Laser projection apparatus, control method and laser device control circuit

Abstract

The present disclosure relates to the technical field of display. Provided are a laser projection apparatus, a control method and a laser device control circuit, the laser projection apparatus comprising a laser device (40), a light modulation device (50), a projection lens (60), a display control circuit (20), and a laser control circuit (30). The display control circuit (20) is used for outputting a dimming driving signal and an image display driving signal. The light modulation device (50) is used for modulating a laser beam under the driving of the image display driving signal. The laser control circuit (30) comprises a controller (31) and a driving circuit (32), the controller (31) being used for generating control signals on the basis of the dimming driving signal, and the driving circuit (32) being used for generating, on the basis of the control signals, a power supply signal for supplying power to the corresponding laser device (40). The control signals comprise a first control signal and a second control signal, the first control signal being a constant-level signal and the second control signal being a PWM signal.

Description

Laser projection equipment, control method and laser control circuit

[0001] The present disclosure claims priority to Chinese patent application No. 202310805812.2 filed on June 30, 2023, entitled “Laser projection device and control method thereof”, application No. 202310799073.0 filed on June 30, 2023, entitled “Laser projection device and control method thereof”, application No. 202310805807.1 filed on June 30, 2023, entitled “Laser projection device and control method thereof”, and application No. 202310992159.5 filed on August 8, 2023, entitled “Laser projection device, control method and laser driving module”, the entire contents of which are incorporated by reference into the present disclosure. Technical Field

[0002] The present disclosure relates to the field of display technology, and in particular to a laser projection device, a control method, and a laser control circuit. Background Art

[0003] Laser projection equipment uses digital light processing (DLP) technology to digitally process image signals and then project them through a laser beam. Laser projection equipment has the characteristics of vivid colors, high brightness, and flexible screen size, and has been widely used. Laser projection equipment includes monochrome, dual-color, and tri-color lasers, and each laser is powered by a corresponding laser control circuit. In laser projection equipment that includes multi-color lasers, multiple lasers are lit in turn.

[0004] In related technologies, a laser control circuit includes a controller, a switching transistor, and an energy storage element. After receiving a start signal, the controller outputs a control signal, a pulse-width modulated (PWM) signal, which controls the opening and closing of the switching transistor. This switching control charges and discharges the energy storage element, and startup is complete when the stored charge in the energy storage element reaches a reference power supply value. The brightness of the corresponding laser is then adjusted by adjusting the duty cycle of the PWM signal.

[0005] However, in the related art, the startup speed of the laser control circuit is slow, so that the laser cannot be lit in time, thereby affecting the display effect of the laser projection device.

[0006] Summary of the Invention

[0007] The present disclosure provides a laser projection device, a control method, and a laser control circuit, which can improve the display effect of the laser projection device. The technical solutions of the laser projection device, the control method, and the laser control circuit are as follows.

[0008] In a first aspect, the present disclosure provides a laser projection device. The laser projection device includes a laser light source, a light modulation device, a projection lens, a display control circuit, and at least one laser control circuit. The laser light source includes at least one laser, each corresponding to at least one laser control circuit. The laser is configured to emit a laser beam. The display control circuit is configured to output a dimming drive signal and an image display drive signal. The dimming drive signal includes an image enable signal and a brightness control signal. The light modulation device is configured to modulate the laser beam under the image display drive signal. The projection lens is configured to receive the modulated laser beam and project an image. The laser control circuit includes a controller and a driver circuit. The controller is connected to the display control circuit and the driver circuit. The controller generates a control signal based on the image enable signal and the brightness control signal. The driver circuit is connected to the corresponding laser. The driver circuit generates a power supply signal to the corresponding laser based on the control signal. The control signal includes a first control signal and a second control signal. The first control signal is a constant-level signal output by the controller when the image enable signal transitions from an inactive level to an active level and the power supply signal does not reach a reference power supply value corresponding to the brightness control signal. The second control signal is a PWM signal output by the controller when the image enable signal is at a valid level and the power supply signal reaches a reference power supply value corresponding to the brightness control signal.

[0009] In a second aspect, the present disclosure provides a control method. The control method is applied to a laser projection device such as the first aspect. The control method includes: a laser emits a laser beam to provide an illumination beam for the device; a display control circuit outputs a dimming drive signal and an image display drive signal, wherein the dimming drive signal includes an image enable signal and a brightness control signal; a light modulation device modulates the laser beam under the drive of the image display drive signal; a projection lens receives the modulated laser beam and projects an image; a controller generates a control signal based on the image enable signal and the brightness control signal; a drive circuit generates a power supply signal to the corresponding laser based on the control signal; wherein the control signal includes a first control signal and a second control signal; the first control signal is a constant level signal output by the controller when the image enable signal is converted from an invalid level to a valid level and the power supply signal does not reach the reference power supply value corresponding to the brightness control signal; the second control signal is a PWM signal output by the controller when the image enable signal is at a valid level and the power supply signal reaches the reference power supply value corresponding to the brightness control signal.

[0010] In a third aspect, the present disclosure provides a laser control circuit. The laser control circuit includes a controller and a drive circuit. The controller is connected to the display control circuit and the drive circuit, and the controller is used to generate a control signal based on an image enable signal and a brightness control signal. The drive circuit is connected to the corresponding laser, and the drive circuit is used to generate a power supply signal to supply power to the corresponding laser based on the control signal. The control signal includes a first control signal and a second control signal; the first control signal is a constant level signal output by the controller when the image enable signal is converted from an invalid level to a valid level and the power supply signal does not reach the reference power supply value corresponding to the brightness control signal; the second control signal is a PWM signal output by the controller when the image enable signal is a valid level and the power supply signal reaches the reference power supply value corresponding to the brightness control signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG1 is a schematic diagram of a laser projection device provided by an embodiment of the present disclosure;

[0012] FIG2 is a schematic diagram of a circuit architecture of a laser projection device provided by an embodiment of the present disclosure;

[0013] FIG3 is a circuit diagram of a laser projection device provided by an embodiment of the present disclosure;

[0014] FIG4 is a circuit diagram of a laser projection device provided by an embodiment of the present disclosure;

[0015] FIG5 is a timing diagram of an image enable signal of a laser provided by an embodiment of the present disclosure;

[0016] FIG6 is a circuit diagram of a laser projection device provided by an embodiment of the present disclosure;

[0017] FIG7 is a timing diagram of various control signals in the related art;

[0018] FIG8 is a timing diagram of various control signals provided by an embodiment of the present disclosure;

[0019] FIG9 is a circuit diagram of another laser projection device provided by an embodiment of the present disclosure;

[0020] FIG10 is a circuit diagram of another laser projection device provided by an embodiment of the present disclosure;

[0021] FIG11 is a circuit diagram of another laser projection device provided by an embodiment of the present disclosure;

[0022] FIG12 is a circuit diagram of another laser projection device provided by an embodiment of the present disclosure;

[0023] FIG13 is another timing diagram of various control signals provided by an embodiment of the present disclosure;

[0024] FIG14 is a circuit diagram of another laser projection device provided by an embodiment of the present disclosure;

[0025] FIG15 is a circuit diagram of another laser projection device provided by an embodiment of the present disclosure;

[0026] FIG16 is a circuit diagram of another laser projection device provided by an embodiment of the present disclosure;

[0027] FIG17 is a circuit diagram of another laser projection device provided by an embodiment of the present disclosure;

[0028] FIG18 is a waveform diagram of an initial power supply current provided by an embodiment of the present disclosure;

[0029] FIG19 is a circuit diagram of another laser projection device provided by an embodiment of the present disclosure;

[0030] FIG20 is a waveform diagram of an initial power supply current provided by an embodiment of the present disclosure;

[0031] FIG21 is a circuit diagram of another laser projection device provided by an embodiment of the present disclosure;

[0032] FIG22 is a waveform diagram of another initial power supply current provided by an embodiment of the present disclosure;

[0033] FIG23 is a circuit diagram of another laser projection device provided by an embodiment of the present disclosure;

[0034] FIG24 is a circuit diagram of another laser projection device provided by an embodiment of the present disclosure;

[0035] FIG25 is a circuit diagram of a current regulation circuit provided by an embodiment of the present disclosure;

[0036] FIG26 is a circuit diagram of another current regulation circuit provided by an embodiment of the present disclosure;

[0037] FIG27 is a circuit diagram of another current regulation circuit provided by an embodiment of the present disclosure;

[0038] FIG28 is a circuit diagram of another current regulation circuit provided by an embodiment of the present disclosure;

[0039] FIG29 is a circuit diagram of another laser projection device provided by an embodiment of the present disclosure;

[0040] FIG30 is a circuit diagram of another laser projection device provided by an embodiment of the present disclosure;

[0041] FIG31 is a circuit diagram of another laser projection device provided by an embodiment of the present disclosure;

[0042] FIG32 is a circuit diagram of another laser projection device provided by an embodiment of the present disclosure;

[0043] FIG33 is a circuit diagram of another current regulation circuit provided by an embodiment of the present disclosure;

[0044] FIG34 is a circuit diagram of another current regulation circuit provided by an embodiment of the present disclosure;

[0045] FIG35 is a circuit diagram of another current regulation circuit provided by an embodiment of the present disclosure;

[0046] FIG36 is a circuit diagram of another current regulation circuit provided by an embodiment of the present disclosure;

[0047] FIG37 is a circuit diagram of another laser projection device provided by an embodiment of the present disclosure;

[0048] FIG38 is a flow chart of a control method provided by an embodiment of the present disclosure;

[0049] FIG39 is a schematic diagram of the hardware structure of an electronic device provided in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0050] The following explains the terms involved in the embodiments of the present disclosure.

[0051] PFC (Power Factor Correction): Power factor correction refers to the relationship between active power and total power consumption (apparent power), or the ratio of active power to total power consumption (apparent power). The basic operating principle of a PFC-regulated switching power supply is to use inductor compensation to adjust the input current waveform to be as similar as possible to the input voltage waveform, achieving a power factor correction value close to 100%.

[0052] LLC: A resonant circuit that achieves a constant output voltage by controlling the switching frequency (frequency regulation). A single-port network consisting of an inductor, capacitor, and resistor is said to resonate when the port voltage and current waveforms are in phase at certain operating frequencies. A circuit capable of resonance is called a resonant circuit.

[0053] The bridge rectifier circuit is the most widely used rectifier circuit in power supply circuits. It consists of four diodes with the same direction and a transformer. Rectification is the process of converting alternating current (AC) into direct current (DC). Using unidirectional conductive devices, it can convert alternating current (AC) with varying direction and magnitude into DC.

[0054] The following describes the technical solutions provided by the embodiments of the present disclosure.

[0055] FIG1 is a schematic diagram of a laser projection device provided by an embodiment of the present disclosure, wherein the laser projection device includes a laser TV, a projector device of a laser beam scanning system, a head-mounted display, a stereoscopic (3D) display, and the like.

[0056] As shown in Figure 1, after the upper shell of the laser projection device is disassembled, the internal structure is divided according to the optical function, including a light source 100, an optical engine 200, and a lens 300. Among them, the light source 100 is used to provide an illumination beam, which is transmitted to the rear-end optical modulation device and the projection lens. The light source 100 includes a laser of at least one color, such as a blue laser, or a dual-light laser, such as a blue laser and a red laser, or a three-color laser light source, including lasers of three colors: red, green, and blue.

[0057] The laser beam provided by light source 100 is combined and shaped before entering the illumination path of optical engine 200. In the DLP projection architecture, the DMD chip is the core optical modulation device. The DMD chip receives a drive control signal corresponding to the image signal and flips the thousands of tiny mirrors on its surface to either a positive or negative angle in response to the drive signal, reflecting the incoming light beam into lens 300.

[0058] In some examples, the lens 300 is an ultra-short-throw projection lens, which is used to project an image beam onto a projection screen to display a projected image. Accordingly, the laser projection device is an ultra-short-throw laser projection device.

[0059] Figure 2 shows a schematic diagram of the circuit architecture of a laser projection device. As shown in Figure 2, the laser projection device includes a display panel 001, a power supply board 002, and a TV board 003. Among them, the power supply board 002 is connected to the display panel 001 and the TV board 003 respectively. The power supply board 002 is used to power various devices or partial modules on the display panel 001 and the TV board 003. At the same time, it also powers other functional modules in the laser projection device, such as the human eye protection module, fan, WIFI module, etc., to ensure the normal power supply of various parts of the laser projection device. In some examples, a laser control circuit is also provided on the power supply board 002. Alternatively, the laser control circuit is provided independently of the power supply board 002.

[0060] In some examples, as shown in FIG19 , the input end of the power supply board 002 receives AC power, and the output end is connected to the laser control circuit 30. The power supply board 002 includes a rectifier bridge circuit 12 and a power conversion circuit 11. The rectifier bridge circuit 12 is a full-bridge or half-bridge rectifier circuit for rectifying the AC AC power into a DC signal. The power conversion circuit 11 is a flyback circuit or a PFC+LLC circuit for performing power conversion processing on the DC signal and outputting a DC power signal corresponding to the load.

[0061] TV board 003 is primarily used to receive and decode external audio and video signals and output video image signals. TV board 003 is equipped with a system-on-chip (SoC) that can decode data in various formats into a normalized format and transmit the normalized data to display board 001 via, for example, a connector. The video image signals output by TV board 003 are transmitted to display board 001.

[0062] The display panel 001 may be provided with an algorithm processing circuit 10 and a display control circuit 20. The algorithm processing circuit 10 is used to process the input video image signal, such as performing MEMC frequency multiplication processing or image correction to implement image enhancement functions. The display control circuit 20 is connected to the algorithm processing circuit 10, and the display control circuit 20 is used to receive the processed video image signal data as image data to be displayed. It should be noted that in some examples, the algorithm processing circuit 10 is implemented by a field programmable gate array (FPGA). The algorithm processing circuit 10 usually exists as an enhancement function circuit. In some low-cost solutions, this circuit part may not be provided, and the display control circuit 20 may receive the video image signal output by the TV panel 003.

[0063] The display control circuit 20 mainly includes a digital light processing chip (DLP) and may also include a driver chip. The display control circuit 20 is used to output an image display drive signal and an output dimming drive signal (also called a laser drive signal or dimming signal). The dimming drive signal includes an image enable signal and a brightness control signal. The image display drive signal is used to drive the light modulator, which modulates the laser beam under the drive of the image display drive signal. The projection lens is used to receive the modulated laser beam and project the image.

[0064] In the DLP control architecture, the light source part needs to cooperate with the working timing of the DLP chip and the DMD chip. Specifically, the DLP chip outputs an image enable signal, which can also be called a primary color light enable signal, usually expressed as X_EN, where X is the abbreviation of different primary color lights, and also outputs a brightness control signal, referred to as a PWM signal. Along with the DMD chip's temporal modulation process of different primary color image components, the light source part needs to synchronously output the primary color light beams of the corresponding colors. That is, the DLP chip outputs a primary color light enable signal to notify the laser light source to enable the lighting of a certain color laser, and outputs a brightness control signal to notify a certain laser in the laser light source at what brightness to light up.

[0065] As shown in FIG2 , the display control circuit 20 is used to generate an image display drive signal for driving the light modulator 50 based on the image signal to be displayed. Furthermore, since the display of the projected image requires the synchronous coordination of the light source beam and the light modulator, the display control circuit 20 also generates a dimming drive signal. The dimming drive signal includes an image enable signal and a brightness control signal, such as a current PWM signal. The image enable signal is a timing control signal used to coordinate the timing of the output of different color lights, while the current PWM signal is a periodic square wave signal used to provide a current signal for igniting the laser.

[0066] Furthermore, the circuit architecture diagram of the laser projection device shown in FIG2 also includes a laser control circuit 30. The laser control circuit 30 is used to receive the image enable signal and brightness control signal output by the display control circuit 20, as well as the power input voltage from the power board 002, and directly control the lighting of the laser 40.

[0067] In the figure, the laser 40 can be a single-color laser or a multi-color laser. In some examples, as shown in Figure 3, the laser 40 includes three groups of lasers of different colors, namely a blue laser 41 emitting blue laser light, a red laser 42 emitting red laser light, and a green laser 43 emitting green laser light. Each of the above lasers can be a multi-package chip laser. In some examples, three light-emitting chips are packaged in one tube shell. In other examples, three light-emitting chips are packaged in multiple (e.g., two) tube shells.

[0068] In some examples, as shown in FIG3 , the display control circuit 20 outputs a blue PWM signal B_PWM corresponding to the blue laser 41 based on the blue primary color component of the image to be displayed, outputs a red PWM signal R_PWM corresponding to the red laser 42 based on the red primary color component of the image to be displayed, and outputs a green PWM signal G_PWM corresponding to the green laser 43 based on the green primary color component of the image to be displayed.

[0069] The display control circuit 20 can output an image enable signal B_EN0 corresponding to the blue laser 41 based on the lighting duration of the blue laser 41 within the driving cycle, output an image enable signal R_EN0 corresponding to the red laser 42 based on the lighting duration of the red laser 42 within the driving cycle, and output an image enable signal G_EN0 corresponding to the green laser 43 based on the lighting duration of the green laser 43 within the driving cycle. In other words, the image enable signal is a periodic PWM signal. For example, when the red laser 42 is lit based on the high level of the corresponding image enable signal R_EN0, the other two lasers are not working based on the low level of the corresponding image enable signal, thereby realizing the rotation of different lasers.

[0070] In the related art, the laser control circuit 30 includes a controller, a switch tube, and an energy storage element. The controller receives a corresponding image enable signal and a brightness control signal. The image enable signal is used to control the state of the controller. When the image enable signal changes from a low level to a high level, the controller starts to start and outputs a PWM control signal. The control signal is used to control the opening and closing of the switch tube. By opening and closing the switch tube, the energy storage element is charged and discharged. When the stored power in the energy storage element reaches the reference power supply value, the startup is completed, and then the brightness of the corresponding laser is adjusted by adjusting the duty cycle of the PWM signal.

[0071] However, in the related art, the startup speed of the laser control circuit 30 is slow, so that the laser cannot be lit in time, thereby affecting the display effect of the laser projection device.

[0072] In view of the above problems, an embodiment of the present disclosure provides a laser projection device. In this laser projection device, when the laser control circuit 30 is started, it outputs a first control signal of a constant level, and after startup, it outputs a second control signal of a PWM signal. Compared to the PWM signal, the constant level first control signal can continuously charge the energy storage element, thereby accelerating the charging speed of the energy storage element, allowing the power supply signal to quickly reach the reference power supply value, thereby increasing the startup speed of the laser control circuit 30 and thus the lighting speed of the laser.

[0073] As shown in Figure 4, the laser projection device includes a laser light source, a light modulation device 50, a projection lens 60, a display control circuit 20, and a laser control circuit 30. The laser light source includes at least one laser 40, which is used to emit a laser beam to provide an illumination beam for the device. There is a one-to-one correspondence between each laser 40 and the laser control circuit 30.

[0074] The display control circuit 20 is configured to output a dimming drive signal and an image display drive signal, wherein the dimming drive signal includes an image enable signal and a brightness control signal.

[0075] The light modulator 50 is used to modulate the laser beam under the drive of the image display drive signal.

[0076] The projection lens 60 is used to receive the modulated laser beam and project an image.

[0077] The laser control circuit 30 includes a controller 31 and a drive circuit 32. The controller 31 is connected to the display control circuit 20 and the drive circuit 32. The controller 31 is used to generate a control signal (or drive signal) based on the image enable signal and the brightness control signal. The drive circuit 32 is connected to the corresponding laser 40. The drive circuit 32 is used to generate a power supply signal to the corresponding laser 40 based on the control signal. Among them, the control signal includes a first control signal and a second control signal. The first control signal is a constant level signal output by the controller 31 when the image enable signal is converted from an invalid level to a valid level and the power supply signal does not reach the reference power supply value corresponding to the brightness control signal. The second control signal is a PWM signal output by the controller 31 when the image enable signal is at a valid level and the power supply signal reaches the reference power supply value corresponding to the brightness control signal.

[0078] It should be noted that the display control circuit 20 may also be referred to as a display control module, the laser control circuit 30 may also be referred to as a laser driving module or a laser driving module, and the brightness control signal may also be referred to as a power supply control signal.

[0079] As shown in Figure 4, the laser control circuit 30 includes a controller 31 and a drive circuit 32. The controller 31 receives the corresponding image enable signal and brightness control signal output by the display control circuit 20. As can be seen from the above example, the brightness control signal is used to control the magnitude of the power supply signal output by the laser control circuit 30, thereby controlling the brightness of the laser 40.

[0080] The brightness control signal represents the brightness of the corresponding color in the image to be displayed. The brightness control signal can be ADIM, which can be an analog signal converted from a digital signal. Exemplarily, the laser control circuit 30 further includes a digital-to-analog converter (DAC). The display control circuit 20 sends a brightness control signal in a digital format, such as a PWM signal, and the DAC circuit converts the PWM signal into an ADIM in an analog format. The DAC circuit can be integrated into the display control circuit 20 or into the controller 31. It should be noted that, in the case where the DAC circuit is integrated into the display control circuit 20, the display control circuit 20 directly sends the brightness control signal in ADIM format to the controller 31. In the case where the DAC circuit is integrated into the controller 31, the display control circuit 20 sends the brightness control signal in PWM format to the controller 31 (as shown in FIG. 3 ). After receiving the brightness control signal in PWM format, the controller 31 converts the brightness control signal in PWM format into a brightness control signal in ADIM format.

[0081] ADIM and the reference power supply value have a corresponding relationship. Based on the corresponding relationship, the reference power supply value corresponding to the current ADIM can be obtained, and the reference power supply value can characterize the power supply signal required for the laser 40 to reach the brightness corresponding to the image to be displayed. For example, ADIM=0.1I_base, when ADIM is 0.2A, the corresponding reference power supply value 0.1I_base is 2A. It should be noted that in the constant current controlled laser control circuit 30, the reference power supply value is the reference current value, and in the constant voltage controlled laser control circuit 30, the reference power supply value is the reference voltage value. To facilitate the understanding of the embodiments of the present disclosure, the following description is based on the reference power supply value as the reference current value.

[0082] The image enable signal EN is a timing control signal used to coordinate the timing of the output of different color lights. Figure 5 is a timing diagram of the image enable signal EN for a laser in an example. As shown in Figure 5, the active level is high, and the inactive level is low. When R_EN is high, the laser control circuit 30 corresponding to the red laser 42 operates, and the red laser 42 is illuminated. The laser control circuit 30 corresponding to the green laser 43 and the laser control circuit 30 corresponding to the blue laser 41 do not operate, and the green laser 43 and the blue laser 41 do not light. R_EN, G_EN, and B_EN are sequentially high, so the three lasers 40 are illuminated in sequence.

[0083] It will be appreciated that when the EN signal received by the laser control circuit 30 transitions from an inactive level to an active level, it indicates that the corresponding laser 40 of the laser control circuit 30 has its turn to illuminate, and the laser control circuit 30 begins to start. In this embodiment, during startup, the controller 31 outputs a first control signal Gate1 at a constant level. This constant level can increase the speed at which the power supply signal reaches the reference power supply value. This will be explained below with reference to an example.

[0084] Figure 6 is a schematic diagram of the structure of a laser control circuit 30. As shown in Figure 6, the drive circuit 32 includes an eighth resistor R8, a first inductor L1, a first diode VD1, a third switching transistor V3, and a fifth capacitor C5. One end of the eighth resistor R8 is connected to the controller 31 and receives the power input signal Vin output by the power supply board 002. The other end of the eighth resistor R8 is connected to the controller 31 and one end of the third switching transistor V3. The other end of the third switching transistor V3 is connected to the cathode of the first diode VD1 and one end of the first inductor L1. The control end of the third switching transistor V3 is connected to the controller 31 to receive the control signal. The other end of the first inductor L1 serves as an output end and is connected to one end of the fifth capacitor C5 and the anode of the laser 40. The other end of the fifth capacitor C5 is connected to the anode of the first diode VD1 and the cathode of the laser 40, and is grounded.

[0085] During operation, the controller 31 outputs a control signal Gate, which is connected to the control terminal of the third switch tube V3 to control the opening and closing of the third switch tube V3. The third switch tube V3 is a P-type or N-type MOS tube, or a triode. The first inductor L1 and the fifth capacitor C5 are energy storage elements. When the third switch tube V3 is closed (or turned on), the fifth capacitor C5 and the first inductor L1 are charged, and the power supply output signal Vin supplies power to the first inductor L1 and the laser 40. When the third switch tube V3 is turned off, the first inductor L1 and the fifth capacitor C5 discharge and output the power supply voltage V out , to power the laser 40. Wherein, V out The size of V is determined by the on-off time of the third switch tube V3. The longer the on time of the third switch tube V3 is, the shorter the off time is. out The larger the duty cycle, the smaller the duty cycle. Therefore, the on-off time of the third switch tube V3 can be controlled based on the duty cycle of the control signal, thereby realizing the control of the power supply current of the laser 40. The two ends of the eighth resistor R8 are connected to different pins of the controller 31. The eighth resistor R8 is a sampling resistor. Based on the voltage (or current) across the sampling resistor, the power supply current flowing through the laser 40 is obtained. If the power supply current of the laser 40 is less than the reference current value, the duty cycle of the drive signal Gate is reduced to increase the power supply current of the laser 40; conversely, if the power supply current of the laser 40 is greater than the reference current value, the duty cycle of the drive signal Gate is increased to reduce the power supply current of the laser 40, so that the power supply current of the laser 40 is maintained at the reference current value corresponding to the current brightness control signal ADIM.

[0086] FIG6 shows an example in which the laser control circuit 30 is a step-down circuit. In practical applications, the laser control circuit 30 may also be a step-up circuit, which is not limited in this embodiment.

[0087] It should be noted that, referring to FIG6 , before the laser control circuit 30 is started, the charge in the first inductor L1 and the fifth capacitor C5 is zero. During startup, the first inductor L1 and the fifth capacitor C5 must first be charged. The first inductor L1 blocks direct current, causing the supply current flowing through the laser 40 to gradually increase until it reaches a reference current value. In the related art, during startup, the controller 31 outputs a fixed-frequency PWM signal as a control signal. This requires an intermittent charging process before the supply current flowing through the laser 40 reaches the reference current value, thus taking a longer time to reach the reference current value. In contrast, in this embodiment, a constant-level first control signal is output during startup. Since the first control signal is a constant level, the third switch V3 remains on, continuously charging the first inductor L1 and the fifth capacitor C5. This allows the supply current flowing through the laser 40 to quickly reach the reference current value, thereby improving startup speed.

[0088] The following is an illustrative explanation in conjunction with actual scenarios: Figure 7 is a timing diagram of each control signal in the related art. As shown in Figure 7, the invalid level is a low level and the valid level is a high level. At time t1, the image enable signal EN changes from a low level to a high level, wherein when EN is at a low level, the laser control circuit 30 enters the standby state, so the time t2-t1 is the time for the controller 31 to start and respond. After time t2, the controller 31 starts to output the PWM control signal Gate, and the first inductor L1 and the fifth capacitor C5 begin to charge. At this stage, the laser 40 has no current, and the duration of this stage is proportional to the storage capacity of the first inductor L1 and the fifth capacitor C5. Starting from time t3, the power supply current of the laser 40 gradually increases until it reaches the reference current value at t4. Since the third switch tube V3 is disconnected when the PWM signal is at a low level, the first inductor L1 and the fifth capacitor C5 cannot be charged and can only be charged when the PWM signal is at a high level. Therefore, it takes multiple cycles for the power supply current of the laser 40 to reach the reference current value, which makes t4-t3 relatively long.

[0089] FIG8 is a timing diagram of the control signals provided in an embodiment of the present disclosure. As shown in FIG8 , starting from time t2, the controller 31 outputs the first control signal Gate1 of a constant level, so that the second switch tube V2 can be continuously closed, thereby continuously charging the first inductor L1 and the fifth capacitor C5. Therefore, the time t5-t2 for fully charging the first inductor L1 and the fifth capacitor C5 in this embodiment is shorter than t3-t2 in the related art. In addition, the power supply current at both ends of the laser 40 will also increase faster, so the time t6-t5 is shorter than the time t4-t3. Therefore, this embodiment can improve the startup speed of the laser control circuit 30.

[0090] In some examples, as shown in FIG9 , the laser projection device further includes a frequency adjustment circuit 70. The frequency adjustment circuit 70 is connected to the controller 31. The frequency adjustment circuit 70 is configured to control the controller 31 to output a control signal of a first frequency when the image enable signal is converted from an invalid level to a valid level and the power supply signal does not reach the reference power supply value corresponding to the brightness control signal, and to control the controller 31 to output a control signal of a second frequency when the image enable signal is at a valid level and the power supply signal reaches the reference power supply value corresponding to the brightness control signal. The first frequency is less than the second frequency, the control signal of the first frequency includes the first control signal, and the control signal of the second frequency is the second control signal. The frequency adjustment circuit 70 can also be referred to as a frequency adjustment module.

[0091] In some examples, the controller 31 is a processor with computing and processing capabilities, such as a microcontroller unit (MCU) or other processing chip. The controller 31 has multiple input pins and output pins. A preset control program is written in the controller 31. The controller 31 receives the dimming drive signal and the sampled power supply current of the laser 40. Under the control of the control program, the controller 31 generates a control signal Gate based on the power supply current and the dimming drive signal.

[0092] In the disclosed embodiment, the frequency adjustment circuit 70 is used to control the frequency of the control signal Gate output by the controller 31, whereas the control signal Gate in the related art is a fixed frequency. In the disclosed embodiment, the frequency adjustment circuit 70 controls the controller 31 to output a control signal of a first frequency when the image enable signal EN changes from an inactive level to an active level, i.e., at startup, until the supply current of the laser 40 reaches a reference current value. Thereafter, a control signal of a second frequency is output. The first frequency is lower than the second frequency. As long as the first frequency is set sufficiently low, the control signal of the first frequency can be maintained at a constant level until the supply current of the laser 40 reaches the reference current value. This constant level serves as the first control signal.

[0093] For example, if the first frequency is 50 Hz and the second frequency is 500 kHz, the first-frequency control signal maintains a constant level for 0.02 seconds, which is much longer than the time it takes for the power supply current of the laser 40 to reach the reference current value. Therefore, the first-frequency control signal maintains a constant level for 0.02 seconds and can be considered the first control signal.

[0094] In some examples, as shown in FIG10 , the display control circuit 20 is further connected to the frequency adjustment circuit 70. The display control circuit 20 is configured to output a first frequency adjustment signal when the image enable signal EN is converted from an invalid level to a valid level and the power supply signal has not reached the reference power supply value corresponding to the brightness control signal, and to output a second frequency adjustment signal when the image enable signal is at a valid level and the power supply signal has reached the reference power supply value corresponding to the brightness control signal. The frequency adjustment circuit 70 is configured to control the controller 31 to output a control signal of a first frequency when receiving the first frequency adjustment signal. And to control the controller 31 to output a control signal of a second frequency when receiving the second frequency adjustment signal. That is, the display control circuit 20 instructs the frequency adjustment circuit 70 to adjust the frequency of the control signal output by the controller 31 by sending a frequency adjustment signal to the frequency adjustment circuit 70. The frequency adjustment signal can also be referred to as a frequency indication signal.

[0095] In this embodiment, the display control circuit 20 detects the status of the laser control circuit 30 through the image enable signal EN and the supply current of the laser 40. When the laser control circuit 30 is activated, it outputs a first frequency adjustment signal, and after activation, it outputs a second frequency adjustment signal. The frequency adjustment circuit 70 controls the controller 31 to output control signals of different frequencies based on different frequency adjustment signals.

[0096] The display control circuit 20 may obtain the power supply current of the laser 40 in a variety of ways. For example, the controller 31 may send the power supply current of the laser 40 collected through the eighth resistor R8 to the display control circuit 20, so that the display control circuit 20 obtains the power supply current of the laser 40. The display control circuit 20 may also directly collect the voltage across the eighth resistor R8 to obtain the power supply current of the laser 40.

[0097] In some examples, as shown in FIG11 , the frequency adjustment circuit 70 includes an external resistor circuit 71. The external resistor circuit 71 is connected to the display control circuit 20 and the frequency setting pin of the controller 31. The external resistor circuit 71 is configured to adjust the resistance of the external resistor circuit 71 to a first resistance value upon receiving a first frequency adjustment signal, and to adjust the resistance of the external resistor circuit 71 to a second resistance value upon receiving a second frequency adjustment signal. The controller 31 is configured to generate a control signal for a first frequency based on the first resistance value of the external resistor circuit 71, and to generate a control signal for a second frequency based on the second resistance value of the external resistor circuit 71. The external resistor circuit 71 may also be referred to as an external resistor module.

[0098] In the disclosed embodiment, the external resistor circuit 71 is connected between the display control circuit 20 and the frequency setting pin Fset of the controller 31. The Fset pin of the controller 31 is the external oscillation frequency timing resistor pin of the controller 31. The frequency of the control signal is usually set by the resistance of the external resistor connected to the Fset pin. The calculation formula of the frequency f of the control signal can be: f=1 / Rset*CT, where Rset is the resistance of the external resistor of the Fset pin of the controller 31, and CT is the capacitance of the internal capacitor of the controller 31. In the related art, Rset is a constant, and thus the frequency of the control signal is a constant. In this embodiment, the external resistor circuit 71 is connected to the Rset pin. Since the resistance of the external resistor circuit 71 changes based on the frequency adjustment signal Ft, the frequency of the drive signal also changes with the resistance of the external resistor circuit 71 during operation, so that the controller 31 can output control signals of different frequencies.

[0099] Continuing with Figure 11 , the external resistor circuit 71 includes a first switching transistor V1, a first resistor R1, and a second resistor R2. One end of the first switching transistor V1 is connected to the frequency setting pin of the controller 31, the other end of the first switching transistor V1 is connected to one end of the first resistor R1, and the control end of the first switching transistor V1 is connected to the display control circuit 20. The other end of the first resistor R1 is grounded. One end of the second resistor R2 is connected to one end of the first switching transistor V1 and the frequency setting pin of the controller 31, and the other end of the second resistor R2 is connected to the other end of the first resistor R1 and to ground.

[0100] The first switching transistor V1 is a P-type or N-type field-effect transistor, or a transistor, which is not limited in this embodiment. Taking a P-type transistor as an example, during operation, the control terminal of the first switching transistor V1 receives a frequency adjustment signal Ft, where the first frequency adjustment signal and the second frequency adjustment signal are level signals with different amplitudes. Based on the different levels, the transistor is controlled to operate in different operating regions, thereby controlling the impedance of the transistor. For example, when the transistor operates in the saturation region, the transistor's impedance is minimum. When the transistor operates in the amplification region, the transistor's impedance increases as the amplitude of the level decreases. When the transistor is disconnected, the impedance is maximum. The first resistor R1 is connected in series with the first switching transistor V1, so the resistance of the circuit containing the first resistor R1 and the first switching transistor V1 also changes accordingly. The first resistor R1 also prevents short circuits when the first switching transistor V1 operates in the saturation region. The second resistor R2 is connected in parallel with the first switching transistor V1. When the impedance of the first switching transistor V1 decreases, the resistance of the external resistor circuit 71 also decreases accordingly. Therefore, the external resistor circuit 71 can control the change of its own resistance based on the frequency adjustment signal Ft.

[0101] In addition to causing the controller 31 to output the first and second control signals based on the resistance change of the external resistor circuit 71, in other examples, when outputting the first control signal, the controller 31 shields the resistance signal of the external resistor circuit 71 and outputs the first control signal based on internal logic. In this case, the external resistor circuit 71 can have a fixed resistance.

[0102] It should be noted that, as shown in Figures 7 and 8, the laser control circuit 30 is in a standby state when receiving an image enable signal at an inactive level. Therefore, when starting up, the controller 31 requires a period of time to respond. To further improve the startup speed of the laser control circuit 30, in some examples, the controller 31 is further configured to enter the standby state when the first duration of the image enable signal being inactive exceeds a predetermined duration; otherwise, the controller 31 does not enter the standby state. The predetermined duration is no less than the period of the image enable signal.

[0103] As can be seen from the above embodiment, the image enable signal is a PWM signal whose cycle is the operating cycle of the laser 40. Each cycle of the image enable signal includes an inactive level and an active level. Taking a laser projection device including three lasers 40 as an example, the red laser 42 is illuminated when R-EN is at an active level; when R-EN is at an inactive level, it is off, and one of the other two lasers 40 is illuminated. This achieves the sequential illumination of the three lasers 40 within each cycle. It can be understood that when R-EN is at an inactive level, there are two possible situations. One is that G-EN or B-EN is at an active level. In this case, the current inactive level is the level within the normal cycle of the image enable signal. The other is that both G-EN and B-EN are at an inactive level, indicating that the laser projection device is not operating and all lasers 40 are off. In this embodiment, a predetermined duration exceeding the cycle of the image enable signal is set. When the first duration of the image enable signal being at an inactive level exceeds the predetermined duration, it indicates that the laser projection device is not operating, and the controller 31 enters a standby state. When the first time duration does not exceed the predetermined time duration, the current invalid level is considered to be the level within the normal cycle of the image enable signal. In this scenario, the controller 31 does not enter the standby state. In this way, when each laser 40 is started in turn within the cycle, it does not need to be restarted, thereby further improving the startup speed of the laser control circuit 30.

[0104] In some examples, as shown in FIG12 , the laser projection device may further include a timing circuit 90. The timing circuit 90 is connected to the controller 31 and the display control circuit 20. The timing circuit 90 is configured to record the first duration and send a standby signal to the controller 31 when the first duration exceeds a predetermined duration. The controller 31 is configured to enter the standby state upon receiving the standby signal; otherwise, it does not enter the standby state.

[0105] The timing circuit 90 may also be referred to as a timing module. The timing circuit 90 is a processor with a timing function. The timing circuit 90 may be integrated into the display control circuit 20 or the controller 31, or may be connected to the controller 31 and the display control circuit 20 as an independent unit. When the first duration exceeds a predetermined duration, the timing circuit 90 may send a standby signal to the controller 31, causing the controller 31 to enter a standby state based on the standby signal.

[0106] The following is an exemplary introduction to the startup process of the laser control circuit 30. The laser projection device includes three lasers 40, with an inactive level being low and an active level being high. The display control circuit 20 sends an image enable signal EN and a brightness control signal ADIM to the laser control circuits 30 corresponding to each of the three lasers 40. The image enable signal for the laser control circuit 30 corresponding to the red laser 42 is R-EN, the image enable signal for the laser control circuit 30 corresponding to the green laser 43 is G-EN, and the image enable signal for the laser control circuit 30 corresponding to the blue laser 41 is B-EN.

[0107] FIG13 is another timing diagram of various control signals provided by an embodiment of the present disclosure. As shown in FIG13 , before time t1, B-EN is high, blue laser 41 is illuminated, G-EN and R-EN are low, and green laser 43 and red laser 42 are inoperative. At time t1, R-EN transitions from low to high, B-EN and G-EN are low, and the display control circuit 20 outputs a first frequency adjustment signal to the external resistor circuit 71 corresponding to the red laser 42. The resistance of the external resistor circuit 71 corresponding to the red laser 42 increases, and the controller 31 corresponding to the red laser 42 outputs a low-frequency first control signal. The low-frequency first control signal includes a first control signal of a constant level. The controller 31 in the laser control circuit 30 corresponding to the red laser 42 is not in standby mode before time t1 and can be directly started after power-up. Therefore, no startup time for the controller 31 is currently required. During the period t7-t1, the capacitor and inductor in the driver circuit 32 corresponding to the red laser 42 are rapidly charged based on the constant-level first control signal Gate1. Starting at time t7, the supply current flowing through the red laser 42 gradually increases. The current reference current value corresponding to the brightness control signal ADIM is 3A. During the period t8-t7, the supply current of the red laser 42 increases from 0 to 3A. At time t8, the laser control circuit 30 corresponding to the red laser 42 is completely started. The display control circuit 20 outputs a second frequency adjustment signal, reducing the resistance of the external resistor circuit 71. The controller 31 corresponding to the red laser 42 outputs a high-frequency second control signal. The laser control circuit 30 adjusts the output supply voltage based on the duty cycle of the high-frequency second control signal Gate2, thereby controlling the brightness of the red laser 42.

[0108] Then, at time t9, R-EN goes low and G-EN goes high, gradually turning off the red laser 42 and lighting up the green laser 43. The timing circuit 90 records the duration that R-EN remains low. If the duration of the low level reaches a predetermined time, indicating that the laser projection device is not currently operating, the controller 31 is controlled to enter a standby state until the laser projection device resumes operation.

[0109] In addition, in the related art, after the laser 40 is lit, the controller 31 of the laser control circuit 30 outputs a control signal of a fixed frequency (i.e., the control signal of the second frequency mentioned above) to drive the opening and closing of the switch tube, and controls the on-off time of the switch tube by the duty cycle of the control signal, thereby controlling the size of the power supply voltage to the laser 40.

[0110] However, the high-frequency switching of the switch tube may cause the laser control circuit 30 to generate a strong electromagnetic interference (EMI), thereby affecting the normal power supply of the laser control circuit 30 to the laser 40 .

[0111] To improve the above technical problems, in some examples, as shown in FIG14 , the laser projection device includes a frequency adjustment circuit 70 connected to the controller 31 . The frequency adjustment circuit 70 is used to adjust the frequency of the second control signal output by the controller 31 .

[0112] The frequency of the second control signal output by the controller 31 can be understood as the operating frequency of the controller 31 .

[0113] In the disclosed embodiment, the display control circuit 20 outputs a dimming drive signal to the controller 31 based on the video signal. The dimming drive signal may be a pulse width modulation (PWM) signal. The controller 31 controls the drive circuit 32 to output a corresponding initial supply current based on the dimming drive signal to control the brightness of the laser 40. Under the action of the frequency adjustment circuit 70, the controller 31 can operate at different operating frequencies, thereby dispersing the electromagnetic radiation that is concentrated when operating at a fixed operating frequency, thereby reducing electromagnetic interference when the laser control circuit 30 is powered.

[0114] During actual operation, the frequency adjustment circuit 70 can periodically control the controller 31 to drive the driving circuit 32 to operate at different operating frequencies.

[0115] In some examples, as shown in FIG15 , the display control circuit 20 is further connected to a frequency adjustment circuit 70 . The display control circuit 20 is configured to output a frequency adjustment signal to the frequency adjustment circuit 70 . The frequency adjustment circuit 70 is configured to adjust the frequency of the second control signal output by the controller 31 based on the frequency adjustment signal. In other words, the display control circuit 20 instructs the frequency adjustment circuit 70 to adjust the frequency of the control signal output by the controller 31 by sending the frequency adjustment signal to the frequency adjustment circuit 70 . The frequency adjustment signal may also be referred to as a frequency indication signal.

[0116] The display control circuit 20 may have a clock function, set a periodically changing frequency adjustment signal based on the clock function, and output the frequency adjustment signal to the frequency adjustment circuit 70. The frequency adjustment circuit 70 causes the controller 31 to output a second control signal of a different frequency based on the frequency adjustment signal.

[0117] In some examples, as shown in Figure 16, the frequency adjustment circuit 70 includes an external resistance circuit 71, which is connected to the display control circuit 20 and the frequency setting pin of the controller 31. The external resistance circuit 71 is used to adjust the resistance of the external resistance circuit 71 according to the frequency adjustment signal to adjust the frequency of the second control signal output by the controller 31.

[0118] In the laser projection device provided in this embodiment, the external resistor circuit 71 is connected between the display control circuit 20 and the frequency setting pin Fset of the controller 31. The Fset pin of the controller 31 is the external oscillation frequency timing resistor pin of the controller 31. The frequency of the control signal is usually set by the resistance of the external resistor connected to the Fset pin. The calculation formula of the frequency f of the control signal can be: f = 1 / Rset*CT, where Rset is the resistance of the external resistor of the Fset pin of the controller 31, and CT is the capacitance of the internal capacitor of the controller 31. In the related art, Rset is a constant value, so the frequency of the control signal is a constant value. In this embodiment, the external resistor circuit 71 is connected to the Rset pin. Since the resistance of the external resistor circuit 71 changes based on the frequency adjustment signal, the frequency of the second control signal also changes with the resistance of the external resistor circuit 71 during operation, thereby achieving the frequency change of the second control signal.

[0119] In some examples, as shown in Figure 17, the external resistance circuit 71 includes a first switch V1, a first resistor R1, and a second resistor R2. The specific structure of the external resistance circuit 71 can be found in the above content and will not be repeated here.

[0120] In some examples, the frequency of the second control signal output by the controller 31 includes at least a first operating frequency and a second operating frequency. The first operating frequency is the frequency of the second control signal output by the controller 31 when the first switch V1 is off. The second operating frequency is the frequency of the second control signal output by the controller 31 when the first switch V1 is on.

[0121] For example, during the power supply process of the laser control circuit 30, the controller 31 first controls the driving circuit 32 to operate at a first operating frequency. After a first duration, the frequency adjustment circuit 70 controls the controller 31 to operate at a second operating frequency. After a second duration, the frequency adjustment circuit 70 continues to control the driving circuit 32 to operate at the first operating frequency. In this way, the frequency adjustment circuit 70 periodically and repeatedly controls the controller 31 to operate at the first operating frequency and the second operating frequency.

[0122] The interval between two consecutive times when the controller 31 controls the driving current 32 to operate at the first operating frequency is the period of operation of the controller 31 at the first operating frequency. The interval between two consecutive times when the controller 31 controls the driving circuit 32 to operate at the second operating frequency is the period of operation of the controller 31 at the second operating frequency.

[0123] In some examples, the period during which the controller 31 operates at the first operating frequency is no greater than the period during which the controller 31 operates at the second operating frequency. That is, during the process of powering the driver circuit 32, the controller 31 controls the driver circuit 32 to operate at the first operating frequency for most of the time. In comparison, the period during which the driver circuit 32 operates at the second operating frequency is relatively short. This can reduce the negative impact of power supply caused by changes in operating frequency. For example, when the driver circuit 32 operates at the second operating frequency, ripple may be generated, thereby affecting normal power supply. By setting the operating time of the driver circuit 32 at the second operating frequency to be shorter, the generation of ripple can be reduced.

[0124] In some examples, the difference between the second operating frequency and the first operating frequency is within a first range. The difference between the upper limit and the lower limit of the first range is less than the first operating frequency. This can reduce power supply fluctuations in the laser control circuit 30, thereby maintaining power supply stability.

[0125] For example, the first operating frequency is 500 kHz and the second operating frequency is 520 kHz, and the difference between the two is 20 kHz, which is within the first range of -30 kHz to +30 kHz. The difference between the upper limit and the lower limit (60 kHz) is much smaller than 500 kHz.

[0126] In practical applications, the second operating frequency can be a single frequency, that is, the controller 31 drives the driving circuit 32 based on two frequency points. The second operating frequency can also include multiple second sub-operating frequencies. The controller 31 controls the driving circuit 32 based on the multiple second sub-operating frequencies and the first operating frequency. In other words, the electromagnetic interference generated by the first operating frequency is dispersed through multiple frequency points. Therefore, the multiple second sub-operating frequencies can improve the effect of reducing radiated interference. The multiple second sub-operating frequencies can be continuous operating frequencies or discontinuous operating frequencies.

[0127] For multiple consecutive second sub-operating frequencies, it can be understood that the second operating frequency varies within a predetermined range. For example, the variation range is 480 kHz to 520 kHz. In combination with the above example, after the frequency adjustment circuit 70 enters the frequency modulation mode, the controller 31 controls the driving circuit 32 to operate at the second operating frequency that continuously varies from 480 kHz to 520 kHz.

[0128] For a plurality of discontinuous second sub-operating frequencies, the controller 31 controls the driving circuit 32 to operate at the plurality of second sub-operating frequencies respectively.

[0129] The magnitude relationship between the plurality of second sub-operating frequencies and the first operating frequency is not limited in the embodiments of the present disclosure.

[0130] For example, the plurality of second sub-operating frequencies are greater than the first operating frequency. In other words, this example reduces electromagnetic interference by using a plurality of sub-frequencies greater than the first operating frequency.

[0131] For another example, the plurality of second sub-operating frequencies are lower than the first operating frequency, that is, the electromagnetic interference is reduced by using the plurality of sub-frequencies lower than the first operating frequency.

[0132] For another example, the plurality of second sub-operating frequencies include a minimum second sub-operating frequency and a maximum second sub-operating frequency, and the first operating frequency is greater than the minimum second sub-operating frequency and less than the maximum second sub-operating frequency.

[0133] In addition, in the related art, the laser control circuit 30 is configured with components such as a switch tube, a capacitor, and an inductor. The output voltage is controlled by turning off the switch tube, thereby controlling the supply current of the laser 40. However, the high-frequency turn-off of the switch tube will cause ripples in the initial supply current. Figure 18 is a waveform diagram of the supply current in an example. As shown in Figure 18, the initial supply current will generate harmonics based on the reference current, that is, ripples, that is, the supply current I 供 Equal to the reference current I 预 With the ripple signal I 纹 The size of the ripple is affected by many factors. In a three-color laser TV, the red, green, and blue lasers correspond to a laser control circuit 30 respectively. When working, these three lasers are lit in turn. When the laser 40 switches, if the rising or falling speed of the working current of the laser 40 is too slow, resulting in a long travel time, a scene in which lasers 40 of different colors are lit at the same time will appear, which will affect the quality of the picture. The rise and fall time of the working current is proportional to the inductance. For this reason, in some example laser TVs, the rise or fall time of the working current is reduced by reducing the inductance. However, the inductance L is proportional to the ripple current I 纹 , with the following relationship.

[0134] In other words, reducing the inductance and capacitance will increase the current ripple. Excessive ripple will reduce the power supply efficiency of the laser control circuit 30 and may even cause surge voltage or current, leading to the burning of the laser 40. Therefore, reducing the ripple in the power supply current of the laser 40 is important.

[0135] In addition, since the embodiment of the present disclosure uses the frequency adjustment circuit 70 to enable the controller 31 to operate at different operating frequencies. However, as the adjustment range of the operating frequency increases, especially when the operating frequency is low, the initial supply current of the laser control circuit 30 will produce greater ripple. Conversely, the further increase in ripple also limits the adjustment range of the operating frequency. For this reason, the embodiment of the present disclosure is equipped with a current adjustment circuit 80 to reduce the ripple in the initial supply current caused by the spread spectrum of the operating frequency. Among them, the current adjustment circuit 80 can also be referred to as a current adjustment module.

[0136] Next, a solution for reducing ripples using the current regulating circuit 80 will be described as an example.

[0137] As shown in Figures 14 to 17, the current adjustment circuit 80 provided in the embodiment of the present disclosure is connected to the driving circuit 32 and the laser 40. The current adjustment circuit 80 is used to adjust the current flowing through the laser 40 based on the comparison result between the initial power supply current and the reference current, so that the absolute value of the difference between the current flowing through the laser 40 and the reference current is smaller than the absolute value of the difference between the initial power supply current and the reference current.

[0138] The reference current is the current that enables the laser 40 to achieve the brightness corresponding to the dimming drive signal. It can be understood that the dimming drive signal corresponds to the reference current, which is the ideal current under the current dimming drive signal and the theoretical output value of the initial supply current. The initial supply current is compared with the reference current. When the initial supply current is greater than the reference current, it indicates that the initial supply current has a ripple current greater than zero. In this scenario, the current adjustment circuit 80 adjusts the current flowing through the laser 40 so that the current flowing through the laser 40 is less than the initial supply current, which is equivalent to reducing the ripple current in the current flowing through the laser 40. Conversely, when the initial supply current is less than the reference current, it indicates that the initial supply current has a ripple current less than zero. The current adjustment circuit 80 adjusts the current flowing through the laser 40 so that the current flowing through the laser 40 is greater than the initial supply current, which is equivalent to compensating for the ripple current less than zero in the initial supply current. This reduces the ripple in the current flowing through the laser 40.

[0139] It should be noted that, based on Ohm's law, when the load is constant, the voltage is proportional to the current. That is, when the ripple current in the current flowing through the laser 40 is reduced, the ripple voltage in the power supply voltage of the laser 40 is also reduced.

[0140] Next, the current regulating circuit 80 is exemplarily introduced.

[0141] In some examples, as shown in FIG19 , one end of the current adjustment circuit 80 is connected to the output end of the laser control circuit 30 and the input end of the laser 40, and the other end of the current adjustment circuit 80 is connected to the output end of the laser 40. The current adjustment circuit 80 is configured to control the current flowing through the laser 40 to be less than the initial supply current when the initial supply current is greater than the reference current.

[0142] The current adjustment circuit 80 is connected in parallel with the laser 40. The current flowing through the laser 40 is the difference between the initial supply current and the current flowing through the current adjustment circuit 80. When the initial supply current is less than the reference current, the current flowing through the laser 40 can be reduced by adjusting the current flowing through the current adjustment circuit 80, which is considered to be shunting the initial supply current. After the shunting process is performed, the current flowing through the laser 40 is less than the initial supply current, thereby reducing the ripple in the current flowing through the laser 40. Of course, when the initial supply current is not greater than the reference current, the shunting process is not performed.

[0143] As shown in Figure 20, the initial supply current I 供 is the reference current I 基 With the ripple signal I 纹 The sum of I 供 =I 基 +I 纹 , reference current I 基 It can be considered as the DC current in the initial power supply current, the reference current I 基 It is set based on the current dimming drive signal. 供 >I 基 When the current is divided, the current I flowing through the laser 40 is obtained. 激 =I 供 -I 分 , where I 分 No more than I 纹 , in Figure 20, I 分 =I 纹 As can be seen, based on this example, the ripple of the initial power supply current for supplying power to the laser 40 can be reduced.

[0144] In other examples, as shown in FIG21 , one end of the current regulating circuit 80 is connected to the output end of the power supply board 002 and the input end of the laser control circuit 30, and the other end of the current regulating circuit 80 is connected to the output end of the laser control circuit 30 and the input end of the laser 40. The current regulating circuit 80 is configured to control the current flowing through the laser 40 to be greater than the initial supply current when the initial supply current is less than the reference current.

[0145] The current adjustment circuit 80 is connected in parallel with the laser control circuit 30. The current flowing through the laser 40 is the sum of the current flowing through the current adjustment circuit 80 and the initial supply current. When the initial supply current is greater than the reference current, the current flowing through the current adjustment circuit 80 can be adjusted to increase the current flowing through the laser 40, which is considered to be compensating for the initial supply current. After the compensation process is performed, the current flowing through the laser 40 is greater than the initial supply current, thereby reducing the ripple in the current flowing through the laser 40. If the initial supply current is not less than the reference current, the compensation process is not performed.

[0146] As shown in Figure 22, the initial supply current I 供 is the reference current I 基 With the ripple signal I 纹 The sum of I 供 =I 基 +I 纹 , reference current I 基 It can be considered as the DC current in the initial power supply current, the reference current I 预 It is set based on the current dimming drive signal. 供 基 When the compensation process is performed, the current I flowing through the laser 40 is obtained. 激 =I 供 +I 补 , where I 补 Not greater than -I 纹 , in FIG22, I 补 =-I 纹 As can be seen, based on this example, the ripple of the initial power supply current for supplying power to the laser 40 can be reduced.

[0147] In other examples, the two aforementioned embodiments may be combined, i.e., two current adjustment circuits 80 may be provided in the laser control circuit 30, wherein the first current adjustment circuit 80 is connected in parallel with the laser 40, and the second current adjustment circuit 80 is connected in parallel with the laser control circuit 30. When the initial supply current is greater than the reference current, the first current adjustment circuit 80 performs a current shunting process to control the current flowing through the laser 40 to be less than the initial supply current; when the initial supply current is less than the reference current, the second current adjustment circuit 80 performs a compensation process to control the current flowing through the laser 40 to be greater than the initial supply current.​

[0148] The current regulating circuit 80 in the above-mentioned embodiment of performing the current shunting process and the compensation process will be described below as examples.

[0149] First, an example description will be given of the current adjustment circuit 80 that performs the current dividing process.

[0150] As shown in Figure 23, the current regulation circuit 80 includes a first control subcircuit 82 and a first current control subcircuit 81. The first control subcircuit 82 is connected to the input terminal of the laser 40. The first control subcircuit 82 is configured to output a first current adjustment signal in a first state when the initial supply current at the input terminal of the laser 40 is greater than a reference current, and to output a first current adjustment signal in a second state when the initial supply current is not greater than the reference current. The first current control subcircuit 81 includes a second switch V2. One end of the second switch V2 is connected to the output terminal of the laser control circuit 30 and the input terminal of the laser 40, the other end of the second switch V2 is connected to the output terminal of the laser 40, and the control end of the second switch V2 is connected to the first control subcircuit 82. The first current control subcircuit 81 is configured to control the current flowing through the second switch V2 based on the first current adjustment signal in the first state, and to disconnect the second switch V2 based on the first current adjustment signal in the second state.

[0151] The first control subcircuit can also be referred to as the first control subunit, and the first current control subcircuit can also be referred to as the first current control subunit. The second switch transistor V2 is a transistor with both shutoff and amplification functions, specifically a P-type or N-type MOS transistor, or a triode. For example, if the second switch transistor V2 is a MOS transistor, the control terminal of the second switch transistor V2 corresponds to the gate of the MOS transistor.

[0152] During operation, the first control subcircuit 82 outputs a first current adjustment signal in a first state when the initial supply current at the input of the laser 40 is greater than the reference current. The first current adjustment signal in the first state is a signal capable of turning on the second switch V2, and the first current adjustment signal in the first state varies with the initial supply current, thereby controlling the current flowing through the second switch V2. When the initial supply current is not greater than the reference current, the first control subcircuit 82 outputs the first current adjustment signal in a second state. The first current adjustment signal in the second state is lower than the turn-on voltage of the second switch V2, causing the second switch V2 to turn off, and the current adjustment circuit 80 does not share the current.

[0153] In some examples, as shown in FIG24 , the first current control sub-circuit 81 includes a third resistor R3 . One end of the third resistor R3 is connected to one end of the second switch V2 , and the other end of the third resistor R3 is connected to the output end of the laser 40 .

[0154] The third resistor R3 is a voltage divider resistor that can prevent the working circuit of the second switch tube V2 from short-circuiting when the second switch tube V2 is working in a saturated state. In addition, the shunt current I of the current adjustment circuit 80 can be set by the resistance value of the third resistor R3. 分 with I 纹 The relationship will be explained in detail in the subsequent examples.

[0155] In one example, as shown in FIG25 , the first control subcircuit 82 includes a first filter subcircuit 83 and a first operational amplifier OP1. The input of the first filter subcircuit 83 is connected to the input of the laser 40. The first filter subcircuit 83 is used to filter out the reference voltage corresponding to the DC reference current from the supply voltage at the input of the laser 40. The non-inverting input of the first operational amplifier OP1 is connected to the output of the first filter subcircuit 83, the inverting input of the first operational amplifier OP1 is connected to one end of the third resistor R3, and the output of the first operational amplifier OP1 is connected to the control terminal of the second switch V2. The first filter subcircuit can also be referred to as a first filter subunit.

[0156] It should be noted that, based on Ohm's law, under a constant load, current and voltage are proportional. It can be understood that the reference voltage corresponding to the reference current under the current dimming drive signal is the ideal voltage at the input of the laser 40. The initial supply current is generated based on the voltage at the output of the drive circuit 32 (i.e., the input of the laser). When the initial supply current is greater than the reference current, the supply voltage at the input of the laser 40 (hereinafter referred to as the supply voltage) is also greater than the reference voltage. Therefore, the relationship between the initial supply current and the reference current can be determined by determining the relationship between the supply voltage and the reference voltage.

[0157] The first filtering sub-circuit 83 is a filter. Specifically, the first filtering sub-circuit 83 is an active filter or a passive filter, a low-order filter or a high-order filter, which is not limited in this example.

[0158] The following is an illustrative description of this example in combination with actual scenarios. The first filter sub-circuit 83 outputs an AC ripple voltage U 纹 =U 供 -U 基 , it can be understood that the initial supply current I 供 Corresponding supply voltage U 供 Greater than the reference current I 基 Corresponding reference voltage U 基 When the ripple voltage U 纹 Greater than zero; otherwise the ripple voltage U 纹 Not greater than zero.

[0159] 25 , the non-inverting input terminal of the first operational amplifier OP1 receives the AC ripple voltage U 纹 The inverting input terminal of the first operational amplifier OP1 is connected to the other end of the second switch tube V2. Based on the virtual short principle of the operational amplifier, the voltage of the non-inverting input terminal and the reverse input terminal of the first operational amplifier OP1 are equal. Therefore, the voltage U3 of the non-inverting input terminal is equal to the voltage U3 of the other end C of the second switch tube V2. C U3 changes with the ripple voltage, so that U3=U C , the first operational amplifier OP1 needs to output a first current adjustment signal of the corresponding first state based on the ripple signal to adjust the opening of the second switch tube V2, thereby controlling the current flowing through the second switch tube V2. 纹 When it is not greater than zero, it corresponds to U C is not greater than zero, U C Cannot be negative, when the ripple voltage U 纹 When the initial supply current is greater than the reference current, the first operational amplifier OP1 outputs a first current adjustment signal of the second state to control the second switch V2 to be turned off. Thus, based on this example, the current shunting process can be performed when the initial supply current is greater than the reference current, and the current shunting process is not performed when the initial supply current is less than the reference current.

[0160] In addition, based on Ohm's law, U C =I 分 (t)·R3, it can be seen that I can be set based on R3 分 (t) and I 纹 The corresponding relationship of (t) can be specifically: 分 (t) = αI 纹 (t)(0≤α≤1); I 供 =I 激 +I 分 (t); I 供 =I 基 +I 纹 (t); I 激 =I 基 +(1-α)I 纹 (t)(0≤α≤1);

[0161] The value of α can be adjusted by the resistance of the third resistor R3.

[0162] In this example, the first operational amplifier OP1, the third resistor R3, and the second switching transistor V2 form a voltage-controlled current source. Specifically, the current flowing through the second switching transistor V2 is controlled based on the voltage at the non-inverting input terminal of the first operational amplifier OP1. The voltage at the non-inverting input terminal of the first operational amplifier OP1 is generated based on the ripple voltage output by the first filtering sub-circuit 83. Therefore, the current in the second switching transistor V2 can be controlled based on the ripple voltage. Furthermore, the ripple reduction ratio can be adjusted by setting the resistance value of the third resistor R3.

[0163] In some examples, as shown in FIG26 , the first filter subcircuit 83 further includes a first capacitor C1, a second capacitor C2, a second operational amplifier OP2, a fourth resistor R4, and a fifth resistor R5. One end of the first capacitor C1 is connected to the input terminal of the laser 40, and the other end of the first capacitor C1 is connected to one end of the second capacitor C2. The other end of the second capacitor C2 is connected to the non-inverting input terminal of the second operational amplifier OP2. The inverting input terminal of the second operational amplifier OP2 is connected to the output terminal of the second operational amplifier OP2, and the output terminal of the second operational amplifier OP2 is connected to the non-inverting input terminal of the first operational amplifier OP1. One end of the fourth resistor R4 is connected to the other end of the first capacitor C1 and one end of the second capacitor C2, and the other end of the fourth resistor R4 is connected to the output terminal of the second operational amplifier OP2. One end of the fifth resistor R5 is connected to the other end of the second capacitor C2, and the other end of the fifth resistor R5 is grounded.

[0164] The first filtering subcircuit 83 is an active second-order high-pass filter. The first capacitor C1 and the fourth resistor R4 form a first-order RC filter, while the second capacitor C2 and the fifth resistor R5 form a second-order RC filter. The RC filter utilizes the characteristic of capacitors that pass AC but block DC to filter out the DC voltage (reference voltage) from the supply voltage, resulting in an AC ripple voltage. This two-order RC filter can enhance the filtering effect of the first filtering subcircuit 83. In this embodiment, a second operational amplifier OP2 is also provided, which makes the first control subcircuit 82 an active filter, thereby further enhancing the filtering effect.

[0165] Continuing with FIG26 , based on the above embodiment, the first filtering sub-circuit 83 further includes a third capacitor C3. One end of the third capacitor C3 is connected to the output terminal of the second operational amplifier OP2, and the other end of the third capacitor C3 is connected to the non-inverting input terminal of the first operational amplifier OP1. The third capacitor C3 is used to further filter out the DC voltage in the ripple voltage, thereby improving the filtering effect of the first filtering sub-circuit 83.

[0166] In some examples, as shown in FIG27 , the first control subcircuit 82 further includes a third operational amplifier OP3, a sixth resistor R6, and a seventh resistor R7. The non-inverting input of the third operational amplifier OP3 is connected to the output of the second operational amplifier OP2, the inverting input of the third operational amplifier OP3 is connected to one end of the sixth resistor R6, and the output of the third operational amplifier OP3 is connected to the non-inverting input of the first operational amplifier OP1. The other end of the sixth resistor R6 is grounded. One end of the seventh resistor R7 is connected to the output of the third operational amplifier OP3, and the other end of the seventh resistor R7 is connected to the inverting input of the third operational amplifier OP3 and one end of the sixth resistor R6.

[0167] As can be seen from the above example, after filtering out the DC reference voltage from the power supply voltage Usupply, an AC ripple voltage is obtained, and the ripple voltage is relatively small. In this example, the ripple voltage is amplified, so that the first operational amplifier OP1 outputs a more accurate first current adjustment signal, thereby improving the current control accuracy of the current adjustment circuit 80.

[0168] The output voltage of the third operational amplifier OP3 is Uo=A(U P -U N ), where A is the amplification factor, U P is the voltage at the non-inverting input terminal of the third operational amplifier OP3, U N is the voltage at the inverting input terminal. From the circuit structure of this example, we can obtain A=(R6+R7) / R6.

[0169] In some examples, as shown in FIG. 28 , the first control subcircuit 82 further includes a fourth capacitor C4, one end of which is connected to the output of the third operational amplifier OP3, and the other end of which is connected to the non-inverting input of the first operational amplifier OP1. The fourth capacitor C4 is used to further filter out DC voltage from the amplified ripple voltage.

[0170] In some examples, with continued reference to FIG28 , the first control sub-circuit 82 further includes a fourth operational amplifier OP4. A non-inverting input terminal of the fourth operational amplifier OP4 is connected to an input terminal of the laser 40, an inverting input terminal of the fourth operational amplifier OP4 is connected to an output terminal of the fourth operational amplifier OP4, and an output terminal of the fourth operational amplifier OP4 is connected to an input terminal of the first filtering sub-circuit 83.

[0171] The in-phase input terminal of the fourth operational amplifier OP4 is connected to the input terminal of the laser 40 and receives the power supply voltage U 供 , the reverse input terminal is connected to the output terminal, based on the virtual short principle of the operational amplifier, the voltage of the in-phase input terminal and the reverse input terminal are equal, so the voltage of the output terminal of the fourth operational amplifier OP4 is the supply voltage U 供That is, the fourth operational amplifier OP4 is a voltage follower. The voltage follower has the characteristics of high input impedance and low output impedance, which can play the role of impedance matching in the circuit, enabling the subsequent amplifier circuit to work better.

[0172] In some examples, as shown in FIG28 , the first control subcircuit 82 further includes a voltage stabilizing diode VD2 , wherein the anode of the voltage stabilizing diode VD2 is grounded, and the cathode of the voltage stabilizing diode VD2 is connected to the non-inverting input terminal of the first operational amplifier OP1 .

[0173] The Zener diode VD2 acts as a limiter, limiting the voltage output to the first operational amplifier OP1. When the voltage at point D is less than the regulated voltage of the Zener diode VD2, this voltage is input to the first operational amplifier OP1. When the voltage at point D is greater than the regulated voltage of the Zener diode VD2, the voltage at point D is maintained at the regulated voltage, which is then input to the first operational amplifier OP1. This prevents damage to the first operational amplifier OP1 due to excessively high voltages.

[0174] In some examples, as shown in FIG28 , the first control subcircuit 82 further includes a bias current source, wherein the anode of the bias current source is connected to the cathode of the Zener diode VD2 , and the cathode of the bias current source is connected to the anode of the Zener diode VD2 and grounded.

[0175] In this example, the current flowing through the laser 40 is: I 分 (t) = I 偏置 +αI 纹 (t)(0≤α≤1); I 供 =I 基 +I 分 (t); I 激 =I 基 -I 偏置 +(1-α)I 纹 (t)(0≤α≤1);

[0176] This can further improve the shunting effect on the initial power supply current.

[0177] In some examples, as shown in FIG29 , the display control circuit 20 is further connected to the laser control circuit 30 , and the display control circuit 20 is configured to adjust the dimming drive signal based on the current flowing through the second switch tube V2 to increase the reference current.

[0178] In the above example, when the initial supply current is greater than the reference current, a current shunting process is performed, which reduces the effective current signal flowing through the laser 40, resulting in insufficient brightness of the laser 40. In this example, the display control circuit 20 is connected to the current adjustment circuit 80. Specifically, as shown in Figure 29, it can be connected to one end of the third resistor R3 to sample the current signal flowing through the second switch tube V2 and increase the corresponding dimming drive signal based on the current signal. In this way, the reference current of the laser control circuit 30 can be increased, and the DC supply voltage output by the laser control circuit 30 can be increased, thereby increasing the brightness of the laser 40.

[0179] It should be noted that in some examples, as shown in FIG30 , there are multiple lasers 40, and the laser projection device includes multiple laser control circuits 30 and multiple current adjustment circuits 80, with the multiple lasers 40, the multiple laser control circuits 30, and the multiple current adjustment circuits 80 corresponding one to one. For each laser control circuit 30, the laser control circuit 30 receives a power signal and a dimming drive signal, and is connected to the input end of the corresponding laser 40 and the input end of the corresponding current adjustment circuit 80. The output end of each laser 40 is connected to the output end of the corresponding current adjustment circuit 80 and is grounded.

[0180] The above is an exemplary description of the current regulating circuit 80 that performs the shunt process. The following is an exemplary description of the current regulating circuit 80 that performs the compensation process.

[0181] As shown in Figure 31, the current regulation circuit 80 includes a second control subcircuit 85 and a second current control subcircuit 84. The second control subcircuit 85 is connected to the input terminal of the laser 40 and is configured to output a second current adjustment signal in a first state when the initial supply current is less than the reference current, and to output a second current adjustment signal in a second state when the initial supply current is not less than the reference current. The second current control subcircuit 84 includes a fourth switch V4. One end of the fourth switch V4 is connected to the output terminal of the power supply board 002, and the other end of the fourth switch V4 is connected to the output terminal of the laser control circuit 30 and the input terminal of the laser 40. The second current control subcircuit 84 is configured to control the current flowing through the fourth switch V4 based on the second current adjustment signal in the first state, and to disconnect the fourth switch V4 based on the second current adjustment signal in the second state.

[0182] The second control subcircuit can also be referred to as a second control subunit, and the second current control subcircuit can also be referred to as a second current control subunit. The fourth switch transistor V4 is a transistor with both shutoff and amplification functions, and can be a P-type or N-type MOS transistor, or a triode. For example, if the fourth switch transistor V4 is a MOS transistor, the control terminal of the fourth switch transistor V4 corresponds to the gate of the MOS transistor.

[0183] During operation, the second control subcircuit 85 outputs a second current adjustment signal in a first state when the initial supply current at the input of the laser 40 is less than the reference current. The second current adjustment signal in the first state is a signal capable of turning on the fourth switch V4, and the second current adjustment signal in the first state varies with the initial supply current, thereby controlling the current flowing through the fourth switch V4. When the initial supply current is not less than the reference current, the second current adjustment signal in the second state is output. The second current adjustment signal in the second state is lower than the turn-on voltage of the fourth switch V4, turning off the fourth switch V4 and causing the current adjustment circuit 80 to not compensate for the current.

[0184] In some examples, as shown in FIG32 , the second current control sub-circuit 84 further includes a ninth resistor R9 . One end of the ninth resistor R9 is connected to the other end of the fourth switch V4 , and the other end of the ninth resistor R9 is connected to the input end of the laser 40 and the output end of the laser control circuit 30 .

[0185] The ninth resistor R9 is a voltage divider resistor that can prevent the fourth switch V4 from short-circuiting the working circuit where the fourth switch V4 is located when the fourth switch V4 is working in a saturated state. In addition, the compensation current I of the current adjustment circuit 80 can be set by the resistance value of the ninth resistor R9. 补 with I 纹 The relationship will be explained in detail in the subsequent examples.

[0186] In some examples, as shown in FIG33 , the second control subcircuit 85 includes a second filtering subcircuit 86, an inverting subcircuit 87, and a fifth operational amplifier OP5. The second filtering subcircuit 86 is connected to the input of the laser 40. The second filtering subcircuit 86 is configured to filter out the reference voltage corresponding to the reference current from the supply voltage at the input of the laser 40 and output the filtered supply voltage. The inverting subcircuit 87 is connected to the output of the second filtering subcircuit 86 and is configured to output the inverted filtered supply voltage. The non-inverting input of the fifth operational amplifier OP5 is connected to the output of the inverting subcircuit 87. The inverting input of the fifth operational amplifier OP5 is connected to one end of the ninth resistor R9 and the other end of the fourth switching transistor V4. The output of the fifth operational amplifier OP5 is connected to the control terminal of the fourth switching transistor V4. The second filtering subcircuit can also be referred to as a second filtering subunit, and the inverting subcircuit can also be referred to as an inverting subunit.

[0187] It should be noted that, based on Ohm's law, under a constant load, current and voltage are proportional. It can be understood that the reference voltage corresponding to the reference current under the current dimming drive signal is the ideal voltage at the input of the laser 40. The initial supply current is generated based on the actual voltage at the output of the laser control circuit 30 (i.e., the input of the laser 40). When the initial supply current is greater than the reference current, the supply voltage at the input of the laser 40 (hereinafter referred to as the supply voltage) is also greater than the reference voltage. Therefore, the relationship between the initial supply current and the reference current can be determined by determining the relationship between the supply voltage and the reference voltage.

[0188] The second filtering subcircuit 86 is a filter. Specifically, the second filtering subcircuit 86 is an active filter or a passive filter, a low-order filter or a high-order filter, which is not limited in this example.

[0189] The following is an illustrative description of this example in combination with a practical scenario: The second filtering sub-circuit 86 outputs an AC ripple voltage U 纹 =U 供 -U 基 , it can be understood that the initial supply current I 供 Corresponding supply voltage U 供 Less than the reference current I 基 Corresponding reference voltage U 基 When the ripple voltage U 纹 Less than zero; otherwise the ripple voltage U 纹 Not less than zero.

[0190] 33, the reverse sub-circuit 87 receives the AC ripple voltage U 纹 , the reverse sub-circuit 87 converts the ripple voltage U 纹 Converted to reverse ripple voltage -U 纹 The non-inverting input terminal of the fifth operational amplifier OP5 receives the reverse ripple voltage -U 纹 The inverting input terminal of the fifth operational amplifier OP5 is connected to the other end of the fourth switch tube V4. Based on the virtual short principle of the operational amplifier, the voltage of the non-inverting input terminal and the reverse input terminal of the fifth operational amplifier OP5 are equal. Therefore, the voltage U3 of the non-inverting input terminal is equal to the voltage U3 of the other end B of the fourth switch tube V4. B And U3 changes with the ripple signal, so that U3=U B , the fifth operational amplifier OP5 needs to output a corresponding second current adjustment signal based on the ripple signal to adjust the opening of the fourth switch tube V4, thereby controlling the current flowing through the fourth switch tube V4. 纹 When the reverse ripple voltage is less than zero, -U 纹is greater than zero, U3 is greater than zero, then the fifth operational amplifier OP5 outputs the second current adjustment signal of the first state so that U3 = U B ; When the ripple voltage U 纹 When the reverse ripple voltage is not less than zero, -U 纹 When the current U1 is less than zero and the current U2 is less than zero, the fifth operational amplifier OP5 outputs a second current adjustment signal of the second state that controls the fourth switch V4 to be turned off. Thus, based on this example, compensation processing is performed when the initial supply current is less than the reference current, and compensation processing is not performed when the initial supply current is not less than the reference current.

[0191] In addition, based on Ohm's law, we can get: U B =I 补 (t)·R9, it can be seen that I can be set based on R9 补 (t) and I 纹 The corresponding relationship of (t) can be specifically: 补 (t)=-αI 纹 (t)(0≤α≤1); I 激 =I 供 +I 补 (t); I 供 =I 基 +I 纹 (t); I 激 =I 基 +(1-α)I 纹 (t)(0≤α≤1);

[0192] The value of α can be adjusted by adjusting the resistance of the ninth resistor R9.

[0193] In some examples, as shown in FIG34 , the second filtering subcircuit 86 includes a sixth capacitor C6, a seventh capacitor C7, a sixth operational amplifier OP6, a tenth resistor R10, and an eleventh resistor R11. One end of the sixth capacitor C6 is connected to the input of the laser 40, the other end of the sixth capacitor C6 is connected to one end of the seventh capacitor C7, and the other end of the seventh capacitor C7 is connected to the non-inverting input of the sixth operational amplifier OP6. The inverting input of the sixth operational amplifier OP6 is connected to the output of the sixth operational amplifier OP6, and the output of the sixth operational amplifier OP6 is connected to the inverting subcircuit 87. One end of the tenth resistor R10 is connected to the other end of the sixth capacitor C6 and one end of the seventh capacitor C7, and the other end of the tenth resistor R10 is connected to the output of the sixth operational amplifier OP6. One end of the eleventh resistor R11 is connected to the other end of the seventh capacitor C7, and the other end of the eleventh resistor R11 is grounded.

[0194] The working principle of the second filtering sub-circuit 86 is the same as that of the first filtering sub-circuit 83 , and details thereof may be referred to the related contents of the first filtering sub-circuit 83 , which will not be described again here.

[0195] In some examples, as shown in FIG34 , the second filtering sub-circuit 86 further includes an eighth capacitor C8 , one end of which is connected to the output of the sixth operational amplifier OP6 , and the other end of which is connected to the non-inverting input of the fifth operational amplifier OP5 . The eighth capacitor C8 is used to further filter out DC signals from the ripple voltage signal, thereby improving the filtering effect of the second filtering sub-circuit 86 .

[0196] In some examples, as shown in FIG35 , the inverting sub-circuit 87 includes a seventh operational amplifier OP7, a twelfth resistor R12, and a thirteenth resistor R13. One end of the twelfth resistor R12 is connected to the second filtering sub-circuit 86, and the other end of the twelfth resistor R12 is connected to the inverting input of the seventh operational amplifier OP7. The non-inverting input of the seventh operational amplifier OP7 is grounded, and the output of the seventh operational amplifier OP7 is connected to the non-inverting input of the fifth operational amplifier OP5. One end of the thirteenth resistor R13 is connected to the other end of the twelfth resistor R12 and the inverting input of the seventh operational amplifier OP7, and the other end of the thirteenth resistor R13 is connected to the output of the seventh operational amplifier OP7.

[0197] The seventh operational amplifier OP7 is an inverting operational amplifier. Since no current flows through the operational amplifier, the current flowing through the twelfth resistor R12 and the thirteenth resistor R13 can be obtained as follows: I=(U 纹 -U P ) / R12=(U P -Uo) / R13

[0198] Based on the virtual short principle, U P =0, then Uo = -U 纹 R13 / R12, so based on this example, an inverted ripple signal can be output.

[0199] Furthermore, the amplification factor can be adjusted based on the twelfth resistor R12 and the thirteenth resistor R13. The amplification factor A = R13 / R12. When R13 is set greater than R12, Uo can be amplified. After filtering the DC reference current from the initial supply current, an AC ripple signal is obtained. The ripple signal is relatively small. In this example, this ripple signal is amplified, thereby causing the fifth operational amplifier OP5 to output a more accurate second current adjustment signal, thereby improving the current control accuracy of the current adjustment circuit 80.

[0200] In some examples, as shown in FIG36 , the second control subcircuit 85 further includes a ninth capacitor C9, one end of which is connected to the output of the seventh operational amplifier OP7, and the other end of which is connected to the non-inverting input of the fifth operational amplifier OP5. The ninth capacitor C9 is used to further filter out DC signals from the amplified ripple signal.

[0201] In some examples, as shown in FIG36 , the second control subcircuit 85 further includes an eighth operational amplifier OP8, the non-inverting input terminal of the eighth operational amplifier OP8 is connected to the input terminal of the laser 40, the inverting input terminal of the eighth operational amplifier OP8 is connected to the output terminal of the eighth operational amplifier OP8, and the output terminal of the eighth operational amplifier OP8 is connected to one end of the sixth capacitor C6.

[0202] The working principle of the eighth operational amplifier OP8 is similar to that of the fourth operational amplifier OP4 in the above example. For details, please refer to the relevant description of the fourth operational amplifier OP4, which will not be repeated here.

[0203] In some examples, as shown in FIG36 , the second control subcircuit 85 further includes a Zener diode VD2 and a bias current source. The anode of the Zener diode VD2 is grounded, and the cathode of the Zener diode VD2 is connected to the non-inverting input of the fifth operational amplifier OP5. The anode of the bias current source is connected to the cathode of the Zener diode VD2, and the cathode of the bias current source is connected to the anode of the Zener diode VD2 and to ground.

[0204] The working principles of the voltage stabilizing diode VD2 and the bias current source can refer to the relevant contents in the aforementioned first control subcircuit 82 and will not be elaborated here.

[0205] It should be noted that in some examples, as shown in Figure 37, there are multiple lasers 40, and the laser projection equipment includes multiple laser control circuits 30 and multiple current adjustment circuits 80, and the multiple lasers 40, multiple laser control circuits 30 and multiple current adjustment circuits 80 correspond one to one.

[0206] For each current adjustment circuit 80 , one end of the current adjustment circuit 80 is connected to the input end of the corresponding laser control circuit 30 and the output end of the power board 002 , and the other end of the current adjustment circuit 80 is connected to the output end of the corresponding laser control circuit 30 and the input end of the corresponding laser 40 .

[0207] It should be supplemented that, FIG19 , FIG21 , FIG23 - FIG24 , FIG29 and FIG31 - FIG32 may only have one of the frequency adjustment circuit 70 and the current adjustment circuit 80 .

[0208] The embodiment of the present disclosure also provides a laser control circuit 30. The laser control circuit 30 includes a controller 31 and a drive circuit 32. The controller 31 is connected to the display control circuit 20 and the drive circuit 32, and the controller 31 is used to generate a control signal based on the image enable signal and the brightness control signal. The drive circuit 32 is connected to the corresponding laser 40, and the drive circuit 32 is used to generate a power supply signal to supply power to the corresponding laser 40 based on the control signal. Among them, the control signal includes a first control signal and a second control signal. The first control signal is a constant level signal output by the controller 31 when the image enable signal is converted from an invalid level to a valid level and the power supply signal does not reach the reference power supply value corresponding to the brightness control signal. The second control signal is a PWM signal output by the controller 31 when the image enable signal is at a valid level and the power supply signal reaches the reference power supply value corresponding to the brightness control signal.

[0209] For the specific content of the laser control circuit 30 , please refer to the above content and will not be repeated here.

[0210] An embodiment of the present disclosure also provides a method for controlling a laser projection device. As shown in FIG38 , the method for controlling a laser projection device includes the following steps.

[0211] S3801: The laser 40 emits a laser beam to provide an illumination beam for the device.

[0212] S3802: The display control circuit 20 outputs a dimming drive signal and an image display drive signal, wherein the dimming drive signal includes an image enable signal and a brightness control signal.

[0213] S3803: The light modulation device 50 modulates the laser beam under the drive of the image display drive signal.

[0214] S3804: The projection lens 60 receives the modulated laser beam and projects an image.

[0215] S3805: The controller 31 generates a control signal based on the image enable signal and the brightness control signal.

[0216] S3806 : The driving circuit 32 generates a power supply signal for supplying power to the corresponding laser 40 based on the control signal.

[0217] The control signal includes a first control signal and a second control signal. The first control signal is a constant-level signal output by the controller 31 when the image enable signal transitions from an inactive level to an active level and the power supply signal does not reach the reference power supply value corresponding to the brightness control signal. The second control signal is a PWM signal output by the controller 31 when the image enable signal is at an active level and the power supply signal reaches the reference power supply value corresponding to the brightness control signal.

[0218] In some examples, S3805 includes the following steps. When the image enable signal is converted from an invalid level to a valid level and the power supply signal does not reach the reference power supply value corresponding to the brightness control signal, the frequency adjustment circuit 70 controls the controller 31 to output a control signal of a first frequency. When the image enable signal is at a valid level and the power supply signal reaches the reference power supply value corresponding to the brightness control signal, the frequency adjustment circuit 70 controls the controller 31 to output a control signal of a second frequency. The first frequency is less than the second frequency. The control signal of the first frequency includes the first control signal. The control signal of the second frequency is the second control signal.

[0219] For details about the control method of the laser projection device, please refer to the above content and will not be repeated here.

[0220] FIG39 is a schematic diagram of the hardware structure of an electronic device provided in an embodiment of the present disclosure. As shown in FIG39 , electronic device 400 includes memory 401 and processor 402. Memory 401 is used to store computer programs. Processor 402 is used to execute the computer programs stored in the memory to implement the laser driving method in the above embodiment.

[0221] In some examples, the memory 401 may be independent or integrated with the processor 402 .

[0222] When the memory 401 is a device independent of the processor 402 , the electronic device 400 further includes a bus 403 , which is used to connect the memory 401 and the processor 402 .

[0223] In some examples, the electronic device provided in this embodiment further includes a communication interface 404, which is connected to the processor 402 via the bus 403. The processor 402 controls the communication interface 404 to implement the above-mentioned receiving and sending functions of the electronic device 400.

[0224] The embodiments of the present disclosure further provide a computer-readable storage medium, which includes a computer program. The computer program is used to implement the control method in the above embodiments.

[0225] The above description is merely an exemplary embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the principles of the present disclosure shall be included in the scope of protection of the present disclosure.

Claims

1. A laser projection device, characterized in that: The laser projection device includes a laser light source, a light modulation device, a projection lens, a display control circuit and at least one laser control circuit; The laser light source includes at least one laser, the at least one laser corresponds to the at least one laser control circuit one by one, and the laser is used to emit a laser beam; The display control circuit is used to output a dimming drive signal and an image display drive signal, wherein the dimming drive signal includes an image enable signal and a brightness control signal; The light modulation device is used to modulate the laser beam under the drive of the image display driving signal; the projection lens is used to receive the modulated laser beam and project an image; The laser control circuit includes a controller and a driving circuit, wherein the controller is connected to the display control circuit and the driving circuit, and the controller is used to generate a control signal based on the image enable signal and the brightness control signal; The driving circuit is connected to the corresponding laser, and the driving circuit is used to generate a power supply signal for supplying power to the corresponding laser based on the control signal; The control signal includes a first control signal and a second control signal, the first control signal being a constant level signal output by the controller when the image enable signal is converted from an invalid level to a valid level and the power supply signal does not reach a reference power supply value corresponding to the brightness control signal; The second control signal is a PWM signal output by the controller when the image enable signal is at a valid level and the power supply signal reaches a reference power supply value corresponding to the brightness control signal.

2. The laser projection device according to claim 1, characterized in that: The laser projection device further comprises a frequency adjustment circuit, and the frequency adjustment circuit is connected to the controller; The frequency adjustment circuit is used to control the controller to output a control signal of a first frequency when the image enable signal is converted from an invalid level to a valid level and the power supply signal does not reach a reference power supply value corresponding to the brightness control signal, and to control the controller to output a control signal of a second frequency when the image enable signal is at a valid level and the power supply signal reaches a reference power supply value corresponding to the brightness control signal; The first frequency is less than the second frequency, the control signal of the first frequency includes the first control signal, and the control signal of the second frequency is the second control signal.

3. The laser projection device according to claim 2, characterized in that: The display control circuit is also connected to the frequency adjustment circuit, and the display control circuit is used to output a first frequency adjustment signal when the image enable signal is converted from an invalid level to a valid level and the power supply signal does not reach the reference power supply value corresponding to the brightness control signal, and output a second frequency adjustment signal when the image enable signal is at a valid level and the power supply signal reaches the reference power supply value corresponding to the brightness control signal; The frequency adjustment circuit is used to control the controller to output the control signal of the first frequency when receiving the first frequency adjustment signal; and to control the controller to output the control signal of the second frequency when receiving the second frequency adjustment signal.

4. The laser projection device according to claim 3, characterized in that: The frequency adjustment circuit includes an external resistor circuit, and the external resistor circuit is connected to the display control circuit and the frequency setting pin of the controller; The external resistor circuit is used to adjust the resistance of the external resistor circuit to a first resistance value when receiving the first frequency adjustment signal; and to adjust the resistance of the external resistor circuit to a second resistance value when receiving the second frequency adjustment signal; The controller is used to generate a control signal of a first frequency based on an external resistor circuit with a first resistance value; and to generate a control signal of a second frequency based on an external resistor circuit with a second resistance value.

5. The laser projection device according to claim 1, characterized in that: The controller is also used to enter a standby state when the first duration of the image enable signal being at an invalid level exceeds a predetermined duration; otherwise, not enter the standby state; wherein the predetermined duration is not less than the period of the image enable signal.

6. The laser projection device according to claim 5, characterized in that: The laser projection device further includes a timing circuit, which is connected to the controller and the display control circuit, and is used to record the first duration and send a standby signal to the controller when the first duration exceeds a predetermined duration; The controller is used to enter a standby state when receiving the standby signal; Otherwise, it will not enter the standby state.

7. The laser projection device according to claim 1, characterized in that: The laser projection device further includes a frequency adjustment circuit, which is connected to the controller; The frequency adjustment circuit is used to adjust the frequency of the second control signal output by the controller.

8. The laser projection device according to claim 7, characterized in that: The display control circuit is also connected to the frequency adjustment circuit, and the display control circuit is used to output a frequency adjustment signal to the frequency adjustment circuit; The frequency adjustment circuit is used to adjust the frequency of the second control signal output by the controller based on the frequency adjustment signal.

9. The laser projection device according to claim 8, characterized in that: The frequency adjustment circuit includes an external resistor circuit, which is connected to the display control circuit and the frequency setting pin of the controller. The external resistor circuit is used to adjust the resistance of the external resistor circuit according to the frequency adjustment signal to adjust the frequency of the second control signal output by the controller.

10. The laser projection device according to claim 9, characterized in that: The external resistance circuit includes a first switch tube, a first resistor and a second resistor; One end of the first switch tube is connected to the frequency setting pin of the controller, the other end of the first switch tube is connected to one end of the first resistor, and the control end of the first switch tube is connected to the display control circuit; The other end of the first resistor is grounded; One end of the second resistor is connected to one end of the first switch tube and a frequency setting pin of the controller, and the other end of the second resistor is connected to the other end of the first resistor and is grounded.

11. The laser projection device according to claim 10, characterized in that: The frequency of the second control signal output by the controller includes at least a first operating frequency and a second operating frequency, wherein the first operating frequency is the frequency of the second control signal output by the controller when the first switch tube is turned off, and the second operating frequency is the frequency of the second control signal output by the controller when the first switch tube is turned on, and the period of the controller operating at the first operating frequency is not greater than the period of the controller operating at the second operating frequency.

12. The laser projection device according to any one of claims 1 to 11, characterized in that: The driving circuit outputs an initial supply current; The laser projection device also includes a current adjustment circuit, which is connected to the drive circuit and the laser. The current adjustment circuit is used to adjust the current flowing through the laser based on the comparison result of the initial power supply current and the reference current so that the absolute value of the difference between the current flowing through the laser and the reference current is smaller than the absolute value of the difference between the initial power supply current and the reference current.

13. The laser projection device according to claim 12, characterized in that: One end of the current regulating circuit is connected to the output end of the laser control circuit and the input end of the laser, and the other end of the current regulating circuit is connected to the output end of the laser; The current adjustment circuit is used for controlling the current flowing through the laser to be smaller than the initial supply current when the initial supply current is greater than the reference current.

14. The laser projection device according to claim 13, characterized in that: The current regulation circuit includes a first control subcircuit and a first current control subcircuit; The first control subcircuit is connected to the input end of the laser, and the first control subcircuit is used to output a first current adjustment signal of a first state when the initial power supply current is greater than the reference current, and to output a first current adjustment signal of a second state when the initial power supply current is not greater than the reference current; The first current control subcircuit includes a second switch tube, one end of the second switch tube is connected to the output end of the laser control circuit and the input end of the laser, the other end of the second switch tube is connected to the output end of the laser, and the control end of the second switch tube is connected to the first control subcircuit; The first current control subcircuit is used to control the current flowing through the second switch tube based on the first current adjustment signal in the first state, and to disconnect the second switch tube based on the first current adjustment signal in the second state.

15. The laser projection device according to claim 14, characterized in that: The first current control subcircuit also includes a third resistor, one end of the third resistor is connected to one end of the second switch tube, and the other end of the third resistor is connected to the output end of the laser.

16. The laser projection device according to claim 15, characterized in that: The first control subcircuit includes a first filtering subcircuit and a first operational amplifier; The input end of the first filtering subcircuit is connected to the input end of the laser, and the first filtering subcircuit is used to filter out the reference voltage corresponding to the reference current in the power supply voltage of the input end of the laser, and output the filtered power supply voltage; The non-inverting input terminal of the first operational amplifier is connected to the output terminal of the first filtering sub-circuit, the inverting input terminal of the first operational amplifier is connected to one end of the third resistor, and the output terminal of the first operational amplifier is connected to the control terminal of the second switch tube.

17. The laser projection device according to claim 16, characterized in that: The first filtering subcircuit includes a first capacitor, a second capacitor, a second operational amplifier, a fourth resistor and a fifth resistor; One end of the first capacitor is connected to the input end of the laser, the other end of the first capacitor is connected to one end of the second capacitor, and the other end of the second capacitor is connected to the non-inverting input end of the second operational amplifier; The inverting input terminal of the second operational amplifier is connected to the output terminal of the second operational amplifier, and the output terminal of the second operational amplifier is connected to the non-inverting input terminal of the first operational amplifier; One end of the fourth resistor is connected to the other end of the first capacitor and one end of the second capacitor, and the other end of the fourth resistor is connected to the output end of the second operational amplifier; One end of the fifth resistor is connected to the other end of the second capacitor, and the other end of the fifth resistor is grounded.

18. The laser projection device according to claim 17, characterized in that: The first control subcircuit further includes a third operational amplifier, a sixth resistor and a seventh resistor; The non-inverting input terminal of the third operational amplifier is connected to the output terminal of the second operational amplifier, the inverting input terminal of the third operational amplifier is connected to one end of the sixth resistor, and the output terminal of the third operational amplifier is connected to the non-inverting input terminal of the first operational amplifier. catch; The other end of the sixth resistor is grounded; One end of the seventh resistor is connected to the output end of the third operational amplifier, and the other end of the seventh resistor is connected to the inverting input end of the third operational amplifier and one end of the sixth resistor.

19. The laser projection device according to claim 16, characterized in that: The first control subcircuit also includes a fourth operational amplifier, a non-inverting input terminal of the fourth operational amplifier is connected to the input terminal of the laser, a reverse input terminal of the fourth operational amplifier is connected to the output terminal of the fourth operational amplifier, and the output terminal of the fourth operational amplifier is connected to the input terminal of the first filtering subcircuit.

20. The laser projection device according to claim 14, characterized in that: The display control circuit is also connected to the laser control circuit, and is used to adjust the dimming drive signal based on the current flowing through the second switch tube to increase the reference current.

21. The laser projection device according to claim 12, characterized in that: One end of the current regulating circuit is connected to the input end of the laser control circuit, and the other end of the current regulating circuit is connected to the output end of the laser control circuit and the input end of the laser; The current adjustment circuit is used for controlling the current flowing through the laser to be greater than the initial supply current when the initial supply current is less than the reference current.

22. The laser projection device according to claim 21, characterized in that: The current regulating circuit includes a second control subcircuit and a second current control subcircuit; The second control subcircuit is connected to the input end of the laser, and the second control subcircuit is used to output a second current adjustment signal in a first state when the initial power supply current is less than the reference current, and to output a second current adjustment signal in a second state when the initial power supply current is not less than the reference current; The second current control subcircuit comprises a fourth switch tube, one end of the fourth switch tube is connected to the input end of the laser control circuit, and the other end of the fourth switch tube is connected to the output end of the laser control circuit and the input end of the laser; The second current control subcircuit is used to control the current flowing through the fourth switch tube based on the second current adjustment signal in the first state, and to disconnect the fourth switch tube based on the second current adjustment signal in the second state.

23. The laser projection device according to claim 22, characterized in that: The second current control subcircuit also includes a ninth resistor, one end of the ninth resistor is connected to the other end of the fourth switch tube, and the other end of the ninth resistor is connected to the input end of the laser and the output end of the laser control circuit.

24. The laser projection device according to claim 23, characterized in that: The second control subcircuit includes a second filtering subcircuit, an inverting subcircuit and a fifth operational amplifier; The input end of the second filtering subcircuit is connected to the input end of the laser, and the second filtering subcircuit is used to filter out the reference voltage corresponding to the reference current in the power supply voltage of the input end of the laser, and output the filtered power supply voltage; The reverse subcircuit is connected to the output end of the second filtering subcircuit, and the reverse subcircuit is used to output a reverse filtered supply voltage; The in-phase input terminal of the fifth operational amplifier is connected to the output terminal of the reverse sub-circuit, the reverse input terminal of the fifth operational amplifier is connected to one end of the ninth resistor and the other end of the fourth switch tube, and the output terminal of the fifth operational amplifier is connected to the control terminal of the fourth switch tube.

25. The laser projection device according to claim 24, characterized in that: The reverse sub-circuit includes a seventh operational amplifier, a twelfth resistor and a thirteenth resistor; One end of the twelfth resistor is connected to the second filtering sub-circuit, and the other end of the twelfth resistor is connected to the inverting input end of the seventh operational amplifier; The non-inverting input terminal of the seventh operational amplifier is grounded, and the output terminal of the seventh operational amplifier is connected to the non-inverting input terminal of the fifth operational amplifier; One end of the thirteenth resistor is connected to the other end of the twelfth resistor and the inverting input end of the seventh operational amplifier, and the other end of the thirteenth resistor is connected to the output end of the seventh operational amplifier.

26. The laser projection device according to claim 24, characterized in that: The second control subcircuit also includes an eighth operational amplifier, the non-inverting input terminal of the 84 operational amplifier is connected to the input terminal of the laser, the inverting input terminal of the eighth operational amplifier is connected to the output terminal of the eighth operational amplifier, and the output terminal of the eighth operational amplifier is connected to one end of the sixth capacitor.

27. A control method, characterized in that: The control method is applied to the laser projection device according to any one of claims 1 to 26, and the method comprises: The laser emits a laser beam to provide an illumination beam for the device; The display control circuit outputs a dimming drive signal and an image display drive signal, wherein the dimming drive signal includes an image enable signal and a brightness control signal; The light modulation device modulates the laser beam under the drive of the image display drive signal; The projection lens receives the modulated laser beam and projects an image; The controller generates a control signal based on the image enable signal and the brightness control signal; The driving circuit generates a power supply signal for supplying power to the corresponding laser based on the control signal; Among them, the control signal includes a first control signal and a second control signal; the first control signal is a constant level signal output by the controller when the image enable signal is converted from an invalid level to a valid level and the power supply signal does not reach a reference power supply value corresponding to the brightness control signal; the second control signal is a PWM signal output by the controller when the image enable signal is a valid level and the power supply signal reaches a reference power supply value corresponding to the brightness control signal.

28. A laser control circuit, characterized in that: The laser control circuit includes a controller and a drive circuit; The controller is connected to the display control circuit and the driving circuit, and the controller is used to generate a control signal based on an image enable signal and a brightness control signal; The driving circuit is connected to the corresponding laser, and the driving circuit is used to generate a power supply signal for supplying power to the corresponding laser based on the control signal; Wherein, the control signal includes a first control signal and a second control signal; the first control signal is a constant level signal output by the controller when the image enable signal is converted from an invalid level to a valid level and the power supply signal does not reach a reference power supply value corresponding to the brightness control signal; The second control signal is a PWM signal output by the controller when the image enable signal is at a valid level and the power supply signal reaches a reference power supply value corresponding to the brightness control signal.

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