CN111902951B - Light-emitting element driving device - Google Patents
Light-emitting element driving device Download PDFInfo
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- CN111902951B CN111902951B CN201880091696.XA CN201880091696A CN111902951B CN 111902951 B CN111902951 B CN 111902951B CN 201880091696 A CN201880091696 A CN 201880091696A CN 111902951 B CN111902951 B CN 111902951B
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Classifications
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/40—Details of LED load circuits
- H05B45/44—Details of LED load circuits with an active control inside an LED matrix
- H05B45/48—Details of LED load circuits with an active control inside an LED matrix having LEDs organised in strings and incorporating parallel shunting devices
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/30—Driver circuits
- H05B45/345—Current stabilisation; Maintaining constant current
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/30—Driver circuits
- H05B45/395—Linear regulators
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
- Y02B20/30—Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
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- Circuit Arrangement For Electric Light Sources In General (AREA)
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Abstract
The light emitting device (X1) has a light emitting element light source (200) in which a plurality of light emitting elements (201-203) (for example, light emitting diodes) are connected in series, and a light emitting element driving device (100) that drives the light emitting element light source (200). A light emitting element driving device (100) is provided with: a current driver (101) that generates an output current (Iout) flowing into a light-emitting element light source (200) connected between an application terminal of a power supply voltage (Vin) and a ground terminal; and a bypass function unit (112) that bypasses at least one of the plurality of light emitting elements (201-203) that constitute the light emitting element light source (200) when the power supply voltage (Vin) decreases, and reduces the number of series stages of light emitting elements through which the output current (Iout) flows.
Description
Technical Field
The invention disclosed in the present specification relates to a light emitting element driving device.
Background
Conventionally, various light-emitting element driving devices have been developed for driving light-emitting elements such as light-emitting diodes (hereinafter referred to as LEDs (LIGHT EMITTING diodes)).
Patent document 1 is an example of a conventional technology related to the above technology.
Prior art literature
Patent literature
Patent document 1: japanese patent laid-open publication No. 2011-244677
Disclosure of Invention
Problems to be solved by the invention
However, in the case of a light-emitting element light source in which a plurality of light-emitting elements are connected in series as a driving target, in the conventional light-emitting element driving device, if the power supply voltage drops to a level near the total forward drop voltage of the light-emitting element light source, the light-emitting element light source may be turned off.
In view of the above problems found by the present inventors, an object of the present application disclosed in the present specification is to provide a light emitting element driving device capable of maintaining the lighting of a light emitting element light source even if a power supply voltage is reduced.
Means for solving the problems
The light-emitting element driving device disclosed in the present specification is configured to have: a current driver that generates an output current flowing into a light emitting element light source connected between an application terminal of a power supply voltage and a ground terminal; and a bypass function unit that bypasses at least one of the plurality of light emitting elements constituting the light emitting element light source when the power supply voltage decreases, and reduces the number of series stages (first configuration) of the light emitting elements through which the output current flows.
In the light emitting element driving device having the first configuration, the bypass function unit may include: a comparator that compares the power supply voltage or a divided voltage of the power supply voltage with a predetermined threshold voltage and generates a comparison signal; and a switch for switching whether or not to bypass at least one of the plurality of light emitting elements based on the comparison signal (second configuration).
In the light-emitting element driving device configured by the second configuration, the comparator may be a hysteresis comparator (third configuration).
In the light-emitting element driving device configured in the first configuration, the bypass function unit may be configured to gradually change the output current flowing into the bypass-target light-emitting element when the number of series stages of the light-emitting elements through which the output current flows is switched (fourth configuration).
In the light-emitting element driving device configured in the fourth configuration, the bypass function unit may be configured to variably control a set value of a branch current of the light-emitting element of the output current, which does not pass through the bypass target, based on a control current corresponding to the power supply voltage or a divided voltage of the power supply voltage (a fifth configuration).
In the light-emitting element driving device configured in the fifth configuration, the control current may be configured to start flowing when the power supply voltage or the divided voltage becomes higher than a predetermined threshold voltage (sixth configuration).
In the light emitting element driving device configured by the fifth or sixth configuration, the set value of the branch current may be reduced from a maximum value larger than the target value of the output current as the control current increases (seventh configuration).
In the light emitting element driving device according to any one of the fifth to seventh configurations, the bypass function unit may include: and a control current generation unit that generates the control current so that the terminal voltage of the bypass control terminal through which the control current flows matches the threshold voltage (eighth configuration).
In the light emitting element driving device configured by the eighth configuration, the terminal voltage may be a voltage obtained by subtracting a voltage drop amount corresponding to the control current from the power supply voltage or the divided voltage (ninth configuration).
In the light emitting element driving device configured by the eighth or ninth configuration, the bypass function unit may further include: a first coefficient multiplication unit that multiplies a reference current for determining a target value of the output current by a first coefficient; a second coefficient multiplication unit that multiplies the control current by a second coefficient; a subtracting section that subtracts an output signal of the second coefficient multiplying section from an output signal of the first coefficient multiplying section; and a current source that generates the branch current from an output signal of the subtracting section (tenth configuration).
In the light emitting element driving device configured by the eighth or ninth configuration, the bypass function unit may further include: a reference voltage generation unit that generates a reference voltage corresponding to a target value of the output current; a current detection unit that generates a sense voltage corresponding to the branch current; a bias applying unit that applies a bias voltage corresponding to the control current to the sense voltage; and a branch current generation unit that generates the branch current so that the sense voltage to which the bias voltage is applied coincides with the reference voltage (eleventh configuration).
In the light-emitting element driving device according to any one of the eighth to eleventh configurations, the light-emitting element driving device may be configured such that a first resistor having a first end connected to the application terminal of the power supply voltage and a second end connected to the application terminal of the divided voltage, a second resistor having a first end connected to the application terminal of the divided voltage and a second end connected to a ground terminal, and a third resistor having a first end connected to the application terminal of the divided voltage and a second end connected to the bypass control terminal are externally provided (twelfth configuration).
In the light-emitting element driving device according to any one of the eighth to twelfth configurations, the bypass control terminal may be adjacent to the power supply voltage input terminal (thirteenth configuration).
In the light-emitting element driving device according to any one of the eighth to thirteenth configurations, the external terminal through which the branch current flows may be adjacent to at least one of the output terminal and the ground terminal of the output current (fourteenth configuration).
In the light-emitting element driving device configured by any one of the first to fourteenth configurations, the current driver may be of a current source type (fifteenth configuration).
In the light-emitting element driving device configured by any one of the first to fourteenth configurations, the current driver may be configured to be a current sink type (sixteenth configuration).
The light-emitting device disclosed in the present specification is configured to include: a light-emitting element light source in which a plurality of light-emitting elements are connected in series; and a light-emitting element driving device (seventeenth structure) configured to be configured to drive the light-emitting element light source, the light-emitting element driving device being configured to be any one of the first to sixteenth structures.
In the light-emitting device configured by the seventeenth configuration, the light-emitting element may be a light-emitting diode or an organic EL element (eighteenth configuration).
In the light-emitting device according to the seventeenth or eighteenth aspect, the light-emitting device may further include: a substrate on which wiring patterns for mounting the light-emitting element light source and the light-emitting element driving device are laid; and a socket (socket) for mounting the substrate (nineteenth configuration).
The vehicle disclosed in the present specification is configured to include: a light-emitting device (twentieth structure) configured by any one of the seventeenth to nineteenth structures described above.
Effects of the invention
According to the light emitting element driving device disclosed in the present specification, the lighting of the light emitting element light source can be maintained even if the power supply voltage is reduced.
Drawings
Fig. 1 is a diagram showing an overall structure of a vehicle provided with an LED light emitting device.
Fig. 2 is a diagram showing a first embodiment of the bypass function unit.
Fig. 3 is a timing chart showing an example of the bypass operation in the first embodiment.
Fig. 4 is a diagram showing a second embodiment of the bypass function unit.
Fig. 5 is a timing chart showing an example of the bypass operation in the second embodiment.
Fig. 6 is a diagram showing an additional element example of the LED light emitting device.
Fig. 7 is a diagram showing a third embodiment of the bypass function unit.
Fig. 8 is a timing chart showing an example of the bypass operation in the third embodiment.
Fig. 9 is a diagram showing a first setting example of the external resistor (iout=100 mA)
Fig. 10 is a diagram showing a second setting example of the external resistor (iout=600ma)
Fig. 11 is a diagram showing a fourth embodiment of the bypass function unit.
Fig. 12 is a diagram showing a terminal arrangement of the LED driving device.
Fig. 13 is a top view of a socket type LED module.
Fig. 14 is a plan view showing another layout of LED chips.
FIG. 15 is an external view (front surface) of a vehicle equipped with an LED light-emitting device
FIG. 16 is an external view (back surface) of a vehicle equipped with an LED light-emitting device
Fig. 17 is an external view of the LED headlamp module.
Fig. 18 is an external view of the LED turn lamp module.
Fig. 19 is an external view of the LED back light module.
Detailed Description
< Integral Structure >
Fig. 1 is a diagram showing an overall structure of a vehicle provided with an LED light emitting device. The vehicle X in this figure includes an LED lighting device X1, a battery X2, and power switches X3a and X3b.
The LED lighting device X1 is a vehicle-mounted lamp that is turned on by receiving a supply of a power supply voltage Vin from a battery X2. Examples of the light emitting device X1 include a headlight, a daytime running light, a tail light, a stop light, and a turn light.
The battery X2 is a power source of the vehicle X, and a lead storage battery, a lithium ion battery, or the like is suitably used.
The power switches X3a and X2b are connected between the light emitting device X1 and the battery X2, respectively, and are turned on/off by receiving a control signal from a controller not shown.
< LED light emitting device >
Next, the internal structure of the LED light emitting device X1 will be described. The LED light emitting device X1 includes, in addition to the LED driving device 100 and the LED light source 200, resistors R1 to R4, capacitors C1 to C3, diodes D1 to D3, and a negative characteristic thermistor NTC as various discrete components external to the LED driving device 100.
Further, as a means for establishing electrical connection with the outside of the device, the LED driving device 100 has a plurality of external terminals (VIN pin, PBUS pin, SWCNT pin, CRT pin, DISC pin, GND pin, ISET pin, THD pin, SW pin, and IOUT pin in this figure). The VIN pin is a supply voltage input terminal. The PBUS pin is an abnormality detection input-output terminal. The SWCNT pin is a power supply voltage monitor terminal. The CRT pin is a CR timer setting terminal. The DISC pin is the CR timer discharge terminal. The GND pin is a ground terminal. The ISET pin is a reference current setting terminal. The THD pin is a temperature decay setting terminal. The SW pin is a bypass switch connection terminal. The IOUT pin is an output current output terminal.
The positive terminal of the battery X2 is connected to the first terminal of each of the power switches X3a and X3 b. The negative terminal of the battery X2 is connected to the ground terminal. A second terminal of the power switch X3a is connected to the anode of the diode D1. A second terminal of the power switch X3b is connected to the anode of each of the diodes D2 and D3. The cathodes of diodes D1 and D2 are connected to the VIN pin. The cathode of diode D3 is connected to the CRT pin. The diodes D1 to D3 connected in this way function as reverse current preventing diodes for cutting off the reverse current from the light emitting device X1 to the battery X2.
Resistors R1 and R2 are connected in series between the VIN pin and ground. The connection node between the resistors R1 and R2 is connected with the SWCNT pin. The resistors R1 and R2 connected in this way function as a voltage divider circuit that generates a monitor voltage Vm (=vin× { R2/(r1+r2) }) corresponding to the power supply voltage Vin. Resistor R3 is connected between the CRT pin and the DISC pin and functions as part of CR timer 106. Resistor R4 is connected between the ISET pin and the ground terminal, and functions as a part of reference current setting unit 109.
The capacitor C1 is connected between the VIN pin and the ground terminal and functions as an input smoothing capacitor. Capacitor C2 is connected between the IOUT pin and ground and functions as an output smoothing capacitor. Capacitor C3 is connected between the CRT pin and ground and functions as part of CR timer 106.
The negative characteristic thermistor NTC is connected between the THD pin and the ground terminal, and functions as a part (temperature detection element) of the reference current setting unit 109.
The LED driving device 100 is a monolithic silicon semiconductor integrated circuit device (so-called LED driver IC) that receives a supply of a power supply voltage Vin from a battery X2 and generates an output current Iout to be supplied to the LED light source 200.
The LED light source 200 is an LED string including a plurality of LED chips (LED chips 201 to 203 in the figure) connected in series. When the LED chips 201 to 203 are individually observed, they can be understood as individual LED elements, or as a light-emitting element aggregate in which a plurality of LED elements are combined in series or in parallel.
In the LED light emitting device X1 of the present embodiment, the anode of the LED light source 200 (=the anode of the LED chip 201 arranged on the highest potential side) is connected to the IOUT pin (=the output terminal of the output current IOUT) of the LED driving device 100. On the other hand, the cathode (=the cathode of the LED chip 203 arranged on the lowest potential side) of the LED light source 200 is connected to the ground terminal. The anode of the LED chip 203 (=the cathode of the LED chip 202) is connected to the SW pin of the LED driving device 100, and the reason thereof will be described later.
In the vehicle X, in a PWM (pulse width modulation ) dimming mode, the power switch X3a is turned on, and the power switch X3b is turned off. As a result, in the PWM dimming mode, the power supply voltage VIN is applied from the battery X2 to the VIN pin via the power switch X3a and the diode D1. In addition, the CRT pins are in an open circuit state with respect to battery X2. On the other hand, in the DC dimming mode, the power switch X3a is turned off and the power switch X3b is turned on. As a result, in the DC dimming mode, the power supply voltage VIN is applied from the battery X2 to the VIN pin via the power switch X3b and the diode D2. In addition, a DC voltage (=battery voltage VB) is applied from the battery X2 to the CRT pin via the power switch X3b and the diode D3.
< LED drive device >
Next, the internal structure of the LED driving device 100 will be described with reference to fig. 1. The LED driving device 100 is formed by integrating a current driver 101, a reference voltage generating section 102, an open mask (open mask) function section 103, an overvoltage mute (overvoltage) section 104, a protection bus function section 105, a CR timer 106, an LED open circuit detecting section 107, an LED short circuit detecting section 108, a reference current setting section 109, an ISET open circuit/short circuit detecting section 110, a control logic section 111, a bypass function section 112, N-channel MOS (metal oxide semiconductor ) field effect transistors N1 and N2, current sources CS1 and CS2, and switches SW1 and SW 2. Although not explicitly shown in the figure, other circuit parts (an under-voltage lock [ UVLO, under voltage locked out ] function part, a thermal shutdown ] function part, and the like) are also integrated in the LED driving device 100.
The current driver 101 performs constant current control of the output current Iout so that the output current Iout flowing to the LED light source 200 coincides with a predetermined target value. Although not explicitly shown in the figure, the current driver 101 may be configured to include, for example, an output transistor provided in a current path through which the output current Iout flows, a sense resistor for converting the output current Iout into a feedback voltage, and an operational amplifier for performing linear driving of the output transistor so that the feedback voltage matches a reference voltage. Further, the target value of the output current Iout may be arbitrarily set according to the reference current Iset.
The reference voltage generation unit 102 generates a predetermined reference voltage VREG (e.g., 5V) from the power supply voltage Vin (e.g., 5.5V to 20V) and outputs the same to each unit of the LED driving device 100.
When the power supply voltage Vin is lower than a predetermined threshold voltage, the open-circuit masking function 103 notifies the control logic 111 of the detection result, masking the detection result of the LED open-circuit detection unit 107. By such an open circuit shielding function, for example, false detection of an open circuit of the LED at the time of rising of the power supply voltage Vin can be eliminated.
When the power supply voltage Vin exceeds a predetermined threshold voltage (for example, 16V), the overvoltage muting unit 104 controls the reference current setting unit 109 so as to decrease the reference current Iset (and thus the output current Iout) according to the difference value (the exceeding amount of Vin) between the two. By such overvoltage muting processing, abnormal heat generation of the LED driving device 100 can be suppressed.
The protection bus function unit 105 shares the abnormality detection results of the plurality of LED driving devices 100 with each other, and reflects the abnormality detection results in the abnormality protection operation of the control logic unit 111. For example, when some abnormality (LED open circuit, LED short circuit, UVLO, temperature abnormality, etc.) is detected in the LED driving device 100, the protection bus function unit 105 outputs an abnormality detection signal to the outside via the PBUS pin. When an abnormality detection signal is externally input via the PBUS pin, the protection bus function unit 105 transfers the abnormality detection signal to the control logic unit 111. By such an operation, for example, if an abnormality is detected in one LED driving device, it is possible to realize a continuous protection operation in which all LED driving devices are stopped.
In the PWM dimming mode (X3 b off) in which the DC voltage is not applied to the CRT pins, the CR timer 106 pulse-drives the PWM dimming signal S1 to the control logic 111 in order to perform PWM dimming of the LED light source 200. For example, the CR timer 106 performs on/off control of the switch SW1 and the transistors N1 and N2 using the PWM dimming signal S1, and periodically switches charge and discharge of the capacitor C3 to drive the terminal voltage of the CRT pin into a triangular waveform, thereby performing pulse driving of the PWM dimming signal S1. Further, the time average value of the output current Iout (and thus the luminance of the LED light source 200) varies according to the duty ratio of the PWM dimming signal S1. The period and the duty ratio of the PWM dimming signal S1 can be arbitrarily set by adjusting the resistance value of the resistor R3 and the capacitance value of the capacitor C3.
On the other hand, the CR timer 106 fixes the logic level of the PWM dimming signal S1 in the DC dimming mode (X3 b on) in which the DC voltage is applied to the CRT pin. At this time, the control logic unit 111 performs constant current control of the output current Iout.
In this way, if the CR timer 106 is incorporated in the LED driving device 100, PWM dimming without a microcomputer can be realized, and thus the cost of the LED light emitting device X1 can be reduced. Further, the CR timer 106 has a function of outputting the PWM signal as the PWM dimming signal S1 to the control logic unit 111 when the PWM signal is externally input to the CRT pin, and thus can cope with PWM dimming using a microcomputer or the like.
The LED open circuit detection unit 107 compares the terminal voltage (=output voltage Vout) of the IOUT pin with a predetermined threshold voltage (for example, vin-0.05V), detects whether or not an open circuit abnormality has occurred in the LED light source 200, and notifies the control logic unit 111 of the detection result.
The LED short circuit detection unit 108 compares the terminal voltage (=output voltage Vout) of the IOUT pin with a predetermined threshold voltage (for example, 0.6V/0.8V), detects whether or not a short circuit abnormality (for example, a ground short circuit) has occurred in the LED light source 200, and notifies the detection result to the control logic unit 111. In the present specification, the term "ground short" refers to a short circuit directed to a ground terminal or a low potential terminal with respect to the ground terminal.
The reference current setting unit 109 generates a reference current Iset for setting a target value of the output current Iout. The reference current Iset may be arbitrarily set by adjusting the resistance value of the resistor R4. The reference current setting unit 109 further has a temperature decay function of adjusting the reference current Iset according to the resistance value of the negative-characteristic thermistor NTC.
The ISET open/short detection unit 110 compares the terminal voltage of the ISET pin with a predetermined threshold voltage to detect whether or not the ISET pin is open/short, and notifies the control logic unit 111 of the detection result.
The control logic unit 111 is a main body that integrally controls the operation of the entire LED driving device 100. For example, the control logic unit 111 has a function of variably controlling the current value of the output current Iout or switching whether the current value of the output current Iout can be output, based on detection results obtained by various abnormality detection units (the overvoltage muting unit 104, the protection bus function unit 105, the LED open circuit detection unit 107, the LED short circuit detection unit 108, and the ISET open circuit/short circuit detection unit 110).
The bypass function unit 112 monitors the monitor voltage Vm (=divided voltage of the power supply voltage Vin) input to the SWCNT pin, and when the power supply voltage Vin decreases (=when the power supply voltage Vin decreases to a voltage value at which the total forward-decreasing voltage vf_total of the LED light source 200 cannot be ensured), bypasses at least one of the plurality of LED chips 201 to 203 (in this figure, the LED chip 203) constituting the LED light source 200, thereby reducing the number of series stages of the LED chips through which the output current Iout flows, and reducing the total forward-decreasing voltage vf_total of the LED light source 200.
For example, by reducing the number of series stages of the LED chips from "3" to "2", the total forward-falling voltage vf_total of the LED light source 200 can be reduced from "3Vf" to "2Vf" (where Vf is the forward-falling voltage of each of the LED chips 201 to 203).
By incorporating such bypass function unit 112, the LED light source 200 can be maintained on even when the power supply voltage Vin decreases. Further, the structure and operation of the bypass function portion 112 will be described in detail later.
Transistors N1 and N2 are connected between the DISC pin and ground, respectively, and are on/off controlled by CR timer 106.
The current source CS1 and the switch SW1 are connected in series between the application terminal of the reference voltage VREG and the CRT pin. Further, the current source CS1 generates a source current (source current) for charging the capacitor C3. As described above, the switch SW1 is turned on/off according to the PWM dimming signal S1 output from the CR timer 106.
The current source CS2 and the switch SW2 are connected in series between the VIN pin and the IOUT pin. The current source CS2 generates a source current (for example, 1 mA) for preventing the malfunction of the LED short-circuit detection unit 108. The switch SW1 is turned on, for example, when the terminal voltage (=output voltage Vout) of the IOUT pin is lower than a predetermined threshold voltage (for example, 0.8V).
< Bypass function portion (first embodiment) >
Fig. 2 is a diagram showing a first embodiment of the bypass function unit 112. The bypass function unit 112 of the present embodiment includes a comparator 112a and a switch 112b (N-channel type MOS field effect transistor in the present embodiment).
The comparator 112a compares the monitor voltage Vm (=divided voltage of the power supply voltage Vin) input to the inverting input terminal (-) with the threshold voltage VthL/VthH (where VthL < VthH) input to the non-inverting input terminal (+) to generate the comparison signal Sa. Further, when Vm > VthH (for example, vthH =2.0v) at the time of rising of the power supply voltage Vin, the comparison signal Sa drops from the high level to the low level. On the other hand, when Vm < VthL (e.g., vthl=1.8v) at the time of the decrease of the power supply voltage Vin, the comparison signal Sa rises from the low level to the high level.
In this way, by using a hysteresis comparator having hysteresis in the threshold voltage VthL/VthH as the comparator 112a, even if noise or the like is superimposed on the monitor voltage Vm, the logic level of the comparison signal Sa is not unnecessarily switched, and thus the operation stability of the bypass function unit 112 can be improved.
In addition, when the power supply voltage Vin is within the input dynamic range of the comparator 112a, the resistors R1 and R2 may be omitted, and the power supply voltage Vin may be directly input to the comparator 112a.
The switch 112b is connected between the SW pin and the ground terminal, and is turned on/off according to the comparison signal Sa, thereby switching whether or not to bypass at least one of the LED chips 201 to 203 (in the example of the present figure, the LED chip 203).
More specifically, when the comparison signal Sa is at a low level, the switch 112b is turned off, and thus the LED chip 203 is in an unbroken state. At this time, the output current IOUT outputted from the IOUT pin flows into the first current path reaching the ground terminal via all the chips of the LED chips 201 to 203.
On the other hand, when the comparison signal Sa is at the high level, the switch 112b is turned on, and thus the LED chip 203 is in a bypassed state. At this time, the output current IOUT outputted from the IOUT pin is guided from the cathode of the LED chip 202 to the SW pin, and flows into the second current path reaching the ground.
Hereinafter, the first output current flowing through the first current path is referred to as IoutA, and the second output current flowing through the second current path is referred to as IoutB. Further, a relationship of iout=iouta+ioutb is established between the output current IOUT output from the IOUT pin and the first and second output currents IoutA and IoutB.
Fig. 3 is a timing chart showing an example of the bypass operation in the first embodiment, and the power supply voltage Vin, the output current Iout, the first output current IoutA, and the second output current IoutB are sequentially drawn from the top.
For example, when the power supply voltage Vin increases, the comparison signal Sa is at a high level during Vin < VthH × { (r1+r2)/R2 } i.e., vm < VthH, and the switch 112b is turned on. As a result, the LED light source 200 is bypassed around the LED chip 203. At this time, the output current Iout does not flow in the first current path via the LED chip 203, but flows in the second current path via the SW pin. Thus, iouta=0, ioutb=iout.
In this way, during the period when the power supply voltage Vin is low, the LED chip 203 is bypassed, the number of series stages of LED chips through which the output current Iout flows is reduced, and the total forward-falling voltage vf_total of the LED light source 200 is reduced, thereby maintaining the LED light source 200 on.
Thereafter, the power supply voltage Vin rises sufficiently, and when Vin > VthH × { (r1+r2)/R2 }, that is, vm > VthH, the comparison signal Sa falls to a low level, and the switch 112b is turned off. As a result, the LED light source 200 is in a state in which the LED chip 203 is not bypassed. At this time, the output current Iout does not flow into the second current path via the SW pin, but flows into the first current path via the LED chip 203. Thus, ioutb=0, iouta=iout.
When the power supply voltage Vin increases in this way, the bypass of the LED chip 203 is released, so that all of the LED chips 201 to 203 emit light, and the LED light source 200 is lighted at the maximum luminance.
Further, once the power supply voltage Vin increases, the comparison signal Sa is maintained at a low level during the period in which Vin > vthl× { (r1+r2)/R2 }, that is, during the period in which Vm > VthL, and the switch 112b is kept off. As a result, the bypass released state of the LED chip 203 is continued, and thus the LED light source 200 is continuously lighted at the maximum brightness.
However, if the power supply voltage Vin further decreases and Vin < vthl× { (r1+r2)/R2 }, that is, vm < VthL, the comparison signal Sa increases to a high level, and the switch 112b is turned on. As a result, the LED chip 203 is bypassed again, and the total forward-falling voltage vf_total of the LED light source 200 decreases, so that the lighting of the LED light source 200 is maintained.
In this way, the bypass function unit 112 compares the power supply voltage Vin with the bypass release voltage VthH × { (r1+r2)/R2 } and the bypass start voltage vthl× { (r1+r2)/R2 } to perform bypass control of the LED chip 203. The bypass release voltage and the bypass start voltage can be arbitrarily set by adjusting the resistance values of the resistors R1 and R2 mounted on the outside of the SWCNT pins.
< Bypass function portion (second embodiment) >
Fig. 4 is a diagram showing a second embodiment of the bypass function unit 112. The bypass function unit 112 of the present embodiment includes operational amplifiers AMP1 to AMP3, N-channel MOS field effect transistors M1 to M3, current mirrors CM1 and CM2, a current control unit CTRL, and resistors Ra to Rd. In the LED driving device 100, an ISINK pin, a SET pin, and a RVIN pin are provided instead of the SW pin and the SWCNT pin of fig. 1. In addition, the ISINK pin is connected to the anode of the LED chip 203 (=the cathode of the LED chip 202). In addition, the SET pin and the RVIN pin are respectively externally provided with resistors RSET and RVIN. The connection relationship between the elements in the LED driving device 100 will be specifically described below.
The non-inverting input terminal (+) of the operational amplifier AMP1 is inputted with a predetermined reference voltage VREF (e.g., a bandgap voltage). The inverting input (-) of the operational amplifier AMP1 is connected to the SET pin and the source and back gate of the transistor M1. The output terminal of the operational amplifier AMP1 is connected to the gate of the transistor M1. The drain of the transistor M1 is connected to the current input of the current mirror CM 1. The current output of the current mirror CM1 is connected to the current input of the current mirror CM 2. The current output of the current mirror CM2 is connected to a first current input (=input of the internal current Ia) of the current control section CTRL.
The resistors Ra and Rb are connected in series between the input terminal of the power supply voltage Vin and the ground terminal. The noninverting input terminal (+) of the operational amplifier AMP2 is connected to a connection node between the resistors Ra and Rb. The inverting input (-) of the operational amplifier AMP2 is connected to the RVIN pin and the source and back gate of the transistor M2. The output terminal of the operational amplifier AMP2 is connected to the gate of the transistor M2. The drain of the transistor M2 is connected to the second current input terminal (=input terminal of the internal current Ib) of the current control section CTRL.
The first terminal of the resistor Rc is connected to the current output terminal (=output terminal of the internal current Ic) of the current control section CTRL. The second terminal of the resistor Rc is connected to the ground terminal. The non-inverting input (+) of the operational amplifier AMP3 is connected to the first end of the resistor Rc. The inverting input (-) of the operational amplifier AMP3 is connected to the first terminal of the resistor Rd and the source and back gate of the transistor M3. The second terminal of resistor Rd is connected to ground. The output terminal of the operational amplifier AMP3 is connected to the gate of the transistor M3. The drain of transistor M3 is connected to the ISINK pin.
In the bypass function unit 112 of the present embodiment, the operational amplifier AMP1 performs gate control of the transistor M1 so that both input terminals thereof are virtually short-circuited. Accordingly, the drain current of the transistor M1 becomes a current value (=vref/RSET) corresponding to the reference voltage VREF and the resistance RSET.
The current mirror CM1 is connected between the application terminal of the internal power supply voltage VREG and the transistor M1, and mirrors the input current (=drain current of the transistor M1) to generate an output current (=source current flowing into the current mirror CM 2).
The current mirror CM2 is connected between the current output terminal of the current mirror CM1 and the ground terminal, and mirrors the input current (=source current flowing from the current mirror CM 1) to generate an output current (=sink current (sink current) drawn from the current control unit CTRL, which corresponds to the internal current Ia).
When the coefficient (=the total mirror ratio of the current mirrors CM1 and CM 2) for Ia setting is α, the current value of the internal current Ia is obtained by ia=α×vref/RSET.
In this way, the operational amplifier AMP1, the transistor M1, the resistor RSET, and the current mirrors CM1 and CM2 function as a first internal current generation unit that generates the internal current Ia of a fixed value.
On the other hand, the operational amplifier AMP2 performs gate control of the transistor M2 so that both input terminals thereof are virtually short-circuited. Therefore, the drain current (=sink current introduced from the current control unit CTRL corresponds to the internal current Ib) of the transistor M2 has a current value (=β×vin/RVIN) corresponding to the power supply voltage Vin and the resistor RVIN. In the formula, β is a coefficient for Ib setting, and may be expressed as a voltage division ratio of the resistors Ra and Rb (=rb/(ra+rb)).
In this way, the operational amplifier AMP2, the transistor M2, the resistor RVIN, and the resistors Ra and Rb function as a second internal current generation unit that generates the internal current Ib having a variable value corresponding to the power supply voltage Vin.
The current control unit CTRL generates the internal current Ic (=ia-Ib) by subtracting the internal current Ib from the internal current Ia.
The operational amplifier AMP3 performs gate control of the transistor M3 so as to virtually short-circuit its two input terminals. Therefore, the drain current (=sink current introduced from the ISINK pin corresponds to the second output current IoutB) of the transistor M3 has a current value (=ic×rc/Rd) corresponding to the internal current Ic and the resistances Rc and Rd.
In this way, the operational amplifier AMP3, the transistor M3, and the resistors Rc and Rd function as a current sink portion that introduces the second output current IoutB corresponding to the internal current Ic from the ISINK pin.
Fig. 5 is a timing chart showing an example of the bypass operation in the second embodiment, and the power supply voltage Vin, the output current Iout, the first output current IoutA, and the second output current IoutB are sequentially drawn from the top as in fig. 3.
For example, when Vin is lower than a predetermined set voltage (vref× (RVIN/RSET) × (α/β)) at the time of rising of the power supply voltage Vin, ia > Ib, ioutB >0. At this time, if the coefficients α and β are set such that IoutB > Iout, the output current Iout entirely flows into the ISINK pin, so iouta=0. That is, the LED light source 200 is in a state in which the LED chip 203 is completely bypassed, and only the LED chips 201 and 202 are turned on (refer to period (1) in the figure).
Thereafter, when the power supply voltage Vin reaches a voltage value (=vref× (RVIN/RSET) × (α/β) - (Rd/Rc) × (RVIN/β) ×iout) of ioutb=iout, the second output current IoutB starts to decrease. Then, as the power supply voltage Vin increases, the second output current IoutB gradually decreases, and the first output current IoutA increases by an amount corresponding to the decrease in a complementary manner (see period (2) in the figure).
Further, when the power supply voltage Vin increases and Vin > vref× (RVIN/RSET) × (α/β), the LED chip 203 is in a state in which the bypass is completely released. At this time, the output current Iout does not flow into the second current path via the ISINK pin, but flows into the first current path via the LED chip 203 in its entirety. Therefore, ioutb=0 and iouta=iout (refer to period (3) in the figure).
In contrast to the above, when Vin < vref× (RVIN/RSET) × (α/β) starts to decrease when the power supply voltage Vin decreases, the first output current IoutA starts to increase by an amount corresponding to the decrease in the complementary manner to the second output current IoutB.
After that, the power supply voltage Vin further decreases, and when vref× (RVIN/RSET) × (α/β) - (Rd/Rc) × (RVIN/β) ×iout is set, the LED chip 203 is restored to the fully bypassed state. Thus, iouta=0, ioutb=iout.
As described above, when controlling whether or not to bypass the LED chip 203 to switch the series number of LED chips through which the output current Iout flows, the bypass function unit 112 according to the second embodiment gradually changes the first output current IoutA (=the output current of the LED chip 203 flowing into the bypass target) that varies complementarily to the second output current IoutB by performing the linear control of the second output current IoutB that is introduced from the cathode of the LED chip 202 to the SW pin. That is, linear cross (linear cross) control of complementarity of the first output current IoutA and the second output current IoutB is performed.
In the bypass function unit 112 according to the present embodiment, when the bypass state of the LED chip 203 is switched, the change in luminance of the LED light source 200 is slower than that of the first embodiment (fig. 2), so that the user does not feel uncomfortable with the eyes.
< LED light emitting device (element addition example) >)
Fig. 6 is a diagram showing an additional element example of the LED light emitting device X1. The LED light emitting device X1 of this configuration example is based on the foregoing fig. 1, and further has resistors R5 to R7. Resistor R5 is connected between the anode of each of diodes D2 and D3 and ground. Resistor R6 is connected between the THD pin and ground. The resistor R7 is connected between the THD pin and the negative characteristic thermistor NTC.
< Bypass function portion (third embodiment) >)
Fig. 7 is a diagram showing a third embodiment of the bypass function unit 112 (and the LED driving device 100 including the bypass function unit 112). The LED driving device 100 of the present embodiment basically has the same structure as that of the first embodiment (fig. 1), but a description of some constituent elements is omitted.
In addition, regarding some of the constituent elements, the respective signs are changed (iout→out, iset→set, sw→isink, swcnt→bpcnt, ioutb→isink, r1→rbp1, r2→rbp2, r4→rset). But the respective functions are not substantially changed.
In addition, a resistor RBP3 is newly arranged between the connection node (=the application terminal of the divided voltage vin_div) between the resistors RBP1 and RBP2 and the BPCNT pin. Specifically, the connection relationship between the resistors RBP1 to RBP3 is described. The first terminal of the resistor RBP1 is connected to the application terminal of the power supply voltage Vin. The second terminal of the resistor RBP1 and the first terminals of the resistors RBP2 and RBP3 are connected to the application terminal of the divided voltage vin_div (=vin× { RBP 2/(rbp1+rbp2) }). The second terminal of the resistor RBP2 is connected to ground. A second terminal of the resistor RBP3 is connected to the BPCNT pin.
The bypass function unit 112 having the new structure will be described below. The bypass function unit 112 of the present embodiment includes an operational amplifier 112A, P channel type MOS field effect transistor 112B, coefficient multiplication units 112C and 112D, a subtraction unit 112E, and a current source 112F.
The inverting input terminal (-) of the operational amplifier 112A is connected to the BPCNT pin (=corresponding to the bypass control terminal). The non-inverting input (+) of the operational amplifier 112A is connected to the application terminal of the threshold voltage VBP. The output of the operational amplifier 112A is connected to the gate of the transistor 112B. The source and back gate of transistor 112B are connected to BPCNT pins. The drain of the transistor 112B is connected to the input terminal of the coefficient multiplying unit 112D.
The operational amplifier 112A and the transistor 112B connected in this way function as a control current generating unit that generates the control current IBPCTL so that the terminal voltage vin_div2 of the BPCTL pin matches the threshold voltage VBP.
In addition, the control current IBPCTL flows from the application terminal of the divided voltage vin_div to the transistor 112B via the resistor RBP 3. Therefore, the terminal voltage vin_div2 is a voltage (=vin_div-IBPCTL ×rbp3) obtained by subtracting the voltage drop amount in the resistor RBP3 corresponding to the control current IBPCTL from the divided voltage vin_div.
The coefficient multiplication unit 112C multiplies the reference current Iset for determining the target value of the output current Iout by a coefficient Ksink (=isink current setting coefficient).
The coefficient multiplication unit 112D multiplies the control current IBPCNT by a coefficient Gsink (=isink current gain).
The subtracting section 112E subtracts the output signal of the coefficient multiplying section 112D from the output signal of the coefficient multiplying section 112C.
The current source 112F generates a sink current ISINK (=corresponding to a branch current of the LED chip 203, which is not a bypass target, of the output current Iout) which is drawn from the cathode of the LED chip 202 to the ISINK pin, from the output signal of the subtracting section 112E.
The set value of the sink current Isink and its maximum value Isink_max, and the control current IBPCNT can be calculated by the following equations (1 a) and (1 b), and equation (1 c), respectively.
[ Number 1]
As is clear from the above equation, the bypass function unit 112 according to the present embodiment can variably control the set value of the sink current Isink according to the control current IBPCTL corresponding to the power supply voltage Vin or the divided voltage vin_div thereof.
In addition, when the bypass function unit 112 is not used, the ISINK pin may be grounded GND, and the BPCNT pin may be resistance-pulled down or grounded GND.
Fig. 8 is a timing chart showing an example of the bypass operation in the third embodiment, and the power supply voltage Vin, the divided voltage vin_div, and the terminal voltage vin_div2, the output current Iout, the control current IBPCNT, the sink current Isink, and the output current IoutA (=iout-Isink) are sequentially drawn from the top.
Before time t1, the power supply voltage Vin does not sufficiently rise, and the terminal voltage vin_div2 (at this time, the same value as the divided voltage vin_div) is lower than the threshold voltage VBP. Therefore, since the output signal of the operational amplifier 112A is attached to the upper limit (=high level potential) of the output dynamic range, the transistor 112B is in the fully off state, and the control current IBPCTL is not flowing at all (IBPCTL =0). As a result, the set value of the sink current Isink becomes its maximum value isink_max (=refer to the formula (1 b) above).
Here, the maximum value isink_max may be set to a value larger than the target value of the output current Iout. According to such a setting, since the output current Iout can be supplied entirely by the sink current Isink, the output current IoutA flowing to the LED chip 203 is maintained at a zero value.
That is, the LED light source 200 is in a state in which the LED chip 203 is completely bypassed, and only the LED chips 201 and 202 are turned on. In this way, by bypassing the LED chip 203 during the period when the power supply voltage Vin is low, the number of series stages of LED chips through which the output current Iout flows can be reduced, and thus the total forward-falling voltage vf_total of the LED light source 200 can be reduced, and the lighting of the LED light source 200 can be maintained.
Then, as the power supply voltage Vin increases, at time t1, if the terminal voltage vin_div2 (=divided voltage vin_div) exceeds the threshold voltage VBP, the output signal of the operational amplifier 112A decreases, and thus, the control current IBPCTL starts to flow into the transistor 112B. As a result, the set value of the sink current Isink gradually decreases from the maximum value isink_max thereof as the control current IBPCNT increases.
However, at the time point of time t1, since the set value of the sink current Isink is still higher than the target value of the output current Iout, the output current Iout is entirely supplied by the sink current Isink. As a result, the output current IoutA flowing to the LED chip 203 remains at a zero value.
Since the control current IBPCTL starts to flow, the terminal voltage vin_div2 is a voltage (=vin_div-IBPCTL ×rbp3) obtained by subtracting the voltage drop in the resistor RBP3 corresponding to the control current IBPCTL from the divided voltage vin_div. After that, the terminal voltage vin_div2 is maintained at a voltage value (or almost the same voltage value) equal to the threshold voltage VBP.
Further, if the power supply voltage Vin rises, the set value of the sink current Isink becomes lower than the target value of the output current Iout at time t2, and the output current Iout cannot be supplied entirely by the sink current Isink. As a result, after time t2, as the power supply voltage Vin increases, the sink current Isink gradually decreases, and the output current IoutA increases by an amount corresponding to the decrease in the sink current.
Then, if the sink current Isink stops flowing at time t3 due to a further increase in the power supply voltage Vin, the output current Iout flows as the output current IoutA entirely, that is, the bypass of the LED chip 203 is completely released.
As described above, in the bypass function unit 112 according to the present embodiment, the complementary linear cross control of the sink current ISINK introduced from the cathode of the LED chip 202 to the ISINK pin and the output current IoutA flowing into the LED chip 203 to be bypassed can be performed as in the second embodiment (fig. 4).
In the bypass function unit 112 of the present embodiment, by appropriately adjusting the resistance values of the external resistors RBP1, RBP2, and RBP3, it is possible to arbitrarily set both the power supply voltage Vin at which the set value of the sink current Isink starts to decrease and the slope at which the set value of the sink current Isink decreases (and thus the power supply voltage Vin at which the sink current Isink stops flowing). Specific examples will be described below.
Fig. 9 is a diagram showing a first setting example (iout=100 mA) of the resistances RBP1, RBP2, and RBP 3. The horizontal axis represents the power supply voltage Vin [ V ], and the vertical axis represents the set value [ mA ] of the sink current Isink. In the following description, VBPstart corresponds to the power supply voltage Vin at which the set value of the sink current Isink starts to decrease. Further, Δvbp [ V ] represents the rising amplitude of the power supply voltage Vin required from the set value of the sink current Isink to zero.
First, as shown in solid line (1), consider the case where VBPstart =6v and avbp=4v are set. In this case, rbp1=46.7kΩ, rbp2=30.0kΩ, rbp3=96.5kΩ may be adjusted, respectively.
Next, as shown by a small broken line (2), consider the case where VBPstart =6v and avbp=1v are set. In this case, rbp1=18.9kΩ, rbp2=10.0kΩ, rbp3=18.8kΩ may be adjusted, respectively.
Next, as shown by a large broken line (3), consider the case where VBPstart =9v and avbp=4v are set. In this case, rbp1=30.6kΩ, rbp2=10.0kΩ, rbp3=64.8kΩ may be adjusted, respectively.
Finally, as shown by the one-dot chain line (4), consider the case where VBPstart =9v and avbp=1v are set. In this case, rbp1=33.9 kΩ, rbp2=10.0 kΩ, rbp3=8.99 kΩ may be adjusted, respectively.
Fig. 10 is a diagram showing a second setting example (iout=600ma) of the resistors RBP1, RBP2, RBP 3. In addition, as in fig. 9 above, the horizontal axis represents the power supply voltage Vin [ V ], and the vertical axis represents the set value [ mA ] of the sink current Isink.
First, as shown in solid line (1), consider the case where VBPstart =6v and avbp=4v are set. In this case, rbp1=15.6kΩ, rbp2=10.0kΩ, rbp3=13.0kΩ may be adjusted, respectively.
Next, as shown by a small broken line (2), consider the case where VBPstart =6v and avbp=1v are set. In this case, rbp1=10.58 kΩ, rbp2=5.6 kΩ, rbp3=0.57 kΩ may be adjusted, respectively.
Next, as shown by a large broken line (3), consider the case where VBPstart =9v and avbp=4v are set. In this case, rbp1=30.6kΩ, rbp2=10.0kΩ, rbp3=4.52kΩ may be adjusted, respectively.
Finally, as shown by the one-dot chain line (4), consider the case where VBPstart =9v and avbp=1v are set. In this case, rbp1=11.18kΩ, rbp2=3.30kΩ, rbp3=0.24kΩ may be adjusted, respectively.
< Bypass function portion (fourth embodiment) >)
Fig. 11 is a diagram showing a fourth embodiment of the bypass function unit 112. The bypass function unit 112 of the present embodiment is configured to embody the third embodiment (fig. 7) and includes, in addition to the operational amplifier 112A and the transistor 112B, the operational amplifier 112G, the current source 112H, N, the channel type MOS field effect transistor 112I, and the resistors RA, RB, and RC as constituent elements corresponding to the coefficient multiplying units 112C and 112D, the subtracting unit 112E, and the current source 112F.
A first terminal of the current source 112H is connected to a power supply terminal. A second terminal of the current source 112H and a first terminal of the resistor RA are connected to a non-inverting input (+) of the operational amplifier 112G. The second terminal of the resistor RA is connected to ground. The inverting input (-) of the operational amplifier 112G is connected to the drain of the transistor 112B and the first end of the resistor RC. The output of the operational amplifier 112G is connected to the gate of the transistor 112I. The drain of transistor 112I is connected to the ISINK pin. The source and back gate of transistor 112I are connected to a first terminal of resistor RB and a second terminal of resistor RC. The second terminal of the resistor RB is connected to the ground terminal.
The current source 112H generates a reference current Iset (or a constant current corresponding thereto) for determining a target value of the output current Iout. In addition, the resistor RA is a current/voltage conversion element for converting the reference current Iset into the reference voltage Vref. In this way, the current source 112H and the resistor RA function as a reference voltage generating unit that generates the reference voltage Vref (=iset×ra) corresponding to the target value of the output current Iout.
The resistor RB is a current/voltage conversion element that converts the sink current Isink into the sense voltage Vs. In this way, the resistor RB functions as a current detection unit that generates the sense voltage Vs (=isink×rb) corresponding to the sink current Isink.
The resistor RC functions as a bias imparting unit that generates and adds the bias voltage Vofs (= IBPCTL ×rc) corresponding to the control current IBPCTL to the sense voltage Vs. In addition, when the offset voltage Vofs' (= IBPCTL ×rb) generated between both ends of the resistor RB according to the control current IBPCTL cannot be ignored, the resistors RB and RC can be understood as the offset imparting unit described above.
The operational amplifier 112G and the transistor 112I function as a sink current generating section that generates a sink current Isink so that the offset sense voltage (vs+vofs) matches the reference voltage Vref.
For example, when the power supply voltage Vin is low and the control current IBPCTL does not flow, the sink current Isink is generated so that the sense voltage Vs to which the bias is not applied coincides with the reference voltage Vref. This state corresponds to a state in which the set value of the sink current Isink is set to its maximum value Isink_max and the output current Iouta does not flow at all, that is, a state in which the LED chip 203 is completely bypassed.
On the other hand, when the power supply voltage Vin rises, the control current IBPCTL starts to flow, the offset voltage Vofs corresponding to the current value is added to the sense voltage Vs, and is feedback-input to the operational amplifier 112G. As a result, the feedback loop reaches equilibrium at less sink current Isink. This state corresponds to a state in which the set value of the sink current Isink is lowered from its maximum value Isink_max, that is, a state in which the complementary linear cross control of the sink current Isink and the output current IoutA is performed.
Finally, if the power supply voltage Vin rises until the offset voltage Vofs corresponding to the control current IBPCTL exceeds the predetermined reference voltage Vref, the sink current Isink no longer flows. This state is a state in which the output current Iout flows as the output current IoutA, that is, a state in which the bypass of the LED chip 203 is completely released.
< Terminal configuration >
Fig. 12 is a diagram showing a terminal arrangement of the LED driving device 100 in fig. 7 and 11. The LED driving device 100 is packaged in VSON [ Very-THIN SMALL Outline No Lead ] package, and as means for establishing electrical connection with the outside of the device, 10 external terminals (VIN pin, BPCNT pin, PBUS pin, CRT pin, DISC pin, THD pin, SET pin, GND pin, ISINK pin, OUT pin) are provided.
The VIN pin (1 pin) is a power supply voltage input terminal. BPCNT pin (2 pin) is a current bypass function setting terminal at power down. The PBUS pin (3 pin) is an abnormal state flag output/output current cut-off control input terminal. The CRT pin (4 pin) and DISC pin (5 pin) are CR timer set terminals, respectively. The THD pin (6 pin) is a temperature decay setting terminal. The SET pin (7 pin) is an output current setting terminal. The GND pin (8 pin) is a ground terminal. The ISINK pin (9 pin) is a current sinking terminal. The OUT pin (10 pin) is a current output terminal.
Further, since BPCNT pin (2 pin) is a resistive voltage division input terminal of the power supply voltage Vin, it is preferable to be disposed adjacent to Vin pin (1 pin).
In addition, since the OUT pin (10 pin) and the ISINK pin (9 pin) are terminals connected to the LED light source 200, they are preferably disposed adjacent to each other. If such a pin configuration is adopted, even if the OUT pin and the ISINK pin are short-circuited, only a part of the LED light source 200 (=the LED chips 201 and 202 connected between OUT-ISINK) is extinguished, so that the LED driving apparatus 100 is not damaged. Further, when the power supply voltage Vin rises, the LED chip 203 at the lowest stage is lighted.
In addition, the ISINK pin (9 pin) is preferably disposed adjacent to the GND pin (8 pin). If such a pin configuration is adopted, even if the ISINK pin and the GND pin are short-circuited, a part of the LED light source 200 (=the LED chips 201 and 202 connected between OUT-ISINK) is lighted.
In addition, in the LED driving device 100, a heat dissipation plate EXP-PAD is provided on the lower surface of the package. In addition, the heat sink EXP-PAD may also be grounded GND.
< Socket type LED Module >
Fig. 13 is a plan view showing a socket-type LED module Y as an example of embodying the LED light emitting device X1 described so far. The socket-type LED module Y of this configuration example is a lighting fixture for a vehicle, for example, and includes: the LED chip comprises a substrate 300, an LED chip 400 (corresponding to the LED chips 201 to 203), a white resin 480, a reflector 600, a terminal 800, various electronic components (LED driving device 100, resistors R1 to R7, capacitors C1 to C3, diodes D1 to D3, negative characteristic thermistor NTC) and a socket 900.
The substrate 300 has a base material and a wiring pattern (see hatched areas in the figure) formed on the base material. The substrate is rectangular in shape and is made of, for example, glass epoxy resin. The wiring pattern is a conductive member laid on the surface of the substrate for mounting the LED chip 400 and various electronic components, and is made of a metal such as Cu or Ag. The LED driving device 100, resistors R1 to R7, capacitors C1 to C3, diodes D1 to D3, and a negative characteristic thermistor NTC are mounted on the upper surface of the substrate 300. Each electronic component is connected to a wiring pattern laid on the upper and lower surfaces of the substrate 300 to constitute a circuit, and is a component for lighting the LED chip 400 in a desired light emission state.
Hereinafter, the arrangement of electronic components (depicted by a thin dotted line frame in the figure) will be described, with the vertical and horizontal directions of the paper surface being defined as the vertical and horizontal directions of the substrate 300, the component arrangement direction parallel to the vertical and horizontal directions of the substrate 300 being defined as the longitudinal direction, and the component arrangement direction parallel to the horizontal direction of the substrate 300 being defined as the lateral direction.
The LED driving device 100 is disposed in the upper left region of the substrate 300 such that the arrangement direction of the pins is transverse.
The resistor R1 is disposed laterally on the upper right side of the LED driving device 100 in the upper center region of the substrate 300. The resistor R2 is disposed laterally on the upper left region of the substrate 300 (on the left side of the resistor R1) on the upper side of the LED driving device 100. The resistor R3 is disposed vertically on the left side of the LED driving device 100 in the upper left region of the substrate 300. The resistor R4 is disposed laterally below the LED driving device 100 in the upper left region of the substrate 300. The resistor R5 is disposed laterally on the right side of the diode D2 in the lower left region of the substrate 300. The resistor R6 is disposed laterally on the left side of the LED driving device 100 in the upper left region of the substrate 300. The resistor R7 is disposed laterally on the lower left side (lower side of the resistor R6) of the LED driving device 100 in the upper left region of the substrate 300. The negative-characteristic thermistor NTC is disposed vertically below the resistor R7 in the left central region of the substrate 300.
The capacitor C1 is disposed in the upper central region of the substrate 300 and is disposed longitudinally on the right side of the LED driving device 100. The capacitor C2 is disposed laterally on the right side of the LED driving device 100 in the upper center region of the substrate 300. The capacitor C3 is disposed vertically above the resistor R6 and to the left of the resistor R3 in the upper left region of the substrate 300.
The diode D1 is disposed longitudinally in the lower right region of the substrate 300. The diode D2 is disposed longitudinally in the lower left region of the substrate 300. The diode D3 is disposed longitudinally on the left side of the negative characteristic thermistor NTC in the left central region of the substrate 300. Further, diode D3 is smaller than diodes D1 and D2.
The types, the number, and the arrangement locations of the electronic components are not limited to the arrangement modes described above.
The reflector 600 is made of, for example, white resin, and is fixed to the central region of the substrate 300 so as to surround the LED chip 400. The reflector 600 is configured to reflect light emitted laterally from the LED chip 400 upward. A reflecting surface 601 is formed on the reflector 600. The reflective surface 601 surrounds the LED chip 400. Although it is difficult to see in fig. 13, the reflection surface 601 is inclined so as to be further away from the substrate 300 in the thickness direction of the substrate 300, and further away from the LED chip 400 in a direction perpendicular to the thickness direction of the substrate 300. That is, the cross section of the reflection surface 601 perpendicular to the thickness direction of the substrate 300 is formed in a tapered shape that increases toward the opening side of the reflector 600.
The LED chip 400 is a light source of the socket type LED module Y, for example, emits red light. In this configuration example, three LED chips 400 are mounted on the substrate 300 so as to be surrounded by the reflector 600. In this figure, three LED chips 400 are arranged at the positions of the vertices of the regular triangle. However, the layout of the LED chips 400 is not limited thereto, and for example, as shown in fig. 14, three LED chips 400 may be arranged in a row in the left-right direction of the substrate 300.
In this configuration example, the case where the LED chip 400 emits red light is described, but the emission color of the LED chip 400 is not limited to this.
The white resin 480 is made of a white resin material that does not transmit light from the LED chip 400, and corresponds to an example of an opaque resin. As can be seen from fig. 13, the white resin 480 surrounds the LED chip 400, and its outer circumference reaches the reflecting surface 601 of the reflector 600. Therefore, in fig. 13, the area extending from the LED chip 400 to the reflection surface 601 in the up-down direction and the left-right direction in the drawing is filled with white resin 480.
The terminal 800 is a metal wire serving as an electrode, and is provided so as to penetrate the substrate 300 and the socket 900. One end of the terminal 800 is connected to a part of the wiring pattern, for example, by solder.
The socket 900 is a component for mounting the substrate 300 on, for example, an automobile. The socket 900 is formed of, for example, synthetic resin, and is formed by, for example, injection molding. The socket 900 includes a mounting portion 910 for mounting the board 300 and a mounting portion for mounting on an automobile or the like. The mounting portion 910 has a cylindrical shape with one surface opened, and the substrate 300 is mounted on the inner bottom surface of the mounting portion 910. A heat sink 950 made of a circular plate made of aluminum is fixed to the inner bottom surface of the mounting portion 910. The lower surface of the substrate 300 is bonded to the upper surface of the heat sink 950 by an adhesive, and is thereby mounted on the mounting portion 910 of the socket 900.
Next, the operation of the socket type LED module Y will be described.
The white resin 480 covers the entire annular region from the support substrate of the LED chip 400 to the reflection surface 601 of the reflector 600. Therefore, the area surrounded by the reflective surface 601 is covered with the white resin 480, except for the area occupied by the LED chip 400. This allows light from the semiconductor layer of the LED chip 400 to be reflected more. This is suitable for increasing the brightness of the socket type LED module Y. In addition, it is not necessary to additionally perform a process of appropriately reflecting light on the region surrounded by the reflection surface 601 of the substrate 300.
By providing the reflector 600 having the reflecting surface 601, the directly upper direction of the socket type LED module Y can be illuminated more brightly.
In the socket-type LED module Y, the LED chips 400 serving as the light sources are arranged in 1 position in a concentrated manner. Therefore, when the power supply voltage Vin decreases, even if one of the LED chips 400 is bypassed by the bypass function unit 112, only the luminance of one LED chip decreases, and the entire socket-type LED module Y is not turned off.
In particular, in-vehicle lamps, regulations that require maintenance of an on state even when a power supply voltage Vin decreases are required to be complied with. In view of this, it can be said that the LED driving apparatus 100 having the bypass function portion 112 is very suitable as a driving body of the in-vehicle lamp.
In addition, in the case where the socket type LED module Y is preferentially made to emit light uniformly, for example, in fig. 14, it is preferable to set the LED chip disposed in the center portion as a bypass target. On the other hand, if priority is given to ease of laying the printed wiring, for example, in fig. 14, the LED chip disposed at the end portion may be set as a bypass target.
< Use >
As shown in fig. 15 and 16, the LED driving device 100 described above can be incorporated into a light emitting device such as a headlight (including a high beam, a low beam, a small beam, a fog light, and the like) X11, a daytime running light (DRL daylight running lamps) X12, a taillight (including a small beam, a reversing light, and the like, and a parking light X14, a turn light X15, and the like of a vehicle X10, for example.
The LED driving device 100 may be provided as a module (for example, a socket-type LED module Y in fig. 13 to 14, an LED headlight module Y10 in fig. 17, an LED turn signal module Y20 in fig. 18, and an LED backlight module Y30 in fig. 19) together with the LED light source 200 to be driven, or may be provided as an IC unit independently of the LED light source 200.
< Other modifications >
In the above embodiment, the structure using the light emitting diode as the light emitting element has been described as an example, but the structure of the present invention is not limited to this, and for example, an organic EL (electroluminescence) element may be used as the light emitting element.
In the above-described embodiment, the case where the current driver 101 is of the current source type (=the output form in which the output current Iout flows from the power source terminal to the anode of the LED light source 200) has been described as an example, but the configuration of the LED driving device 100 is not limited to this, and the bypass function unit 112 is effectively introduced when the current driver 101 is of the current sink type (=the output form in which the output current Iout is introduced from the cathode of the LED light source 200 to the ground terminal).
In the above embodiment, the LED chip 203 arranged on the lowest potential side among the three LED chips 201 to 203 constituting the LED light source 200 is the bypass target, but the other LED chip 201 or 202 may be the bypass target.
Further, a stepwise bypass control may be performed, for example, by preparing a plurality of threshold voltages Vth1 and Vth2 (Vth 1< Vth 2) to be compared with the power supply voltage Vin in advance, by-passing both the LED chips 202 and 203 when Vin < Vth1, by-passing only the LED chip 203 when Vth1< Vin < Vth2, and by-passing both the LED chips 202 and 203 when Vin > Vth 2.
As described above, various technical features disclosed in the present specification can be variously modified in addition to the above-described embodiments without departing from the gist of the technical creation. For example, the mutual replacement of the bipolar transistor and the MOS field effect transistor and the inversion of the logic levels of various signals are arbitrarily performed. That is, the above-described embodiments are to be considered in all respects as illustrative and not restrictive, and the technical scope of the present invention is not limited to the above-described embodiments, but is to be construed as including all modifications within the meaning and scope equivalent to the scope of the claims.
Industrial applicability
The invention disclosed in the present specification can be used, for example, in a light-emitting element driving device for a vehicle, to maintain the lighting of a light-emitting element light source even if the power supply voltage is reduced.
Description of the reference numerals
100 LED driving means (light emitting element driving means);
101. A current driver;
102. a reference voltage generation unit;
103. An open-circuit shielding function section;
104. An overvoltage muting unit;
105. A protection bus function unit;
106 A CR timer;
107 An LED open circuit detection unit;
108 An LED short circuit detection unit;
109. A reference current setting unit;
110 An ISET open circuit/short circuit detection unit;
111. A control logic section;
112. a bypass function section;
112a comparators;
112b switch;
112A operational amplifier;
112B P channel type MOS field effect transistor;
112C, 112D coefficient multiplication sections;
112E subtracting section;
112F current source;
a 112G operational amplifier;
112H current source;
112I N channel type MOS field effect transistor;
200 LED light source (light emitting element light source);
201. 202, 203 LED chips (light-emitting elements);
300. A substrate;
400 An LED chip;
480. White resin;
600. a reflector;
601. A reflecting surface;
800. A terminal;
900. A socket;
910. a carrying part;
950. A heat dissipation plate;
R1-R4, R5-R7 resistance;
C1-C3 capacitors;
D1-D3 diodes;
An NTC negative characteristic thermistor;
N1, N2N channel type MOS field effect transistor;
CS1, CS2 current sources;
SW1, SW2 switches;
AMP1 to AMP3 operational amplifiers;
CM1, CM2 current mirrors;
A CTRL current control unit;
M1-M3N channel MOS field effect transistors;
Ra-Rd, RA, RB, RC, RSET, RVIN, RBP resistance 1-3 resistance;
an X vehicle;
an X1 LED light emitting device;
An X2 battery;
x3a, X3b power switches;
X10 vehicle;
X11 head lamps;
X12 daytime running lights;
X13 taillight;
x14 stop light;
X15 turn signals;
Y socket type LED module;
Y10 LED headlight module;
y20 LED turn light module;
Y30 LED back light module.
Claims (15)
1. A light emitting element driving device includes:
a current driver that generates an output current flowing into a light emitting element light source connected between an application terminal of a power supply voltage and a ground terminal; and
A bypass function unit for bypassing at least one of the plurality of light emitting elements constituting the light emitting element light source when the power supply voltage decreases, reducing the number of series stages of the light emitting elements through which the output current flows,
When the series number of the light emitting elements through which the output current flows is switched, the bypass function section gradually changes the output current flowing into the light emitting element to be bypassed,
The bypass function unit variably controls a set value of a branch current of the output current, which does not pass through the light emitting element to be bypassed, based on a control current corresponding to the power supply voltage or a divided voltage of the power supply voltage,
The bypass function section further includes:
A first coefficient multiplication unit that multiplies a reference current for determining a target value of the output current by a first coefficient;
a second coefficient multiplication unit that multiplies the control current by a second coefficient;
A subtracting section that subtracts an output signal of the second coefficient multiplying section from an output signal of the first coefficient multiplying section; and
And a current source that generates the branch current from an output signal of the subtracting section.
2. The light-emitting element driving device according to claim 1, wherein,
The control current starts to flow when the power supply voltage or the divided voltage becomes higher than a predetermined threshold voltage.
3. The light-emitting element driving device according to claim 1, wherein,
The set value of the branch current decreases as the control current increases from a maximum value larger than the target value of the output current.
4. The light-emitting element driving device according to claim 1, wherein,
The bypass function section further includes:
And a control current generation unit that generates the control current so that a terminal voltage of a bypass control terminal through which the control current flows matches a predetermined threshold voltage.
5. The light-emitting element driving device according to claim 4, wherein,
The terminal voltage is obtained by subtracting a voltage drop corresponding to the control current from the power supply voltage or the divided voltage.
6. The light-emitting element driving device according to claim 1, wherein,
The bypass function section further includes:
a reference voltage generation unit that generates a reference voltage corresponding to a target value of the output current;
a current detection unit that generates a sense voltage corresponding to the branch current;
A bias applying unit that applies a bias voltage corresponding to the control current to the sense voltage; and
And a branch current generation unit that generates the branch current so that the sense voltage to which the bias voltage is applied coincides with the reference voltage.
7. The light-emitting element driving device according to claim 4, wherein,
The light-emitting element driving device is externally provided with a first resistor, a second resistor and a third resistor, wherein the first end of the first resistor is connected with the application end of the power supply voltage, the second end of the first resistor is connected with the application end of the divided voltage, the second end of the second resistor is connected with the grounding end, and the first end of the third resistor is connected with the application end of the divided voltage, and the second end of the third resistor is connected with the bypass control terminal.
8. The light-emitting element driving device according to claim 4, wherein,
The bypass control terminal is adjacent to the input terminal of the power supply voltage.
9. The light-emitting element driving device according to claim 1, wherein,
The external terminal through which the branch current flows is adjacent to at least one of an output terminal and a ground terminal of the output current.
10. The light-emitting element driving device according to any one of claims 1 to 9, wherein,
The current driver is a current source type.
11. The light-emitting element driving device according to any one of claims 1 to 9, wherein,
The current driver is current sinking.
12. A light emitting device includes:
a light-emitting element light source in which a plurality of light-emitting elements are connected in series; and
A light emitting element driving device according to any one of claims 1 to 11 that drives the light emitting element light source.
13. The light emitting device of claim 12, wherein,
The light emitting element is a light emitting diode or an organic EL element.
14. The light emitting device of claim 12, wherein,
The light-emitting device further includes:
A substrate on which wiring patterns for mounting the light-emitting element light source and the light-emitting element driving device are laid; and
And a socket for mounting the substrate.
15. A vehicle having the light emitting device of any one of claims 12 to 14.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2018-061200 | 2018-03-28 | ||
| JP2018061200 | 2018-03-28 | ||
| PCT/JP2018/039634 WO2019187279A1 (en) | 2018-03-28 | 2018-10-25 | Light-emitting element drive device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN111902951A CN111902951A (en) | 2020-11-06 |
| CN111902951B true CN111902951B (en) | 2024-05-10 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN201880091696.XA Active CN111902951B (en) | 2018-03-28 | 2018-10-25 | Light-emitting element driving device |
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| Country | Link |
|---|---|
| JP (1) | JP7018124B2 (en) |
| CN (1) | CN111902951B (en) |
| DE (1) | DE112018007350T5 (en) |
| WO (1) | WO2019187279A1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR102192393B1 (en) * | 2019-12-09 | 2020-12-17 | 이경연 | Led system for vehicle lighting having high efficiency and high reliability |
| JPWO2022202670A1 (en) | 2021-03-26 | 2022-09-29 |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001325824A (en) * | 2000-05-17 | 2001-11-22 | Kyocera Corp | Led drive circuit for backlight at portable terminal |
| JP2010015883A (en) * | 2008-07-04 | 2010-01-21 | Sumida Corporation | Lighting circuit |
| JP2011119738A (en) * | 2009-12-02 | 2011-06-16 | Aussmak Optoelectronic Corp | Light-emitting apparatus |
| JP2014197656A (en) * | 2013-03-04 | 2014-10-16 | シチズンホールディングス株式会社 | LED drive circuit |
| CN106663724A (en) * | 2014-07-30 | 2017-05-10 | Lg 伊诺特有限公司 | Light emitting module |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63307784A (en) * | 1987-06-09 | 1988-12-15 | Fujitsu Ltd | Drive circuit for led |
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2018
- 2018-10-25 CN CN201880091696.XA patent/CN111902951B/en active Active
- 2018-10-25 WO PCT/JP2018/039634 patent/WO2019187279A1/en active Application Filing
- 2018-10-25 DE DE112018007350.5T patent/DE112018007350T5/en active Pending
- 2018-10-25 JP JP2020509589A patent/JP7018124B2/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001325824A (en) * | 2000-05-17 | 2001-11-22 | Kyocera Corp | Led drive circuit for backlight at portable terminal |
| JP2010015883A (en) * | 2008-07-04 | 2010-01-21 | Sumida Corporation | Lighting circuit |
| JP2011119738A (en) * | 2009-12-02 | 2011-06-16 | Aussmak Optoelectronic Corp | Light-emitting apparatus |
| JP2014197656A (en) * | 2013-03-04 | 2014-10-16 | シチズンホールディングス株式会社 | LED drive circuit |
| CN106663724A (en) * | 2014-07-30 | 2017-05-10 | Lg 伊诺特有限公司 | Light emitting module |
Also Published As
| Publication number | Publication date |
|---|---|
| WO2019187279A1 (en) | 2019-10-03 |
| CN111902951A (en) | 2020-11-06 |
| JPWO2019187279A1 (en) | 2021-02-12 |
| JP7018124B2 (en) | 2022-02-09 |
| DE112018007350T5 (en) | 2020-12-03 |
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