Current control circuit, method and projection device

Abstract

The embodiment of the present application provides a current control circuit, method and projection device, wherein the current control circuit is applied to a projection device including at least a light source and a color wheel, the circuit includes a main power circuit for connecting the light source; a discharge circuit connected to the main power circuit; and a control circuit connected to the main power circuit and the discharge circuit, the control circuit is used to control the main power circuit to pre-increase the voltage across the light source to a voltage value corresponding to the required drive current after switching during the spoke time of the color wheel when the drive current of the light source needs to be switched from small to large; and is used to reduce the voltage across the light source to a voltage value corresponding to the required drive current after switching through the discharge circuit during the spoke time of the color wheel when the drive current of the light source needs to be switched from large to small. The current control circuit provided in the embodiment of the present application can realize fast and stable switching of any current of the light source.

Description

Technical Field

[0001] The present application relates to the field of projection display technology, and in particular to a current control circuit, method and projection equipment. Background Art

[0002] The color wheel is an important device in the existing projection system. It is mainly used to receive the light from the light source and emit sequential light in sequence. Due to the differences in the light output requirements of different colors and the characteristics of the phosphors in different segmented areas of the color wheel, the light source has different current requirements in different segmented areas of the color wheel. When the light source switches between adjacent segmented areas of the color wheel, it needs to pass through the spoke area between the adjacent segmented areas of the color wheel. In order to avoid the mixing of the sequential light emitted by the color wheel in the spoke area, it is usually necessary to turn off the light source in the spoke area and turn it on again after the spoke area ends. Therefore, when the light source switches the current in different segmented areas of the color wheel, the current first drops to zero quickly, and then rises again to the required current value.

[0003] In the prior art, when the light source switches from a high current to a low current, a current overshoot often occurs at the moment the light source is turned on; and when the light source switches from a low current to a high current, the current rises too slowly after the light source is turned on. Therefore, the prior art needs to be improved. Summary of the invention

[0004] In view of the above problems, the embodiments of the present application provide a current control circuit, method and projection device, which can realize fast and stable switching of arbitrary current of a light source.

[0005] In a first aspect, an embodiment of the present application provides a current control circuit, which is applied to a projection device including at least a light source and a color wheel, and the circuit includes a main power circuit, a discharge circuit and a control circuit; wherein the main power circuit is used to connect the light source; the discharge circuit is connected to the main power circuit; the control circuit is connected to the main power circuit and the discharge circuit, and the control circuit is used to control the main power circuit to pre-increase the voltage across the light source to a voltage value corresponding to the required driving current after switching during the spoke time of the color wheel when the driving current of the light source needs to be switched from small to large; and is used to reduce the voltage across the light source to a voltage value corresponding to the required driving current after switching through the discharge circuit during the spoke time of the color wheel when the driving current of the light source needs to be switched from large to small.

[0006] In a second aspect, an embodiment of the present application provides a current control method, which is applied to a projection device including at least a light source and a color wheel. The current control method runs on the above-mentioned current control circuit to perform: when the driving current of the light source needs to be switched from small to large, during the spoke time of the color wheel, the main power circuit is controlled to pre-increase the voltage across the light source to a voltage value corresponding to the driving current required after the switching; and when the driving current of the light source needs to be switched from large to small, during the spoke time of the color wheel, the voltage across the light source is reduced to a voltage value corresponding to the driving current required after the switching through the discharge circuit.

[0007] In a third aspect, an embodiment of the present application provides a projection device, comprising a light source, a color wheel and a current control device; the color wheel is located in the optical path of the light source; the current control device is electrically connected to the light source to drive the power supply to emit light; wherein the current control device comprises a main power circuit, a discharge circuit and a control circuit; the main power circuit is connected to the light source; the discharge circuit is connected to the main power circuit; the control circuit is connected to the main power circuit and the discharge circuit, and the control circuit is used to control the main power circuit to pre-increase the voltage across the light source to a voltage value corresponding to the driving current required after switching during the spoke time of the color wheel when the driving current of the light source needs to be switched from small to large; when the driving current of the light source needs to be switched from large to small, the voltage across the light source is reduced to a voltage value corresponding to the driving current required after switching through the discharge circuit during the spoke time of the color wheel.

[0008] Compared with the prior art, the current control circuit, method and projection device provided in the embodiment of the present application are provided with a main power circuit, a discharge circuit and a control circuit. When the driving current of the light source needs to be switched from small to large, the control circuit controls the main power circuit to pre-increase the voltage at both ends of the light source to a voltage value corresponding to the driving current required after the switching during the spoke time of the color wheel, so that when the driving current of the light source is switched from a small current to a large current, the time from stopping to recovering is skipped at the moment when the light source is turned on, and the current of the light source can quickly rise to the driving current required after the switching. At the same time, when the driving current of the light source needs to be switched from large to small, the control circuit reduces the voltage at both ends of the light source to a voltage value corresponding to the driving current required after the switching during the spoke time of the color wheel, so that when the driving current of the light source is switched from a large current to a small current, at the moment when the light source is turned on, the two ends of the light source are not subjected to excessively high voltage, thereby suppressing current overshoot. Therefore, when the driving current of the light source switches between any current sizes, the steady state has been reached at the moment of turning on, thereby realizing fast and stable switching of any current.

[0009] These and other aspects of the present application will become more apparent from the description of the following embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0011] Figure 1 A projection system provided by an embodiment of the present application is shown.

[0012] Figure 2 Shows Figure 1 Schematic diagram of the color wheel structure in .

[0013] Figure 3 A block diagram of a current control circuit provided in an embodiment of the present application is shown.

[0014] Figure 4 A schematic structural diagram of a current control circuit provided in an embodiment of the present application is shown.

[0015] Figure 5 A structural schematic diagram of another current control circuit provided in an embodiment of the present application is shown.

[0016] Figure 6 A signal schematic diagram of system control quantity and state quantity in the current control circuit provided in an embodiment of the present application is shown.

[0017] Figure 7 A flow chart of a current control method provided in an embodiment of the present application is shown.

[0018] Figure 8 A schematic structural diagram of a projection device provided in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0019] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0020] In order to enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present application.

[0021] like Figure 1 As shown, Figure 1 A projection system 10 is schematically shown, and the projection system includes a light source control device 11, a light source 12, a color wheel driving device 13, a color wheel 14, a controller 15, a spatial light modulator 16, and a projection lens 17. The light source control device 11 is used to drive the light source 12 to emit light, the color wheel driving device 13 is used to drive the color wheel 14 to move, the color wheel 14 is used to receive the light emitted by the light source 12 and emit at least two color lights, the spatial light modulator 16 is used to perform image modulation on at least two color lights according to image data DATA to generate image light, and the projection lens 17 is used to perform projection according to the image light to display a projection image. The controller 15 is used to control the light source control device 11 to turn on and off the light source 12, the driving speed of the color wheel driving device 13, and the modulation timing of the spatial light modulator 16 so that the three are adapted to each other.

[0022] Specifically, the light source control device 11 is used to control the opening and closing of the light source 12, and the light source 12 is used to receive the driving signal sent by the light source control device 11 and emit light source light, such as blue light source light, and the light source can be a blue light source. In some embodiments, the light source 12 can also be a light source of other colors, not limited to a blue light source, such as a UV light source, thereby emitting UV light. Further, the light source 12 can be a semiconductor diode laser light source to provide high-brightness light source light.

[0023] The color wheel 14 is located on the light path of the light source light emitted by the light source 12. Figure 2As shown, the color wheel 14 includes at least two segmented areas A, at least one of the at least two segmented areas A carries a wavelength conversion material, at least two segmented areas A receive light from the light source and emit at least two colors of light correspondingly, at least one of the at least two colors of light is converted light generated by the wavelength conversion material being excited by the light from the light source, and each segmented area A emits one color of at least two colors of light. The color wheel driving device 13 is used to drive the color wheel 14 to move, so that at least two segmented areas A are periodically located on the light path where the light from the light source is located and correspondingly emit at least two colors of light periodically. In this embodiment, at least two segmented areas A are arranged along the circumferential direction, and the color wheel driving device 13 drives the color wheel 14 to rotate along the center of the color wheel 14, so that at least two segmented areas A are periodically located on the light path where the light from the light source is located, so that at least two segmented areas A periodically emit at least two colors of light. Due to the different brightness and light output requirements of each color, the driving current corresponding to the light source 12 in each segmented area A may be different. For example, the driving current corresponding to the light source 12 in the first segmented area a1 is the first driving current, and the driving current corresponding to the light source 12 in the second segmented area a2 is the second driving current. Therefore, when the light source 12 passes through different segmented areas A, the driving current may need to be adjusted, and the second driving current is the driving current required after adjustment.

[0024] The spoke area B is between two adjacent segmented areas A. When the light source 12 passes through two adjacent segmented areas A, it is bound to pass through the spoke area B. When the light source 12 passes through the spoke area B, the color wheel 14 emits mixed light of the colors corresponding to the two adjacent segmented areas A, that is, the spoke light. Generally speaking, in order to avoid the generation of spoke light, the light source 12 is turned off when the light source 12 passes through the spoke area B, so that the light source 12 does not emit light in the spoke area B. In other words, the light source 12 is turned off when entering the spoke area B and turned on when leaving the spoke area B.

[0025] When the light source 12 passes through two adjacent segmented areas A, the light source 12 is turned off when entering the spoke area A so that the driving current flowing through the light source 12 is zero. Since the driving currents corresponding to the light source 12 in different segmented areas A may be different, the driving current of the light source 12 may need to be readjusted after the light source 12 leaves the spoke area B to adapt to the light output requirements of the next segmented area A.

[0026] After rigorous testing, the inventors found that when a light source passes through two adjacent segmented areas, if the driving current corresponding to the previous segmented area is smaller than the driving current corresponding to the next segmented area, when the light source is turned on again after leaving the spoke area, the driving current of the light source rises too slowly; and if the driving current corresponding to the previous segmented area is larger than the driving current corresponding to the next segmented area, at the moment of leaving the spoke area and turning on the light source again, the voltage carried by both ends of the light source is too large, resulting in current overshoot.

[0027] In view of this problem, the inventor has conducted a lot of research and testing, and proposed a current control circuit in the present application, which can be applied to the above-mentioned projection system and solve the above-mentioned problem. The current control circuit in the present application is provided with a main power circuit, a discharge circuit and a control circuit. When the driving current of the light source needs to be switched from small to large, the control circuit controls the main power circuit to pre-increase the voltage at both ends of the light source to a voltage value corresponding to the driving current required after the switching during the spoke time of the color wheel, so that when the driving current of the light source is switched from a small current to a large current, the time from stopping to restoring is skipped at the moment when the light source is turned on, and the current of the light source can quickly rise to the driving current required after the switching. At the same time, when the driving current of the light source needs to be switched from large to small, the control circuit reduces the voltage at both ends of the light source to a voltage value corresponding to the driving current required after the switching during the spoke time of the color wheel, so that when the driving current of the light source is switched from a large current to a small current, at the moment when the light source is turned on, the two ends of the light source are not subjected to excessively high voltage, thereby suppressing current overshoot. Therefore, when the driving current of the light source is switched between any current values, a steady state is reached at the moment of switching on, thereby achieving fast and stable switching of any current.

[0028] Specifically, if Figure 3 As shown, Figure 3 A current control circuit 100 provided in an embodiment of the present application is shown. The current control circuit 100 specifically includes a main power circuit 110, a discharge circuit 120 and a control circuit 130. The discharge circuit 120 is connected to the main power circuit 110, and the control circuit 130 is connected to the main power circuit 110 and the discharge circuit 120. The main power circuit 110 is used to connect a light source, and the light source may be a semiconductor laser. The discharge circuit 120 is used to reduce the voltage across the light source. The control circuit 130 is used to control the timing of the main power circuit 110 switching on or off the light source and the discharge timing of the discharge circuit 120. The control circuit 130 is also used to control the main power circuit 110 to pre-increase the voltage across the light source to a voltage value corresponding to the required drive current after switching during the spoke time of the color wheel when the drive current of the light source needs to be switched from small to large; and to reduce the voltage across the light source to a voltage value corresponding to the required drive current after switching through the discharge circuit 120 during the spoke time of the color wheel when the drive current of the light source needs to be switched from large to small.

[0029] It should be noted that, in the embodiment of the present application, the period during which the light source passes through the color wheel segment area is called the segment time, and the period during which the light source passes through the color segment spoke area is called the spoke time. When the light source passes through two adjacent first segment areas and second segment areas, the light source needs to sequentially experience the first segment time, the spoke time, and the second segment time. The driving current required for the light source in the first segment time is the first driving current, and the driving current required for the light source in the second segment time is the second driving current. When the light source passes through two adjacent first segment areas and second segment areas, the first driving current needs to be switched to the second driving current, and the second driving current is the driving current required after the switching.

[0030] Assuming that the first driving current is less than the second driving current, when the light source changes from the first segment time to the second segment time, its driving current needs to switch from a small current to a large current, which also means that the driving current needs to increase. During the spoke time, the light source is turned off; after the spoke time ends, the light source is turned on again in the second segment time. In this embodiment, during the spoke time, the voltage across the light source is increased from the voltage value corresponding to the first driving current to the voltage value corresponding to the second driving current in advance, that is, before the light source is turned on, the voltage across the light source has already reached the voltage value corresponding to the second driving current required for the second segment time in advance, and the system enters the steady state in advance and is ready for the light source to be turned on, so that when the light source is turned on at the second segment time, the time for the system to resume work after the light source is turned on can be skipped, thereby accelerating the current rise speed of the light source and allowing the current of the light source to quickly reach the second driving current.

[0031] Assuming that the first driving current is greater than the second driving current, when the light source changes from the first segment time to the second segment time, its driving current needs to switch from a large current to a small current, which also means that the driving current needs to decrease. When entering the spoke time period, the light source is turned off; after the spoke time ends, the light source is turned on again when entering the second segment time. In this embodiment, when the light source is turned off and enters the spoke time period, the voltage across the light source is reduced to a voltage value corresponding to the second driving current. In other words, before the light source is turned on, the voltage across the light source has dropped to a voltage value corresponding to the second driving current required for the second segment time. The system enters a steady state in advance and is ready for the light source to be turned on, so that when the light source is turned on at the second segment time, the two ends of the light source will not be subjected to a high voltage corresponding to the first driving current, but a low voltage corresponding to the required second driving current, thereby suppressing current overshoot.

[0032] The current control circuit provided in the embodiment of the present application is provided with a main power circuit, a discharge circuit and a control circuit. When the driving current of the light source needs to be switched from small to large, the control circuit 100 controls the main power circuit 110 to pre-increase the voltage at both ends of the light source to a voltage value corresponding to the driving current required after the switching during the spoke time of the color wheel, so that when the driving current of the light source is switched from a small current to a large current, the time from stopping to recovering is skipped at the moment when the light source is turned on, and the current of the light source can quickly rise to the driving current required after the switching. At the same time, when the driving current of the light source needs to be switched from large to small, the control circuit 100 controls the voltage at both ends of the light source to a voltage value corresponding to the driving current required after the switching during the spoke time of the color wheel, so that when the driving current of the light source is switched from a large current to a small current, at the moment when the light source is turned on, the two ends of the light source are not subjected to excessively high voltage, thereby suppressing current overshoot. Therefore, when the driving current of the light source is switched between any current sizes, the steady state has been reached at the moment of turning on, thereby realizing fast and stable switching of any current.

[0033] In this embodiment, the main power circuit 110 may be a Buck circuit. In some implementations, the main power circuit 110 may also be a Boost circuit, etc. Specifically, Figure 4 As shown, Figure 4 One structure of the main power circuit 110 is shown. The main power circuit 110 includes a DC power source Source, a first switch S1, a second switch S2, a first capacitor C1, an inductor L1, and a freewheeling diode D1. One end of the first switch S1 is connected to the positive electrode of the DC power source Source, and the other end is used to connect to one end of the light source; one end of the inductor L1 is connected in series with the second switch S2 and then connected to the negative electrode of the DC power source Source, and the other end of the inductor L1 is used to connect to the other end of the light source; one end of the first capacitor C1 is connected between the first switch S1 and the positive electrode of the DC power source Source, and the other end is used to connect between the light source and the inductor L1; the positive electrode of the freewheeling diode D1 is connected between the inductor L1 and the second switch S2, and the negative electrode is connected between the first switch S1 and the positive electrode of the DC power source Source. Among them, the first capacitor C1 is connected in parallel to both ends of the light source, and the inductor L1 is connected in series with the light source.

[0034] like Figure 4 As shown, the discharge circuit 120 is connected in parallel with the first capacitor C1. The discharge circuit 120 includes a third switch S3, a first resistor R1 and a second capacitor C2; the first resistor R1 and the second capacitor C2 are respectively connected in parallel at both ends of the first capacitor C1, one end of the third switch S3 is connected to one end of the first capacitor C1, and the other end is connected between the first resistor R1 and the second capacitor C2.

[0035] In some embodiments, the structure of the discharge circuit 120 may also be as follows: Figure 5The discharge circuit 120 includes a third switch S3, a first resistor R1, a voltage zener diode Z1 and a second capacitor C2; the first resistor R1 and the voltage zener diode Z1 are connected in series and then connected in parallel at both ends of the first capacitor C1, the second capacitor C2 is connected in parallel at both ends of the first capacitor C1, one end of the third switch S3 is connected to one end of the first capacitor C1, and the other end is connected between the first resistor R1 and the second capacitor C2.

[0036] The first switch S1, the second switch S2 and the third switch S3 are all electronic switches. The first switch S1, the second switch S2 and the third switch S3 can be any one or more combinations of triodes, field effect transistors and thyristors.

[0037] In this embodiment, the control circuit 130 is connected to the first switch S1, the second switch S2 and the third switch S3. The control circuit 130 is used to output control signals to the first switch S1, the second switch S2 and the third switch S3 respectively to control the switching timing of the first switch S1, the second switch S2 and the third switch S3. Among them, the control circuit 130 controls the on and off of the light source by controlling the switching timing of the first switch S1. The control circuit 130 can be, but is not limited to, a clock chip, a pulse width modulation (PWM) chip, a single-chip microcomputer, etc., and the control signal can be a PWM signal, a clock signal, etc.

[0038] Furthermore, the main power circuit 110 includes a charging circuit connected to the light source. When the first driving current is less than the second driving current, the control circuit 130 is used to control the charging time of the charging circuit according to the driving current required after switching during the spoke time of the color wheel, and control the charging circuit to charge, so as to pre-increase the voltage across the light source to a voltage value corresponding to the driving current required after switching, and the driving current required after switching is also the second driving current. Specifically, since the voltage across the light source is in a certain relationship with the current, the charging time can be determined according to the first driving current before the increase and the second driving current after the increase, so that the voltage across the power supply increases from the voltage value corresponding to the first driving current to the voltage value corresponding to the second driving current after the charging time is reached.

[0039] In this embodiment, the charging circuit is composed of the first capacitor C1 and the inductor L1. In some embodiments, the charging circuit may not only include the first capacitor C1 and the inductor L1. The charging circuit of this embodiment adopts a closed-loop charging method. In some embodiments, the charging circuit may also adopt an open-loop charging method.

[0040] The control circuit 130 outputs a control signal to the second switch S2, and controls the charging time of the charging circuit by controlling the on-time and off-time of the second switch S2. Specifically, by controlling the on-time of the second switch S2, the first capacitor C1 and the inductor L1 are charged simultaneously. After the first capacitor C1 is charged to saturation, the off-time of the second switch is controlled to control the inductor L1 to discharge to the first capacitor C1, so that the voltage across the first capacitor C1 rises to the voltage corresponding to the second drive current, so that the voltage across the power supply reaches the voltage value corresponding to the second drive current in advance, and the system enters the steady state in advance. In some embodiments, the inductor current can also be controlled to be constant after the inductor L1 is discharged, so that the system reaches the steady state faster.

[0041] In addition, in this embodiment, the second switch S2 is controlled to be turned on or off by time control, so that the voltage across the light source reaches the voltage corresponding to the second driving current in advance. In some embodiments, the duty cycle of the control signal can be adjusted by pulse width modulation to control the on and off of the second switch S2. Alternatively, the on and off of the second switch S2 can be controlled by controlling the PWM frequency.

[0042] In this embodiment, the charging time of the charging circuit is calculated in real time according to the second driving current. In some embodiments, the charging time corresponding to the second driving current can be determined by looking up a table. Specifically, by testing to obtain the charging time corresponding to driving currents of different values, the charging time required to reach the second driving current can be determined by an offline table lookup.

[0043] Furthermore, when the first driving current is greater than the second driving current, the control circuit 130 is used to control the discharge time of the discharge circuit 120 according to the driving current required after switching when the light source is turned off, so as to reduce the voltage across the light source to a voltage value corresponding to the driving current required after switching, and the driving current required after switching is also the second driving current. Specifically, since the voltage across the light source is in a certain relationship with the current, the discharge time can be determined according to the first driving current before the drop and the second driving current after the drop, so that the voltage across the power supply drops from the voltage value corresponding to the first driving current to the voltage value corresponding to the second driving current after the discharge time is reached.

[0044] The control circuit 130 outputs a control signal to the third switch S3, and controls the discharge time of the discharge circuit 120 by controlling the conduction time of the third switch S3. Specifically, by controlling the conduction time of the third switch S3, the first capacitor C1 is discharged to the second capacitor C2, and then the voltage across the first capacitor C1 drops to a voltage corresponding to the second drive current, thereby causing the voltage across the light source to drop to a voltage value corresponding to the second drive current, and the system enters a steady state in advance.

[0045] In addition, in this embodiment, the third switch S3 is controlled to be turned on by time control, so that the voltage across the light source drops to a voltage value corresponding to the second driving current. In some embodiments, the duty cycle of the control signal can be adjusted by pulse width modulation to control the conduction of the third switch. Alternatively, the conduction and cutoff of the third switch S3 can be controlled by controlling the PWM frequency.

[0046] In this embodiment, the discharge time of the discharge circuit 120 is calculated in real time according to the second drive current. In some embodiments, the discharge time corresponding to the second drive current can be determined by looking up a table. Specifically, the discharge time corresponding to drive currents of different values ​​is obtained by testing, and the discharge time required to drop to the second drive current can be determined by an offline table lookup.

[0047] like Figure 6 As shown, Figure 6 The schematic diagram shows the changes of the control quantity (control signal) and the state quantity (the voltage of the first capacitor, the current of the inductor and the driving current of the light source) of the system over time when the light source switches to different segmented areas. Figure 4 and Figure 6 The principle of the embodiment of the present application is described below. It should be noted that the embodiment of the present application is described by taking the time control method of the control signal as an example, and in fact the control method of the control signal is not limited to this.

[0048] First of all Figure 6 The various signals shown are explained, the enable signal EN is the output enable signal of the light source driving current; the control signal S1 is the control signal output by the control circuit to control the first switch S1 to be turned on or off; the control signal S2 is the control signal output by the control circuit to control the second switch S2 to be turned on or off; the control signal S3 is the control signal output by the control circuit to control the third switch S3 to be turned on or off; the voltage signal C1 is the capacitor voltage signal of the first capacitor C1; the current signal L1 is the inductor current signal of the inductor L1; the current signal S1 is the current signal of the first switch S1. The current of the first switch S1 is equal to the driving current of the light source, so the current signal S1 can also be expressed as the driving current of the light source. In addition, the first switch S1, the second switch S2 and the third switch S3 in the embodiment of the present application take N-MOS as an example.

[0049] exist Figure 6In the color wheel, the light source sequentially passes through the first segmented area, the first spoke area, the second segmented area, the second spoke area and the third segmented area. And the second driving current corresponding to the second segmented area is greater than the first driving current corresponding to the first segmented area; the third driving current corresponding to the third segmented area is less than the second driving current corresponding to the second segmented area. In other words, when the light source switches from the first segmented area to the second segmented area, the driving current needs to increase; when the light source switches from the second segmented area to the third segmented area, the driving current needs to decrease.

[0050] At the initial time T0, the light source has left the first segmented area and is located in the first spoke area; at time T2, the light source leaves the first spoke area and enters the second segmented area; at time T3, the light source leaves the second segmented area and enters the second spoke area. That is to say, the stage T0 to T2 is the spoke time period; the stage T2 to T3 is the first segmented time period; and the stage T3 to T6 is also the spoke time period.

[0051] At time T0, the enable signal EN is at a high level, and the light source enters the light emitting preparation stage, and the control signal S2 is at a high level.

[0052] In the T0-T1 stage, the control signal S1 and the control signal S3 are at a low level, and the control signal S2 remains at a high level; in this stage, the first switch S1 is turned off, the second switch S2 is turned on, and the third switch S3 is turned off, and the light source is in an off state. In this stage, the DC power source Source charges the first capacitor C1 and the inductor L1 at the same time, and the voltage signal C1 and the current signal L1 rise at the same time. The voltage across the first capacitor C1 is equal to the voltage across the light source, that is, the voltage across the light source is rising in this stage.

[0053] At time T1, the control signal S2 changes to a low level, and the control signal S1 and the control signal S3 remain unchanged. The second switch S2 is turned off. At this time, since the first capacitor C1 has been fully charged, the voltage across the first capacitor C1 is equal to the power supply voltage, so the second switch 2 is turned off, and the inductor L1 continues to charge the first capacitor C1.

[0054] In the T1-T2 stage, the control signal S1, the control signal S2 and the control signal S3 remain at a low level, the inductor L1 continues to discharge to the first capacitor C1, and the voltage signal C1 continues to rise until it rises to the voltage corresponding to the second drive current, at which time the system voltage reaches a steady state. In fact, this stage is an additional boost value of the voltage of the first capacitor C1. If the voltage across the first capacitor C1 has risen to the voltage corresponding to the second drive current in the T0-T1 stage, then the system voltage can reach a steady state in the T0-T1 stage. In addition, the T0-T2 stage is a charging stage, so the time from T0 to T2 can be calculated based on the first drive current before the rise and the second drive current required to rise.

[0055] At time T2, the control signal S1 changes to a high level, the first switch S1 is turned on, and the light source is turned on. At this time, the light source leaves the spoke area of ​​the color wheel and enters the second segment area. Before the light source is turned on, since the voltage across the light source has already risen to the voltage value corresponding to the second drive current, it is ready for the light source to be turned on. At this moment when the light source is turned on, since the current of the light source is proportional to its voltage, the light source drive current can quickly rise to the current value corresponding to the second drive current, and the system current quickly enters the constant current closed-loop steady state.

[0056] In the T2-T3 stage, the control signal S1 maintains a high level, and the light source enters the second segment area and continues to emit light. At the same time, the control signal S2 controls the second switch S2 to turn on or off according to actual needs, and the voltage signal C1 and the current signal L1 are stable, so that the voltage at both ends of the light source and the driving current of the light source are kept stable. At the same time, the current signal S1 is constant, and the system is in a constant current closed-loop steady state.

[0057] At time T3, the enable signal EN becomes low level, the control signals S1 and S2 become low level, and the control signal S3 becomes high level. The first switch S1 is turned off, the second switch S2 is turned off, and the third switch S3 is turned on. At this time, the light source is turned off and leaves the second segment area of ​​the color wheel and enters the second spoke area.

[0058] In the T3-T4 stage, the control signal S1 and the control signal S2 are kept at a low level, and the control signal S3 is kept at a high level. In this stage, the inductor discharges to the first capacitor C1 and the second capacitor C2, and the first capacitor C1 discharges to the second capacitor C2, the current of the inductor L1 drops to zero and the voltage across the first capacitor C1 also continues to drop.

[0059] In the stage T4-T5, the control signal remains unchanged, the first capacitor C1 continues to discharge to the second capacitor C2, and the voltage across the first capacitor C1 continues to drop until it drops to a voltage value corresponding to the third driving current.

[0060] At time T5, the control signal S3 becomes low level, and the third switch S3 is turned off. At this time, the voltage across the first capacitor C1 drops to a voltage value corresponding to the third drive current, and the system voltage enters a steady state. It can be understood that the T3 to T5 stages are all discharge times, so the time from T3 to T5 can be calculated based on the second drive current before the drop and the third drive current to which it needs to drop.

[0061] In the T5-T6 stage, the control signal S1, the control signal S2 and the control signal S3 maintain a low level, the voltage across the first capacitor C1 remains unchanged, the system voltage remains steady, and waits for the light source to be turned on and enter the third segmented area. When the light source enters the third segmented area, at the moment of turning on, since the voltage across the light source has dropped to the voltage corresponding to the third drive current, the two ends of the light source will not withstand high voltage at this time, thereby suppressing the current overshoot when the light source is turned on. In fact, if the voltage across the first capacitor C1 has dropped to the voltage corresponding to the third drive current in the T4-T5 stage, the system can enter the steady state in advance. In addition, if the third drive current is the same as the second drive current, then the first capacitor C1 can be discharged without controlling it in the T3-T4 stage, so that the voltage across the first capacitor C1 remains unchanged, and the system directly enters the steady state.

[0062] In summary, when the light source passes through adjacent segmented areas of the color wheel, if the driving current needs to rise, the voltage across the light source is pre-raised to a voltage value corresponding to the required driving current during the spoke time, so that the current rises rapidly at the moment the light source is turned on, and the system quickly reaches a steady state; if the driving current needs to drop, the voltage across the light source is dropped to a voltage value corresponding to the required driving current during the spoke time, so that the current overshoot is suppressed at the moment the light source is turned on. Therefore, no matter how much the driving current before and after the light source is switched between segmented areas, it can be switched quickly and stably, and any segmented current can be quickly and stably controlled. Based on this, the segmented currents can differ more, thereby reducing the constraints on the angle ratios of the various colors of the color wheel, and the system deviation of the white balance can be corrected by the segmented current, thereby improving the yield of the product and achieving a better display effect.

[0063] The current control circuit provided in the embodiment of the present application is provided with a main power circuit, a discharge circuit and a control circuit. When the driving current of the light source needs to be switched from small to large, the control circuit controls the main power circuit to pre-increase the voltage at both ends of the light source to a voltage value corresponding to the driving current required after the switching during the spoke time of the color wheel, so that when the driving current of the light source is switched from a small current to a large current, the time from stopping to recovering is skipped at the moment when the light source is turned on, and the current of the light source can quickly rise to the driving current required after the switching. At the same time, when the driving current of the light source needs to be switched from large to small, the control circuit reduces the voltage at both ends of the light source to a voltage value corresponding to the driving current required after the switching during the spoke time of the color wheel, so that when the driving current of the light source is switched from a large current to a small current, at the moment when the light source is turned on, the two ends of the light source are not subjected to excessively high voltage, thereby suppressing current overshoot. Therefore, when the driving current of the light source is switched between any current sizes, the steady state has been reached at the moment of turning on, thereby realizing fast and stable switching of any current.

[0064] like Figure 7As shown, the embodiment of the present application further provides a current control method 200, which is applicable to the above-mentioned projection system 10, and the method 200 runs the above-mentioned current control circuit. The method 200 may include the following steps S210 to S220.

[0065] Step S210: when the driving current of the light source needs to be switched from small to large, during the spoke time of the color wheel, the main power circuit is controlled to pre-increase the voltage across the light source to a voltage value corresponding to the driving current required after the switching.

[0066] When the light source passes through adjacent segmented areas of the color wheel, if the driving current needs to increase, the voltage across the light source is pre-increased to a voltage value corresponding to the driving current required after switching during the spoke time, so that the current rises rapidly at the moment the light source is turned on, and the system quickly reaches a steady state.

[0067] Step S220: when the driving current of the light source needs to be switched from large to small, during the spoke time of the color wheel, the voltage across the light source is reduced to a voltage value corresponding to the driving current required after the switching through the discharge circuit.

[0068] When the light source passes through adjacent segmented areas of the color wheel, if the driving current needs to be reduced, the voltage across the light source is reduced to a voltage value corresponding to the driving current required after switching during the spoke time, thereby suppressing current overshoot at the moment the light source is turned on.

[0069] The current control method provided by the embodiment of the present application controls the main power circuit to pre-increase the voltage at both ends of the light source to a voltage value corresponding to the driving current required after the switching during the spoke time of the color wheel when the driving current of the light source needs to be switched from small to large, so that when the driving current of the light source is switched from small current to large current, the time from stopping to recovering is skipped at the moment the light source is turned on, and the current of the light source can quickly rise to the driving current required after the switching. At the same time, when the driving current of the light source needs to be switched from large to small, the voltage at both ends of the light source is reduced to a voltage value corresponding to the driving current required after the switching through the discharge circuit during the spoke time of the color wheel, so that when the driving current of the light source is switched from large current to small current, at the moment the light source is turned on, the two ends of the light source are not subjected to excessively high voltage, thereby suppressing current overshoot. Therefore, when the driving current of the light source switches between any current sizes, the steady state is reached at the moment of turning on, thereby realizing fast and stable switching of any current.

[0070] like Figure 8 As shown, the embodiment of the present application also provides a projection device 300, which includes a light source 310, a color wheel 320 and a current control device 330. The color wheel 320 is arranged on the light path of the light source 310, and the current control device 330 is electrically connected to the light source 310 to control the light source 310 to emit light.

[0071] Among them, the current control device includes the above-mentioned current control circuit; the main power circuit is connected to the light source; the control circuit is used to control the main power circuit to pre-increase the voltage across the light source to a voltage value corresponding to the driving current required after switching during the spoke time of the color wheel when the driving current of the light source needs to be switched from small to large; when the driving current of the light source needs to be switched from large to small, the voltage across the light source is reduced to a voltage value corresponding to the driving current required after switching through the discharge circuit during the spoke time of the color wheel.

[0072] The projection device provided by the embodiment of the present application is provided with a main power circuit, a discharge circuit and a control circuit. When the driving current of the light source needs to be switched from small to large, the control circuit controls the main power circuit to pre-increase the voltage at both ends of the light source to a voltage value corresponding to the driving current required after the switching during the spoke time of the color wheel, so that when the driving current of the light source is switched from a small current to a large current, the time from stopping to recovering is skipped at the moment when the light source is turned on, and the current of the light source can quickly rise to the driving current required after the switching. At the same time, when the driving current of the light source needs to be switched from large to small, the control circuit reduces the voltage at both ends of the light source to a voltage value corresponding to the driving current required after the switching during the spoke time of the color wheel, so that when the driving current of the light source is switched from a large current to a small current, at the moment when the light source is turned on, the two ends of the light source are not subjected to excessively high voltage, thereby suppressing current overshoot. Therefore, when the driving current of the light source switches between any current sizes, the steady state has been reached at the moment of turning on, thereby realizing fast and stable switching of any current. As a result, the difference between the segmented currents can be larger, thereby reducing the constraints on the angle ratios of the colors on the color wheel, and being able to correct the system deviation of the white balance through the segmented currents, thereby improving the product yield and achieving better display effects.

[0073] The above is only a preferred embodiment of the present application and does not constitute any form of limitation to the present application. Although the present application has been disclosed as a preferred embodiment as above, it is not intended to limit the present application. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present application. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present application without departing from the content of the technical solution of the present application are still within the scope of the technical solution of the present application.

Claims

1. A current control circuit, applied to a projection device comprising at least a light source and a color wheel, characterized in that: include: Main power circuit, used to connect the light source; A discharge circuit connected to the main power circuit; as well as A control circuit connected to the main power circuit and the discharge circuit, wherein the control circuit is used to control the main power circuit to pre-increase the voltage across the light source to a voltage value corresponding to the required driving current after switching during the spoke time of the color wheel when the driving current of the light source needs to be switched from small to large; And when the driving current of the light source needs to be switched from large to small, the voltage across the light source is reduced to a voltage value corresponding to the driving current required after the switching through the discharge circuit during the spoke time of the color wheel.

2. The current control circuit according to claim 1, characterized in that: The control circuit is used to control the discharge time of the discharge circuit according to the driving current required after switching during the spoke time of the color wheel, so as to reduce the voltage across the light source to a voltage value corresponding to the driving current required after switching.

3. The current control circuit according to claim 2, characterized in that: The control circuit is used to determine the discharge time corresponding to the driving current required after switching by looking up a table during the spoke time of the color wheel.

4. The current control circuit according to any one of claims 1 to 3, characterized in that: The main power circuit includes a charging circuit for connecting the light source, and the control circuit is used to control the charging time of the charging circuit according to the driving current required after switching during the spoke time of the color wheel and control the charging circuit to charge so as to pre-increase the light source voltage to a voltage value corresponding to the driving current required after switching.

5. The current control circuit according to claim 4, characterized in that: The control circuit is used to determine the charging time corresponding to the driving current required after switching by looking up a table during the spoke time of the color wheel.

6. The current control circuit according to claim 4, characterized in that: The charging circuit includes a first capacitor connected in parallel with the light source and an inductor connected to the first capacitor and connected in series with the light source. When controlling the charging of the charging circuit, the control circuit controls the charging of the first capacitor and the inductor at the same time, and controls the inductor to continue charging the first capacitor after the first capacitor is saturated, so that the light source voltage is pre-increased to a voltage value corresponding to the driving current required after switching.

7. The current control circuit according to claim 6, characterized in that: The main power circuit also includes a power supply, a first switch, a second switch and a freewheeling diode, one end of the first switch is connected to the positive electrode of the power supply, and the other end is used to connect to one end of the light source; one end of the inductor is connected in series with the second switch and then connected to the negative electrode of the power supply, and the other end is used to connect to the other end of the light source; one end of the first capacitor is connected between the first switch and the positive electrode of the power supply, and the other end is used to connect between the light source and the inductor; the positive electrode of the freewheeling diode is connected between the inductor and the second switch, and the negative electrode is connected between the first switch and the positive electrode of the power supply.

8. The current control circuit according to claim 6, characterized in that: The discharge circuit is connected in parallel with the first capacitor, and the discharge circuit includes a third switch, a first resistor and a second capacitor; the first resistor and the second capacitor are respectively connected in parallel at both ends of the first capacitor, one end of the third switch is connected to one end of the first capacitor, and the other end is connected between the first resistor and the second capacitor.

9. A current control method, characterized in that: Applied to a projection device comprising at least a light source and a color wheel, the current control method is run on a current control circuit as described in any one of claims 1 to 8 to perform: When the driving current of the light source needs to be switched from small to large, during the spoke time of the color wheel, the main power circuit is controlled to pre-increase the voltage across the light source to a voltage value corresponding to the driving current required after the switching; as well as When the driving current of the light source needs to be switched from large to small, the voltage across the light source is reduced to a voltage value corresponding to the driving current required after the switching through the discharge circuit during the spoke time of the color wheel.

10. A projection device, characterized in that: include: light source; A color wheel located in the light path of the light source; as well as A current control device, electrically connected to the light source to drive the light source to emit light; wherein the current control device comprises a current control circuit as claimed in any one of claims 1 to 8; the main power circuit is connected to the light source; the control circuit is used to control the main power circuit to pre-increase the voltage across the light source to a voltage value corresponding to the driving current required after switching during the spoke time of the color wheel when the driving current of the light source needs to be switched from small to large; and to reduce the voltage across the light source to a voltage value corresponding to the driving current required after switching through the discharge circuit during the spoke time of the color wheel when the driving current of the light source needs to be switched from large to small.

Images