Projection equipment and driving method of laser light source thereof

Abstract

The invention provides projection equipment and a driving method of a laser light source thereof, and relates to the technical field of projection display, the projection equipment comprises a power supply circuit, a display control circuit, a laser light source and at least one light driving circuit, and the laser light source comprises at least one laser; the power supply circuit is respectively connected with the display control circuit and the at least one light driving circuit and is used for supplying power to the display control circuit and the at least one light driving circuit; the display control circuit is connected with the at least one light driving circuit and is used for providing a dimming signal for the at least one light driving circuit; the light driving circuits are connected with the lasers one by one, the light driving circuits are connected with the anodes of the lasers, and the cathodes of at least one laser are connected; and the light driving circuit is used for providing driving current for the connected laser based on the dimming signal, and the laser is used for emitting light under the driving of the driving current. According to the invention, the influence of electromagnetic waves radiated by the projection equipment on elements can be reduced.

Description

Projection device and driving method of laser light source thereof

[0001] This disclosure claims priority to Chinese patent application No. 202211128274.X, filed on September 16, 2022, with the invention name “Projection device and driving method of its light source”, and Chinese patent application No. 202310978399.X, filed on August 4, 2023, with the invention name “Laser projection device, control method and laser driving module”, the entire contents of which are incorporated by reference into this disclosure. Technical Field

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

[0003] Projection equipment, such as laser projectors, utilizes Digital Light Processing (DLP) technology to digitally process image signals and then project them through a laser beam. Laser projectors are widely used due to their vivid colors, high brightness, and flexible screen sizes.

[0004] Summary of the Invention

[0005] The present disclosure provides a projection device and a method for driving its light source, which can solve the problem in related technologies that electromagnetic waves radiated by the projection device affect the working state and performance of its internal components and other electronic devices. The technical solution is as follows:

[0006] In a first aspect, a projection device is provided, comprising a power supply circuit, a display control circuit, a laser light source, and at least one light driving circuit, wherein the laser light source comprises at least one laser;

[0007] The power supply circuit is connected to the display control circuit and the at least one light driving circuit respectively, and is used to supply power to the display control circuit and the at least one light driving circuit;

[0008] The display control circuit is connected to the at least one light driving circuit and is used to provide a dimming signal to the at least one light driving circuit;

[0009] The optical driving circuit and the laser are connected one by one, and the optical driving circuit and the anode of the laser are connected, and the cathode of the at least one laser is interconnected;

[0010] The optical driving circuit is used to provide a driving current to the connected laser based on the dimming signal, and the laser is used to emit light under the driving of the driving current.

[0011] In a second aspect, a projection device is provided, characterized by a power supply circuit, a display control circuit, a laser light source and at least one light driving circuit, wherein the laser light source includes at least one laser;

[0012] The power supply circuit and the at least one optical driving circuit are arranged on different boards, and the optical driving board where the at least one optical driving circuit is located is close to the laser light source;

[0013] The power supply circuit is connected to the display control circuit and is used to supply power to the display control circuit;

[0014] The display control circuit is connected to the at least one light driving circuit and is used to provide a dimming signal to the at least one light driving circuit;

[0015] The optical driving circuit is connected to the laser one by one and is used to provide a driving current to the connected laser based on the dimming signal, and the laser is used to emit light under the driving current.

[0016] In a third aspect, a method for driving a laser light source is provided, which is applied to the projection device according to the first and second aspects, the method comprising:

[0017] The power supply circuit supplies power to the display control circuit and the at least one light driving circuit;

[0018] The display control circuit provides a dimming signal to the at least one light driving circuit;

[0019] The optical driving circuit provides a driving current to the connected laser based on the dimming signal;

[0020] The laser emits light when driven by the driving current.

[0021] In this embodiment, the laser's anode is connected to the optical drive circuit, and its cathode is connected together. For example, the laser's cathode can be grounded. This grounding of the laser's cathode effectively shortens the transmission path through which the drive current flows, thereby reducing the current loop area of ​​the drive current. Furthermore, the impact of electromagnetic waves radiated by the projection device on the performance and operating status of components within the projection device and other electronic devices surrounding the projection device is reduced.

[0022] For another example, the cathode of the laser can be connected to the line between the power circuit and the optical drive circuit, so that the voltage V d , is the power supply output voltage V output by the optical drive circuit out , and the power supply input voltage V inThen, in order to promote the voltage V across the laser d Its rated driving voltage V′ d , you only need to control the light drive circuit to output V out , relative to the input V in , increase V′ d The voltage raised by the optical drive circuit is not affected by the input V in Influence, then, the power supply input voltage V output by the power supply circuit in , it is not limited by the rated drive voltage of the laser. in It is not easy for components to be burned out due to excessive input current, nor is it easy for components to be damaged due to excessive input voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0024] FIG1 is a circuit diagram of a projection device provided by an embodiment of the present disclosure;

[0025] FIG2 is a circuit diagram of a projection device in the related art;

[0026] FIG3 is a schematic diagram of a transmission circuit of a driving current for driving a laser to emit light provided by an embodiment of the present disclosure;

[0027] FIG4 is a circuit diagram of a projection device provided by an embodiment of the present disclosure;

[0028] FIG5 is a circuit diagram of a projection device provided by an embodiment of the present disclosure;

[0029] FIG6 is a schematic diagram of a transmission circuit of a driving current for driving a laser to emit light provided by an embodiment of the present disclosure;

[0030] FIG7 is a schematic diagram of a transmission circuit of a driving current for driving a laser to emit light provided by an embodiment of the present disclosure;

[0031] FIG8 is a circuit diagram of a projection device provided by an embodiment of the present disclosure;

[0032] FIG9 is a circuit diagram of a projection device provided by an embodiment of the present disclosure;

[0033] FIG10 is a circuit diagram of a projection device provided by an embodiment of the present disclosure;

[0034] FIG11 is a circuit diagram of a projection device provided by an embodiment of the present disclosure;

[0035] FIG12 is a circuit diagram of a projection device provided by an embodiment of the present disclosure;

[0036] FIG13 is a circuit diagram of a projection device provided by an embodiment of the present disclosure;

[0037] FIG14 is a circuit diagram of a projection device provided by an embodiment of the present disclosure;

[0038] FIG15 is a schematic diagram showing changes of an Adim signal, a Pwm signal, a Drv signal, and a driving current over time, respectively, provided by an embodiment of the present disclosure;

[0039] FIG16 is a circuit diagram of a projection device provided by an embodiment of the present disclosure;

[0040] FIG17 is a schematic diagram of a driving current frequency and corresponding radio disturbance limit values ​​provided in an embodiment of the present application;

[0041] FIG18 is a schematic diagram of a transmission circuit of a driving current for driving a laser to emit light provided by an embodiment of the present disclosure;

[0042] FIG19 is a schematic flow chart of a driving method provided in an embodiment of the present application;

[0043] FIG20 is a schematic flow chart of a driving method provided in an embodiment of the present application;

[0044] FIG21 is a schematic diagram of the hardware structure of the electronic device provided in this application. DETAILED DESCRIPTION

[0045] In order to make the objectives, technical solutions and advantages of the present disclosure more clear, the embodiments of the present disclosure will be further described in detail below with reference to the accompanying drawings.

[0046] FIG1 is a schematic diagram of the circuitry of a projection device provided by an embodiment of the present disclosure. Referring to FIG1 , the projection device includes a power supply circuit 10, a multimedia processing circuit 20, a display control circuit 30, an optical drive circuit 40, a laser light source 50, an optical-mechanical assembly 60, and a projection lens 70.

[0047] The power supply circuit 10 can output a DC voltage. For example, the power supply circuit 10 can output a DC voltage of 12V or 24V to the light driving circuit 40 .

[0048] For example, the power supply circuit 10 can receive the mains power, and after filtering and transforming the mains power, provide a DC power supply input voltage Vin to the light driving circuit 40 .

[0049] Continuing with reference to FIG1 , the power supply circuit 10 may include a bridge rectifier circuit 11 and a power conversion circuit 12, wherein the power conversion circuit 12 may include a power factor correction (PFC) circuit 121 and an LLC circuit 122. The rectifier bridge circuit 11 receives the AC power, rectifies and filters the AC power, and then outputs the power to the PFC circuit 121 and the LLC circuit 122. The PFC circuit 121 and the LLC circuit 122 perform power conversion to supply power to the load, such as outputting a DC power supply input voltage V to the light drive circuit 40. in .

[0050] The bridge rectifier circuit is the most widely used type of 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, AC current with varying direction and magnitude can be converted into DC.

[0051] The PFC circuit uses inductor compensation to adjust the input current waveform to make it as similar as possible to the input voltage waveform, so that the power factor correction value approaches 100%. The power factor refers to the relationship between real power and total power consumption (apparent power), that is, the ratio of real power to total power consumption (apparent power).

[0052] The LLC circuit is a resonant circuit that achieves a constant output voltage by controlling the switching frequency (frequency regulation). This circuit consists of a single-port network consisting of inductors, capacitors, and resistors. When the port voltage and current waveforms are in phase at certain operating frequencies, the circuit is said to be resonant. A circuit that can resonate is called a resonant circuit.

[0053] 1 , the power supply circuit 10 is electrically connected to the multimedia processing circuit 20 , the display control circuit 30 , the optical driving circuit 40 , the laser light source 50 , the optical-mechanical assembly 60 and the projection lens 70 to supply power to these loads.

[0054] It should be noted that the power supply circuit 10 can also simultaneously supply power to other functional modules and circuits in the projection device, such as the human eye protection module, the fan and the WIFI module, to ensure the normal operation of all parts of the projection device.

[0055] The multimedia processing circuit 20 may also be referred to as a field programmable gate array (FPGA) circuit.

[0056] 1 , the multimedia processing circuit 20 is configured to receive video signals transmitted by a TV board. For example, the multimedia processing circuit 20 can receive video signals transmitted by a TV board via various communication interfaces, such as a universal serial bus (USB) interface.

[0057] The TV board may be provided with a system on chip (SoC) that can decode data in different data formats into a normalized format and transmit the normalized format data (called a video signal) to the multimedia processing circuit 20 through a connector.

[0058] After receiving the video signal, the multimedia processing circuit 20 may perform some processing on the video signal, such as motion estimation and motion compensation (MEMC) frequency multiplication processing, image correction processing, image brightness processing, image clarity processing, and image color processing.

[0059] Continuing to refer to FIG. 1 , the multimedia processing circuit 20 is connected to the display control circuit 30 to transmit the processed video signal to the display control circuit 30 .

[0060] It should be noted that the multimedia processing circuit 20 usually exists as an enhanced function circuit. In some low-cost solutions, this circuit part may not be provided, and the display control circuit 30 receives the video signal output by the TV board.

[0061] After receiving the video signal, the display control circuit 30 can decode and format-convert the video signal, further process the video signal (eg, perform geometric correction processing), and generate a dimming signal based on the processed video signal.

[0062] Continuing to refer to FIG. 1 , the display control circuit 30 is connected to the light driving circuit 40 , and the display control circuit 30 can transmit a dimming signal to the light driving circuit 40 .

[0063] The dimming signal may include an analog dimming (Adim) signal and a pulse width modulation (Pwm) signal.

[0064] The Pwm signal is used to control the presence or absence of the driving current transmitted to the laser light source 50 , and the Adim signal in the dimming signal is used to control the current value of the driving current.

[0065] The optical driving circuit 40 may also be referred to as a laser driving circuit, specifically a DC-DC conversion circuit, and specifically may be a boost circuit or a buck circuit.

[0066] The optical driving circuit 40 is used to receive the dimming signal and the power supply input voltage of the power supply circuit 10 , and convert the input power supply input voltage into a power supply output voltage based on the dimming signal, and output a driving current to the laser light source 50 .

[0067] The laser light source 50 emits light under the driving current and transmits the light to the optomechanical assembly 60 .

[0068] The laser light source 50 may include at least one laser 51 , and the colors of the light beams emitted by the at least one laser 51 may be the same or different.

[0069] Continuing to refer to FIG. 1 , each laser 51 may include a plurality of light-emitting diodes (LEDs) 511 connected in series.

[0070] The laser light source 50 may include a monochromatic laser or a multicolor laser, such as a dual-color laser including a red laser and a blue laser, or as shown in FIG1 , a three-color laser including a red laser, a blue laser, and a green laser.

[0071] The number of the optical driving circuits 40 is the same as the number of the lasers 51 , and they correspond one to one.

[0072] Continuing with Figure 1 , the laser light source 50 includes three lasers: a red laser, a blue laser, and a green laser. The projection device then includes a red light drive circuit 40_R, a green light drive circuit 40_G, and a blue light drive circuit 40_B. Each of the three lasers 51 is connected to a corresponding light drive circuit 40.

[0073] The three color lasers 51 can emit red light, green light and blue light respectively when driven by driving current. Based on the color synthesis principle in optics, it can be known that white light can be obtained after the three colors of light are combined and homogenized.

[0074] Continuing to refer to FIG. 1 , the light beam emitted by the laser light source 50 is transmitted to the optical-mechanical assembly 60 .

[0075] The optomechanical assembly 60 integrates a digital micromirror device (DMD) and a DMD driver circuit. The DMD is the core optical modulation component of the optomechanical assembly 60. The DMD driver circuit drives the DMD based on the video signal. Thus, under the control of the DMD driver circuit, the DMD modulates the light beam emitted by the laser light source 50 to produce the image to be projected.

[0076] For example, the DMD receives a driving control signal corresponding to an image signal, and flips the thousands of tiny mirrors on its surface to a positive or negative angle corresponding to the driving signal, forming the light beam irradiating its surface into an image to be projected and reflected into the projection lens 70.

[0077] Continuing with FIG1 , the optical engine assembly 60 transmits the image to be projected to the projection lens 70 . The projection lens 70 magnifies the image to be projected and projects it onto a target object in the form of a light beam. The target object may be a projection screen or a wall.

[0078] The projection lens 70 may be an ultra-short-throw projection lens, which is used to project an image beam onto a projection screen, thereby displaying a projected image. The laser projection device of this embodiment may be an ultra-short-throw laser projection device.

[0079] It should be noted that the power supply circuit 10 and the light driving circuit 40 can be integrated. For example, the power supply circuit 10 and the light driving circuit 40 are integrated on a single board.

[0080] Alternatively, the power supply circuit 10 and the optical drive circuit 40 may be separately arranged. For example, the power supply circuit 10 is arranged on a single board, which can be recorded as a power board, and the optical drive circuit 40 is arranged on another single board, which can be recorded as a optical drive board.

[0081] It should be noted that the multimedia processing circuit 20, the display control circuit 30 and the optical-mechanical assembly 60 can be arranged on a single board, for example, the single board is recorded as a display board.

[0082] It should be noted that the multimedia processing circuit 20 may also include a system on chip (SoC), which may include a digital light processor (DLP) and a driver.

[0083] In the DLP control architecture, the laser light source 50 must coordinate with the operating timing of the DLP and the DMD of the optical-mechanical assembly 60. Specifically, the DLP outputs an image enable signal, also known as a primary color enable signal, typically represented as X_EN, where X is the abbreviation for the different primary colors, and also outputs a dimming signal. Along with the DMD timing, the laser light source must synchronously output the corresponding primary color beams during the modulation process of the different primary color image components. In other words, the DLP outputs the primary color enable signal to instruct the laser light source to illuminate a certain color laser, and outputs the dimming signal to instruct the laser light source to illuminate the corresponding color laser at a certain brightness.

[0084] The above is a brief introduction to projection equipment to facilitate a better understanding of projection equipment. The following will introduce some problems existing in current projection equipment.

[0085] Because the light driver circuit 40 operates at a high frequency and current, and its operating state switches between on and off at high frequency and periodically, the changing electric field generated by this switching of operating states generates a changing magnetic field, which in turn generates a changing electric field. These changing electric and magnetic fields generate electromagnetic waves that can radiate outward, which can also be referred to as electromagnetic disturbance.

[0086] Among them, the electromagnetic waves radiated by the projection device should be below a certain limit, otherwise the electromagnetic waves will easily affect the working state of the internal components of the projection device and the working state of other electronic equipment around the projection device, thereby damaging the performance of its internal components and other electronic equipment.

[0087] Current projection equipment has strong electromagnetic interference for the following reasons.

[0088] FIG2 is a schematic diagram of a partial structure of a projection device in the related art. Referring to FIG2 , a power supply circuit and a plurality of light driving circuits may be integrated on a power supply board of the projection device.

[0089] As shown in Figure 2, the anodes (i.e., positive poles) of the multiple lasers 51 and the multiple optical driving circuits are all connected to the power supply circuit, and the cathode (i.e., negative end) of each laser is connected to its corresponding optical driving circuit, and each optical driving circuit is also connected to the ground end.

[0090] Then, when each optical driver circuit drives the laser to emit light, the driving current flowing through the laser can flow in the following direction: the positive electrode of the power circuit - the laser - the optical driver circuit - the ground terminal. The ground terminal can be the common ground terminal of the power board. As a result, the transmission path of the driving current can form a loop (i.e., a driving current loop. Unless otherwise specified, the current loop mentioned in this article refers to the current loop of the driving current).

[0091] The connection mode in which the anodes of the multiple lasers are directly connected to the power supply circuit and the cathodes are respectively connected to a light driving circuit is called common anode drive.

[0092] It should be noted that common anode drive is generally related to the packaging method of the laser light source. For example, a common anode laser light source packaging method is to package multiple lasers together, and the positive and negative poles of each laser are independent of each other. Then, the packaged laser light source includes multiple anode pins and multiple cathode pins. When connecting a laser light source with this packaging method to the optical drive circuit, the multiple anode pins are generally connected together and then connected to the power circuit. This wiring method is called common anode drive.

[0093] This common anode driving laser emission method often results in strong electromagnetic interference for the following reasons.

[0094] The high-frequency on-off switching of transistor switches in optical drive circuits causes high-frequency variations in the drive current. These changes in the drive current can easily cause changes in the magnetic and electric fields surrounding the drive current's transmission path. These changes in the magnetic and electric fields generate electromagnetic waves. These electromagnetic waves are also called electromagnetic interference (or noise). The faster the rate of change of the drive current, the wider the bandwidth of the noise. The greater the average value of the change in the drive current signal value, the greater the amplitude of the noise.

[0095] Among them, during the transmission process of the driving current, the electric field strength E of the electromagnetic radiation interference electric field generated around its transmission line can meet the following requirements:

[0096] Wherein, f is the frequency of the driving current, A is the current loop area of ​​the driving current, which is positively correlated with the length of the transmission line of the driving current. The unit of the current loop area can be square centimeters (cm 2 ), I is the current value of the driving current (i.e., the intensity of the driving current), and the unit of the driving current can be milliamperes (mA). r is the distance between the test antenna used to test the electric field intensity E and the transmission line of the driving current. Optionally, the value of r can be 3 meters.

[0097] Referring to the above formula (1), it can be seen that the electric field intensity E is positively correlated with the current loop area A of the driving current, the current intensity I of the driving current, and the frequency f of the driving current.

[0098] To ensure the projection function of the projection device, the frequency f of the driving current and the current intensity I of the driving current are both fixed values.

[0099] Therefore, the current loop area A of the driving current is the main factor affecting the current intensity E. Since the current loop area of ​​the driving current is positively correlated with the length of the driving current transmission line, the length of the driving current transmission line is the main factor affecting the current intensity E.

[0100] Therefore, referring to Figure 3, it can be seen that in a projection device using a common anode drive, the drive current flows from the power board to the laser and then needs to flow back to the power board to connect with the optical drive circuit. The dotted arrow in Figure 3 indicates the transmission direction of the drive current, and the corresponding current loop area is recorded as S1. The power board and the laser are located in different positions in the projection device, with a certain distance between them. Therefore, it can be seen that the drive current path includes the path from the power board to the laser and the path from the laser back to the power board. The drive current transmission path is relatively long. Therefore, the current loop area A of this drive current is also large.

[0101] Then, when the electromagnetic waves generated by the projection device exceed a certain limit, the working state and performance of the components inside the projection device will be affected.

[0102] For example, these electromagnetic waves can interfere with the operation and performance of the infrared sensor in the projection device, which is designed to protect human eyes from approaching the projection lens. They can also interfere with the operation and performance of the far-field voice circuit in the projection device used to recognize user voices, and they can also interfere with the operation and performance of the audio output circuit in the projection device. Furthermore, the electromagnetic waves radiated by the projection device can affect the operation of other electronic devices around the projection device, thereby damaging their performance.

[0103] The above is a problem existing in current projection devices. In addition, there are other problems with projection devices, which are described below.

[0104] As described above, the light driving circuit 40 is a DC-DC conversion circuit, which can be a step-up circuit or a step-down circuit.

[0105] In the related art, in order to improve the uniformity of the circuit, the light driving circuits 40 corresponding to different lasers 51 are usually set to the same circuit type, for example, all are step-up circuits, or all are step-down circuits. Figure 4 is a schematic diagram of the connection between the power supply circuit 10, the light driving circuit 40 and the laser light source 50 of the projection device. As shown in Figure 4, taking the projection device including three-color lasers as an example, the light driving circuit 40 corresponding to each laser 51 receives the power supply input voltage V output by the power supply circuit 10. in and the power supply input voltage V in , converted to the corresponding power supply output voltage V out , and output to the corresponding laser 51 through the output end.

[0106] 4, the anode of the laser 51 is connected to the output terminal of the optical drive circuit 40, and the cathode of the laser 51 is grounded. Then, the potential of the anode of the laser 51 is V out , the cathode potential is 0, so the supply voltage V across the laser is d The power supply output voltage V out .

[0107] Then, when the projection equipment is working, the power supply output voltage V out The size of the laser is used to adjust the voltage V across the laser. d , and then adjust the brightness of the laser. When the laser emits light, the voltage across its two ends can be recorded as the rated driving voltage, recorded as V' d , then, when the voltage V across the laser d V′ d When the laser is on, it can emit light.

[0108] Because the supply voltage V d Equal to V out Therefore, in the boost circuit, the light driving circuit 40 needs to supply the input voltage V in Increase to V' d , the increase is V′ d -V in , because it cannot increase negative value, so, V in Less than or equal to V′ d .

[0109] In the step-down circuit, the light driving circuit 40 needs to convert the power supply input voltage V in Reduce to V′ d , the reduction amount is V in -V′ d , because it cannot reduce the negative value, so, V in Greater than or equal to V′ d .

[0110] It can be seen that the power supply input voltage V output by the power supply circuit 10 in The size of V is limited and needs to be satisfied in the boost circuit. in ≤V′ d , in the step-down circuit, V in ≥V′ d .

[0111] For example, in actual applications, the brightness of different lasers is different and may vary greatly, so the rated driving voltage V′ of different lasers is d Therefore, in the application of the optical drive circuit as a boost circuit, it is necessary to set the power supply input voltage V based on the rated drive voltage of the laser with the lowest brightness.in In applications where the optical drive circuit is a step-down circuit, the power supply input voltage V needs to be set based on the rated drive voltage of the laser with the highest brightness. in .

[0112] For example, the rated driving voltages of red laser, blue laser and green laser are 8V, 15V and 18V respectively. In the application of the optical driving circuit as a boost circuit, the red driving circuit needs to increase the power supply input voltage V in Increase to 8V, the blue light driving circuit needs to increase the input voltage V in Increase to 15V, the green light driver circuit needs to increase the power supply input voltage V in Increase to 18V.

[0113] Because the optical drive circuit is a boost circuit type, the power input voltage V in , needs to be less than or equal to the rated drive voltage V' of all lasers d Therefore, when setting the power supply input voltage V in When the voltage is 8V, the power supply input voltage V in Less than or equal to 8V, such as the power supply input voltage V in is 6V, then the three light drive circuits will supply 6V to the input voltage V in , converted into 8V, 15V and 18V power supply output voltage V respectively out .

[0114] Due to the selected power supply input voltage V in The output power of the power supply circuit is relatively low, so the power supply circuit will input a relatively large current into the three light driving circuits, which is consistent with the selected V in For lasers with significantly different rated drive voltages, some components in the connected optical drive circuit will be damaged due to the large current. For example, for a laser with a rated drive voltage of 18V, some components in the connected optical drive circuit will be damaged due to the large current.

[0115] In the application of the light driving circuit as a step-down circuit, the red light driving circuit needs to change the power supply input voltage V in Reduced to 8V, the blue light driving circuit needs to reduce the input voltage V in Reduced to 15V, the green light driver circuit needs to reduce the input voltage V in Reduce to 18V.

[0116] Since the optical drive circuit is a step-down circuit type, the power supply input voltage V in , needs to be greater than or equal to the rated drive voltage V' of all lasers d Therefore, when setting the power supply input voltage Vin When setting the power supply input voltage V in When the voltage is 18V, the power supply input voltage V in Greater than or equal to 18V, such as the power supply input voltage V in is 21V, then the three light drive circuits will be 21V power supply input voltage V in , converted into 8V, 15V and 18V power supply output voltage V respectively out .

[0117] This is consistent with the selected V in Lasers with significantly different rated drive voltages will have some components in the connected optical drive circuit damaged by the higher voltage. For example, a laser with a rated drive voltage of 8V will have some components in the connected optical drive circuit damaged by the higher voltage.

[0118] It can be seen that the optical drive circuit, whether it is a boost circuit or a buck circuit, will be affected by the selected V in , and the rated driving voltage at both ends of some of the lasers is quite different, which results in higher current or voltage of some components in the optical driving circuits connected to these lasers, making the service life of these optical driving circuits shorter.

[0119] In addition, in the related art, once a short circuit or other fault occurs in the optical drive circuit, the power supply input voltage V in The voltage is applied to the laser connected to the short-circuited optical drive circuit, causing the laser to be subjected to a large voltage and thus damaged.

[0120] Based on the above problems, this embodiment provides a projection device, which can solve the above problems. The technical features of the projection device will be introduced below.

[0121] As shown in Figure 4, the projection device may include a power supply circuit 10, a display control circuit 30, a laser light source 50 and at least one light driving circuit 40, wherein the laser light source 50 includes at least one laser 51, the laser 51 and the light driving circuit 40 correspond one to one, and one laser 51 is driven by one light driving circuit 40 to emit light.

[0122] For the introduction of the power supply circuit 10 and the display control circuit 30 , please refer to the above description and will not be repeated here.

[0123] The number of lasers 51 may be one or more. In the solution of multiple lasers, a three-color laser as shown in FIG. 1 may be used as an example for illustration.

[0124] As shown in Figure 4, the output end of the power supply circuit 10 is respectively connected to the first end 1 (i.e., the input end) of the display control circuit 30 and at least one light driving circuit 40. The power supply circuit 10 is used to supply power to the display control circuit 30 so that the display control circuit 30 can send and receive signals (such as video signals and dimming signal lights), and the power supply circuit 10 is used to supply power to at least one light driving circuit 40 to provide a driving voltage to at least one light driving circuit 40.

[0125] The driving voltage mentioned in this article, unless otherwise specified, is the driving voltage of the input light driving circuit, that is, V in The voltage outputted by the optical drive circuit 40 is the power supply output voltage unless otherwise specified, i.e. V out .

[0126] 4 , the display control circuit 30 is connected to the second end 2 of at least one light driving circuit 40 , so that the display control circuit 30 provides a dimming signal to each light driving circuit 40 .

[0127] As described above, the dimming signal may include an Adim signal for controlling the magnitude of the driving current and a Pwm signal for controlling the presence or absence of the driving current.

[0128] The third end 3 (i.e., the output end) of each light driving circuit 40 is connected to the first end 1 (i.e., the anode end) of a corresponding laser 51. Each light driving circuit 40 is used to provide a driving current to the laser connected thereto based on the dimming signal under the drive of the driving voltage.

[0129] The driving currents described herein, unless otherwise specified, refer to the currents input to the laser 51 .

[0130] As shown in FIG5 , the second end 2 (ie, cathode end) of at least one laser 51 is interconnected, and each laser 51 is configured to emit light under the driving of a driving current.

[0131] In the disclosed embodiment, each of the at least one light driving circuit 40 can adjust the current value of the driving current it outputs based on the Adim signal in the received dimming signal, and can control the presence or absence of the driving current it outputs based on the PWM signal in the dimming signal. For example, within 1 second, if the duty cycle of the PWM signal is 50%, the light driving circuit 40 outputs the driving current for 0.5 seconds within 1 second, and does not output the driving current for the remaining 0.5 seconds.

[0132] The current value of the driving current may be positively correlated with the signal value of the Adim signal. That is, when the signal value of the Adim signal is larger, the current value of the driving current is larger.

[0133] In one example, the display control circuit 30 can simultaneously output a dimming signal (including an Adim signal and a PWM signal) to at least one light driving circuit 40. Therefore, the display control circuit 30 may include at least one group of ports for outputting dimming signals, each group of ports including two ports, each for outputting an Adim signal and a PWM signal, and both ports in each group of ports are connected to one light driving circuit 40.

[0134] For example, as shown in FIG5 , the display control circuit 30 can output the Adim_R signal and the Pwm_R signal to the red light driving circuit 40_R, output the Adim_G signal and the Pwm_G signal to the green light driving circuit 40_G, and output the Adim_B signal and the Pwm_B signal to the blue light driving circuit 40_B.

[0135] It should be pointed out that the display control circuit 30 may not include grouped ports, but may include multiple ports, each port having a pin for transmitting Adim signals and a pin for transmitting Pwm signals, that is, the pin for transmitting Adim signals and the pin for transmitting Pwm signals are integrated into one port.

[0136] As described above, the cathodes of at least one laser 51 are interconnected, and the cathodes of at least one laser 51 are interconnected, which can reduce the length of the transmission line of the driving current and also achieve unrestricted selection of the power supply input voltage of the optical driving circuit 40.

[0137] How to reduce the length of the transmission line of the driving current and how to achieve unrestricted selection of the power supply input voltage of the optical driving circuit 40 will be described in detail below.

[0138] As shown in FIG5 , the anodes of the plurality of lasers 51 are respectively connected to one optical driving circuit 40 , while the cathodes are interconnected, which can be referred to as common cathode driving.

[0139] It should be noted that common cathode drive is generally related to the packaging method of the laser light source. For example, a common cathode type laser light source packaging method is to package multiple lasers together, and the anodes of each laser are independent of each other, while the cathodes of each laser are connected together and share a pin. Then, the packaged laser light source includes multiple anode pins and one cathode pin. When connecting a laser light source with this packaging method to an optical drive circuit, the multiple anode pins can be connected to a single optical drive circuit, while the cathode pin can be grounded nearby or connected to the output terminal of the power supply circuit 10. This wiring method is called common cathode drive.

[0140] The reason why the common cathode drive can shorten the transmission line of the drive current is as follows.

[0141] The reason why common cathode driving can shorten the transmission line of the driving current is that the anode of the laser 51 is already connected to the optical driving circuit 40. Then, the cathode of the laser 51 can be grounded nearby to form a closed loop where the driving current is located, thereby shortening the transmission line of the driving current.

[0142] For example, as shown in Figure 6, power supply circuit 10 and optical driver circuit 40 are integrated on a single board, which is labeled the power board. The drive current flows from the power board where power supply circuit 10 and optical driver circuit 40 are located, to laser 51, and then to ground GND. The dotted arrows in Figure 6 indicate the drive current transmission path, and the corresponding current loop area is labeled S2.

[0143] For example, Figure 7 shows a schematic diagram of a separate power supply circuit 10 and optical driver circuit 40. The optical driver circuit 40 can be placed near the laser 51. The drive current then flows from the optical driver circuit 40 to the laser 51 and then to the ground terminal GND. The dotted arrow in Figure 6 indicates the drive current transmission path, and the corresponding current loop area is denoted as S3.

[0144] According to FIG3 , FIG6 and FIG7 , it can be seen that the current loop area S1 is larger than the current loop area S2 and the current loop area S3.

[0145] 3 , the driving current in the common cathode driving mode flows directly into the ground terminal GND after passing through the laser 51, rather than into the optical driving circuit 40. This effectively reduces the current loop area of ​​the driving current.

[0146] Based on the above formula (1), it can be seen that when the current loop area of ​​the driving current is reduced, the electric field strength of the electromagnetic radiation interference electric field generated around the transmission line of the driving current will also be reduced. Accordingly, the impact of the electromagnetic waves radiated by the projection device on the components within the projection device and other electronic equipment around the projection device is also reduced.

[0147] As described above, the power supply circuit 10 and the at least one light driving circuit 40 in the projection device can be integrated on a single board, for example, can be provided on a power supply board.

[0148] Alternatively, the power supply circuit 10 and the plurality of optical drive circuits 40 may be separately provided. For example, the power supply circuit 10 is provided on a single board, which may be referred to as a power supply board, and the at least one optical drive circuit 40 is not provided on the power supply board but is provided on another single board, which may be referred to as a optical drive board.

[0149] As shown in Figures 6 and 7, if the power supply circuit 10 and at least one optical driving circuit 40 are integrated, then as shown in Figure 6, the transmission line where the driving current is located includes the transmission line between the power supply board where the driving circuit 40 is located and the laser 51, and the transmission line between the laser 51 and the ground terminal.

[0150] If the power supply circuit 10 and at least one optical drive circuit 40 are separately provided, as shown in FIG7 , the transmission line for the drive current includes the transmission line between the optical drive board where the drive circuit 40 is located and the laser 51, and the transmission line between the laser 51 and the ground terminal. As shown in FIG7 , the optical drive board where the optical drive circuit 40 is located is located between the power supply board and the laser 51. Therefore, compared with FIG6 , the transmission line for the drive current is further shortened.

[0151] It should be pointed out that only a high-frequency changing driving current (the current input to the laser 51) can generate strong electromagnetic waves. Therefore, as shown in Figure 7, the transmission line between the power board and the optical driving circuit 40 is used to provide the power supply voltage to the optical driving circuit 40. The transmitted current is relatively stable, and the electromagnetic waves generated are very weak and will not affect the device.

[0152] Therefore, when the power supply circuit 10 and the at least one optical driving circuit 40 are separately provided, the electromagnetic disturbance generated by the driving current is smaller than when the power supply circuit 10 and the at least one optical driving circuit 40 are integrated.

[0153] It can be seen that in the common cathode driving mode, since the driving current can flow directly into the ground terminal after passing through the laser without flowing back to the optical driving circuit, regardless of whether the power supply circuit 10 and at least one optical driving circuit are integrated or discrete, the electromagnetic interference generated by the driving current during the transmission process is often small.

[0154] Continuing to refer to Figures 6 and 7, the power board where the power circuit 10 is located and the laser light source 50 can be fixed to the metal bracket inside the projection device by screws and studs. The metal bracket inside the machine can be connected to the ground terminal, wherein the ground terminal can be the common ground terminal of the power board.

[0155] The common cathode drive can realize the power supply input voltage provided by the power supply circuit 10 to the light driving circuit 40 without limitation for the following reasons.

[0156] As shown in FIG8 , the cathode of the laser 51 may not be grounded, but may be connected to the line between the power supply circuit 10 and the optical driving circuit.

[0157] Thus, the potential of the cathode of the laser 51 is the power supply input voltage V provided by the power supply circuit 10. inThen, the voltage V loaded on the anode and cathode of the laser 51 is d V out and V in The difference, V d =V out -V in , and then, V out =V d +V in .

[0158] When the optical drive circuit 40 stops outputting the drive current to the laser, V d When the optical drive circuit 40 outputs the drive current to the laser, V d V′ d , so, V out ≥V in .

[0159] It should be pointed out that if V out and V in The relationship between V and V is used to determine whether the optical drive circuit is a boost circuit or a buck circuit. out Always greater than or equal to V in , then the light driving circuit is a boost circuit.

[0160] It can be seen that in order to make the voltage V d , is the rated driving voltage V' that causes it to emit light normally d , then the optical drive circuit only needs to supply input voltage V in , increase V′ d Therefore, the light driving circuit 40 supplies the power input voltage V in Increase V′ d , instead of rising to V′ d Therefore, regardless of the power supply input voltage V in No matter what value is selected, the light driving circuit can raise the output voltage V' d , so, when selecting the power supply input voltage V in When selecting, there is no need to use the minimum rated drive voltage as the basis.

[0161] Therefore, in the common cathode driving mode, the negative pole of the laser 51 is connected to the connection line between the power supply circuit 10 and the optical driving circuit 40, so that the selection of the power supply input voltage of the power supply circuit 10 is not limited by the rated driving voltage of each laser (the voltage required for normal light emission).

[0162] Since the selection of the power supply input voltage of the power supply circuit 10 is not limited by the rated driving voltage of each laser, then when selecting V inWhen the selected voltage is not the minimum rated drive voltage, the selection can be made based on neither the minimum rated drive voltage nor the maximum rated drive voltage. in There is a large difference between the maximum rated drive voltage and the minimum rated drive voltage.

[0163] For example, a voltage as high as possible can be selected within the voltage range that the components in each optical drive circuit can withstand. This is because, when the voltage is higher and the power is constant, the input current is smaller, and the smaller the input current, the smaller the line loss generated during transmission.

[0164] For example, taking the above-mentioned rated driving voltages of the red laser, blue laser and green laser as 8V, 15V and 18V respectively, the power supply input voltage V of the power supply circuit 10 can be set to in 12V, so compared with the cathode grounding of the laser 51, the connection method shown in FIG8 can reduce the power supply input voltage V in , and the difference between the rated driving voltage of each laser 51, thereby reducing the current or voltage input to some components in each optical driving circuit, so as to avoid component damage due to the large current or voltage input to the optical driving circuit.

[0165] Moreover, as shown in FIG8 , when the optical driving circuit 40 is short-circuited, the voltages at both ends of the laser 51 are equal and the voltage difference is zero. Therefore, the laser 51 will not be subjected to a large power supply input voltage, thereby preventing the laser 51 from being damaged when the optical driving circuit 40 is short-circuited.

[0166] The above is an introduction to the connection relationship between the power supply circuit 10, display control circuit 30, light driving circuit 40 and laser light source 50, as well as an introduction to the effects of the projection device. The specific circuits included in the light driving circuit 40 will be introduced below.

[0167] It should be pointed out that the optical driving circuit 40 introduced below is any one of at least one optical driving circuit 40. Since the optical driving circuit 40 is introduced, the drawings involved all illustrate an optical driving circuit 40 and a laser 51 connected to the optical driving circuit 40.

[0168] It should be pointed out that the cathode of the laser 51 in the accompanying drawings can be grounded to reduce electromagnetic interference, or it can be connected to the line between the power supply circuit 10 and the optical driving circuit 40 to ensure that the power input voltage provided by the power supply circuit 10 is not limited by the rated driving voltage of the laser 51.

[0169] FIG9 is a schematic diagram of an optical driving circuit provided by an embodiment of the present disclosure. Referring to FIG9 , the optical driving circuit 40 may include a control circuit 410 , a switch circuit 420 and a charge-discharge circuit 430 .

[0170] The switch circuit 420 has a control terminal, a first terminal, and a second terminal. As shown in FIG9 , the control circuit 410 is connected to the output terminal of the power supply circuit 10 and the control terminal of the switch circuit 420, respectively. In this way, the control circuit 410 can generate a switch drive signal (denoted as a Drv signal) based on the received dimming signal, and input the Drv signal to the control terminal of the switch circuit 420 to control the on-time and off-time of the first terminal and the second terminal of the switch circuit 420.

[0171] The Drv signal may also be referred to as a switch signal SW. The Drv signal may be a level signal including a first level and a second level. The first level is a high level, and the second level is a low level.

[0172] As an example, when the Drv signal is at a first level, the first and second terminals of the switch circuit 420 are connected, and when the Drv signal is at a second level, the first and second terminals of the switch circuit 420 are disconnected. It can be seen that the connection and disconnection of the switch circuit 420 are controlled by the Drv signal.

[0173] In one example, the switching circuit 420 is turned on and off to realize the charging and discharging of the charging and discharging circuit 430 . That is, the charging and discharging of the charging and discharging circuit 430 is controlled by the switching circuit 420 being turned on and off.

[0174] It should be pointed out that when the switch circuit 420 is turned on, whether the charge-discharge circuit 430 is in a charging state or a discharging state, and when the switch circuit 420 is disconnected and when the switch circuit 420 is turned on, whether the charge-discharge circuit 430 is in a charging state or a discharging state is related to the specific circuit of the light driving circuit 40.

[0175] Continuing to refer to FIG. 9 , the charge-discharge circuit 430 is connected to the corresponding laser 51 to provide a driving current to the laser 51 so that the laser 51 emits light under the action of the driving current.

[0176] For example, the charge and discharge circuit 430 is specifically used to continuously charge and discharge when the PWM signal in the dimming signal is at a high level, while the switch circuit 420 is continuously switched on and off, so as to provide a driving current to the connected laser 51, and to stop providing a driving current to the light source when the PWM signal in the dimming signal is at a low level.

[0177] It should be noted that the on-time and off-time of the switch circuit 420 are related to the duty cycle of the Drv signal. The duty cycle is the ratio of the power-on time to the total time within a pulse cycle. The duty cycle of the Drv signal is proportional to the Adim signal in the dimming signal. For example, the larger the Adim signal, the larger the duty cycle of the Drv signal (see Figure 15). Referring to the following formula, the larger the duty cycle of the Drv signal, the higher the power supply output voltage V of the charge and discharge circuit 430. out The larger the value, the greater the driving current provided by the charge and discharge circuit 430 to the laser 51.

[0178] As an example, when the Drv signal output by the control circuit 410 is at a first level, the first and second terminals of the switch circuit 420 are turned on. At this time, if the PWM signal in the dimming signal is at a high level, the power supply input voltage provided by the power supply circuit 10 can charge the charge-discharge circuit 430, and the charge-discharge circuit 430 can also output a driving current to the laser 51.

[0179] When the Drv signal output by the control circuit 410 is at the second level, the first terminal 1 and the second terminal 2 of the switch circuit 420 are turned off. At this time, if the PWM signal in the dimming signal is still at a high level, the charge-discharge circuit 430 is in a discharge state. Therefore, the charge-discharge circuit 430 can still output the driving current and still drive the laser 51 to emit light.

[0180] When the PWM signal in the dimming signal is at a low level, the control circuit 410 may or may not input the Drv signal to the switch circuit 420. When the control circuit 410 inputs the Drv signal to the switch circuit 420, regardless of whether the Drv signal is at the first level (high level) or the second level (low level), the charge-discharge circuit 430 will not provide a driving current to the laser 51. In this case, the laser 51 stops emitting light. In other words, when the PWM signal in the dimming signal is at a low level, regardless of whether the first and second terminals of the switch circuit 420 are in the on state or in the off state, the charge-discharge circuit 430 will not provide a driving current to the laser 51. In this case, the laser 51 stops emitting light.

[0181] In one example, the charge and discharge circuit 430 of the light source driving circuit 40 can provide a stable driving current to the laser 51. This can shorten the rise time and fall time of the driving current, for example, making the rise time and fall time of the driving current less than 20 microseconds (us).

[0182] Furthermore, by providing the charge and discharge circuit 430, the ripple current flowing into the laser can be reduced, thereby increasing the precision of the driving current flowing through the laser.

[0183] The electromagnetic interference generated during the transmission of the driving current is positively correlated with the magnitude of the ripple current. Therefore, by reducing the magnitude of the ripple current through the charge-discharge circuit 430, the electromagnetic interference generated during the transmission of the driving current can be further reduced.

[0184] Regarding the connection relationship between the power supply circuit 10, the switch circuit 420 and the charge-discharge circuit 430, there can be multiple layouts, two of which will be introduced below.

[0185] (1) A connection relationship among the power supply circuit 10 , the switch circuit 420 , and the charge and discharge circuit 430 .

[0186] As shown in FIG. 10 , a first end of the switch circuit 420 is connected to the power supply circuit 10 , and a second end of the switch circuit 420 is connected to the charge and discharge circuit 430 .

[0187] For example, as shown in FIG. 10 , the first terminal 1 of the control circuit 410 and the first terminal 1 of the switch circuit 420 are both connected to the output terminal of the power supply circuit 10 .

[0188] As an example, the first end 1 of the control circuit 410 and the first end 1 of the switching circuit 420 are both connected to the power interface of the optical driving circuit 40 (that is, the first end 1 of the optical driving circuit 40, which is also the power input end of the optical driving circuit 40), and the power interface of the optical driving circuit 40 is connected to the power connector of the power supply circuit 10 (that is, the output end of the power supply circuit 10).

[0189] Continuing with FIG10 , the second end of the control circuit 410 serves as the second end of the light driving circuit 40 and is connected to the display control circuit 30. Alternatively, the second end of the control circuit 410 and the second end of the light driving circuit 40 are independent of each other and are connected via a transmission line. Furthermore, the second end of the control circuit 410 is connected to the second end of the light driving circuit 40, and the second end of the light driving circuit 40 is connected to the display control circuit 30.

[0190] Continuing to refer to FIG. 10 , the third terminal 3 of the control circuit 410 is connected to the control terminal C of the switch circuit 420 to transmit the Drv signal to the switch circuit 420 .

[0191] (2) Another connection relationship among the power supply circuit 10, the switch circuit 420 and the charge and discharge circuit 430.

[0192] As shown in FIG. 11 , a first end of the switch circuit 420 is connected to the charge-discharge circuit 430 , a second end of the switch circuit 420 is grounded, and the charge-discharge circuit 430 is connected to the power supply circuit 10 .

[0193] The specific circuits of the light driving circuit 40 shown in FIG. 10 and the specific circuits of the light driving circuit 40 shown in FIG. 11 will be introduced below.

[0194] (1) The specific circuit of the light driving circuit 40 shown in FIG10 is as follows.

[0195] (1) Features of the switch circuit 420 of the light driving circuit 40 .

[0196] As shown in FIG. 12 , the switch circuit 420 may include a switch transistor Q1 .

[0197] The gate (Gate, G) of the switching transistor Q1 can serve as the control terminal C of the switching circuit 420, connected to the third terminal 3 of the control circuit 410, the first electrode of the switching transistor Q1 can serve as the first terminal of the switching circuit 420, connected to the power supply circuit 10, and the second electrode of the switching transistor Q1 can serve as the second terminal of the switching circuit 420, connected to the first terminal of the charging and discharging circuit 430.

[0198] Alternatively, the gate G of the switching transistor Q1 is connected to the control terminal C of the switching circuit 420, the first terminal of the switching transistor Q1 is connected to the first terminal of the switching circuit 420, and the second terminal of the switching transistor Q1 is connected to the second terminal of the switching circuit 420. In this way, the Drv signal transmitted by the control circuit 410 to the switching circuit 420 can also be input to the switching transistor Q1, causing the first and second terminals of the switching transistor Q1 to be turned on or off.

[0199] In one example, the switch transistor Q1 may be a P-type metal oxide semiconductor (MOS) transistor, wherein a first electrode of the switch transistor Q1 may be a source electrode (Source, S), and a second electrode of the switch transistor Q1 may be a drain electrode (Drain, D).

[0200] It can be understood that, referring to FIG15 (c1) and (d1), when the level of the gate G of the switching transistor Q1 is at the first level (high level), the voltage applied to the source S of the switching transistor Q1 by the power supply circuit 10 is higher than the voltage at the gate G. As a result, a negative voltage is formed between the gate G and the source S of the switching transistor Q1, and the absolute value of the negative voltage is greater than the threshold voltage of the switching transistor Q1, thereby turning on the source S and drain D of the switching transistor Q1.

[0201] Referring to Figures 15(c1) and (d1), when the voltage level of the gate G of the switching transistor Q1 is at the second level (low), the voltage applied to the source S of the switching transistor Q1 by the power supply circuit 10 is lower than the voltage at the gate G. The absolute value of the voltage between the gate G and the source S of the switching transistor Q1 is lower than the threshold voltage of the switching transistor Q1. As a result, the source S and drain D of the switching transistor Q1 are disconnected, and the switching transistor Q1 is in the off state.

[0202] Continuing to refer to FIG. 12 , the switch circuit 420 may further include: a first diode D1 , a first resistor R1 , and a second resistor R2 .

[0203] As shown in FIG12 , the first resistor R1 and the second resistor R2 are connected in parallel between the control circuit 410 and the control terminal of the switch circuit 420. Specifically, they can be connected in parallel between the control circuit 410 and the gate G of the transistor switch Q1. The first diode D1 is connected in series with the first resistor R1 or the second resistor R2, and the cathode of the first diode D1 is connected to the control circuit 410. For ease of description, as shown in FIG12 , the first diode D1 and the first resistor R1 can be used as an example for description.

[0204] For example, as shown in FIG12 , the cathode end of the first diode D1, serving as the control terminal C of the switch circuit 420, is connected to the third terminal 3 of the control circuit 410 and one end of the second resistor R2, respectively. The anode of the first diode D1 is connected to one end of the first resistor R1. The other end of the first resistor R1 and the other end of the second resistor R2 are both connected to the gate G of the switch transistor Q1.

[0205] Alternatively, the cathode of the first diode D1 is connected to the control terminal C of the switching circuit 420, the anode is connected in series with one end of the first resistor R1, the other end of the first resistor R1 is connected to the gate G of the switching transistor Q1, and one end of the second resistor R2 is connected to the control terminal C of the switching circuit 420, and the other end is connected to the gate G of the switching transistor Q1. In this way, the first resistor R1 and the second resistor R2 can be connected in parallel between the control circuit 410 and the gate G of the switching transistor Q1, and the first diode D1 is connected in series with the first resistor R1.

[0206] Regarding the first resistor R1 , the second resistor R2 and the first diode D1 being connected between the control circuit 410 and the gate G of the switching transistor Q1 , the effects achieved are as follows.

[0207] As shown in FIG12 , a circuit composed of a first resistor R1 , a second resistor R2 and a first diode D1 is connected between the control circuit 410 and the gate G of the switching transistor Q1 , which can slowly turn on the first and second electrodes of the switching transistor Q1 and quickly turn off the first and second electrodes.

[0208] This is because, when the current is being transmitted from the control circuit 410 to the switching transistor Q1, the line resistance is relatively large, significantly limiting the current on the line, causing the switching transistor Q1 to turn on slowly. However, when the current is being transmitted from the switching transistor Q1 to the control circuit 410, the line resistance is relatively small, weakening the current limiting effect on the line, causing the switching transistor Q1 to turn off quickly.

[0209] Among them, the first and second electrodes of the switching transistor Q1 are slowly turned on, which reduces the rate of change of the driving current, thereby reducing the intensity of the generated electromagnetic field, and the first and second electrodes of the switching transistor Q1 are quickly disconnected, which can reduce circuit losses. This is because, when the switching transistor Q1 is disconnected, the voltage drops, the power remains unchanged, and the current rises. The large current generates large losses, and the rapid disconnection can quickly cut off the current, thereby reducing circuit losses.

[0210] The impact on the driving current can be seen in (d1) in Figure 15. The rising slope of the driving current is smaller than the falling slope, where each falling start time point corresponds to the turn-on start time point of the switching transistor Q1.

[0211] Continuing with reference to FIG12 , the switching circuit 420 may further include a second capacitor C2, which is connected in parallel between the first and second electrodes of the switching transistor Q1, for example, between the S and D electrodes. For example, one capacitor plate of the second capacitor C2 is connected to the first electrode (e.g., the S electrode) of the switching transistor Q1, and the other capacitor plate of the first capacitor C1 is connected to the second electrode (e.g., the D electrode) of the switching transistor Q1.

[0212] The first capacitor C1 is used to stabilize the voltage between the first electrode and the second electrode of the switching transistor Q1.

[0213] The above are the features of the switch circuit 420 . The features of the charge and discharge circuit 430 will be described below.

[0214] (2) Features of the charge and discharge circuit 430 of the light driving circuit 40 .

[0215] As shown in Figure 12, the charge and discharge circuit 430 may include an inductor L and a second diode D2, one end of the inductor L and the cathode of the second diode D2 are both connected to the second end 2 of the switching circuit 420, the other end of the inductor L is connected to the first end 1 (i.e., the anode) of the laser 51, and the anode of the second diode D2 is connected to the ground terminal GND.

[0216] Since the second electrode of the switch transistor Q1 is connected to the second end of the switch circuit 420 , the inductor L and the cathode of the second diode D2 are both connected to the second electrode of the switch transistor Q1 .

[0217] (3) Features of the current detection circuit 440 of the light driving circuit 40 .

[0218] 13 , the optical driving circuit 40 may further include a current detection circuit 440 , which is connected in series with the laser 51 and the control circuit 410 to monitor the driving current of the laser 51 .

[0219] The current detection circuit 440 is used to enable the control circuit 410 to determine the driving current flowing through the laser 51. The control circuit 410 generates a switch driving signal Drv based on the dimming signal and the driving current determined by the current detection circuit 440 to control the on-time and off-time of the first terminal 1 and the second terminal 2 of the switch circuit 420.

[0220] For example, as shown in FIG. 13 , the current detection circuit 440 is connected between the power supply circuit 10 and the switch circuit 420 , and the current detection circuit 440 is connected to the control circuit 410 .

[0221] The control circuit 410 may obtain the potentials at both ends of the current detection circuit 440 , thereby determining the voltages at both ends of the current detection circuit 440 .

[0222] For example, as shown in FIG13 , a first terminal 1 of the current detection circuit 440 is connected to the output terminal of the power supply circuit 10, the power supply terminal Vin of the control circuit 410, and the first detection terminal Isen+ of the control circuit 410. A second terminal 2 of the current detection circuit 440 is connected to the first terminal 1 of the switch circuit 420 and the second detection terminal Isen- of the control circuit 410. In this way, the current detection circuit 440 can be connected in series with the laser 51, or its two ends can be connected to the control circuit 410.

[0223] The power supply terminal V of the control circuit 410 is in That is, the first terminal 1 of the control circuit 410 is used to be connected to the output terminal of the power supply circuit 10 .

[0224] In the disclosed embodiment, the control circuit 410 can sample the driving current flowing through the laser 51 through the current detection circuit 440 to obtain a current detection signal Isen. For example, the control circuit 410 can sample the potentials at the first and second terminals of the current detection circuit 440 to obtain a voltage across the current detection circuit 440. When the resistance in the current detection circuit 440 is constant, the current can be obtained from the voltage, and this current is the driving current.

[0225] Then, the control circuit 410 can control the on-time and off-time of the first terminal 1 and the second terminal 2 of the switch circuit 420 based on the relationship between the detected driving current and the rated driving current. The rated driving current is the current that drives the laser 51 to emit light normally.

[0226] For example, the current detection signal Isen is a current value, and the control circuit 410 can compare the determined current detection signal Isen with the rated drive current. The rated drive current is the current required for the laser to emit light. If the control circuit 410 determines that the current detection signal Isen is lower than the rated drive current, it can increase the duty cycle of the Drv signal output to the switch circuit 420, that is, increase the conduction time of the first terminal 1 and the second terminal 2 of the switch circuit 420 until the current detection signal Isen is equal to the rated drive current. In this way, the current value of the drive current flowing through the laser can be gradually increased, thereby allowing the light source to emit light normally.

[0227] If the control circuit 410 determines that the current detection signal Isen is higher than the rated drive current, it can reduce the duty cycle of the Drv signal output to the switch circuit 420, that is, reduce the conduction time of the first terminal 1 and the second terminal 2 of the switch circuit 420 until the current detection signal Isen is equal to the rated drive current.

[0228] Of course, the control circuit 410 can also control the on and off of the first terminal 1 and the second terminal 2 of the switch circuit 420 through the relationship between the voltage across the current detection circuit 440 and a preset threshold voltage of the current detection circuit 440 .

[0229] For example, the current detection signal Isen is a voltage value, and the control circuit 410 can compare the determined current detection signal Isen with a pre-stored voltage threshold. The voltage threshold can be the voltage value across the first terminal 1 and the second terminal 2 of the current detection circuit 440 when the current flowing through the current detection circuit 440 is the rated drive current of the laser. If the control circuit 410 determines that the current detection signal Isen is lower than the voltage threshold, it can increase the duty cycle of the Drv signal output to the switch circuit 420, that is, increase the conduction time of the first terminal 1 and the second terminal 2 of the switch circuit 420, until the current detection signal Isen is equal to the voltage threshold. In this way, the current value of the drive current flowing through the laser can be gradually increased, thereby allowing the light source to emit light normally.

[0230] If the control circuit 410 determines that the voltage value corresponding to the current detection signal Isen is higher than the voltage threshold, it can reduce the duty cycle of the Drv signal output to the switch circuit 420, that is, reduce the conduction time of the first terminal 1 and the second terminal 2 of the switch circuit 420 until the voltage value corresponding to the current detection signal Isen is equal to the voltage threshold.

[0231] As an example, as shown in FIG14 , the current detection circuit 440 includes a detection resistor Rsns, wherein the detection resistor Rsns is a sensitive resistor with a relatively small resistance value.

[0232] One end of the detection resistor Rsns serves as the first end 1 of the current detection circuit 440, and is connected to the output end of the power supply circuit 10 and the power supply end V of the control circuit 410. in , and the first detection terminal Isen+ of the control circuit 410. The other end of the detection resistor Rsns, as the second end 2 of the current detection circuit 440, is connected to the first end 1 of the switch circuit 420 and the second detection terminal Isen- of the control circuit 410 respectively.

[0233] Alternatively, one end of the detection resistor Rsns is connected to the first end of the current detection circuit 440, and the other end of the detection resistor Rsns is connected to the second end of the current detection circuit 440. In this way, the detection resistor Rsns and the laser 51 can be connected in series, and both ends of the detection resistor Rsns are connected to the control circuit 410.

[0234] It is understandable that by detecting the potentials of the first and second terminals of the detection resistor Rsns, the voltage of the detection resistor Rsns can be obtained, and then the relationship between the voltage value of the detection resistor Rsns and the voltage threshold can be determined.

[0235] It can also be understood that by detecting the potential of the first end and the second end of the detection resistor Rsns, and then based on the resistance value of the detection resistor Rsns, the current of the circuit where the detection resistor Rsns is located can be obtained by Ohm's law. The detection resistor Rsns is connected in series with the laser 51, and the relationship between the driving current of the laser 51 and its rated driving current can be determined.

[0236] It should be noted that if the control circuit 410 generates the Drv signal based on the relationship between the collected drive current and the rated drive current of the laser to control the on / off state of the switch circuit 420, then the current detection signal Isen described above is the collected drive current. If the control circuit 410 generates the Drv signal based on the relationship between the collected voltage across the detection resistor Rsns and a preset voltage threshold to control the on / off state of the switch circuit 420, then the current detection signal Isen described above can be the voltage threshold.

[0237] (4) Features of the voltage stabilizing circuit 450 of the light driving circuit 40 .

[0238] 14 , each light driving circuit 40 may further include a voltage stabilizing circuit 450 , wherein a first terminal of the voltage stabilizing circuit 450 is connected to the line between the power supply circuit 10 and the light driving circuit 40 , and a second terminal of the voltage stabilizing circuit 450 is grounded.

[0239] As shown in FIG14 , the voltage stabilizing circuit 450 may include at least one capacitor. The voltage stabilizing circuit 450 is used to stabilize the driving voltage output by the power supply circuit 10 to the light driving circuit 40. Therefore, the positive plate of the at least one capacitor is connected to the line between the output terminal of the power supply circuit 10 and the input terminal of the light driving circuit, and the negative plate of the at least one capacitor is grounded.

[0240] For example, as shown in FIG14 , an example is given including two capacitors, namely a third capacitor C3 and a fourth capacitor C4. The positive plates of the third capacitor C3 and the fourth capacitor C4 are both connected to the line between the output end of the power supply circuit 10 and the input end of the light driving circuit 40, and the cathode plates of the third capacitor C3 and the fourth capacitor C4 are both grounded.

[0241] For example, as shown in FIG14 with reference to FIG13 , one end of the fourth capacitor C4 and one end of the third capacitor C3 both serve as the first end 1 of the voltage stabilizing circuit 450 and are respectively connected to the output end of the power supply circuit 10, the power supply end of the control circuit 410, and the first end 1 of the switch circuit 420. The other end of the fourth capacitor C4 and the other end of the third capacitor C3 both serve as the second end 2 of the voltage stabilizing circuit 450 and are connected to the ground end GND.

[0242] Alternatively, one end of the fourth capacitor C1 and one end of the third capacitor C3 are both connected to the first end of the voltage stabilizing circuit 450, and the other end of the fourth capacitor C1 and the other end of the third capacitor C3 are both connected to the second end of the voltage stabilizing circuit 450. In this way, one end of the third capacitor C3 and the fourth capacitor C4 can be connected to the circuit of the power supply circuit 10 and the light driving circuit 40, and the other end can be grounded.

[0243] In the embodiment of the present disclosure, the fourth capacitor C4 and the third capacitor C3 can filter the driving voltage output by the power supply circuit 10 to the light driving circuit 40, so that the driving voltage output by the power supply circuit 10 is relatively stable, to ensure that the light driving circuit 40 can drive the light source to emit light within a certain driving voltage range.

[0244] (5) The enable signal Fault of the light driving circuit 40 .

[0245] The control circuit 410 in the light driving circuit 40 may further transmit an enable signal Fault to the power supply circuit 10. The power supply circuit 10 may output a driving voltage based on the enable signal Fault. When the enable signal Fault is at a high level, the power supply circuit 10 outputs the driving voltage to the light driving circuit 40. When the enable signal Fault is at a low level, the power supply circuit 10 stops outputting the driving voltage to the light driving circuit 40.

[0246] In the embodiment of the present disclosure, when the control circuit 410 determines that the light source has an open circuit or short circuit fault based on the current detection signal Isen, it can control the level of the enable signal Fault to be low. As a result, the power supply circuit 10 stops outputting the driving voltage, thereby protecting the light source.

[0247] For example, under normal circumstances, if the control circuit 410 detects a normal value of the current detection signal Isen, it can be determined that there is no abnormality in the optical drive circuit. In this case, the level of the enable signal Fault can be controlled to be high. However, if the control circuit 410 detects an abnormal value of the current detection signal Isen, such as being much larger than the rated drive current of the laser, it can be determined that there may be a short circuit in the optical drive circuit. For example, if the PWM signal is high but the current detection signal Isen is 0, it can be determined that there may be an open circuit in the optical drive circuit. In this case, the level of the enable signal Fault can be controlled to be low.

[0248] Based on the above, as shown in FIG14 , when the switch transistor Q1 of the switch circuit 420 is turned on and off, the current loop of the driving current is respectively as follows.

[0249] As shown in FIG14 , when the switching transistor Q1 is in the on state, the inductor L is in a charged state and slowly transmits the driving current transmitted by the switching transistor Q1 to the laser 51, thereby driving the laser 51 to emit light. At this time, the current loop of the driving current is: power supply circuit 10 - source S of the switching transistor Q1 - drain D of the switching transistor Q1 - inductor L - laser - ground terminal GND.

[0250] When the switching transistor Q1 is in the off state, the inductor L is in a discharging state. The inductor L, the laser 51, and the second diode D2 form a discharge loop, which continues to provide drive current to the laser 51, so that the laser 51 continues to emit light. At this time, the current loop of the drive current is: ground terminal GND - second diode D2 - inductor L - light source - ground terminal GND.

[0251] Based on the light driving circuit 420 shown in FIG. 14 , the relationship between the driving current and the dimming signal (including Adim and Pwm) and the Drv signal will be described below.

[0252] For example, see Figure 15. (a1) and (a2) in Figure 15 are schematic diagrams showing how the signal value (i.e., voltage value, in V) of the Adim signal in the dimming signal provided by the display control circuit 30 changes over time. (b1) and (b2) in Figure 15 are schematic diagrams showing how the duty cycle (in %) of the Pwm signal in the dimming signal provided by the display control circuit 30 changes over time. (c1) and (c2) in Figure 15 are schematic diagrams showing how the duty cycle of the Drv signal output by the control circuit 410 changes over time. (d1) and (d2) in Figure 15 are schematic diagrams showing how the current value of the driving current I flowing through the laser changes over time, where the unit of current is ampere (A).

[0253] Referring to (a1) and (d1) in FIG15 , it can be seen that the current value of the driving current in a certain period is positively correlated with the signal value of the Adim signal in the period. Therefore, as described above, the Adim signal is used to control the current value of the driving current.

[0254] Referring to (b1) and (d1) in FIG15 , it can be seen that during the period from t0 to t3, the duty cycle of the PWM signal is 100%, and the optical driving circuit 40 will continue to provide driving current to the laser 51, regardless of whether the switching circuit 420 is in the on state or in the off state.

[0255] Referring to (b2) and (d2) in FIG. 15 , it can be seen that during the period t0′ to t3′, the control circuit 410 still provides the switch drive signal Drv to the switch circuit 420. However, since the duty cycle of the PWM signal is 0 during the period t0′ to t3′, the light drive circuit 40 stops providing the drive current to the light source, and the drive current flowing through the light source is 0. Therefore, as described above, the PWM signal is used to control the presence or absence of the drive current.

[0256] Referring to (c1) and (d1) in FIG. 15 , it can be seen that during the period from t0′ to t3′, the larger the duty cycle of Drv, that is, the longer the on-time of the switch circuit 420 is, the larger the driving current is.

[0257] Referring to (c1) and (d1) in FIG. 15 , it can be seen that the frequency of change of the drive current corresponds to the signal frequency of the switch drive signal Drv. For example, a change cycle of the Drv signal includes a high level and a low level, and a change cycle of the drive current includes a rise and a fall. Therefore, when the Drv signal completes a change cycle, the drive current also completes a change cycle. Therefore, the change frequency of the drive current is consistent with the change frequency of the Drv signal, which is used to control the on and off of the switching transistor Q1. Therefore, as described above, the high-frequency on and off of the switch circuit 420 causes high-frequency changes in the drive current.

[0258] Referring to (d1) in FIG15 , it can be seen that the current value of the driving current flowing through the laser fluctuates in a sawtooth shape within a certain period of time. In the embodiment of the present disclosure, the average value of the current value within a certain period of time can be used to determine the driving current within the period of time. The average value can be the average value of the maximum current and the minimum current within the period of time. For example, as shown in (d1) in FIG15 , the driving current within the period of t0 to t1 is I0, the driving current within the period of t1 to t2 is I1, and the driving current within the period of t2 to t3 is I2.

[0259] The waveform of the driving current shown in (d1) in FIG. 15 may also be referred to as a driving current ripple.

[0260] (2) The specific circuit of the light driving circuit 40 shown in FIG11 is as follows.

[0261] (1) Features of the switch circuit 420 of the light driving circuit 40 .

[0262] As shown in FIG16 , the switch circuit 420 includes a switch transistor Q1 , a control terminal of the switch transistor Q1 is connected to the control circuit 410 , a first terminal of the switch transistor Q1 is connected to the charge and discharge circuit 430 , and a second terminal of the switch transistor Q1 is grounded.

[0263] Regarding the features of the switching transistor Q1 , please refer to the above description and will not be repeated here.

[0264] In an example, the switch circuit 420 may also include the first diode D1, the first resistor R1, and the second resistor R2 described above. Detailed descriptions can be found above and will not be repeated here.

[0265] In one example, the switch circuit 420 may also include the second capacitor C2 described above. The second capacitor C is connected in parallel between the first and second terminals of the switch circuit 420, and specifically, between the first and second terminals of the switch transistor Q1. For details, please refer to the above description and will not be repeated here.

[0266] (2) Features of the charge and discharge circuit 430 of the light driving circuit 40 .

[0267] As shown in FIG16 , the charge-discharge circuit 430 includes an inductor L, a second diode D2, and a first capacitor C1. One end of the inductor L is connected to the power supply circuit 10, and the other end is connected to the anode of the second diode D2. The cathode of the second diode D2 is connected to the cathode of the laser 51 corresponding to the optical drive circuit 40. The positive plate of the first capacitor C1 is connected to the cathode of the laser 51 corresponding to the optical drive circuit 40, and the negative plate of the first capacitor C1 is grounded.

[0268] The inductor L and the first capacitor C1 are both energy storage elements.

[0269] As described above, the first terminal of the switch circuit 420 is connected to the charge-discharge circuit 430. For example, as shown in FIG16 , the first terminal of the switch circuit 420 is connected to the line between the inductor L and the second diode D2. Alternatively, the first terminal of the switch circuit 420 may be connected to the line between the cathode of the second diode D2 and the sense resistor Rsns.

[0270] Thus, when the switching transistor Q1 is turned on, the power supply circuit 10 charges the inductor L. When the switching transistor Q1 is turned off, the inductor L discharges, providing a driving current to the laser 51. When the switching transistor Q1 is turned on again, the power supply circuit 10 again charges the inductor L. At this time, the first capacitor C1 discharges. The discharge loop is the driving current loop, i.e., first capacitor C1 - laser 51 - inductor L - switching transistor Q1 - ground. The first capacitor C1 provides a driving current to the laser 51. When the switching transistor Q1 is turned off again, the inductor L discharges again, providing a driving current to the laser 51. It can be seen that the charge-discharge circuit 430 provides a driving current to the laser 51 through the continuous charging and discharging of the inductor L and the first capacitor C1.

[0271] As mentioned above, the on-off state of the switching transistor Q1 is determined by the duty cycle of the Drv signal (denoted as D), and the larger the duty cycle D of the Drv signal is, the larger the driving current is. in and the power supply output voltage V out The following relationship is satisfied:

[0272] Then, if the cathode of the laser 51 is connected to the connection line between the power supply circuit 10 and the optical drive circuit 40, as described above, the voltage Vd loaded across the laser 51 satisfies the relationship: V d =V out -V in , then we can get the following formula.

[0273] It can be seen that when the duty cycle of the Drv signal is greater than 0.5, V d Greater than V in From the overall effect of the light driving circuit 40, the light driving circuit 40 is equivalent to a boost circuit (note that the judgment standard here is V d >V in ).

[0274] When the duty cycle is not greater than 0.5, V d Not greater than V in From the overall effect of the light driving circuit 40, the light driving circuit 40 is equivalent to a step-down circuit (note that the judgment standard here is V d ≤Vin ).

[0275] But the light driving circuit 40 itself is still V out ≥V in boost circuit.

[0276] For example, taking the laser projection device including a dual-color laser as an example, the rated driving current of the blue laser is 3A, and the corresponding rated driving voltage is 18V. The rated driving current of the red laser is 1.5A, and the corresponding rated driving voltage is 9V. Among them, the power supply input voltage V in Select 12V. Then, the control circuit 410 corresponding to the blue laser outputs a Drv signal with a duty cycle of 0.8, and the corresponding charge and discharge circuit 430 outputs a 30V power supply output voltage V out , to achieve the voltage rise at both ends of the laser. The control circuit 410 corresponding to the red laser outputs a Drv signal with a duty cycle of 0.3, and the corresponding charge and discharge circuit 430 outputs a 21V power supply output voltage V out , to achieve the voltage drop across the laser. The optical drive circuit 40 itself is still V out ≥V in boost circuit.

[0277] As can be seen from the above, this embodiment can control the voltage output by the optical drive circuit by controlling the duty cycle of the Drv signal, thereby controlling the voltage V across the laser. d Moreover, when the duty cycle is greater than 0.5, the voltage V across the laser is d , relative to the power supply input voltage V in Boost, and when the duty cycle of the Drv signal is not greater than 0.5, the voltage V across the laser is achieved d , relative to the power supply input voltage V in Therefore, this embodiment can achieve voltage boosting and voltage reduction across the laser based on different scenarios through the same type of optical drive circuit.

[0278] (3) Features of the current detection circuit 440 of the light driving circuit 40 .

[0279] As shown in Figure 16, the optical driving circuit 40 may also include a current detection circuit 440, wherein the current detection circuit 440 may also include a detection resistor Rsns as described above. For details, please refer to the above description and will not be repeated here.

[0280] (4) Features of the voltage stabilizing circuit 450 of the light driving circuit 40 .

[0281] In one example, the light driving circuit 40 may also include a voltage stabilizing circuit 450. As described above, the voltage stabilizing circuit 450 may include at least one capacitor, with the positive plate of each capacitor connected to the line between the power supply circuit 10 and the light driving circuit 40, and the negative plate of each capacitor connected to ground. For details, please refer to the above description and will not be repeated here.

[0282] It should be noted that the cathode of the laser 51 in FIG16 may also be grounded to shorten the transmission line of the driving current and reduce electromagnetic interference.

[0283] (5) The enable signal Fault of the light driving circuit 40 .

[0284] In the optical driving circuit 40 shown in FIG16 , the control circuit 410 may also send an enable signal to the power supply circuit 10 . For details, please refer to the above description and will not be repeated here.

[0285] As shown in Figure 17, a schematic diagram of the relationship between the frequency of the driving current and the electric field strength of the electromagnetic radiation disturbance electric field generated during transmission, as provided in the national standard GB / T 9254 (Limits and Methods of Measurement of Radio Disturbance for Information Technology Equipment) provided by an embodiment of the present disclosure. As shown in Figure 17, when the frequency of the driving current of a projection device is within the range of 30 megahertz (MHz) to 200 MHz, the electric field strength of the electromagnetic radiation disturbance electric field generated by the driving current of the projection device during transmission should be no greater than 40 millivolts (uV). When the frequency of the driving current of the projection device is within the range of 200 MHz to 1000 MHz, the electric field strength of the electromagnetic radiation disturbance electric field (i.e., radio disturbance) generated by the driving current of the projection device during transmission should be no greater than 47 millivolts (uV).

[0286] It can be understood that since the projection device provided in the embodiment of the present disclosure adopts common cathode drive, and the cathode of the laser is grounded, it can effectively reduce the transmission line of the driving current, thereby reducing the current loop area of ​​the driving circuit during the transmission process, thereby ensuring that the electromagnetic interference generated by the driving current during the transmission process meets the GB / T 9254 standard.

[0287] In this embodiment, the laser's anode is connected to the optical drive circuit, and its cathode is connected together. For example, the laser's cathode can be grounded. This grounding of the laser's cathode effectively shortens the transmission path through which the drive current flows, thereby reducing the current loop area of ​​the drive current. Furthermore, the impact of electromagnetic waves radiated by the projection device on the performance and operating status of components within the projection device and other electronic devices surrounding the projection device is reduced.

[0288] For another example, the cathode of the laser can be connected to the line between the power circuit and the optical drive circuit, so that the voltage V d , is the power supply output voltage V output by the optical drive circuit out , and the power supply input voltage V in Then, in order to promote the voltage V across the laser d Its rated driving voltage V′ d , you only need to control the light drive circuit to output V out , relative to the input Vin, increase V' d The voltage raised by the optical drive circuit is not affected by the input V in Influence, then, the power supply input voltage V output by the power supply circuit in , it is not limited by the rated drive voltage of the laser. in It is not easy for components to be burned out due to excessive input current, nor is it easy for components to be damaged due to excessive input voltage.

[0289] An embodiment of the present disclosure further provides a projection device, which, as described above, also includes a power supply circuit 10 , a display control circuit 30 , a laser light source 50 and at least one light driving circuit 40 , and the laser light source 50 includes at least one laser 51 .

[0290] The power supply circuit 10 and the at least one optical driving circuit 40 are arranged on different boards, and the optical driving board where the at least one optical driving circuit 40 is located is close to the laser light source 50 .

[0291] The power supply circuit 10 is connected to the display control circuit 30 and is used to supply power to the display control circuit 30 .

[0292] Regarding the features of the power supply circuit 10 and the display control circuit 30 , please refer to the above description and will not be repeated here.

[0293] The display control circuit 30 is connected to at least one light driving circuit 40 and is used to provide a dimming signal to the at least one light driving circuit 40. For details, please refer to the above description and will not be repeated here.

[0294] The light driving circuit 40 and the laser 51 are connected one to one, and is used to provide a driving current to the connected laser 51 based on the dimming signal, and the laser 51 is used to emit light under the driving current.

[0295] In one example, the projection device can be driven by a common anode or a common cathode. Accordingly, if driven by a common anode, the anode of the laser 51 is connected to the power supply circuit 10, and the cathode of the laser 51 is connected to the optical drive circuit 40. If driven by a common cathode, the anode of the laser 51 is connected to the optical drive circuit 40, and the cathode of the laser 51 can be grounded nearby. For details, please refer to the above description.

[0296] As described above, common cathode drive, and the power supply circuit 10 and the light driving circuit 40 are separately arranged, as shown in Figure 7, can shorten the transmission line of the driving current, thereby reducing the current loop area of ​​the driving current, thereby reducing the current loop area of ​​the driving current, and thus, the electromagnetic waves radiated by the projection device have a reduced impact on the devices inside the projection device and the performance and working status of other electronic equipment around the projection device.

[0297] In common anode drive, as shown in FIG18 , the optical drive board where the optical drive circuit 40 is located is located close to the laser light source. Therefore, the drive current flowing from the cathode of the laser 51 flows to the optical drive board, and the transmission path is obviously shorter than that flowing to the power supply board. Therefore, in the common anode drive scheme, the separate layout of the power supply circuit and the optical drive circuit can also shorten the transmission path of the drive current, thereby reducing the current loop area of ​​the drive current. Consequently, the impact of the electromagnetic waves radiated by the projection device on the performance and operating status of the components within the projection device and other electronic equipment surrounding the projection device is also reduced.

[0298] Regarding the features of the projection equipment, you can refer to the above description and will not go into details here.

[0299] FIG19 is a flow chart of a method for driving a laser of a projection device provided by an embodiment of the present disclosure, which method can be applied to the projection device described above. Referring to FIG19 , the method includes:

[0300] In step 101 , the power supply circuit 10 supplies power to the display control circuit 30 and at least one light driving circuit 40 .

[0301] The driving voltage provided by the power supply circuit to the light driving circuit may be a DC 24V.

[0302] In step 102 , the display control circuit 30 provides a dimming signal to at least one light driving circuit 40 .

[0303] The dimming signal includes a PWM signal and an Adim signal. The PWM signal is used to control the presence or absence of a driving current transmitted from the optical driving circuit to the laser, and the Adim signal is used to control the current value of the driving current.

[0304] In step 103 , the light driving circuit 40 provides a driving current to the connected laser 51 based on the dimming signal.

[0305] In the disclosed embodiment, each light driving circuit is capable of providing a driving current to the light source to which it is connected, driven by a driving voltage and based on a received dimming signal. The current value of the driving current may be positively correlated with the signal value of the Adim signal in the dimming signal. That is, the greater the signal value of the Adim signal, the greater the current value of the driving current. The frequency at which the driving current output by the light driving circuit is present or absent may be related to the duty cycle of the PWM signal in the dimming signal.

[0306] In step 104 , the laser 51 emits light under the driving current.

[0307] In the disclosed embodiment, the first ends of the multiple lasers may be anode (i.e., positive) ends, and the second ends may be cathode (i.e., negative) ends. Because the cathodes of the lasers are interconnected and the anodes are connected to the optical drive circuit, this driving method may also be referred to as common cathode drive.

[0308] In the common cathode drive mode, if the cathode of the laser is grounded, the drive current flowing out of the laser can flow to the reference ground nearby without returning to the power circuit or the optical drive circuit. Compared with the common anode drive mode, the transmission line of the drive current can be shortened, thereby effectively reducing the current loop area of ​​the drive current. Based on the above formula (1), it can be seen that when the current loop area of ​​the drive current is reduced, the electric field strength of the electromagnetic radiation interference electric field generated around the transmission line of the drive current will also be reduced. Accordingly, the electromagnetic waves radiated by the projection device will also have a reduced impact on the performance and working status of other electronic devices around the projection device.

[0309] For another example, the cathode of the laser can be connected to the line between the power circuit and the optical drive circuit, so that the voltage V d , is the power supply output voltage V output by the optical drive circuit out , and the power supply input voltage V in Then, in order to promote the voltage V across the laser d Its rated driving voltage V′ d , you only need to control the light drive circuit to output V out , relative to the input V in , increase V′ d The voltage raised by the optical drive circuit is not affected by the input V in Influence, then, the power supply input voltage V output by the power supply circuit in, it is not limited by the rated drive voltage of the laser. in It is not easy for components to be burned out due to excessive input current, nor is it easy for components to be damaged due to excessive input voltage.

[0310] FIG20 is a flow chart of another driving method provided by an embodiment of the present disclosure, which can be applied to a projection device. Referring to FIG20 , the method includes:

[0311] In step 201 , a power supply circuit provides a driving voltage to at least one light driving circuit.

[0312] In step 202 , the voltage stabilizing circuit stabilizes the driving voltage output by the power supply circuit.

[0313] In step 203 , the display control circuit provides a dimming signal to each light driving circuit.

[0314] In step 204 , the control circuit, under the drive of the driving voltage, controls the on / off state of the first terminal and the second terminal of the switch circuit according to the dimming signal transmitted by the display control circuit.

[0315] In step 205 , the charge and discharge circuit provides a driving current to the laser when the PWM signal of the dimming signal is at a high level, and stops providing the driving current to the laser when the PWM signal is at a low level.

[0316] In step 206 , the laser is driven by the driving current to emit light.

[0317] In step 207 , the current detection circuit detects the driving current flowing through the laser.

[0318] In step 208 , the control circuit controls the conduction time between the first terminal and the second terminal of the switch circuit according to the driving current.

[0319] It can be understood that the implementation process of each step in the above method embodiment can refer to the above related description and will not be repeated here.

[0320] It is also understandable that the order of the steps of the method for driving a light source provided by the embodiment of the present disclosure can be appropriately adjusted, and the steps can be increased or decreased accordingly according to the circumstances. For example, step 202 can be deleted according to the circumstances. Alternatively, steps 207 and 208 can be deleted according to the circumstances. Alternatively, steps 201 and 203 can be executed simultaneously. Any technician familiar with this technical field can easily think of a method of variation within the technical scope disclosed in this disclosure, and it should be covered by the scope of protection of this disclosure, so it will not be repeated here.

[0321] FIG21 is a schematic diagram of the hardware structure of the electronic device provided by the present disclosure. As shown in FIG21 , the electronic device 100 is used to implement the operation of the light driving circuit in any of the above-mentioned method embodiments. The electronic device 100 may include a memory 1001 and a processor 1002;

[0322] The memory 1001 is used to store computer programs.

[0323] The processor 1002 is configured to execute the computer program stored in the memory to implement the driving method in the above embodiment. For details, please refer to the relevant description in the above method embodiment.

[0324] Optionally, the memory 1001 may be independent or integrated with the processor 1002 .

[0325] When the memory 1001 is a device independent of the processor 1002 , the electronic device 100 may further include a bus 1003 for connecting the memory 1001 and the processor 1002 .

[0326] Optionally, this embodiment may further include a communication interface 1004, which may be connected to the processor 1002 via the bus 1003. The processor 1002 may control the communication interface 1003 to implement the above-mentioned receiving and sending functions of the electronic device 100.

[0327] An embodiment of the present disclosure provides a projection device, which includes: a memory, a processor and a computer program stored in the memory. When the processor executes the computer program, it implements the driving method provided in the above method embodiment (for example, the method shown in Figure 19 or Figure 20).

[0328] An embodiment of the present disclosure provides a computer-readable storage medium storing instructions, which are loaded and executed by a processor to implement the driving method provided in the above method embodiment (for example, the method shown in Figure 19 or Figure 20).

[0329] An embodiment of the present disclosure provides a computer program product containing instructions. When the computer program product is run on a computer, the computer is caused to execute the driving method provided in the above method embodiment (for example, the method shown in FIG. 19 or FIG. 20 ).

[0330] Those skilled in the art will understand that all or part of the steps to implement the above embodiments may be accomplished by hardware, or may be accomplished by a program to instruct the relevant hardware, and the program may be stored in a computer-readable storage medium, and the above-mentioned storage medium may be a read-only memory, a disk or an optical disk, etc.

[0331] It will be understood that the term "plurality" in the present disclosure means two or more.

[0332] In the present disclosure, the terms "first", "second", etc. are used to distinguish identical or similar items with substantially the same effects and functions. It should be understood that there is no logical or temporal dependency between "first", "second", and "nth", nor is there any limitation on the quantity and execution order.

[0333] 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 spirit and principles of the present disclosure shall be included in the scope of protection of the present disclosure.

Claims

1. A projection device, characterized in that: It includes a power supply circuit, a display control circuit, a laser light source and at least one light driving circuit, wherein the laser light source includes at least one laser; The power supply circuit is connected to the display control circuit and the at least one light driving circuit respectively, and is used to supply power to the display control circuit and the at least one light driving circuit; The display control circuit is connected to the at least one light driving circuit and is used to provide a dimming signal to the at least one light driving circuit; The optical driving circuit and the laser are connected one by one, and the optical driving circuit and the anode of the laser are connected, and the cathode of the at least one laser is interconnected; The optical driving circuit is used to provide a driving current to the connected laser based on the dimming signal, and the laser is used to emit light under the driving of the driving current.

2. The projection device according to claim 1, wherein: The cathode of the at least one laser is grounded.

3. The projection device according to claim 1, wherein: The cathode of the at least one laser is connected to the line between the power supply circuit and the optical driving circuit.

4. The projection device according to any one of claims 1 to 3, characterized in that: The optical drive circuit includes a control circuit, a switch circuit and a charge and discharge circuit; The switch circuit has a control end, a first end, and a second end. The control circuit is connected to the power circuit and the control end of the switch circuit, respectively, and is configured to generate a switch drive signal based on the dimming signal, and control the on-time and off-time of the first end and the second end of the switch circuit through the switch drive signal. The charging and discharging circuit is connected to the laser corresponding to the optical driving circuit, and is used to provide driving current to the laser corresponding to the optical driving circuit.

5. The projection device according to claim 4, characterized in that: The first end of the switch circuit is connected to the power supply circuit, and the second end is connected to the charge and discharge circuit.

6. The projection device according to claim 5, characterized in that The charging and discharging circuit includes an inductor and a second diode; One end of the inductor and the cathode of the second diode are both connected to the second end of the switch circuit, the other end of the inductor is connected to the laser corresponding to the optical drive circuit, and the anode of the second diode is grounded.

7. The projection device according to claim 4, characterized in that The switch circuit has a first end connected to the charge and discharge circuit and a second end connected to the ground. The charge and discharge circuit is connected to the power supply circuit.

8. The projection device according to claim 7, characterized in that The charging and discharging circuit includes an inductor, a second diode and a first capacitor; One end of the inductor is connected to the power supply circuit, and the other end is connected to the anode of the second diode, and the cathode of the second diode is connected to the laser corresponding to the optical drive circuit; The positive plate of the first capacitor is connected to the laser corresponding to the optical drive circuit, and the negative plate is grounded; The first end of the switch circuit is connected to the line between the inductor and the second diode.

9. The projection device according to claim 4, characterized in that The optical driving circuit further includes a current detection circuit, and the current detection circuit is connected to the laser corresponding to the optical driving circuit; The control circuit is connected to the current detection circuit and is configured to obtain a driving current of the corresponding laser through the current detection circuit, and generate a switch driving signal based on the dimming signal and the driving current.

10. The projection device according to claim 9, characterized in that The current detection circuit includes a detection resistor, the detection resistor and the laser corresponding to the optical driving circuit are connected in series, and both ends of the detection resistor are connected to the control circuit.

11. The projection device according to claim 4, characterized in that The switch circuit further includes a first resistor, a second resistor and a first diode; The first resistor and the second resistor are connected in parallel between the control circuit and the control terminal of the switch circuit (420); The cathode of the first diode is connected to the control circuit, and the anode is connected to the first resistor or the second resistor; The first resistor, the second resistor and the first diode are located in a circuit.

12. The projection device according to claim 4, characterized in that The light driving circuit further includes a voltage stabilizing circuit, and the voltage stabilizing circuit includes at least one capacitor; The positive plate of the at least one capacitor is connected to the line between the power supply circuit and the light driving circuit, and the negative plate is grounded.

13. The projection device according to claim 4, characterized in that The light driving circuit further includes a second capacitor connected in parallel between the first end and the second end of the switch circuit.

14. The projection device according to claim 1, wherein: The power supply circuit and the at least one light driving circuit are integrated together.

15. The projection device according to claim 1, wherein: The power supply circuit and the at least one optical driving circuit are arranged on different boards, and the optical driving board where the at least one optical driving circuit is located is close to the laser light source.

16. A projection device, characterized in that: A power supply circuit, a display control circuit, a laser light source and at least one light driving circuit, wherein the laser light source includes at least one laser; The power supply circuit and the at least one optical driving circuit are arranged on different boards, and the optical driving board where the at least one optical driving circuit is located is close to the laser light source; The power supply circuit is connected to the display control circuit and is used to supply power to the display control circuit; The display control circuit is connected to the at least one light driving circuit and is used to provide a dimming signal to the at least one light driving circuit; The optical driving circuit is connected to the laser one by one and is used to provide a driving current to the connected laser based on the dimming signal, and the laser is used to emit light under the driving current.

17. The projection device according to claim 16, wherein: The anode of the at least one laser (51) is connected to the power supply circuit, and the cathode is connected to the corresponding light driving circuit.

18. A method for driving a laser light source, characterized in that: Applied to the projection device according to any one of claims 1 to 17, the method comprises: The power supply circuit supplies power to the display control circuit and the at least one light driving circuit; The display control circuit provides a dimming signal to the at least one light driving circuit; The optical driving circuit provides a driving current to the connected laser based on the dimming signal; The laser emits light when driven by the driving current.

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