Current control method, switching power supply circuit and projection equipment

Abstract

Embodiments of the present application provide a current control method, a switching power supply circuit, and a projection device. The current control method is applied to a switching power supply circuit, wherein the switching power supply circuit includes at least a load capacitor for charging a light source and a first switching tube for controlling the on / off state of the light source. The current control method includes comparing the second driving current required after the switching with the first driving current before the switching when the driving current of the light source needs to be switched; if the second driving current is greater than or equal to the first driving current, precharging the load capacitor during the spoke time of the color wheel; and if the second driving current is less than the first driving current, delaying the on-signal of the first switching tube and controlling the first switching tube to operate in the linear region during the delay period. The current control method provided in the embodiments of the present application enables rapid and stable switching of arbitrary currents 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 method, a switching power supply circuit, and a projection device. Background Art

[0002] The color wheel is a crucial device in existing projection systems, primarily used to receive light from the light source and emit sequential light in sequence. Due to differences in the light output requirements for different colors and the properties of the phosphors in different segments of the color wheel, the light source has different current requirements in different segments of the color wheel. When the light source switches between adjacent segments of the color wheel, it must pass through the spokes between them. To prevent the sequential light emitted by the color wheel in the spokes from mixing, the light source is typically shut off in the spokes and then turned back on after the spokes have ended. Therefore, when the light source switches current between different segments of the color wheel, the current first quickly drops to zero before rising back to the required current value.

[0003] In existing technologies, when a light source switches from high current to low current, a current overshoot often occurs at the moment the light source is turned on. Furthermore, when a light source switches from low current to high current, the current rises too slowly after the light source is turned on. Therefore, there is a need for improvement in existing technologies. Summary of the Invention

[0004] In view of the above problems, the embodiments of the present application provide a current control method, a switching power supply circuit and a 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 method, which is applied to a switching power supply circuit, wherein the switching power supply circuit includes at least a load capacitor for charging a light source and a first switching tube for controlling the on and off of the light source. The current control method includes comparing the second driving current required after the switching with the first driving current before the switching when the driving current of the light source needs to be switched; if the second driving current is greater than or equal to the first driving current, pre-charging the load capacitor during the spoke time of the color wheel; if the second driving current is less than the first driving current, delaying the turn-on signal of the first switching tube, and controlling the first switching tube to operate in the linear region during the delay period.

[0006] In a second aspect, an embodiment of the present application provides a switching power supply circuit, comprising a main power supply circuit and a control module, the main power supply circuit comprising a load capacitor for charging a light source and a first switching tube for controlling the on and off of the light source; the control module is connected to the main power supply circuit and is configured to compare the second driving current required after the switching with the first driving current before the switching when the driving current of the light source needs to be switched; if the second driving current is greater than or equal to the first driving current, the load capacitor is pre-charged during the spoke time of the color wheel; if the second driving current is less than the first driving current, the turn-on signal of the first switching tube is delayed, and the first switching tube is controlled to operate in the linear region during the delay period.

[0007] In a third aspect, an embodiment of the present application provides a projection device, comprising any one of the switching power supply circuits described above; the projection device further comprises a light source and a color wheel; wherein the light source is electrically connected to the switching power supply circuit; and the color wheel is located in the optical path of the light source.

[0008] Compared to the prior art, the current control method, switching power supply circuit, and projection device provided in the embodiments of the present application are applied to a switching power supply circuit. The switching power supply circuit includes at least a load capacitor for charging a light source and a first switching transistor for controlling the on / off of the light source. This current control method compares the second driving current required after the switch with the first driving current before the switch when the light source's driving current needs to be switched. If the second driving current is greater than or equal to the first driving current, the load capacitor is precharged during the spoke time of the color wheel. If the second driving current is less than the first driving current, the turn-on signal of the first switching transistor is delayed, and during the delay period, the first switching transistor is controlled to operate in the linear region. Consequently, when the second driving current is greater than or equal to the first driving current, the light source is turned on, skipping the time from shutdown to recovery, thereby rapidly increasing the light source current to the second driving current. Furthermore, when the second driving current is less than the first driving current, the first switching transistor is subjected to a portion of the output voltage drop, thereby suppressing current overshoot at the moment the light source is turned on. Therefore, when the driving current of the light source switches between any current levels, it reaches a steady state at the moment of turn-on, thereby achieving fast and stable switching of any current.

[0009] These and other aspects of the present application will become more readily 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 following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present 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 Shown Figure 1 Schematic diagram of the structure of the color wheel.

[0013] Figure 3 A flow chart of a current control method provided in an embodiment of the present application is shown.

[0014] Figure 4 A flow chart of another current control method provided in an embodiment of the present application is shown.

[0015] Figure 5 A schematic structural diagram of a switching power supply circuit provided in an embodiment of the present application is shown.

[0016] Figure 6 A conventional control schematic diagram of a switching power supply circuit provided in an embodiment of the present application is shown.

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

[0018] Figure 8 Another control schematic diagram of the current control method provided in an embodiment of the present application is shown.

[0019] Figure 9 The module block diagram of the switching power supply circuit provided in an embodiment of the present application is shown.

[0020] Figure 10 A schematic structural diagram of a switching power supply circuit provided in an embodiment of the present application is shown.

[0021] Figure 11 A working principle diagram of a switching power supply circuit provided in an embodiment of the present application is shown.

[0022] Figure 12 Another working principle diagram of the switching power supply circuit provided in an embodiment of the present application is shown.

[0023] Figure 13 A signal schematic diagram of a switching power supply circuit provided in an embodiment of the present application is shown.

[0024] Figure 14 A schematic structural diagram of a projection system provided in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0025] 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 should not be understood as limiting the present application.

[0026] In order to enable those skilled in the art to better understand the present invention, the following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0027] like Figure 1 As shown, Figure 1 A projection system 10 is schematically shown. The projection system includes a light source control device 11, a light source 12, a color wheel drive 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 drive device 13 is used to drive the color wheel 14 to move. The color wheel 14 is used to receive light from the light source 12 and emit at least two colors of light. The spatial light modulator 16 is used to perform image modulation on the at least two colors of light based on image data DATA to generate image light. The projection lens 17 is used to project the image light to display a projection image. The controller 15 is used to control the light source control device 11 to adjust the on and off timing of the light source 12, the driving speed of the color wheel drive device 13, and the modulation timing of the spatial light modulator 16 to ensure that the three are compatible.

[0028] Specifically, the light source control device 11 is used to control the on and off of the light source 12. The light source 12 is used to receive the driving signal from the light source control device 11 and emit light source light, such as blue light source light. 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 blue light sources. For example, the light source can be an ultraviolet light source, thereby emitting ultraviolet light. Furthermore, the light source 12 can be a semiconductor diode laser light source to provide high-brightness light source light.

[0029] 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 regions A. At least one of the at least two segmented regions A carries a wavelength conversion material. The at least two segmented regions A receive light from a light source and correspondingly emit at least two colors of light. At least one of the at least two colors is converted light generated by the wavelength conversion material being excited by the light from the light source. Each segmented region A emits one of the at least two colors of light. The color wheel drive device 13 is used to drive the color wheel 14 so that the at least two segmented regions A are periodically located along the light path of the light source and correspondingly periodically emit at least two colors of light. In this embodiment, the at least two segmented regions A are arranged along a circumferential direction. The color wheel drive device 13 drives the color wheel 14 to rotate along the center of the color wheel 14 so that the at least two segmented regions A are periodically located along the light path of the light source, thereby periodically emitting at least two colors of light. Due to the different brightness and light output requirements for each color, the driving current of the light source 12 corresponding to each segmented region A may be different. For example, the driving current corresponding to the light source 12 in the first segmented area a1 is a first driving current, and the driving current corresponding to the light source 12 in the second segmented area a2 is a 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 required driving current after adjustment.

[0030] Between two adjacent segmented areas A lies the spoke area B. When the light source 12 passes through two adjacent segmented areas A, it inevitably passes through the spoke area B. When the light source 12 passes through the spoke area B, the color wheel 14 emits a mixture of light corresponding to the colors of the two adjacent segmented areas A, known as spoke light. Generally, to prevent the generation of spoke light, the light source 12 is turned off when passing through the spoke area B, preventing it from emitting light in the spoke area B. In other words, the light source 12 turns off when entering the spoke area B and turns on when leaving it.

[0031] 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.

[0032] After rigorous testing, the inventors found that when a light source passes through two adjacent segmented areas, if the driving current corresponding to the next segmented area is greater than the driving current corresponding to the previous segmented area, when the light source leaves the spoke area and is turned on again, the driving current of the light source rises too slowly; and if the driving current corresponding to the next segmented area is less than the driving current corresponding to the previous segmented area, at the moment of leaving the spoke area and turning on again, the voltage carried by both ends of the light source is too large, resulting in current overshoot.

[0033] To address this issue, the inventors conducted extensive research and testing, resulting in the current control method, switching power supply circuit, and projection device disclosed herein. The current control method is applied to a switching power supply circuit comprising at least a load capacitor for charging a light source and a first switching transistor for controlling the on / off of the light source. This current control method compares the required second drive current after the switch with the first drive current before the switch when the light source's drive current needs to be switched. If the second drive current is greater than or equal to the first drive current, the load capacitor is pre-charged during the spoke time of the color wheel. If the second drive current is less than the first drive current, the turn-on signal of the first switching transistor is delayed, and during this delay, the first switching transistor is controlled to operate in the linear region. Consequently, when the second drive current is greater than or equal to the first drive current, the light source is turned on, skipping the time from shutdown to resumption, thereby rapidly increasing the light source current to the second drive current. Furthermore, when the second drive current is less than the first drive current, the first switching transistor is subjected to a portion of the output voltage drop, thereby suppressing current overshoot at the moment the light source is turned on. Therefore, when the driving current of the light source switches between any current values, the steady state is reached at the moment of switching on, thereby achieving fast and stable switching of any current.

[0034] like Figure 3 As shown, Figure 3 A schematic flow chart 100 of a current control method provided in an embodiment of the present application is shown. This current control method 100 is applied to a switching power supply circuit, which includes at least a load capacitor for charging a light source and a first switching transistor for controlling the on / off of the light source. This current control method 100 may include the following steps S110 to S30.

[0035] Step S110 : When the driving current of the light source needs to be switched, the second driving current required after the switching is compared with the first driving current before the switching.

[0036] In the embodiment of the present application, the period during which the light source passes through the segmented area of ​​the color wheel is called the segment time, and the period during which the light source passes through the spoke area of ​​the color segment is called the spoke time. The spoke time can also be called the spoke time of the color wheel. When the light source passes through two adjacent first segmented areas and second segmented areas, the light source needs to sequentially pass through the first segmented time, the spoke time, and the second segmented time. The driving current required for the light source in the first segmented time is the first driving current, and the driving current required for the light source in the second segmented time is the second driving current. When the light source passes through two adjacent first segmented areas and second segmented areas, it is necessary to switch the first driving current to the second driving current, and the second driving current is the driving current required after switching. In this embodiment, the second driving current after switching can be greater than the first driving current before switching, or the second driving current after switching can be less than the first driving current before switching, or the second driving current after switching can be equal to the first driving current before switching.

[0037] In this embodiment, at the moment the light source leaves the first segmented area and before entering the spoke area, the second driving current required for the second segmented area is compared with the first driving current corresponding to the first segmented area to determine whether the driving current of the light source needs to be increased or decreased when the light source enters the second segmented area.

[0038] In some embodiments, the driving current corresponding to each segmented area can be set in advance, so the size of the driving current required by the light source when it passes through different segmented areas has been determined. At this time, when the light source needs to switch the driving current, step S120 or step S130 can be directly executed to speed up the response speed.

[0039] Step S120: If the second driving current is greater than or equal to the first driving current, pre-charging the load capacitor during the spoke time of the color wheel.

[0040] In this embodiment, if the second drive current is greater than the first drive current, the light source's drive current must switch from a high current to a low current when switching from the first segment to the second segment, which also means that the drive current needs to decrease. During the spoke time, the light source is turned off; after the spoke time ends and the light source turns back on in the second segment, the light source enters the second segment. In this embodiment, the load capacitor is precharged during the spoke time when the light source is off. This allows the voltage across the light source to rise from the voltage corresponding to the first drive current to the voltage corresponding to the second drive current during the spoke time. In other words, before the light source is turned on, the voltage across the light source has already reached the voltage corresponding to the second drive current required for the second segment. This allows the system to enter steady state and prepare for the light source to turn on in advance. This allows the system to skip the time it takes to resume operation after the light source turns on when the second segment arrives, accelerating the current rise rate and quickly reaching the second drive current.

[0041] Furthermore, if the second drive current is equal to the first drive current, the magnitude of the drive current remains unchanged when the light source switches from the first segmented time to the second segmented time. Since the light source needs to undergo a spoke time during the switching process, during which it is turned off, the magnitude of the drive current remains unchanged when the light source switches from the first segmented time to the second segmented time. However, the drive current still needs to rise, i.e., it drops from the first drive current to zero and then rises from zero to the second drive current. In this embodiment, during this process, the load capacitor is pre-charged during the spoke time when the light source is turned off. This allows the voltage across the light source to rise from the voltage corresponding to the first drive current to the voltage corresponding to the second drive current during the spoke time. Therefore, even if the magnitude of the second drive current remains unchanged from the first drive current, the current rise rate of the light source can be accelerated, allowing the current of the light source to quickly reach the second drive current, thereby improving the current switching speed.

[0042] Step S130: If the second driving current is less than the first driving current, delaying the turn-on signal of the first switch tube, and controlling the first switch tube to operate in a linear region during the delay period.

[0043] In this embodiment, if the second drive current is less than the first drive current, the light source's drive current must switch from a high current to a low current when switching from the first segment to the second segment, which also means that the drive current needs to decrease. During the spoke time, the light source is turned off; after the spoke time ends and the light source enters the second segment, the light source turns on again. When the light source enters the spoke time, the first switch must be turned on to activate the light source. In this embodiment, when the light source enters the spoke time, the turn-on signal to the first switch is delayed. During this delay, the first switch is controlled to operate in the linear region, causing the first switch to slowly turn on. At the end of the delay, the turn-on signal fully turns on the first switch, turning on the light source. Because the first switch operates in the linear region before turning on, it experiences a certain voltage drop across its terminals. This allows the light source to reach a steady state at the moment of turning on. The high voltage corresponding to the first drive current is not applied to the terminals of the light source, thus suppressing current overshoot.

[0044] The current control method provided in an embodiment of the present application compares the second drive current required after the switch with the first drive current before the switch when the light source's drive current needs to be switched. If the second drive current is greater than or equal to the first drive current, the load capacitor is pre-charged during the spoke time of the color wheel. This allows the system to resume operation after the light source is turned on, accelerating the current rise rate of the light source and allowing the light source's current to quickly reach the second drive current. Furthermore, if the second drive current is less than the first drive current, the turn-on signal of the first switching transistor is delayed, and during the delay period, the first switching transistor is controlled to operate in the linear region, subjecting the first switching transistor to a partial voltage drop. Consequently, at the moment the light source is turned on, the high voltage corresponding to the first drive current is not applied to the light source, thereby suppressing current overshoot. Therefore, the current control method provided in an embodiment of the present application ensures that the light source reaches a steady state at the moment of switching between any current levels, thereby achieving fast and stable switching of any current.

[0045] like Figure 4 As shown, the embodiment of the present application also provides another current control method 200, which is applied to the switching power supply circuit 20 to switch the driving current of the light source. Figure 5 As shown, Figure 5The schematic diagram of the circuit structure of a switching power supply circuit 20 is shown. The switching power supply circuit 20 is a Boost circuit. In some embodiments, the switching power supply circuit 20 can also be a Buck circuit. The switching power supply circuit 20 includes a first switching tube Q1, a second switching tube Q2, a load capacitor C1, an inductor L1, and a diode D1, wherein the first switching tube Q1 and the second switching tube Q2 are NMOS tubes. One end of the inductor L1 is connected to the power supply, and the other end is connected to the positive electrode of the diode D1; the cathode of the diode D1 is connected to the first end of the load capacitor C1; the drain of the second switching tube Q2 is connected between the inductor L1 and the diode D1, and the source is grounded; the first end of the load capacitor C1 is also used to connect to one end of the light source, and the second end is connected to the source of the second switching tube Q2; the drain of the first switching tube Q1 is used to connect to the other end of the light source, and the source is connected to the second end of the load capacitor C1.

[0046] like Figure 6 As shown, Figure 6 The conventional control diagram based on the above-mentioned switching power supply circuit 20 is shown. The mainboard outputs a signal SPK to the constant current control chip, so that the constant current control chip outputs a signal Sq1 to the first switch tube Q1 and outputs a signal Sq2 to the second switch tube Q2. When the light source is in the spoke time, the signal SPK is at a low level. At this time, the signals Sq1 and Sq2 are both at a low level. The first switch tube Q1 and the second switch tube Q2 are turned off, and the light source is turned off. When the light source enters the segmented time, the signal SPK is at a high level, so that the sq1 signal is at a high level, the first switch tube Q1 is turned on to turn on the light source, and at the same time, the signal Sq2 operates in a high-frequency PWM (Pulse Width Modulation) to charge the load capacitor. At the same time, the mainboard outputs a current amplitude signal I2C to the MCU (Microcontroller Unit). The MCU outputs an amplitude control signal V1 to the constant current control chip according to the current amplitude signal I2C, so that the constant current control chip controls the duty cycle of the signal Sq2 according to the amplitude control signal V1, thereby increasing the voltage across the load capacitor C1 to a voltage value corresponding to the power supply driving current, thereby increasing the driving current of the light source to the corresponding current value.

[0047] When the light source passes through two adjacent segmented times, if the current amplitude signals of the two adjacent segmented times are inconsistent, the voltage across the load capacitor cannot suddenly change, which will result in the inability to achieve a rapid rise and fall of the current. For example, when the second current amplitude signal entering the second segmented time is greater than the first current amplitude signal entering the first segmented time, at the moment the first switch tube enters the second segmented time, the voltage across the load capacitor cannot suddenly change, and the voltage across the load capacitor needs to rise from the voltage value corresponding to the first drive current to the voltage value corresponding to the second drive current, thereby causing the drive current of the light source to rise too slowly; for another example, when the second current amplitude signal entering the second segmented time is less than the first current amplitude signal entering the first segmented time, at the moment the first switch tube enters the second segmented time, the voltage across the load capacitor cannot suddenly change, and the voltage across the load capacitor needs to drop from the voltage value corresponding to the first drive current to the voltage value corresponding to the second drive current, thereby causing the two ends of the light source to bear a large voltage corresponding to the first drive current at the moment the light source is turned on, resulting in current overshoot.

[0048] The current control method 200 provided in this embodiment is dedicated to solving the above problems. Taking the above switching power supply circuit 20 as an example, Figure 4 As shown, the current control method provided in this embodiment may include the following steps S210 to S240.

[0049] Step S210: When the driving current of the light source needs to be switched, the second driving current required after the switching is compared with the first driving current before the switching.

[0050] In this embodiment, when the light source experiences two adjacent segmented times, the current amplitude signal after switching is compared with the current amplitude signal before switching. It can be understood that the current amplitude signal can represent the current value of the driving current required by the light source within the segmented time.

[0051] For example, when a light source experiences adjacent first and second segmented times, during the first segmented time, the driving current of the light source is changed to the first driving current according to the first current amplitude signal; during the second segmented time, the driving current of the light source is changed to the second driving current according to the second current amplitude signal. When the light source ends the first segmented time, the second current amplitude signal corresponding to the next segmented time is compared with the first amplitude signal corresponding to the previous segmented time to determine the magnitude of the second driving current required for the upcoming second segmented time and the first driving current during the first segmented time.

[0052] Furthermore, if the second driving current is less than the first driving current, steps S220 to S230 may be performed. If the second driving current is greater than or equal to the first driving current, step S240 may be performed.

[0053] Step S220 : When the rising edge of the light source start-up signal is triggered, keep outputting the first conduction signal to the first switch tube within a first preset time, and adjust the rising edge speed of the first conduction signal.

[0054] In this embodiment, if the second driving current is less than the first driving current, when the rising edge of the start-up signal of the light source is triggered, the turn-on signal of the first switch tube is delayed, and the gate drive voltage of the first switch tube is controlled during the delay period so that the first switch tube operates in the linear region.

[0055] like Figure 7 As shown in the figure, a control schematic diagram of the current control method provided by this embodiment when the second drive current is less than the first drive current is shown. It should be noted that this control schematic diagram is a schematic diagram of the internal control principle of the main controller on the main board. The main controller of the main board outputs a start signal V2, which is a synchronization signal of the signal SPK. When the start signal V2 is at a high level, it means that the light source is in the segment time, the first switch tube Q1 is turned on, and the light source is turned on and works normally; when the start signal is at a low level, it means that the light source is in the spoke time, the first switch tube Q2 is turned off, and the light source is turned off.

[0056] Furthermore, the turn-on signal of the first switch Q1 includes a first turn-on signal and a second turn-on signal, wherein the voltage of the second turn-on signal is greater than the voltage of the first turn-on signal. When triggered by the rising edge of the light source start signal V2, the first turn-on signal is continuously output to the first switch for a first preset time, and the rising edge speed of the first turn-on signal is adjusted.

[0057] In this embodiment, the second turn-on signal is signal Sq1, a conventional drive signal that controls the on / off of the first switch Q1. When the second drive current is less than the first drive current, the rising edge of the start signal V2 is detected. This rising edge of the start signal V2 indicates the moment when the light source leaves the spoke time and enters the segmented time. In this embodiment, this rising edge of the start signal V2 indicates the moment when the light source leaves the spoke time and enters the second segmented time. Furthermore, the rising edge of the start signal V2 triggers the generation of signal Stq1. At this time, signal Stq1 is high and triggers the operation of the delay module. When the delay module operates, it triggers a delay on signal SPK, extending the duration of signal SPK's low level, thereby delaying the turn-on of signal Sq1 by turning on the first switch Q1. Simultaneously, signal Stq1 triggers the generation of signal Saq1, the aforementioned first turn-on signal. Signal Saq1 remains input to the first switch Q1 for a first preset time. Signal Saq1 then serves as the gate drive voltage for the first switch Q1. Furthermore, by adjusting the rising edge speed of the signal Saq1 and the voltage of the signal Saq1, the first switch tube Q1 operates in the linear region within the first preset time. Due to the characteristics of the MOS tube, when the MOS tube operates in the linear region, it is equivalent to a variable resistor. Therefore, at this time, the first switch tube Q1 is equivalent to a variable resistor connected in series with the light source, so that it can bear part of the voltage drop at the moment when the light source is turned on.

[0058] Step S230: when the rising edge is triggered, delay for a second preset time, and output a second conduction signal to the first switch tube when the second preset time arrives.

[0059] like Figure 7 As shown, in this embodiment, when the rising edge of the start signal V2 triggers the generation of the signal Stq1, the signal Stq1 is high and triggers the operation of the delay module. The delay time of the delay module is the second preset time. When the second preset time arrives, the main controller generates a signal SPK through the delay module and outputs it to the constant current control chip. At this time, the signal Sq1 is high, causing the first switch Q1 to operate in the conduction region, thereby turning on the first switch Q1. At the moment the first switch Q1 is turned on, the first switch Q1 bears a portion of the voltage drop, thereby suppressing current overshoot.

[0060] It should be noted that the first preset time and the second preset time are two different time periods. In this embodiment, the first preset time is greater than the second preset time, that is, the signal Saq1 is turned off only after the delay time expires, thereby ensuring that the signal Saq1 remains input to the first switch tube throughout the entire delay period of the delay module.

[0061] Step S240: When triggered by the falling edge of the light source start-up signal, keep outputting the PWM signal to the second switch tube within a third preset time.

[0062] In this embodiment, if the second driving current is greater than or equal to the first driving current, then when the falling edge of the light source is triggered, the PWM signal is continuously output to the second switch for a third predetermined time to control the charging of the load capacitor. The third predetermined time is less than the spoke time of the color wheel.

[0063] like Figure 8 As shown, Figure 8 The following diagram illustrates a control scheme for the current control method provided in this embodiment when the second drive current is greater than or equal to the first drive current. It should be noted that this control scheme represents the internal control principle of the main controller on the mainboard. The PWM signal includes a first PWM signal and a second PWM signal. When the light source's turn-on signal is at a high level, the first PWM signal is input to the second switch transistor. The second PWM signal remains input to the second switch transistor for a third preset time. In this embodiment, the first PWM signal is the Sq2 signal, which is a conventional PWM signal that drives the second switch transistor Q2 in high-frequency PWM operation. The second PWM signal is the Saq2 signal. When the second drive current is greater than the first drive current, the falling edge of the turn-on signal V2 is detected. This falling edge indicates the moment when the light source leaves the segmented time and enters the spoke time. In this embodiment, the falling edge of the turn-on signal V2 indicates the moment when the light source leaves the first segmented time and enters the spoke time. Furthermore, the falling edge of the start signal V2 triggers the generation of the signal Stq2. At this time, Stq2 is at a high level and triggers the PWM working module to generate the signal Saq2. The signal Saq2 is input to the second switch tube Q2 to drive the second switch tube Q2 to operate at high-frequency PWM within the spoke time, and then pre-charge the load capacitor C1 within the spoke time, so that the voltage across the light source reaches the voltage value corresponding to the second drive current before it is turned on. The system enters the steady state in advance and is ready to turn on the light source. 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 making the current of the light source quickly reach the second drive current.

[0064] It is worth noting that since the signal Stq2 does not trigger the delay module to work, the timing of the signal SPK is synchronized with the timing of the start signal. When the start signal rises, the light source leaves the spoke time and enters the second segment time. At this time, the signal Sq2 drives the second switch tube to work at high frequency PWM, and the high level of the signal Sq1 turns on the first switch tube and then turns on the light source. At the moment 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 during the spoke time, the drive current of the light source can quickly reach the second drive current.

[0065] In this embodiment, the third preset time may be any time period within the spoke time, that is, the second switch tube may be triggered to perform high-frequency PWM operation within any time period within the spoke time to pre-charge the load capacitor.

[0066] The current control method provided in this embodiment compares the second drive current required after the light source is switched with the first drive current before the switch. If the second drive current is greater than the first drive current, the load capacitor is precharged during the spoke time of the color wheel. This allows the system to resume operation after the light source is turned on, accelerating the current rise rate of the light source and allowing the light source current to quickly reach the second drive current. Furthermore, if the second drive current is less than the first drive current, the turn-on signal of the first switching transistor is delayed. During the delay period, the first switching transistor is controlled to operate in the linear region, subjecting the terminals of the first switching transistor to a partial voltage drop. Consequently, at the moment the light source is turned on, the terminals of the light source are not subjected to the high voltage corresponding to the first drive current, thereby suppressing current overshoot. Therefore, the current control method provided in this embodiment of the application ensures that the light source reaches a steady state at the moment of switching between any current levels, thereby achieving rapid and stable switching of any current.

[0067] like Figure 9 As shown, the embodiment of the present application further provides a switching power supply circuit 300, which includes a main power supply circuit 310 and a control module 320 connected to the main power supply circuit 310. The main power supply circuit 310 includes a load capacitor for charging the light source and a first switch tube for controlling the on and off of the light source; the control module 320 is configured to compare the second drive current required after the switch with the first drive current before the switch when the drive current of the light source needs to be switched; if the second drive current is greater than or equal to the first drive current, the load capacitor is pre-charged during the spoke time of the color wheel; if the second drive current is less than the first drive current, the turn-on signal of the first switch tube is delayed, and the first switch tube is controlled to operate in the linear region during the delay period.

[0068] In the embodiment of the present application, the period during which the light source passes through the color wheel segment area is referred to as the segment time, and the period during which the light source passes through the color segment spoke area is referred to as the spoke time. When the light source passes through two adjacent first segment areas and second segment areas, the light source needs to sequentially pass through the first segment time, the spoke time, and the second segment time. The driving current required for the light source during the first segment time is the first driving current, and the driving current required for the light source during 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.

[0069] The control module 320 compares the second drive current required after the switch with the first drive current before the switch. If the second drive current is greater than the first drive current, the drive current of the light source switches from a high current to a low current when the light source switches from the first segment time to the second segment time, which also means that the drive current needs to decrease. During the spoke time, the light source is turned off; after the spoke time ends and the light source turns back on in the second segment time. In this embodiment, the load capacitor is precharged during the spoke time when the light source is off. This allows the voltage across the light source to rise from the voltage corresponding to the first drive current to the voltage corresponding to the second drive current during the spoke time. In other words, before the light source is turned on, the voltage across the light source has already reached the voltage corresponding to the second drive current required for the second segment time. This allows the system to enter steady state and prepare for the light source to turn on in advance. This allows the system to skip the time it takes to resume operation after the light source turns on when the second segment time arrives, accelerating the current rise rate and quickly reaching the second drive current.

[0070] If the second drive current is equal to the first drive current, the magnitude of the drive current remains unchanged when the light source switches from the first segmented time to the second segmented time. Since the light source undergoes a spoke time during the switching process, during which it is turned off, the drive current remains unchanged during the switch from the first segmented time to the second segmented time. However, the drive current still undergoes a ramp-up process, i.e., it drops from the first drive current to zero and then rises from zero to the second drive current. In this embodiment, during this process, the load capacitor is pre-charged during the spoke time when the light source is turned off. This pre-charges the voltage across the light source from the voltage corresponding to the first drive current to the voltage corresponding to the second drive current during the spoke time. Therefore, even if the magnitude of the second drive current remains unchanged from the first drive current, the current rise rate of the light source is accelerated, allowing the current of the light source to quickly reach the second drive current, thereby improving the current switching speed.

[0071] If the second drive current is less than the first drive current, the light source's drive current must switch from a high current to a low current when transitioning from the first segment to the second segment, meaning the drive current needs to decrease. During the spoke time, the light source is turned off; after the spoke time ends and the light source enters the second segment, it turns back on. When the light source enters the spoke time, the first switch must be turned on to activate the light source. In this embodiment, when the light source enters the spoke time, the turn-on signal to the first switch is delayed. During this delay, the first switch is controlled to operate in the linear region, causing the first switch to slowly turn on. At the end of the delay, the turn-on signal fully turns on the first switch, turning on the light source. Because the first switch operates in the linear region before turning on, it experiences a voltage drop across its terminals. This allows the light source to reach a steady state at the moment of turn-on. The high voltage corresponding to the first drive current is not applied to the terminals of the light source, thus suppressing current overshoot.

[0072] Therefore, the switching power supply circuit 300 provided in this embodiment enables the driving current of the light source to reach a steady state at the moment of switching on when switching between any current values, thereby achieving fast and stable switching of any current.

[0073] Specifically, if Figure 10 As shown, the main power supply circuit 310 includes a first switching transistor Q1, a second switching transistor Q2, a load capacitor C1, an inductor L1, and a diode D1. The first switching transistor Q1 and the second switching transistor Q2 are NMOS transistors. One end of the inductor L1 is connected to the power supply, and the other end is connected to the anode of the diode D1. The cathode of the diode D1 is connected to the first end of the load capacitor C1. The drain of the second switching transistor Q2 is connected between the inductor L1 and the diode D1, the source is grounded, and the gate is connected to the control module 320. The first end of the load capacitor C1 is also used to connect to one end of the light source, and the second end is connected to the source of the second switching transistor Q2. The drain of the first switching transistor Q1 is used to connect to the other end of the light source, the source is connected to the second end of the load capacitor C1, and the gate is connected to the control module 320.

[0074] The control module 320 is connected to the first switching transistor Q1 and the second switching transistor Q2 to control the on and off of the first switching transistor Q1 and the second switching transistor Q2. In this embodiment, the control module 320 may include a mainboard, a constant current control chip, and an MCU (Microcontroller Unit), wherein the mainboard is provided with a main controller. In some embodiments, the control module 320 may include only the mainboard; the constant current control chip and MCU may be external chips.

[0075] In this embodiment, the control module 320 is configured to, if the second drive current is less than the first drive current, delay the turn-on signal of the first switch Q1 when the rising edge of the light source turn-on signal is triggered, and control the gate drive voltage of the first switch Q1 during the delay period to enable the first switch Q1 to operate in the linear region. If the second drive current is greater than or equal to the first drive current, then, if the falling edge of the light source turn-on signal is triggered, maintain outputting a PWM (Pulse Width Modulation) signal to the second switch Q2 for a third preset time to control the charging of the load capacitor C1. The third preset time is less than the spoke time of the color wheel.

[0076] like Figure 11 and Figure 12 As shown, Figure 11 and Figure 12 FIG. 3 is a schematic diagram showing the working principle of the switching power supply circuit 300 provided in this embodiment. It should be noted that, Figure 11 and Figure 12 The main controller on the motherboard outputs the SPK signal to the constant current control chip, which then outputs the signal Sq1 to the first switch tube Q1 and the signal Sq2 to the second switch tube Q2 according to the signal SPK. When the signal SPK is high, the signal Sq1 is high and the signal Sq2 is a high-frequency PWM signal; when the signal SPK is low, both the signal Sq1 and the signal Sq2 are low. Figure 13 As shown in the figure, it shows the schematic diagram of the change of the control quantity and state quantity of the system over time when the light source switches between different segmented areas in this embodiment. Figures 11-13 The principle of the embodiment of the present application is explained. It should be noted that the embodiment of the present application is only 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.

[0077] First of all, Figure 13 The various signals shown are explained below. The synchronization signal is a start signal V2 used to indicate that the light source is turned on. When the synchronization signal is at a high level, it is used to indicate that the light source is turned on. When the synchronization signal is at a low level, it is used to indicate that the light source is turned off. Signals Sq1 and Saq1 are turn-on signals of the first switch tube Q1. Signals Sq2 and Saq2 are control signals of the second switch tube Q2.

[0078] exist Figure 13In the example, 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 of ​​the color wheel. T0-T1 represents the first segmented time, T1-T3 represents the first spoke time, T3-T4 represents the second segmented time, T4-T5 represents the second spoke time, and T5-T8 represents the third segmented time. Assume that the second drive current corresponding to the second segmented area is greater than the first drive current corresponding to the first segmented area; and the third drive current corresponding to the third segmented area is less than the second drive 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 drive current needs to increase; when the light source switches from the second segmented area to the third segmented area, the drive current needs to decrease. It should be noted that since the principle when the second drive current is equal to the first drive current is the same as when the second drive current is greater than the first drive current, the following description will only use the case where the second drive current is greater than the first drive current as an example.

[0079] T0~T1 stage: the light source is in the first segment time, the mainboard outputs a high-level signal SPK to the constant current control chip. At this time, the signal Sq1 output by the constant current control chip to the first switch tube Q1 is high, thereby turning on the light source; the signal Sq2 output by the constant current control chip to the second switch tube Q2 is a high-frequency PWM signal.

[0080] T1 moment: Figure 12 and Figure 13 As shown, the light source leaves the first segment time and enters the first spoke time. The synchronization signal is on a falling edge. This synchronization signal is a start signal V2 that is synchronized with signal SPK and is used to turn on the light source. In other words, the timing of the synchronization signal is synchronized with that of signal SPK. At this time, because the second drive current required for the next segment time is greater than the first drive current for the previous segment time, the mainboard triggers the generation of signal Stq2 when the synchronization signal is on a falling edge. Simultaneously, this signal Stq2 triggers the PWM operation module to generate signal Saq2. Signal Saq2 is a high-frequency PWM signal, which is input and output to the second switch transistor Q2 to control its high-frequency PWM operation.

[0081] Phase T1-T2: This phase is during the first spoke period, during which the light source is off. During this period, signal Sq2 drives the second switch Q2 to operate in high-frequency PWM mode, thereby charging the load capacitor C1. By configuring the frequency, duty cycle, and duration of signal Sq2, the voltage of load capacitor C1 can be pre-increased to a voltage corresponding to the second drive current before the light source is turned on. It is worth noting that signal Sq2 can be input to the second switch Q2 at any time during the first spoke period to drive the second switch Q2 in high-frequency PWM mode, and is not limited to being input to the second switch Q2 at time T1.

[0082] At time T3, the light source leaves the first spoke and enters the second segment. At this time, the synchronization signal is rising, and the signal SPK is also rising. The constant current control chip outputs a high-level signal Sq1 to the first switch tube Q1 to turn on the light source, and outputs a high-frequency PWM signal Sq2 to the second switch tube Q2. At this time, since the voltage across the load capacitor C1 has already risen to the voltage value corresponding to the second drive current, the voltage across the light source has also risen to the voltage value corresponding to the second drive current. At this moment, when the light source is turned on, the drive current of the light source can quickly rise to the current value corresponding to the second drive current, and the system quickly enters the constant current closed-loop steady state.

[0083] T3~T4 stage: The light source continues to emit light in the second segment time, and the system is in a constant current closed-loop steady state.

[0084] T4~T5 stage: the light source is in the second spoke time. At this time, the synchronization signal is low, the signal SPK is also low, the constant current control chip outputs a low-level signal Sq1 to the first switch tube Q1 and outputs a low-level signal Sq2 to the second switch tube Q2, and the light source is turned off.

[0085] T5 moment: Figure 11 and Figure 13 As shown, the light source leaves the second spoke and enters the third segment. At this time, the synchronization signal is on a rising edge. Because the third drive current required for the next segment is less than the second drive current for the previous segment, the rising edge of the synchronization signal triggers the generation of signal Stq1. This signal Stq1 triggers the delay module, which in turn triggers a delay in signal SPK. This delay extends the duration of signal SPK's low level, causing signal Sq1 to turn on the first switch Q1. Simultaneously, signal Stq1 triggers the generation of signal Saq1, which is input to the first switch Q1.

[0086] Stages T5-T7: During this stage, signal Saq1 is input to the first switch Q1. By setting the rising edge speed of signal Saq2, the first switch Q1 is slowly turned on. During this stage, the first switch Q1 operates in its linear region. Due to the characteristics of MOS transistors, when operating in the linear region, they act as a variable resistor. Therefore, the first switch acts as a variable resistor in series with the light source, thereby absorbing some of the voltage drop from the light source.

[0087] Phase T5-T6: This phase is the delay time of the delay module. In this embodiment, the duration of phase T5-T7 is longer than that of phase T5-T6, ensuring that signal Saq2 remains input to the first switch Q1 throughout the entire delay period of the delay module. During this phase, signal SPK is at a low level, and therefore both signals Sq1 and Sq2 are at a low level.

[0088] At T6: The delay ends, and the motherboard outputs a high-level signal SPK to the constant-current control chip. It should be noted that the delay module maintains the SPK signal at a low level during the delay period, extending the SPK low-level period. After the delay ends, the SPK signal is turned high again. At this point, the SPK signal's timing is out of sync with the synchronization signal. Furthermore, when the SPK signal transitions to a high level, the constant-current control chip outputs a high-level signal Sq1 to the first switch Q1, fully turning it on. At the moment the light source is turned on, the first switch Q1 bears some of the voltage drop, thereby suppressing current overshoot.

[0089] T6~T8 stage: The light source continues to emit light in the third segment time, and the system is in a constant current closed-loop steady state.

[0090] To summarize, when the light source passes through adjacent segmented areas of the color wheel, if the drive current needs to increase, the load capacitor C1 is precharged during the spoke time of the color wheel, 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 drive current needs to decrease, the turn-on signal of the first switch tube Q1 is delayed, and during the delay period, the first switch tube Q1 is controlled to operate in the linear region, thereby suppressing current overshoot at the moment the light source is turned on. As a result, no matter how large the difference in the drive current before and after the light source switches between segmented areas, the ideal control effect can be achieved, and fast and stable control of any segmented current can be achieved. Based on this, the segmented currents can differ more, thereby reducing the constraints on the angle ratio of each color wheel color, and can correct the system deviation of white balance through the segmented current, improving the product yield and achieving a better display effect.

[0091] The switching power supply circuit provided in the embodiments of the present application comprises a main power supply circuit and a control module. When the light source's drive current needs to be switched, the control module compares the second drive current required after the switch with the first drive current before the switch. If the second drive current is greater than or equal to the first drive current, the load capacitor is precharged during the spoke time of the color wheel. This allows the system to resume operation after the light source is turned on, accelerating the current rise rate of the light source and allowing the light source current to quickly reach the second drive current. Furthermore, if the second drive current is less than the first drive current, the turn-on signal of the first switch is delayed. During the delay period, the first switch is controlled to operate in the linear region, subjecting the first switch to a partial voltage drop across the terminals. Consequently, the high voltage corresponding to the first drive current is not applied to the terminals of the light source at the moment of switching, thereby suppressing current overshoot. Therefore, the current control method provided in the embodiments of the present application ensures that the light source's drive current reaches a steady state at the moment of switching between any current levels, thereby achieving fast and stable switching of any current.

[0092] like Figure 14 As shown, the embodiment of the present application further provides a projection device 400, which includes a light source 410, a color wheel 420, and the aforementioned switching power supply circuit 300. The color wheel 410 is located in the optical path of the light source 420, and the switching power supply circuit 300 is electrically connected to the light source to control the light output of the light source 410.

[0093] A projection device provided in an embodiment of the present application includes a light source, a color wheel, and a switching power supply circuit. When the light source's drive current needs to be switched, the switching power supply circuit compares the second drive current required after the switch with the first drive current before the switch. If the second drive current is greater than or equal to the first drive current, the load capacitor is precharged during the spoke time of the color wheel. This allows the system to resume operation after the light source is turned on, accelerating the current rise rate of the light source and allowing the current of the light source to quickly reach the second drive current. Furthermore, if the second drive current is less than the first drive current, the turn-on signal of the first switch is delayed. During the delay period, the first switch is controlled to operate in a linear region, subjecting the first switch to a partial voltage drop across the terminals. Consequently, when the light source is turned on, the terminals are not subjected to the high voltage corresponding to the first drive current, thereby suppressing current overshoot. Therefore, the current control method provided in an embodiment of the present application ensures that the light source reaches a steady state at the moment of switching between any current levels, thereby achieving rapid 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 various colors on the color wheel. In addition, the segmented currents can be used to correct the system deviation of the white balance, thereby improving the product yield and achieving better display effects.

[0094] The above description is merely 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 above with preferred embodiments, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to equivalent embodiments using the technical contents disclosed above 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 method, applied to a switching power supply circuit, wherein the switching power supply circuit comprises at least a load capacitor for charging a light source and a first switching tube for controlling the on / off of the light source, characterized in that: include: When the driving current of the light source needs to be switched, the second driving current required after the switching is compared with the first driving current before the switching; If the second driving current is greater than or equal to the first driving current, precharging the load capacitor during a spoke time of a color wheel, wherein the color wheel is located on an optical path of light emitted by the light source and includes a plurality of segmented areas and spoke areas between adjacent segmented areas, and the spoke time is a time period during which the light source passes through the spoke areas; If the second driving current is less than the first driving current, the turn-on signal of the first switch tube is delayed, and the first switch tube is controlled to operate in a linear region during the delay period.

2. The current control method according to claim 1, wherein: The delaying of the turn-on signal of the first switch tube and operating the first switch tube in a linear region during the delay period includes: When the rising edge of the light source start signal is triggered, the turn-on signal of the first switch tube is delayed, and the gate drive voltage of the first switch tube is controlled during the delay period to make the first switch tube operate in the linear region.

3. The current control method according to claim 2, wherein: The conduction signal includes a first conduction signal and a second conduction signal, wherein the voltage of the second conduction signal is greater than the voltage of the first conduction signal; when the rising edge of the light source start signal is triggered, the conduction signal of the first switch tube is delayed, and the gate drive voltage of the first switch tube is controlled during the delay period so that the first switch tube operates in the linear region, including: When triggered by the rising edge of the light source start signal, keep outputting the first conduction signal to the first switch tube within a first preset time, and adjust the rising edge speed of the first conduction signal; and When the rising edge of the light source start signal is triggered, the second preset time is delayed, and the second conduction signal is output to the first switch tube when the second preset time arrives; wherein the first preset time is greater than the second preset time.

4. The current control method according to claim 1, wherein: The switching power supply circuit further includes a second switching tube for controlling charging of the load capacitor; and precharging the load capacitor during the spoke time of the color wheel includes: When triggered by the falling edge of the light source start signal, the PWM signal is output to the second switch tube within a third preset time to control the charging of the load capacitor; the third preset time is less than the spoke time of the color wheel.

5. The current control method according to claim 4, wherein: The PWM signal includes a first PWM signal and a second PWM signal; the first PWM signal is input to the second switch tube when the start signal of the light source is at a high level, and the second PWM signal remains input to the second switch tube within the third preset time.

6. A switching power supply circuit, characterized in that: include: A main power supply circuit, comprising a load capacitor for charging the light source and a first switch tube for controlling the on and off of the light source; The control module, connected to the main power circuit, is configured to: When the driving current of the light source needs to be switched, the second driving current required after the switching is compared with the first driving current before the switching; If the second driving current is greater than or equal to the first driving current, precharging the load capacitor during a spoke time of a color wheel, wherein the color wheel is located on an optical path of light emitted by the light source and includes a plurality of segmented areas and spoke areas between adjacent segmented areas, and the spoke time is a time period during which the light source passes through the spoke areas; If the second driving current is less than the first driving current, the turn-on signal of the first switch tube is delayed, and the first switch tube is controlled to operate in a linear region during the delay period.

7. The switching power supply circuit according to claim 6, wherein: The control module is further configured to: if the second drive current is less than the first drive current, then when the rising edge of the start signal of the light source is triggered, delay the turn-on signal of the first switch tube, and control the gate drive voltage of the first switch tube during the delay period so that the first switch tube operates in the linear region.

8. The switching power supply circuit according to claim 6, wherein: The main power supply circuit further includes a second switch tube for controlling the charging of the load capacitor; and the control module is further configured to: If the second driving current is greater than or equal to the first driving current, then when the falling edge of the light source start signal is triggered, the PWM signal is output to the second switch tube within a third preset time to control the charging of the load capacitor; the third preset time is less than the spoke time of the color wheel.

9. The switching power supply circuit according to any one of claims 6 to 8, wherein: The main power supply circuit includes a first switching tube, a second switching tube, a load capacitor, an inductor and a diode; one end of the inductor is connected to the power supply, and the other end is connected to the positive electrode of the diode; the negative electrode of the diode is connected to the first end of the load capacitor; the drain of the second switching tube is connected between the inductor and the diode, the source is grounded, and the gate is connected to the control module; the first end of the load capacitor is also used to connect to one end of the light source, and the second end is connected to the source of the second switching tube; the drain of the first switching tube is used to connect to the other end of the light source, the source is connected to the second end of the load capacitor, and the gate is connected to the control module.

10. A projection device, characterized in that: The projector comprises the switching power supply circuit according to any one of claims 6 to 9; the projector further comprises: a light source electrically connected to the switching power supply circuit; and The color wheel is located in the optical path of the light source.

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