CN111198470B

CN111198470B - Projection system, driving device and driving method

Info

Publication number: CN111198470B
Application number: CN201811273930.9A
Authority: CN
Inventors: 陈振旺; 纪信维; 叶英杰
Original assignee: Coretronic Corp
Current assignee: Coretronic Corp
Priority date: 2018-10-30
Filing date: 2018-10-30
Publication date: 2022-03-18
Anticipated expiration: 2038-10-30
Also published as: CN111198470A

Abstract

The invention provides a projection system, a driving device and a driving method. The driving device is used for driving a light source module with a plurality of light-emitting elements connected in series. The driving device comprises a power supply circuit, a current controller and a voltage following circuit. The power circuit adjusts the output voltage according to the adjustment signal and drives the light source module by the output voltage. The current controller includes a switch. The current controller controls the switch to maintain a current value of the driving current flowing through the light source module at a preset driving current value, and provides a control signal according to energy consumed by the switch. The voltage tracking circuit provides an adjusting signal according to the control signal. Therefore, the projection system can have the driving device with lower deployment cost, and the driving device can not generate larger electromagnetic interference.

Description

Projection system, driving device and driving method

Technical Field

The present invention relates to a projection system, a driving apparatus and a driving method thereof, and more particularly, to a driving apparatus and a driving method thereof for driving a projection system having a plurality of light emitting elements connected in series.

Background

Currently, a projection system converts a fixed dc input power into a plurality of power sources to control a plurality of driving devices to drive a plurality of sets of light emitting elements. In other words, each group of light emitting devices needs to be driven by one driving device. Therefore, when the projection system needs more light emitting elements, the cost for disposing the driving device is increased. In addition, once the number of the driving devices is increased, the on/off switching of the switches inside the driving devices may increase the electromagnetic interference, thereby affecting the normal operation of the projection system.

The background section is only for the purpose of illustrating the present invention, and therefore the disclosure in the background section may include some known techniques that do not constitute a part of the knowledge of those skilled in the art. Furthermore, the disclosure in the "background" section is not intended to represent a material, or problem, which one or more embodiments of the present invention might solve, nor is it intended to be known or appreciated by those skilled in the art prior to filing this application.

Disclosure of Invention

The invention provides a projection system with only a single driving device, a driving device of a single switch and a driving method thereof. The projection system of the invention can have lower deployment cost of the driving device. In addition, the driving device of the invention only has one switch, so the driving device of the invention can not generate larger electromagnetic interference.

Other objects and advantages of the present invention will be further understood from the technical features disclosed in the present invention.

To achieve one or a part of or all of the above or other objects, the driving device of the present invention is used for driving a light source module having a plurality of light emitting elements connected in series. The driving device comprises a power supply circuit, a current controller and a voltage following circuit. The power circuit is coupled to the light source module for adjusting the output voltage according to the adjustment signal and driving the light source module by the output voltage. The current controller is coupled to the light source module and includes a switch, and the current controller is configured to control the switch to maintain a current value of the driving current flowing through the light source module at a preset driving current value and provide a control signal according to energy consumed by the switch. The voltage tracking circuit is coupled between the power circuit and the current controller for providing an adjustment signal according to the control signal.

To achieve one or a part of or all of the above or other objects, the projection system of the present invention includes a light source module and the driving device. The driving device is used for driving a light source module with a plurality of light-emitting elements, wherein the plurality of light-emitting sources are connected in series.

To achieve one or a part of or all of the above or other objects, the present invention further provides a driving method for driving a light source module having a plurality of light emitting elements connected in series. The driving method comprises the following steps: providing a switch, coupling the switch to the light source module; controlling the switch to maintain the current value of the driving current flowing through the light source module at a preset driving current value, and providing a control signal according to the energy consumed by the switch; providing an adjusting signal according to the control signal; and adjusting the output voltage according to the adjustment signal, and driving the light source module by the output voltage.

Based on the above, the embodiments of the invention have at least one of the following advantages or efficacies. In the projection system of the present invention, the driving device drives the light source module having the plurality of light emitting elements connected in series by the output voltage. The driving device controls the switch to maintain the current value of the driving current flowing through the light source module at a preset driving current value, provides a control signal according to the energy consumed by the switch, and adjusts the output voltage according to the adjustment signal. Therefore, the projection system can have lower deployment cost of the driving device. In addition, the driving device of the invention only has one switch, so the driving device of the invention can not generate larger electromagnetic interference.

In order to make the aforementioned and other features and advantages of the invention more comprehensible, embodiments accompanied with figures are described in detail below.

Drawings

Fig. 1 is a schematic view of a projection apparatus according to a first embodiment of the invention.

Fig. 2 is a schematic diagram of a current controller according to a first embodiment of the invention.

Fig. 3 is a schematic diagram of a first sensor and a switch according to a second embodiment of the invention.

Fig. 4 is a schematic diagram of a second sensor and a switch according to a third embodiment of the invention.

Fig. 5 is a schematic diagram of a voltage tracking circuit according to a first embodiment of the invention.

Fig. 6 is a schematic diagram of a voltage tracking circuit according to a fourth embodiment of the invention.

FIG. 7 is a diagram illustrating a projection system according to a fifth embodiment of the invention.

Fig. 8 is a flowchart illustrating a driving method according to an embodiment of the invention.

Detailed Description

The foregoing and other features, aspects and utilities of the present general inventive concept will be apparent from the following detailed description of a preferred embodiment thereof, which is to be read in connection with the accompanying drawings.

Referring to fig. 1, fig. 1 is a schematic view of a projection apparatus 10 according to a first embodiment of the invention. In this embodiment, the projection apparatus 10 is, for example, a projector, and the projection apparatus 10 includes a light source module LM and a driving apparatus 100. The light source module LM has light emitting elements LD _1 to LD _ n, and the light emitting elements LD _1 to LD _ n are connected in series with each other. The driving device 100 is used for driving the light source module LM. In the present embodiment, the Light emitting elements LD _1 to LD _ n may be implemented by, for example, a laser diode (laser diode), but not limited to, and may also be implemented by, for example, a Light Emitting Diode (LED), a bulb, or other Light sources. In the present embodiment, the driving apparatus 100 includes a power supply circuit 110, a current controller 120, and a voltage tracking circuit 130. The power circuit 110 is coupled to the light source module LM. The power circuit 110 adjusts the output voltage Vo according to the adjustment signal Sadj, and drives the light source module LM according to the output voltage Vo. The power circuit 110 of the present embodiment can be implemented by any type of power converter.

The current controller 120 is coupled to the light source module LM. Current controller 120 includes a switch SW. The current controller 120 controls the switch SW to maintain the current value of the driving current ID flowing through the light source module LM at the predetermined driving current value. In addition, the current controller 120 provides the control signal SC according to the energy consumed by the switch SW. That is, the switch SW is set to adjust the current value of the driving current ID, thereby fixing the current value of the driving current ID. The switch SW consumes energy corresponding to the adjustment result, and the current controller 120 provides the control signal SC based on the energy. The switch SW of this embodiment is implemented by a Metal Oxide Semiconductor Field Effect Transistor (MOSFET). In some embodiments, the switch SW may be implemented by a Bipolar Junction Transistor (BJT), a Silicon Controlled Rectifier (SCR), a thyristor (thyristor), or a triac. The preset driving current value of the present embodiment represents at least a rated current value sufficient for driving the light source module LM. It should be understood that the predetermined driving current value can be set to at least a value for maintaining the current value of the driving current ID at least a rated current value.

The voltage tracking circuit 130 is coupled between the power circuit 110 and the current controller 120. The voltage tracking circuit 130 is configured to receive the control signal SC and provide the adjustment signal Sadj according to the control signal SC.

It should be noted that the light source module LM has a plurality of light emitting elements LD _1 to LD _ n connected in series with each other. Therefore, unlike the conventional projection apparatus that requires a plurality of driving devices to drive a plurality of light source modules, the driving device 100 of the present embodiment only requires a single power circuit 110 to provide the output voltage Vo. In this way, the layout area (occupied space) of the driving device 100 required by the projection apparatus 10 of the embodiment can be greatly reduced, so that the volume of the projection apparatus 10 can be smaller, and the cost of the driving device 100 can be reduced. In addition, the current controller 120 controls the switch SW to maintain the current value of the driving current ID at the predetermined driving current value. Therefore, also in the case where the current value of the driving current ID is controlled by the current controller 120, the light source module LM is protected.

Specifically, referring to fig. 1 and fig. 2, fig. 2 is a schematic diagram of a current controller 120 according to a first embodiment of the invention. In the present embodiment, the current controller 120 includes a first sensor 122 and a second sensor 124 in addition to the switch SW. The switch SW has a first terminal, a second terminal, and a control terminal. The first terminal of the switch SW is coupled to the light source module LM. The first sensor 122 is coupled to the first end and the second end of the switch. The first sensor 122 is used for sensing a voltage difference between the first terminal and the second terminal of the switch to determine the control signal SC.

Further, the first sensor 122 includes at least a first operational amplifier OP 1. The first operational amplifier OP1 has a non-inverting input, an inverting input, and an output. The non-inverting input terminal of the first operational amplifier OP1 is coupled to the first terminal of the switch SW, and the inverting input terminal of the first operational amplifier OP1 is coupled to the second terminal of the switch SW. The non-inverting input terminal of the first operational amplifier OP1 is used for receiving the voltage value of the first terminal of the switch SW. The inverting input terminal of the first operational amplifier OP1 is used for receiving the voltage value of the second terminal of the switch SW. The first operational amplifier OP1 performs an operation, i.e. a subtraction, on the voltage value of the first terminal of the switch SW and the voltage value of the second terminal of the switch SW to obtain the control signal SC, and provides the control signal SC via the output terminal.

In the present embodiment, the second sensor 124 is coupled to the second end and the control end of the switch. The second sensor 124 receives the driving current ID from the second end of the switch, obtains the current sensing signal VS according to the current value of the driving current ID, and provides the current control signal SID to the control end of the switch SW according to the current sensing signal VS. The switch SW receives the current control signal SID through the control terminal, and changes the magnitude of the current value of the driving current ID according to the voltage level of the current control signal SID. For the present embodiment, the switch SW can operate in a linear region or a saturation region under the control of the second sensor 124. Therefore, the second sensor 124 can control the switch SW according to the current value of the driving current ID, so as to maintain the current value of the linear control driving current ID at the preset driving current value.

Further, the second sensor 124 at least includes a sensing resistor RS and a second operational amplifier OP 2. A first end of the sensing resistor RS is coupled to a second end of the switch SW, and a second end of the sensing resistor RS is coupled to a system low voltage (e.g., ground). The driving current ID flows through a resistor RS having a resistance value, and then generates a current sensing signal VS. The second operational amplifier OP2 has a non-inverting input, an inverting input, and an output. The non-inverting input terminal of the second operational amplifier OP2 is used for receiving a first reference voltage VREF 1. The inverting input terminal of the second operational amplifier OP2 is coupled to the first terminal of the sensing resistor RS. The inverting input terminal of the second operational amplifier OP2 receives the current sense signal VS from the sense resistor RS. The second operational amplifier OP2 receives the voltage value of the first reference voltage VREF1 and the voltage value of the current sensing signal VS for feedback operation, and then provides the current control signal SID from the output terminal to control the switch SW. Since the second sensor 124 and the switch SW form a negative feedback, and the voltage value of the first reference voltage VREF1 is a fixed voltage value, the voltage value of the current control signal SID and the voltage value of the current sensing signal VS are in a negative correlation. For example, when the current value of the driving current ID increases, the voltage of the current sense signal VS increases, and the voltage of the current control signal SID decreases, so as to linearly control the switch SW to decrease the current value of the driving current ID. For example, when the current value of the driving current ID decreases, the voltage value of the current sense signal VS decreases, and the voltage value of the current control signal SID increases, so as to linearly control the switch SW to increase the current value of the driving current ID. Thus, the current value of the driving current ID can be maintained at the predetermined driving current value.

It should be noted that the driving device linearly controls the switch SW via the second sensor 124, so that the current value of the driving current ID can be maintained at the predetermined driving current value. The driving device replaces the fast switching operation of the plurality of internal switches in the prior art by the linear control of the single switch SW by the second sensor 124. Therefore, the Electromagnetic Interference (EMI) generated by the fast switching operation of the plurality of internal switches can be reduced, and the cost required for coping with the EMI can be saved.

Referring to fig. 3, fig. 3 is a schematic diagram of a first sensor 222 and a switch SW according to a second embodiment of the invention. Compared to the embodiment of fig. 2, the first sensor 222 of the second embodiment further includes resistors R1-R4 and a capacitor C1 in addition to the first operational amplifier OP 1. The resistor R1 is coupled between the non-inverting input terminal of the first operational amplifier OP1 and the first terminal of the switch SW. The resistor R2 and the capacitor C1 are respectively coupled between the non-inverting input terminal of the first operational amplifier OP1 and a system low voltage (e.g., ground). The resistor R2 and the capacitor C1 are used to stabilize the voltage value of the non-inverting input terminal of the first operational amplifier OP1 and filter the noise from the light source module LM. The resistor R3 is coupled between the inverting input terminal of the first operational amplifier OP1 and the second terminal of the switch SW. The resistor R4 is coupled between the inverting input terminal of the first operational amplifier OP1 and the output terminal of the first operational amplifier OP 1. It is understood that the first operational amplifier OP1 can adjust the operation result of the first operational amplifier OP1 by setting the resistance of the resistors R1-R4.

Referring to fig. 4, fig. 4 is a schematic diagram of a second sensor 224 and a switch SW according to a third embodiment of the invention. The second sensor 224 of the third embodiment comprises a sensing resistor RS, a second operational amplifier OP2 and a gain circuit 2242. The gain circuit 2242 is coupled between the second operational amplifier OP2 and the sensing resistor RS. The gain circuit 2242 gains the current sense signal VS from the sense resistor RS and provides the gain current sense signal VS to the inverting input terminal of the second operational amplifier OP 2. The gain circuit 2242 includes an operational amplifier OP3 and resistors R5 and R6. The non-inverting input terminal of the operational amplifier OP3 is coupled to the first terminal of the sensing resistor RS, and the non-inverting input terminal of the operational amplifier OP3 is used for receiving the current sensing signal VS. The inverting input terminal of the operational amplifier OP3 is coupled to the second terminal of the sensing resistor RS via the resistor R5, and the output terminal of the operational amplifier OP3 is coupled to the inverting input terminal of the second operational amplifier OP2 and to the inverting input terminal of the operational amplifier OP3 via the resistor R5. The gain circuit 2242 can gain the sensing signal VS according to the resistance values of the resistors R5 and R6. In the present embodiment, the output terminal of the second operational amplifier OP2 is coupled to the inverting input terminal of the second operational amplifier OP2 through a resistor R7 and a capacitor C2 connected in series. The non-inverting input terminal of the second operational amplifier OP2 is used for receiving a first reference voltage VREF 1. In the embodiment, the second operational amplifier OP2 subtracts the voltage value of the first reference voltage VREF1 and the voltage value of the gain current sensing signal VS to obtain the current control signal SID, and provides the current control signal SID through the output terminal of the second operational amplifier OP 2.

In the present embodiment, the second sensor 224 further includes a voltage divider circuit formed by resistors R8 and R9. The resistor R8 is coupled between the output terminal of the second operational amplifier OP2 and the control terminal of the switch SW. The resistor R9 is coupled between the control terminal of the switch SW and a system low voltage (e.g., ground). The voltage divider circuit divides the voltage of the current control signal SID according to the proportional relationship between the resistance values of the resistors R8 and R9.

Based on the setting of the resistance values of the resistors R5 to R9 and the voltage value of the first reference voltage VREF1, the voltage range of the current control signal SID suitable for linearly controlling the driving current ID can be adjusted.

Referring to fig. 1 and fig. 5, fig. 5 is a schematic diagram of a voltage tracking circuit 130 according to a first embodiment of the invention. In the present embodiment, the voltage tracking circuit 130 includes a third operational amplifier OP 4. The non-inverting input terminal of the third operational amplifier OP4 is used for receiving a second reference voltage VREF 2. The inverting input terminal of the third operational amplifier OP4 is used for receiving the control signal SC from the current controller 120. The third operational amplifier OP4 subtracts the second reference voltage VREF2 and the control signal SC to generate an adjustment signal Sadj, and provides the adjustment signal Sadj to the power circuit 110 via an output terminal of the third operational amplifier OP 4. Since the second reference voltage VREF2 is a fixed voltage value. Therefore, the voltage value of the adjustment signal Sadj and the voltage value of the control signal SC exhibit negative correlation. That is, the voltage value of the adjustment signal Sadj is inversely related to the energy consumed by the switch SW.

For example, when the power circuit 110 provides the output voltage Vo, the current value of the driving current ID of the light source module LM is equal to the preset driving current value. During the driving period, when the current value of the driving current ID starts to increase and the current value of the driving current ID is greater than the preset driving current value, the second sensor 124 of the current controller 120 controls the switch SW according to the increased current value of the driving current ID to maintain the current value of the driving current ID flowing through the light source module LM at the preset driving current value. However, also under the driving of the output voltage Vo, the energy consumed by the switch SW increases (i.e. the voltage difference between the first terminal and the second terminal of the switch SW increases), so the voltage value of the control signal SC output from the first sensor 122 increases. The voltage tracking circuit 130 decreases the voltage value of the adjustment signal Sadj based on the control signal SC whose voltage value increases, and the adjustment signal Sadj whose voltage value decreases the voltage value of the output voltage Vo of the power circuit 110, and vice versa.

Referring to fig. 6, fig. 6 is a schematic diagram of a voltage tracking circuit 230 according to a fourth embodiment of the invention. Unlike the first embodiment, the voltage tracking circuit 230 in the fourth embodiment includes resistors R10 and R11 and capacitors C3 and C4 in addition to the third operational amplifier OP 4. The resistor R10 is coupled to the inverting input terminal of the third operational amplifier OP 4. The resistor R11 and the capacitors C3 and C4 are disposed between the inverting input terminal and the output terminal of the third operational amplifier OP 4. The third operational amplifier OP4 can adjust the operation result of the third operational amplifier OP4 and stabilize the adjustment signal Sadj by setting the resistance values of the resistors R10 and R11 and the capacitances of the capacitors C3 and C4.

Referring to fig. 7, fig. 7 is a schematic view of a projection system 70 according to a fifth embodiment of the invention. In the present embodiment, the projection system 70 includes a light source module LM having series light emitting elements LD _ 1-LD _ n and a driving device 700 for driving the light source module LM. Unlike the projection system 10 of fig. 1, the driving apparatus 700 further includes a power conversion circuit 740 in addition to the power supply circuit 710, the current controller 720 and the voltage tracking circuit 730. The power conversion circuit 740 is configured to receive an external ac power VAC and convert the ac power VAC into a dc power VDC. Therefore, the power supply circuit 710 can receive the dc power VDC and convert the dc power VDC into the output voltage Vo. It should be noted that the power conversion circuit 740 can be any type of rectification circuit of the existing power converter, and therefore, the power circuit 710 and the power conversion circuit 740 can be implemented by only one test of the existing power converter. In this way, the fifth embodiment can further reduce the number of switches of the external circuit connected to the power circuit, and save more components and design cost. Implementation details of the driving device 700 can be sufficiently taught in the embodiments of fig. 1 to 6, and therefore cannot be reiterated here.

Referring to fig. 1 and fig. 8, fig. 8 is a flowchart illustrating a driving method according to an embodiment of the invention. The driving method of the present embodiment can be applied to the projection system 10 of fig. 1 and the projection system 70 of fig. 7. The driving method comprises the following steps: in step S810, a switch SW is provided and coupled to the light source module LM. In step S820, the switch SW is controlled to maintain the current value of the driving current ID flowing through the light source module LM at the preset driving current value, and the control signal SC is provided according to the energy consumed by the switch SW. In step S830, the adjustment signal Sadj is provided according to the control signal SC. In step S840, the output voltage Vo is adjusted according to the adjustment signal Sadj, and the light source module LM is driven by the output voltage Vo. Details regarding the implementation of the above steps have been elaborated in the embodiments of fig. 1 to 6, and therefore cannot be reiterated here.

In summary, in the projection system of the present invention, the driving device drives the light source module having the plurality of light emitting elements connected in series by the output voltage. The driving device maintains the current value of the driving current flowing through the light source module at a preset driving current value by controlling the switch. The control signal is provided according to the energy consumed by the switch, the output voltage is adjusted according to the adjusting signal, wherein the voltage value of the current control signal is in negative correlation with the voltage value of the current sensing signal, and the voltage value of the adjusting signal is in negative correlation with the voltage value of the output voltage.

On the other hand, the driving device of the present invention has only one switch, so the driving device of the present invention does not generate large electromagnetic interference, and thus, the electromagnetic interference generated by the fast switching operation of the plurality of internal switches can be reduced, and the cost required for coping with the electromagnetic interference can be saved. Furthermore, the driving device of the invention only needs a single power supply circuit to provide the output voltage. Therefore, the layout area of the driving device required by the projection device of the embodiment can be greatly reduced, so that the volume of the projection device can be smaller, and the cost of the driving device can be reduced. In addition, the light source module is protected in the case where the current value of the driving current is controlled by the driving device. In addition, the driving device linearly controls the single switch to replace the fast switching operation of the plurality of internal switches in the prior art. Therefore, the projection system can have lower deployment cost of the driving device.

It should be understood that the above-mentioned embodiments are only preferred embodiments of the present invention, and that the scope of the present invention should not be limited thereby, and all the simple equivalent changes and modifications made by the claims and the summary of the invention should be included in the scope of the present invention. It is not necessary for any embodiment or claim of the invention to address all of the objects, advantages, or features disclosed herein. In addition, the abstract and the title of the invention are provided for assisting the search of patent documents and are not intended to limit the scope of the invention. Furthermore, the terms "first," "second," and the like in the description and in the claims are used for naming elements (elements) or distinguishing between different embodiments or ranges, and are not intended to limit the upper or lower limit on the number of elements.

Description of reference numerals:

10. 70: projection device

100. 700: drive device

110. 710: power supply circuit

120. 720: current controller

122. 222: first sensor

124. 224: second sensor

130. 230, 730: voltage following circuit

2242: gain circuit

740: power supply conversion circuit

LM: light source module

LD _1 to LD _ n: light emitting element

Sadj: adjusting signals

Vo: output voltage

SW: switch with a switch body

ID: drive current

SC: control signal

SID: current control signal

VAC: AC power supply

VDC: direct current power supply

VS: current sensing signal

And RS: sensing resistor

OP 1: a first operational amplifier

OP 2: a second operational amplifier

OP 3: operational amplifier

OP 4: third operational amplifier

VREF 1: a first reference voltage

VREF 2: second reference voltage

R1-R11: resistance (RC)

C1-C4: capacitor with a capacitor element

S810 to S840: and (5) carrying out the following steps.

Claims

1. A driving apparatus for driving a light source module having a plurality of light emitting elements connected in series, the driving apparatus comprising: a power supply circuit, a current controller and a voltage following circuit; wherein the content of the first and second substances,

the power circuit is coupled with the light source module and used for adjusting output voltage according to an adjusting signal and driving the light source module by the output voltage;

the current controller is coupled to the light source module and comprises a switch, the current controller is used for controlling the switch to maintain the current value of the driving current flowing through the light source module at a preset driving current value and providing a control signal according to the energy consumed by the switch; and

the voltage tracking circuit is coupled between the power circuit and the current controller for providing the adjustment signal according to the control signal,

wherein the switch has a first end and a second end, the first end of the switch is coupled to the light source module, an

The current controller further includes a first sensor coupled to the first end of the switch and the second end of the switch for sensing a voltage difference between the first end of the switch and the second end of the switch to determine the control signal.

2. The drive of claim 1, wherein the first sensor comprises:

a first operational amplifier having a non-inverting input to receive the voltage value from the first terminal of the switch, an inverting input to receive the voltage value from the second terminal of the switch, and an output to provide the control signal.

3. The drive of claim 1, wherein the switch has a control terminal, the current controller further comprising:

a second sensor coupled to the second terminal of the switch and the control terminal of the switch for receiving the driving current from the second terminal of the switch, obtaining a current sensing signal according to the driving current, and providing a current control signal to the control terminal of the switch according to the current sensing signal,

wherein a voltage value of the current control signal and a voltage value of the current sense signal exhibit a negative correlation.

4. The driving apparatus as claimed in claim 3, wherein said second sensor comprises:

a sensing resistor, a first end of which is coupled to the second end of the switch, and a second end of which is coupled to a system low voltage, for generating the current sensing signal according to a current value of the driving current and a resistance value of the sensing resistor; and

a second operational amplifier having a non-inverting input for receiving a first reference voltage, an inverting input coupled to the first end of the sense resistor for receiving the current sense signal from the sense resistor, and an output for providing the control signal.

5. The drive of claim 4, wherein the second sensor further comprises:

the gain circuit is coupled between the second operational amplifier and the sensing resistor, and is used for performing gain on the current sensing signal from the sensing resistor and providing the current sensing signal after the gain to an inverting input end of the second operational amplifier.

6. The driving apparatus according to claim 1, wherein the voltage follower circuit comprises:

a third operational amplifier having a non-inverting input to receive a second reference voltage, an inverting input to receive the control signal from the current controller, and an output to provide the adjustment signal to the power circuit.

7. A projection system, characterized in that the projection system comprises:

a light source module having a plurality of light emitting elements, wherein the plurality of light emitting elements are connected in series with each other; and

a driving device for driving the light source module having the plurality of light emitting elements connected in series, wherein the driving device includes: a power supply circuit, a current controller and a voltage following circuit; wherein the content of the first and second substances,

8. A driving method for driving a light source module having a plurality of light emitting elements connected in series, the driving method comprising:

providing a switch having a first end and a second end, coupling the first end of the switch to the light source module;

controlling the switch to maintain the current value of the driving current flowing through the light source module at a preset driving current value, and providing a control signal according to the energy consumed by the switch;

sensing a voltage difference between the first terminal of the switch and the second terminal of the switch to determine the control signal;

providing an adjusting signal according to the control signal; and

and adjusting the output voltage according to the adjusting signal, and driving the light source module by the output voltage.

9. The driving method according to claim 8, wherein the switch further has a control terminal, and wherein the step of controlling the switch to maintain the current value of the driving current flowing through the light source module at the preset driving current value comprises:

receiving the driving current from the second terminal of the switch;

obtaining a current sensing signal according to the driving current; and

providing a current control signal to the control terminal of the switch in dependence on the current sense signal,

10. The driving method according to claim 9, wherein the step of controlling the switch to maintain the current value of the driving current flowing through the light source module at the preset driving current value further comprises:

the current sense signal is gained.