A method and device for adjusting the light of vehicle glass

Abstract

The application discloses a kind of vehicle-mounted glass dimming method and device, it is related to vehicle-mounted glass control technical field, method includes: using front-stage Boost circuit converts input direct-current power into fixed amplitude direct-current bus voltage;Receiving transparency instruction and analysis obtains target drive voltage effective value;Based on target drive voltage effective value and direct-current bus voltage, the modulation ratio of sinusoidal pulse width modulation control signal is calculated;According to the modulation ratio, using unipolar frequency multiplication SPWM mode generates drive signal, to drive the output modulation waveform of rear-stage full-bridge inverter circuit;After filtering processing, it is converted into sinusoidal alternating voltage and drives dimming glass.The application realizes stepless regulation of output voltage by software adjustment modulation ratio, eliminates the dimming delay caused by large-capacity capacitor charging and discharging;At the same time, unipolar frequency multiplication modulation is combined with voltage closed-loop feedback, output high-precision, low-harmonic sinusoidal alternating voltage, effectively avoids dimming glass flicker and liquid crystal molecule polarization damage.

Description

Technical Field

[0001] This invention relates to the field of vehicle glass control technology, specifically a method and device for dimming vehicle glass. Background Technology

[0002] Automotive smart glass is a type of intelligent glass that uses electronic control to change its light transmittance. It is widely used in car sunroofs, side windows, rear windshields, and partitions. Users can adjust the glass's transparency according to light intensity or personal privacy needs, thereby achieving functions such as sun shading, heat insulation, privacy protection, and cabin atmosphere adjustment. Currently, mainstream automotive smart glass is based on liquid crystal technology or electrochromic technology. Their common characteristic is that a specific frequency and amplitude AC driving voltage needs to be applied to both ends of the glass, and the light transmittance is precisely controlled by changing the effective value of the driving voltage.

[0003] Existing dimming methods for automotive smart windows employ direct hardware voltage regulation using Buck-Boost converters, which changes the output voltage by adjusting the amplitude of the DC bus voltage. However, this hardware voltage regulation architecture requires the bus voltage to vary over a wide range with the target voltage. To meet the wide voltage output requirements, complex buck-boost topologies and large-capacity capacitors must be configured, resulting in high system cost and large size. Moreover, the charging and discharging inertia of large-capacity capacitors inevitably introduces a physical delay in voltage establishment, while the temperature drift and ripple of the analog hardware circuitry itself further degrade the output accuracy. This makes it difficult for existing dimming methods for automotive smart windows to simultaneously achieve a balance between cost, response speed, and output quality. Summary of the Invention

[0004] The purpose of this invention is to provide a method and apparatus for dimming vehicle windows to solve the above-mentioned problems.

[0005] The technical solution of this invention is: A method for dimming vehicle windows includes: The input DC power supply is converted into a DC bus voltage of fixed amplitude using a pre-amplitude Boost circuit. Receive a transparency command sent by an external vehicle host, and parse the transparency command to obtain the effective value of the target driving voltage required for the dimming glass; Based on the effective value of the target driving voltage and the DC bus voltage, the modulation ratio of the sinusoidal pulse width modulation (SPWM) control signal is calculated. Based on the modulation ratio, an SPWM control signal is generated using a unipolar frequency doubling SPWM modulation method to drive the subsequent full-bridge inverter circuit. The full-bridge inverter circuit outputs a modulated waveform, which, after being processed by a filter circuit, converts the DC bus voltage into a sinusoidal AC voltage corresponding to the effective value of the target driving voltage, in order to drive the dimming glass.

[0006] Furthermore, the formula for calculating the modulation ratio is: ; in, The target driving voltage RMS value, Where is a fixed DC bus voltage, and m is the modulation ratio. .

[0007] Furthermore, the unipolar frequency-doubling SPWM modulation method specifically includes: A bipolar triangular wave is generated as the carrier signal; A first sinusoidal modulated wave and a second sinusoidal modulated wave are generated. The first modulated wave and the second modulated wave have the same amplitude and frequency, and the first modulated wave and the second modulated wave are 180 degrees out of phase. The amplitude is determined by the modulation ratio. The carrier signal is compared with the first modulated wave and the second modulated wave respectively to generate a first comparison signal and a second comparison signal; Logical operations are performed on the first comparison signal and the second comparison signal to generate an SPWM control signal.

[0008] Furthermore, it also includes output feedback adjustment, which includes the following steps: The voltage signal at the output of the filter circuit is acquired in real time. Calculate the effective value of the actual output voltage and compare it with the effective value of the target drive voltage to obtain the voltage error value; The voltage error value is calculated using a PID control algorithm, and the modulation ratio is corrected in a closed loop based on the calculation result.

[0009] Furthermore, the steps for determining the effective value of the target driving voltage include: A nonlinear mapping table between the light transmittance of the dimming glass and the effective value of the driving voltage is pre-constructed; Receive transparency commands sent by the vehicle's main unit via the CAN bus; Using a lookup table method, the corresponding effective value of the target driving voltage is obtained from the nonlinear mapping table according to the transparency instruction.

[0010] Furthermore, the step of converting the DC power supply into a DC bus voltage of fixed amplitude includes: Control the periodic on and off of the power switch in the Boost circuit; By adjusting the duty cycle of the power switch, the input voltage or load changes are dynamically compensated, and the DC bus voltage is stabilized at a fixed amplitude.

[0011] Furthermore, the filtering circuit is an LC low-pass filter, configured as follows: an inductor and a capacitor are connected in series between the two output arms of the full-bridge inverter circuit to form an LC series branch; the two ends of the capacitor are connected in parallel to the dimming glass as output terminals.

[0012] A vehicle-mounted window dimming device, which dims vehicle-mounted windows using the above method, includes: The boost converter module has an input terminal for connecting to the vehicle's DC power supply and an output terminal for outputting a fixed amplitude DC bus voltage, which is used to control the front-end Boost circuit to convert the input DC power supply into a fixed amplitude DC bus voltage. The instruction parsing module is used to receive the transparency instruction sent by the external vehicle host, and parse the transparency instruction to obtain the effective value of the target driving voltage required for the dimming glass; The modulation calculation module has its first input terminal connected to the output terminal of the instruction parsing module and its second input terminal connected to the output terminal of the boost conversion module. It is used to calculate the modulation ratio of the SPWM control signal based on the effective value of the target driving voltage and the DC bus voltage. The driver generation module, whose input is connected to the output of the modulation calculation module, is used to generate an SPWM control signal according to the modulation ratio using a unipolar frequency doubling SPWM modulation method to drive the subsequent full-bridge inverter circuit. A full-bridge inverter module, whose control terminal is connected to the output terminal of the drive generation module and whose power input terminal is connected to the output terminal of the boost converter module, is used to control the output modulation waveform of the full-bridge inverter circuit. The filter output module has its input terminal connected to the output terminal of the full-bridge inverter module and its output terminal connected to the dimming glass. It is used to process the modulated waveform through the filter circuit and convert the DC bus voltage into a sinusoidal AC voltage corresponding to the effective value of the target driving voltage to drive the dimming glass.

[0013] Furthermore, it also includes: a feedback adjustment module, whose input terminal is connected to the output terminal of the filter output module, and whose output terminal is connected to the input terminal of the modulation calculation module, for real-time acquisition of the voltage signal at the output terminal of the filter circuit, calculation of the effective value of the actual output voltage and comparison with the effective value of the target driving voltage to obtain a voltage error value, calculation of the voltage error value using a PID control algorithm, and closed-loop correction of the modulation ratio based on the calculation result.

[0014] Compared with the prior art, the beneficial effects of the present invention are: This invention utilizes a pre-stage Boost circuit to convert the on-board DC power supply into a DC bus voltage of fixed amplitude, preventing the bus voltage from fluctuating significantly with changes in the target drive voltage. This eliminates the need for complex buck-boost topologies and large-capacity capacitors, greatly reducing system cost and PCB size. Since the bus voltage remains constant and no capacitor charging or discharging is required to establish voltage, the voltage regulation task is entirely transferred to the software layer by adjusting the modulation ratio. This completely eliminates the voltage establishment delay caused by capacitor charging and discharging inertia, achieving a nanosecond-level dynamic response speed. Simultaneously, the software-based voltage regulation method based on the modulation ratio avoids the impact of analog hardware circuit temperature drift, aging, and ripple interference on output accuracy. Combined with the high-purity sine wave output by unipolar frequency-doubled SPWM modulation, it effectively avoids flickering of the dimming glass transmittance and polarization damage to liquid crystal molecules. This significantly improves the user's visual experience while extending the device's lifespan, achieving low-cost, fast-response, and high-precision dimming glass driving. Attached Figure Description

[0015] Figure 1 This is a flowchart of the dimming method of the present invention.

[0016] Figure 2 This is a flowchart of the closed-loop voltage regulation control of the present invention.

[0017] Figure 3 This is a flowchart for solving the effective value of the target driving voltage in this invention.

[0018] Figure 4 This is a flowchart illustrating the generation of SPWM control signals using a unipolar frequency-doubling SPWM modulation method, as described in this invention.

[0019] Figure 5 This is a diagram illustrating the signal source selection principles of the present invention.

[0020] Figure 6 This is a flowchart illustrating the configuration of an LC low-pass filter circuit at the inverter output terminal in this invention.

[0021] Figure 7 This is a flowchart illustrating the output feedback adjustment of the present invention.

[0022] Figure 8 This is a system architecture diagram of the dimming device of the present invention. Detailed Implementation

[0023] The following is combined Figures 1 to 8The specific embodiments of the present invention will be described in detail below. In the description of the present invention, it should be understood that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description, and are not intended to 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 the present invention.

[0024] 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 technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0025] It should be noted that the circuit connections involved in this invention all adopt conventional circuit connection methods and do not involve any innovation.

[0026] Example like Figure 1 As shown in this embodiment, a method for dimming vehicle windows includes the following steps: S1 uses a pre-amplifier Boost circuit to convert the input DC power supply into a DC bus voltage of fixed amplitude.

[0027] Because the vehicle battery voltage may fluctuate with engine start / stop or changes in vehicle electrical load, closed-loop voltage regulation control is used in this step to provide a stable input reference for the subsequent inverter. Figure 2 As shown, the closed-loop voltage regulation control includes the following steps:

[0028] S11 controls the power switch in the Boost circuit to periodically turn on and off.

[0029] By controlling the periodic switching of the power switch in the Boost circuit, the low-voltage vehicle voltage is efficiently and stably boosted to a fixed amplitude. This simplifies the front-end stage from a voltage regulator to a voltage regulator, providing a stable reference for the subsequent stage to achieve precise AC voltage regulation through a pure software algorithm (SPWM modulation ratio adjustment).

[0030] S12. Through real-time sampling feedback, the duty cycle of the power switch is dynamically adjusted to compensate for input voltage fluctuations and load changes, thereby precisely maintaining a constant amplitude of the DC bus voltage. This stable DC bus voltage ( This is the basis for ensuring the stability of light transmittance of the dimming glass.

[0031] S2 receives the transparency command sent by the external vehicle host and obtains the effective value of the target driving voltage required for the dimming glass based on the transparency command.

[0032] like Figure 3 As shown, the steps for solving the effective value of the target driving voltage include: S21. Pre-construct a nonlinear mapping relationship table between the light transmittance of the dimming glass and the effective value of the driving voltage.

[0033] Since the transmittance of dimming glass does not typically exhibit an ideal linear relationship with voltage, direct calculation may introduce errors. Therefore, a nonlinear mapping table between the transmittance of dimming glass and the effective value of the driving voltage is stored in the memory of the microcontroller (MCU).

[0034] S22. The MCU microcontroller communicates with the vehicle's main unit via the CAN bus to receive transparency commands.

[0035] The MCU microcontroller is configured with a preset CAN message identifier (ID).

[0036] The MCU microcontroller monitors the CAN bus in real time. When it captures a CAN message that matches a preset identifier, it extracts the transparency control byte from the CAN message data field.

[0037] The value of the transparency control byte is mapped to a transparency instruction by looking up a table.

[0038] S23. After receiving the transparency command, the corresponding effective value of the target driving voltage is obtained by using a lookup table.

[0039] Based on the received transparency command value, the MCU retrieves the pre-stored mapping table in S21 and quickly and accurately matches the optimal effective value of the driving voltage required to achieve the transparency through direct indexing. ).

[0040] S3, based on the effective value of the target driving voltage and the DC bus voltage, calculates the modulation ratio of the sinusoidal pulse width modulation (SPWM) control signal.

[0041] Since SPWM modulation is based on peak amplitude, the MCU first converts the effective value of the target drive voltage to its peak value (i.e., multiplies it by 0). Subsequently, the microcontroller calculates the modulation ratio m of the SPWM control signal according to the following formula:

[0042] ; in, The target driving voltage RMS value, Where is a fixed DC bus voltage, and m is the modulation ratio. .

[0043] S4, based on the modulation ratio, an SPWM control signal is generated using unipolar frequency-doubled SPWM modulation to drive the subsequent full-bridge inverter circuit. This is the core modulation strategy of this embodiment, designed to reduce switching losses, suppress high-frequency harmonics and electromagnetic interference, and improve output waveform quality. Figure 4 As shown, the specific steps for generating the SPWM control signal using unipolar frequency-doubling SPWM modulation are as follows:

[0044] S41. Obtain the modulating wave signal and the carrier signal. To achieve unipolar frequency doubling modulation, a specific signal source needs to be constructed. For example... Figure 5 As shown, the definition of a signal specifically includes:

[0045] S411. Generate a carrier signal. This carrier signal is a bipolar triangular wave with a frequency much higher than that of the modulating wave signal.

[0046] S412. Generate the first modulation wave. The first modulation wave is a standard sine wave with the same frequency as the target driving voltage, and its amplitude is determined by the modulation ratio m calculated in step S3.

[0047] S413. Generate a second modulated wave. This second modulated wave has the same amplitude and frequency as the first modulated wave, but is 180 degrees out of phase (i.e., out of phase).

[0048] S42. The carrier signal is compared with the first modulating wave and the second modulating wave respectively to generate the first comparison signal and the second comparison signal. The first modulating wave and the second modulating wave are unipolar sinusoidal modulating waves with opposite phases.

[0049] When the first modulated wave is greater than the carrier signal, a first comparison signal is generated; When the second modulated wave is greater than the carrier signal, a second comparison signal is generated.

[0050] Because two inverted modulation waves are used, the two generated comparison signals are complementary in timing.

[0051] S43. Perform logical operations on the first comparison signal and the second comparison signal to generate a square wave signal, which drives the left and right bridge arms of the full-bridge inverter circuit.

[0052] S44, Output the final SPWM control signal.

[0053] At this point, the generated SPWM square wave exhibits frequency doubling characteristics, meaning that the equivalent switching frequency of the square wave is twice the actual switching frequency of a single power switch in the full-bridge inverter circuit. Furthermore, the square wave switches between zero level and the DC bus voltage during both the positive and negative half-cycles (three-level characteristic), rather than switching directly between the positive and negative bus voltages. This significantly suppresses high-frequency harmonics and electromagnetic interference, improving waveform quality.

[0054] S5 controls the output modulation waveform of the full-bridge inverter circuit. After processing by the filter circuit, the DC bus voltage is converted into a sinusoidal AC voltage corresponding to the effective value of the target drive voltage to drive the dimming glass. To restore higher harmonics to a smooth sine wave, such as... Figure 6 As shown, this embodiment configures an LC low-pass filter circuit at the inverter output, including the following steps:

[0055] S51. An inductor (L) and a capacitor (C) are connected in series between the two output arms of the full-bridge inverter circuit to form an LC series branch; the two ends of the capacitor serve as the output terminals of the filter circuit, which are connected in parallel to the dimming load so that the voltage across the load is a sine wave voltage after being smoothed and filtered by the LC circuit.

[0056] The parameter design of the LC filter in this embodiment is based on the frequency domain constraint that the cutoff frequency must be between the output fundamental frequency and twice the carrier frequency. The equivalent switching frequency is increased by using the unipolar frequency doubling effect, thereby achieving miniaturization and weight reduction of the filter device while ensuring the accuracy of the sine waveform, and effectively filtering out the high-frequency switching harmonics generated in S44, while retaining the fundamental component.

[0057] S52. The two ends of the capacitor serve as the output terminals of the filter circuit, which are connected in parallel to the dimming load to ensure that the voltage across the load is a smoothed sinusoidal voltage after being filtered by the LC circuit. After filtering, it directly drives the dimming glass to achieve the desired transparency.

[0058] Furthermore, in order to improve the system's anti-interference capability and output accuracy, such as Figure 7 As shown, this embodiment also includes a closed-loop feedback adjustment step, comprising the following steps: S61. Real-time acquisition of the voltage signal at the output of the filter circuit, i.e., the actual voltage across the dimming glass.

[0059] S62. Calculate the effective value of the actual output voltage and compare it with the effective value of the target driving voltage obtained in S2 to obtain the voltage error value.

[0060] S63. The voltage error value is calculated using the PID (proportional-integral-derivative) control algorithm, and the modulation ratio in S3 is corrected in real time based on the calculation result.

[0061] Closed-loop correction can effectively compensate for output errors caused by DC bus voltage fluctuations or changes in the load impedance of the dimming glass, ensuring the stability of light transmittance.

[0062] like Figure 8 As shown, the vehicle-mounted glass dimming device of this embodiment uses the above-mentioned dimming method to dim the vehicle-mounted glass, including: an instruction parsing module, a boost conversion module, a modulation calculation module, a drive generation module, a full-bridge inverter module, a filter output module, and a feedback adjustment module.

[0063] The input terminal of the boost converter module is used to connect to the vehicle DC power supply, and the output terminal outputs a DC bus voltage of fixed amplitude, which is used to control the front-end Boost circuit to convert the input DC power supply into a DC bus voltage of fixed amplitude. The instruction parsing module is used to receive transparency instructions sent by the external vehicle host, and to parse the effective value of the target driving voltage required for the dimming glass based on the transparency instructions; The first input terminal of the modulation calculation module is connected to the output terminal of the instruction parsing module, and the second input terminal is connected to the output terminal of the boost conversion module. It is used to calculate the modulation ratio of the SPWM control signal based on the effective value of the target drive voltage and the DC bus voltage. The input of the driver generation module is connected to the output of the modulation calculation module. It is used to generate an SPWM control signal according to the modulation ratio using a unipolar frequency doubling SPWM modulation method to drive the subsequent full-bridge inverter circuit. The control terminal of the full-bridge inverter module is connected to the output terminal of the drive generation module, and the power input terminal is connected to the output terminal of the boost converter module, which is used to control the output modulation waveform of the full-bridge inverter circuit. The input terminal of the filter output module is connected to the output terminal of the full-bridge inverter module, and the output terminal is used to connect to the dimming glass. It is used to process the modulated waveform through the filter circuit and convert the DC bus voltage into a sinusoidal AC voltage corresponding to the effective value of the target drive voltage to drive the dimming glass.

[0064] The input of the feedback adjustment module is connected to the output of the filter output module, and the output is connected to the input of the modulation calculation module. It is used to collect the voltage signal at the output of the filter circuit in real time, calculate the effective value of the actual output voltage and compare it with the effective value of the target driving voltage to obtain the voltage error value. The voltage error value is calculated using a PID control algorithm, and the modulation ratio is corrected in a closed loop based on the calculation result.

[0065] This embodiment controls the front-end Boost circuit to convert the input vehicle DC power supply into a DC bus voltage of fixed amplitude; then it receives the transparency command sent by the external vehicle host and analyzes it to obtain the effective value of the target driving voltage required for the dimming glass; based on the relationship between the effective value of the target driving voltage and the DC bus voltage, it calculates the modulation ratio of the SPWM control signal; according to the modulation ratio, it generates the SPWM control signal using a unipolar frequency doubling SPWM modulation method; the SPWM control signal drives the output modulation waveform of the rear full-bridge inverter circuit; after the obtained modulation waveform is processed by the filtering circuit, the DC bus voltage is converted into a sinusoidal AC voltage corresponding to the effective value of the target driving voltage to drive the dimming glass.

[0066] Abandoning the traditional approach of relying on Buck-Boost circuits for direct hardware voltage regulation, this solution first utilizes a pre-stage Boost circuit to convert fluctuating automotive power supplies into a constant-amplitude DC bus voltage. This eliminates the need for complex switching buck-boost topologies, significantly reducing the number of power devices and magnetic components, thereby drastically lowering BOM costs and PCB size, meeting the miniaturization and lightweight requirements of automotive-grade products. Secondly, the SPWM modulation ratio is directly calculated based on the target voltage resolution, and stepless voltage regulation is achieved by adjusting the switching duty cycle of the full-bridge inverter circuit. This software-defined voltage approach completely eliminates the voltage build-up lag caused by the charging and discharging of large-capacity bus capacitors in traditional solutions, achieving nanosecond-level dynamic response speeds and resolving dimming delay issues.

[0067] Furthermore, by combining unipolar frequency doubling modulation and PID closed-loop correction algorithm, not only are high-frequency harmonics and electromagnetic interference (EMI) significantly suppressed, but a high-purity sine wave is also output, effectively avoiding the lifespan degradation of the dimming glass caused by harmonic heating. This achieves a dual improvement in high performance and high reliability. It can also compensate for output errors caused by bus voltage fluctuations or load changes in real time, ensuring that the sinusoidal AC voltage driving the dimming glass has extremely high accuracy, smooth waveform, and low harmonic content. This effectively avoids glass transmittance flicker and prevents polarization damage to liquid crystal molecules, significantly improving the user's visual experience while effectively extending the system's lifespan.

[0068] The above-disclosed embodiments are merely preferred embodiments of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A method for dimming vehicle windows, characterized in that, include: The input DC power supply is converted into a DC bus voltage of fixed amplitude using a pre-amplitude Boost circuit. Receive a transparency command sent by an external vehicle host, and parse the transparency command to obtain the effective value of the target driving voltage required for the dimming glass; Based on the effective value of the target driving voltage and the DC bus voltage, the modulation ratio of the sinusoidal pulse width modulation control signal is calculated. Based on the modulation ratio, an SPWM control signal is generated using a unipolar frequency doubling SPWM modulation method to drive the subsequent full-bridge inverter circuit. The full-bridge inverter circuit outputs a modulated waveform, which, after being processed by a filter circuit, converts the DC bus voltage into a sinusoidal AC voltage corresponding to the effective value of the target driving voltage, in order to drive the dimming glass.

2. The method for dimming vehicle windows according to claim 1, characterized in that, The unipolar frequency-doubling SPWM modulation method specifically includes: A bipolar triangular wave is generated as the carrier signal; A first sinusoidal modulated wave and a second sinusoidal modulated wave are generated. The first modulated wave and the second modulated wave have the same amplitude and frequency, and the first modulated wave and the second modulated wave are 180 degrees out of phase. The amplitude is determined by the modulation ratio. The carrier signal is compared with the first modulated wave and the second modulated wave respectively to generate a first comparison signal and a second comparison signal; Logical operations are performed on the first comparison signal and the second comparison signal to generate an SPWM control signal.

3. The method for dimming vehicle windows according to claim 1, characterized in that, It also includes output feedback adjustment, which includes the following steps: The voltage signal at the output of the filter circuit is acquired in real time. Calculate the effective value of the actual output voltage and compare it with the effective value of the target drive voltage to obtain the voltage error value; The voltage error value is calculated using a PID control algorithm, and the modulation ratio is corrected in a closed loop based on the calculation result.

4. The method for dimming vehicle windows according to claim 1, characterized in that, The steps for determining the effective value of the target driving voltage include: A nonlinear mapping table between the light transmittance of the dimming glass and the effective value of the driving voltage is pre-constructed; Receive transparency commands sent by the vehicle's main unit via the CAN bus; Using a lookup table method, the corresponding effective value of the target driving voltage is obtained from the nonlinear mapping table according to the transparency instruction.

5. The method for dimming vehicle windows according to claim 1, characterized in that, The steps for converting the DC power supply into a DC bus voltage of fixed amplitude include: Control the periodic on and off of the power switch in the Boost circuit; By adjusting the duty cycle of the power switch, the input voltage or load changes are dynamically compensated, and the DC bus voltage is stabilized at a fixed amplitude.

6. The method for dimming vehicle windows according to claim 1, characterized in that, The formula for calculating the modulation ratio is: ； in, The target driving voltage RMS value, Where is a fixed DC bus voltage, and m is the modulation ratio. .

7. The method for dimming vehicle windows according to claim 1, characterized in that, The filtering circuit is an LC low-pass filter, configured as follows: an inductor and a capacitor are connected in series between the two output arms of the full-bridge inverter circuit to form an LC series branch; the two ends of the capacitor are connected in parallel to the dimming glass as output terminals.

8. A vehicle-mounted glass dimming device, characterized in that, The method for dimming vehicle windows according to any one of claims 1-7 includes: The boost converter module has an input terminal for connecting to the vehicle's DC power supply and an output terminal for outputting a fixed-amplitude DC bus voltage. It is used to control the front-end Boost circuit to convert the input DC power supply into a fixed-amplitude DC bus voltage. The instruction parsing module is used to receive the transparency instruction sent by the external vehicle host, and parse the transparency instruction to obtain the effective value of the target driving voltage required for the dimming glass; The modulation calculation module has a first input terminal connected to the output terminal of the instruction parsing module and a second input terminal connected to the output terminal of the boost conversion module. It is used to calculate the modulation ratio of the SPWM control signal based on the effective value of the target driving voltage and the DC bus voltage. The driver generation module, whose input is connected to the output of the modulation calculation module, is used to generate an SPWM control signal according to the modulation ratio using a unipolar frequency doubling SPWM modulation method to drive the subsequent full-bridge inverter circuit. The full-bridge inverter module has its control terminal connected to the output terminal of the drive generation module and its power input terminal connected to the output terminal of the boost converter module, and is used to control the output modulation waveform of the full-bridge inverter circuit. The filter output module has its input end connected to the output end of the full-bridge inverter module and its output end connected to the dimming glass. It is used to process the modulated waveform through the filter circuit and convert the DC bus voltage into a sinusoidal AC voltage corresponding to the effective value of the target driving voltage to drive the dimming glass.

9. A vehicle-mounted glass dimming device according to claim 8, characterized in that, Also includes: The feedback adjustment module has its input end connected to the output end of the filter output module and its output end connected to the input end of the modulation calculation module. It is used to collect the voltage signal at the output end of the filter circuit in real time, calculate the effective value of the actual output voltage and compare it with the effective value of the target driving voltage to obtain the voltage error value, use a PID control algorithm to calculate the voltage error value, and perform closed-loop correction on the modulation ratio based on the calculation result.

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