Driving circuit and dimming rearview mirror comprising driving circuit

Abstract

A driving circuit for a dimming rearview mirror, the driving circuit comprising: a micro-controller unit circuit, a front-facing light sensor circuit, a rear-facing light sensor circuit and an H-bridge control circuit, wherein the front-facing light sensor circuit is used for sensing the intensity of light in front of a dimming rearview mirror, converting a sensed optical signal into a first electrical signal and transmitting same to the micro-controller unit circuit; the rear-facing light sensor circuit is used for sensing the intensity of light behind the dimming rearview mirror, converting a sensed optical signal into a second electrical signal and transmitting same to the micro-controller unit circuit; one end of the H-bridge control circuit is electrically connected to the micro-controller unit circuit, and the other end thereof is electrically connected to a liquid crystal film on the dimming rearview mirror; and the micro-controller unit circuit is configured to drive and control the H-bridge control circuit on the basis of the first electrical signal and the second electrical signal, so as to control a driving voltage switch of the liquid crystal film.

Description

Driving circuit and dimming rearview mirror including the driving circuit

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese Patent Application No. 202420071394.9 filed on January 11, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The embodiments of the present disclosure relate to, but are not limited to, rearview mirror technology, and in particular to a driving circuit and a dimming rearview mirror including the driving circuit. Background Art

[0004] Mid-range and high-end vehicles are typically equipped with rearview mirrors with anti-glare features. When the mirror senses strong light from behind the vehicle, it significantly reduces its reflectivity (for example, to 5%-10% of normal). This prevents glare to the driver's eyes caused by strong reflected light from the mirror, improving driving safety.

[0005] In related technologies, electrochromic (EC) glass is created by adding electrochromic materials to glass panels. Using EC glass as a dimming lens in rearview mirrors can achieve an anti-glare function. Under the influence of alternating high and low, or positive and negative, external electric fields, EC glass can be injected or extracted with electric charge, reversibly switching between a low-transmittance chromatic state and a high-transmittance achromatic state. This is manifested as a reversible change in color and transparency. When a voltage is applied (charge is injected) across the two electrodes, EC glass takes on a deep blue color, absorbing a significant amount of incident light. This significantly reduces the reflectivity of the EC glass to incident light, achieving an anti-glare effect.

[0006] However, EC glass has a relatively slow response speed. When powered on, it typically takes 3 to 6 seconds for the chemical reaction to reduce its reflectivity, and after power is removed, it typically takes 10 to 15 seconds to return to normal. Furthermore, to ensure safe driving at high speeds, rearview mirrors must instantly reduce or restore their reflectivity based on the intensity of incident light, allowing the driver to clearly see what's ahead and behind the vehicle. EC glass's response speed may not meet these requirements.

[0007] SUMMARY OF THE INVENTION

[0008] According to an embodiment of the present disclosure, a drive circuit for a dimming rearview mirror includes a microcontroller unit (MCU), a front light sensor circuit, a rear light sensor circuit, and an H-bridge control circuit. The front light sensor circuit senses the light intensity in front of the dimming rearview mirror to obtain a first light signal, converts the first light signal into a first electrical signal, and transmits it to the MCU circuit. The rear light sensor circuit senses the light intensity behind the dimming rearview mirror to obtain a second light signal, converts the second light signal into a second electrical signal, and transmits it to the MCU circuit. One end of the H-bridge control circuit is electrically connected to the MCU circuit, and the other end is electrically connected to the liquid crystal film on the dimming rearview mirror. The MCU circuit is configured to drive and control the H-bridge control circuit based on the first and second electrical signals to control the driving voltage switching of the liquid crystal film.

[0009] A dimming rearview mirror according to an embodiment of the present disclosure includes a liquid crystal film and the above-mentioned driving circuit, wherein the driving circuit is used to drive and control the liquid crystal film. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG1 is a block diagram of a driving circuit for a dimming rearview mirror according to an embodiment of the present disclosure.

[0011] FIG2 is a circuit diagram of a boost circuit in a driving circuit according to an embodiment of the present disclosure.

[0012] FIG3 is a circuit diagram of a microcontroller unit (MCU) circuit in a driving circuit according to an embodiment of the present disclosure.

[0013] FIG4 is a circuit diagram of a front light sensor circuit in a driving circuit according to an embodiment of the present disclosure.

[0014] FIG5 is a circuit diagram of a post-light sensor circuit in a driving circuit according to an embodiment of the present disclosure.

[0015] FIG6 is a circuit diagram of a voltage regulation delay control circuit in a driving circuit according to an embodiment of the present disclosure.

[0016] FIG7 is a circuit diagram of an H-bridge control circuit in a driving circuit according to an embodiment of the present disclosure. Modes for Carrying Out the Invention

[0017] Some embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. These embodiments are described for illustrative purposes only and are not intended to limit the present disclosure.

[0018] It should be noted that if directional indications (such as up, down, left, right, front, and back) are mentioned in this disclosure, such directional indications are only used to explain the relative positional relationships and movement of various components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications may change accordingly.

[0019] In addition, if the present disclosure involves modifiers such as "first" and "second", the modifiers such as "first" and "second" are used only for descriptive purposes and cannot be understood as indicating or implying the relative importance or order of the technical features they indicate.

[0020] According to an embodiment of the present disclosure, a dimming rearview mirror for a car may include a front glass panel with a liquid crystal film attached thereto, a rear plastic cover, and a drive circuit. The liquid crystal film may be a Crystal Clear Switching (CCS) liquid crystal film. The drive circuit can drive and control the liquid crystal film.

[0021] As shown in FIG1 , a driving circuit for a dimming rearview mirror according to an embodiment of the present disclosure may include a boost circuit, an MCU circuit, a front light sensor circuit, a rear light sensor circuit, a voltage regulation delay control circuit, and an H-bridge control circuit.

[0022] The boost circuit has a power input terminal and is connected to the voltage regulation delay control circuit and the MCU circuit. The front light sensor circuit is used to sense the light intensity in front of the dimming rearview mirror and convert the sensed light signal into a first electrical signal and transmit it to the MCU circuit. The rear light sensor circuit is used to sense the light intensity behind the dimming rearview mirror and convert the sensed light signal into a second electrical signal and transmit it to the MCU circuit. The voltage regulation delay control circuit is connected to the MCU circuit and is used to delay the voltage regulation of the boost circuit to avoid flickering of the liquid crystal film on the dimming rearview mirror. One end of the H-bridge control circuit is electrically connected to the MCU circuit, and the other end is electrically connected to the liquid crystal film on the dimming rearview mirror. The MCU circuit is capable of driving and controlling the H-bridge control circuit.

[0023] In at least one embodiment, both the front light sensor circuit and the rear light sensor circuit may include highly sensitive photodiode sensors. An MCU circuit may perform analog-to-digital (A / D) conversion on a first electrical signal from the front light sensor circuit and a second electrical signal from the rear light sensor circuit to obtain two light intensity values. Based on the difference between the two light intensity values, a first PWM signal PWM1 and a second PWM signal PWM2 with opposite phases are generated through pulse width modulation (PWM) and output to an H-bridge control circuit to drive and control the H-bridge control circuit. For example, the MCU circuit may include an 8-bit microcontroller. The H-bridge control circuit may generate an AC square wave signal based on the first PWM signal PWM1 and the second PWM signal PWM2, and output this AC square wave signal to the liquid crystal film to control the driving voltage switching of the liquid crystal film in real time.

[0024] As shown in Figure 2, the boost circuit may include integrated circuit U2, a wirewound inductor LE8, a Schottky diode D9, an input capacitor C22, output capacitors C16 and C14, and resistors R9, R8, and R30. The boost circuit operates as follows: a +5V power signal is input to pins 5 and 6 of integrated circuit U2. Resistors R9, R8, and R30 divide the voltage to generate a feedback voltage, which is then applied to pin 3 of integrated circuit U2. Energy storage in the inductor and diode D9 generate a boosted voltage (e.g., 12Vdc) at a switching frequency of 500K to 1MHz. Adjusting the feedback resistors can produce different output voltages.

[0025] As shown in Figure 3, the MCU circuit may include a microcontroller U6. Pin 1 of the microcontroller U6 is used to receive the second electrical signal PS_REAR_OUT from the rear light sensor circuit, and pin 20 is used to receive the first electrical signal PS_FRONT_OUT from the front light sensor circuit. Pin 2 of the microcontroller U6 is a PWM high-voltage control terminal, which can change the output voltage through PWM. Pins 5 and 8 of the microcontroller U6 are both power input terminals. Pin 10 of the microcontroller U6 is a ground terminal. Pins 11 and 12 of the microcontroller U6 serve as serial ports for downloading software. Pin 13 of the microcontroller U6 is a control terminal for the boost circuit, which can output a control signal HV_ON to enable / disable the high voltage. Pins 14 and 15 of the microcontroller U6 can output a first PWM signal PWM1 and a second PWM signal PWM2, respectively, with opposite phases, to the H-bridge control circuit, thereby generating an AC square wave signal on the H-bridge control circuit. Pins 16 to 19 of the microcontroller U6 are reserved voltage control terminals.

[0026] As shown in Figure 4 , the front photosensor circuit may include photosensor PS1, resistors R4 and R65, and capacitors C7 and C12, where resistor R4 is a current-limiting resistor. As shown in Figure 5 , the rear photosensor circuit may include photosensor PS2, resistors R37 and R66, and capacitors C2 and C24, where resistor R37 is a current-limiting resistor.

[0027] The front photosensor circuit operates as follows: After a 5V regulated power signal is applied to photosensor PS1 through resistor R65, light incident on photosensor PS1 generates a photocurrent within photosensor PS1, generating a first photovoltage signal at pin 2 of photosensor PS1 as the first electrical signal, PS_FRONT_OUT. Similarly, the rear photosensor circuit operates as follows: After a 5V regulated power signal is applied to photosensor PS2 through resistor R66, light incident on photosensor PS2 generates a photocurrent within photosensor PS2, generating a second photovoltage signal at pin 2 of photosensor PS2 as the second electrical signal, PS_REAR_OUT. Stronger light increases the photocurrent and the resulting voltage.

[0028] The first electrical signal PS_FRONT_OUT and the second electrical signal PS_REAR_OUT generated by photosensors PS1 and PS2, respectively, are input into an MCU circuit for A / D conversion, thereby obtaining front and rear light intensity values. The MCU circuit calculates the difference between the front and rear light intensity values ​​and, based on this difference, drives and controls the H-bridge control circuit to turn on / off the drive voltage switch for the dimming rearview mirror's liquid crystal film. For example, during the day, the difference between the front and rear light intensity values ​​is typically small. Therefore, the MCU circuit drives and controls the H-bridge control circuit to turn off the drive voltage switch for the liquid crystal film, maintaining the dimming rearview mirror in its normal state. At night, when strong light from behind the vehicle strikes the rearview mirror, the difference between the front and rear light intensity values ​​can be larger (e.g., greater than a preset threshold). Therefore, the MCU circuit drives and controls the H-bridge control circuit to turn on the drive voltage switch for the liquid crystal film. In this way, the reflectivity of the liquid crystal film to the incident light will be reduced instantly, causing the dimming rearview mirror to switch to an anti-glare state.

[0029] As shown in Figure 6, the voltage regulation delay control circuit may include a voltage regulation integrated circuit U4 and a feedback circuit formed by resistors R43, R42, and R41. Pins 1 and 2 of the voltage regulation integrated circuit U4 are voltage input terminals. Pins 3 and 4 of the voltage regulation integrated circuit U4 are voltage output terminals. Pin 6 of the voltage regulation integrated circuit U4 is a voltage feedback terminal.

[0030] When voltage is applied to the liquid crystal, the liquid crystal molecules rotate. When the applied voltage is very high, the rotation angles of the liquid crystal molecules will differ, resulting in visual stroboscopic and dizziness. In view of this, the voltage regulation delay control circuit can be set to generate a fixed voltage through a feedback circuit formed by resistors R43, R42 and R41, and the fixed voltage is applied to the voltage feedback terminal of the voltage regulation integrated circuit U4 through a node electrically connected to the PWM high-voltage control terminal of the MCU circuit, so that the output of different voltages can be delayed. For example, the output voltage can be gradually increased from a low voltage, or gradually decreased from a high voltage, so that the liquid crystal film can be ideally turned on / off to avoid stroboscopic and dazzling.

[0031] As shown in Figure 7, the H-bridge control circuit may include a motor driver integrated circuit U3. The motor driver integrated circuit U3 may include an H-bridge circuit composed of four metal-oxide-semiconductor field effect transistors (MOSFETs). Pins 2 and 3 of the motor driver integrated circuit U3 are both PWM control terminals, which can respectively receive a first PWM signal PWM1 and a second PWM signal PWM2 with opposite phases from the MCU circuit. Pin 8 of the motor driver integrated circuit U3 is used to receive a high voltage signal HV_LCF. Pins 6 and 7 of the motor driver integrated circuit U3 serve as the load interface of the H-bridge, which is used to output an AC square wave signal. The first PWM signal PWM1 and the second PWM signal PWM2 can be used to control the gates of each MOSFET in the H-bridge circuit, respectively, so that the two paths of the H-bridge are alternately turned on, thereby generating an AC square wave signal for controlling the liquid crystal film.

[0032] The driving circuit according to the embodiment of the present disclosure can drive a dimming rearview mirror including a liquid crystal film in real time, enabling the dimming rearview mirror to switch from a normal state to an anti-glare state within 0.1 to 1 second, and to return from the anti-glare state to a normal state within 0.1 to 2 seconds. This can enhance driver safety.

[0033] Some embodiments of the present disclosure have been described in detail above. Based on the teachings of this disclosure, it will be readily apparent to those skilled in the art that various modifications or equivalent substitutions may be made to these embodiments. Such modifications or equivalent substitutions should be within the scope of this disclosure.

Claims

1. A driving circuit for a dimming rearview mirror, comprising: A microcontroller unit (MCU) circuit; A front light sensor circuit, which is used to sense the light intensity in front of the dimming rearview mirror to obtain a first light signal, and convert the first light signal into a first electrical signal and transmit it to the MCU circuit; A rear light sensor circuit, which is used to sense the light intensity behind the dimming rearview mirror to obtain a second light signal, and convert the second light signal into a second electrical signal and transmit it to the MCU circuit; And An H-bridge control circuit, which has a first end electrically connected to the MCU circuit and a second end electrically connected to a liquid crystal film on the dimming rearview mirror, Wherein, the MCU circuit is configured to drive and control the H-bridge control circuit based on the first electrical signal and the second electrical signal to control the driving voltage switch of the liquid crystal film.

2. The driving circuit according to claim 1, further comprising: A boost circuit, electrically connected to the MCU circuit; And A voltage regulation delay control circuit, electrically connected to both the MCU circuit and the boost circuit to perform delay control on the voltage regulation of the boost circuit.

3. The drive circuit according to claim 2, wherein, The voltage regulation delay control circuit includes a voltage regulation integrated circuit and a feedback circuit formed by a plurality of resistors.

4. The drive circuit according to any one of claims 1 to 3, wherein, The MCU circuit is configured to obtain a light intensity difference based on the first electrical signal and the second electrical signal, and generate a first PWM signal and a second PWM signal with opposite phases through pulse width modulation (PWM) based on the light intensity difference and output them to the H-bridge control circuit to drive and control the H-bridge control circuit.

5. The drive circuit according to claim 4, wherein, The H-bridge control circuit is configured to generate an alternating square wave signal for controlling the driving voltage switch of the liquid crystal film based on the first PWM signal and the second PWM signal.

6. The drive circuit according to claim 5, wherein, The H-bridge control circuit includes an H-bridge circuit composed of four metal-oxide-semiconductor field effect transistors (MOSFETs), and the gate of each of the four MOSFETs is used to receive one of the first PWM signal and the second PWM signal.

7. A dimming rearview mirror, comprising: A liquid crystal film; And The driving circuit according to any one of claims 1 to 6, for driving and controlling the liquid crystal film.

8. The dimming rearview mirror according to claim 7, wherein, The liquid crystal film is a crystal light transmittance conversion (CCS) liquid crystal film.

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