Light source driving circuit and projection device using the same

Abstract

The present application provides a projection device, comprising: a plurality of light source modules, and a plurality of light source driving circuits respectively coupled to and driving the plurality of light source modules. Each light source driving circuit comprises: a light source driving unit coupled to and driving a light source module, the light source driving unit receiving and being controlled by a gate signal and a pulse width modulation signal, the pulse width modulation signal controlling the size of a driving current outputted by the light source driving unit to the light source module; and a delay circuit coupled to the light source driving unit, the delay circuit controlling the gate signal according to the adjustment node voltage to determine when to release the gate signal, wherein the plurality of delay circuits of the plurality of light source driving circuits release the gate signal synchronously, so that the plurality of light source driving circuits output the plurality of driving currents to the plurality of light source modules synchronously.

Description

Technical Field

[0001] This invention relates to projection devices, and more particularly to a laser diode light source driving circuit and a projection device using the same. Background Technology

[0002] Projection devices, such as but not limited to projectors or projection televisions, are increasingly used in people's daily lives to achieve a high-quality audio-visual experience.

[0003] High-end projection devices (such as projection TVs) typically use red (R) / green (G) / blue (B) laser diodes (LDs) as their light source. These high-end devices require multiple LD light source modules, which may be connected in parallel or series. Because high-end projection devices require multiple LD light source modules, they also require multiple LD light source driver circuits, with each circuit driving one LD light source module.

[0004] However, due to the significant differences in characteristics between R, G, and B laser diode light source modules, the compensation adjustments of their driving circuits also differ greatly, requiring different compensation capacitors for each. These different capacitors cause the startup timing of the R, G, and B laser diode driving circuits to become asynchronous. Therefore, when the projector starts projecting an image, especially when it is powered on, viewers may see a poorly mixed startup image. For example, the image may initially display the red component, then the cyan component (a mixture of green and blue), and finally white (a mixture of R, G, and B colors), negatively impacting the viewer's entertainment experience. Summary of the Invention

[0005] The purpose of this invention is to provide a light source driving circuit and a projection device using it, which can synchronize the startup timing of all laser diode light source driving circuits even with different compensation capacitors. Therefore, when the projection device is turned on, the viewer will not see a poorly mixed startup screen, thus improving the viewer's entertainment experience.

[0006] To achieve the above objectives, the present invention provides a projection device comprising: a plurality of light source modules; and a plurality of light source driving circuits, wherein the plurality of light source driving circuits are respectively coupled to and drive the plurality of light source modules, and each of the light source driving circuits includes:

[0007] A light source driving unit is coupled to and drives the light source module. This unit receives an input voltage and is controlled by an enable signal, which controls whether the unit operates. It also receives and is controlled by a gating signal, which controls the timing of the drive current output from the unit to the light source module. Furthermore, the unit receives and is controlled by a pulse width modulation (PWM) signal, which controls the magnitude of the drive current output. A voltage conversion circuit is coupled to both the light source driving unit and the light source module. This circuit converts the input voltage and outputs it to the light source module. The voltage conversion circuit also feeds back the driving voltage of the light source module to the light source driving unit, so that the light source driving unit can perform constant current control on the driving current output to the light source module; the hysteresis comparator circuit is coupled to the light source driving unit, and the hysteresis comparator circuit controls the enable signal according to the adjustment node voltage to determine whether to release the enable signal; and the delay circuit is coupled to the light source driving unit, and the delay circuit controls the gating signal according to the adjustment node voltage to determine when to release the gating signal; wherein, the multiple delay circuits of the multiple light source driving circuits release the gating signal synchronously, so that the multiple light source driving circuits synchronously output multiple driving currents to multiple light source modules.

[0008] Preferably, based on the maximum compensation capacitor in the plurality of light source driving circuits, the plurality of delay circuits of the plurality of light source driving circuits determine when to synchronously release the gating signal.

[0009] Preferably, each of the light source modules includes multiple laser diodes.

[0010] Preferably, the hysteresis comparator circuit includes a first hysteresis comparator unit, a second hysteresis comparator unit, a first switching transistor, and a diode; the first hysteresis comparator unit receives the adjustment node voltage and a first reference voltage, and inputs an output signal to the second hysteresis comparator unit; the second hysteresis comparator unit receives the output signal of the first hysteresis comparator unit and the second reference voltage, and inputs an output signal to the first switching transistor to control the first switching transistor to turn on or off; the first switching transistor has: a first terminal connected to a ground terminal; a second terminal coupled to the diode; and a control terminal receiving the output signal of the second hysteresis comparator unit; and the diode is coupled between the enable signal and the second terminal of the first switching transistor.

[0011] Preferably, when the adjustment node voltage is less than the first reference voltage, the first hysteresis comparator outputs a high level to the second hysteresis comparator, causing the second hysteresis comparator to output a high level to turn on the first switching transistor and turn on the diode, thereby pulling down the enable signal and preventing the light source driving unit from operating. The adjustment node voltage is charged by the pulse width modulation signal and gradually rises. When the adjustment node voltage is equal to or greater than the first reference voltage, the first hysteresis comparator outputs to the second hysteresis comparator, causing the second hysteresis comparator to output a low level to the first switching transistor to turn it off. When the first switching transistor is off, the diode is turned off, the hysteresis comparator circuit releases the enable signal, and in response to the enable signal in the enabled state, the light source driving unit starts operating.

[0012] Preferably, the delay circuit includes: a second switching transistor, a third switching transistor, and a resistor-capacitor circuit; the second switching transistor is coupled to the adjustment node voltage through the resistor-capacitor circuit; the third switching transistor is coupled to the gating signal; and the resistor-capacitor circuit is coupled to the adjustment node voltage.

[0013] Preferably, when the voltage across the capacitor in the resistor-capacitor circuit is insufficient to turn on the second switching transistor, the adjustment node voltage turns on the third switching transistor to pull the gating signal low; when the voltage across the capacitor in the resistor-capacitor circuit is sufficient to turn on the second switching transistor, the third switching transistor turns off to release the gating signal, wherein the time required for the second switching transistor to turn on is greater than the settling time of the voltage across the maximum compensation capacitor.

[0014] Based on the above objectives, the present invention also proposes a light source driving circuit coupled to and driving a light source module. The light source driving circuit includes: a light source driving unit coupled to and driving the light source module; the light source driving unit receiving an input voltage; the light source driving unit receiving and being controlled by an enable signal, the enable signal controlling whether the light source driving unit operates; the light source driving unit also receiving and being controlled by a gating signal, the gating signal controlling the timing of a driving current output by the light source driving unit to the light source module; and the light source driving unit receiving and being controlled by a pulse width modulation signal, the pulse width modulation signal controlling the driving current output by the light source driving unit to the light source module. The system includes: a voltage conversion circuit coupled to the light source driving unit and the light source module; a voltage conversion circuit that converts the input voltage and outputs it to the light source module; a voltage conversion circuit that also feeds back the driving voltage of the light source module to the light source driving unit so that the light source driving unit can perform constant current control on the driving current output to the light source module; a hysteresis comparator circuit coupled to the light source driving unit that controls the enable signal based on the adjustment node voltage to determine when to release the enable signal; and a delay circuit coupled to the light source driving unit that controls the gating signal based on the adjustment node voltage to determine when to release the gating signal.

[0015] Preferably, the delay circuit determines when to synchronously release the gating signal based on the compensation capacitor of the light source driving circuit.

[0016] Preferably, the light source module includes multiple laser diodes.

[0017] Preferably, the hysteresis comparator circuit includes a first hysteresis comparator unit, a second hysteresis comparator unit, a first switching transistor, and a diode; the first hysteresis comparator unit receives the adjustment node voltage and a first reference voltage, and inputs an output signal to the second hysteresis comparator unit; the second hysteresis comparator unit receives the output signal of the first hysteresis comparator unit and the second reference voltage, and inputs an output signal to the first switching transistor to control the first switching transistor to turn on or off; the first switching transistor has: a first terminal connected to a ground terminal; a second terminal coupled to the diode; and a control terminal receiving the output signal of the second hysteresis comparator unit; and the diode is coupled between the enable signal and the second terminal of the first switching transistor.

[0018] Preferably, when the adjustment node voltage is less than the first reference voltage, the first hysteresis comparator outputs a high level to the second hysteresis comparator, causing the second hysteresis comparator to output a high level to turn on the first switching transistor and turn on the diode, thereby pulling down the enable signal and preventing the light source driving unit from operating. The adjustment node voltage is charged by the pulse width modulation signal and gradually rises. When the adjustment node voltage is equal to or greater than the first reference voltage, the first hysteresis comparator outputs a low level to the second hysteresis comparator, causing the second hysteresis comparator to output a low level to the first switching transistor to turn it off. When the first switching transistor is off, the diode is turned off, the hysteresis comparator circuit releases the enable signal, and in response to the enable signal in the enabled state, the light source driving unit starts to operate.

[0019] Preferably, the delay circuit includes: a second switching transistor, a third switching transistor, and a resistor-capacitor circuit; the second switching transistor is coupled to the adjustment node voltage through the resistor-capacitor circuit; the third switching transistor is coupled to the gating signal; and the resistor-capacitor circuit is coupled to the adjustment node voltage.

[0020] Preferably, when the voltage across the capacitor in the resistor-capacitor circuit is insufficient to turn on the second switching transistor, the adjustment node voltage turns on the third switching transistor to pull the gating signal low; when the voltage across the capacitor in the resistor-capacitor circuit is sufficient to turn on the second switching transistor, the third switching transistor is turned off to release the gating signal, wherein the time required for the second switching transistor to turn on is greater than the settling time of the voltage across the compensation capacitor.

[0021] Compared with the prior art, the light source driving circuit and the projection device using it proposed in this invention enable each light source driving unit in advance by setting up a delay circuit and a hysteresis comparison circuit, and enable the gating signal of each light source driving circuit to be delayed and emitted synchronously with the enable signal, thereby providing driving current to each light source module synchronously, illuminating each light source module synchronously, and eliminating the color mixing problem that exists when the projection device starts to project the image. Attached Figure Description

[0022] Figure 1 A functional block diagram of a projection device according to an embodiment of the present invention is shown.

[0023] Figure 2 This invention illustrates a light source driving circuit and a light source module according to an embodiment of the present invention.

[0024] Figure 3 Display the signal waveform of the hysteresis comparator.

[0025] Figure 4This is a signal waveform diagram according to an embodiment of the present invention. Detailed Implementation

[0026] The technical terms used in this specification refer to those commonly used in the field. Where this specification provides explanations or definitions for certain terms, the interpretation of those terms shall be based on the explanations or definitions provided in this specification. Each embodiment of the present invention has one or more technical features. Where feasible, those skilled in the art may selectively implement some or all of the technical features in any embodiment, or selectively combine some or all of the technical features in these embodiments.

[0027] Please refer to Figure 1 The diagram illustrates a functional block diagram of a projection device according to an embodiment of the present invention. The projection device 100 includes a plurality of light source driving circuits 110 and a plurality of light source modules 120. The plurality of light source driving circuits 110 are respectively coupled to and drive the plurality of light source modules 120. Here, the light source driving circuits 110 and light source modules 120 are described as laser diode light source driving circuits and laser diode light source modules, respectively, but it should be understood that the present invention is not limited thereto. One set of light source driving circuits 110 can drive one set of light source modules 120. For example, where possible, the projection device 100 includes 6 sets of light source driving circuits 110 and 6 sets of light source modules 120, wherein 2 sets of light source modules 120 are red (R) laser diode light source modules, 3 sets of light source modules 120 are green (G) laser diode light source modules, and 1 set of light source modules 120 is a blue (B) laser diode light source module.

[0028] Figure 2 This illustrates a light source driving circuit 110 and a light source module 120 according to an embodiment of the present invention. For example... Figure 2 As shown, the light source driving circuit 110 includes: a light source driving unit 210, a voltage conversion circuit 220, a hysteresis comparator circuit 230, and a delay circuit 240. The light source module 120 includes multiple laser diodes (LDs) connected in series.

[0029] The light source driving unit 210 is, for example, but not limited to, a laser diode driver integrated circuit (IC). The architecture of the light source driving unit 210 is not particularly limited herein. The light source driving unit 210 is coupled to the light source module 120 to drive the light source module 120. The light source driving unit 210 receives an input voltage VIN as an operating voltage source.

[0030] The light source driving unit 210 receives and is controlled by the enable signal EN, which is also controlled by the hysteresis comparator circuit 230. That is, even if the enable signal EN sent from an external source (not shown) is in an enabled state (e.g., but not limited to logic high), the light source driving unit 210 remains inactive when the enable signal EN is controlled by the hysteresis comparator circuit 230 to be in a disabled state (e.g., but not limited to logic low). The light source driving unit 210 only begins to operate in response to the enabled signal EN being in an enabled state when the enable signal EN is released by the hysteresis comparator circuit 230 (i.e., not controlled, or meaning, not further pulled low, so that the enable signal received by the light source driving unit 210 is consistent with the externally sent enable signal EN). In other words, the enable signal EN controls whether the light source driving unit 210 operates.

[0031] The light source driving unit 210 receives and is controlled by the gating signal S. The gating signal S controls the waveform timing of the driving current output by the light source driving unit 210 to the light source module 120; that is, the gating signal S is a synchronization signal for the driving current. The gating signal S can also be controlled by the delay circuit 240. That is, even if the gating signal S sent from the outside (not shown) is in an enabled state, but is disabled by the delay circuit 240, the light source driving unit 210 will not output driving current. The light source driving unit 210 will only start outputting driving current to the light source module 120 when the gating signal S is released by the delay circuit 240 (i.e., not controlled, or not pulled low, so that the gating signal received by the light source driving unit 210 is consistent with the externally sent gating signal S).

[0032] The light source driving unit 210 receives and is controlled by the pulse width modulation (PWM) signal PWM, which can control the magnitude of the driving current output by the light source driving unit 210 to the light source module 120.

[0033] like Figure 2 As shown, the light source driving circuit 110 also includes resistors R1 and R2, and capacitors C1 to C3. Resistor R1 and capacitor C1 are connected in series, and the voltage at the coupling node between resistor R1 and capacitor C1 is called the adjustment node voltage Vadj. The pulse width modulation (PWM) signal is input to the light source driving unit 210 through resistor R1. The compensation pin COMP of the light source driving unit 210 is also coupled to capacitor C2, resistor R2, and capacitor C3. The capacitance value of capacitor C2 is related to the system stability, and capacitor C2 can also be called a compensation capacitor. Because the module characteristics of the R / G / B light source modules 120 are different, the capacitance value of capacitor C2 varies, ranging from as high as 10μF to as low as 22nF.

[0034] In conventional technology, the capacitance value of capacitor C2 affects the timing of the output drive current of the light source module. Therefore, the timing of the output drive current of conventional R / G / B light source modules is different, which may cause poor R / G / B color mixing when the system is turned on, thus reducing the viewer's viewing experience.

[0035] A voltage conversion circuit 220 is coupled to the light source driving unit 210 and the light source module 120. The voltage conversion circuit 220 converts the input voltage VIN and outputs it to the light source module 120. The architecture and operation of the voltage conversion circuit 220 are not particularly limited herein. In one possible embodiment of the invention, the voltage conversion circuit 220 may be a buck converter, but the invention is not limited thereto. In other possible embodiments of the invention, the voltage conversion circuit 220 may be other types of voltage conversion circuits, all of which are within the spirit and scope of the invention. Furthermore, the voltage conversion circuit 220 may also feed back the driving voltage of the light source module 120 to the light source driving unit 210, allowing the light source driving unit 210 to perform constant current control on the driving current output to the light source module 120.

[0036] In this embodiment, the delay circuit 240 is coupled to the light source driving unit 210. The delay circuit 240 controls the gating signal S according to the adjustment node voltage Vadj. That is, the delay circuit 240 determines when to release the gating signal S according to the adjustment node voltage Vadj, so that the waveform timing of the driving current output by the light source driving unit 210 to the light source module 120 is controlled by the gating signal S. The multiple delay circuits 240 of the multiple light source driving circuits 110 release the gating signal S synchronously, so that the multiple light source driving circuits 110 synchronously output the multiple driving currents to the multiple light source modules 110.

[0037] In a preferred embodiment, the hysteresis comparator circuit 230 is coupled to the light source driving unit 210. The hysteresis comparator circuit 230 controls the enable signal EN based on the adjustment node voltage Vadj; that is, the hysteresis comparator circuit 230 determines whether to release (not control) the enable signal EN based on the adjustment node voltage Vadj. The release time of the enable signal EN is earlier than the release time of the strobe signal S. In other embodiments, the light source driving circuit 110 does not include the hysteresis comparator circuit 230, that is, it does not control or manage the release of the externally input enable signal EN.

[0038] The details of how the hysteresis comparator circuit 230 controls the enable signal EN and the delay circuit 240 controls the gating signal S in the preferred embodiment of the present invention will now be explained.

[0039] like Figure 2As shown, the hysteresis comparator circuit 230 includes a first hysteresis comparator unit 231, a second hysteresis comparator unit 232, a first switching transistor Q1, resistors R3 to R5, and a diode D.

[0040] The two input terminals of the first hysteresis comparator 231 receive the adjustment node voltage Vadj and the first reference voltage VREF1, respectively, and input an output signal to the second hysteresis comparator 232. For example, but not limited to, the positive and negative input terminals of the internal operational amplifier (not shown) of the first hysteresis comparator 231 receive the adjustment node voltage Vadj and the first reference voltage VREF1, respectively. The first reference voltage VREF1 is, for example, but not limited to, 3.3V.

[0041] The two input terminals of the second hysteresis comparator 232 receive the output signal of the first hysteresis comparator 231 and the second reference voltage VREF2, respectively, and input an output signal to the control terminal of the first switching transistor Q1. For example, but not limited to, the positive and negative input terminals of the internal operational amplifier (not shown) of the second hysteresis comparator 232 receive the output signal of the first hysteresis comparator 231 and the second reference voltage VREF2, respectively. The second reference voltage VREF2 is, for example, but not limited to, 3.3V.

[0042] The architecture of the first hysteresis comparator unit 231 and the second hysteresis comparator unit 232 is not particularly limited. For example, each of the first hysteresis comparator unit 231 and the second hysteresis comparator unit 232 includes an amplifier comparator and several resistors, capacitors, etc.

[0043] The first switching transistor Q1 has: a first terminal (e.g., the source) connected to ground; a second terminal (e.g., the drain) coupled to diode D; and a control terminal (e.g., the gate) receiving the output signal of the second hysteresis comparator 232.

[0044] Diode D is coupled between the enable signal EN and the second terminal of the first switching transistor Q1.

[0045] Resistor R3 is coupled between the operating voltage and the control terminal of the first switching transistor Q1. Resistor R4 is coupled between the operating voltage and the second terminal of the first switching transistor Q1. Resistor R5 is coupled between the control terminal and the first terminal of the first switching transistor Q1.

[0046] The delay circuit 240 includes: a second switching transistor Q2, a third switching transistor Q3, resistors R6 and R7, and capacitor C4. Resistors R6, R7, and capacitor C4 can also be collectively referred to as a resistor-capacitor circuit.

[0047] The second switching transistor Q2 has: a first terminal (e.g., the source) connected to the ground terminal; a second terminal (e.g., the drain) coupled to the control terminal of the third switching transistor Q3; and a control terminal (e.g., the gate) coupled to the coupling point of resistor R6 and capacitor C4.

[0048] The third switching transistor Q3 has: a first terminal (e.g., the source) connected to ground; a second terminal (e.g., the drain) coupled to a strobe signal S; and a control terminal (e.g., the gate) coupled to the second terminal of the second switching transistor Q2.

[0049] Resistor R6 is coupled between the adjustment node voltage Vadj and the control terminal of the second switching transistor Q2. Resistor R7 is coupled between the adjustment node voltage Vadj and the control terminal of the third switching transistor Q3. Capacitor C4 is coupled between the control terminal of the second switching transistor Q2 and the ground terminal.

[0050] Figure 3 The signal waveform diagram of the hysteresis comparator in the above embodiment is shown. As is known, when the input voltage Vi of the hysteresis comparator rises and reaches the first critical voltage value VTH, the output voltage Vo of the hysteresis comparator changes from a high output voltage Vz to a low output voltage -Vz. When the input voltage Vi of the hysteresis comparator falls and reaches the second critical voltage value VTL, the output voltage Vo of the hysteresis comparator changes from a low output voltage -Vz to a high output voltage Vz.

[0051] Figure 4 This is a signal waveform diagram according to an embodiment of the present invention. Please refer to it as well. Figures 2 to 4 .

[0052] Before timing T1, the adjustment node voltage Vadj is still less than the first reference voltage VREF1. Therefore, the first hysteresis comparator 231 outputs a positive voltage to the second hysteresis comparator 232. When the first hysteresis comparator 231 is still outputting a positive voltage, the second hysteresis comparator 232 is also outputting a positive voltage through resistor / capacitor design. When the second hysteresis comparator 232 outputs a positive voltage, the first switching transistor Q1 is turned on. The turn on of the first switching transistor Q1 causes the diode D to turn on, pulling down the enable signal EN, so that the light source driving unit 210 does not operate.

[0053] In one embodiment of the present invention, the adjustment node voltage Vadj is charged by the pulse width modulation signal PWM and gradually increases.

[0054] At timing T1, the adjustment node voltage Vadj is equal to or greater than the first reference voltage VREF1. Therefore, the first hysteresis comparator 231 outputs a voltage of 0 to the positive input of the internal operational amplifier (not shown) of the second hysteresis comparator 232. Since the negative input of the internal operational amplifier (not shown) of the second hysteresis comparator 232 receives the second reference voltage VREF2 (e.g., but not limited to 3.3V), the second hysteresis comparator 232 outputs a voltage of 0 to the control terminal of the first switching transistor Q1, causing the first switching transistor Q1 to be turned off. When the first switching transistor Q1 is turned off, the diode D is turned off. Therefore, the hysteresis comparator circuit 230 cannot continue to pull the enable signal EN low, that is, it releases the enable signal EN. Therefore, in response to the enable signal EN (at timing T1), which is in the enabled state, the light source driving unit 210 starts to operate.

[0055] Following timing T1, the adjustment node voltage Vadj is continuously charged by the pulse width modulation signal PWM and gradually increases. Similarly, the voltage across capacitor C4 also gradually increases. In one embodiment of the present invention, by designing the values ​​of resistor R6 and capacitor C4, the voltage across capacitor C4 between timing T1 and timing T2 is insufficient to turn on the second switching transistor Q2. In response to the adjustment node voltage Vadj at this time, the third switching transistor Q3 is turned on. When the third switching transistor Q3 is turned on, the gating signal S is pulled low, that is, the light source driving unit 210 still does not output driving current to the light source module 120.

[0056] Subsequently, by designing the values ​​of resistor R6 and capacitor C4, at timing T2, the voltage across capacitor C4 is sufficient to turn on the second switching transistor Q2 (the voltage across capacitor C4 is greater than the critical voltage of the second switching transistor Q2). Since the second switching transistor Q2 is turned on, the control terminal of the third switching transistor Q3 is pulled low, causing the third switching transistor Q3 to be off. When the third switching transistor Q3 is off, it is impossible to continue pulling the gating signal S low, i.e., the gating signal S is released. Therefore, the gating signal S, which is in the enabled state, can control the light source driving unit 210 to output driving current to the light source module 120.

[0057] In one embodiment of the present invention, the charging time of the control resistor R6 and capacitor C4 is such that the time required for all second switching transistors Q2 to turn on (i.e., timing T2) is greater than the time required for the voltage across the maximum compensation capacitor C2 to reach a stable value. Here, the maximum compensation capacitor C2 refers to the largest capacitance value among all capacitors C2 of the plurality of light source driving modules 110. In this way, when the voltage across capacitor C4 reaches the critical voltage of the second switching transistor Q2, all light source driving modules 110 can synchronously receive the released gating signal S. That is, based on the maximum compensation capacitor of the plurality of light source driving circuits 110, the plurality of delay circuits 240 of the plurality of light source driving circuits 110 determine when to synchronously release the gating signal S, so that all light source driving modules 110 synchronously output driving current to the individual light source modules 120, allowing all light source modules 120 to emit light synchronously. Therefore, in one embodiment of the present invention, when the projection device 100 system is turned on, all the light source modules 120 can emit light synchronously, so the viewer can see a well-mixed startup screen, which can improve the viewer's entertainment effect.

[0058] In other embodiments, the enable state of the enable signal EN can also be logic low. In this case, the corresponding hysteresis comparator circuit 230 outputs a high level to control the enable signal EN, and outputs a low level to release the enable signal EN. The specific circuit composition will not be described in detail here.

[0059] In other embodiments, the enable state of the strobe signal S can also be logic low. In this case, the corresponding delay circuit 240 outputs a high level to control the strobe signal S, and outputs a low level to release the strobe signal S. The specific circuit composition will not be described in detail here.

[0060] In summary, the light source driving circuit and projection device using the present invention, through the setting of delay circuit and hysteresis comparison circuit, enable each light source driving unit in advance, and enable the gating signal of each light source driving circuit to be delayed and emitted synchronously with the enable signal, thereby providing driving current to each light source module synchronously, illuminating each light source module synchronously, eliminating the color mixing problem that exists when the projection device starts projecting the image, and improving the entertainment effect for the viewer.

[0061] The present invention has been described in the above-described embodiments; however, these embodiments are merely examples for implementing the present invention. It must be noted that the disclosed embodiments do not limit the scope of the present invention. Conversely, any modifications and refinements made without departing from the spirit and scope of the present invention are within the scope of patent protection of the present invention.

Claims

1. A projection device, characterized in that, include: Multiple light source modules; as well as, Multiple light source driving circuits are coupled to and drive the multiple light source modules respectively. Each light source driving circuit includes: A light source driving unit is coupled to and drives the light source module. The light source driving unit receives an input voltage and is controlled by an enable signal, which controls whether the light source driving unit operates. The light source driving unit also receives and is controlled by a gating signal, which controls the timing of the drive current output by the light source driving unit to the light source module. The light source driving unit receives and is controlled by a pulse width modulation signal, which controls the magnitude of the drive current output by the light source driving unit to the light source module. A voltage conversion circuit is coupled to the light source driving unit and the light source module. The voltage conversion circuit converts the input voltage and outputs it to the light source module. The voltage conversion circuit also feeds back the drive voltage of the light source module to the light source driving unit, allowing the light source driving unit to perform constant current control on the drive current output to the light source module. A hysteresis comparator circuit, coupled to the light source driving unit, controls the enable signal based on the adjustment node voltage to determine whether to release the enable signal; and A delay circuit, coupled to the light source driving unit, controls the gating signal based on the adjustment node voltage to determine when to release the gating signal. In this process, the multiple delay circuits of the multiple light source driving circuits simultaneously release the gating signal, so that the multiple light source driving circuits simultaneously output multiple driving currents to the multiple light source modules.

2. The projection device as described in claim 1, characterized in that: Based on the maximum compensation capacitance in the plurality of light source driving circuits, the plurality of delay circuits of the plurality of light source driving circuits determine when to synchronously release the gating signal.

3. The projection device as claimed in claim 1, wherein, Each of these light source modules includes multiple laser diodes.

4. The projection device as described in claim 1, characterized in that: The hysteresis comparator circuit includes a first hysteresis comparator unit, a second hysteresis comparator unit, a first switching transistor, and a diode; The first hysteresis comparison unit receives the adjustment node voltage and the first reference voltage, and inputs the output signal to the second hysteresis comparison unit; The second hysteresis comparator receives the output signal of the first hysteresis comparator and the second reference voltage, and inputs the output signal to the first switching transistor to control the first switching transistor to turn on or off; The first switching transistor has: a first terminal connected to a ground terminal; a second terminal coupled to the diode; and a control terminal that receives the output signal of the second hysteresis comparator unit. as well as The diode is coupled between the enable signal and the second terminal of the first switching transistor.

5. The projection device as described in claim 4, characterized in that: When the voltage of the adjustment node is less than the first reference voltage, the first hysteresis comparator outputs a high level to the second hysteresis comparator, so that the second hysteresis comparator outputs a high level to turn on the first switching transistor and turn on the diode to pull down the enable signal, so that the light source driving unit does not operate. The voltage at the adjustment node is charged by the pulse width modulation signal and gradually increases; When the voltage of the adjustment node is equal to or greater than the first reference voltage, the first hysteresis comparator outputs to the second hysteresis comparator, causing the second hysteresis comparator to output a low level to the first switching transistor to turn off the first switching transistor. When the first switching transistor is off, the diode is turned off, and the hysteresis comparator circuit releases the enable signal. In response to the enable signal in the enabled state, the light source driving unit starts to operate.

6. The projection device as described in claim 5, characterized in that: The delay circuit includes: a second switching transistor, a third switching transistor, and a resistor-capacitor circuit; The second switching transistor is coupled to the adjustment node voltage through the resistor-capacitor circuit; The third switching transistor is coupled to the gating signal; and The resistor-capacitor circuit is coupled to the voltage of the adjustment node.

7. The projection device as described in claim 6, characterized in that: When the voltage across the capacitor in the resistor-capacitor circuit is insufficient to turn on the second switching transistor, the adjustment node voltage turns on the third switching transistor to pull the gating signal low. When the voltage across the capacitor in the resistor-capacitor circuit is sufficient to turn on the second switching transistor, the third switching transistor turns off to release the gating signal. The time required for the second switching transistor to turn on is greater than the voltage stabilization time of the maximum compensation capacitor.

8. A light source driving circuit, coupled to and driving a light source module, characterized in that: The light source driving circuit includes: A light source driving unit is coupled to and drives the light source module. The light source driving unit receives an input voltage and is controlled by an enable signal, which controls whether the light source driving unit operates. The light source driving unit also receives and is controlled by a gating signal, which controls the timing of a driving current output by the light source driving unit to the light source module. The light source driving unit receives and is controlled by a pulse width modulation signal, which controls the magnitude of the driving current output by the light source driving unit to the light source module. A voltage conversion circuit is coupled to the light source driving unit and the light source module. The voltage conversion circuit converts the input voltage and outputs it to the light source module. The voltage conversion circuit also feeds back the driving voltage of the light source module to the light source driving unit so that the light source driving unit can perform constant current control on the driving current output to the light source module. A hysteresis comparator circuit, coupled to the light source driving unit, controls the enable signal based on the adjustment node voltage to determine when to release the enable signal; and A delay circuit, coupled to the light source driving unit, controls the gating signal based on the adjustment node voltage to determine when to release the gating signal.

9. The light source driving circuit as described in claim 8, characterized in that: Based on the compensation capacitor of the light source driving circuit, the delay circuit determines when to synchronously release the gating signal.

10. The light source driving circuit as described in claim 8, characterized in that: The light source module includes multiple laser diodes.

11. The light source driving circuit as described in claim 8, characterized in that: The hysteresis comparator circuit includes a first hysteresis comparator unit, a second hysteresis comparator unit, a first switching transistor, and a diode; The first hysteresis comparison unit receives the adjustment node voltage and the first reference voltage, and inputs the output signal to the second hysteresis comparison unit; The second hysteresis comparator receives the output signal of the first hysteresis comparator and the second reference voltage, and inputs the output signal to the first switching transistor to control the first switching transistor to turn on or off; The first switching transistor has: a first terminal connected to a ground terminal; a second terminal coupled to the diode; and a control terminal that receives the output signal of the second hysteresis comparator unit. as well as The diode is coupled between the enable signal and the second terminal of the first switching transistor.

12. The light source driving circuit as described in claim 11, characterized in that: When the voltage of the adjustment node is less than the first reference voltage, the first hysteresis comparator outputs a high level to the second hysteresis comparator, so that the second hysteresis comparator outputs a high level to turn on the first switching transistor and turn on the diode to pull down the enable signal, so that the light source driving unit does not operate. The voltage at the adjustment node is charged by the pulse width modulation signal and gradually increases; When the voltage of the adjustment node is equal to or greater than the first reference voltage, the first hysteresis comparator outputs a low level to the second hysteresis comparator, causing the second hysteresis comparator to output a low level to the first switching transistor to turn off the first switching transistor. When the first switching transistor is off, the diode is turned off, and the hysteresis comparator circuit releases the enable signal. In response to the enable signal in the enabled state, the light source driving unit starts to operate.

13. The light source driving circuit as described in claim 12, characterized in that: The delay circuit includes: a second switching transistor, a third switching transistor, and a resistor-capacitor circuit; The second switching transistor is coupled to the adjustment node voltage through the resistor-capacitor circuit; The third switching transistor is coupled to the gating signal; and The resistor-capacitor circuit is coupled to the voltage of the adjustment node.

14. The light source driving circuit as described in claim 13, characterized in that: When the voltage across the capacitor in the resistor-capacitor circuit is insufficient to turn on the second switching transistor, the adjustment node voltage turns on the third switching transistor to pull the gating signal low. When the voltage across the capacitor in the resistor-capacitor circuit is sufficient to turn on the second switching transistor, the third switching transistor is turned off to release the gating signal. The time required for the second switching transistor to turn on is greater than the voltage stabilization time of the compensation capacitor.

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