CN101426312A - Backlight device - Google Patents

Abstract

The invention relates to a backlight device, comprising a light emitting unit, a voltage converter, a voltage detection unit, a correction unit and a feedback control unit. The light-emitting unit is provided with a first connecting end and a second connecting end. The voltage converter converts the input voltage to a rated voltage according to a periodic signal. The voltage detection unit detects voltage levels on the first connecting end and the second connecting end of the light-emitting unit to generate a measurement voltage. The calibration unit performs gain calibration on the measurement voltage and adjusts the calibrated measurement voltage by using a scaling ratio to generate a calibration voltage. The feedback control unit outputs a feedback signal according to the correction voltage, and the voltage converter dynamically modifies the periodic signal according to the feedback signal.

Description

backlight

technical field

The invention relates to a backlight device of a display, and in particular to a backlight device which dynamically modifies the voltage for driving a light-emitting diode.

Background technique

For various types of display devices, liquid crystal displays can be regarded as current mainstream products. Because liquid crystal displays have the advantages of high image quality, low power consumption, thin mass production, low voltage drive, and small size, they occupy a place in the market, such as small portable TVs, video phones, video recorders, notebooks, etc. Computers, desktop monitors, and LCD TVs all demonstrate the importance of LCDs.

A liquid crystal display mainly includes a liquid crystal display panel, a backlight module and a frame. Among them, the light source generated by the backlight module is a very important factor in determining the chromaticity and brightness of the liquid crystal display. FIG. 1 is a structural diagram of a conventional backlight device 100 . Please refer to FIG. 1 , the backlight device 100 includes a voltage converter 110 and light emitting units 120a˜120n. The light-emitting units 120a-120n are all electrically connected to the voltage converter 110, and the light-emitting unit 120a includes M light-emitting diodes _D11 -D _M1 , a switch SW1, and a constant current source CS1, where M is an integer greater than 0. The internal components of the light emitting units 120b - 120n can be deduced by analogy.

In order to easily explain the problems of the conventional backlight device 100 , the partial structure diagram of the conventional backlight device 100 shown in FIG. 2 will now be used for illustration. Please refer to FIG. 2 , after the voltage converter 110 receives an input voltage V _I1 from its input terminal, it converts the input voltage V _I1 to a rated voltage V _O1 according to its internal periodic signal, and transmits it to the light emitting unit 120a. When the switch SW1 in the light-emitting unit 120a is turned on, the light-emitting unit 120a will drive the internal light-emitting diodes D ₁₁ -D _M1 to emit light by the rated voltage V _O1 , and adjust the light-emitting diodes D by its internal constant current source CS1 ₁₁ ~D _M1 brightness.

Since the voltage converter 110 determines the magnitude of the rated voltage V _O1 according to its internal periodic signal, when the periodic signal is constant, the rated voltage V _O1 will also be fixed accordingly. However, the forward voltage of the LEDs D ₁₁ -D _M1 will decrease as the temperature of the system rises, that is, the voltage difference between the two ends of the LEDs D ₁₁ -D _M1 will become smaller. Therefore, the excess voltage will be absorbed by the switch SW1, and the energy will be released in the form of heat by switching the switch SW1, resulting in temperature rise and energy waste.

For example, referring to FIG. 2 , the LED D ₁₁ has a forward voltage V ₁₁ , the LED D ₂₁ has a forward voltage V ₁₂ , and so on. In addition, the voltage dropped on the switch SW1 is the voltage V _SW1 , and the voltage dropped on the constant current source CS1 is the voltage V _C1 , so the first mathematical formula V _O1 =V ₁₁ +...+V can be obtained _1M +V _S and the second mathematical formula V _S =V _SW1 +V _C1 . From the first mathematical formula, when the forward voltage V ₁₁ ～V _1M of the light-emitting diodes D ₁₁ ～D _M1 decreases due to temperature rise, the voltage V _S will rise accordingly because the rated voltage V _O1 is fixed. . From the second mathematical formula, since the voltage V _C1 is fixed, the rising part of the voltage V _S is completely absorbed by the switch SW1. As a result, a lot of energy will be dissipated in the form of heat (the energy loss of the switch is divided into conduction loss and switching loss), which will cause the system temperature to rise and excess power consumption, and the working efficiency of the system will also be reduced.

Contents of the invention

The invention provides a backlight device, which can improve the problem that the forward voltage of the light-emitting diode itself decreases due to the temperature rise, so that the redundant voltage is absorbed by the switch, which causes the temperature rise of the switch.

The invention provides a backlight device, which can not only improve the influence of LED temperature rise, but also effectively prevent redundant power consumption and device temperature rise, so that the overall efficiency can be improved.

The invention provides a backlight device, which includes a light emitting unit, a voltage converter, a voltage detection unit, a correction unit and a feedback control unit. Wherein, the light emitting unit has a first connection end and a second connection end. The voltage converter converts the input voltage to a rated voltage according to a period signal, and the rated voltage drives the light emitting unit through the first connection end of the light emitting unit.

Following the above, the voltage detection unit is used to detect the voltage levels on the first connection terminal and the second connection terminal of the light emitting unit, thereby generating a measurement voltage. The correction unit is used for performing gain correction on the measured voltage, and adjusting the corrected measured voltage with a scaling ratio, so as to generate a corrected voltage. The feedback control unit outputs a feedback signal according to the correction voltage, and the voltage converter dynamically corrects the periodic signal according to the feedback signal.

From another point of view, the present invention provides a backlight device including N light emitting units, a voltage converter, N voltage detection units, a voltage comparison unit, a correction unit and a feedback control unit. Wherein, each of the N light-emitting units has a first connection end and a second connection end, and N is an integer greater than 0. The voltage converter converts the input voltage to a rated voltage according to a periodic signal, and the rated voltage drives each light emitting unit through the first connection end of each light emitting unit.

Following the above, each of the N voltage detection units generates a measurement voltage, and the i-th voltage detection unit among the N voltage detection units is used to detect the voltage on the two connection terminals of the i-th light-emitting unit The voltage level is used to generate the i-th measurement voltage, and the aforementioned i is an integer and 1≦i≦N. The voltage comparison unit is used to compare the measurement voltages generated by the N voltage detection units, and select one of the measurement voltages as the maximum measurement voltage according to the comparison result to output.

On the other hand, the correction unit is used for performing gain correction on the measured voltage, and adjusting the corrected measured voltage with a scaling ratio, so as to generate a corrected voltage. The feedback control unit outputs a feedback signal according to the correction voltage, and the voltage converter dynamically corrects the periodic signal according to the feedback signal.

The present invention adopts the design of the feedback circuit, so that the voltage converter can dynamically modify its internal periodic signal according to a feedback signal to change the rated output voltage, so it can effectively improve the shortcomings of the prior art and prevent the temperature of the switch from rising. Moreover, by dynamically adjusting the rated voltage, unnecessary power consumption and device temperature rise can be prevented, so that the overall efficiency can be improved.

Description of drawings

In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and understandable, the specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

FIG. 1 is a structural diagram of a conventional backlight device 100 .

FIG. 2 is a partial structural diagram of a conventional backlight device 100 .

FIG. 3A is a structural diagram of a backlight device 300 according to an embodiment of the present invention.

FIG. 3B is a structural diagram of another type of voltage detection unit used in the backlight device 300 .

FIG. 4A is a structural diagram of a backlight device 400 according to another embodiment of the present invention.

FIG. 4B is a structural diagram of another type of voltage detection unit used in the backlight device 400 .

Description of main component symbols:

100, 300, 400: backlight device

110, 320, 460: voltage converter

120a～120n, 310, 410a～410n: light emitting unit

330, 380, 420a~420n, 480a~480n: voltage detection unit

340, 440: correction unit

350, 450: feedback control unit

311, 411a: current generating unit

430: Voltage comparison unit

D ₁ ~D _M , D ₁₁ ~D _M1 : Light emitting elements

C ₁ , C ₂ , C ₁₁ , C ₁₂ : capacitance

T ₁ , T ₄₁ : Transformer

E ₁ ~E _N : Diodes

SW1, SW31, SW41: switch

CS1, CS31, CS41: constant current source

S ₁ , S ₁₁ ~SN ₁ : the first connection end

S ₂ , S ₁₂ ~S _N2 : the second connection terminal

V ₁₁ , V _I3 , V _I4 : Input voltage

V _O1 , V _O3 , V _O4 : rated voltage

V ₁₁ ~V _1M , V ₃₁ ~V _3M : forward voltage

V _SW1 , V _C1 , V _SW3 , V _C3 , V _S : Voltage

VM31, V41a～V41n: measuring voltage

VM32, V42: correction voltage

S31, S41: feedback signal

VM41: maximum measurement voltage

Detailed ways

FIG. 3A is a structural diagram of a backlight device 300 according to an embodiment of the present invention. Referring to FIG. 3 , the backlight device 300 includes a light emitting unit 310 , a voltage converter 320 , a voltage detection unit 330 , a calibration unit 340 and a feedback control unit 350 . Wherein, the light emitting unit 310 has a first connection terminal S ₁ and a second connection terminal S ₂ , the first connection terminal S ₁ is electrically connected to the output terminal of the voltage converter 320 , and the second connection terminal S ₂ is electrically connected to the voltage detection unit 330 .

Following the above, the voltage detection unit 330 is electrically connected between the first connection terminal S ₁ and the second connection terminal S ₂ for detecting the voltage levels of the two connection terminals and generating a measurement voltage VM31 accordingly. The correction unit 340 is electrically connected to the voltage detection unit 330 and the feedback control unit 350, and is used for performing gain correction on the measurement voltage VM31, and adjusting the corrected measurement voltage VM31 with a scaling ratio, thereby generating a correction voltage VM32 . The feedback control unit 350 is electrically connected to the voltage converter 320 for outputting a feedback signal S31 to the voltage converter 320 according to the correction voltage VM32 .

The light emitting unit 310 includes a plurality of light emitting elements D ₁ -D _M and a current generating unit 311 , where M is an integer greater than 0. Wherein, the light-emitting elements D ₁ -D _M are connected in series between the first connection end S ₁ and the second connection end S ₂ of the light-emitting unit 310 , and each of the light-emitting elements D ₁ -D _M is a light-emitting diode. Here, the first end (anode end) of the light emitting element D ₁ is electrically connected to the first connection end S ₁ , and the second end (cathode end) of the light emitting element D _M is electrically connected to the second connection end S ₂ .

Furthermore, the current generating unit 311 is electrically connected between the second connection terminal _S2 of the light emitting unit 310 and the ground terminal, and includes a switch SW31 and a constant current source CS31. One end of the switch SW31 is electrically connected to the second connection end S ₂ , the other end is electrically connected to the constant current source CS31 , and the other end of the constant current source CS31 is electrically connected to the ground end. Here, the current generating unit 311 regulates the current flowing through the light emitting elements D ₁ -D _M according to a control signal. In other words, the switch SW31 will determine its conduction state according to the above-mentioned control signal, so as to control whether the current provided by the constant current source CS31 flows through the light-emitting elements D ₁ -D _M .

The voltage detection unit 330 includes capacitors C ₁ and C ₂ . Wherein, the first end of the capacitor _C1 is electrically connected to the first connection end _S1 , the second end thereof is used to output a measurement voltage VM31, and the first end of the capacitor _C2 is electrically connected to the second end of the capacitor _C1. terminal, and its second terminal is electrically connected to the second connection terminal S ₂ .

Please continue to refer to FIG. 3A. After receiving an input voltage V _I3 , the voltage converter 320 will amplify or reduce the input voltage V _I3 according to its internal periodic signal, and its purpose is to convert the input voltage V _I to a rated voltage V _O3 . When the switch SW31 is turned on according to the control signal, the light-emitting unit 301 will drive its internal light-emitting elements D ₁ -D _M with the rated voltage V _O3 provided by the voltage converter 320 , and can adjust the constant current source CS31 to The brightness of the light-emitting elements D ₁ -D _M is adjusted.

Assume that the light-emitting element D ₁ has a forward voltage V ₃₁ , the light-emitting element D _M has a forward voltage V _3M , and so on, and assume that the voltage on the switch SW31 is the voltage V _SW3 and the voltage on the constant current source CS31 is the voltage V _C3 . Since the forward voltage of the light-emitting elements D ₁ -D _M will drop due to temperature rise, when the forward voltage V _f1 -V _fM drops, the voltage detection unit 330 will obtain the first connection terminal S ₁ and the second connection terminal The variation of the voltage between S _{and 2} generates a measurement voltage VM31 and sends it to the calibration unit 340 .

After receiving the measurement voltage VM31 , the correction unit 340 performs gain correction on the measurement voltage VM31 , and adjusts the corrected measurement voltage VM31 with a scaling ratio, thereby generating a correction voltage VM32 . That is to say, after obtaining the voltage level between the first connection terminal _S1 and the second connection terminal _S2 , the calibration unit 340 will subtract the voltage level obtained at the moment from the voltage level obtained at the previous moment. , to get a voltage change. Afterwards, the correction unit 340 performs a non-linear calculation on the variation, and then generates a correction voltage VM32 , and outputs it to the feedback control unit 350 .

After the feedback control unit 350 receives the correction voltage VM32 , it generates a feedback signal S31 according to the correction voltage VM32 and sends it to the voltage converter 320 . That is to say, the feedback control unit 350 converts the unit of the received correction voltage VM32 to generate the feedback signal S31 . After receiving the feedback signal S31 , the voltage converter 320 will modify the internal periodic signal according to the feedback signal S31 to change the output rated voltage V _O3 . For example, the voltage converter 320 originally scales the input voltage V _I3 with a proportional value to generate the rated voltage V _O3 according to the internal periodic signal, but after receiving the feedback signal S31 , it will use the feedback signal S31 to compare with the periodic signal. Add or subtract, so as to generate a new periodic signal to modify the proportional value used to scale the input voltage V _I3 .

Here, the coupling manner of the voltage converter 320 , the voltage detection unit 330 , the calibration unit 340 and the feedback control unit 350 can be regarded as a feedback circuit. By means of the aforementioned feedback circuit, the backlight device 300 can adjust the magnitude of the rated voltage V _O3 at any time. Therefore, as long as the voltage detection unit 330 obtains the amount of change in the forward voltage of the light-emitting elements D ₁ -D _M , it can immediately generate a feedback signal S31 to correct the periodic signal in the voltage converter 320, and then change the rated voltage V _O3 so that The voltage V _SW3 dropped across switch SW31 does not rise. In addition, the drop in forward voltage of light-emitting elements D ₁ -D _M due to temperature rise is not a linear relationship, so the correction unit 340 uses a non-linear calculation method to correct the gain of the measured voltage VM31, so as to conform to the actual system demand.

It is worth mentioning here that the structure of the voltage detection unit 330 in the backlight device 300 is not limited to the above description. For example, FIG. 3B is a structural diagram of another type of voltage detection unit used in the backlight device 300 , wherein the voltage detection unit 380 is used to replace the voltage detection unit 330 in FIG. 3A . Please refer to FIG. 3B , the voltage detection unit 380 includes a transformer T ₁ . Wherein, the transformer T ₁ has a primary side and a secondary side, the first terminal of the primary side is electrically connected to the first connection terminal S ₁ of the light emitting unit 310 , and the second terminal of the primary side is electrically connected to the second terminal of the light emitting unit 310 . The terminal S ₂ is connected, and the first terminal of the secondary side is used to generate the measurement voltage VM31 , and the second terminal of the secondary side is electrically connected to the ground terminal.

Following the above, using the coupling method of the above-mentioned transformer T ₁ , the voltage detection unit 380 can achieve the function of the voltage detection unit 330 composed of capacitors. Therefore, those skilled in the art should know that the voltage detection unit in the backlight device 300 is not limited to the forms listed in the above embodiments, and users can also use an amplifier to design a circuit to achieve the function of the voltage detection unit.

FIG. 4A is a structural diagram of a backlight device 400 according to another embodiment of the present invention. Please refer to FIG. 4A, the backlight device 400 includes N light emitting units 410a-410n, a voltage converter 460, N voltage detection units 420a-420n, a voltage comparison unit 430, a correction unit 440 and a feedback control unit 450, where N is greater than 0 an integer of . Wherein, each of the light emitting units 410a˜410n has a first connection terminal and a second connection terminal, for example, the light emitting unit 410a has a first connection terminal S ₁₁ and a second connection terminal S ₁₂ , and the light emitting unit 410b has a first connection terminal S _N1 and the second connection terminal _SN2 , and so on for the rest. The first connection terminals S _{11 -SN1} of all the light emitting units are electrically connected to the output terminal of the voltage converter 460, and the second connection terminals S _{12 -SN2} are respectively electrically connected to the corresponding voltage detection units 420a-420n .

Following the above, each of the voltage detection units 420a-420n is electrically connected between the corresponding first connection terminals S11 _{- SN1} and the second connection terminals _S12 - _SN2 , for example, the voltage detection unit 420a is electrically connected to the first connection Between the terminal _S11 and the second connection terminal _S12 , the voltage detection unit 420n is electrically connected between the first connection terminal _SN1 and the second connection terminal _SN2 . In addition, the voltage detection units 420 a - 420 n are used to detect the voltage levels of the two connection terminals, and generate a measurement voltage respectively. For example, the voltage detection unit 420a is electrically connected between the first connection terminal _S11 and the second connection terminal _S12 , and is used for detecting the voltage levels of the two connection terminals, and accordingly generating a measurement voltage V41a. The voltage comparison unit 430 is electrically connected to the voltage detection units 420 a - 420 n for comparing the voltage values of the measurement voltages V41 a - V41 n , and selects one of them according to the comparison result to output as a maximum measurement voltage VM41 .

The correction unit 440 is electrically connected to the voltage comparison unit 430 and the feedback control unit 450 , and the feedback control unit 450 is electrically connected to the voltage converter 460 .

Please continue to refer to FIG. 4A , the structure and functions of the backlight device 400 of this embodiment are very similar to those of the above embodiments, the only difference lies in the number of voltage comparison units, light emitting units, and voltage detection units. Therefore, the spirit of the present embodiment will now be described with respect to these units (410a-410n, 420a-420n, 430).

In the light-emitting units 410a-410n, each unit includes M light-emitting elements and a current generating unit, and M is an integer greater than 0. For example, the light-emitting unit 420a includes light-emitting elements _D11 -D _M1 and a current generating unit 411a. By analogy, internal components of the light emitting units 410b-410n. Here, the current generating unit 411a includes a switch SW41 and a constant current source CS41, which regulates the current flowing through the light emitting elements D ₁₁ -D _M1 according to a control signal. In other words, the switch SW41 will determine its conduction state according to the above-mentioned control signal, so as to control whether the current provided by the constant current source CS41 flows through the light-emitting elements D ₁₁ -D _M1 .

Among the voltage detection units 420a˜420n, each unit includes two capacitors, and the two capacitors are connected in series and electrically connected between the corresponding first connection terminal and the second connection terminal. For example, the voltage detection unit 420a includes capacitors C ₁₁ and C ₁₂ , wherein the first end of the capacitor C ₁₁ is electrically connected to the first connection end S ₁₁ , the second end is electrically connected to the first end of the capacitor C ₁₂ , and the capacitor C The second end of ₁₂ is electrically connected to the second connection end S ₁₂ , and the first end is used to generate a measurement voltage V41a. By analogy, the internal components of the voltage detection units 420b˜420n are coupled with them.

The voltage comparison unit 430 includes N diodes E _{1 -EN} , wherein the anode of each diode is electrically connected to the corresponding voltage detection unit (for example, the anode of the diode E ₁ is electrically connected to the voltage detection unit 420a), and the diode The cathode terminals of E _{1 -EN} are electrically connected to the calibration unit 440 .

In FIG. 4A, the forward voltage of the light-emitting units 420a-420n may drop due to temperature rise, so each voltage detection unit will obtain a corresponding measurement voltage, so the N voltage detection units 420a-420n will have N measuring voltages V41a-V41n. Therefore, the voltage comparison unit 430 will receive the measured voltages V41a-V41n and compare the voltage values of the measured voltages V41a-V41n, and then select one of the measured voltages V41a-V41n according to the comparison result to output as a maximum measured voltage VM41 . For example, if the voltage comparing unit 430 only includes diodes E ₁ and E ₂ , and the diode E ₁ receives the measured voltage V41a of 2 volts, and the diode E ₂ receives the measured voltage V41b of 1 volt, then the diode E The cathode terminal of ₁ will get a voltage of 2 volts, so that the 1 volt voltage received by the diode E ₂ cannot pass through, so the maximum measured voltage generated by using this principle is 2 volts.

After the maximum measured voltage VM41 is obtained, the following actions will be similar to the above-mentioned embodiment. The correction unit 440 performs gain correction and scaling on the maximum measured voltage VM41 to generate a correction voltage V42 and transmits it to the feedback control unit 450, and the feedback control unit 450 generates a feedback signal S41 according to the correction voltage V42, To modify the periodic signal of the voltage converter 460, thereby changing the rated voltage V _O4 .

It is worth mentioning here that the structure of the voltage detection units 420 a - 420 n in the backlight device 400 is not limited to the above description. For example, FIG. 4B is a structural diagram of another type of voltage detection unit used in the backlight device 400 , wherein the voltage detection units 480 a - 480 n are used to replace the voltage detection units 420 a - 420 n in FIG. 4A . Please refer to FIG. 4B , among the voltage detection units 480 a - 480 n , each voltage detection unit includes a transformer. Wherein, the transformer T ₄₁ has a primary side and a secondary side, the first terminal and the second terminal of the primary side are respectively electrically connected to the first connection terminal S ₁₁ and the second connection terminal S ₁₂ of the light emitting unit 410a, and the secondary side The first terminal of the secondary side is used to generate the measurement voltage V41a, and the second terminal of the secondary side is electrically connected to the ground terminal. By analogy, the internal components of the voltage detection units 480b˜480n are coupled with them.

Following the above, using the coupling method of the above-mentioned transformer T ₄₁ , the voltage detection units 480 a - 480 n can achieve the functions of the voltage detection units 420 a - 420 n composed of capacitors. Therefore, those skilled in the art should know that the voltage detection unit in the backlight device 400 is not limited to the forms listed in the above-mentioned embodiments.

To sum up, the present invention adopts the design of the feedback circuit, so that the voltage converter can correct its internal periodic signal according to a feedback signal, thereby changing the rated voltage of its output, so that the temperature of the switch will not rise, thus preventing redundant Power consumption and device temperature increase, and can make the state of the light-emitting element more stable, so that the overall efficiency of the system is improved. In addition, the present invention can be applied to any voltage converter architecture, so it can be widely used to improve the competitiveness of products.

Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make some modifications and improvements without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection should be defined by the claims.

Claims (13)

1. A backlight device, characterized in that comprising: A light emitting unit having a first connection end and a second connection end; A voltage converter, used to convert an input voltage to a rated voltage according to a periodic signal, and the rated voltage drives the light emitting unit to emit light through the first connection terminal of the light emitting unit; a voltage detection unit, used to detect the voltage levels on the first connection terminal and the second connection terminal of the light emitting unit, and generate a measuring voltage accordingly; a correction unit, used for performing gain correction on the measured voltage, and adjusting the corrected measured voltage with a scaling ratio, so as to generate a corrected voltage; and A feedback control unit is used for outputting a feedback signal according to the correction voltage, wherein the voltage converter dynamically corrects the periodic signal according to the feedback signal. 2. The backlight device according to claim 1, wherein the voltage detection unit comprises: a first capacitor, the first end of which is electrically connected to the first connection end of the light emitting unit, and the second end of which is used to generate the measurement voltage; and A second capacitor, the first end of which is electrically connected to the second end of the first capacitor, and the second end of which is electrically connected to the second connection end of the light emitting unit. 3. The backlight device according to claim 1, wherein the voltage detection unit comprises: A transformer has a primary side and a secondary side, the first end of the primary side is electrically connected to the first connection end of the light emitting unit, and the second end of the primary side is electrically connected to the first connection end of the light emitting unit Two connection terminals, and the first terminal of the secondary side is used to generate the measurement voltage, and the second terminal of the secondary side is electrically connected to a ground terminal. 4. The backlight device according to claim 1, wherein the light emitting unit comprises: a plurality of light-emitting elements, the light-emitting elements are connected in series between the first connection end and the second connection end of the light-emitting unit; and A current generating unit is electrically connected between the second connection terminal of the light-emitting unit and a ground terminal, and is used for regulating the current flowing through the light-emitting elements according to a control signal. 5. The backlight device according to claim 4, wherein the current generating unit comprises: a switch, the first end of which is electrically connected to the second connection end of the light emitting unit, and the switch determines its conduction state according to the control signal; and A constant current source is electrically connected between the second end of the switch and the ground end. 6. The backlight device as claimed in claim 4, wherein the light emitting elements are light emitting diodes. 7. A backlight device, characterized in that it comprises: N light-emitting units, each of which has a first connection end and a second connection end, and N is an integer greater than 0; A voltage converter, used for converting an input voltage to a rated voltage according to a periodic signal, and the rated voltage drives the light emitting units to emit light through the first connection terminal of each of the light emitting units; N voltage detection units are used to generate N measurement voltages, wherein the i-th voltage detection unit is used to detect the voltage level on the two connection terminals of the i-th light-emitting unit, and accordingly generate the i-th measurement voltage , where i is an integer and 1≦i≦N; a voltage comparison unit, used to compare the voltage values of the measured voltages, and select one of the measured voltages to output as a maximum measured voltage according to the comparison result; a correction unit, used for performing gain correction on the maximum measured voltage, and adjusting the corrected maximum measured voltage with a scaling ratio, so as to generate a corrected voltage; and A feedback control unit is used for outputting a feedback signal according to the correction voltage, wherein the voltage converter dynamically corrects the periodic signal according to the feedback signal. 8. The backlight device according to claim 7, wherein the voltage comparison unit comprises: N diodes, wherein the anode of the i-th diode is electrically connected to the i-th voltage detection unit, and the cathode of each of these diodes is electrically connected to the calibration unit. 9. The backlight device according to claim 7, wherein the i-th voltage detection unit comprises: a first capacitor, the first end of which is electrically connected to the first connection end of the i-th light-emitting unit, and the second end of which is used to generate the i-th measurement voltage; and A second capacitor, the first end of which is electrically connected to the second end of the first capacitor, and the second end of which is electrically connected to the second connection end of the i-th light-emitting unit. 10. The backlight device according to claim 7, wherein the i-th voltage detection unit comprises: A transformer has a primary side and a secondary side, the first end of the primary side is electrically connected to the first connection end of the ith light-emitting unit, and the second end of the primary side is electrically connected to the ith The second connection terminal of the light emitting unit, and the first terminal of the secondary side is used to generate the i-th measurement voltage, and the second terminal of the secondary side is electrically connected to a ground terminal. 11. The backlight device according to claim 7, wherein the i-th light-emitting unit comprises: A plurality of light-emitting elements, these light-emitting elements are connected in series between the first connection end and the second connection end of the i-th light-emitting unit; and A current generation unit is electrically connected between the second connection terminal of the i-th light-emitting unit and a ground terminal, and is used for regulating the current flowing through the light-emitting elements according to a control signal. 12. The backlight device according to claim 11, wherein the current generating unit comprises: a switch, the first end of which is electrically connected to the second connection end of the i-th light-emitting unit, and the switch determines its conduction state according to the control signal; and A constant current source is electrically connected between the second end of the switch and the ground end. 13. The backlight device as claimed in claim 11, wherein the light emitting elements are light emitting diodes.

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