WO2023238887A1

WO2023238887A1 - Light-emitting element drive circuit and lighting device using same, display device, and electronic apparatus

Info

Publication number: WO2023238887A1
Application number: PCT/JP2023/021137
Authority: WO
Inventors: 知彦鷲見
Original assignee: ローム株式会社
Priority date: 2022-06-08
Filing date: 2023-06-07
Publication date: 2023-12-14

Abstract

This light-emitting element drive circuit comprises a plurality of current drivers respectively connected to light-emitting elements of a plurality of channels, and a controller configured to control the plurality of current drivers. The controller is configured to perform ON/OFF switching of the current drivers of one channel and to set the on-duty of the current drivers of the remaining channels to 100% if the light control ratio is a first light control ratio greater than 100×(N-1)/N% and less than 100%, where N is the number of channels in the plurality of channels.

Description

Light-emitting element drive circuits, lighting devices, display devices, and electronic devices using the same

The invention disclosed herein relates to a drive circuit for a light emitting element.

As a backlight for liquid crystal display (LCD) panels, it is an excellent alternative to conventional CCFL (Cold Cathode Fluorescent Lamp) and EEFL (External Electrode Fluorescent Lamp) in terms of long life, low power consumption, and wide color gamut. A white light emitting diode (hereinafter abbreviated as LED) having special characteristics is used.

Incidentally, Patent Document 1 can be mentioned as an example of the conventional technology related to the above.

JP2014-207204A

Current dimming (analog dimming) and PWM dimming are known as methods for controlling the brightness of LEDs for backlights. In current dimming, the amount of drive current flowing through the light emitting element is adjusted according to target brightness. In PWM dimming, the effective brightness of the light emitting element is controlled by switching the drive current and adjusting the time ratio (duty ratio) between the lighting period in which the drive current flows and the lighting period in which the drive current is cut off. .

In recent years, the contrast ratio required for lighting devices has been increasing more and more. For example, when the drive current I _LED is changed by current dimming from a maximum current corresponding to maximum brightness to a minimum current of 0.1% thereof, the contrast ratio is 1000:1. Further, when the duty ratio is changed in the range of 100% to 0.1% by PWM dimming, the contrast ratio is 1000:1.

Therefore, the contrast ratio of a lighting device is constrained in current dimming by the minimum amount of current that the current driver can generate, and in PWM dimming by the minimum pulse width. Alternatively, it is possible to increase the contrast ratio by combining analog dimming and PWM dimming, but even in this case, there is an upper limit to the contrast ratio.

Furthermore, when driving and dimming LEDs, there is a method of simultaneously dimming all LEDs using PWM dimming. When all LEDs are dimmed at the same time, the load fluctuation associated with PWM dimming increases, resulting in noise. In order to suppress the output voltage ripple and improve this noise, it is necessary to increase the capacitance of the capacitor, which leads to an increase in cost.

Rather than dimming all LEDs at the same time, by dimming them at different timings using Phase Shift, load fluctuations can be suppressed to some extent. Therefore, even if the capacitance of the output capacitor is reduced, noise can be suppressed, leading to cost reduction. However, even if Phase Shift is implemented, the number of times of switching itself does not decrease, so a reduction in switching noise cannot be expected.

The light emitting device driving circuit disclosed herein includes a plurality of current drivers connected to each of the plurality of channels of light emitting devices, and a controller configured to control the plurality of current drivers, The controller is configured to turn on the current driver of one channel when the number of channels of the plurality of channels is N and the dimming rate is a first dimming rate that is greater than 100×(N-1)/N% and smaller than 100%. /OFF switching, and the on-duty of the current drivers of the remaining channels is set to 100%.

The lighting device disclosed in this specification includes a plurality of channels of light emitting elements and a light emitting element driving circuit having the above configuration for driving the plurality of channels of light emitting elements.

The electronic device disclosed herein includes a display panel and a lighting device configured as described above.

The display device disclosed herein includes a display panel and a lighting device configured as described above.

According to the light emitting element drive circuit, lighting device, electronic device, and display device disclosed in this specification, it is possible to reduce noise, reduce cost, and reduce switching noise.

FIG. 1 is a diagram showing the configuration of a display device including a backlight device according to an embodiment. FIG. 2A is a diagram illustrating an example of an arrangement layout of light emitting elements of a lighting device. FIG. 2B is a diagram showing a substrate on which a light emitting element is mounted. FIG. 3 is a diagram showing another example of the arrangement layout of light emitting elements of the lighting device. FIG. 4 is a diagram showing an example of dimming control when the dimming rate is 90%. FIG. 5 is a diagram showing an example of dimming control when the dimming rate is 50%. FIG. 6 is a diagram showing an example of dimming control when the dimming rate is 0.25%. FIG. 7 is a diagram showing changes in load when the dimming rate is 20%. FIG. 8 is a diagram showing a comparison with the prior art. FIG. 9A is a diagram illustrating an example of an electronic device including a lighting device. FIG. 9B is a diagram illustrating an example of an electronic device including a lighting device.

FIG. 1 is a diagram showing the configuration of a display device including a lighting device according to an embodiment.

The display device 100 includes an LCD (Liquid Crystal Display) panel 101 and a lighting device 1. The illumination device 1 is configured to emit backlight from the back surface of the LCD panel 101.

The lighting device 1 has a multi-channel configuration, and includes N (N is an integer of 2 or more) channel light emitting element strings 10_1 to 10_N, a light emitting element drive circuit 2, a capacitor C1, and a light guide plate (not shown in FIG. 1). and.

Each of the N light emitting element strings 10_1 to 10_N includes M light emitting units 11 (M is an integer of 2 or more) connected in series. For example, each light emitting unit 11 includes one light emitting element or a plurality of light emitting elements connected in series. The light emitting element is, for example, an LED.

The M light emitting units 11 included in the same light emitting element string 10 (channel) are configured to have substantially the same size (light emitting area) so that they emit light with the same brightness.

Hereinafter, the i-th light-emitting unit 11 of the light-emitting element string 10_j of the j-th (1≦j≦N) channel CHj will be referred to as a light-emitting unit (11_j, i). In this embodiment, for the purpose of simplifying the description and facilitating understanding, a case will be described in which all the light emitting units (11_1, 1) to (11_N, M) have the same size (light emitting area).

The LCD panel 101 is divided into a plurality of M regions 102_1 to 102_M in the direction of one side thereof (in the present embodiment, the X direction in the figure). Dividing here does not mean that the LCD panel 101 is physically divided, but rather that it is divided into virtual areas.

One side of the LCD panel 101 (the i-th light emitting units (11_1, i) to (11_N, i) included in each of the N light-emitting element strings 10_1 to 10_N in this embodiment are allocated to the i-th area 102_i). The light emitting units (11_1,i) to (11_N,i) of the plurality of channels CH1 to CHN assigned to the i-th region 102_i are arranged as the light emitting module 12_i. to be called.

A dimming signal PWMCLK that instructs the brightness of the backlight is input to the light emitting element drive circuit 2 from the outside. The light emitting element drive circuit 2 is configured to be able to independently turn on and off the light emission of each of the N light emitting element strings 10_1 to 10_N in accordance with the dimming signal PWMCLK.

The light emitting element drive circuit 2 includes a plurality of current drivers 3_1 to 3_N connected to each of the plurality of channels of light emitting elements, a DC/DC converter 4 configured to supply voltage to the plurality of channels of light emitting elements, and a plurality of current drivers 3_1 to 3_N connected to each of the plurality of channels of light emitting elements. A controller 5 is provided, configured to control the current driver and the DC/DC converter.

N current drivers 3_1 to 3_N are provided for each light emitting element string 10_1 to 10_N. The j-th (1≦j≦N) current driver 3_j is provided in series with the corresponding light emitting element string 10_j. Specifically, the current driver 3_j is provided between the cathode of the corresponding light emitting element string 10_j and the ground line. Alternatively, the current driver 3_j may be provided between the light emitting element string 10_j and the output line of the DC/DC converter 4. Current driver 3_j generates drive current I _LEDj . The current driver 3 may use any known technology, and its configuration is not limited.

The controller 5 performs PWM (pulse width modulation) dimming by controlling the current drivers 3_1 to 3_N in accordance with the dimming signal PWMCLK. In PWM dimming, the time ratio over which the drive current I _LED flows is controlled.

The controller 5 is capable of independently turning on and off each of the current drivers 3_1 to 3_N for the purpose of brightness adjustment according to the dimming signal PWMCLK.

The DC/DC converter 4 supplies a driving voltage V _CC across the pair of light emitting element string 10 and current driver 3 of each channel CH1 to CHN, that is, between its output line and the ground line. Capacitor C1 suppresses ripple in drive voltage V _CC .

The controller 5 controls the DC/DC so that the voltage drop of the N current drivers 3_1 to 3_N, that is, the lowest voltage among the cathode voltages V _LED1 to V _LEDN of the light emitting element strings 10_1 to 10_N approaches a predetermined reference voltage. Controls converter 4.

FIG. 2A is a diagram showing an example of the arrangement layout of light emitting elements of a lighting device. FIG. 2A is a diagram showing an example of an arrangement layout when the number of channels is four. The lighting device 1 includes light emitting element strings 10_1 to 10_4 provided for each of a plurality of channels CH1 to CH4, a light emitting element drive circuit 2 for driving the light emitting element strings 10_1 to 10_4, and a light guide plate 103. In the arrangement layout example shown in FIG. 2A, the light emitting modules 12_i are arranged to illuminate the corresponding area 102_i (see FIG. 1), and the light emitting element strings 10_1 to 10_4 (all the light emitting elements connected to the light emitting element drive circuit 2) are arranged to illuminate the corresponding area 102_i (see FIG. 1). ) and has all-channel light emitting elements. In the arrangement layout example shown in FIG. 2A, the light emitting elements are shown arranged in four rows for each of the plurality of channels CH1 to CH4 in order to make it easier to understand the electrical connection state of the light emitting element strings 10_1 to 10_4. However, in reality, as shown in FIG. 2B, it is desirable that the light emitting elements of the plurality of channels CH1 to CH4 (all the light emitting elements connected to the light emitting element drive circuit 2) are lined up in a line. This makes it possible to reduce the area of the substrate 6 on which the light emitting elements of the plurality of channels CH1 to CH4 (all the light emitting elements connected to the light emitting element drive circuit 2) are mounted. The board 6 is preferably a flexible circuit board. When the board 6 is a flexible circuit board, the work of attaching the board 6 to the casing of the display device 100 becomes easier.

FIG. 2A illustrates the light guide plate 103, which is not shown in FIG. Each of the light emitting element strings 10_1 to 10_4 includes a plurality of LEDs connected in series, and by entering the light from the light emitting element strings 10_1 to 10_4 driven by the light emitting element drive circuit 2 from the side of the light guide plate 103, The LCD panel 101 (see FIG. 1) can be illuminated uniformly. The LCD panel 101 is arranged in front of the light guide plate 103 and facing the light guide plate 103. Further, the light emitting element drive circuit 2 is housed in a semiconductor package 7. Four terminals T1 to T4, which are exposed from the semiconductor package 7 and output drive currents I _LED1 to I _LED4 for each of the plurality of channels CH1 to CH4, are adjacent to each other. Although the arrangement of the plurality of terminals that output drive current is not limited to the example shown in FIG. 2A, it is desirable that at least two of the plurality of terminals that output drive current are adjacent to each other. This facilitates wiring between the light emitting element drive circuit 2 and the light emitting elements.

Even if an abnormality occurs in channel CH1 and the light goes out, all the divided areas can be illuminated using the remaining channels CH2 to CH4. With the light emitting element arrangement layout as shown in FIG. 2A, even if an abnormality occurs in a certain channel, the entire LCD panel 101 can be illuminated, although the dimming will be darker than the target dimming. .

On the other hand, if the light emitting elements are arranged in a layout as shown in FIG. 3, if an abnormality occurs in a certain channel and the light is turned off, a certain specific area will become dark. Therefore, the brightness differs depending on the location of the LCD panel 101. In view of such disadvantages, the lighting device according to the embodiment does not adopt the arrangement layout of the light emitting elements as shown in FIG. 3.

FIG. 4 is a diagram showing an example of dimming control when the dimming rate is 90%. A dimming signal PWMCLK adjusted to have an on-duty of 90% is input to the controller 5.

The left side of FIG. 4 shows the case of the prior art, in which the ratio of on-duty and off-duty of the duty cycle is the same as that of the dimming signal PWMCLK in all channels CH1 to CH4, and the controller 5 controls the current Turns ON/OFF the drivers 3_1 to 3_4.

The right side of FIG. 4 shows the case of a method controlled by the configuration of the present embodiment, in which the ratio of on-duty and off-duty of the duty cycle is different from that of the prior art and different from the dimming signal PWMCLK. The controller 5 turns on the current drivers 3_1 to 3_3 with an on duty of 100% for channels CH1 to CH3, and switches ON/OFF the current driver 3_4 only for channel CH4 with an on duty of 60%. In this case, the total on-duty of the four channels is 360%, and when the total on-duty is divided by the number of channels, 4, the dimming rate is 90%.

Although FIG. 4 shows the case where the number of channels is 4, when the number of channels is N, the controller 5 has a dimming rate of 100×(N-1)/N% (N is the number of channels). When the first dimming rate is larger and smaller than 100%, the current driver of one channel is switched ON/OFF in the duty cycles of multiple current drivers, and the on-duty of the current drivers of the remaining channels is set to 100%. configured to do so. For example, when the number of channels is 4, the first dimming rate is greater than 75% and less than 100%.

FIG. 5 is a diagram showing an example of dimming control when the dimming rate is 50%. The left side of FIG. 5 shows the case of the prior art, in which the ratio of the on-duty and off-duty of the duty cycle is the same as that of the dimming signal PWMCLK, and the controller 5 controls channels CH1 to The current drivers 3_1 to 3_4 of CH4 are switched ON/OFF.

The right side of FIG. 5 shows the case of the control method according to the configuration of this embodiment, in which the controller 5 turns on the current drivers 3_1 to 3_2 with an on-duty of 100% for channels CH1 to CH2, and turns on the current drivers 3_1 to 3_2 for channels CH1 to CH2. Since the on-duty for ~CH4 is 0%, the current drivers 3_3 to 3_4 are turned off.

In this case, the total on-duty of the four channels is 200%, and when the total on-duty is divided by the number of channels, 4, the dimming rate is 50%. In FIG. 5, the controller is configured to control the plurality of current drivers such that at the third dimming rate, there are both a channel with an on-duty of 0% and a channel with an on-duty of 100%. be done. For example, when the number of channels is 4, the third dimming rate is 75%, 50%, 25%, etc. The third light control rate is smaller than the first light control rate, is 100/N% or more, and is divisible by 100/N%.

FIG. 6 is a diagram showing an example of dimming control when the dimming rate is 0.25%. The left side of FIG. 6 shows the case of the prior art, in which the ratio of the on-duty and off-duty of the duty cycle is the same as that of the dimming signal PWMCLK, and the controller 5 controls channels CH1 to The current drivers 3_1 to 3_4 of CH4 are switched ON/OFF.

The right side of FIG. 6 shows the case of the control method according to the configuration of this embodiment, in which the controller 5 switches the current driver 3_1 ON/OFF with the on-time duty of only channel CH1 being 1%, and channels CH2 to Since the on-duty of CH4 is 0%, current drivers 3_2 to 3_4 are turned off. The total on-time duty of the four channels is 1%, and when the total on-time duty is divided by the number of channels, the dimming rate is 0.25%.

Although FIG. 6 shows the case where the number of channels is 4, the dimming rate when the minimum value of the on-duty of the dimming signal PWMCLK is 1% and the number of channels is N is the total on-time of N channels. The duty is 1%, and if the duty of the total on-time is divided by the number of channels, the dimming rate can be set to 1/N%. In this way, the dimming rate can be narrowed down to the value obtained by dividing the minimum value of the duty setting range of the on-time of the duty cycle by the number of channels.

In FIG. 6, the controller switches the current driver of one channel ON/OFF when the dimming rate is a fourth dimming rate smaller than 100/N%, and sets the on-duty of the current drivers of the remaining channels to 0. % of the current driver. For example, when the number of channels is 4, the fourth dimming rate is less than 25%. The fourth light control rate is a light control rate smaller than 100/N%.

Although not illustrated in this specification, the controller controls a channel with an on-duty of 0%, a channel with an on-duty of 100%, and a channel that performs ON/OFF switching at the second dimming rate. The device is configured to control a plurality of current drivers such that one channel exists. For example, when the number of channels is 4, the second dimming rate is greater than 50% and less than 75%. The second light control rate is a light control rate that is smaller than the first light control rate and larger than 100/N% and produces a remainder when divided by 100/N%.

At the same dimming rate, the channel for ON/OFF switching of the current driver may be configured to be fixed. When using this configuration, the controller receives the abnormality detection signal output from the abnormality detection section, determines which channel of the light emitting element in which the abnormality has occurred based on the abnormality detection signal, and then A current driver connected to an element may be excluded from candidates for lighting.

If the channel for ON/OFF switching of the current driver is configured to be fixed at the same dimming rate, only the same channel will be switched, so there is a risk that element deterioration will occur only in a specific channel. Therefore, for example, a configuration may be adopted in which the channel for ON/OFF switching of the current driver is switched every time the current driver is activated or every specific cycle using a counter. Alternatively, if the controller receives a frame switching signal from the display panel, it is also possible to switch in synchronization with the frame cycle of the display panel. When the current driver is configured to switch between ON/OFF channels at the same dimming rate, it is possible to reduce element deterioration in only a specific channel.

In addition, when an abnormality occurs, the controller receives the abnormality detection signal output from the abnormality detection section and detects the abnormality, just as when fixing the channel for ON/OFF switching of the current driver at the same dimming rate. Based on the signal, the controller may determine which channel of the light emitting element the abnormality has occurred in, and remove the current driver connected to the light emitting element in which the abnormality has occurred from the candidates for lighting.

FIG. 7 is a diagram showing changes in load when the dimming rate is 20%. Switching the current driver ON causes a load variation of 100 mA per channel. The left side of FIG. 7 shows the case of the prior art, and when the number of channels is four, all four channels switch at the same timing, so the total load is 400 mA. As described above, in the case of the conventional technology, as the load fluctuation increases, the input/output ripple voltage increases. Therefore, noise occurs.

The middle side of Figure 7 shows the case of the conventional technology (Phase Shift), which differs from the conventional technology on the left side of Figure 7 in that all channels are not switched at the same timing, but each channel is switched at different timings. Perform switching. By performing switching channel by channel in this manner, the TOTAL load becomes 100 mA, and the load fluctuation becomes small. By reducing the load fluctuation, the input/output ripple voltage becomes smaller, and noise is reduced. However, since the number of times of switching is not reduced, it cannot be expected that switching noise will be reduced.

The right side of FIG. 7 shows a method controlled by the configuration of this embodiment, in which only one channel is switched, and the remaining channels are turned off because their on-duty is 0%. In the case of the method controlled by the configuration of this embodiment, since only one channel is switched, the TOTAL load is 100 mA. The number of switching times can be significantly reduced compared to the case of the conventional technology (Phase Shift). Therefore, it is possible to reduce noise and also to suppress the occurrence of switching noise. Further, when a capacitor is used to suppress ripple, the capacitance of the capacitor can be reduced, and costs can be reduced.

FIG. 8 is a diagram showing a comparison with the conventional technology. To summarize the contents explained with reference to FIG. 7, in the case of the control method according to the configuration of this embodiment, only one channel is switched, so that load fluctuations are small and input/output ripple voltages are small. Therefore, noise can also be suppressed and the size of the capacitor can be reduced. Furthermore, since the number of times of switching is small, generation of switching noise can also be suppressed. It can be seen that there are advantages compared to the conventional technique and the conventional technique (Phase Shift). Furthermore, it is also possible to expand the range of dimming ratios compared to the conventional technology.

<Other variations>
Although the explanation has been given using PWM dimming, the present invention is not limited to PWM dimming, and pulse modulation dimming other than PWM dimming may be used. Examples of pulse modulation dimming other than PWM dimming include PFM (pulse frequency modulation) dimming and PDM (pulse density modulation) dimming. Furthermore, by combining PWM dimming and analog dimming, it is possible to further increase the contrast ratio. Taking 4 channels as an example, when a current of XmA is flowing and the on-duty of all 4 channels becomes the same value (for example, 100%) as the maximum on-duty of the dimming signal PWMCLK, analog dimming is performed. It can be made even brighter by changing the current from XmA to YmA. Note that Y only needs to be a larger value than X.

Furthermore, in the case of 4 channels as an example, when a current of XmA is flowing and the total on-duty of the 4 channels becomes the same value as the minimum value of the on-duty of the dimming signal PWMCLK (for example, 1%), It is also possible to make it even darker by changing the current from XmA to ZmA using analog dimming. Note that Z may be a value smaller than X.

Next, the application of the lighting device 1 will be explained. 9A and 9B are diagrams showing an example of an electronic device including the lighting device 1. The electronic device 200 in FIG. 9A is a display device such as a television, a car navigation system, or a PC. In FIG. 9B, the electronic device 200 is a tablet PC, a PDA (Personal Digital Assistant), a mobile phone terminal, or the like. Electronic device 200 includes a housing 201 and an LCD panel 101. The light emitting element string 10 is placed on the back of the LCD panel 101 as a backlight.

In addition to the above embodiments, the configuration of the present invention can be modified in various ways without departing from the spirit of the invention. The above embodiments should be considered to be illustrative in all respects and not restrictive, and the technical scope of the present invention is indicated by the claims rather than the description of the above embodiments. It should be understood that all changes that come within the meaning and range of equivalence of the claims are included.

The light emitting element drive circuit described above includes a plurality of current drivers connected to each of the plurality of channels of light emitting elements, and a controller configured to control the plurality of current drivers. is N, and when the dimming rate is the first dimming rate greater than 100×(N-1)/N% and less than 100%, the current driver of one channel is switched ON/OFF, and the current driver of the remaining channels is switched on/off. The current driver is configured to have an on-duty of 100% (first configuration).

Further, in the light emitting element drive circuit having the first configuration, the controller turns on the light at a second dimming rate which is smaller than the first dimming rate and is larger than 100/N% and produces a remainder when divided by 100/N%. A plurality of current drivers are configured to be controlled so that there are a channel with a duty of 0%, a channel with an on-duty of 100%, and a channel that performs ON/OFF switching (second configuration). .

Further, in the light emitting element drive circuit having the first configuration or the second configuration, the controller controls the controller at a third dimming rate which is smaller than the first dimming rate and is 100/N% or more and is divisible by 100/N%. , a plurality of current drivers are controlled so that there are both a channel with an on-duty of 0% and a channel with an on-duty of 100% (third configuration).

Further, in the light emitting element drive circuit having any of the first to third configurations above, the controller controls ON/OFF switching of the current driver of one channel when the fourth dimming rate is smaller than 100/N%. (fourth configuration).

In addition, in the light emitting element drive circuit having any of the first to fourth configurations above, when an abnormality occurs in the light emitting element, the controller controls the current driver connected to the abnormal light emitting element to turn off the light. (fifth configuration).

Further, in the same rate dimming ratio that is any one of the first to fifth configurations, the channel for switching ON/OFF of the current driver is configured to be fixed (sixth configuration).

In addition, in the same rate dimming ratio that is any one of the first to fifth configurations, the channel for switching ON/OFF of the current driver is configured to be switched (seventh configuration).

Further, the light emitting element drive circuit having the seventh configuration is configured to switch the channel for ON/OFF switching of the current driver each time it is activated or at a specific cycle using a counter. (Eighth configuration).

Furthermore, in the case where the controller receives a frame switching signal from the display panel, the light emitting element drive circuit having the seventh configuration has a channel for switching the current driver ON/OFF in synchronization with the frame period of the display panel. configured to switch (ninth configuration).

Further, in the light emitting element driving circuit having any one of the first to ninth configurations, the light emitting element driving circuit is housed in a semiconductor package, exposed from the semiconductor package, and generated by each of the plurality of current drivers. At least two of the plurality of terminals that output each of the plurality of drive currents are configured to be adjacent to each other (tenth configuration).

Furthermore, the lighting device described above has a configuration (eleventh configuration) including a light emitting element drive circuit having any one of the first to tenth configurations and the plurality of channels of light emitting elements.

Furthermore, the electronic device described above has a configuration (twelfth configuration) that includes a display panel and a lighting device that is the eleventh configuration.

Further, the electronic device having the twelfth configuration includes a plurality of light emitting units, the display panel is divided into a plurality of virtual regions, and each of the plurality of light emitting units illuminates the corresponding region. The light emitting device is arranged as shown in FIG.

Further, in the electronic device having the thirteenth configuration, the plurality of channels of light emitting elements are arranged in a line (fourteenth configuration).

Furthermore, the display device described above has a configuration (fifteenth configuration) that includes a display panel and a lighting device that is the eleventh configuration.

Further, the display device having the fifteenth configuration includes a plurality of light emitting units, the display panel is divided into a plurality of virtual regions, and each of the plurality of light emitting units illuminates the corresponding region. The light emitting device is arranged as shown in FIG.

Further, in the display device having the sixteenth configuration, the plurality of channels of light emitting elements are arranged in a line (seventeenth configuration).

1 Lighting device 2 Light emitting element drive circuit 3_1~3_N Current driver 4 DC/DC converter 5 Controller 6 Substrate 7 Semiconductor package 10_1~10_N Light emitting element string 11 Light emitting unit 12_1~12_M Light emitting module 100 Display device 101 LCD panel 102_1~102_M Area 103 Light guide plate 200 Electronic equipment 201 Housing C1 Capacitor T1~T4 Terminal

Claims

a plurality of current drivers connected to each of the light emitting elements of the plurality of channels;
a controller configured to control the plurality of current drivers;
Prepare,
The controller controls the current driver of one channel when the number of channels of the plurality of channels is N and the dimming rate is a first dimming rate that is larger than 100×(N-1)/N% and smaller than 100%. A light emitting element drive circuit configured to perform ON/OFF switching and set the on-duty of the current driver of the remaining channels to 100%.
The controller controls the channel where the on-duty is 0% and the on-duty is 100% at a second dimming rate that is smaller than the first dimming rate and larger than 100/N% and produces a remainder when divided by 100/N%. The light emitting element drive circuit according to claim 1, configured to control the plurality of current drivers so that there is one channel and one channel that performs ON/OFF switching.
The controller sets the on-duty of the current driver of at least one channel to 0% at a third dimming rate that is smaller than the first dimming rate, is 100/N% or more and is divisible by 100/N%, and sets the on-duty of the current driver of at least one channel to 0%; The light emitting element drive circuit according to claim 1 or 2, configured to control the plurality of current drivers so that the on-duty of the current driver of the channel is 100%.
The controller is configured to turn on/off the current driver of one channel and set the on-duty of the current drivers of the remaining channels to 0% when a fourth dimming rate is smaller than 100/N%. The light emitting element driving circuit according to claim 1, wherein the light emitting element driving circuit is configured.
Any one of claims 1 to 4, wherein when an abnormality occurs in the light emitting element, the controller is configured to remove the current driver connected to the light emitting element in which the abnormality has occurred from candidates for lighting. 2. The light emitting element drive circuit according to item 1.
The light emitting element drive circuit according to any one of claims 1 to 5, configured to fix a channel for ON/OFF switching of the current driver at the same dimming rate.
The light emitting element drive circuit according to any one of claims 1 to 5, configured to switch a channel for ON/OFF switching of the current driver at the same dimming rate.
The light emitting element drive circuit according to claim 7, wherein the light emitting element drive circuit is configured to switch the channel for ON/OFF switching of the current driver every time the current driver is activated or every specific cycle using a counter.
8. The controller according to claim 7, wherein when the controller receives a frame switching signal from a display panel, the controller is configured to switch a channel for ON/OFF switching of the current driver in synchronization with a frame period of the display panel. Light emitting element drive circuit.
The light emitting element driving circuit is housed in a semiconductor package,
10. At least two of the plurality of terminals exposed from the semiconductor package and outputting each of the plurality of drive currents generated by each of the plurality of current drivers are adjacent to each other. The light emitting element drive circuit described above.
A light emitting element drive circuit according to any one of claims 1 to 10,
the multi-channel light emitting device;
A lighting device comprising:
a display panel;
The lighting device according to claim 11;
Electronic equipment.
Equipped with multiple light emitting units,
The display panel is divided into a plurality of virtual areas,
13. The electronic device according to claim 12, wherein each of the plurality of light emitting units is arranged so as to illuminate the corresponding region, is part of the plurality of channels of light emitting elements, and has light emitting elements of all channels.
The electronic device according to claim 13, wherein the plurality of channels of light emitting elements are arranged in a line.
a display panel;
The lighting device according to claim 11,
A display device comprising:
Equipped with multiple light emitting units,
The display panel is divided into a plurality of virtual areas,
16. The display device according to claim 15, wherein each of the plurality of light emitting units is arranged to illuminate the corresponding region, is part of the plurality of channels of light emitting elements, and has light emitting elements of all channels.
The display device according to claim 16, wherein the plurality of channels of light emitting elements are arranged in a line.