Lamp fitting, lighting circuit, and semiconductor device

Abstract

To provide a lamp fitting capable of preventing blackout of a light emitting element at a modulation of an input voltage VIN.SOLUTION: The present invention provides a lamp fitting 1 having a plurality of light emitting elements 21a, 21b, and 21c that is serially connected, and a lighting circuit 3 that supplies an output current flowing in each of the light emitting elements 21a, 21b, and 21c in responce to an input voltage VIN. The lighting circuit 3 comprises: a current driver 4 that generates an output current IOUT flowing in each of the light emitting elements 21a, 21b, and 21c; bypass current drivers 7b and 7c that flow bypass currents IBYPASSb and IBYPASSc that bypass at least one of the light emitting elements 21a, 21b, and 21c. Any one of the current driver 4 and the bypass current drivers 7b and 7c is constructed by a source type current circuit that discharges the output current IOUT, and the other one is constructed by a sink type current circuit that absorbs the output current IOUT.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a lamp and a lighting circuit, and more particularly to a lamp and a lighting circuit in which a plurality of light-emitting elements are connected in series. [Background technology]

[0002] Lamps using light-emitting elements such as LEDs (Light Emitting Diodes) are used, for example, as vehicle lamps. When a single light-emitting chip does not provide enough light, multiple light-emitting elements are connected in series. In lamps in which multiple light-emitting elements are connected in series, when the input voltage of the lighting circuit that lights the light-emitting elements drops and falls below the forward drop voltage (VF voltage) of the light-emitting elements, the light-emitting elements are turned off. In the case of vehicle lamps, the input voltage of the lighting circuit drops when the idling stop function is activated, etc.

[0003] Therefore, a lighting device has been proposed that controls the number of light-emitting elements to be turned on by reducing the input voltage (see, for example, Patent Document 1). Patent Document 1 controls a bypass switch connected in parallel to at least one light-emitting element based on the difference between the input voltage and the forward voltage of the light-emitting element connected in series. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-197711 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the VF voltage of a light-emitting element varies greatly during manufacturing and also varies with environmental changes such as temperature. Therefore, the conventional technology has not been able to completely solve the problem of the light-emitting element going out due to a drop in input voltage.

[0006] The present invention has been made in consideration of such problems, and its purpose is to provide a lighting fixture, a lighting circuit, and a semiconductor device that can prevent the light-emitting element from turning off when the input voltage fluctuates, even if the VF of the light-emitting element fluctuates due to manufacturing variations or temperature environment. [Means for solving the problem]

[0007] In order to achieve the above object, the lamp and the lighting circuit according to the present invention are configured as follows. The lighting fixture of the present invention is a lighting fixture comprising a plurality of light-emitting elements connected in series, and a lighting circuit that receives an input voltage and supplies an output current flowing to the light-emitting elements, wherein the lighting circuit comprises a current driver that generates the output current flowing to the light-emitting elements, and a bypass current driver that flows a bypass current that bypasses at least one of the light-emitting elements, and one of the current driver and the bypass current driver is composed of a sink-type current circuit that sinks the output current, and the other is composed of a source-type current circuit that sinks the output current. The lighting fixture of the present invention is a lighting fixture comprising a plurality of light-emitting elements connected in series, and a lighting circuit that receives an input voltage and supplies an output current flowing to the light-emitting elements, wherein the lighting circuit comprises a current driver that generates the output current flowing to the light-emitting elements, and a bypass current driver that flows a bypass current that bypasses at least one of the light-emitting elements, and the bypass current driver changes the bypass current based on the voltage difference between both ends of the current driver. The lighting circuit of the present invention is a lighting circuit that receives an input voltage and supplies an output current flowing to a plurality of light-emitting elements connected in series, and is characterized in that it comprises a current driver that generates the output current flowing to the light-emitting elements, and a bypass current driver that flows a bypass current that bypasses at least one of the light-emitting elements, and the bypass current driver changes the bypass current based on the voltage difference between both ends of the current driver. The lighting circuit of the present invention receives an input voltage and supplies an output current flowing to a plurality of light-emitting elements connected in series, and is characterized in that it comprises a current driver that generates the output current flowing to the light-emitting elements, and a bypass current driver that supplies a bypass current that bypasses at least one of the light-emitting elements, and one of the current driver and the bypass current driver is composed of a sink-type current circuit that sinks the output current, and the other is composed of a source-type current circuit that sinks the output current. Effect of the Invention

[0008] The lamp, lighting circuit, and semiconductor device of the present invention have the effect of preventing the light-emitting element from going out when the input voltage fluctuates, even if the VF of the light-emitting element fluctuates due to manufacturing variations or temperature environment. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram showing a configuration of a first embodiment of a lighting fixture according to the present invention; [Diagram 2] 2 is a diagram illustrating a configuration of a current driver illustrated in FIG. 1. [Diagram 3] 2 is a diagram showing currents flowing through the elements of the lighting fixture shown in FIG. 1. [Figure 4] FIG. 4 is a diagram showing the configuration of a second embodiment of a lighting device according to the present invention. [Diagram 5] 5 is a diagram showing currents flowing through the elements of the lighting fixture shown in FIG. 4. [Figure 6] FIG. 11 is a diagram showing the configuration of a third embodiment of a lighting device according to the present invention. [Figure 7] FIG. 13 is a diagram showing the configuration of a fourth embodiment of a lighting device according to the present invention. [Figure 8] FIG. 13 is a diagram showing the configuration of a fifth embodiment of a lighting device according to the present invention. [Figure 9] FIG. 13 is a diagram showing the configuration of a sixth embodiment of a lighting device according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[0011] (First embodiment) Referring to FIG. 1, a lamp 1 according to the first embodiment includes a light-emitting unit 2 and a lighting circuit 3 that causes the light-emitting unit 2 to emit light.

[0012] The light-emitting unit 2 includes three light-emitting elements 21a, 21b, and 21c connected in series. The light-emitting elements 21a, 21b, and 21c can be configured with LEDs (Light Emitting Diodes).

[0013] The lighting circuit 3 is connected to the input voltage V IN and an output current I OUT and the current setting terminal T2 which sets the output current I OUT The output terminal T4 has an output terminal T3 that outputs the voltage Vcc, a bypass input terminal T4b, and a bypass input terminal T4c.

[0014] The output terminal T3 is connected to the anode of the light-emitting element 21a. The bypass input terminal T4b is connected to the connection point between the cathode of the light-emitting element 21a and the anode of the light-emitting element 21b. The bypass input terminal T4c is connected to the connection point between the cathode of the light-emitting element 21b and the anode of the light-emitting element 21c.

[0015] The lighting circuit 3 receives an input voltage Vin input to an input terminal T1 and outputs an output current I OUT The output terminal T3 outputs an output current I OUT is supplied to the light emitting unit 2 and becomes a current flowing through the light emitting elements 21a, 21b, and 21c.

[0016] The lighting circuit 3 receives an output current I OUT The lighting circuit 3 includes an output current setting circuit 5 that sets the value of in accordance with the resistance value of an external resistor R1 connected to a current setting terminal T2. The lighting circuit 3 can be configured as a semiconductor device integrated on a substrate.

[0017] The current driver 4 is a source-type (discharge-type) current circuit, and is configured, for example, as a source-type constant current circuit as shown in Fig. 2(a). The current driver 4 shown in Fig. 2(a) includes a reference voltage source 41, a resistor R2, an operational amplifier 42, and a P-type MOSFET 43.

[0018] The reference voltage source 41 is a reference voltage V ref The reference voltage source 41 has a positive electrode connected to the input terminal T1 and a negative electrode connected to the non-inverting input terminal of the operational amplifier 42. The resistor R2 and the P-type MOSFET 43 are connected in series between the input terminal T1 and the output terminal T3, and the connection point between the resistor R2 and the P-type MOSFET 43 is connected to the inverting input terminal of the operational amplifier 42.

[0019] The output current I from the current driver 4 OUT I OUT =V ref / R2, and since resistor R2 is a fixed value, the reference voltage V ref Therefore, the output current I OUT is set by the output current setting circuit 5 (external resistor R1).

[0020] The lighting circuit 3 includes a bypass circuit 6. The bypass circuit 6 prevents the output current I OUT and reducing the number of series stages of the light-emitting elements 21a, 21b, and 21c in the light-emitting unit 2. The bypass circuit 6 includes a bypass current driver 7b connected in parallel to the light-emitting element 21b, a bypass current driver 7c connected in parallel to the light-emitting element 21c, and a bypass control circuit 61.

[0021] The bypass current driver 7b is a sink type (absorption type) current circuit, and is configured, for example, by a sink type constant current circuit as shown in Fig. 2(b). The bypass current driver 7b shown in Fig. 2(b) includes a resistor R3, an operational amplifier 72b, and an N-type MOSFET 73b.

[0022] The operational amplifier 72b receives the reference voltage V ref is input to the non-inverting input terminal. The N-type MOSFET 73b is connected in series with a resistor R3, and the connection point between the N-type MOSFET 73b and the resistor R3 is connected to the inverting input terminal of the operational amplifier 72b.

[0023] The bypass current I absorbed by the bypass current driver 7b BYPASSb I BYPASSb =V ref / R3, and since resistor R3 is a fixed value, the reference voltage V ref Therefore, the bypass current driver 7b controls the bypass current I BYPASSb is drawn from the bypass input terminal T4b, thereby bypassing the light emitting element 21b and the light emitting element 21c.

[0024] The bypass current driver 7c is a sink-type current circuit like the bypass current driver 7b, and is configured, for example, with a sink-type constant current circuit as shown in Fig. 2(c). The bypass current driver 7c shown in Fig. 2(c) includes a resistor R4, an operational amplifier 72c, and an N-type MOSFET 73c.

[0025] The operational amplifier 72c receives the reference voltage V ref is input to the non-inverting input terminal. The N-type MOSFET 73c is connected in series with a resistor R4, and the connection point between the N-type MOSFET 73c and the resistor R4 is connected to the inverting input terminal of the operational amplifier 72c.

[0026] The bypass current I drawn by the bypass current driver 7c BYPASSc I BYPASSc =V ref / R4, and since resistor R4 is a fixed value, the reference voltage V ref Therefore, the bypass current driver 7c controls the bypass current I BYPASScis drawn from the bypass input terminal T4c, thereby bypassing the light emitting element 21c.

[0027] The bypass control circuit 61 controls the voltage across the current driver 4 (input voltage V IN , output voltage V OUT ) based on the bypass current I BYPASSb and bypass current I BYPASSc Change the value.

[0028] The operation of the bypass circuit 6 will now be described in detail with reference to FIG. Figure 3(a) shows the input voltage V IN The LED current I flows through the light emitting element 21a in response to LEDa Figure 3(b) shows the input voltage V IN The LED current I flows through the light emitting element 21a in response to LEDb Figure 3(c) shows the input voltage V IN The bypass current I drawn by the bypass current driver 7b according to BYPASSb Fig. 3(d) shows the input voltage V IN The LED current I flows through the light emitting element 21c according to LEDc Fig. 3(e) shows the input voltage V IN The bypass current I drawn by the bypass current driver 7c corresponds to BYPASSc Shows.

[0029] Referring to Figure 3, the input voltage V IN V 6 If so, the output current I OUT flows through all the light emitting elements 21a, 21b, and 21c of the light emitting unit 2, and all three lights are turned on. OUT When the forward voltages of the light-emitting elements 21a, 21b, and 21c are VFa, VFb, and VFc, respectively, all three lights (light-emitting elements 21a, 21b, and 21c) have an output current I OUT Therefore, the three lights are turned on. When the three lights are turned on, the output voltage V OUT V 6 = VFa + VFb + VFc.

[0030] Input voltage V IN V 6 If the input voltage V IN - Output voltage V OUT ) bypass current I BYPASSc As a result, the LED current I LEDc is the output current I OUT - Bypass current I BYPASSc It becomes.

[0031] The bypass control circuit 61 controls the bypass current I BYPASSc As a result, the smaller the voltage difference between both ends of the current driver 4, the larger the LED current I LEDc Since the bypass current I BYPASSc The maximum value of the output current I OUT The bypass current I BYPASSc becomes larger, and I BYPASSc =I OUT When the input voltage V IN V 5 If the input voltage V IN V 6 ~V 5 The LED current I flows through the light emitting element 21c. LEDc The input voltage V IN V 5 The LED current I LEDc When becomes zero, the output current I OUT is the bypass current I BYPASSc The light-emitting element 21c is bypassed, and the two lights (light-emitting elements 21a and 21b) output a current I OUT The bypass current driver 7c is turned on by the input voltage V IN V 5 Current control starts at this point, and V 5 This is the current control start level of the bypass current driver 7c. In the two-lamp lighting state, the input voltage V IN V 5 ~V 4During this time, the output voltage V OUT V 4 = VFa + VFb.

[0032] Input voltage V IN V 4 If the input voltage V IN - Output voltage V OUT ) depending on the bypass current I BYPASSb As a result, the LED current I LEDb is the output current I OUT - Bypass current I BYPASSb In addition, the bypass current driver 7c is a current driver 4 having a voltage difference between both ends (input voltage VIN - Output voltage V OUT ) LED current I LEDb The bypass current I BYPASSc As a result, the light emitting element 21c receives the input voltage V IN V 4 Even if the voltage drops below this level, the light will remain off.

[0033] The bypass control circuit 61 controls the bypass current I BYPASSb As a result, the smaller the voltage difference between both ends of the current driver 4, the larger the LED current I LEDb Since the bypass current I BYPASSb The maximum value of the output current I OUT The bypass current I BYPASSb becomes larger, and I BYPASSb =I OUT When the input voltage V IN V 3 If the input voltage V IN V 4 ~V 3 The LED current I flows through the light emitting element 21b. LEDb The input voltage V IN V 3 The LED current I LEDb When becomes zero, the output current I OUT is the bypass current IBYPASSb The light emitting elements 21b and 21c are bypassed, and one light (light emitting element 21a) outputs an output current I OUT The bypass current driver 7b is turned on when the input voltage V IN V 3 Current control starts at this point, and V 3 is the current control start level of the bypass current driver 7b. In the one-lamp lighting state, the input voltage V IN V 3 ~V 2 During this time, the output voltage V OUT V 2 =VFa.

[0034] The number of light emitting elements connected in series in the light emitting unit 2 may be two, or may be four or more. The number of light emitting elements bypassed by the bypass circuit 6 depends on the assumed input voltage V IN For example, the expected input voltage V IN The range of V 4 In the above cases, the bypass current driver 7b can be omitted, and the current control can be performed only by the bypass current driver 7c.

[0035] (Second embodiment) Referring to FIG. 4, the lighting circuit 3a of the lamp 1a of the second embodiment includes a bypass output terminal T5b, and the bypass current I BYPASSb is output from the bypass output terminal T5b to the connection point between the light emitting element 21b and the light emitting element 21b. That is, the bypass current driver 7b is connected in parallel only to the light emitting element 21b.

[0036] As shown in FIG. 5, the bypass control circuit 61 of the lighting circuit 3a is IN V 4 Even if the bypass current I BYPASSb The output current I OUT As a result, the light emitting element 21c is maintained at the input voltage V IN V 4 Even if the voltage drops below this level, the light will remain off.

[0037] (Third embodiment) 6, in the light-emitting unit 2a of the lamp 1b of the third embodiment, a resistor R5 is connected between the bypass input terminal T4b and the anode of the light-emitting element 21b, and a resistor R6 is connected between the bypass input terminal T4c and the anode of the light-emitting element 21b. That is, the bypass current driver 7b is connected to the connection point between the cathode of the light-emitting element 21a and the resistor R5, and the bypass current driver 7c is connected to the connection point between the light-emitting element 21b and the resistor R6.

[0038] (Fourth embodiment) 7, the lighting circuit 3b of the lamp 1c of the fourth embodiment includes a light-emitting unit failure detection circuit 8. The light-emitting unit failure detection circuit 8 monitors the voltages of the output terminal T3, the bypass input terminal T4b, and the bypass input terminal T4c, and determines that an abnormality has occurred when the voltage becomes higher than a judgment potential (number of light-emitting element stages × VF voltage), and outputs an output current I OUT Stops the output of.

[0039] (Fifth embodiment) Referring to FIG. 8, the lighting circuit 3c of the lighting fixture 1d of the fifth embodiment has an input voltage V IN and an output current I OUT and the current setting terminal T2 which sets the output current I OUT The output terminal T5 includes an output terminal T3 that outputs a current, a bypass output terminal T5a, and an output current input terminal T6.

[0040] The output terminal T3 is connected to the anode of the light emitting element 21a. The bypass output terminal T5a is connected to the connection point between the cathode of the light emitting element 21a and the anode of the light emitting element 21b. The output current input terminal T6 is connected to the cathode of the light emitting element 21c.

[0041] The lighting circuit 3c outputs an output current I OUT The current driver 4' outputs an output current I from an output current input terminal T6. OUT It is composed of a sink-type current circuit that absorbs

[0042] The lighting circuit 3c includes a bypass circuit 6'. The bypass circuit 6' prevents the output current I OUT The bypass circuit 6′ has a bypass function of reducing the number of series stages of the light emitting elements 21a, 21b, and 21c in the light emitting section 2. The bypass circuit 6′ includes a bypass current driver 7a connected in parallel with the light emitting element 21a. The bypass current driver 7a outputs an output current I OUT It consists of a source-type current circuit that outputs

[0043] The bypass current driver 7a performs the same current control as the bypass current driver 7c of the first embodiment. IN V 4 If the voltage difference between both ends of the current driver 4′ (output voltage V OUT -ground potential) depending on the bypass current I BYPASSa As a result, the LED current I LEDa is the output current I OUT - Bypass current I BYPASSa It becomes.

[0044] (Sixth embodiment) 9, the lighting circuit 3d of the lamp 1e according to the sixth embodiment includes a bypass switch circuit 9. The bypass switch circuit 9 controls a target element to be bypassed by the bypass current driver 7b by switching the input voltage V IN In response to the signal, the light emitting elements 21b and 21c and the light emitting element 21b are switched in. By providing the bypass switch circuit 9, the lighting circuit 3d can save the power of the bypass current driver 7c in the second embodiment.

[0045] As described above, this embodiment includes a plurality of light emitting elements 21a, 21b, and 21c connected in series, and an input voltage V IN and a lighting circuit 3 for supplying an output current I flowing to the light-emitting elements 21a, 21b, and 21c. OUTand a bypass current I BYPASSb , I BYPASSc and bypass current drivers 7b, 7c for supplying an output current I OUT The other is a source-type current circuit that outputs an output current I OUT It is composed of a sink type current circuit that absorbs With this configuration, even if the VF of the light emitting elements 21a, 21b, and 21c varies due to manufacturing variations or temperature environments, the input voltage V IN This can prevent the light emitting element from going out when the voltage fluctuates.

[0046] In addition, in this embodiment, a plurality of light emitting elements 21a, 21b, and 21c are connected in series, and an input voltage V IN and a lighting circuit 3 for supplying an output current I flowing to the light-emitting elements 21a, 21b, and 21c. OUT and a bypass current I BYPASSb , I BYPASSc The bypass current drivers 7b and 7c are provided to pass a voltage difference between both ends of the current driver 4 (input voltage V IN - Output voltage V OUT ) based on the bypass current I BYPASSb , I BYPASSc Change the value. This configuration allows the luminous intensity of the light-emitting elements 21b and 21c to be smoothly changed during bypassing by the bypass current drivers 7b and 7c.

[0047] Furthermore, in this embodiment, the lighting circuit 3 includes a plurality of bypass current drivers 7b, 7c, each of which has a current control start level set to a different value. This configuration allows the number of light emitting elements 21a, 21b, and 21c that emit light to be controlled in stages.

[0048] Furthermore, in the sixth embodiment, the lighting circuit 3d includes a bypass switch circuit 9 that switches the target element bypassed by the bypass current driver 7b between the light-emitting elements 21b and 21c, and the light-emitting element 21c. This configuration allows a plurality of bypass paths to be formed by one bypass current driver 7b.

[0049] Furthermore, the third embodiment includes a resistor R5 connected in series between the light emitting elements 21a and 21b (a resistor R6 connected in series between the light emitting elements 21b and 21c).

[0050] Furthermore, the fourth embodiment includes a light-emitting unit failure detection circuit 8 (failure detection circuit) that detects an abnormality in the light-emitting elements 21a, 21b, and 21c based on the voltages of the output terminal T3, the bypass input terminal T4b, and the bypass input terminal T4c, which are the input terminals or output terminals of the current driver 4 and the bypass current drivers 7b and 7c. When the light-emitting unit failure detection circuit 8 detects an abnormality in the light-emitting elements 21a, 21b, and 21c, it detects an output current I OUT The supply of is stopped. With this configuration, a malfunction of the light-emitting unit 2 can be easily detected.

[0051] It is clear that the present invention is not limited to the above-described embodiments, and each embodiment can be appropriately modified within the scope of the technical concept of the present invention. Furthermore, the number, position, shape, etc. of the above-described components are not limited to the above-described embodiments, and the number, position, shape, etc. can be set to be suitable for implementing the present invention. The same components are denoted by the same reference numerals in each drawing. [Explanation of symbols]

[0052] 1, 1a, 1b, 1c, 1d, 1e light fixtures 2, 2a Light emitting part 3, 3a, 3b, 3c, 3d lighting circuit 4, 4' Current Driver 5 Output current setting circuit 6, 6', 6a Bypass circuit 7a, 7b, 7c Bypass Current Drivers 8. Light-emitting unit failure detection circuit 9. Bypass Switch Circuit 21a, 21b, 21c Light-emitting element

Claims

1. A lighting device comprising a plurality of light-emitting elements connected in series, and a lighting circuit that receives an input voltage and supplies an output current flowing through the light-emitting elements, The lighting circuit includes: a current driver for generating the output current flowing through the light emitting element; a bypass current driver that supplies a bypass current that bypasses at least one of the light emitting elements; A lighting fixture, wherein one of the current driver and the bypass current driver is composed of a sink type current circuit that sinks the output current, and the other is composed of a source type current circuit that sinks the output current.

2. A lighting device comprising a plurality of light-emitting elements connected in series, and a lighting circuit that receives an input voltage and supplies an output current flowing through the light-emitting elements, The lighting circuit includes: a current driver for generating the output current flowing through the light emitting element; a bypass current driver that supplies a bypass current that bypasses at least one of the light emitting elements; The lamp, wherein the bypass current driver varies the bypass current based on a voltage difference between both ends of the current driver.

3. The lighting circuit includes:

3. The lamp according to claim 1, further comprising a plurality of the bypass current drivers, each of which has a current control start level set to a different value.

4. The lighting circuit includes:

3. The lamp according to claim 1, further comprising a bypass switch circuit for switching the light emitting element to be bypassed by the bypass current driver.

5. 3. The lamp according to claim 1, further comprising a resistor connected in series between the light emitting elements.

6. a fault detection circuit for detecting an abnormality of the light-emitting element based on a voltage of an input terminal or an output terminal of the current driver and the bypass current driver; 3. The lamp according to claim 1, wherein the failure detection circuit stops the supply of the output current by the current driver when the failure detection circuit detects an abnormality in the light emitting element.

7. A lighting circuit that receives an input voltage and supplies an output current flowing through a plurality of light-emitting elements connected in series, a current driver for generating the output current flowing through the light emitting element; a bypass current driver that supplies a bypass current that bypasses at least one of the light emitting elements; The lighting circuit according to claim 1, wherein the bypass current driver changes the bypass current based on a voltage difference between both ends of the current driver.

8. A lighting circuit that receives an input voltage and supplies an output current flowing through a plurality of light-emitting elements connected in series, a current driver for generating the output current flowing through the light emitting element; a bypass current driver that supplies a bypass current that bypasses at least one of the light emitting elements; A lighting circuit characterized in that one of the current driver and the bypass current driver is composed of a sink type current circuit that sinks the output current, and the other is composed of a source type current circuit that sinks the output current.

9. 9. A semiconductor device comprising the lighting circuit according to claim 7 or 8 integrated on a substrate.

Images