Semiconductor integrated circuit for driving light emitting element, light emitting element driving device, light emitting device, and vehicle

Abstract

To provide a light-emitting element driving semiconductor integrated circuit capable of suppressing a large current from flowing through light-emitting elements.SOLUTION: A light-emitting element driving semiconductor integrated circuit (100) constitutes at least a portion of a light-emitting element driving device configured to drive a plurality of light-emitting elements (Z0 to Z7) connected in series. The light-emitting element driving semiconductor integrated circuit includes: a controller (11, 12, 16, 17, R7) configured to have a first mode in which switching control is performed on a transistor (M2) connected in series to the plurality of light-emitting elements and a second mode in which linear control is performed on the transistor; and a first detector (12) configured to detect that a current flowing through a sense resistor (R2) connected in series to the plurality of light-emitting elements and the transistor reaches a threshold value. The controller switches from the switching control to the linear control on the basis of an output of the first detector.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The invention disclosed in this specification relates to a semiconductor integrated circuit for driving a light-emitting element, and also to a light-emitting element driving device, and a light-emitting device and a vehicle using the same. [Background technology]

[0002] Automobile headlamps are configured to be able to switch between a state in which they function as passing headlamps that emit low beams, and a state in which they function as driving headlamps that emit high beams that can reach further ahead than low beams.

[0003] An example of a light-emitting device used as an automobile headlamp is disclosed in Patent Document 1. The light-emitting device (LED (Light Emitting Diode) lighting circuit) disclosed in Patent Document 1 has a plurality of light-emitting elements connected in series, and is configured so that all of the light-emitting elements are turned on when the device is used as a driving headlamp, and some of the light-emitting elements are short-circuited and only the remaining light-emitting elements are turned on when the device is used as a passing headlamp. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-47047 A (paragraphs 0029 to 0033) Summary of the Invention [Problem to be solved by the invention]

[0005] In the light-emitting device (LED lighting circuit) disclosed in Patent Document 1, when switching from a driving headlight to a passing headlight, the output voltage of the DC-DC converter that drives the light-emitting element drops. This drop in output voltage causes the charge stored in the output capacitor of the DC-DC converter to be released from the output capacitor, causing the output current of the DC-DC converter to temporarily become an overcurrent, which in turn causes a temporary overcurrent to flow through the LEDs that are not short-circuited. In other words, when switching from a driving headlight to a passing headlight, the LEDs that are not short-circuited are damaged.

[0006] In Patent Document 1, when switching from a driving headlight to a passing headlight, the LED is short-circuited in two stages, thereby reducing the output voltage of the DC-DC converter described above in two stages and reducing the overcurrent.

[0007] However, the light-emitting device (LED lighting circuit) disclosed in Patent Document 1 only reduces the degree of overcurrent and does not fundamentally solve the problem of overcurrent. Therefore, the value of the predetermined output voltage Va obtained by the first-stage output voltage reduction and the value of the maintenance time t1 for maintaining the predetermined output voltage Va must be experimentally optimized through a trial-and-error process to ensure that the overcurrent is reduced to the desired value. Because the optimal values ​​of Va and t1 change depending on changes in LED specifications or individual variations in LEDs, it was difficult to guarantee that the light-emitting device (LED lighting circuit) disclosed in Patent Document 1 would reduce the overcurrent to the desired value.

[0008] In addition to the above-mentioned switching from high beam to low beam, for example, in vehicle lamp control, when performing control to sequentially turn on a plurality of light-emitting elements, control to sequentially turn off a plurality of light-emitting elements, control to turn on a plurality of light-emitting elements arranged in a matrix in an animation manner, control to turn on a plurality of light-emitting elements in an ADB (Adaptive Driving Beam) manner, etc., the number of light-emitting elements that are turned on may decrease, and a large current may flow through the light-emitting elements. Furthermore, for example, if some of the plurality of light-emitting elements have a ground fault, a large current may flow through the remaining light-emitting elements that are not ground-faulted. [Means for solving the problem]

[0009] The semiconductor integrated circuit for driving light-emitting elements disclosed in this specification constitutes at least a part of a light-emitting element driving device configured to vary the number of light-emitting elements that are turned on among a plurality of light-emitting elements connected in series. The semiconductor integrated circuit for driving light-emitting elements includes a control unit configured to have a first mode for switching control of transistors connected in series to the plurality of light-emitting elements and a second mode for linear control of the transistors, and a first detection unit configured to detect whether a current flowing through a sense resistor connected in series to the plurality of light-emitting elements and the transistors has reached a threshold. The control unit switches from the switching control to the linear control based on an output of the first detection unit.

[0010] The present specification discloses a light-emitting element driving device configured to drive a plurality of light-emitting elements connected in series, the light-emitting element driving device including: transistors connected in series to the plurality of light-emitting elements; a control unit configured to have a first mode for switching control of the transistors and a second mode for linear control of the transistors; sense resistors connected in series to the plurality of light-emitting elements and the transistors; and a first detection unit configured to detect whether a current flowing through the sense resistor reaches a threshold value, and the control unit switches from the switching control to the linear control based on an output of the first detection unit.

[0011] The light emitting device disclosed in this specification has a configuration including the light emitting element driving device configured as described above and the plurality of light emitting elements.

[0012] The vehicle disclosed in this specification has a configuration including the light emitting device having the above configuration. [Effects of the Invention]

[0013] According to the semiconductor integrated circuit for driving a light-emitting element, the light-emitting element driving device, the light-emitting device, and the vehicle disclosed in this specification, it is possible to prevent a large current from flowing through the light-emitting element. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a light emitting device. [Figure 2] FIG. 2 is a diagram showing an example of the configuration of the switch and the switch control circuit. [Figure 3] 2 is a time chart showing waveforms of voltages and the like at various parts of the light emitting device shown in FIG. [Figure 4] FIG. 4 is a diagram showing another example of the configuration of the light emitting device. [Figure 5] FIG. 5 is a diagram showing still another example of the configuration of the light emitting device. [Figure 6] FIG. 6 is an external view (front) of a vehicle on which a light emitting device is mounted. [Figure 7] FIG. 7 is an external view (rear view) of a vehicle on which a light emitting device is mounted. [Figure 8] FIG. 8 is an external view of the LED headlight module. [Figure 9] FIG. 9 is an external view of the LED turn lamp module. [Figure 10] FIG. 10 is an external view of the LED rear lamp module. DETAILED DESCRIPTION OF THE INVENTION

[0015] In this specification, a MOS (Metal Oxide Semiconductor) field effect transistor refers to a field effect transistor whose gate structure is composed of at least three layers: a layer made of a conductor or a semiconductor such as polysilicon with a low resistance, an insulating layer, and a P-type, N-type, or intrinsic semiconductor layer. In other words, the gate structure of a MOS field effect transistor is not limited to a three-layer structure of metal, oxide, and semiconductor.

[0016] In this specification, the reference voltage means a voltage that is constant under ideal conditions, but in reality it is a voltage that may fluctuate slightly due to temperature changes and the like.

[0017] <Light-emitting device> Fig. 1 is a diagram showing an example of the configuration of a light-emitting device. The light-emitting device shown in Fig. 1 includes a light-emitting element driving IC 100. The light-emitting device shown in Fig. 1 includes light-emitting diodes Z0 to Z7 that are light-emitting elements, and a light-emitting element driving device that drives the light-emitting elements. The light-emitting element driving device includes the light-emitting element driving IC 100.

[0018] The light emitting element driving device described above further includes a coil L1, an N-channel MOS field effect transistor (hereinafter referred to as an NMOS transistor) M1 which is a switching element, a Schottky barrier diode D1, and an output capacitor C1.

[0019] The coil L1, the NMOS transistor M1, the Schottky barrier diode D1, and the output capacitor C1 constitute a step-up / step-down DC / DC converter. IN DC output voltage V OUT Convert to.

[0020] The light-emitting element driving device described above further includes sense resistors R1 and R2, a P-channel MOS field effect transistor (hereinafter referred to as a PMOS transistor) M2, light-emitting diodes Z0 to Z7, a diode D2, a capacitor C2, resistors R3 and R4, and an EEPROM (Electrically Erasable Programmable Read Only Memory) 200.

[0021] The light emitting element driving device described above further includes switches SW0 to SW7 (see FIG. 2, not shown in FIG. 1) and a switch control circuit 300 (see FIG. 2, not shown in FIG. 1).

[0022] The light-emitting element driving IC 100 is a semiconductor integrated circuit device (so-called LED driver IC) that integrates a constant voltage circuit 1, a logic circuit 2, an operational amplifier 3, an adder 4, a DAC (Digital Analog Converter) 5, an error amplifier 6, an oscillator 7, a slope circuit 8, a comparator 9, a boost driving circuit 10, an operational amplifier 11, a comparator 12, a current limit circuit 13, an adder 14, a PWM (Pulse Width Modulation) circuit 15, an inverter 16, a switch 17, a comparator 18, and resistors R5 to R7.

[0023] The operational amplifier 11, the comparator 12, the inverter 16, the switch 17, and the resistor R7 function as a control section configured to have a first mode for switching-controlling the PMOS transistor M2 and a second mode for linearly controlling the PMOS transistor M2.

[0024] The comparator 12 functions as a first detector configured to detect whether the current flowing through the sense resistor R2 reaches a threshold value. That is, in this embodiment, the control unit and the first detector share the comparator 12.

[0025] The comparator 18 functions as a second detection unit configured to detect whether the gate-source voltage of the PMOS transistor M2 reaches a predetermined value.

[0026] In addition, the light-emitting element driving IC 100 has terminals VIN, GL, PGND, IS, SNSP, SNSN, PGATE, SO, SI, CSB, SCLK, SDA, SCL, COMP, and RT to establish electrical connection with the outside.

[0027] Input voltage V IN is supplied to the terminal VIN, one end of the coil L1, one end of the output capacitor C1, and the cathode of the diode D2. The other end of the coil L1 is connected to the drain of the NMOS transistor M1 and the anode of the Schottky barrier diode D1. The source of the NMOS transistor M1 is connected to one end of the sense resistor R1 and the terminal IS. The other end of the sense resistor R1 is connected to the ground potential and the terminal PGND. The gate of the NMOS transistor M1 is connected to the terminal GL. A square wave switch voltage V is applied to the other end of the coil L1 by switching the NMOS transistor M1. SW occurs.

[0028] The cathode of the Schottky barrier diode D1 is connected to the other end of the output capacitor C1, one end of the sense resistor R2, and the terminal SNSP. The other end of the output capacitor C1 is connected to the output voltage V OUT occurs. The output voltage V OUT is the switch voltage V SW is smoothed.

[0029] The other end of the sense resistor R2 is connected to the source of the PMOS transistor M2 and the terminal SNSN. The gate of the PMOS transistor M2 is connected to the terminal PGATE. The drain of the PMOS transistor M2 is connected to the anode of the series circuit of the light emitting diodes Z0 to Z7.

[0030] The cathode of the series circuit of the light emitting diodes Z0 to Z7 is connected to the anode of the diode D2, which has its cathode connected to the terminal VIN. The diode D2 may be, for example, a Schottky barrier diode.

[0031] One end of the clock frequency setting resistor R3 is connected to the terminal RT, and the other end of the resistor R3 is connected to the ground potential.

[0032] One end of the resistor R4 is connected to the terminal COMP, and the other end of the resistor R4 is connected to the ground potential via a phase compensation capacitor C2.

[0033] The constant voltage circuit 1 regulates the input voltage V supplied to the VIN terminal. IN Using a constant voltage V REG and supplies it to each part of the light-emitting element driving IC 100.

[0034] The logic circuit 2 performs dimming control and the like based on the settings stored in the EEPROM 200. The logic circuit 2 outputs a current setting value ISETX, an overcurrent limit value OCLIM, and a duty value D. The logic circuit 2 performs so-called DC dimming control by changing the value of the current setting value ISETX. The logic circuit 2 performs so-called PWM dimming control by changing the value of the duty value D.

[0035] The non-inverting input terminal of the operational amplifier 3 is connected to the terminal SNSP via a resistor R5, and the inverting input terminal of the operational amplifier 3 is connected to the terminal SNSN via a resistor R6. The operational amplifier 3 outputs a voltage according to the voltage across the sense resistor R2.

[0036] The output voltage of the operational amplifier 3 is offset by the adder 4 so that it increases by 0.2 V. The feedback voltage V generated by the adder 4 is FB is supplied to the inverting input terminal of the error amplifier 6, the non-inverting input terminal of the operational amplifier 11, and the non-inverting input terminal of the comparator 12. The feedback voltage V FBis a voltage based on the current output from the DC / DC converter and flowing through the sense resistor R2.

[0037] DAC5 converts the current setting value ISETX into an analog voltage, the DC dimming voltage V DCDIM Convert to DC dimming voltage V DCDIM is supplied to the non-inverting input terminal of the error amplifier 6.

[0038] Error amplifier 6 outputs the feedback voltage V FB and DC dimming voltage V DCDIM Error voltage V according to the difference ERR Generate.

[0039] An oscillator 7 generates a clock signal CK. The clock frequency of the clock signal CK is determined by the resistance value of a resistor R3 connected to a terminal RT. The clock signal CK is supplied to a slope circuit 8 and a boost driver circuit 10.

[0040] The slope circuit 8 generates a triangular or sawtooth waveform slope voltage V using the clock signal CK. SLP Generates a slope voltage V SLP The slope of varies depending on the voltage supplied to the terminal IS, that is, the source voltage of the NMOS transistor M1.

[0041] Comparator 9 detects the error voltage V ERR and slope voltage V SLP The comparison result is supplied to the boost driver circuit 10.

[0042] The boost driver circuit 10 generates a gate signal for the NMOS transistor M1 based on the clock signal CK and the output of the comparator 9, and supplies the signal to the gate of the NMOS transistor M1 via the terminal GL.

[0043] With the above circuit configuration, the DC / DC converter outputs the output current I OUT is feedback controlled so that it approaches the target current.

[0044] The current limit circuit 13 generates a voltage V based on the overcurrent limit value OCLIM. LIM The adder 14 outputs the DC dimming voltage V DCDIM and voltage V LIM The voltage obtained by adding these is supplied to the inverting input terminal of the operational amplifier 11 and the inverting input terminal of the comparator 12.

[0045] Op-amp 11 operates at a feedback voltage V FB and the output voltage of adder 14. The minimum value of the output voltage of operational amplifier 11 is 7.5 V less than the voltage applied to terminal SNSP. The maximum value of the output voltage of operational amplifier 11 is the same as the voltage applied to terminal SNSP.

[0046] The output terminal of the operational amplifier 11 is connected to the terminal PGATE via a resistor R7. When the switch 17 is off, the PMOS transistor M2 is linearly controlled by the output voltage of the operational amplifier 11.

[0047] Comparator 12 detects the feedback voltage V FB and the output voltage (threshold setting voltage) of the adder 14, and controls the switch 17 based on the comparison result. When the switch 17 is on, the output voltage (threshold setting voltage) of the adder 14 becomes equal to the feedback voltage V FB If it becomes greater, the comparator 12 switches the switch 17 from on to off.

[0048] The PWM circuit 15 outputs a PWM dimming voltage V PWMDIM and generates the PWM dimming voltage V PWMDIM to the inverter 16. The inverter 16 supplies the PWM dimming voltage V PWMDIM When the output voltage of the inverter 16 is at a high level, the value of the output voltage of the inverter 16 is the same as the voltage applied to the terminal SNSP. When the output voltage of the inverter 16 is at a low level, the value of the output voltage of the inverter 16 is 7.5 V less than the voltage applied to the terminal SNSP.

[0049] The output terminal of the inverter 16 is connected to the terminal PGATE via the switch 17. When the switch 17 is on, the output voltage of the inverter 16 controls the switching of the PMOS transistor M2.

[0050] The non-inverting input terminal of the comparator 18 is connected to the terminal PGATE. The inverting input terminal of the comparator 18 is connected to a reference voltage V that is generated based on a value 7.5 V less than the voltage applied to the terminal SNSP. REF The comparator 18 compares the output voltage at the terminal PGATE with the reference voltage V REF The output voltage of the terminal PGATE is compared with the reference voltage V REF If it is smaller, the comparator 18 switches the switch 17 from off to on.

[0051] 2 is a diagram showing an example of the configuration of the switches SW0 to SW7 and the switch control circuit 300. In the example configuration shown in FIG. 2, the switches SW0 to SW7 are each an NMOS transistor. The switch SWk (k is an integer between 0 and 7) is connected in parallel to the light-emitting diode Zk. When the switch SWk is off, a current flows through the light-emitting diode Zk. On the other hand, when the switch SWk is on, no current flows through the light-emitting diode Zk.

[0052] The switch control circuit 300 controls the on / off states of the switches SW0 to SW7. The switch control circuit 300 controls the on / off states of the switches SW0 to SW7, thereby controlling the lighting states of the light-emitting diodes Z0 to Z7.

[0053] The switch control circuit 300 and the logic circuit 2 do not communicate with each other. Therefore, the logic circuit 2 does not know how the switch control circuit 300 controls the lighting states of the light-emitting diodes Z0 to Z7.

[0054] Fig. 3 is a time chart showing waveforms of voltages and the like at various parts of the light emitting device shown in Fig. 1. Fig. 3 is a time chart showing the transition from when all of the switches SW0 to SW7 are off to when one of the switches SW0 to SW7 is turned on.

[0055] When the number of lit light-emitting diodes Z0 to Z7 decreases from 8 to 7, the anode voltage V of light-emitting diode Z7 Z7A decreases, and the output current I of the DC / DC converter mentioned above OUT reaches the threshold value TH. The threshold value TH corresponds to the output voltage of the adder 14 (threshold setting voltage).

[0056] The output current I of the DC / DC converter mentioned above OUT When the voltage Vcc reaches the threshold TH, the switch 17 is switched from on to off by the output voltage of the comparator 12. This ends the switching control period.

[0057] The logic circuit 2 also monitors the state of the switch 17, and stops outputting the current setting value ISETX and the overcurrent limit value OCLIM during the period (mask period) from when the switch 17 is switched from on to off until a predetermined time has elapsed. As a result, during the mask period, the value of the gate voltage VG of the PMOS transistor M2 is set to the voltage V supplied to the terminal SNSP. SNSP , and the PMOS transistor M2 is turned off. By turning off the PMOS transistor M2, the output current I OUT becomes zero.

[0058] By providing a mask period, the output current I of the DC / DC converter mentioned above can be reduced. OUT This can reliably prevent overshooting.

[0059] When the mask period ends, the linear control period begins. During the linear control period, the PMOS transistor M2 is linearly controlled by the output voltage of the operational amplifier 11. Since the source-drain resistance of the PMOS transistor M2 during the linear control period is larger than the source-drain resistance of the PMOS transistor M2 during the switching control period, the output current I of the DC / DC converter described above OUT 1 can prevent a large current from flowing through the light-emitting diodes that supply current among the light-emitting diodes Z0 to Z7.

[0060] The output voltage of the PGATE terminal is the reference voltage V REF When the voltage Vcc becomes smaller than the reference voltage Vdc, the linear control period ends and the switching control period begins, thereby allowing the light emitting device shown in FIG.

[0061] Fig. 4 is a diagram showing another example of the configuration of a light emitting device. The light emitting device shown in Fig. 4 differs from the light emitting device shown in Fig. 1 in that it includes an MPU (Micro Processor Unit) 400 instead of the EEPROM 200, but is otherwise identical to the light emitting device shown in Fig. 1. The logic circuit 2 of the light emitting device shown in Fig. 4 performs dimming control and the like based on settings sent from the MPU 400.

[0062] Fig. 5 is a diagram showing yet another example of the configuration of a light-emitting device. The light-emitting device shown in Fig. 5 differs from the light-emitting device shown in Fig. 1 in that it includes a light-emitting element driving IC 101 instead of the light-emitting element driving IC 100, but is otherwise the same as the light-emitting device shown in Fig. 1.

[0063] The light-emitting element driving IC 101 has a configuration in which a discharge circuit 20 and a clamp element 21 are added to the light-emitting element driving IC 100.

[0064] During the linear control period, the discharge circuit 20 draws current from the output terminal of the error amplifier 6. As a result, during the linear control period when the value of the source-drain resistance of the PMOS transistor M2 is higher than during the switching control period, the error voltage V ERR The error voltage V ERR When the output current I of the DC / DC converter decreases, the boost driver circuit 10 OUT 5 controls the switching of the NMOS transistor M1 so that the loss in the PMOS transistor M2 during the linear control period is reduced.

[0065] The value of the current drawn by the discharge circuit 20 is not particularly limited. For example, the value of the current drawn by the discharge circuit 20 is set based on the control state of the terminal PGATE. In this case, the discharge circuit 20 may include a current mirror circuit and draw a mirror current of the current flowing through the terminal PGATE from the output terminal of the error amplifier 6. Alternatively, for example, the discharge circuit 20 may include a constant current circuit and draw a constant current from the output terminal of the error amplifier 6. Alternatively, for example, the discharge circuit 20 may include a variable current circuit and set the value of the output current of the variable current circuit based on the circuit constants of externally connected discrete components, the output signal of the logic circuit 2, etc., and draw the output current of the variable current circuit from the output terminal of the error amplifier 6.

[0066] The clamp element 21 clamps the error voltage V ERR The clamp element 21 may be, for example, a Zener diode. The discharge circuit 20 draws current to clamp the lower limit of the error voltage V ERR If the output current I of the DC / DC converter mentioned above decreases too much when switching control is restored. OUT By providing the clamp element 21, the output current I of the DC / DC converter can be reduced when switching control is restored. OUT It is possible to prevent shortage of

[0067] <Application> The above-described light emitting device can be suitably used, for example, as shown in Figures 6 and 7, as a headlight (including high beam / low beam / parking lamp / fog lamp, etc., as appropriate) X11 of a vehicle X10, a light source for daylight running (DRL) X12, a tail lamp (including parking lamp, back lamp, etc., as appropriate) X13, a stop lamp X14, and a turn lamp X15.

[0068] The above-described light emitting device may be provided as a module (such as the LED headlight module Y10 in FIG. 8, the LED turn lamp module Y20 in FIG. 9, and the LED rear lamp module Y30 in FIG. 10). Also, the light emitting device may be provided in the form of a driver with a light emission number control function, which is a semi-finished product obtained by removing external components such as light emitting diodes and light emitting element driving ICs from the above-described light emitting device.

[0069] <Other> The above-described embodiments should be considered to be illustrative in all respects and not restrictive. The technical scope of the present invention is indicated by the claims, not by the description of the above-described embodiments, and should be understood to include all modifications that fall within the meaning and scope of the claims.

[0070] In the above embodiment, a configuration using a light-emitting diode as the light-emitting element has been described as an example, but the configuration of the present invention is not limited to this, and for example, an organic EL (Electro Luminescence) element can also be used as the light-emitting element.

[0071] In the above embodiment, a PMOS transistor is used as the transistor connected in series to the light-emitting diode, but the present invention is not limited to this. For example, a bipolar transistor may be used instead of the PMOS transistor M2.

[0072] In the above embodiment, the light emitting device is configured to include the IC 100 for driving the light emitting element, but for example, the portion corresponding to the IC 100 for driving the light emitting element may be configured with a plurality of ICs.

[0073] The semiconductor integrated circuit (100) for driving light-emitting elements described above is a semiconductor integrated circuit for driving light-emitting elements that constitutes at least a part of a light-emitting element driving device configured to drive a plurality of light-emitting elements (Z0 to Z7) connected in series, and comprises a control unit (11, 12, 16, 17, R7) configured to have a first mode for switching control of a transistor (M2) connected in series to the plurality of light-emitting elements and a second mode for linearly controlling the transistor, and a first detection unit (12) configured to detect that the current flowing through a sense resistor (R2) connected in series to the plurality of light-emitting elements and the transistor has reached a threshold value, and the control unit is configured to switch from the switching control to the linear control based on the output of the first detection unit (first configuration).

[0074] The semiconductor integrated circuit for driving a light-emitting element having the first configuration can prevent a large current from flowing through the light-emitting element.

[0075] The semiconductor integrated circuit for driving a light-emitting element of the first configuration may further include a second detection unit (18) configured to detect whether the gate-source voltage or base current of the transistor has reached a predetermined value, and the control unit may be configured to switch from the linear control to the switching control based on the output of the second detection unit (second configuration).

[0076] The semiconductor integrated circuit for driving a light-emitting element having the second configuration can automatically return to switching control.

[0077] In the semiconductor integrated circuit for driving a light-emitting element of the first or second configuration, when the control unit switches from the switching control to the linear control, the control unit may be configured (third configuration) to transition from a switching control period in which the switching control is performed to a linear control period in which the linear control is performed via a mask period in which the transistor is turned off.

[0078] The semiconductor integrated circuit for driving a light-emitting element having the third configuration can reliably prevent overshoot of the current flowing through the sense resistor.

[0079] In the semiconductor integrated circuit for driving a light-emitting element of any of the first to third configurations, the light-emitting element driving device may be configured to include a DC / DC converter that converts an input voltage into an output voltage, and a switching control unit (8, 9, 10) that controls a switching element in the DC / DC converter based on an error voltage output from an error amplifier (6) that amplifies the difference between a first voltage based on an output current of the DC / DC converter and a second voltage corresponding to a target current, and is configured to supply the output current of the DC / DC converter to the sense resistor, and the semiconductor integrated circuit for driving a light-emitting element may be configured (fourth configuration) further including a discharge unit (20) that is configured to draw current from an output terminal of the error amplifier when the control unit is performing the linear control.

[0080] The semiconductor integrated circuit for driving a light-emitting element having the fourth configuration can suppress loss in the transistor.

[0081] The semiconductor integrated circuit for driving a light-emitting element of the fourth configuration may be configured (fifth configuration) further comprising a clamp element (21) that clamps the lower limit of the error voltage.

[0082] The semiconductor integrated circuit for driving a light-emitting element having the fifth configuration can prevent a shortage of current flowing through the sense resistor when switching from linear control to switching control.

[0083] The light-emitting element driving device described above is a light-emitting element driving device configured to drive a plurality of light-emitting elements connected in series, and includes a transistor (M2) connected in series to the plurality of light-emitting elements, a control unit (11, 12, 16, 17, R7) configured to have a first mode for switching control of the transistor and a second mode for linearly controlling the transistor, a sense resistor (R2) connected in series to the plurality of light-emitting elements and the transistor, and a first detection unit (12) configured to detect that the current flowing through the sense resistor has reached a threshold value, and the control unit is configured to switch from the switching control to the linear control based on the output of the first detection unit (sixth configuration).

[0084] The light emitting element driving device having the sixth configuration can prevent a large current from flowing through the light emitting element.

[0085] The light emitting device described above has a configuration (seventh configuration) including the light emitting element driving device of the sixth configuration and the plurality of light emitting elements (Z0 to Z7).

[0086] The light emitting device having the seventh configuration can prevent a large current from flowing through the light emitting element.

[0087] The vehicle described above has a configuration (eighth configuration) that includes the light emitting device of the seventh configuration.

[0088] The vehicle (X10) having the eighth configuration can prevent a large current from flowing through the light emitting element. [Explanation of symbols]

[0089] 1 Constant voltage circuit 2 Logic Circuits 3 Operational Amplifiers 4 Adder 5 DAC 6 Error Amplifier 7. Oscillators 8 Slope Circuit 9, 12, 18 Comparators 10 Boost drive circuit 11 Operational Amplifiers 13 Current limit circuit 14 Adder 15 PWM circuit 16 inverters 17. SW0~SW7 switches 20 Discharge circuit 21 Clamping element 100, 101 Light emitting element driving IC 200 EEPROM 300 Switch control circuit C1 Output capacitor C2 capacitor D1 Schottky barrier diode D2 diode L1 coil M1 NMOS transistor M2 PMOS transistor R1, R2 Sense resistors R3~R7 resistance X10 vehicle X11 headlight X12 Day and Night Running Light X13 tail lamp X14 Stop lamp X15 Turn Lamp Y10 LED headlight module Y20 LED Turn Lamp Module Y30 LED rear lamp module Z0~Z7 light emitting diodes

Claims

1. A semiconductor integrated circuit for driving a light emitting element constituting at least a part of a light emitting element driving device configured to drive a plurality of light emitting elements connected in series, a control unit configured to have a first mode for switching-controlling transistors connected in series to the plurality of light-emitting elements and a second mode for linearly controlling the transistors; a first detection unit configured to detect whether a current flowing through a sense resistor connected in series to the plurality of light-emitting elements and the transistor reaches a threshold; a second detection unit configured to detect whether the gate-source voltage or the base current of the transistor reaches a predetermined value; Equipped with the control unit switches from the switching control to the linear control based on the output of the first detection unit, and switches from the linear control to the switching control based on the output of the second detection unit, and when the control unit switches from the switching control to the linear control, transitions from a switching control period in which the switching control is performed to a linear control period in which the linear control is performed, via a mask period in which the transistor is turned off.

2. A semiconductor integrated circuit for driving a light emitting element constituting at least a part of a light emitting element driving device configured to drive a plurality of light emitting elements connected in series, a control unit configured to have a first mode for switching-controlling transistors connected in series to the plurality of light-emitting elements and a second mode for linearly controlling the transistors; a first detection unit configured to detect whether a current flowing through a sense resistor connected in series to the plurality of light-emitting elements and the transistor reaches a threshold; a second detection unit configured to detect whether the gate-source voltage or the base current of the transistor reaches a predetermined value; Equipped with the control unit includes a switch, and is configured to change the switch from on to off and switch from the switching control to the linear control based on the output of the first detection unit, and to change the switch from off to on and switch from the linear control to the switching control based on the output of the second detection unit, and when the control unit switches from the switching control to the linear control, to transition from a switching control period in which the switching control is performed to a linear control period in which the linear control is performed, via a mask period in which the transistor is turned off.

3. A semiconductor integrated circuit for driving a light emitting element constituting at least a part of a light emitting element driving device configured to drive a plurality of light emitting elements connected in series, a control unit configured to have a first mode for switching-controlling transistors connected in series to the plurality of light-emitting elements and a second mode for linearly controlling the transistors; a first detection unit configured to detect whether a current flowing through a sense resistor connected in series to the plurality of light-emitting elements and the transistor reaches a threshold; Equipped with the control unit comprises: an operational amplifier configured to output a voltage corresponding to the difference between a feedback voltage based on a potential difference between both ends of the sense resistor and a threshold setting voltage; a comparator configured to compare the feedback voltage with the threshold setting voltage; an inverter configured to receive a PWM dimming voltage indicating a duty of PWM dimming; a switch having a first end connected to an output end of the inverter and a second end connected to a control end connecting terminal for connecting to a control end of the transistor, the switch being configured to switch between an on state and an off state according to an output of the comparator; and a resistor having a first end connected to the output end of the operational amplifier and a second end connected to the control end connecting terminal,

4. the light-emitting element driving device includes a DC / DC converter that converts an input voltage into an output voltage, and a switching control unit that controls a switching element in the DC / DC converter based on an error voltage output from an error amplifier that amplifies a difference between a first voltage based on an output current of the DC / DC converter and a second voltage corresponding to a target current, and is configured to supply the output current of the DC / DC converter to the sense resistor; The semiconductor integrated circuit for driving a light-emitting element according to any one of claims 1 to 3, further comprising a discharge unit configured to draw current from the output terminal of the error amplifier when the control unit is performing the linear control.

5. 5. The semiconductor integrated circuit for driving a light-emitting element according to claim 4, further comprising a clamping element for clamping a lower limit of the error voltage.

6. A light emitting element driving device configured to drive a plurality of light emitting elements connected in series; the plurality of light-emitting elements; Equipped with A light emitting device, wherein at least a part of the light emitting element driving device is configured by the semiconductor integrated circuit for driving a light emitting element according to any one of claims 1 to 5.

7. A vehicle comprising the light emitting device according to claim 6.

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