CN115437203B

CN115437203B - Projection device and driving method of light source thereof

Info

Publication number: CN115437203B
Application number: CN202211128274.XA
Authority: CN
Inventors: 陈许; 吴超
Original assignee: Qingdao Hisense Laser Display Co Ltd
Current assignee: Qingdao Hisense Laser Display Co Ltd
Priority date: 2022-09-16
Filing date: 2022-09-16
Publication date: 2024-10-11
Anticipated expiration: 2042-09-16
Also published as: CN115437203A

Abstract

The application discloses a projection device and a driving method of a light source thereof, wherein the projection device comprises a power circuit, the display control circuit comprises a plurality of light source driving circuits, a display control circuit and a plurality of light sources which are in one-to-one correspondence with the light source driving circuits. Each light source driving circuit can provide driving current for the light source connected with the light source driving circuit based on the light source driving signal provided by the display control circuit under the driving of the driving voltage provided by the power supply circuit so as to drive the light source to emit light. Since the second ends of the light sources are connected to the ground, the driving current flowing through the light sources can directly flow into the ground. Therefore, the current loop area of the driving current in the transmission process is smaller, so that the electromagnetic disturbance generated by the driving current in the transmission process is smaller, and the influence of electromagnetic waves radiated by the projection equipment on the working states and performances of the internal devices and other electronic equipment around the projection equipment is avoided.

Description

Projection device and driving method of light source thereof

Technical Field

The present application relates to the field of projection display technologies, and in particular, to a projection device and a driving method for a light source thereof.

Background

A laser projection device generally includes a light source driving circuit, a laser light source, a light valve, and a projection lens. The light source driving circuit is used for providing driving current for the laser light source so as to drive the laser light source to emit light. The light valve is used for modulating a laser beam emitted by the laser light source into an image beam, and the projection lens is used for projecting the image beam to the projection screen so as to realize the display of a projection image.

In the related art, the operating frequency of the light source driving circuit is high, the operating current is high, and the operating state of the light source driving circuit is periodically switched between on and off. The changing electric field generated by the switching of the working state generates a changing magnetic field, and the changing magnetic field further generates a changing electric field. The varying electric field and the varying magnetic field may generate electromagnetic waves, which may also be referred to as electromagnetic disturbances, capable of radiating outwards.

The electromagnetic wave radiated by the projection device should be lower than a certain limit value, otherwise, the electromagnetic wave is liable to affect the working state of the internal devices of the projection device and the working state of other electronic devices around the projection device, thereby damaging the performances of the internal devices and other electronic devices.

Disclosure of Invention

The application provides a projection device and a driving method of a light source thereof, which can solve the problem that electromagnetic waves radiated by the projection device in the related art have influence on the working states and performances of internal devices and other electronic devices. The technical scheme is as follows:

In one aspect, there is provided a projection device comprising: the display control circuit comprises a power supply circuit, a plurality of light source driving circuits, a display control circuit and a plurality of light sources which are in one-to-one correspondence with the light source driving circuits;

The output ends of the power supply circuits are respectively connected with the first ends of the light source driving circuits, and the power supply circuits are used for providing driving voltages for the light source driving circuits;

the display control circuit is respectively connected with the second ends of the light source driving circuits and is used for providing a light source driving number for each light source driving circuit;

The third end of each light source driving circuit is connected with the first end of a corresponding light source, and the light source driving circuits are used for providing driving current for the connected light source based on the light source driving signals under the driving of the driving voltages;

The second ends of the light sources are connected with the grounding end, and each light source is used for emitting light under the driving of the driving current.

In another aspect, a method for driving a light source of a projection apparatus is provided, the projection apparatus including a plurality of light sources, the projection apparatus further including a power supply circuit, a display control circuit, and a plurality of light source driving circuits connected in one-to-one correspondence with the plurality of light sources; the method comprises the following steps:

the power supply circuit supplies driving voltages to the plurality of light source driving circuits;

the display control circuit provides a light source driving signal to each of the light source driving circuits;

The light source driving circuit is driven by the driving voltage and provides driving current for the light source connected with the light source driving circuit based on the light source driving signal;

each of the light sources emits light under the drive of the driving current.

In yet another aspect, there is provided a projection apparatus including: the light source driving device comprises a memory, a processor and a computer program stored in the memory, wherein the processor realizes the light source driving method according to the aspect when executing the computer program.

In yet another aspect, a computer-readable storage medium having instructions stored therein that are loaded and executed by a processor to implement a method of driving a light source as described in the above aspect is provided.

In a further aspect, there is provided a computer program product containing instructions which, when run on a computer, cause the computer to perform the method of driving a light source as described in the above aspect.

The technical scheme provided by the application has the beneficial effects that at least:

The application provides a projection device and a driving method of a light source thereof, wherein the projection device comprises a power circuit, the display control circuit comprises a plurality of light source driving circuits, a display control circuit and a plurality of light sources which are in one-to-one correspondence with the light source driving circuits. Each light source driving circuit can provide driving current for the light source connected with the light source driving circuit based on the light source driving signal provided by the display control circuit under the driving of the driving voltage provided by the power supply circuit so as to drive the light source to emit light. Since the second ends of the light sources are connected to the ground, the driving current flowing through the light sources can directly flow into the ground. Therefore, the current loop area of the driving current in the transmission process can be ensured to be smaller, so that the electromagnetic disturbance generated by the driving current in the transmission process is ensured to be smaller, and the influence of electromagnetic waves radiated by the projection equipment on the working state and performance of internal devices and the working state and performance of other electronic equipment around the projection equipment is avoided.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic view of a projection apparatus according to an embodiment of the present application;

FIG. 2 is a schematic view of a structure of a projection apparatus in the related art;

FIG. 3 is a schematic view of another projection apparatus according to an embodiment of the present application;

fig. 4 is a schematic structural diagram of a light source driving circuit according to an embodiment of the present application;

FIG. 5 is a schematic diagram of a plurality of signals in a projection device according to an embodiment of the present application;

Fig. 6 is a schematic structural diagram of another light source driving circuit according to an embodiment of the present application;

Fig. 7 is a schematic structural diagram of a light source driving circuit according to another embodiment of the present application;

Fig. 8 is a schematic diagram of a structure of a light source driving circuit according to another embodiment of the present application;

fig. 9 is a schematic diagram of a power panel driving a light source to emit light according to an embodiment of the present application;

FIG. 10 is a schematic diagram of a radio disturbance limit corresponding to a frequency of a driving current according to an embodiment of the present application;

Fig. 11 is a flow chart of a driving method of a light source according to an embodiment of the present application;

Fig. 12 is a flowchart of another driving method of a light source according to an embodiment of the present application.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the present application more apparent, the embodiments of the present application will be described in further detail with reference to the accompanying drawings.

Fig. 1 is a schematic structural diagram of a projection device according to an embodiment of the present application. Referring to fig. 1, the projection apparatus may include: the device comprises a power circuit 10, a multimedia processing circuit 20, a display control circuit 30, a light source driving circuit 40, a light source assembly 50, an optical-mechanical assembly 60 and a projection lens 70.

Referring to fig. 1, the power supply circuit 10 is connected to a multimedia processing circuit 20, a display control circuit 30, and a light source driving circuit 40, respectively. The power supply circuit 10 is configured to supply an operating voltage to the multimedia processing circuit 20, the display control circuit 30, and the light source driving circuit 40, respectively. The power supply circuit 10 may output a dc voltage, for example, the power supply circuit 10 may output a dc voltage of 12 volts (V) or 24V.

With continued reference to fig. 1, the multimedia processing circuit 20 is connected to the display control circuit 30, and the multimedia processing circuit 20 is configured to receive video signals via various communication interfaces, such as a universal serial bus (universal serial bus, USB) interface, and process the video signals (e.g., brightness processing, sharpness processing, color processing, etc.). The multimedia processing circuit 20 may then transmit the processed video signal to the display control circuit 30. The multimedia processing circuit 20 may include a system on chip (SoC), among others.

The display control circuit 30 is capable of decoding and format converting the received video signal and further processing the video signal (e.g., geometry correction processing). The display control circuit 30 may then output the processed video signal to the opto-mechanical assembly 60. The display control circuit 30 is also capable of outputting a light source drive signal to the light source drive circuit 40 based on the video signal. The light source driving signal may include an Analog Dimming (ADIM) signal and a pulse width modulation (pulse width modulation, PWM) signal, among others.

The light source driving circuit 40 is configured to receive a light source driving signal and output a driving current to the light source assembly 50 based on the light source driving signal, so as to drive the light source in the light source assembly 50 to emit light. The PWM signal in the light source driving signal is used to control the presence or absence of the driving current transmitted to the light source assembly 50, and the ADIM signal in the light source driving signal is used to control the magnitude of the current value of the driving current. In an embodiment of the present application, the projection apparatus may include a plurality of light source driving circuits 40. The light source driving circuits 40 are connected to the light sources of the light source assembly 50 in a one-to-one correspondence.

In an embodiment of the present application, the light source assembly 50 may include a plurality of light sources, and the colors of the light beams emitted by the light sources may be the same or different. The light source in the light source assembly 50 may be a laser light source. For example, referring to fig. 1, each light source may include a plurality of lasers 51 in series. Accordingly, the projection device may be a laser projection device. Or the light source in the light source assembly 50 may be a light-emitting diode (LED) or other type of light source.

For example, referring to fig. 1, the projection apparatus may include a red light driving circuit 40_r, a green light driving circuit 40_g, and a blue light driving circuit 40_b. The light source assembly 50 may include a red light source 50_r, a green light source 50_g, and a blue light source 50_b. Each of the three light sources is connected to its corresponding one of the light source driving circuits 40. The three-color light sources can respectively emit red light, green light and blue light under the drive of the driving current. Based on the principle of synthesizing colors in optics, white light can be obtained by combining and homogenizing the three colors of light.

The opto-mechanical assembly 60 has integrated therein a digital micromirror device (digital micromirror devices, DMD) and a DMD driver circuit. The DMD driving circuit is used for driving the DMD to operate based on the video signal. The DMD is used to modulate the light beam emitted from the light source assembly 50 under the control of the DMD driver circuit to obtain the image to be projected for display. The projection lens 70 can enlarge the image to be projected and displayed, and project the image to be projected and displayed to the target object in a beam manner. The target object can be a projection screen or a wall surface.

Fig. 2 is a schematic view of a partial structure of a related art projection apparatus, and referring to fig. 2, a power supply circuit and a plurality of light source driving circuits may be integrally provided on a power panel of the projection apparatus. Or the power supply circuit may be provided on the power supply board, and the plurality of light source driving circuits are not provided on the power supply board, i.e., the plurality of light source driving circuits and the power supply circuit are separately provided.

As shown in fig. 2, the anodes (i.e., anodes) of the light sources and the light source driving circuits are connected to a power circuit, the cathode (i.e., negative terminal) of each light source is connected to a corresponding light source driving circuit, and each light source driving circuit is also connected to a ground terminal. In the process of driving the light source to emit light, the driving current flowing through the light source by each light source driving circuit may flow to: the positive pole of the power supply circuit, the light source driving circuit and the grounding end. The ground terminal may be a common ground terminal of the power panel. Thus, the transmission line of the driving current may form a loop (i.e. a current loop). Since the anodes of the plurality of light sources are directly connected to the power supply circuit, this light source driving method may also be referred to as a common anode light source driving.

It will be appreciated that when the drive current is changed, the magnetic and electric fields around the transmission line of the drive current are liable to be changed, which generates electromagnetic waves. The electromagnetic waves may also be referred to as electromagnetic interference (or noise). The faster the rate of change of the drive current, the wider the bandwidth of the noise. The larger the average value of the variation in the signal value of the driving current, the larger the amplitude of the noise.

In the transmission process of the driving current, the electric field strength E of the electromagnetic radiation disturbance electric field generated around the transmission line can be as follows:

Where f is the frequency of the driving current, a is the current loop area of the driving current, the unit of the current loop area may be square centimeter (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 may be milliamp (mA). r is the distance between the test antenna for testing the electric field strength E and the transmission line of the driving current. Alternatively, r may take a value of 3 meters.

Referring to the above formula (1), the electric field strength E is positively correlated with the current loop area A of the driving current, the current strength I of the driving current and the frequency f of the driving current. To ensure the projecting function of the projecting device, the frequency f of the driving current and the current intensity I of the driving current are fixed values. Therefore, the current loop area a of the driving current is a main factor affecting the current intensity E.

Referring to fig. 2, in the projection apparatus adopting the light source driving method of the common anode, the driving current is required to flow through the light source driving circuit connected to the light source after flowing through the light source, and finally flows into the ground terminal. Therefore, the current loop area of the driving current is also large. When the electromagnetic wave generated by the projection equipment exceeds a certain limit value, the working state and the performance of devices inside the projection equipment are influenced. For example, the electromagnetic waves may interfere with the operation state and performance of an infrared sensor in the projection device designed to protect the human eye from the proximity of the projection lens, with the operation state and performance of far-field speech circuitry in the projection device for recognizing the user's speech, and with the operation state and performance of audio output current in the projection device. In addition, electromagnetic waves radiated by the projection device can also influence the working states of other electronic devices around the projection device, so that the performances of the other electronic devices are damaged.

Fig. 3 is a schematic partial structure of a projection device according to an embodiment of the present application, and referring to fig. 3, the projection device may include: the display control circuit 30 includes a power supply circuit 10, a display control circuit 30, a plurality of light source driving circuits 40, and a plurality of light sources in one-to-one correspondence with the plurality of light source driving circuits 40.

The output terminals of the power supply circuit 10 are respectively connected to the first terminals 1 of the light source driving circuits 40, and the power supply circuit 10 is used for providing driving voltages to the light source driving circuits 40.

The display control circuit 30 is connected to the second terminals 2 of the plurality of light source driving circuits 40, respectively, and the display control circuit 30 is configured to provide a light source driving signal to each of the light source driving circuits 40. The light source driving signal may include an ADIM signal and a PWM signal.

The third terminal 3 of each light source driving circuit 40 is connected to the first terminal 1 of its corresponding one of the light sources, and each light source driving circuit 40 is configured to supply a driving current to the light source connected thereto based on a light source driving signal under the driving of the driving voltage. The second ends 2 of the plurality of light sources are all connected to the ground GND. Each light source is configured to emit light under the drive of a driving current.

Wherein the first ends 1 of the plurality of light sources may be anode (i.e., positive) ends and the second ends 2 may be cathode (i.e., negative) ends. Since the cathodes of the plurality of light sources are all connected to the ground GND, this light source driving method may also be referred to as a common cathode light source driving.

In the embodiment of the present application, each light source driving circuit 40 of the plurality of light source driving circuits 40 can adjust the magnitude of the current value of the driving current output by the light source driving circuit based on the ADIM signal in the received light source driving signal, and can control the presence or absence of the driving current output by the light source driving circuit based on the PWM signal in the light source driving signal.

Wherein the current value of the drive current may be positively correlated with the signal value of the ADIM signal. That is, as the signal value of the ADIM signal is larger, the current value of the driving current is larger. The frequency of the driving current output from the light source driving circuit 40 may be related to the duty ratio of the PWM signal. For example, if the duty ratio of the PWM signal is 50% in 1 second, the light source driving circuit 40 outputs the driving current for 0.5 seconds in 1 second, and does not output the driving current for the remaining 0.5 seconds.

In the common-cathode light source driving method, the driving current may flow as follows: power supply circuit 10-light source driving circuit 40-light source-ground GND. In the light source driving method of the common cathode, the driving current directly flows into the ground GND after flowing through the light source, rather than into the light source driving circuit 40, compared with the light source driving method of the common anode. This effectively reduces the current loop area of the drive current. Based on the above formula (1), when the current loop area of the driving current is reduced, the electric field strength of the electromagnetic radiation disturbance electric field generated around the transmission line of the driving current is also reduced. Accordingly, the electromagnetic waves radiated by the projection device have reduced effects on the performance and operating state of devices within the projection device and other electronic devices surrounding the projection device.

In summary, the embodiment of the application provides a projection device, which includes a power circuit, a plurality of light source driving circuits, a display control circuit, and a plurality of light sources corresponding to the light source driving circuits one by one. Each light source driving circuit can provide driving current for the light source connected with the light source driving circuit based on the light source driving signal provided by the display control circuit under the driving of the driving voltage provided by the power supply circuit so as to drive the light source to emit light. Since the second ends of the light sources are connected to the ground, the driving current flowing through the light sources can directly flow into the ground. Therefore, the current loop area of the driving current in the transmission process can be ensured to be smaller, so that the electromagnetic disturbance generated by the driving current in the transmission process is ensured to be smaller, and the influence of electromagnetic waves radiated by the projection equipment on the working state and performance of internal devices and the working state and performance of other electronic equipment around the projection equipment is avoided.

Alternatively, referring to fig. 3, the projection apparatus may include three light source driving circuits 40: a red light driving circuit 40_r, a green light driving circuit 40_g, a blue light driving circuit 40_b, and a red light source 50_r, a green light source 50_g, and a blue light source 50_b connected to the three light source driving circuits 40 in one-to-one correspondence. The driving voltage transmitted from the power circuit 10 to the three light source driving circuits 40 may be 24V.

As one possible example, the power supply circuit 10 and the plurality of light source driving circuits 40 in the projection apparatus may each be provided on a power supply board. That is, the power supply circuit 10 and the plurality of light source driving circuits 40 may be integrally provided.

As another possible example, the power supply circuit 10 is provided on a power supply board, and the plurality of light source driving circuits 40 are not provided on the power supply board. That is, the power supply circuit 10 and the plurality of light source driving circuits 40 may be separately provided.

It will be appreciated that when the power supply circuit 10 and the light source driving circuits 40 are integrally disposed, a relatively large number of relatively long connection lines (which may also be referred to as transmission lines) are required to be disposed inside the power panel to connect the power supply circuit 10 and the light source driving circuits 40. When the power supply circuit 10 and the light source driving circuits 40 are separately arranged, only a short connecting wire is required to connect the power panel and the light source driving circuits 40. As can be seen from this, the current loop area of the driving current when the power supply circuit 10 and the plurality of light source driving circuits 40 are separately provided is smaller than the current loop area of the driving current when the power supply circuit 10 and the plurality of light source driving circuits 40 are integrally provided. That is, the electromagnetic disturbance generated by the driving current when the power supply circuit 10 and the plurality of light source driving circuits 40 are separately provided is smaller than the electromagnetic disturbance generated by the driving current when the power supply circuit 10 and the plurality of light source driving circuits 40 are integrally provided.

It can be further understood that, in the light source driving mode of the common anode, since the driving current still needs to flow through the light source driving circuit after flowing through the light source, no matter the power source circuit and the plurality of light source driving circuits are integrated or separately arranged, the driving current also tends to generate larger electromagnetic disturbance in the transmission process. In the common-cathode light source driving mode, the driving current can directly flow into the grounding end after flowing through the light source, so that no matter the power supply circuit and the plurality of light source driving circuits are arranged in an integrated mode or in a discrete mode, the electromagnetic disturbance generated by the driving current in the transmission process is also small.

In the embodiment, the display control circuit 30 can output light source driving signals to the plurality of light source driving circuits 40 at the same time based on the received video signals. The display control circuit 30 may include a plurality of groups of ports for outputting the ADIM signal and the PWM signal, and each group of ports is connected to one light source driving circuit 40. For example, referring to fig. 3, the display control circuit 30 is capable of outputting Adim _r and pwm_r signals to the red light driving circuit 40_r, adim _g and pwm_g signals to the green light driving circuit 40_g, and Adim _b and pwm_b signals to the blue light driving circuit 40_b.

Fig. 4 is a schematic structural diagram of a light source driving circuit according to an embodiment of the present application, and referring to fig. 4, the light source driving circuit 40 may include: a control circuit 410, a switching circuit 420 and a charge-discharge circuit 430.

The first terminal 1 of the control circuit 410 and the first terminal 1 of the switch circuit 420 are connected to the power supply circuit 10 as the first terminal 1 of the light source driving circuit 40, the second terminal 2 of the control circuit 410 is connected to the display control circuit 30 as the second terminal 2 of the light source driving circuit 40, and the third terminal 3 of the control circuit 410 is connected to the control terminal C of the switch circuit 420. The second terminal 2 of the switching circuit 420 is connected to the first terminal 1 of the charge-discharge circuit 430.

The control circuit 410 is configured to control the on-off states of the first terminal 1 and the second terminal 2 of the switch circuit 420 according to the light source driving signal transmitted by the display control circuit 30 under the driving of the driving voltage provided by the power circuit 10.

The second terminal 2 of the charge/discharge circuit 430 is connected to the first terminal 1 of the light source as the third terminal 3 of the light source driving circuit 40. The charge and discharge circuit 430 is used to charge and supply a driving current to the light source when the switching circuit 420 is turned on, and discharge and stop the supply of the driving current to the light source when the switching circuit 420 is turned off.

In the embodiment of the present application, the control circuit 410 can output the switching signal SW to the switching circuit 420 after receiving the light source driving signal. The switching signal SW may be a level signal. When the switching signal SW output from the control circuit 410 is at the first level, the first terminal 1 and the second terminal 2 of the switching circuit 420 are turned on. At this time, the driving current supplied from the power supply circuit 10 can charge the charge/discharge circuit 430. A path can be formed between the power supply circuit 10 and the light source, and the light source can be driven to emit light by the driving current supplied from the power supply circuit 10.

When the switching signal SW output from the control circuit 410 is at the second level, the first terminal 1 and the second terminal 2 of the switching circuit 420 are turned off. At this time, the charge-discharge circuit 430 is in a discharge state, and a path cannot be formed between the power supply circuit 10 and the light source, and the driving current provided by the power supply circuit 10 cannot be transmitted to the light source, so that the light source stops emitting light.

It will be appreciated that by providing the charge and discharge circuit 430 in the light source driving circuit 40, a quick turn-on (i.e., supply of the driving current to the light source) and a quick turn-off (i.e., stop of the supply of the driving current to the light source) of the driving current can be achieved. Thus, the rise time and the fall time of the driving current can be made small, for example, both of them are made smaller than 20 microseconds (us). Further, by providing the charge/discharge circuit 430, the ripple current flowing into the light source can be made small, and the accuracy of the driving current flowing through the light source can be made high. The ripple current is the higher harmonic component in the driving current waveform.

It will also be appreciated that the electromagnetic disturbance generated during the drive current transfer is also positively correlated with the magnitude of the ripple current. Therefore, the magnitude of the ripple current is reduced by the charge/discharge circuit 430, and electromagnetic disturbance generated during the driving current transmission process can be further reduced.

The level of the driving voltage output by the power circuit and the second level may be both high level with respect to the first level, and the second level is greater than or equal to the level of the driving voltage.

For example, referring to fig. 5, (a 1) and (a 2) in fig. 5 are schematic diagrams of time variation of signal values (i.e., voltage values, in V) of ADIM signals in the light source driving signals provided by the display control circuit 30, (b 1) and (b 2) in fig. 5 are schematic diagrams of time variation of duty ratios (in%) of PWM signals in the light source driving signals provided by the display control circuit 30, and (c 1) and (c 2) in fig. 5 are schematic diagrams of time variation of duty ratios of the switching signals SW outputted by the control circuit 410, and (d 1) and (d 2) in fig. 5 are schematic diagrams of time variation of current values of the driving current I flowing through the light source. Wherein the unit of current is ampere (a).

Referring to fig. 5 (b 1) and (d 1), the duty ratio of the PWM signal is 100% in the period from t0 to t3, and the light source driving circuit 40 continuously supplies the driving current to the light source. Referring to (d 1) of fig. 5, it can be seen that the current value of the driving current flowing through the light source fluctuates in a zigzag shape for a certain period. In the embodiment of the application, the average value of the current values in a certain period can be used for determining the driving current in the period. Wherein the average value may be an average value of a maximum value and a minimum value of the current in the period. For example, as shown in (d 1) in fig. 5, the driving current in the period t0 to t1 is I0, the driving current in the period t1 to t2 is I1, and the driving current in the period t2 to t3 is I2. Referring to (a 1) and (d 1) in fig. 5, 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 certain period.

Referring to (c 1) and (d 1) of fig. 5, it can be seen that the frequency of the variation of the driving current corresponds to the signal frequency of the switching signal SW. For example, a period in which the driving current changes from I2 to i2+ corresponds to a period of high level of the switching signal SW, and a period in which the driving current changes from i2+ to I2-corresponds to a period in which the switching signal SW is low level. The waveform of the driving current shown in (d 1) of fig. 5 may be also referred to as a driving current ripple.

Referring to fig. 5 (b 2) and (d 2), the control circuit 410 still provides the switch signal SW to the switch circuit 420 during the period from t0 'to t 3'. However, since the duty ratio of the PWM signal is 0 in the period t0 'to t3', the light source driving circuit 40 stops supplying the driving current to the light source, and the value of the driving current flowing through the light source is 0.

Alternatively, as shown in fig. 6, the switching circuit 420 may include: and a switching transistor Q1.

The Gate (Gate, G) of the switching transistor Q1 is connected to the third terminal 3 of the control circuit 410 as the control terminal C of the switching circuit 420, the first pole of the switching transistor Q1 is connected to the power supply circuit 10 as the first terminal 1 of the switching circuit 420, and the second pole of the switching transistor Q1 is connected to the first terminal 1 of the charge/discharge circuit 430 as the second terminal 2 of the switching circuit 420.

Alternatively, the switching transistor Q1 may be a P-type metal oxide semiconductor (metal oxide semiconductor, MOS) transistor. The first pole of the switching transistor Q1 may be a Source (S), and the second pole of the switching transistor Q1 may be a Drain (Drain, D).

It will be appreciated that when the level of the gate G of the switching transistor Q1 is the first level, the power supply circuit 10 is loaded to the level at the source S of the switching transistor Q1, which is a high level compared to the first level at the gate G. Thus, a negative voltage can be 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, so that the source S and the drain D of the switching transistor Q1 are turned on.

When the level of the gate G of the switching transistor Q1 is the second level, the power supply circuit 10 loads the level at the source S of the switching transistor Q1 to be a low level compared to the second level at the gate G. The absolute value of the voltage between the gate G and the source S of the switching transistor Q1 is smaller than the threshold voltage of the switching transistor Q1. Thereby, the source S and the drain D of the switching transistor Q1 are turned off, and the switching transistor Q1 is in an off state.

With continued reference to fig. 6, the switching circuit 420 may further include: the first diode D1, the first resistor R1, the second resistor R2 and the first capacitor C1.

The cathode of the first diode D1 is connected to the third terminal 3 of the control circuit 410 and one end of the second resistor R2 as the control terminal C of the switching circuit 420, and 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 connected to the gate G of the switching transistor Q1. One end of the first capacitor C1 is connected to the first pole of the switching transistor Q1, and the other end of the first capacitor C1 is connected to the second pole of the switching transistor Q1.

In the embodiment of the present application, the switching signal SW output by the control circuit 410 may also be referred to as a pulse signal. The first diode D1 and the first resistor R1 may be used to absorb spikes in the pulse signal. Thus, electromagnetic radiation generated by the pulse signal during the switching process of the high level and the low level can be effectively reduced, so that the performance of each device in the light source driving circuit 40 is prevented from being damaged.

The second resistor R2 is used to reduce the switching speed of the high and low levels of the pulse signal (i.e., the speed at which the pulse signal is turned on or off), so that the pulse signal becomes a slowly rising, slowly falling pulse signal. This can prevent the switching transistor Q1 from rapidly changing between on and off states, and further prevent the performance of the switching transistor Q1 from being impaired.

The first capacitor C1 is used to stabilize the voltage between the first and second poles of the switching transistor Q1.

Optionally, referring to fig. 6, the charge and discharge circuit 430 may include: an inductance L and a second diode D2.

One end of the inductor L and the cathode of the second diode D2 are connected to the second end 2 of the switch circuit 420, the other end of the inductor L is connected to the first end 1 of the light source, and the anode of the second diode D2 is connected to the ground GND.

In the embodiment of the application, when the switching transistor Q1 is in the on state, the inductor L is in the charging state, and the driving current transmitted by the switching transistor Q1 is slowly transmitted to the light source to drive the light source to emit light. At this time, the current loop of the driving current is: the power circuit 10-the source of the switching transistor Q1-the drain D-the inductance L-the source-the ground GND of the switching transistor Q1.

When the switching transistor Q1 is in the off state, the inductor L is in a discharge state, and the inductor L, the light source, and the second diode D2 can form a discharge loop, so that the light source stops emitting light. At this time, the current loop of the driving current is: ground GND-second diode D2-inductance L-light source-ground GND.

Optionally, referring to fig. 7, each light source driving circuit 40 may further include: a current detection circuit 440.

The first terminal 1 of the current detection circuit 440 is connected to the output terminal of the power circuit 10, the power terminal Vin of the control circuit 410, and the first detection terminal isen+ of the control circuit 410, respectively, and the 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, respectively. The power source Vin of the control circuit 410 is the first terminal 1 of the control circuit 410.

The current detection circuit 440 is used to detect a driving current flowing through the light source. The control circuit 410 is further configured to control the on-time of the first terminal 1 and the second terminal 2 of the switch circuit 420 according to the driving current detected by the current detection circuit 440.

In an embodiment of the present application, the current detection circuit 440 can sample the driving current flowing through the light source to obtain the current detection signal Isen, and transmit the current detection signal Isen to the control circuit 410.

The control circuit 410 can compare a voltage value corresponding to the received current detection signal Isen with a voltage threshold value stored in advance. The voltage threshold may be a 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 driving current of the light source. If the control circuit 410 determines that the voltage value corresponding to the current detection signal Isen is lower than the voltage threshold, the duty ratio of the switching signal SW output to the switching circuit 420 may be increased, that is, the on-time of the first terminal 1 and the second terminal 2 of the switching circuit 420 may be increased until the voltage value corresponding to the current detection signal Isen is equal to the voltage threshold. Thus, the current value of the driving current flowing through the light source can be gradually increased, and the light source can emit light normally.

If the control circuit 410 determines that the voltage value corresponding to the current detection signal Isen is higher than the voltage threshold, the duty ratio of the switching signal SW output to the switching circuit 420 may be reduced, that is, the on-time of the first terminal 1 and the second terminal 2 of the switching circuit 420 may be reduced until the voltage value corresponding to the current detection signal Isen is equal to the voltage threshold. Thus, the current value of the driving current flowing through the light source can be reduced, and the light source can emit light normally.

Alternatively, as shown in fig. 8, the current detection circuit 440 includes: the resistance Rsns is detected. One end of the detection resistor Rsns is connected to the output end of the power supply circuit 10, the power supply end Vin of the control circuit 410, and the first detection end isen+ of the control circuit 410 as the first end 1 of the current detection circuit 440, respectively. The other end of the sense resistor Rsns is connected as a second end 2 of the current sense circuit 440 to the first end 1 of the switch circuit 420 and the second sense end Isen of the control circuit 410, respectively.

It will be appreciated that when the resistance value of the sense resistor Rsns is constant, the voltage across the sense resistor Rsns is proportional to the current flowing through the sense resistor Rsns. By detecting the current flowing through the detection resistor Rsns, the magnitude relation between the voltage value and the threshold voltage of the detection resistor Rsns can be determined.

Optionally, with continued reference to fig. 7, each light source driving circuit 40 may further include: a voltage stabilizing circuit 450. The first terminal 1 of the voltage stabilizing circuit 450 is connected to the output terminal of the power circuit 10, the power terminal Vin of the control circuit 410, and the first terminal 1 of the switching circuit 420, respectively, and the second terminal 2 of the voltage stabilizing circuit 450 is connected to the ground terminal GND. The voltage stabilizing circuit 450 is used for stabilizing the driving voltage outputted from the power supply circuit 10.

Alternatively, as shown in fig. 8, the voltage stabilizing circuit 440 includes: a second capacitor C2 and a third capacitor C3. One end of the second capacitor C2 and one end of the third capacitor C3 are respectively connected to the output terminal of the power circuit 10, the power terminal Vin of the control circuit 410, and the first end 1 of the switch circuit 420 as the first end 1 of the voltage stabilizing circuit 450. The other end of the second capacitor C2 and the other end of the third capacitor C3 are both connected to the ground GND as the second end 2 of the voltage stabilizing circuit 450.

In the embodiment of the present application, the second capacitor C2 and the third capacitor C3 can perform filtering processing on the driving voltage output by the power circuit 10, so that the driving voltage output by the power circuit 10 is relatively stable, so as to ensure that the light source driving circuit 40 can drive the light source to emit light within a certain driving voltage range.

Referring to fig. 7 and 8, the control circuit 410 in the light source driving circuit 40 may also 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 circuit 10 outputs a driving voltage. When the enable signal Fault is low, the power circuit 10 stops outputting the driving voltage.

In the embodiment of the application, the control circuit 410 may control the level of the enable signal Fault to be low if it is determined that the light source has an open circuit or a short circuit Fault based on the current detection signal Isen. Thereby, the power supply circuit 10 stops outputting the driving voltage, thereby functioning to protect the light source.

Fig. 9 (a) is a schematic diagram of a current loop of a driving current in a light source driving method of a common anode provided by the related art, and fig. 9 (b) is a schematic diagram of a current loop of a driving current in a light source driving method of a common cathode provided by an embodiment of the present application. It will be appreciated that the power supply circuit 10 and the light source driving circuits 40 according to the embodiments of the present application may be integrally disposed on the power panel of the projection apparatus. The power panel and the light source component can be fixed on an internal metal bracket of the projection equipment through screws and studs, and the internal metal bracket can be connected with a grounding end. The ground may be a common ground of the power strip.

As can be seen from comparing (a) and (b) in fig. 9, the current loop area S1 of the driving current in the light source driving mode of the common anode is larger than the current loop area S2 of the driving current in the light source driving mode of the common cathode. Based on the above formula (1), on the premise that the current value I of the driving current, the frequency f of the driving current, and the distance r between the test antenna and the driving current transmission line are fixed, the electric field intensity of the electromagnetic radiation disturbance electric field generated around the driving current transmission line in the common-cathode light source driving mode is smaller than the electric field intensity of the electromagnetic radiation disturbance electric field generated around the driving current transmission line in the common-anode light source driving mode.

Fig. 10 is a schematic diagram of a relationship between a frequency of a driving current and an electric field strength of an electromagnetic radiation disturbance electric field generated in a transmission process of the driving current in a national standard GB/T9254 (radio disturbance limit value and measurement method of an information technology device) provided by an embodiment of the present application. As can be seen from fig. 10, in the standard specified in GB/T9254, when the frequency of the driving current of the projection apparatus is in the range of 30 megahertz (MHz) to 200MHz, the electric field strength of the electromagnetic radiation disturbing electric field generated by the driving current of the projection apparatus during transmission should be not more than 40 millivolts (uV). When the frequency of the driving current of the projection device is in the range of 200MHz to 1000MHz, the electric field strength (i.e., radio disturbance) of the electromagnetic radiation disturbing electric field generated by the driving current of the projection device during transmission should be not more than 47 millivolts (uV).

It can be understood that, since the projection device provided by the embodiment of the application adopts the common cathode light source for driving, the current loop area of the driving current in the transmission process can be effectively reduced, so that the electromagnetic interference generated by the driving current in the transmission process can be ensured to meet the GB/T9254 standard.

Fig. 11 is a flowchart of a driving method of a light source of a projection device according to an embodiment of the present application, where the method may be applied to a projection device, for example, the projection device shown in fig. 1, 3, 4, 6, 7, or 8. The projection apparatus includes a plurality of light sources, as shown in fig. 3, and further includes a power supply circuit, a display control circuit, and a plurality of light source driving circuits connected in one-to-one correspondence with the plurality of light sources. Referring to fig. 11, the method includes:

Step 101, a power supply circuit supplies driving voltages to a plurality of light source driving circuits.

Wherein the driving voltage may be 24V.

Step 102, the display control circuit provides a light source driving signal to each light source driving circuit.

Wherein the light source driving signal includes a PWM signal and an ADIM signal. The PWM signal is used for controlling the existence of the driving current transmitted to the light source by the light source driving circuit, and the ADIM signal is used for controlling the magnitude of the current value of the driving current.

Step 103, the light source driving circuit provides driving current for the light source connected with the light source driving circuit based on the light source driving signal under the driving of the driving voltage.

In the embodiment of the application, each light source driving circuit can provide driving current for the light source connected with the light source driving circuit based on the received light source driving signal under the driving of the driving voltage. Wherein the current value of the driving current may be positively correlated with the signal value of the ADIM signal in the light source driving signal. That is, as the signal value of the ADIM signal is larger, the current value of the driving current is larger. The frequency of the driving current output by the light source driving circuit may be related to the duty ratio of the PWM signal in the light source driving signal.

Step 104, each light source emits light under the drive of the driving current.

In an embodiment of the present application, the first ends of the plurality of light sources may be anode (i.e., positive) ends and the second ends may be cathode (i.e., negative) ends. Since the cathodes of the plurality of light sources are all connected to the ground, this light source driving method may also be referred to as a common cathode light source driving method. In the common-cathode light source driving method, the driving current may flow as follows: the power supply circuit-the light source driving circuit-the light source-the ground terminal. Compared with the common anode light source driving mode, the driving current in the common cathode light source driving mode can directly flow into the grounding terminal after flowing through the light source, and can not flow into the light source driving circuit. This effectively reduces the current loop area of the drive current. Based on the above formula (1), when the current loop area of the driving current is reduced, the electric field strength of the electromagnetic radiation disturbance electric field generated around the transmission line of the driving current is also reduced. Accordingly, the electromagnetic waves radiated by the projection device have reduced influence on the performance and the operating state of other electronic devices around the projection device.

In summary, an embodiment of the present application provides a method for driving a light source of a projection apparatus, where the projection apparatus includes a power supply circuit, a plurality of light source driving circuits, a display control circuit, and a plurality of light sources corresponding to the plurality of light source driving circuits one by one. Each light source driving circuit can provide driving current for the light source connected with the light source driving circuit based on the light source driving signal provided by the display control circuit under the driving of the driving voltage provided by the power supply circuit so as to drive the light source to emit light. Since the second ends of the light sources are connected to the ground, the driving current flowing through the light sources can directly flow into the ground. Therefore, the current loop area of the driving current in the transmission process can be ensured to be smaller, so that the electromagnetic disturbance generated by the driving current in the transmission process is ensured to be smaller, and the influence of electromagnetic waves radiated by the projection equipment on the working state and performance of internal devices and the working state and performance of other electronic equipment around the projection equipment is avoided.

Fig. 12 is a flowchart of another method for driving a light source according to an embodiment of the present application, which can be applied to a projection device, for example, the projection device shown in fig. 1, 3,4, 6,7 or 8. The projection device includes a plurality of light sources. As shown in fig. 3, the projection apparatus further includes a power supply circuit, a display control circuit, and a plurality of light source driving circuits connected to the plurality of light sources in one-to-one correspondence. Referring to fig. 12, the method includes:

step 201, a power supply circuit provides driving voltages to a plurality of light source driving circuits.

Step 202, the voltage stabilizing circuit stabilizes the driving voltage output by the power supply circuit.

Step 203, the display control circuit provides a light source driving signal to each light source driving circuit.

Step 204, the control circuit controls the on-off state of the first end and the second end of the switch circuit according to the light source driving signal transmitted by the display control circuit under the driving of the driving voltage.

Step 205, the charge-discharge circuit charges when the switch circuit is turned on and supplies the driving current to the light source, and discharges when the switch circuit is turned off and stops supplying the driving current to the light source.

Step 206, each light source emits light under the driving of the driving current.

Step 207, the current detection circuit detects a driving current flowing through the light source.

Step 208, the control circuit controls the conducting time of the first end and the second end of the switch circuit according to the driving current.

It may be understood that the implementation process of each step in the above method embodiment may refer to the related description of each structure in the projection device in the foregoing apparatus embodiment, which is not repeated in the present embodiment.

It can be further understood that the sequence of the steps of the driving method of the light source provided by the embodiment of the application can be properly adjusted, and the steps can be correspondingly increased or decreased according to the situation. For example, step 202 may be deleted as appropriate. Or steps 207 and 208 may be deleted as appropriate. Or step 201 and step 203 may be performed simultaneously. Any method that can be easily conceived by those skilled in the art within the technical scope of the present disclosure should be covered in the protection scope of the present application, and thus will not be repeated.

An embodiment of the present application provides a projection apparatus including: the light source driving method provided in the above method embodiment (for example, the method shown in fig. 11 or fig. 12) is implemented when the processor executes the computer program.

Embodiments of the present application provide a computer-readable storage medium having instructions stored therein that are loaded and executed by a processor to implement a method of driving a light source (e.g., the method shown in fig. 11 or 12) as provided in the above-described method embodiments.

Embodiments of the present application provide a computer program product comprising instructions which, when run on a computer, cause the computer to perform a method of driving a light source (e.g. the method shown in fig. 11 or fig. 12) as provided by the method embodiments described above.

It will be understood by those skilled in the art that all or part of the steps for implementing the above embodiments may be implemented by hardware, or may be implemented by a program for instructing relevant hardware, where the program may be stored in a computer readable storage medium, and the above storage medium may be a read-only memory, a magnetic disk or an optical disk, etc.

It is understood that the term "plurality" in the present application means two or more.

The terms "first," "second," and the like in this disclosure are used for distinguishing between similar elements or items having substantially the same function and function, and it should be understood that there is no logical or chronological dependency between the terms "first," "second," and "n," and that there is no limitation on the amount and order of execution.

The foregoing description of the exemplary embodiments of the application is not intended to limit the application to the particular embodiments disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the application.

Claims

1. A projection device, the projection device comprising: the display control circuit comprises a power supply circuit, a plurality of light source driving circuits, a display control circuit and a plurality of light sources which are in one-to-one correspondence with the light source driving circuits;

The display control circuit is respectively connected with the second ends of the light source driving circuits and is used for providing light source driving signals for each light source driving circuit;

the second ends of the light sources are connected with the grounding end, and each light source is used for emitting light under the drive of the driving current;

Wherein, the first end of a plurality of light sources is positive pole, the second end of a plurality of light sources is negative pole, and every light source drive circuit includes: a control circuit, a switch circuit and a charge-discharge circuit;

the first end of the control circuit and the first end of the switch circuit are used as the first end of the light source driving circuit to be connected with the power supply circuit, the second end of the control circuit is used as the second end of the light source driving circuit to be connected with the display control circuit, the third end of the control circuit is connected with the control end of the switch circuit, and the second end of the switch circuit is connected with the first end of the charge-discharge circuit;

the control circuit is used for controlling the on-off states of the first end and the second end of the switch circuit according to the light source driving signal transmitted by the display control circuit under the driving of the driving voltage;

the second end of the charge-discharge circuit is used as a third end of the light source driving circuit and is connected with the first end of the light source, and the charge-discharge circuit is used for charging when the switch circuit is turned on and supplying the driving current to the light source, and discharging when the switch circuit is turned off and stopping supplying the driving current to the light source;

The charge-discharge circuit is also connected with the grounding end; when the switch circuit is turned on, the current loop of the driving current is: sequentially passing through the switch circuit, the charge-discharge circuit and the light source from the power circuit to the grounding end; when the switching circuit is turned off, the current loop of the driving current is: and the charging and discharging circuit and the light source are sequentially connected from the grounding end to the grounding end.

2. The projection device of claim 1, wherein the switching circuit comprises: a switching transistor;

The grid electrode of the switching transistor is used as the control end of the switching circuit to be connected with the third end of the control circuit, the first electrode of the switching transistor is used as the first end of the switching circuit to be connected with the power supply circuit, and the second electrode of the switching transistor is used as the second end of the switching circuit to be connected with the first end of the charge-discharge circuit.

3. The projection device of claim 2, wherein the switching circuit further comprises: the first diode, the first resistor, the second resistor and the first capacitor;

The cathode of the first diode is used as a control end of the switching circuit and is respectively connected with a third end of the control circuit and one end of the second resistor, and the anode of the first diode is connected with one end of the first resistor;

the other end of the first resistor and the other end of the second resistor are connected with the grid electrode of the switching transistor;

one end of the first capacitor is connected with the first pole of the switching transistor, and the other end of the first capacitor is connected with the second pole of the switching transistor.

4. The projection device of claim 1, wherein the charge-discharge circuit comprises: an inductor and a second diode;

One end of the inductor and the cathode of the second diode are connected with the second end of the switching circuit, the other end of the inductor is connected with the first end of the light source, and the anode of the second diode is connected with the grounding end.

5. The projection apparatus according to any one of claims 1 to 4, wherein each of the light source driving circuits further comprises: a current detection circuit;

the first end of the current detection circuit is respectively connected with the output end of the power circuit, the power end of the control circuit and the first detection end of the control circuit, the second end of the current detection circuit is respectively connected with the first end of the switch circuit and the second detection end of the control circuit, and the current detection circuit is used for detecting the driving current flowing through the light source, wherein the power end of the control circuit is the first end of the control circuit;

the control circuit is also used for controlling the conduction time of the first end and the second end of the switch circuit according to the driving current.

6. The projection device of claim 5, wherein the current detection circuit comprises: detecting a resistor;

one end of the detection resistor is used as a first end of the current detection circuit and is respectively connected with the output end of the power circuit, the power end of the control circuit and the first detection end of the control circuit;

the other end of the detection resistor is used as a second end of the current detection circuit and is respectively connected with the first end of the switch circuit and the second detection end of the control circuit.

7. The projection apparatus according to any one of claims 1 to 4, wherein the power supply circuit and the plurality of light source driving circuits are each provided on a power supply board.

8. The projection apparatus according to any one of claims 1 to 4, wherein the power supply circuit is provided separately from the plurality of light source driving circuits.

9. A driving method of a light source of a projection apparatus, characterized by being applied to the projection apparatus as claimed in any one of claims 1 to 8; the method comprises the following steps:

each of the light sources emits light under the drive of the driving current.