Light source device

Abstract

To provide a light source device capable of reducing a noise radiation amount.SOLUTION: The light-source module has a plurality of side walls, each side LED32 being disposed in a matrix. A plurality of LEDs are connected in series in each row, and the first row Rw1 and the third row Rw3 are connected in parallel to the first driver 6. The second row Rw2 and the fourth row Rw4 are connected in parallel to the second driver 7. In the first row Rw1 and the third row Rw3, a current path is formed so that a current flows in a direction opposite to that in the second row Rw2 and the fourth row Rw4. The first driver 6 and the second driver 7 are configured to supply a current as a PWM signal to each row in synchronization with each other when a common clock signal is input from the controller 5.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a light source device having a configuration in which light emitting elements are arranged in a matrix. [Background technology]

[0002] Light source devices used as backlights for liquid crystal displays or as room lighting devices include a configuration in which a plurality of light emitting diodes (LEDs) are arranged in a matrix. For example, Patent Document 1 discloses a light source device in which LEDs are arranged in a matrix, with a plurality of LEDs in one row connected in series. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5337883 Summary of the Invention [Problem to be solved by the invention]

[0004] In a light source device in which LEDs are arranged in a matrix, the LEDs in each row may be arranged in the same direction and current may flow in the same direction in order to simplify the wiring pattern on the circuit board. However, if current flows in the same direction in each row, the magnetic fields formed by the currents flowing in each row may reinforce each other, which can cause problems such as increased noise radiation.

[0005] An object of the present disclosure is to provide a light source device capable of reducing the amount of noise radiation. [Means for solving the problem]

[0006] The light source device disclosed herein is a light source device in which a plurality of light-emitting elements are arranged in a matrix on a substrate, and the matrix formed by the plurality of light-emitting elements includes a first direction line (Rw1) which is a row in which a plurality of light-emitting elements are connected in series so that the current direction to adjacent light-emitting elements in the row direction is a first direction, and a second direction line (Rw2) which is a row in which a plurality of light-emitting elements are connected in series so that the current direction to adjacent light-emitting elements in the row direction is a second direction that is opposite to the first direction.The light source device disclosed herein is a light source device in which a plurality of light-emitting elements are arranged in a matrix on a substrate, and the matrix formed by the plurality of light-emitting elements includes a first direction line (Rw1) which is a row in which a plurality of light-emitting elements are connected in series so that the current direction to adjacent light-emitting elements in the row direction is a second direction that is opposite to the first direction.The light source device further includes a first drive circuit (6) electrically connected to the first direction line and PWM-controlling the lighting state of the light-emitting elements constituting the first direction line, and a second drive circuit (7) electrically connected to the second direction line and PWM-controlling the lighting state of the light-emitting elements constituting the second direction line, and the first drive circuit and the second drive circuit are configured so that the timing of outputting current in PWM control overlaps.

[0007] In the above configuration, the first directional line and the second directional line formed by the plurality of light-emitting elements are configured so that currents flow in opposite directions. The first and second drivers are also configured so that the timing of passing PWM-controlled currents (i.e., pulsed currents) through the first and second directional lines overlaps. Therefore, the magnetic fields formed by the pulsed currents flowing through the first directional line and the magnetic fields formed by the pulsed currents flowing through the second directional line cancel each other out in accordance with Ampere's law, reducing noise radiation.

[0008] Note that the symbols in parentheses in the claims indicate a correspondence with the specific means described in the embodiments described below as one aspect, and do not limit the technical scope of the present disclosure. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is an exploded perspective view for explaining a schematic configuration of a liquid crystal display. [Figure 2] FIG. 2 is a diagram showing an example of an LED arrangement in a light source module. [Figure 3] FIG. 10 is a diagram for explaining the flow of current in an LED matrix. [Figure 4] 4 is a diagram for explaining the exchange of signals between a control unit and first and second drivers. FIG. [Figure 5] FIG. 10 is a diagram showing an example of detailed current paths for each row. [Figure 6] FIG. 10 is a diagram illustrating another example of the configuration of an LED matrix. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments. The configurations disclosed below may be modified in various ways without departing from the spirit of the present disclosure. Various modified examples may be appropriately combined as long as no technical contradictions arise. The present disclosure also includes configurations that are not explicitly stated and are formed by combining multiple modified examples. In the following description, components having the same function may be given the same reference numerals, and specific descriptions thereof may be omitted. Furthermore, components having the same function may be given the same or similar names, and specific descriptions thereof may be omitted. When only a portion of a configuration is mentioned, descriptions given elsewhere may apply to other parts.

[0011] The light source device of this embodiment is a module used as a backlight for a liquid crystal display 1. The liquid crystal display 1 has a preset up-down direction and left-right direction depending on the orientation of the image display. In this disclosure, the up-down direction may also be referred to as the vertical direction, and the left-right direction may also be referred to as the horizontal direction or width direction. The liquid crystal display 1 may be housed in, for example, a vehicle instrument panel for use. The liquid crystal display 1 has a rectangular display screen. In the following, as an example, the liquid crystal display 1 is assumed to have a landscape-oriented display screen.

[0012] As shown in FIG. 1, the liquid crystal display 1 includes a liquid crystal panel 2, a light source module 3, and a housing 4. Note that some of the figures show an X-axis, a Y-axis, and a Z-axis. The X-axis indicates the horizontal direction (i.e., the longitudinal direction) of the liquid crystal display 1 and the liquid crystal panel 2, and the Y-axis direction indicates the vertical direction (i.e., the direction of the short side). The Z-axis direction is perpendicular to the display screen, and the direction in which image light is output is defined as the positive Z-axis direction. As described below, the negative Z-axis direction is the direction from the liquid crystal panel 2 toward the light source module 3, and may be referred to as the back direction, rear direction, or back side. In the following, the terms front side, front side, etc. refer to the positive Z-axis direction.

[0013] The liquid crystal panel 2 is a component that provides a display screen and has a horizontally elongated rectangular shape in a plan view. The liquid crystal panel 2 is configured by bonding a pair of glass substrates together with a predetermined gap between them, and liquid crystal is sealed between the two glass substrates. One of the glass substrates is provided with switching elements (e.g., TFTs) connected to mutually orthogonal source and gate wiring, pixel electrodes connected to the switching elements, and an alignment film. The other glass substrate may be provided with a color filter in which colored portions such as R (red), G (green), and B (blue) are arranged in a predetermined array, a counter electrode, and an alignment film. Each glass substrate is provided with a polarizing plate on its outer surface. A hard coat filter may be attached to the front surface of the liquid crystal panel 2 to protect the polarizing plate, glass substrate, and the like. The specific configuration of the liquid crystal panel 2 may be modified as appropriate.

[0014] The light source module 3 is a so-called direct type backlight device in which a plurality of LEDs (Light Emitting Diodes) 31 are arranged in a matrix. The light source module 3 is arranged on the back side of the liquid crystal panel 2. Details of the light source module 3 will be described separately later.

[0015] The housing 4 is a member that houses the liquid crystal panel 2 and the light source module 3. The housing 4 may have, for example, a bracket for fixing to the instrument panel of the vehicle, an opening for passing cables through, and the like. The housing 4 has a certain shape. The housing 4 may be made of resin or metal such as aluminum. The housing 4 may also be configured by combining resin parts and metal parts.

[0016] <Light source module> The light source module 3 is configured as a multi-lamp LED board in which a plurality of LEDs 32 are arranged on a board 31. For example, in the light source module 3, the plurality of LEDs 32 are arranged in a matrix of 4 rows and 11 columns, as shown in FIG. 2. That is, the light source module 3 has 44 LEDs 32. Eleven LEDs 32 form one row. Hereinafter, the set of LEDs 32 arranged in a matrix (in other words, the whole) will also be referred to as an LED matrix.

[0017] The intervals between the LEDs 32 in the horizontal direction may be constant. The intervals between the LEDs 32 in the vertical direction may also be constant. The substrate 31 may be a rectangular multi-layer substrate. Screw holes 33 for fixing the light source module 3 to the housing 4 may be provided at the four corners of the substrate 31. The number of rows of the LEDs 32 is not limited to four, and may be set to any number of two or more. The number of columns of the LEDs 32 is not limited to eleven, and may be set to any number of six or more.

[0018] As shown in Fig. 3, a plurality of (here, eleven) LEDs 32 forming each row of the LED matrix are connected in series. That is, the LEDs 32 in each row are connected in series to form parallel current paths. The first row Rw1 and the third row Rw3 are configured so that current flows in a first direction parallel to the row direction, and the second row Rw2 and the fourth row Rw4 are configured so that current flows in a second direction opposite to the first direction.

[0019] Here, the first row Rw1 refers to a set of multiple serially connected LEDs 32 that make up the first row of the LED matrix. Similarly, the second row Rw2, third row Rw3, and fourth row Rw4 also refer to sets of multiple serially connected LEDs 32 that make up the second, third, or fourth row of the LED matrix.

[0020] In each row, the LED 32 located most upstream (i.e., at the beginning) will be referred to as the leading LED. For example, "32a" shown in FIG. 3 indicates the leading LED of the first row Rw1. Also, the LED 32 located most downstream (i.e., at the end) of the row will be referred to as the trailing LED. For example, "32b" shown in FIG. 3 indicates the trailing LED of the first row Rw1.

[0021] The first row Rw1 and the third row Rw3 correspond to the first direction lines. The second row Rw2 and the fourth row Rw4 correspond to the second direction lines. The drive circuits (i.e., drivers) electrically connected to the first direction lines refer to drive circuits electrically connected to the LEDs 32 located at the beginning and end of the first direction lines.

[0022] As shown in FIGS. 3 and 4, in addition to the LED matrix, the substrate 31 is provided with a control unit 5, a first driver 6, and a second driver 7. The control unit 5 may be a microcomputer. Some of the functions of the control unit 5 may be realized by an integrated circuit (IC), a field-programmable gate array (FPGA), or a combination thereof. The control unit 5 is configured to control the first driver 6 and the second driver 7. The first driver 6 and the second driver 7 are configured to PWM (Pulse Width Modulation) control the LEDs 32 connected thereto.

[0023] The first driver 6 is a driver for passing current through the first row Rw1 and the third row Rw3 to drive the LEDs 32 constituting the first row Rw1 and the third row Rw3. The first driver 6 corresponds to a first driving circuit. The first driver 6 may be an IC. The first driver 6 has terminals (also called pins or ports) for inputting and outputting signals, including a PWM input terminal 61, a frequency synchronization terminal 62, an output terminal 63, and an input terminal 64. The PWM input terminal 61 is a terminal to which a PWM control signal (described later) is input. The frequency synchronization terminal 62 is a terminal for synchronizing the switching frequency of the voltage output from the output terminal 63 with an externally input clock signal. The input terminal 64 is one of the input terminals of the first driver 6 and is electrically connected to the cathodes of the end LEDs of the first row Rw1 and the third row Rw3, as described later. The input terminal 64 may also be a ground terminal connected to the circuit ground.

[0024] The first row Rw1 and the third row Rw3 are connected in parallel to the first driver 6. Specifically, the anode of the first LED 32a in the first row Rw1 and the anode of the first LED 32e in the third row Rw3 are electrically connected to an output terminal 63 of the first driver 6. In addition, the cathode of the last LED 32b in the first row Rw1 and the cathode of the last LED 32f in the third row Rw3 are electrically connected to an input terminal 64 of the first driver 6.

[0025] The first driver 6 raises and lowers the output voltage from the output terminal 63 in conjunction with a PWM control signal (described later) to pass a pulse current as a PWM signal through the first row Rw1 and the third row Rw3, thereby lighting them up. In other words, the first driver 6 PWM-controls the lighting states of the LEDs 32 constituting the first row Rw1 and the third row Rw3. For convenience, the current path from the output terminal 63 of the first driver 6, through the first row Rw1 and the third row Rw3, and back to the input terminal 64 is also referred to as the "first path." The pulse current that the first driver 6 passes through the first current path Rt1 under PWM control is also referred to as the "first pulse current." "I1" in FIG. 4 indicates the first pulse current.

[0026] The second driver 7 is a driver for passing a current through the second row Rw2 and the fourth row Rw4 to drive the LEDs 32 that make up the second row Rw2 and the fourth row Rw4. The second driver 7 corresponds to a second drive circuit. The configuration of the second driver 7 may be substantially the same as that of the first driver 6, and includes a PWM input terminal 71, a frequency synchronization terminal 72, an output terminal 73, and an input terminal 74 as terminals (also called pins or ports) for inputting and outputting signals.

[0027] The second row Rw2 and the fourth row Rw4 are connected in parallel to the second driver 7. Specifically, the anode of the first LED 32c of the second row Rw2 and the anode of the first LED 32g of the fourth row Rw4 are electrically connected to an output terminal 73 of the second driver 7. In addition, the cathode of the last LED 32d of the second row Rw2 and the cathode of the last LED 32h of the fourth row Rw4 are electrically connected to an input terminal 74 of the second driver 7.

[0028] The second driver 7 raises and lowers the output voltage from the output terminal 73 in conjunction with a PWM control signal (described later), thereby passing a pulse current as a PWM signal through the second row Rw2 and the fourth row Rw4, thereby lighting up the LEDs 32 that make up these rows. In other words, the second driver 7 PWM-controls the lighting state of the LEDs 32 that make up the second row Rw2 and the fourth row Rw4. For convenience, the current path that runs from the output terminal 73 of the second driver 7 through the second row Rw2 and the fourth row Rw4 and returns to the input terminal 74 is also referred to as the "second path." The pulse current that the second driver 7 passes through the second current path Rt2 during PWM control is also referred to as the "second pulse current." "I2" in FIG. 4 indicates the second pulse current.

[0029] The first driver 6 and the second driver 7 may each have various terminals other than those described above. The first driver 6 and the second driver 7 may each have, for example, an enable terminal. The enable terminal is a terminal for enabling the driver. For example, each driver may be configured to operate when a high-level signal is input to the enable terminal. In the present disclosure, drive circuits (including ICs) for lighting the LED 32, such as the first driver 6 and the second driver 7, are also simply referred to as drivers.

[0030] As shown in Fig. 4, the control unit 5 includes a clock generation unit 51 and a PWM control unit 52. The clock generation unit 51 is configured to generate a clock signal of a predetermined frequency. The clock signal generated by the clock generation unit 51 is input as a common clock to a frequency synchronization terminal 62 of the first driver 6 and a frequency synchronization terminal 72 of the second driver 7. This causes the first driver 6 and the second driver 7 to operate based on the same clock. In other words, the first driver 6 and the second driver 7 operate in synchronization with each other.

[0031] The PWM control unit 52 is configured to PWM-control the multiple LEDs 32 included in the light source module 3. The PWM control unit 52 is configured to generate a square-wave signal (hereinafter referred to as a PWM control signal) of a predetermined frequency for brightness adjustment. The PWM control signal is the source of pulse currents I1 and I2. The larger the duty ratio of the PWM control signal, the longer the power is applied to the LEDs, thereby increasing brightness. The PWM control unit 52 controls the brightness of each LED by adjusting the proportion of time the signal level is high within one cycle of the square wave (i.e., the duty ratio). The target value for controlling the brightness of the LEDs may be constant or may be adjusted according to the external illuminance. The external illuminance is the brightness outside the vehicle and may be determined based on the output signal of an illuminance sensor located on the dashboard or the like. The PWM control signal generated by the PWM control unit 52 is input to a PWM input terminal 61 of the first driver 6 and a PWM input terminal 71 of the second driver 7. As a result, the first driver 6 and the second driver 7 switch the output voltage in accordance with a common PWM control signal input from the control unit 5.

[0032] Because the first driver 6 and the second driver 7 operate based on a common clock, the timing at which the first driver 6 passes current to the first row Rw1 and the third row Rw3 coincides with the timing at which the second driver 7 passes current to the second row Rw2 and the fourth row Rw4. Here, "same" includes "approximately same." The direction of current flow in the first row Rw1 and the third row Rw3 is opposite to the direction of current flow in the second row Rw2 and the fourth row Rw4, and these rows are arranged alternately. Therefore, within the LED matrix, pulse currents flow in opposite directions at approximately the same timing, alternating between rows. With this configuration, the magnetic field generated by the current flowing through each row cancels out the magnetic field generated by adjacent rows according to Ampere's law. This reduces noise emitted from the light source module 3.

[0033] Note that according to the above configuration, the rising timing of the first pulse current output by the first driver 6 and the rising timing of the second pulse current output by the second driver 7 coincide, but the embodiments of the present disclosure are not limited thereto. The rising timing of the first pulse current and the rising timing of the second pulse current may be slightly deviated. As long as the periods during which each current flows, in other words, the periods during which the output level of the output terminal is at a high level, at least partially overlap, the noise radiated from the light source module 3 can be reduced.

[0034] <Operation at power-on> When the power supply of the light source module 3 is turned on, first, the control unit 5 is activated, and boot processing such as initialization is executed. When the initialization is completed, the control unit 5 starts operating each driver by inputting a high-level signal to the enable terminal of each driver. Next, the control unit 5 inputs a common clock signal to the frequency synchronization terminals 62 and 72 of each driver to synchronize each driver. Then, the control unit 5 inputs a PWM control signal having a predetermined duty ratio to each driver.

[0035] Each driver starts operating based on the input of a high-level signal from the control unit 5 to the enable terminal, and further starts controlling the output voltage according to the clock signal based on the input of the clock signal to the frequency synchronization terminal 62. Each driver controls the output voltages of the output terminals 63 and 73 according to the PWM control signal input to the PWM input terminal 61. By inputting a common clock signal and a common PWM control signal to each driver in this way, the timings at which currents flow in each current path will generally coincide.

[0036] <Arrangement direction of LEDs> While FIG. 3 illustrates a mounting pattern in which the orientation of the LEDs 32 is reversed for each row, the orientation of the LEDs for each row may be the same by modifying the wiring pattern for supplying current to each LED 32. Specifically, as shown in FIG. 5, each LED 32 may be mounted on a substrate 31 such that the direction from the anode to the cathode (hereinafter also referred to as the LED current direction) is the positive direction of the Y axis. The circuit configuration shown in FIG. 5 corresponds to a circuit configuration in which each LED is mounted on a substrate so that the current path from the anode terminal to the cathode terminal is perpendicular to the row direction. In the LED layout shown in FIG. 5, the direction of current to adjacent light-emitting elements (LEDs) in the row direction is parallel to the row direction, i.e., the first direction or the second direction, as indicated by P15, P25, P35, and P45 in the figure.

[0037] 5, path sections P11 to P19 represent parts of the current paths in the first row Rw1. Path sections P21 to P29 represent parts of the current paths in the second row Rw2. Path sections P31 to P39 represent parts of the current paths in the third row Rw3. Path sections P41 to P49 represent parts of the current paths in the fourth row Rw4. "91" in the figure represents an anode connection portion, which is a pad on the substrate 31 that electrically connects to the anode of PED 31. "92" in the figure represents a cathode connection portion, which is a pad on the substrate 31 that electrically connects to the cathode of PED 31. The pad here refers to a conductor (e.g., copper foil) provided on the surface of the substrate for mounting an electrical or electronic component.

[0038] In the substrate 31, the wiring pattern may be formed using a surface or an internal layer of the substrate 31 to realize the current path illustrated in FIG. 5. According to this configuration, currents flow in opposite directions in the path sections P11 and P29, canceling each other out based on Ampere's law. Similarly, when focusing on the current flow in the first row Rw1 and the second row Rw2, currents also flow in opposite directions in the combinations of the path sections P15 and P25, P19 and P21, P12 and P14, P16 and P18, P22 and P24, and P26 and P28, canceling each other out based on Ampere's law. Similarly, the path sections in the third row Rw3 and the fourth row Rw4 also cancel each other out in similar combinations. Between the second row Rw2 and the third row Rw3, the currents flow in opposite directions in the combinations of the path sections P23 and P37, and P27 and P33, and therefore the magnetic fields cancel each other out.

[0039] 5, magnetic fields cancel each other out not only between adjacent rows but also between current paths forming a single row (e.g., P12 and P14). This further reduces noise radiation. Furthermore, each LED 32 can be mounted on the substrate 31 facing the same direction, which can improve manufacturing efficiency.

[0040] Each LED 32 may be attached to the substrate 31 so that the current flows from the anode to the cathode in the negative direction of the Y axis. This configuration also corresponds to a configuration in which the direction from the anode to the cathode, i.e., the direction of current flow to the LED, is perpendicular to the row direction.

[0041] Note that one driver can drive only a finite number of LEDs 32, and the maximum number is determined by the specifications of the driver and the connection relationship (parallel or series, etc.) of the multiple LEDs 32 to be operated. The driver of this embodiment may be a driver that can drive up to two columns of 11 or 12 series (corresponding to the above-mentioned rows and lines) in parallel. The number of series refers to the number of LEDs 32 connected in series. The number of LEDs 32 that a driver can drive may be expressed as a combination of the number of series and the number of parallel LEDs.

[0042] As mentioned above, the number of series constituting one row is not limited to 11, but may be determined according to the specifications of the driver, such as 8, 10, 12, or 14. The number of rows (in other words, lines) driven by one driver is also not limited to two, but may be one, three, or four.

[0043] In the above-described embodiment, the number of rows formed so that a current flows in the first direction (i.e., first direction lines) is the same as the number of rows formed so that a current flows in the second direction (i.e., second direction lines), but the circuit configuration is not limited to this. For example, as shown in Figure 6, the number of first direction lines may be one more than the number of second direction lines. In the example shown in Figure 6, the fifth row Rw5 formed so that a current flows in the first direction is connected in parallel to the first driver 6 together with the first row Rw1 and the third row Rw3.

[0044] In consideration of an increase in the number of lines connected in parallel, Fig. 6 shows a configuration in which the number of LEDs 32 constituting one line (in other words, row) is reduced from 11 to 7 as an example, but the number of LEDs 32 constituting each row is not limited to this, and a value according to the driver specifications may be applied. When the number of second direction lines is one less than the number of first lines, each of the multiple second direction lines may be arranged so as to be sandwiched between first direction lines. This circuit configuration also reduces the amount of noise radiation.

[0045] Although the above describes an embodiment in which the control unit 5 includes the clock generating unit 51, the clock generating unit 51 may be provided independently of the control unit 5 (in other words, outside the control unit 5). The clock generating unit 51 may be a crystal oscillation circuit including a crystal resonator. The clock generating unit 51 may be a VCO (Voltage Controlled Oscillator) that uses a crystal resonator as a resonator, i.e., a VCXO (Voltage Controlled Crystal Oscillator). The row direction and column direction may be interchangeable depending on the perspective. The term "row direction" may be replaced with the term "column direction." The term "row direction" is used for the convenience of explaining the relative positional relationship. A configuration in which the term "row direction" is replaced with the term "column direction" is also within the scope of the technical idea of ​​the present disclosure.

[0046] The light source device of the present disclosure may be used for various purposes other than as a backlight for a liquid crystal display. For example, the light source device may be used as a surface light source for an indoor or outdoor lighting device. The light-emitting element may be an LED that outputs white light. However, the light-emitting element may also be an LED that emits light of a color other than white, such as blue, yellow, red, or green. The light-emitting element may also be an RGB-LED that includes a set of three LED elements: a red LED that emits red (R), a green LED that emits green (G), and a blue LED that emits blue (B).

[0047] Furthermore, the light is not limited to visible light, but may include infrared light, ultraviolet light, etc. The multiple light-emitting elements included in the light source device are not limited to LEDs that output visible light, but may also be LEDs that emit infrared light (so-called infrared LEDs, IR-LEDs). The light source device may be used as a light source module for a distance sensor that uses infrared light. Furthermore, the light-emitting elements may be LEDs that emit ultraviolet light (so-called ultraviolet LEDs, UV-LEDs). The light source device of the present disclosure may be used as a surface light source for a sterilization device that uses ultraviolet light. [Explanation of symbols]

[0048] 1 liquid crystal display, 2 liquid crystal panel, 3 light source module, 32·32a to 32h LEDs (light emitting elements), 5 control unit, 51 clock generation unit, 6 first driver (first drive circuit), 7 second driver (second drive circuit), Rw1 first row (first direction line), Rw2 second row (second direction line), Rw3 third row (first direction line), Rw4 fourth row (second direction line)

Claims

1. A light source device in which a plurality of light emitting elements are arranged in a matrix on a substrate, The matrix formed by the plurality of light-emitting elements is a first direction line (Rw1) in which a plurality of the light emitting elements are connected in series so that the direction of current flow to adjacent light emitting elements in the row direction is a first direction; a second direction line (Rw2) in which a plurality of the light emitting elements are connected in series so that the direction of a current to adjacent light emitting elements in the row direction is a second direction opposite to the first direction, a first driving circuit (6) electrically connected to the first direction line and controlling the lighting state of the light-emitting elements constituting the first direction line by PWM (Pulse Width Modulation); a second drive circuit (7) electrically connected to the second direction line and PWM-controlled to turn on and off the light emitting elements constituting the second direction line; The light source device is configured such that the first drive circuit and the second drive circuit output currents at timings that overlap with each other under PWM control.

2. a clock generating unit (51) that generates a clock signal of a predetermined frequency and inputs the clock signal to each of the first drive circuit and the second drive circuit; The light source device according to claim 1 , wherein each of the first drive circuit and the second drive circuit is configured to operate in accordance with the clock signal input from the clock generation unit.

3. Each of the plurality of light-emitting elements is an LED (Light Emitting Diode) and has an anode terminal and a cathode terminal, The light source device according to claim 1 , wherein each of the plurality of light-emitting elements is mounted on the substrate such that a current path from the anode terminal to the cathode terminal is oriented perpendicular to the row direction.

4. The light source device according to claim 1 , wherein the number of the light-emitting elements constituting each row of the matrix is ​​10 or more.

5. the number of rows of the matrix is ​​four or more; A plurality of the first direction lines are provided, A plurality of the second direction lines are provided, the first direction lines and the second direction lines are alternately arranged, the plurality of first direction lines are connected in parallel to the first driving circuit; The light source device according to claim 1 , wherein the plurality of second direction lines are connected in parallel to the second drive circuit.

6. The light source device according to claim 5 , wherein the number of the first direction lines is the same as the number of the second direction lines.

7. the number of the first direction lines is one more than the number of the second direction lines; The light source device according to claim 5 , wherein each of the plurality of second direction lines is arranged so as to be sandwiched between the first direction lines.

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