Light emitting element driving device

Abstract

The connection terminals corresponding to the plurality of channels are configured to be connectable to a light emitting unit so that a drive current can be supplied to the light emitting unit via the connection terminals individually for each channel. During a non-supply period of the drive current to the light emitting unit, a sensing process is performed to sense a particular failure. The sensing process includes a first comparison process by which a voltage at one of the two connection terminals is compared with a judgment voltage in a case where a pull-up current is supplied to the other connection terminal, and a second comparison process by which a voltage at the other connection terminal is compared with the judgment voltage in a case where the pull-up current is supplied to the one connection terminal.

Description

Technical Field

[0001] This disclosure relates to a light-emitting element driving device. Background Technology

[0002] An LED driver drives a light-emitting unit, including a light-emitting diode (LED). Typically, an LED driver is an electronic component constructed by encapsulating a semiconductor integrated circuit within a package (housing) formed of resin, and has multiple external terminals exposed outside the package. These external terminals include multiple connection terminals (LED connection terminals) that connect to different light-emitting units. By individually controlling the brightness of each light-emitting unit, local dimming (local brightness adjustment) can be achieved.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2010-182883 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] When an LED driver is mounted on a circuit board, two adjacent connection terminals may unintentionally short-circuit together due to solder or other reasons. Two such connection terminals can be connected together across a relatively low-resistance element. Such a fault makes it impossible to supply the desired drive current to the light-emitting unit. A highly desirable technique is one that allows for proper sensing of the presence of this fault. While the discussion so far has addressed the case of light-emitting element drivers that use LEDs as the light-emitting elements constituting the light-emitting unit and LED drivers as the light-emitting element driving devices, any light-emitting element driver for light-emitting elements other than LEDs finds itself in a similar situation.

[0008] This disclosure aims to provide a light-emitting element driving device that helps to sense faults between adjacent terminals.

[0009] Methods for solving problems

[0010] According to one aspect of the present invention, a light-emitting element driving device includes connection terminals corresponding to a plurality of channels, and these connection terminals are configured to be connected to a light-emitting unit having one or more light-emitting elements. The light-emitting element driving device is configured to individually supply a driving current to the light-emitting unit via the connection terminal for each of the channels. The light-emitting element driving device includes a specific fault sensor configured to perform a sensing process for sensing a specific fault during a non-supply period of the driving current to the light-emitting unit. The specific fault is an abnormality in the resistance value between two adjacent connection terminals among the plurality of connection terminals. The specific fault sensor includes: a pull-up circuit configured to individually supply a pull-up current toward the connection terminal for each of the channels; and a comparator configured to compare a voltage at the connection terminal with a predetermined judgment voltage. The sensing process includes: a first comparison process, in which, when the pull-up current is supplied to one of the two connection terminals, the voltage at the other connection terminal is compared with the judgment voltage; and a second comparison process, in which, when the pull-up current is supplied to the other connection terminal, the voltage at the first connection terminal is compared with the judgment voltage. Based on the results of the first and second comparison processes, the specific fault sensor senses the presence or absence of a specific fault at the two connection terminals.

[0011] The effects of the invention

[0012] According to this disclosure, a light-emitting element driving device that helps to sense faults between adjacent terminals can be provided. Attached Figure Description

[0013] Figure 1 This is a general configuration diagram of a light-emitting system according to an embodiment of the present disclosure.

[0014] Figure 2 This is a schematic diagram illustrating multiple channels in a light-emitting system according to an embodiment of the present disclosure.

[0015] Figure 3 This is a schematic diagram showing multiple groups in a light-emitting system according to an embodiment of the present disclosure.

[0016] Figure 4 It is a timing diagram of eight time-division lighting operations that can be performed in a light-emitting system according to an embodiment of the present disclosure.

[0017] Figure 5This is an external perspective view of an LED driver according to an embodiment of the present disclosure.

[0018] Figure 6 This is a plan view of an LED driver according to an embodiment of the present disclosure.

[0019] Figure 7 This is a schematic diagram illustrating the relationship between two adjacent connection terminals according to an embodiment of the present disclosure.

[0020] Figure 8 This is a schematic diagram illustrating the configuration of a specific fault sensor according to an embodiment of the present disclosure.

[0021] Figure 9 This is a schematic diagram illustrating a first inspection period and a second inspection period set in a specific fault sensing process according to an embodiment of the present disclosure.

[0022] Figure 10 This is a schematic diagram showing signal waveforms, etc., during the first and second inspection periods according to Embodiment 1 (Case CS1) which belongs to the present disclosure.

[0023] Figure 11 This is a schematic diagram showing signal waveforms, etc., during the first and second inspection periods according to Embodiment 1 (Case CS2) of this disclosure.

[0024] Figure 12A This is a schematic diagram illustrating the relationship between the terminal voltage and terminal current at two connection terminals according to Embodiment 1, which belongs to the present disclosure.

[0025] Figure 12B This is a schematic diagram illustrating the relationship between the terminal voltage and terminal current at two connection terminals according to Embodiment 1, which belongs to the present disclosure.

[0026] Figure 13 This is a schematic diagram showing four consecutively arranged connection terminals according to Embodiment 2, which belongs to the present disclosure.

[0027] Figure 14 This is a schematic diagram illustrating the control of a switch with four connection terminals arranged in a continuous manner, according to Embodiment 2 of the present disclosure. Detailed Implementation

[0028] Examples of implementing this disclosure will now be described in detail with reference to the accompanying drawings. In the schematic diagrams referred to in the process, the same parts are identified by the same reference numerals, and in principle, overlapping descriptions of the same parts will not be repeated. In this description, for the sake of simplicity, sometimes the symbols and reference numerals that refer to information, signals, physical quantities, elements, parts, etc., corresponding to those symbols and reference numerals are used where the names are omitted or abbreviated. For example, the reference numeral "CH[1]" (see below) will be described later. Figure 1 The connector marked with ) is sometimes referred to as connector CH[1], and at other times abbreviated as connector CH[1], both referring to the same entity.

[0029] First, some terms used to describe embodiments of this disclosure will be defined. "Ground" refers to a reference conductor with a reference potential of 0V (zero volts), or to the potential itself of 0V. The reference conductor is formed of a conductive material such as a metal. The potential of 0V is sometimes referred to as the ground potential. In embodiments of this disclosure, any voltage mentioned without specifying a particular reference is a potential relative to ground.

[0030] "Level" refers to the voltage level, and for any signal or voltage of interest, a "high level" has a higher potential than a "low level". For any signal or voltage of interest, being at a high level means more precisely that its level is high, and being at a low level means more precisely that its level is low. The level of a signal is sometimes called the signal level, and the level of a voltage is sometimes called the voltage level.

[0031] For any transistor configured as a FET (field-effect transistor), which can be a MOSFET, "on state" refers to the state where the drain-source channel of the transistor is turned on, while "off state" refers to the state where the drain-source channel of the transistor is not turned on (turned off). A similar definition applies to any transistor not classified as an FET. Unless otherwise stated, any MOSFET can be understood as a power-up MOSFET. "MOSFET" is an abbreviation for "Metal-Oxide-Semiconductor Field-Effect Transistor".

[0032] Any switch can be configured with one or more FETs (Field-Effect Transistors). When a given switch is in the ON state, the switch terminals are conductive; when a given switch is in the OFF state, the switch terminals are not conductive. In the following description, for any transistor, its ON or OFF state is sometimes simply referred to as ON or OFF, respectively. For any transistor or switch, the period during which it is in the ON state is generally referred to as the ON period, and the period during which it is in the OFF state is generally referred to as the OFF period. Unless otherwise stated, wherever the term “connection” between the multiple parts constituting a circuit (such as between given circuit elements, wiring (conductors), nodes, etc.) is discussed, the term should be understood to mean “electrical connection”.

[0033] Figure 1 This is a general configuration diagram of a light-emitting system SYS according to an embodiment of the present disclosure. The light-emitting system SYS includes an LED driver 1 (as an example of a light-emitting element driving device), an MPU (microprocessor unit) 2 for controlling the LED driver 1, a plurality of light-emitting units driven by the LED driver 1, and an output power supply voltage V. IN 3. Power supply circuit. Power supply voltage V IN It is a positive DC voltage. LED driver 1 has a power supply voltage V that it receives at its location. IN The terminal VINSW, and based on the power supply voltage V IN The luminescent system SYS also includes wiring 6, 7 and 8[1] through 8

[24] , and pull-up resistor R. PU and current setting resistor R ISET As a component, the power supply circuit 3 can be included in the LED driver 1. In this case, terminal FB (described later) is used as an internal terminal of the LED driver 1.

[0034] In the absence of distinction between multiple light-emitting units in a light-emitting system SYS, a light-emitting unit is referred to as a light-emitting unit LL. Each light-emitting unit LL includes one or more LEDs (light-emitting diodes). For example, each light-emitting unit LL is configured as a series circuit of multiple LEDs. Alternatively, each light-emitting unit LL can be configured as a parallel circuit of multiple LEDs, or both a series circuit of multiple LEDs and a parallel circuit of multiple LEDs can be combined to form a light-emitting unit LL. Even a single LED can constitute a light-emitting unit LL. Each light-emitting unit LL has a high-potential terminal and a low-potential terminal, and each LED in the light-emitting unit LL has a positive direction from the high-potential terminal to the low-potential terminal.

[0035] Here, it is assumed that the light-emitting system SYS comprises a total of 24×8 light-emitting units LL as multiple light-emitting units LL, and these 24×8 light-emitting units LL will be identified by the symbols LL[1, 1] to LL[24, 8]. A given light-emitting unit LL among the light-emitting units LL[1, 1] to LL[24, 8] will be called light-emitting unit LL[i, j], where i is any integer satisfying 1 ≤ i ≤ 24, and j is any integer satisfying 1 ≤ j ≤ 8. The light-emitting system SYS and LED driver 1 have channels 1 to 24, such that... Figure 2 As shown, the light-emitting units LL[i, 1] to LL[i, 8] belong to the i-th channel (in other words, correspond to the i-th channel). On the other hand, the light-emitting units LL[1, 1] to LL[24, 8] can be classified into the first to eighth groups, such that... Figure 3 As shown, the light-emitting units LL[1,j] to LL[24,j] belong to the j-th group (in other words, they correspond to the j-th group).

[0036] LED driver 1 has as many connection terminals CH[1] to CH

[24] as the total number of channels. Connection terminal CH[i] belongs to channel i (in other words, corresponds to channel i). Connection terminal CH[i] is the light-emitting unit connection terminal to which the light-emitting units LL[i,1] to LL[i,8] belonging to channel i are connected. When there is no need to distinguish between connection terminals CH[1] to CH

[24] , the connection terminal is sometimes referred to as connection terminal CH.

[0037] The light-emitting system SYS has as many SW[1] to SW[8] as the total number of groups. SW[j] is the switch corresponding to the j-th group. One terminal of all switches SW[1] to SW[8] is connected to the output terminal of the power supply circuit 3 to receive the output voltage of the power supply circuit 3 (i.e., the power supply voltage V). IN The other terminal of switch SW[j] is connected to the high-potential terminals of all light-emitting units LL[1,j] to LL[24,j] in group j. The low-potential terminals of all light-emitting units LL[i,1] to LL[i,8] belonging to channel i are connected to wiring 8[i]. Wiring 8[i] is connected to connection terminal CH[i].

[0038] LED driver 1 includes driver block 10 and control block 20. Driver block 10 includes current drivers DRV[1] to DRV

[24] . Current driver DRV[i] belongs to the i-th channel (in other words, corresponds to the i-th channel). Therefore, driver block 10 includes current drivers, one for each channel. In the absence of need to distinguish between the total of 24 current drivers provided for each channel, the current drivers will sometimes be referred to as current drivers DRV. Current drivers DRV[1] to DRV

[24] are identical in configuration and function. In each channel, current driver DRV[1] includes a constant current circuit; in normal lighting operation, under the control of control block 20, current driver DRV[i] operates such that the drive current I LED [i] flows in the direction from the connection terminal CH[i] to ground. Due to the drive current I LED [1] The current flows to the light-emitting unit LL[1,j] via the connection terminal CH[1], the light-emitting unit LL[1,j] emits light, and due to the driving current I LED [2] The current flows through the connection terminal CH[2] to the light-emitting unit LL[2,j], and the light-emitting unit LL[2,j] emits light. A similar description applies to any other drive current and any other light-emitting unit.

[0039] Control block 20 comprehensively controls the operation of components within LED driver 1. LED driver 1 has terminals GC[1] to GC[8] connected to control terminals of switches SW[1] to SW[8]. Control block 20 can individually turn switches SW[1] to SW[8] on and off via terminals GC[1] to GC[8]. Switches SW[1] to SW[8] can all be implemented using, for example, p-channel MOSFETs (metal-oxide-semiconductor field-effect transistors). In this case, the source of all MOSFETs of switches SW[1] to SW[8] can be supplied with a power supply voltage V. IN The drain of the MOSFET serving as switch SW[j] can be connected to the high-potential terminals of all light-emitting units LL[1,j] to LL[24,j], and the control block 20 can control the gate potential of the MOSFETs serving as switches SW[1] to SW[8] via terminals GC[1] to GC[8]. The control block 20 has the ability to adjust the power supply voltage V of the power supply circuit 3 via terminal FB based on the voltage of the connection terminals CH[1] to CH

[24] during normal lighting operation. IN The function.

[0040] LED driver 1 has a terminal FAILB connected to MPU2 via wiring 6. MPU2 operates based on a power supply voltage VCC, which is a predetermined positive DC voltage. Wiring 6 connecting terminal FAILB and MPU2 is connected via a pull-up resistor R. PUIt is connected to the terminal to which the power supply voltage VCC is applied (the terminal to which the power supply voltage VCC is applied). MPU2 is also connected to terminal COM via communication cable 7, which is the communication terminal of LED driver 1. LED driver 1 and MPU2 can communicate bidirectionally with each other via communication cable 4. Through this bidirectional communication, MPU2 can send desired commands to LED driver 1, and LED driver 1 can send signals to MPU2 in response to received commands. Although Figure 1 Only one terminal COM is shown, but in reality, terminal COM includes multiple external terminals, and correspondingly, communication wiring 7 includes multiple wirings. Any communication method can be used between LED driver 1 and MPU2, and it can be a communication method compliant with SPI (Serial Peripheral Interface).

[0041] LED driver 1 also has terminals GND and I. ISET Terminal GND is connected to ground. Current-setting resistor R ISET It is provided externally to LED driver 1. Current setting resistor R ISET One terminal is connected to terminal I ISET And the current setting resistor R ISET The other terminal is connected to ground. The resistor R is set based on the current. ISET Based on the value and commands from MPU2, control block 20 can independently set the drive current I. LED [1] to I LED

[24] The value.

[0042] The LED driver 1 includes a specific fault sensor 30 as its unique component. The configuration and function of the specific fault sensor 30 will be described later.

[0043] refer to Figure 4 This section describes an eight-part time-division lighting operation as a type of normal lighting operation. In the eight-part time-division lighting operation, unit time periods with a predetermined duration are set. The unit time periods are repeated at a predetermined cycle. Each unit time period is divided into eight parts, and thus the first to eighth division time periods are set. In the first to eighth division time periods, the control block 20 turns on switches SW[1] to SW[8] one by one. Specifically, in the j-th division time period, among switches SW[1] to SW[8], only switch SW[j] remains on, while the other seven switches remain off. Therefore, in the j-th division time period, the power supply voltage V IN The high-potential terminals of the light-emitting units LL[1,j] to Ll[24,j] in the j-th group of the first to eighth groups are supplied only via switch [j], so that only the light-emitting units LL[1,j] to Ll[24,j] can emit light.

[0044] In each of the first to eighth time periods, control block 20 drives the current driver DRV for each channel via PWM. PWM is short for Pulse Width Modulation. In the PWM drive within each time period, the drive current I supplied to each channel is controlled. LED [i] is the time span (i.e., the duration of time). Specifically, the supply drive current I is controlled separately via PWM. LED [1] to I LED

[24] The time span. In this way, in each time period, the corresponding light-emitting unit LL is pulsed and the average brightness of a total of 24×8 light-emitting units LL is individually controlled by this control of the time span.

[0045] For example, when the light-emitting blocks including light-emitting units LL[1, 1] to 11[24, 8] are used as the light source for a display panel (display screen) such as a liquid crystal display panel, unit time periods can be set synchronously with the vertical synchronization signal supplied from the outside to the LED driver 1. In this case, unit time periods are set repeatedly with the period of the vertical synchronization signal. The entire display area of ​​the display panel is divided into multiple subdivisions (e.g., 24 × 8 subdivisions), each subdivision being assigned one or more light-emitting units LL. Then, according to the brightness of the image to be displayed in each display area, the luminous brightness of the corresponding light-emitting unit LL can be adjusted, and thus local dimming (local brightness adjustment) corresponding to the total number of subdivisions can be achieved.

[0046] Although the above description uses eight-part time-division lighting operation as an example of normal lighting operation, normal lighting operation can be one in which the drive current I... LED [i] is any operation that supplies power to any one or more light-emitting units LL[i,j] to make them emit light. For example, the drive current I LED [1] to I LED

[24] can be constantly supplied to perform DC drive during the on period of switch SW[j], or two or more of switches SW[1] to SW[8] can be kept on at the same time.

[0047] Figure 5This is an external perspective view of LED driver 1. The functional blocks (including 10, 20, and 30) constituting LED driver 1 are configured as semiconductor integrated circuits. LED driver 1 is an electronic component constructed by sealing the semiconductor integrated circuits in a package (housing) formed of resin. The package of LED driver 1 has multiple external terminals exposed outside the package. The multiple terminals of LED driver 1 include the aforementioned terminals CH[1] to CH

[24] , GC[1] to CH[8], FB, VINSW, FAILB, COM, ISET, and GND. LED driver 1 also has other external terminals that will not be specifically described.

[0048] Figure 6 This is a schematic plan view of the LED driver 1 as seen on the surface where the external terminals are arranged. In the example used here, the LED driver 1 has a package (housing) called QFN (Quad Flat No Leads). In this case, the LED driver 1 has a package that is substantially rectangular parallelepiped in shape, and has multiple external terminals along each of the four sides SD1 to SD4 of the face constituting the bottom of the package. Figure 6 (This is a plan view seen from the bottom). LED driver 1 can have any package other than QFN, examples include DFN (Dual Flat No Leads) and SOP (Small Outline Package).

[0049] The bottom surface of the package of LED driver 1 has a rectangular shape (which may be a square). The four sides of the rectangular shape include sides SD1 and SD2 opposite to each other and sides SD3 and SD4 opposite to each other. The external terminals of LED driver 1 are all arranged at one of sides SD1 to SD4. Note the connecting terminals CH[1] to CH

[24] , which are arranged at one or more of sides SD1 to SD4 so as to be distributed in one or more of sides SD1 to SD4. For example, connecting terminals CH[1] to CH

[12] may be arranged along side SD1, and connecting terminals CH

[13] to CH

[24] may be arranged along side SD2.

[0050] If two connection terminals CH are arranged along the same side (e.g., SD1) so that they are adjacent to each other, the two connection terminals CH may be short-circuited by solder, condensed moisture, etc. Alternatively, if short-circuited, the two such connection terminals may be connected together across a relatively low-resistance component. Here, such a condition will be referred to as a specific fault. Figure 7 As shown, two connection terminals CH arranged along the same side so that they are adjacent to each other will be referred to as connection terminals CH. A and CH B No other external terminals are arranged at the CH connection terminal. A and CHB Between. Figure 7 In, the symbol "R" EXT The resistor indicated is not a resistor intentionally provided in the SYS lighting system, but rather a resistor connected to the CH terminal external to the LED driver 1. A and CH B An unexpected resistive component exists between them. Resistor R EXT For example, the connection terminal CH that may be unintentionally left on the circuit board when LED driver 1 is mounted on the circuit board (not shown). A and CH B Between, or possibly due to condensation, at the connection terminal CH A and CH B Moisture, or possibly deposits due to soil, may accumulate at the CH connection terminals. A and CH B Foreign matter is generated between them.

[0051] Connecting terminal CH A and CH B The specific fault is at the CH connection terminal. A and CH B The resistance value between (i.e., resistance R) EXT The value of ) is abnormal, and more specifically, the connection terminal CH is abnormal. A and CH B The resistance value between (i.e., resistance R) EXT A fault occurs when the value of the connection terminal CH changes to a predetermined value or lower. In other words, the connection terminal CH... A and CH B The specific fault is in the connection terminal CH. A and CH B The potential difference between them causes a significant current in the connection terminal CH. A and CH B The fault flows between them. The connecting terminal CH... A and CH B The state of short circuits together corresponds to the resistance R. EXT The value is quite low, and therefore it is considered a specific fault.

[0052] Specific fault sensor 30 (see Figure 1 This involves executing a specific fault sensing process, which is a procedure used to sense a specific fault. The specific fault sensor 30 is based on the connection terminal CH. A and CH B The voltage at the connection terminal CH is used to sense the connection. A and CH B The presence or absence of a specific fault at that location. When drive current flows through connection terminal CH... A and CHB When (for example, when the drive current I) LED [1] and I LED [2] When the flow passes through the connecting terminals CH[1] and CH[2], the connecting terminal CH A and CH B The voltage at that point depends on the power supply voltage V. IN And the voltage drop across the corresponding light-emitting unit LL. In multiple light-emitting units LL, the voltage drops across them are usually equal; therefore, when the drive current flows through the connection terminal CH A and CH B At that time, regardless of whether a specific fault exists, the connection terminal CH A and CH B The voltages at these locations are typically equal. This makes it difficult to determine the presence or absence of a specific fault when a drive current is supplied. In this context, the specific fault sensor 30 performs a specific fault sensing process during the non-supply period of the drive current to the light-emitting unit LL. The non-supply period of the drive current to the light-emitting unit LL is when no drive current I is supplied to the light-emitting block including light-emitting units LL[1,8] to LL[24,8]. LED [1] to I LED

[24] During the period (in other words, the driver block 10 does not supply driving current I to the light-emitting block including the light-emitting units LL[1,8] to LL[24,8]), LED [1] to I LED

[24] The time period can be any time period other than the time period during which the normal lighting operation described above is performed. During the non-supply period when the drive current to the light-emitting unit LL is not supplied, switches SW[1] to SW[8] are all turned off, and the high-potential terminal of the light-emitting unit LL is turned off.

[0053] For example, when LED driver 1 is initially supplied with a power supply voltage V that enables it to start. IN Therefore, when LED driver 1 is started, control block 20 first executes a predetermined startup initialization process, and upon completion of its execution, transitions to normal mode, in which control block 20 can perform normal lighting operation. Normal lighting operation is not performed during the execution period of the startup initialization process. During the execution period of the startup initialization process, control block 20 receives a predetermined test command from MPU2, and upon receiving it, causes specific fault sensor 30 to execute a specific fault sensing process. While the specific fault sensing process is being executed, transition to normal mode is not permitted until its completion; transition to normal mode is permitted after the execution of the specific fault sensing process is completed.

[0054] Figure 8The internal configuration of a specific fault sensor 30 is shown. The specific fault sensor 30 includes sensing circuitry for each channel. Where there is no need to distinguish between the multiple sensing circuits corresponding to multiple channels, the sensing circuitry will be referred to as sensing circuitry 31. The sensing circuitry corresponding to the i-th channel will be specifically identified by the symbol "31[i]". The specific fault sensor 30 includes sensing circuitry 31[1] to 31

[24] . The specific fault sensor 30 also includes a determiner 32. Each sensing circuitry 31 includes a control switch, a pull-up constant current circuit, a pull-down constant current circuit, and a comparator. The control switch, pull-up constant current circuit, pull-down constant current circuit, and comparator in sensing circuitry 31[i] will be respectively identified by the symbol "SW". PU [i]”CC PU [i]”CC PD [i]” and “CMP[i]” are used to identify the terminal. The voltage at the connection terminal CH will be referred to as the terminal voltage, and the terminal voltage at the connection terminal CH[i] will be specifically indicated by the symbol “V”. CH The comparator's output signal will be referred to as the comparison result signal, and the output signal of comparator CMP[i] will be specifically identified by the symbol "CMP". OUT [i]” identifier.

[0055] Sensing circuits 31[1] to 31

[24] are identical in configuration. The interconnection between sensing circuit 31 and the corresponding connection terminal CH is identical in channels 1 to 24. Therefore, focusing on channel i (1≤i≤24), a description of the configuration and operation of sensing circuit 31[i] and the interconnection between sensing circuit 31[i] and connection terminal CH[i] will be given.

[0056] In the sensing circuit 31[i], the control switch SW PU One terminal of [i] is connected to a predetermined internal voltage V. REG The applied terminal (i.e., the internal voltage V) REG (Applied to the terminal), and control switch SW PU The other terminal of [i] is connected to the pull-up constant current circuit CC. PU [i] is connected to the connection terminal CH[i]. The connection terminal CH[i] is connected via a pull-down constant current circuit CC. PD [i] is connected to ground and also to the non-inverting terminal of comparator CMP[i]. The inverting input terminal of comparator CMP[i] is supplied with a predetermined judgment voltage V. TH Internal voltage V REG And determine voltage V TH It is based on the power supply voltage V in the internal power supply circuit (not shown) within the LED driver 1. IN The generated positive DC voltage. Internal voltage VREG (For example, 3.3V) is higher than the judgment voltage V. TH (e.g., 0.15V).

[0057] Control switch SW PU [i] and constant current circuit CC PU [i] forms a pull-up circuit, which can supply pull-up current I toward the connection terminal CH[i]. PU Specifically, in the sensing circuit 31[i], only when the control switch SW is activated... PU [i] When connected, the constant current circuit CC is pulled up. PU [i] only receives internal voltage V REG And based on the internal voltage V REG Generate pull-up current I PU To obtain from the internal voltage V REG The application terminal supplies pull-up current I to the connection terminal CH[i]. PU (i.e., the positive charge generated by the pull-up current). In the control switch SW... PU During the conduction period of [i], the constant current circuit CC PU [i] The operation is to supply a predetermined current value I to the connection terminal CH[i]. PU_VAL Pull-up current I PU However, it does not have the function of transferring terminal voltage V CH [i] Rise to a level higher than the internal voltage V REG The ability. Therefore, in the control switch SW PU During the conduction period of [i], until the terminal voltage V CH [i] Reaching internal voltage V REG Pull-up current I PU The value is equal to the current value I PU_VAL However, at the terminal voltage V CH [i] has essentially reached the internal voltage V REG In this case, the pull-up current I PU The value is less than the current value I PU_VAL In the control switch SW PU During the cutoff period of [i], the constant current circuit CC PU [i] No pull-up current I is generated PU And there is no current in the constant current circuit CC. PU The current flows between [i] and the connecting terminal CH[i].

[0058] In sensing circuit 31[i], the pull-down constant current circuit CC PD [i] Continuously draws a constant current from the connection terminal CH[i] (i.e., from the pull-up constant current circuit CC). PUThe connection node between [i] and the connection terminal CH[i] draws pull-down current I to ground. PD (by pull-down current I) PD (Generated positive charge). Constant current circuit CC PD [i] The operation is to draw a predetermined current value I from the connection terminal CH[i] toward ground. PD_VAL pull-down current I PD However, it does not have the ability to make the terminal voltage V CH [i] The ability to drop below 0V. Therefore, if the terminal voltage V CH [i] If it is higher than 0V, then the pull-down current I PD The value is equal to the current value I PD_VAL However, at the terminal voltage V CH [i] With the voltage essentially dropping to 0V, the pull-down current I PD The value is less than the current value I PD_VAL (And can be zero.)

[0059] As the pull-down current I PD The set value of the current value I PD_VAL Less than the pull-up current I PU The set value of the current value I PU_VAL For example, the current value I PU_VAL It is 3mA (milliamperes), and the current value I PD_VAL The pull-down current is 20 μA (microamps). PD It has the ability to supply pull-up current I PU This is to discharge the positive charge stored at the connection terminal CH[i]. Therefore, the pull-down current I... PD This can be referred to as the discharge current, and is the CC of the pull-down constant current circuit. PD [i] can be referred to as a constant current discharge circuit CC PD [i].

[0060] In the sensing circuit 31[i], the comparator CMP[i] converts the terminal voltage V CH [i] and the predetermined judgment voltage V TH A comparison is performed to output a comparison result signal CMP indicating the comparison result. OUT [i]. Comparison result signal CMP OUT [i] treats its signal level as a binary signal, either high or low. If the terminal voltage V CH [i] Higher than the judgment voltage V TH Then the comparator CMP[i] will compare the result signal CMP. OUT [i] Remains at a high level, and if the terminal voltage V CH [i] is lower than the judgment voltage V THThen the comparator CMP[i] will compare the result signal CMP. OUT [i] Remains at a low level. If the terminal voltage V CH [i] is exactly equal to the voltage V. TH The comparison result signal CMP OUT [i] is at a high or low level.

[0061] The determiner 32 is supplied with the comparison result signal CMP OUT [1] to CMP OUT

[24] . Based on the comparison result signal CMP OUT [1] to CMP OUT

[24] , Determiner 32 checks the connection terminals CH[1] to CH

[24] which are in relation to the connection terminal CH. A and CH B (see Figure 7 The presence or absence of a specific fault between two given connection terminals CH in a similar relationship.

[0062] Now, through various embodiments, some specific examples of the configuration and operation of a particular fault sensor 30, LED driver 1, or light-emitting system SYS, along with the associated applied and modified techniques, will be presented. Unless otherwise stated or unless inconsistent, any description given above in conjunction with the embodiments applies to the embodiments presented below. For any description of embodiments that contradicts the above description, the description given in conjunction with the embodiments shall prevail. Unless inconsistent, any description given in conjunction with any embodiment presented below applies to any other embodiment (i.e., any two or more embodiments may be implemented in combination).

[0063] <<Example 1>>

[0064] Example 1 will be described. Example 1 assumes... Figure 7 CH in the connection terminal A and CH B This relates to methods for sensing the presence or absence of specific faults at connection terminals CH[1] and CH[2]. Therefore, in conjunction with the resistor R mentioned in Embodiment 1... EXT The term "resistive component" refers to the resistive component between terminals CH[1] and CH[2], and "specific fault" refers to a specific fault at terminals CH[1] and CH[2] in conjunction with the specific fault mentioned in Embodiment 1.

[0065] During a specific fault sensing process, the specific fault sensor 30 sets a first inspection period and a second inspection period. The first and second inspection periods are two periods that do not overlap with each other. Although the first and second inspection periods can occur in any order, it is assumed here that they are arranged such that the first inspection period is followed by the second inspection period (this also applies to any other embodiments described later).

[0066] As described above, a specific fault sensing process is performed during the non-supply period of the drive current to the light-emitting unit LL, and therefore, no drive current is supplied to the light-emitting unit LL during the first and second check periods (i.e., the light-emitting unit LL is in a non-light-emitting state). Figure 9 As shown, during the first inspection period, the specific fault sensor 30 maintains the control switch SW. PU [1] Turn on and hold the control switch SW PU [2] Shutdown. Therefore, during the first check period, the pull-up circuit of the first channel (i.e., SW) is turned off. PU [1], CC PU [1]) Supply pull-up current I toward the connection terminal CH[1] PU And the pull-up circuit of the second channel (i.e., SW) PU [2], CC PU [2]) Pause the supply of pull-up current I toward the connection terminal CH[2] PU In contrast, during the second inspection period, the specific fault sensor 30 kept the control switch SW active. PU [2] Turn on and hold the control switch SW PU [1] Shutdown. Therefore, during the second check period, the pull-up circuit of the second channel (i.e., SW) is turned off. PU [2], CC PU [2]) Supply pull-up current I toward the connection terminal CH[2] PU And the pull-up circuit of the first channel (i.e., SW) PU [1], CC PU [1]) Pause the supply of pull-up current I toward the connection terminal CH[1] PU Incidentally, the control switch SW is used before the first inspection period and after the second inspection period. PU [1] and SW PU [2] Keep it off.

[0067] The first inspection period begins at time t1 and ends at time t3. The second inspection period begins at time t3 and ends at time t5. Although the end time of the first inspection period and the start time of the second inspection period coincide at time t3, there may be a time lag between the end time of the first inspection period and the start time of the second inspection period. Within the first inspection period, a predetermined time Δt elapses from time t1. A The time point will be referred to as inspection time point t2. Inspection time point t2 occurs earlier than time point t3. During the second inspection period, a predetermined time Δt elapses from time point t3. B The time point will be referred to as the inspection time point t4. Inspection time point t4 occurs earlier than time point t5. The scheduled time Δt A and Δt B They are equal, but they can be different.

[0068] Figure 10 The state of the control switch and the waveform of the terminal voltage are shown in case CS1. In case CS1, the connecting terminals CH[1] and CH[2] are not short-circuited together, and the resistance R between the connecting terminals CH[1] and CH[2] is... EXT High enough.

[0069] In case CS1, when the first check period begins, along with the constant current from the CC circuit... PU [1] pull-up current I PU Terminal voltage V CH [1] Basically rises sharply from its initial voltage (e.g., 0V) to its internal voltage V REG Following this, during the period from time point t2 to time point t3, the terminal voltage V... CH [1] Basically maintained at internal voltage V REG And therefore, the comparison result signal CMP OUT [1] Remains at a high level. On the other hand, in case CS1, during the first check period, the constant current circuit CC... PD [2] Function, terminal voltage V CH [2] It remains at 0V, and therefore the comparison result signal CMP is obtained. OUT [2] Always keep at a low level.

[0070] In case CS1, when the second check period begins, along with the constant current circuit CC... PU [2] Pull-up current I PU Terminal voltage V CH [2] Basically rises sharply from its initial voltage (e.g., 0V) to its internal voltage V REGFollowing this, during the period from time point t4 to time point t5, the terminal voltage V... CH [2] Basically maintained at internal voltage V REG And therefore, the comparison result signal CMP OUT [2] Remains at a high level. On the other hand, in case CS1, during the second check period, the constant current circuit CC... PD [1] Function, terminal voltage V CH [1] It remains at 0V, and therefore the comparison result signal CMP is obtained. OUT [1] Always keep at a low level.

[0071] Figure 11 The state of the control switch and the waveform of the terminal voltage are shown in case CS2. In case CS2, terminals CH[1] and CH[2] are short-circuited together, and the resistance R between terminals CH[1] and CH[2] is... EXT Low enough.

[0072] In case CS2, when the first check period begins, the constant current circuit CC is used. PU [1] pull-up current I PU Terminal voltage V CH [1] It rises sharply from its initial voltage (e.g., 0V) to its internal voltage V REG Following this, during the period from time point t2 to time point t3, the terminal voltage V... CH [1] Roughly maintained at internal voltage V REG And therefore, the comparison result signal CMP OUT [1] Remains at a high level. Furthermore, in case CS2, during the first check period, the constant current circuit CC... PU [1] pull-up current I PU Via connection terminal CH[1] and resistor R EXT The current flows to the connection terminal CH[2], and therefore the terminal voltage V CH [2] is the ratio of terminal voltage V CH [1] Low resistance R EXT The voltage drop across the terminals. Figure 11 In the middle, the resistance R EXT It is assumed to be low enough, and therefore during the first inspection period, the terminal voltage V CH [2] Roughly equal to the internal voltage V REG Therefore, in case CS2, during the period from check time point t2 to time point t3, the terminal voltage V... CH [1] Similarly, the terminal voltage V CH [2] Roughly maintained at internal voltage VREG And therefore, the comparison result signal CMP OUT [2] Keep it at a high level.

[0073] In case CS2, at the start time t3 of the second inspection period, the terminal voltage V... CH [2] Roughly equal to the internal voltage V REG Furthermore, after this, the constant current circuit CC is used. PU [2] Pull-up current I PU Terminal voltage V CH [2] Maintain internal voltage V REG Therefore, during the entire second inspection period, the comparison result signal CMP is used. OUT [2] Remains at a high level. Furthermore, in case CS2, during the second check period, the constant current circuit CC... PU [2] Pull-up current I PU Via connection terminal CH[2] and resistor R EXT The current flows to the connection terminal CH[1], and therefore the terminal voltage V CH [1] is the voltage V of the terminal. CH [2] Low resistance R EXT The voltage drop across the terminals. Figure 11 In the middle, the resistance R EXT It is assumed to be low enough, and therefore during the second inspection period, the terminal voltage V CH [1] Roughly equal to the internal voltage V REG Therefore, in case CS2, during the entire second inspection period, the terminal voltage V... CH [2] Similarly, the terminal voltage V CH [1] Roughly maintained at internal voltage V REG And therefore, the comparison result signal CMP OUT [1] Keep it at a high level.

[0074] Determiner 32 receives the comparison result signal CMP at the inspection time point t2. OUT [2] Comparison result signal CMP at inspection time point t4 OUT [1] as the first and second evaluation signals. If both the first and second evaluation signals are high, the determiner 32 determines that a specific fault exists at the connection terminals CH[1] and CH[2]; otherwise, the determiner 32 determines that there is no specific fault at the terminals CH[1] and CH[2] (in other words, it is uncertain whether a specific fault exists). Therefore, in Figure 10 In case CS1, it is determined that there is no specific fault at the connection terminals CH[1] and CH[2], and Figure 11In case CS2, a specific fault is determined to exist at the connection terminals CH[1] and CH[2].

[0075] The specific fault sensing process can be understood as including a first comparison process and a second comparison process. Note the two adjacent connection terminals CH[1] and CH[2]. The first comparison process is to use comparator CMP[2] to check the terminal voltage V at time point t2. CH [2] and the judgment voltage V TH The comparison process, and the first inspection period includes the execution period of the first comparison process (i.e., the first comparison process is performed during the first inspection period). On the other hand, the second comparison process is to compare the terminal voltage V at the inspection time point t4 using comparator CMP[1]. CH [1] and the judgment voltage V TH The comparison process is performed, and the second inspection period includes the execution period of the second comparison process (i.e., the second comparison process is performed during the second inspection period). Based on the results of the first and second comparison processes (i.e., based on the first and second evaluation signals), the specific fault sensor 30 (determiner 32) senses the presence or absence of a specific fault at the connection terminals CH[1] and CH[2].

[0076] Specifically, if during the first comparison process, a pull-up current I is supplied toward a connection terminal (here, CH[1]) PU In the case where the voltage at the other connection terminal (here, CH[2]) is higher than the judgment voltage V TH Furthermore, during the second comparison process, a pull-up current I is supplied toward another connection terminal (here, CH[2]). PU In the case where the voltage at one of the connection terminals (here, CH[1]) is higher than the judgment voltage, the specific fault sensor 30 (determiner 32) senses the presence of a specific fault at the two connection terminals (here, CH[1] and CH[2]).

[0077] Based on resistance R EXT The value of the fault is used to determine whether a particular fault exists or not. Figure 12A The terminal voltage V during the first inspection period is shown. CH [1] and terminal current I CH [1] and the terminal voltage V CH [2] with terminal current I CH [2] The relationship between them. Figure 12B The terminal voltage V during the second inspection period is shown. CH [2] with terminal current I CH [2] and the terminal voltage V CH [1] and terminal current I CHThe relationship between [1]. Terminal current I CH [i] is the current flowing through the connection terminal CH[i]. Here, during the first check period, the terminal current I... CH [1] is assumed to be positive when flowing from inside the LED driver 1 through the connection terminal CH[1] to the outside of the LED driver 1, and the terminal current I CH [2] is assumed to be positive when flowing from outside the LED driver 1 through the connection terminal CH[2] into the LED driver 1. In contrast, during the second check period, the terminal current I CH [2] is assumed to be positive when flowing from inside LED driver 1 through connection terminal CH[2] to outside LED driver 1, and terminal current I CH [1] is assumed to be positive when flowing from outside the LED driver 1 through the connection terminal CH[1] into the LED driver 1.

[0078] During the first inspection period (see Figure 12A In the terminal current I, CH [1] and I CH [2] The point where the voltages are exactly equal is the operating point. The terminal voltage V at the operating point is... CH [2] With resistance R EXT The value of decreases as resistance R increases, and decreases as resistance R increases. EXT The value of R decreases and increases. EXT The value is so low that the terminal voltage V at the operating point CH [2] Higher than the judgment voltage V TH The comparison result signal CMP in the first inspection period OUT [2] is at a high level. A similar understanding applies to the second check period. If resistor R EXT If the value of resistor R is higher than the predetermined value, then the specific fault is determined to be absent; if the value of resistor R is higher than the predetermined value, then the specific fault is determined to be absent. EXT If the value is lower than a predetermined value, then the existence of a specific fault is determined. Here, the predetermined value depends on the judgment voltage V. TH .

[0079] According to Example 1, the presence or absence of a specific fault at the two connection terminals CH can be accurately sensed.

[0080] <<Example 2>>

[0081] Example 2 will be described. Although only two connection terminals CH are considered in Example 1, any number of consecutively arranged connection terminals CH can be sensed for the presence or absence of a specific fault. Three or more consecutively arranged connection terminals CH include multiple combinations of two mutually adjacent connection terminals CH; for each combination, the two connection terminals CH can be considered as connection terminals CH.A and CH B Furthermore, for each combination, the presence or absence of a specific fault can be sensed by combining the method described in Example 1.

[0082] For example, such as Figure 13 As shown, assume that along edges SD1 to SD4 (see...) Figure 6 At one of the edges of the circuit, the connecting terminals CH[1] to CH[4] are arranged in succession. The connecting terminals CH[1], CH[2], CH[3] and CH[4] are arranged sequentially along this edge. No other terminals are arranged between connecting terminals CH[1] and CH[2], between connecting terminals CH[2] and CH[3], or between connecting terminals CH[3] and CH[4]. That is, connecting terminals CH[1] and CH[2] are adjacent to each other, connecting terminals CH[2] and CH[3] are adjacent to each other, and connecting terminals CH[3] and CH[4] are adjacent to each other.

[0083] As described in conjunction with Embodiment 1, during a specific fault sensing process, the specific fault sensor 30 is configured with first and second inspection periods. The first and second inspection periods, and time points t1 to t5, are consistent with those described in conjunction with Embodiment 1 (see [link to Embodiment 1]). Figure 9 The same relationship described.

[0084] like Figure 14 As shown, during the first inspection period, the specific fault sensor 30 maintains the control switch SW. PU [1] and SW PU [3] Switch SW for connection and control PU [2] and SW PU [4] Shutdown. Therefore, during the first check period, the pull-up circuit (SW) of the first channel is turned off. PU [1], CC PU [1]) and the pull-up circuit of the third channel (SW) PU [3], CC PU [3]) Supply pull-up current I to the connection terminals CH[1] and CH[3] respectively. PU And the pull-up circuit of the second channel (SW) PU [2], CC PU [2]) and the pull-up circuit of the fourth channel (SW) PU [4], CC PU [4]) Stop supplying pull-up current I to the connection terminals CH[2] and CH[4] respectively. PU In contrast, during the second inspection period, the specific fault sensor 30 kept the control switch SW active. PU [2] and SW PU [4] Switch SW is connected and controlled PU [1] and SWPU [3] Shutdown. Therefore, during the second check period, the pull-up circuit (SW) of the second channel is turned off. PU [2], CC PU [2]) and the pull-up circuit of the fourth channel (SW) PU [4], CC PU [4]) Supply pull-up current I to the connection terminals CH[2] and CH[4] respectively. PU And the pull-up circuit of the first channel (SW) PU [1], CC PU [1]) and the pull-up circuit of the third channel (SW) PU [3], CC PU [3]) Stop supplying pull-up current I to the connection terminals CH[1] and CH[3] respectively. PU Incidentally, the control switch SW is used before the first inspection period and after the second inspection period. PU [1] to SW PU [4] Keep it off.

[0085] Determiner 32 senses the presence or absence of a specific fault for each combination of two adjacent connection terminals CH. Specifically, Determiner 32 examines the comparison result signal CMP at time point t2. OUT [2] Comparison result signal CMP at inspection time point t4 OUT [1] As two evaluation signals, if both evaluation signals are high, it is determined that a specific fault exists at the connection terminals CH[1] and CH[2]; otherwise, the determiner 32 determines that there is no specific fault at the connection terminals CH[1] and CH[2] (in other words, it is uncertain whether a specific fault exists). Similarly, the determiner 32 will check the comparison result signal CMP at time point t2. OUT [2] Comparison result signal CMP at inspection time point t4 OUT [3] As two evaluation signals, if both evaluation signals are high, it is determined that a specific fault exists at the connection terminals CH[2] and CH[3]; otherwise, the determiner 32 determines that there is no specific fault at the connection terminals CH[2] and CH[3] (in other words, it is uncertain whether a specific fault exists). In addition, the determiner 32 will check the comparison result signal CMP at time point t2. OUT [4] Comparison result signal CMP at inspection time point t4 OUT [3] As two evaluation signals, if both evaluation signals are high, it is determined that a specific fault exists at the connection terminals CH[3] and CH[4]; otherwise, the determiner 32 determines that there is no specific fault at the connection terminals CH[3] and CH[4] (in other words, it is not certain that a specific fault exists).

[0086] The specific fault sensing process can be understood as including a first comparison process and a second comparison process. Note the connection of terminals CH[1] to CH[4]. The first comparison process corresponds to using comparators CMP[2] and CMP[4] to check the terminal voltage V at time point t2. CH [2] and V CH [4] All are related to the judgment voltage V TH The comparison process, and the first check period includes the execution period of the first comparison process (i.e., the first comparison process is performed during the first check period). In contrast, the second comparison process corresponds to comparing the terminal voltage V at check time point t4 using comparators CMP[1] and CMP[3]. CH [1] and V CH [3] All are related to the judgment voltage V TH The comparison process, and the second inspection period includes the execution period of the second comparison process (i.e., the second comparison process is performed during the second inspection period). Based on the results of the first and second comparison processes, the specific fault sensor 30 (determiner 32) individually senses the presence or absence of a specific fault at connection terminals CH[1] and CH[2], the presence or absence of a specific fault at connection terminals CH[2] and CH[3], and the presence or absence of a specific fault at connection terminals CH[3] and CH[4].

[0087] Specifically, assuming i is a variable taking the value 1, 2, or 3, if a pull-up current I is supplied towards the connection terminal CH[i] PU In the case where the voltage at terminal CH[i+1] is higher than the judgment voltage V, TH Furthermore, a pull-up current I is supplied toward the connection terminal CH[i+1]. PU In the case where the voltage at terminal CH[i] is higher than the judgment voltage V, TH Then, the specific fault sensor 30 (determiner 32) senses the presence of a specific fault at the connection terminals CH[i] and CH[i+1].

[0088] Although here, for the sake of specificity, note the four connection terminals CH[1] to CH[4], a similar description applies to five or more connection terminals CH along edges SD1 to SD4 (see [link to documentation]). Figure 6The case of any consecutive arrangement of the terminals CH[1], CH[2], CH[3], ..., CH[2×k] along one edge in that order (where k is an integer of three or greater), such that for any natural number p, the terminals CH[p] and CH[p+1] are adjacent to each other. In this case, the first, third, ..., and (2×k-1)th channels are classified as odd channels, and the second, fourth, ..., and (2×k)th channels are classified as even channels.

[0089] During the first inspection period, the specific fault sensor 30 maintains the control switch SW of the odd-numbered channels. PU [1] SW PU [3], ... and SW PU [2×k-1] On and even-numbered channel control switch SW PU [2] SW PU [4], ... and SW PU [2×k] is turned off. Therefore, during the first check period, the pull-up circuit of the odd-numbered channels supplies pull-up current I to the connection terminals (CH[1], CH[3], ... and CH[2×k-1]) of the odd-numbered channels. PU Furthermore, the pull-up circuits of even-numbered channels suspend supplying pull-up current I to the connection terminals (CH[2], CH[4], ... and CH[2×k]) of even-numbered channels. PU In contrast, during the second inspection period, the specific fault sensor 30 maintains the control switch SW on an even-numbered channel. PU [2] SW PU [4], ... and SW PU [2×k] On and Odd-numbered channel control switch SW PU [1] SW PU [3], ... and SW PU [2×k-1] is turned off. Therefore, during the second check period, the pull-up circuit of the even-numbered channels supplies pull-up current I to the connection terminals (CH[2], CH[4], ... and CH[2×k]) of the even-numbered channels. PU Furthermore, the pull-up circuits of the odd-numbered channels suspend supplying pull-up current I to the connection terminals (CH[1], CH[3], ... and CH[2×k-1]) of the odd-numbered channels. PU Incidentally, the control switch SW is used before the first inspection period and after the second inspection period. PU [1] to SW PU

[24] All remain off.

[0090] Determiner 32 senses the presence or absence of a specific fault for each combination of two adjacent connection terminals CH. That is, individually for each integer q satisfying 1≤q≤k, determiner 32 will examine the comparison result signal CMP at time point t2. OUT The comparison result signal CMP between [2×q] and the inspection time point t4. OUT [2×q-1] serves as two evaluation signals, and if both evaluation signals are high, a specific fault is determined to exist at the connection terminals CH[2×q-1] and CH[2×q]; otherwise, the determiner 32 determines that no specific fault exists at the connection terminals CH[2×q-1] and CH[2×q] (in other words, it is uncertain whether a specific fault exists). Similarly, for each integer q that satisfies 1≤q≤k-1, the determiner 32 will check the comparison result signal CMP at time point t2. OUT The comparison result signal CMP between [2×q] and the inspection time point t4. OUT [2×q+1] serves as two evaluation signals, and if both evaluation signals are high, it is determined that a specific fault exists at the connection terminals CH[2×q] and CH[2×q+1]; otherwise, the determiner 32 determines that there is no specific fault at the connection terminals CH[2×q] and CH[2×q+1] (in other words, it is uncertain whether a specific fault exists).

[0091] According to Embodiment 2, the presence or absence of a specific fault can be sensed individually among any mutually adjacent connection terminals of a plurality of connection terminals CH including a plurality of connection terminals CH.

[0092] <<Example 3>>

[0093] Example 3 will be described. If a specific fault is sensed with respect to a given combination of two connection terminals CH, control block 20 stores fault presence data indicating the presence of the fault and fault location data indicating where the fault is located in a register (not shown) provided therein. Furthermore, if the presence of any fault (including a specific fault) is sensed in LED driver 1, control block 20 changes the normally high signal level on wiring 6 to a low level, thereby notifying MPU2 of the fault's presence. Upon detecting a low signal level on wiring 6, MPU2 can send an error read command to LED driver 1, requesting the transmission of data stored in the aforementioned register, if necessary. Upon receiving the error read command, LED driver 1 sends data including fault presence data and fault location data to MPU 2, and MPU 2 can then identify what the fault presence data and fault location data indicate based on the received data.

[0094] Based on the received data, including fault presence data and fault location data, the MPU2 can perform a predetermined fault handling procedure. For example, in the case where the light-emitting blocks including light-emitting units LL[1,1] to LL[24,8] are used as the light source in a display panel such as a liquid crystal display panel, the entire display area of ​​the display panel is divided into multiple partitioned areas (e.g., 24×8 partitioned areas), and each partitioned area is assigned one or more light-emitting units LL, if the presence of a specific fault is sensed at the connection terminals CH[1] and CH[2], the image to be displayed on the display panel is displayed in the normal display area. Here, the normal display area is the display area excluding the partitioned areas of light-emitting units LL[1,1] to LL[1,8] and LL[2,1] to LL[2,8] assigned to the first and second channels.

[0095] <<Example 4>>

[0096] Example 4 will be described. Example 4 relates to application techniques and modification techniques that are related to the content already described above.

[0097] The light-emitting blocks, including light-emitting units LL[1, 1] to LL[24, 8], can be used as light sources in various devices, such as in a display panel as described above. The light-emitting system SYS can be specifically included in a vehicle, such as an automobile. In this case, the light-emitting blocks as described above can be used as light sources in cluster panels for displaying vehicle speed, engine speed, remaining fuel, etc., in display panels for automobile navigation, in head-up displays, or in central information displays.

[0098] Although the above configuration contains 24 channels and 8 groups (see...) Figures 1 to 3 However, any number (two or more) channels and any number (two or more) groups can exist.

[0099] There can be only one group. Specifically, although in the above configuration each connection terminal CH is connected in parallel to the same number of light-emitting units LL as the group, it is also possible for each connection terminal CH to have a single light-emitting unit LL connected to it. For example, only a total of 24 light-emitting units LL[1,1], LL[2,2], LL[3,3], ... and LL[24,24] from LL[1,1] to LL[24,8] can be provided in the light-emitting system SYS. In this case, local dimming (local brightness adjustment) corresponding to up to 24 divided areas can be achieved.

[0100] According to this disclosure, the light-emitting unit LL may include one or more light-emitting elements that emit light when supplied with current. The light-emitting diode (LED) serving as the light-emitting element may be any type of LED and may be an organic LED that produces organic electroluminescence. The light-emitting element may be a light-emitting element not classified as an LED and may be, for example, a laser diode.

[0101] LED driver 1 is an example of a light-emitting element driving device for driving light-emitting units LL, and the above embodiments relate to examples in which the technology according to this disclosure (including technology for sensing specific faults) is applied to the light-emitting element driving device. However, this does not mean that the technology according to this disclosure can be excluded from being applied to any other device. Specifically, for example, the technology according to this disclosure for sensing specific faults can be used to sense the presence or absence of a specific fault between any two mutually adjacent terminals provided in any device.

[0102] For any signal or voltage, the relationship between its high and low levels can be reversed, unless it is inconsistent with what is disclosed herein.

[0103] The embodiments of this disclosure may be modified in various ways as needed without departing from the scope of the technical concept defined in the appended claims. The embodiments described herein are merely examples of how the invention can be implemented, and the meaning of any terms used to describe the invention and its constituent elements is not limited to the meaning mentioned in connection with the embodiments. The specific values ​​mentioned in the above description are merely illustrative and are not necessarily to be modified to different values.

[0104] <<Notes>>

[0105] The following is a study of the technical concepts implemented in the above embodiments.

[0106] According to one aspect of this disclosure, a light-emitting element driving device includes connection terminals corresponding to a plurality of channels, and these connection terminals are configured to connect to a light-emitting unit having one or more light-emitting elements. The light-emitting element driving device is configured to individually supply a drive current to the light-emitting unit via the connection terminal for each of the channels. The light-emitting element driving device includes a specific fault sensor configured to perform a sensing process for sensing a specific fault during a non-supply period of the drive current to the light-emitting unit. The specific fault is an abnormality in the resistance value between two adjacent connection terminals among the plurality of connection terminals. The specific fault sensor includes: a pull-up circuit configured to individually supply a pull-up current toward the connection terminal for each of the channels; and a comparator configured to compare a voltage at the connection terminal with a predetermined judgment voltage. The sensing process includes: a first comparison process, in which, when the pull-up current is supplied to one of the two connection terminals, the voltage at the other connection terminal is compared with the judgment voltage; and a second comparison process, in which, when the pull-up current is supplied to the other connection terminal, the voltage at the first connection terminal is compared with the judgment voltage. Based on the results of the first and second comparison processes, the specific fault sensor senses the presence or absence of a specific fault at the two connection terminals. (First Configuration)

[0107] In the light-emitting element driving device of the first configuration described above, preferably, if during the first comparison process, when the pull-up current is supplied to one of the two connection terminals, the voltage at the other of the two connection terminals is higher than the judgment voltage, and furthermore, during the second comparison process, when the pull-up current is supplied to the other of the two connection terminals, the voltage at the other of the two connection terminals is higher than the judgment voltage, then the specific fault sensor senses the presence of a specific fault at the two connection terminals. (Second Configuration)

[0108] In the light-emitting element driving device of the first or second configuration described above, preferably, one of the two connection terminals and the other connection terminal are connection terminals of the first channel and the second channel, respectively. Preferably, during the execution period of the first comparison process, the pull-up circuit of the first channel supplies the pull-up current to one of the two connection terminals, and the pull-up circuit of the second channel suspends supplying the pull-up current to the other of the two connection terminals; during the execution period of the second comparison process, the pull-up circuit of the second channel supplies the pull-up current to the other of the two connection terminals, and the pull-up circuit of the first channel suspends supplying the pull-up current to the one of the two connection terminals. (Third Configuration)

[0109] In the light-emitting element driving device of the first configuration described above, preferably, the plurality of connection terminals include first to fourth connection terminals. Preferably, the first to fourth connection terminals are arranged consecutively in this order. Preferably, in the first comparison process, the specific fault sensor compares the voltage at the second and fourth connection terminals with the judgment voltage while supplying the pull-up current to each of the first and third connection terminals, and in the second comparison process, the specific fault sensor compares the voltage at the first and third connection terminals with the judgment voltage while supplying the pull-up current to each of the second and fourth connection terminals. Preferably, based on the results of the first and second comparison processes, the specific fault sensor individually senses the presence or absence of a specific fault at the first and second connection terminals, the presence or absence of a specific fault at the second and third connection terminals, and the presence or absence of a specific fault at the third and fourth connection terminals. (Fourth Configuration)

[0110] In the above-described fourth configuration of the light-emitting element driving device, preferably, if the voltage at the (i+1)th connection terminal is higher than the judgment voltage when the pull-up current is supplied to the i-th connection terminal, and furthermore, if the voltage at the i-th connection terminal is higher than the judgment voltage when the pull-up current is supplied to the (i+1)-th connection terminal, then the specific fault sensor senses the presence of a specific fault at the i-th and (i+1)-th connection terminals, where i is 1, 2, or 3. (Fifth Configuration)

[0111] In the above-described fourth or fifth configuration of the light-emitting element driving device, preferably, the first to fourth connection terminals are respectively the connection terminals of the first to fourth channels. Preferably, during the execution period of the first comparison process, the pull-up circuits of the first and third channels supply the pull-up current toward the first and third connection terminals, and the pull-up circuits of the second and fourth channels suspend supplying the pull-up current toward the second and fourth connection terminals; during the execution period of the second comparison process, the pull-up circuits of the second and fourth channels supply the pull-up current toward the second and fourth connection terminals, and the pull-up circuits of the first and third channels suspend supplying the pull-up current toward the first and third connection terminals. (Sixth Configuration)

[0112] In any of the first to sixth configurations of the above-described light-emitting element driving device, preferably, for each of the channels, the specific fault sensor includes a pull-down circuit configured to draw a pull-down current from a corresponding one of the connection terminals, and the pull-down current is set to be less than the magnitude of the pull-up current. (Seventh Configuration)

[0113] List of reference numerals

[0114] SYS lighting system

[0115] 1 LED driver

[0116] 2MPU

[0117] 3 Power supply circuit

[0118] 10 Driver Blocks

[0119] 20 Control Blocks

[0120] 30 Specific Fault Sensors

[0121] LL[1,1] to LL[24,8] light-emitting units

[0122] CH[1] to CH

[24] connection terminals

[0123] I LED [1] to I LED

[24] Drive current

[0124] 31[1] to 31

[24] Sensing circuits

[0125] 32 Determiner

[0126] I PU Pull-up current

[0127] I PD Pull-down current (discharge current)

Claims

1. A light-emitting element driving device, comprising connection terminals corresponding to a plurality of channels, the connection terminals being configured to connect to a light-emitting unit having one or more light-emitting elements, the light-emitting element driving device being configured to supply a driving current to the light-emitting unit individually via the connection terminals for each of the plurality of channels. in The light-emitting element driving device includes a specific fault sensor configured to perform a sensing process for sensing a specific fault during the off-supply period of the driving current to the light-emitting unit. The specific fault is an abnormality in the resistance value between two adjacent connection terminals among a plurality of connection terminals. The specific fault sensor includes the following pull-up circuit and comparator: A pull-up circuit, configured to individually supply pull-up current toward the connection terminal for each of the plurality of channels; as well as A comparator configured to compare the voltage at the connection terminal with a predetermined judgment voltage. The sensing process includes the following first comparison process and second comparison process: In the first comparison process, when the pull-up current is supplied to one of the two connection terminals, the voltage at the other connection terminal is compared with the judgment voltage. as well as The second comparison process involves comparing the voltage at one of the two connection terminals with the determination voltage while supplying the pull-up current to the other connection terminal of the two connection terminals. Based on the results of the first comparison process and the second comparison process, the specific fault sensor senses the presence or absence of a specific fault at the two connection terminals.

2. The light-emitting element driving device according to claim 1, wherein... If, during the first comparison process, when the pull-up current is supplied to one of the two connection terminals, the voltage at the other of the two connection terminals is higher than the judgment voltage, and furthermore, during the second comparison process, when the pull-up current is supplied to the other of the two connection terminals, the voltage at the other of the two connection terminals is higher than the judgment voltage, then the specific fault sensor senses the presence of a specific fault at the two connection terminals.

3. The light-emitting element driving device according to claim 1 or 2, wherein... One of the two connection terminals and the other connection terminal are respectively the connection terminals for the first channel and the second channel. During the execution period of the first comparison process, the pull-up circuit of the first channel supplies the pull-up current toward one of the two connection terminals, and the pull-up circuit of the second channel suspends supplying the pull-up current toward the other of the two connection terminals. During the execution period of the second comparison process, the pull-up circuit of the second channel supplies the pull-up current toward the other of the two connection terminals, and the pull-up circuit of the first channel suspends supplying the pull-up current toward one of the two connection terminals.

4. The light-emitting element driving device according to claim 1, wherein... The plurality of connection terminals include a first connection terminal, a second connection terminal, a third connection terminal, and a fourth connection terminal arranged in a continuous sequence. The first and second connection terminals are adjacent to each other, the second and third connection terminals are adjacent to each other, and the third and fourth connection terminals are adjacent to each other. In the first comparison process, the specific fault sensor compares the voltages at the second and fourth connection terminals with the judgment voltage while supplying the pull-up current to each of the first and third connection terminals. Similarly, in the second comparison process, the specific fault sensor compares the voltages at the first and third connection terminals with the judgment voltage while supplying the pull-up current to each of the second and fourth connection terminals. Based on the results of the first comparison process and the second comparison process, the specific fault sensor individually senses the presence or absence of a specific fault at the first connection terminal and the second connection terminal, the presence or absence of a specific fault at the second connection terminal and the third connection terminal, and the presence or absence of a specific fault at the third connection terminal and the fourth connection terminal.

5. The light-emitting element driving device according to claim 4, wherein... If, when the pull-up current is supplied toward the i-th connection terminal, the voltage at the (i+1)-th connection terminal is higher than the judgment voltage, and furthermore, when the pull-up current is supplied toward the (i+1)-th connection terminal, the voltage at the i-th connection terminal is higher than the judgment voltage, then the specific fault sensor senses the presence of a specific fault at the i-th connection terminal and the (i+1)-th connection terminal, where i is 1, 2, or 3.

6. The light-emitting element driving device according to claim 4 or 5, wherein The first connection terminal, the second connection terminal, the third connection terminal, and the fourth connection terminal are respectively the connection terminals for the first channel, the second channel, the third channel, and the fourth channel. During the execution period of the first comparison process, the pull-up circuits of the first and third channels supply pull-up current toward the first and third connection terminals, respectively, and the pull-up circuits of the second and fourth channels suspend supplying pull-up current toward the second and fourth connection terminals. During the execution period of the second comparison process, the pull-up circuits of the second channel and the fourth channel supply the pull-up current toward the second connection terminal and the fourth connection terminal, and the pull-up circuits of the first channel and the third channel suspend supplying the pull-up current toward the first connection terminal and the third connection terminal.

7. The light-emitting element driving device according to any one of claims 1, 2, 4 or 5, wherein For each of the plurality of channels, the specific fault sensor includes a pull-down circuit configured to draw a pull-down current from a corresponding one of the connection terminals, the pull-down current being set to be less than the magnitude of the pull-up current.

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