TWI384439B - Multi-color backlight control circuit and method - Google Patents

Description

Multicolor backlight control circuit and method

The present invention relates to a multicolor backlight control circuit (Backlight Control Circuit) and related control methods.

In the liquid crystal display device, a backlight control circuit is used to control the light emitting diode (LED) to emit light from behind the liquid crystal screen, so that the user can view the screen on the screen.

LEDs controlled by backlight control circuits currently have two types of design methods, one of which uses white LEDs in all cases, and the other uses LEDs of three colors of RGB (referred to as "multi-color backlight" in the present invention, and its corresponding control circuit This is referred to as "multicolor backlight control circuit" in the present invention. The advantage of the former is that the circuit is relatively simple, but the white light emitted by it is the synthesized light after the blue light is excited by the fluorescent powder, and its color rendering property is poor. The use of RGB three colors of LED mixed light into white light can achieve better color rendering. However, whether it is a white light LED or RGB three colors of LED mixed light into white light as a backlight source, its light will be filtered by the liquid crystal screen color filter when passing through the liquid crystal screen, only with pixels Light of the same color will penetrate, in other words, its energy will be partially lost and not fully utilized. There is a new technology called color sequential, which is designed to solve this problem. Its RGB three-color backlight corresponds to the same color pixel on the LCD screen, which is turned on and does not need color filter film, so it can save light energy. But the disadvantage is that the circuit is more complicated. The new technology of color cycling highlights the importance of multi-color backlight control circuits, especially the multi-color backlight control circuit that can be used with color cycling technology.

In particular, RGB three color LEDs, the operating voltage is not the same. Generally speaking, white LEDs have an operating voltage of about 3.2V-3.8V; red LEDs have an operating voltage of about 1.9V-2.6V; green LEDs have an operating voltage of about 2.9V-3.7V; blue LEDs Its working voltage is about 3.0V-3.8V. When applied to LCD backlights, it is common to have multiple LEDs connected in series in the circuit arrangement, so the total supply voltage required is quite different between the LED strings of different colors, in the red LED It may exceed 15V with the blue LED. Therefore, in order to control the relative brightness and power efficiency of the RGB three-color backlight, three sets of backlight control circuits 10R, 10G, and 10B must be separately provided in the prior art to supply different voltages Vout(R), Vout(G), Vout(B). ), as shown in Figure 1. Even if the three sets of backlight control circuits are integrated into the same integrated circuit, three sets of voltage supply circuits and associated feedback control circuits are still required in the circuit.

Obviously, the above described method is not economical. Therefore, it is necessary to propose a multi-color backlight control circuit that is more compact on the hardware and more efficient in cost.

In view of this, the present invention is directed to the deficiencies of the prior art described above, and proposes a multi-color backlight control circuit having a simplified hardware architecture.

A second object of the present invention is to provide a multicolor backlight control method.

In order to achieve the above object, the present invention provides a multi-color backlight control circuit comprising: a plurality of pins for connecting with a plurality of different color LED paths; and a voltage supply circuit It accepts an input voltage and provides a single output voltage to the plurality of different color LED paths. As used herein, "providing a single output voltage" means providing a single voltage at the same point in time, but at different points in time, the voltage can vary depending on the feedback detection result.

In the above multi-color backlight control circuit, the number of the light-emitting diodes is different on at least two different color LED paths connected thereto.

According to the present invention, the total number of the light-emitting diodes of different colors may be the same, or the light-emitting diodes of different colors may be illuminated at different times, or the current amounts of the light-emitting diodes of different colors may be different.

In another aspect, the present invention provides a backlight control circuit including: a plurality of pins for connecting to a plurality of light emitting diode paths; and a voltage supply circuit that receives an input voltage and provides a single output The voltage is given to the plurality of light-emitting diode paths, and the number of the light-emitting diodes is different in at least two of the light-emitting diode paths.

The backlight control circuit described above may be a monochrome or multi-color backlight control circuit.

In another aspect, the present invention provides a multi-color backlight control method comprising: providing a single output voltage for at least two different color LED paths. As used herein, "providing a single output voltage" means providing a single voltage at the same point in time, but at different points in time, the voltage can vary depending on the feedback detection result.

Similar to the foregoing, according to the present invention, the total number of the light-emitting diodes of different colors may be the same, or the light-emitting diodes of different colors may be illuminated at different times, or the current of the light-emitting diodes of different colors may not be the same. the same.

The purpose, technical content, features, and effects achieved by the present invention will become more apparent from the detailed description of the embodiments.

Referring to FIG. 2, in the present invention, only a single set of output voltages Vout is provided, so only a single multi-color backlight control circuit 100 is required; the multi-color backlight control circuit 100 has a plurality of pins (illustrated as R1 in the figure) -R3, G1-G3, B1-B3, but the number is not limited to three colors) for respectively connecting with LED paths of different colors. The output voltage Vout is arranged to be equal to or slightly larger than the least common multiple of the operating voltage of each LED. Correspondingly, on different color LED paths, different numbers of LEDs are arranged so that the voltages required for each LED path are similar, and can operate efficiently under the same supply voltage Vout. It should be noted that the number of RGB LEDs on the path is respectively plotted as 5, 4, and 3, which are only shown schematically to indicate their numbers; the actual number should be determined according to the product design. For example, the number of red LEDs can be 15 and the number of green and blue LEDs is 10 (assuming the green LED is similar to the operating voltage of the blue LED, the subtle difference can be ignored), and the output voltage Vout is Around 36V. Output voltage Vout higher than the required voltage value will reduce the power efficiency, but as long as the voltage danger limit is not exceeded, it does not affect the normal operation of the LED.

In the arrangement of Fig. 2, since the number of LEDs of different colors is different, it is necessary to balance the brightness. In this regard, in one embodiment of the present invention, the total number of LEDs of different colors may be arranged to be the same or similar, that is, the number of LED paths of different colors is different, but the total number is the same or similar. For example, assuming that the number of LEDs on each red LED path is 15 and the number of green and blue LEDs is 10, two red LED paths and three green LED paths can be arranged in the overall circuit. Three blue LED paths, and the number of LEDs in each color is 30.

In addition to the above method of changing the number of paths, a different number of LEDs of different colors can be maintained, but the lighting time is controlled; for example, if the ratio of the number of RGB LEDs is 3:2:2, the ratio of the lighting time can be controlled to 2 : 3:3, so that the brightness received by the naked eye is the same or similar. Referring to Figure 3, the red, green, and blue LEDs are illuminated at T1, T2, and T3, respectively, with a ratio of 2:3:3. The pulse times T1, T2, T3 can be generated by setting a counter 16 and three sets of pulse generators 17, 18, 19, and the counter 16 sequentially activates the pulse generators 17, 18, 19 according to the clock to generate a corresponding Pulse time T1, T2, T3. The clock may be taken from the outside of the multi-color backlight control circuit 100 (for example, from a liquid crystal screen controller), or a clock generator may be provided inside the multi-color backlight control circuit 100. In some designs, after the RGB tri-color LEDs are turned on, a short, full dark time is arranged to eliminate the afterimage, so a fourth or more pulse generators (not shown) can be added to A full dark period is generated and the counter 16 is in turn to initiate four or more pulse generators in turn according to the clock.

In addition to the above manners, the amount of current of the different color LEDs can also be separately controlled so that different numbers of LEDs of the same color produce the same or similar brightness. Referring to FIG. 4, which is a schematic circuit diagram of another embodiment of the present invention, in order to simplify the drawing, only one LED path of different colors is shown. As shown, in the multi-color backlight control circuit 100 of the present embodiment, current quantities CS1-CS3 (shown in circuit blocks, details of which are detailed later) are used to control the amount of current on each LED path. In addition to this, sample and hold circuits (S/H) 31-33 are provided in the circuit to maintain the voltages on the corresponding nodes, respectively. The sample-and-hold circuits 31-33 are each controlled by the signals S1-S3, taking the sample-and-hold circuit 31 as an example. For details, please refer to FIG. 5. When the signal S1 turns on the switch SW, the voltage on the corresponding node NA1 can be sampled. And when the switch SW is turned off, the voltage is stored in the capacitor C1.

Returning to Fig. 4, the lowest voltage selection circuit 21 selects the lowest one of the outputs 111-113 of the sample and hold circuit 31-33, compares it with the reference voltage Vref in the input error amplifying circuit 13, and generates a control signal based on the comparison result. 15. The control voltage supply circuit 11 generates an appropriate voltage Vout. The purpose of selecting the lowest voltage is to make the output voltage Vout meet the voltage requirements of any one of the LED paths, so that the current source on each LED path can work normally. The voltage supply circuit 11 can be, for example, a boost converter, or can be other types of power circuits such as a buck converter, a buck-boost converter, and a flyback converter. )Wait.

In order to avoid the output voltage Vout being too high, an overvoltage protection circuit may be provided to increase the safety of the multicolor backlight control circuit; the circuit implementation method is the same as the conventional circuit implementation method in the white LED backlight control circuit, and is no longer Narration.

See Figure 6 for details of current sources CS1-CS3. As shown in the figure, in addition to the basic current source structure, each current source CS1-CS3 is still controlled by the enable signal EN1-EN3. When the enable signal EN1-EN3 turns on the corresponding switch, the current source CS1-CS3 To work. The waveforms of the enable signals EN1-EN3 are sequentially rotated as shown in FIG. 7 to control the LEDs of the corresponding colors to be turned on alternately. The relationship between the enable signals EN1-EN3 and the signals S1-S3 in the sample-and-hold circuits 31-33 is as shown in the figure. After the enable signals EN1-EN3 enable the corresponding current sources CS1-CS3, the sample-and-hold circuits 31-33 The signal S1-S3 is activated and the voltage on the corresponding node is stored.

Each of the current sources CS1-CS3 controls the LED paths of different colors to pass different amounts of current on the LED paths of different colors to balance the total brightness of the LEDs of the respective colors. The method of setting the current amount of the current source CS1-CS3 may be: 1. setting different voltage values VR1, VR2, VR3; 2. setting different resistance values RS1, RS2, RS3; 3. combining the above two.

In any of the above methods, the purpose of setting the brightness of the LEDs on each path can be achieved.

The structure of the current source is not limited to those illustrated in Fig. 6; for example, it can also be fabricated using a bipolar transistor. The enable signal can also be designed in different ways, as shown in Figure 8. Further, the voltage sampling points of the sample-and-hold circuits 31-33 are not limited to NA1-NA3 in FIG. 6, but may also be taken from the nodes NB1-NB3. All such should fall within the scope of the invention.

In the multi-color backlight control circuit 100 shown in FIG. 4, in order to avoid the LED path failure, the path current is too low or no current (for example, the pin is misconnected, the vacant connection or the LED is blown to cause an open circuit), resulting in the voltage supply circuit 11 Pull the voltage unrestricted and set the Under Current Detection (UCD) 41-43 in the circuit. The low current detecting circuits 41-43 may be disposed between the sample and hold circuits 31-33 and the lowest voltage selection circuit 21 as shown, or between the sample and hold circuits 31-33 and the corresponding current sources CS1-CS3. The low current detecting circuit 41-43 allows the lowest voltage selecting circuit 21 to receive the signals 111-113 when the LED path does not have a current under-current or current-free condition. When any one or more of the LED path currents are too low or no current, the low current detecting circuit 41-43 excludes the corresponding signals 111-113 so as not to become the effective input of the lowest voltage selecting circuit 21, and the output voltage Vout is also It will not rise without limit.

Taking the low current detecting circuit 41 as an example, the above concept can be referred to FIG. 10, which is easier to understand. LED current conditions on the path ₁₀₁ i 101, which can be converted into a voltage signal, and then compared with a reference voltage Vuc of the set. The comparison result S41 represents the detection result of the current condition, and the detection signal S41 is used to control the switch SW41 to cut off the switch SW41 when the current on the path 101 is too low or no current. (Of course, depending on the design of the switch SW41, the output of the comparator CP41 may need to be inverted.) It should be noted that this figure is for illustrative purposes only, in fact, the position of the switch does not necessarily need to be placed on the path 111; As long as the equivalent purpose can be achieved.

There are many specific ways to convert the current condition on path 101 into a voltage signal. Two examples are given below. As shown in FIG. 11, if the current source CS1 is fabricated by an NMOS field effect transistor, the gate voltage signal of the transistor can be extracted and input to the low current detecting circuit 41 for comparison with the set reference voltage Vuc. Alternatively, as shown in FIG. 12, the source voltage signal of the transistor may be extracted and input to the low current detecting circuit 41 for comparison with the set reference voltage Vuc. Of course, due to the different positions of the extracted voltage signals, the setting of the reference voltage Vuc may also be different, so as to appropriately detect whether the path 101 has a low current or no current.

In addition to the above, in fact, one or more nodes are appropriately taken on the LED path outside the multi-color backlight control circuit 100, and the same current detection function can be achieved, but an additional pin is required, so it is not Good practice; however, it should still fall within the scope of the invention.

In the case of setting a low current detecting circuit, it is possible that all of the signals 111-113 do not become effective inputs of the lowest voltage selecting circuit 21 at the start of the circuit because there is no current on all of the LED paths. At this time, there is a possibility that the voltage supply circuit 11 cannot start the power supply. If you want to be cautious to avoid such malfunctions, there are many ways to do this. Here are a few examples.

First, when the circuit is started, the low current detecting circuit 41-43 can be activated according to the startup-related signals in the system, such as a power on reset signal or a soft start signal. After the signal S41-S43 is not sent for a while, or the signal is ignored, the time after the power-on can be set by other signals generated during the start of the system (such as the end signal of the soft start) to set the time. End, either after the fixed time is calculated by the timer, or by monitoring the output voltage Vout (usually only one comparator is required), and ending the time after it reaches a certain set value or more. . For the above, please refer to FIG. 13, a boot mask circuit 23 can be provided; the boot mask circuit 23 can generate the masking signal 24 according to any one of the above manners or the like to shield the low current during the startup time. The signals S41-S43 of the detection circuits 41-43 are detected, and after the start-up time is over, the signals S41-S43 are restored. Moreover, the logic and gates in the figure are merely examples; the shielding function can be achieved in any other way. Moreover, the masking signal 24 does not necessarily need to cover all of the detecting signals S41-S43, but only one or a part of them can be shielded.

Next, please refer to FIG. 14 , and the startup circuit can also be used to ensure startup to solve the above problem. In the embodiment, one input is provided in the lowest voltage selection circuit 21, and a startup circuit 28 is provided to activate the circuit. The output of 28 is connected to this input. The purpose of the startup circuit 28 is to provide a valid input signal 110 to the lowest voltage selection circuit 21 for the other signals 111-113 to be cut off for comparison with the reference voltage Vref in the error amplifier 13 to produce the correct The signal 15 is activated by the voltage supply circuit 11. In other words, the startup circuit 28 is designed to generate a voltage signal lower than the reference voltage Vref when the other signals 111-113 are turned off, so that the error amplifier 13 can generate the signal 15 and enter the circuit. There is no longer any impact in the normal working range.

To achieve the above objectives, various methods are feasible. For example, the voltage 110 can be generated from the output voltage Vout, or the 0V input can be given for a short time when the circuit is started, and then the signal 110 is switched to the high voltage level, etc.; The technical person, when thinking about various practices, will not be described here.

In the embodiments of the fourth, ninth, and fourteenth embodiments described above, the sample and hold circuits 31-33 are used to store the corresponding voltage values, and the output of the lowest voltage selection circuit 21 from the sample hold circuits 31-33 is 111-113. Among them, the lowest one is selected, and the input error amplifying circuit 13 is compared with the reference voltage Vref. However, the present invention is not limited to this arrangement. For example, referring to FIG. 15, a multiplexer circuit (MUX) 50 may be used to select a corresponding voltage signal from the nodes NA1-NA3 according to the enable signals EN1-EN3. The input valley detecting circuit 60 has a function of storing a local minimum voltage level for a period of time. Therefore, the output of the valley detecting circuit 60 represents the lowest voltage level among the nodes NA1-NA3. The purpose of selecting the lowest voltage can also be achieved. Similarly, for the sake of safety, the low current detecting circuit 40 may be disposed in the circuit to prevent the circuit from being erroneously caused by an erroneous signal; the low current detecting circuit 40 may be disposed on the right side of the multiplex circuit 50 as shown in the figure. Or set to the left of the multiplex circuit 50. In short, the lowest voltage selection circuit 21 selects the lowest voltage of the same time point in the parallel input, and the valley detecting circuit 60 selects the lowest voltage among the different time points in the sequential input. Even its synthesis is within the scope of the invention.

For a structural example of the valley detecting circuit 60, refer to FIG. 16. The current source 62 of a small current amount slowly charges the capacitor 64. When the voltage across the capacitor 64 is higher than the voltage of the input IN, the capacitor 64 passes through the left operation. The amplifier 66 is discharged until its voltage is equal to the voltage of the input IN, so the voltage of the output OUT will follow the lowest voltage of the input IN.

The present invention has been described with respect to the preferred embodiments, and the above description is only for the purpose of facilitating the understanding of the present invention, and is not intended to limit the scope of the present invention; Various equivalent variations are immediately considered when within the spirit of the invention. For example, the present invention is not limited to a backlight control circuit applied to three colors of RGB, and may be applied to a backlight control circuit of a white LED, or any other backlight control circuit of any color, such as red yellow (RYC, red, yellow, Cyan) three-color backlight control circuit, etc.; two components directly connected in all embodiments can be inserted between circuits that do not affect the meaning of signals, such as delay circuits, etc.; the "backlight" control circuit may not necessarily be controlled "Backlight", but can be any lighting; and so on. Equivalent changes or modifications of the concept and spirit of the invention are intended to be included within the scope of the invention.

10R, 10G, 10B. . . Backlight control circuit

11. . . Voltage supply circuit

13. . . Error amplifier circuit

15. . . Signal

16. . . counter

17,18,19. . . Pulse generator

twenty one. . . Minimum voltage selection circuit

twenty three. . . Start mask circuit

twenty four. . . Masking signal

28. . . Startup circuit

31-33. . . Sample and hold circuit

40. . . Low current detection circuit

41-43. . . Low current detection circuit

50. . . Multiplexed circuit

60. . . Valley detection circuit

62. . . Battery

64. . . Capacitor

66. . . Operational Amplifier

68. . . Dipole

100. . . Multi-color backlight control circuit

101-103. . . LED path

110. . . Start input

111-113. . . Signal

B1-B3. . . Pin

C1. . . Capacitor

CP41-CP43. . . Comparators

CS1-CS3. . . Battery

EN1-EN3. . . Enable signal

G1-G3. . . Pin

NA1-NA3. . . node

NB1-NB3. . . node

R1-R3. . . Pin

RS1-RS3. . . resistance

S1-S3, S41-S43. . . Signal

SW, SW41-SW43. . . switch

Vin. . . Input voltage

Vout, Vout(R), Vout(G), Vout(B). . . The output voltage

Vuc, Vref, VR1-VR3. . . Reference voltage

Schematic description:

Figure 1 is a schematic circuit diagram of the prior art.

Figure 2 illustrates one embodiment of the present invention in which a single multi-color backlight control circuit is used to provide voltage to LED paths of different colors.

Fig. 3 shows an embodiment in which the LEDs of different colors are illuminated at different times.

Fig. 4 is a schematic circuit diagram showing an example of a specific structure of a multicolor backlight control circuit.

Fig. 5 shows an example of a sample and hold circuit.

Fig. 6 shows an example of a current source circuit.

Figure 7 is a waveform diagram illustrating the relationship between the enable signal EN1-EN3 and the signals S1-S3.

Fig. 8 shows another example of the current source circuit.

Fig. 9 is a schematic circuit diagram showing another example of the specific structure of the multicolor backlight control circuit.

Figure 10 illustrates the structure of the low current detection circuit.

Figure 11 and Figure 12 illustrate the connection of the low current detection circuit.

Figure 13 illustrates the practice of activating the masking circuit.

Figure 14 illustrates how to use the startup circuit to ensure startup.

Figure 15 is a schematic circuit diagram showing another embodiment of the present invention.

Figure 16 illustrates the operation of the valley detection circuit.

100. . . Multi-color backlight control circuit

B1-B3. . . Pin

G1-G3. . . Pin

R1-R3. . . Pin

Vin. . . Input voltage

Vout. . . The output voltage

Claims (39)

A multi-color backlight control circuit comprising: a plurality of pins for connecting to a plurality of different color LED paths; and a voltage supply circuit that receives an input voltage and provides a single output voltage to the plurality of different The light-emitting diode path of the color, wherein the number of the light-emitting diodes is different in the path of the light-emitting diodes of at least two different colors, so that the working voltages of the plurality of light-emitting diode paths are similar. The multi-color backlight control circuit of claim 1, wherein the total number of the light-emitting diodes of different colors is the same. The multi-color backlight control circuit according to claim 1, wherein the light-emitting diodes of different colors are sequentially turned on. The multi-color backlight control circuit according to claim 3, wherein the illumination time of the light-emitting diodes is different between at least two light-emitting diode paths of different colors. The multi-color backlight control circuit of claim 4, further comprising a counter and a complex array pulse generator, wherein the complex array pulse generator sequentially generates pulses according to the output of the counter, and controls the at least two The illuminating time of the light-emitting diode on the light-emitting diode path of different colors. The multi-color backlight control circuit of claim 1, wherein the amount of current on at least two different color light-emitting diode paths is different from each other. Such as the multi-color backlight control circuit described in claim 6 of the patent scope, At least two current sources are included to respectively control the amount of current on the path of the at least two different color LEDs. The multi-color backlight control circuit of claim 7, wherein the at least two current sources each have a resistor, and the amount of current can be determined by setting a resistance value thereof. The multi-color backlight control circuit of claim 7, wherein the at least two current sources each have a first reference voltage input, and the current value can be determined by setting a voltage value thereof. The multi-color backlight control circuit of claim 7, wherein the at least two current sources are each controlled by a corresponding enable signal to operate normally when receiving the enable signal. The multi-color backlight control circuit of claim 1, further comprising: a first circuit that extracts voltage from the plurality of different color LED paths and selects the lowest one; The amplifier compares the lowest voltage of the first circuit output with a second reference voltage, and outputs a signal to control the voltage supply circuit. The multicolor backlight control circuit of claim 11, wherein the first circuit includes a plurality of sample and hold circuits to maintain the extracted voltage. The multicolor backlight control circuit of claim 11, wherein the first circuit includes a lowest voltage detection circuit to select a lowest voltage from among the plurality of inputs. For example, the multi-color backlight control circuit described in claim 11 is The first circuit includes a valley detecting circuit to detect and maintain a minimum voltage for a local time. The multi-color backlight control circuit of claim 14, wherein the first circuit comprises a multiplex circuit, and an appropriate input of the valley detecting circuit is selected from the extracted voltages. The multi-color backlight control circuit of claim 11, wherein the first circuit further comprises a low current detecting circuit to exclude one of the extracted voltages lower than a third reference voltage. A backlight control circuit includes: a plurality of pins for connecting to a plurality of light emitting diode paths; and a voltage supply circuit that receives an input voltage and provides a single output voltage to the plurality of light emitting diode paths. In the path of at least two of the light emitting diodes, the number of the light emitting diodes is different, so that the working voltages of the plurality of light emitting diode paths are similar. The backlight control circuit of claim 17, wherein the amount of current on at least two different numbers of light-emitting diode paths is different from each other. The backlight control circuit of claim 18, further comprising at least two current sources for respectively controlling the amount of current on the at least two different numbers of light-emitting diode paths. The backlight control circuit of claim 19, wherein the at least two current sources each have a resistor, and the amount of current can be determined by setting a resistance value thereof. The backlight control circuit of claim 19, wherein The at least two current sources each have a first reference voltage input, and the amount of current can be determined by setting a voltage value thereof. The backlight control circuit of claim 17, further comprising: a first circuit that extracts voltage from the at least two different numbers of light-emitting diode paths and selects the lowest one; an error amplifier, Comparing the lowest voltage of the first circuit output with a second reference voltage, and outputting a signal to control the voltage supply circuit. The backlight control circuit of claim 22, wherein the first circuit comprises at least two sample and hold circuits to maintain the extracted voltage. The backlight control circuit of claim 22, wherein the first circuit includes a minimum voltage detecting circuit to select a lowest voltage from at least two of the inputs. The backlight control circuit of claim 22, wherein the first circuit includes a valley detecting circuit to detect and maintain a minimum voltage for a local time. The backlight control circuit of claim 22, wherein the first circuit comprises a multiplex circuit, and an appropriate input of the valley detecting circuit is selected from the extracted voltages. The backlight control circuit of claim 22, wherein the first circuit further comprises a low current detecting circuit to exclude a lower than a third reference voltage among the extracted voltages. A multi-color backlight control method comprising: For at least two different color LED paths, a single output voltage is provided and the operating voltages of the plurality of LED paths are similar. The multi-color backlight control method of claim 28, further comprising: setting a different number of light-emitting diodes on the at least two different color light-emitting diode paths. The multi-color backlight control method as described in claim 29, further comprising: making the total number of light-emitting diodes of different colors the same. The multi-color backlight control method according to claim 28, wherein the light-emitting diodes of different colors are sequentially turned on. The multi-color backlight control method as described in claim 31, further comprising: causing at least two different color LEDs to have different illumination times. The multi-color backlight control method of claim 28, further comprising: providing different current quantities to the at least two different color LED paths. The multi-color backlight control method of claim 33, further comprising: providing at least two current sources to respectively control the amount of current corresponding to the path of the at least two different color light-emitting diodes. The multi-color backlight control method of claim 28, further comprising: extracting a voltage from the at least two different color LED paths; selecting a lowest one of the extracted voltages; and according to the minimum voltage, Controlling the output voltage. The multicolor backlight control method as claimed in claim 35, further comprising: sampling and maintaining the extracted voltage. The multicolor backlight control method of claim 35, wherein the step of selecting the lowest voltage is to select the lowest voltage of the same time point. The multi-color backlight control method according to claim 35, wherein the step of selecting the lowest voltage is to select the lowest voltage in a local time. The multi-color backlight control method as claimed in claim 35, further comprising: excluding a voltage lower than a reference voltage in the extracted voltage, not as a minimum voltage.