is a second-order active filter.
[0014] In one embodiment of this application, the voltage of the filtered signal is 0V to 5V, and the voltage of the adjustable voltage is 0V to 1.4V.
[0015] In one embodiment of this application, a tracking low-dropout regulator is also included for connecting to the collector of the Darlington transistor and outputting a current-limiting power supply.
[0016] In one embodiment of this application, a data acquisition unit is further included. The input terminal of the data acquisition unit is used to connect to the emitter of the Darlington tube to receive the regulated signal. The output terminal of the data acquisition unit is used to connect to the main control unit to output a data acquisition signal generated based on the regulated signal.
[0017] In one embodiment of this application, the main control unit is integrated into the body controller.
[0018] This application utilizes a filter-divider circuit to output a stable adjustable voltage. The first operational amplifier operates in voltage follower mode, with the adjustable voltage connected to its non-inverting input. The output of the operational amplifier is connected to the base of a Darlington transistor, controlling the Darlington transistor to achieve a step-down output. The Darlington transistor possesses extremely high current gain, high input impedance, and low output impedance, making it suitable for driving high-current loads. The emitter output of the Darlington transistor supplies power to the anti-glare rearview mirror and simultaneously transmits power to the negative input of the operational amplifier, forming a negative feedback loop to achieve a voltage-following regulated output. Attached Figure Description
[0019] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0020] Figure 1 This is an architecture diagram of a rearview mirror anti-glare drive system provided in some embodiments of this application;
[0021] Figure 2 This is a circuit diagram of the filter section provided in some embodiments of this application;
[0022] Figure 3 This is a circuit connection diagram of the voltage follower circuit and the discharge control circuit provided in some embodiments of this application.
[0023] In the attached image:
[0024] 1. Main control unit; 2. Filtering and voltage divider circuit; 21. Filtering section; 22. Voltage divider section; 3. Voltage follower circuit; 4. Discharge control circuit; 41. Discharge chip; 42. Discharge switch section; 5. Data acquisition unit;
[0025] R1, first resistor; R2, second resistor; R3, third resistor; R4, fourth resistor; R5, fifth resistor; R6, sixth resistor; R7, seventh resistor; R8, eighth resistor; C1, first capacitor; C2, second capacitor; C3, third capacitor; C4, fourth capacitor; C5, fifth capacitor; C6, sixth capacitor; C7, seventh capacitor; C8, eighth capacitor; Q1, Darlington transistor; Q2, transistor; U1, first operational amplifier; U2, second operational amplifier; D1, diode; PWM, control signal; VDC, filter signal; Vin, adjustable voltage; Dis, bleeder control signal; OUT, regulated signal. Detailed Implementation
[0026] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0027] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.
[0028] like Figure 1 , Figure 2 , Figure 3 As shown, an embodiment of this application provides a rearview mirror anti-glare drive system, which adopts a discrete drive control architecture, including:
[0029] The filter voltage divider circuit 2 is used to receive the control signal PWM output by the main control unit 1 and output an adjustable voltage Vin according to the control signal PWM.
[0030] The voltage follower circuit 3 includes a first operational amplifier U1 and a Darlington transistor Q1. The non-inverting input of the first operational amplifier U1 is used to connect an adjustable voltage Vin, and the output of the first operational amplifier U1 is used to output a drive signal. The base of the Darlington transistor Q1 is used to receive the drive signal, and the emitter of the Darlington transistor Q1 is used to connect an external load and the negative inverting input of the first operational amplifier U1, and outputs a regulated voltage signal OUT.
[0031] Specifically, the filter voltage divider circuit 2 of this application includes a filter section 21 and a voltage divider section 22. The filter section 21 is used to receive the control signal PWM and output the filter signal VDC according to the control signal PWM. The voltage divider section 22 is used to receive the filter signal VDC and output the adjustable voltage Vin according to the filter signal VDC.
[0032] In a specific embodiment, the filtering unit 21 of this application is a second-order active filter, including:
[0033] The first resistor R1, the first end of the first resistor R1 is used to receive the control signal PWM, the control signal of this application is the duty cycle signal;
[0034] The second resistor R2 is connected to the second end of the first resistor R1.
[0035] The first capacitor C1 has its first terminal connected to the second terminal of the second resistor R2, and the second terminal of the first capacitor C1 is grounded. In this application, the second resistor R2 and the first capacitor C1 constitute a first-order filter.
[0036] The second operational amplifier U2 has its non-inverting input connected to the first terminal of the second resistor R2, and its negative input connected to the first terminal of the second resistor R2 via the second capacitor C2. The negative feedback of the second operational amplifier U2 and the first resistor R1 form a second-order filter, which can effectively filter out the high-frequency ripple of the control signal PWM, making the voltage at the non-inverting input of the second operational amplifier U2 closer to pure DC. The second operational amplifier U2 operates in voltage follower mode, and its output voltage is approximately equal to the voltage at the non-inverting terminal. Since the duty cycle of the control signal PWM can be adjusted from 0% to 100%, in this embodiment, the high level of the control signal PWM output by the main control unit 1 is 5V and the low level is 0V. The voltage of the filtered signal VDC is proportional to the duty cycle. When the duty cycle is 0%, the filtered signal VDC is 0V, and when the duty cycle is 100%, the filtered signal VDC is 5V, realizing a continuously adjustable DC voltage output from 0V to 5V.
[0037] Since most rearview mirror anti-glare lenses on the market have a driving voltage below 1.2V, directly inputting a 5V filtered signal VDC into the lens would cause it to burn out due to overvoltage. Therefore, the voltage needs to be reduced to a safe range by the voltage divider 22. In this application, the filtered signal VDC is further divided by the voltage divider 22 to obtain an adjustable voltage Vin from 0V to 1.4V, ensuring that the output voltage is not too high and causes the anti-glare lens to burn out.
[0038] In one specific embodiment, please refer further to Figure 3 As shown, the voltage follower circuit 3 of this application includes:
[0039] The first operational amplifier U1 has an inverting input terminal for connecting an adjustable voltage Vin and an output terminal for outputting a drive signal.
[0040] The third resistor R3 and the third capacitor C3 are connected, with the first terminal of the third capacitor C3 connected to the non-inverting input terminal of the first operational amplifier U1.
[0041] The third resistor R3 has its first end connected to the second end of the third capacitor C3, and the second end of the third resistor R3 is connected to the negative input terminal of the first operational amplifier U1. The third capacitor C3 and the third capacitor C3 in this application are used for input filtering and input current, and to attenuate the high-frequency noise of the adjustable voltage Vin.
[0042] The fifth resistor R5 has its first end connected to the output of the first operational amplifier U1.
[0043] The Darlington transistor has its base connected to the second terminal of the fifth resistor R5 to receive the drive signal. The emitter of the Darlington transistor is connected to the output terminal of the rearview mirror anti-glare drive system of this application to output a regulated signal OUT to the load. The emitter of the Darlington transistor is also connected back to the negative input terminal of the first operational amplifier U1 through the fourth resistor R4.
[0044] Specifically, the voltage follower circuit 3 of this application is constructed using a combination of a first operational amplifier U1 and a Darlington transistor Q1. An adjustable voltage Vin from 0V to 1.4V is input to the non-inverting input of the first operational amplifier U1, while the output of the first operational amplifier U1 is connected to the base of the Darlington transistor via a fifth resistor R5, controlling the Darlington transistor Q1 to achieve a step-down output. The emitter output of the Darlington transistor Q1 supplies the anti-glare rearview mirror load and simultaneously transmits the voltage to the negative inverting input of the first operational amplifier U1, forming a negative feedback loop to achieve a regulated voltage follower output, which is more reliable and stable than the step-down output of an open-loop transistor. The Darlington transistor Q1 has extremely high current gain, high input impedance, and low output impedance, making it suitable for driving high-current loads.
[0045] The collector-emitter voltage of the Darlington transistor Q1 in this application must be sufficiently high, greater than 40V. Since this device is an external output, it must be ensured that the device will not be damaged in the event of an external short-circuit fault. Furthermore, the continuous current of the Darlington transistor Q1 must be greater than 500mA, and the peak current must be greater than 1A. To ensure sufficient current gain and guarantee output current capability, the DC current amplification factor of the Darlington transistor Q1 must be greater than 1000 times. Additionally, based on the maximum junction temperature, thermal resistance, and voltage drop, calculations show that the driving capability is sufficient to meet the load requirements at 85℃, satisfying automotive-grade requirements and preventing chip overheating and damage.
[0046] The first operational amplifier U1 can be a general-purpose dual-channel op-amp, saving cost and space. One channel is used for low-pass filtering, and the other channel is used for voltage follower circuit 3. Since the current application scenario involves excessively large load current, a high-gain power op-amp could be used to directly drive the external load, but such op-amps are very expensive. This application directly uses a common op-amp plus a Darlington transistor Q1 driving circuit, significantly reducing the overall cost.
[0047] To further suppress high-frequency oscillations, compensate for low frequencies, and ensure sufficient phase margin, this application also includes:
[0048] The fourth capacitor C4 has its first end connected to the output terminal of the first operational amplifier U1, and its second end connected to the negative input terminal of the first operational amplifier U1.
[0049] The fifth capacitor C5 is connected in parallel across the fourth resistor R4;
[0050] The seventh capacitor C7 has its first terminal connected to the second terminal of the fifth resistor R5, and its second terminal grounded.
[0051] The selection of resistors and capacitors used in this application requires specific calculation of the RC filtering frequency to determine appropriate resistance and capacitance values. Resistors are typically chosen between 10kΩ and 100kΩ, which avoids excessive leakage current and increased power consumption, and is suitable for high-frequency filtering. Capacitor selection must be based on the actual circuit. For example, in a low-pass filter circuit, to rectify AC signals into DC signals, a lower filtering frequency is needed, requiring larger capacitance values, typically nanofarad level capacitors. However, for capacitors such as C5 (fifth capacitor) and C7 (seventh capacitor), to filter high-frequency signals, picofarad level capacitors are required.
[0052] In an optional embodiment, a tracking low-dropout regulator is also included for connecting to the collector of Darlington transistor Q1 to output a current-limited power supply.
[0053] Specifically, the collector power supply VCC of the Darlington transistor Q1 in this application is output from a TrackLDO. In the event of a short circuit to ground fault in the wiring harness output to the external load, the TrackLDO can provide current limiting protection to ensure circuit safety. At the same time, the two-stage voltage drop can distribute the power loss caused by the large voltage drop, preventing the Darlington transistor Q1 from being directly reduced from the battery voltage to 1.2V or below, which would make it difficult for the chip to withstand the temperature rise caused by the large voltage drop.
[0054] In an optional embodiment, the system further includes a data acquisition unit 5. The input terminal of the data acquisition unit 5 is connected to the emitter of the Darlington transistor Q1 through an eighth resistor R8 to receive the regulated voltage signal OUT. The output terminal of the data acquisition unit 5 is used to connect to the main control unit 1 to output a data acquisition signal generated based on the regulated voltage signal OUT.
[0055] This application also includes an eighth capacitor C8 for filtering the received signal of the acquisition unit 5. The first end of the eighth capacitor C8 is connected to the input end of the acquisition unit 5, and the second end of the eighth capacitor C8 is grounded.
[0056] The main control unit 1 of this application collects the voltage value output from the emitter stage of Darlington transistor Q1 through the sampling unit 5 to ensure stable and reliable output voltage. If there is a slight deviation in voltage, the output voltage value can be dynamically adjusted and calibrated through software. In addition, if a short circuit to ground fault occurs at the output terminal, or a short circuit to power supply fault occurs when the circuit is not enabled, the fault can be reported through the voltage value, and corresponding actions can be taken to ensure circuit safety.
[0057] In an optional embodiment, the rearview mirror anti-glare drive system further includes a discharge control circuit 4 for receiving a discharge control signal Dis and discharging an external load according to the discharge control signal Dis.
[0058] The discharge control circuit 4 includes a discharge chip 41 and a discharge switch 42. The discharge chip 41 is connected between the external load and ground. The control terminal of the discharge chip 41 is used to receive the discharge control signal Dis. Based on the discharge control signal Dis, the discharge chip 41 can controllably switch the grounding loop of the external load on and off.
[0059] The discharge switch 42 is connected between the non-inverting input terminal of the first operational amplifier U1 and ground. The control terminal of the discharge switch 42 is used to receive the discharge control signal Dis. Based on the discharge control signal Dis, the discharge switch 42 can controllably switch the grounding loop of the non-inverting input terminal of the first operational amplifier U1 on and off.
[0060] Specifically, the discharge chip 41 in this application uses a low-side chip. Since the anti-glare lens is equivalent to a farad capacitor, if there is no discharge path after the power supply is stopped, the charge stored inside the large capacitor is difficult to release quickly, which makes it impossible for the reflectivity of the lens to increase quickly, affecting the driver's driving safety.
[0061] More specifically, the selection of the low-side chip in this application must ensure that it meets the instantaneous discharge current carrying capacity, and the internal resistance of the low-side chip must be less than 160mΩ. In addition, the discharge chip 41 has a fault diagnosis unit for identifying and reporting fault information, and can promptly report the fault in the event of a short circuit to a power supply fault.
[0062] This application uses a bleeder chip 41 for rapid discharge. In the event of a short circuit to power failure in the external load harness, the bleeder chip 41 can promptly shut down for protection, preventing chip burnout. A diode D1 is also provided between the bleeder chip 41 and the emitter of the Darlington transistor Q1. Diode D1 prevents current from flowing out of the anti-glare lens through the body diode D1 inside the low-side chip when the power supply is reversed, thus preventing lens burnout.
[0063] In one specific embodiment, the discharge switch 42 uses transistor Q2 to pull down the input voltage of the operational amplifier, preventing the low-side chip from conducting and causing a short circuit to ground when the Darlington transistor Q1 is not yet turned off. The discharge switch 42 includes:
[0064] Transistor Q2, the base of transistor Q2 is used to receive the discharge control signal Dis through the sixth resistor R6, the collector of transistor Q2 is connected to the non-inverting input terminal of the first operational amplifier U1, and the emitter of transistor Q2 is grounded.
[0065] The seventh resistor R7 and the sixth capacitor C6 are connected in parallel between the base and bottom of transistor Q2.
[0066] When the discharge control signal Dis is valid, transistor Q2 is turned on, pulling the non-inverting input of the first operational amplifier U1 down to ground potential, forcing the output of the first operational amplifier U1 to decrease, and the Darlington transistor is turned off. In this application, transistor Q2 first pulls down the input of the first operational amplifier U1, and then cooperates with the discharge chip 41 to turn on, avoiding shoot-through short circuit.
[0067] In one optional embodiment, the main control unit 1 is integrated within the vehicle body controller. Specifically, the rearview mirror anti-glare drive circuit of this application is integrated into the vehicle body controller, and data acquisition, drive control, and fault diagnosis are performed through the main control unit 1 in the vehicle body controller. The vehicle body controller is a vehicle accessory controller that integrates a core processor and can control accessories such as doors, lights, rearview mirrors, and wipers according to user commands.
[0068] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.
[0069] The above provides a detailed description of a rearview mirror anti-glare drive system provided in the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.
Claims
1. A rearview mirror anti-glare drive system, characterized in that, include: A filter voltage divider circuit is used to receive the control signal output by the main control unit and output an adjustable voltage according to the control signal. The voltage follower circuit includes a first operational amplifier and a Darlington transistor. The non-inverting input of the first operational amplifier is used to connect the adjustable voltage, and the output of the first operational amplifier is used to output a drive signal. The base of the Darlington transistor is used to receive the drive signal, and the emitter of the Darlington transistor is used to connect an external load and the negative inverting input of the first operational amplifier to output a regulated signal.
2. The rearview mirror anti-glare drive system according to claim 1, characterized in that, It also includes a discharge control circuit for receiving a discharge control signal and discharging the external load according to the discharge control signal.
3. The rearview mirror anti-glare drive system according to claim 2, characterized in that, The discharge control circuit includes a discharge chip and a discharge switch. The discharge chip is connected between the external load and ground. The control terminal of the discharge chip is used to receive the discharge control signal. The discharge chip can controllably switch the grounding loop of the external load on and off based on the discharge control signal. The discharge switch is connected between the non-inverting input terminal of the first operational amplifier and ground. The control terminal of the discharge switch is used to receive the discharge control signal. Based on the discharge control signal, the discharge switch can controllably switch the grounding loop of the non-inverting input terminal of the first operational amplifier on and off.
4. The rearview mirror anti-glare drive system according to claim 3, characterized in that, The discharge chip has a fault diagnosis unit for identifying and reporting fault information.
5. The rearview mirror anti-glare drive system according to claim 1, characterized in that, The filter voltage divider circuit includes a filter section and a voltage divider section. The filter section is used to receive the control signal and output a filtered signal according to the control signal. The voltage divider section is used to receive the filtered signal and output the adjustable voltage according to the filtered signal.
6. The rearview mirror anti-glare drive system according to claim 5, characterized in that, The filtering section is a second-order active filter.
7. The rearview mirror anti-glare drive system according to claim 5, characterized in that, The voltage of the filtered signal is 0V to 5V, and the voltage of the adjustable voltage is 0V to 1.4V.
8. The rearview mirror anti-glare drive system according to claim 1, characterized in that, It also includes a tracking low-dropout regulator for connecting to the collector of the Darlington transistor and outputting a current-limiting power supply.
9. The rearview mirror anti-glare drive system according to claim 1, characterized in that, It also includes a data acquisition unit, the input of which is connected to the emitter of the Darlington tube to receive the regulated signal; the output of which is connected to the main control unit to output a data acquisition signal generated based on the regulated signal.
10. The rearview mirror anti-glare drive system according to claim 1, characterized in that, The main control unit is integrated into the body controller.