Lighting device and motor vehicle

Abstract

The invention provides a lighting device and a motor vehicle. The lighting device comprises a constant current source circuit, a current balancing circuit and a light-emitting assembly. Wherein the constant current source circuit comprises an output positive electrode and an output negative electrode, and the constant current source circuit is used for outputting an output current between the output positive electrode and the output negative electrode; the light-emitting component comprises N light-emitting branches, N is an integer greater than or equal to 2, a first end of each light-emitting branch is electrically connected with the output positive electrode through the current balancing circuit, and a second end of each light-emitting branch is electrically connected with the output negative electrode; and the current balancing circuit is used for receiving and balancing the output current and providing balanced driving current for the N light-emitting branches.

Description

Technical Field

[0001] The present application relates to the field of electronic technology, and more specifically, to a lighting device and a motor vehicle including the lighting device. Background Art

[0002] In the field of lighting technology, light emitting element strings are widely used. Multiple light emitting element strings can be connected in parallel at the output end of a driving circuit. In order to achieve uniform brightness of each light emitting element string, the current flowing through each light emitting element string needs to be the same. However, due to various reasons, the parameters of each light emitting element string are not completely consistent, resulting in an unbalanced current in each light emitting element string connected in parallel, making the brightness of each light emitting element string uneven. Summary of the invention

[0003] An object of the present application is to overcome at least one of the problems and drawbacks in the prior art.

[0004] A first aspect of the present application provides a lighting device, the lighting device comprising a constant current source circuit, a current balancing circuit and a light-emitting component;

[0005] Wherein, the constant current source circuit comprises an output positive electrode and an output negative electrode, and the constant current source circuit is used to output an output current between the output positive electrode and the output negative electrode;

[0006] The light-emitting component includes N light-emitting branches, where N is an integer greater than or equal to 2, a first end of each light-emitting branch is electrically connected to the output positive electrode through the current balancing circuit, and a second end of each light-emitting branch is electrically connected to the output negative electrode;

[0007] The current balancing circuit is used to receive and balance the output current and provide balanced driving current for the N light-emitting branches.

[0008] In some embodiments, when the light-emitting component works normally, the difference between the driving currents of the N light-emitting branches is less than 1 mA.

[0009] In some embodiments, each of the light-emitting branches includes a plurality of light-emitting elements. In each of the light-emitting branches, the plurality of light-emitting elements are connected in series between the first end and the second end of the corresponding light-emitting branch. When any of the light-emitting elements is short-circuited, the difference in current of the N light-emitting branches is less than 1 mA.

[0010] In some embodiments, the number of the light-emitting elements in each of the light-emitting branches is the same, and the model of each of the light-emitting elements in the N light-emitting branches is the same. When the driving current flowing through the N light-emitting branches is balanced, the brightness of each of the light-emitting elements is consistent.

[0011] In some embodiments, the constant current source circuit includes a current source, the current source is electrically connected between the output positive electrode and the output negative electrode, and the current source is used to provide the output current;

[0012] The current source includes a DC working mode and / or a PWM working mode. In the DC working mode, the constant current source circuit is used to output a constant DC current. In the PWM working mode, the constant current source circuit is used to output a constant PWM current.

[0013] In some embodiments, the constant current source circuit further includes an output overvoltage protection circuit, and the output overvoltage protection circuit is electrically connected between the output positive electrode and the output negative electrode;

[0014] When an open circuit fault occurs in any of the light-emitting branches, the driving current of other light-emitting branches that have not experienced an open circuit fault becomes smaller through the adjustment of the current balancing circuit, the output voltage of the constant current source circuit increases, and the output overvoltage protection circuit clamps the output voltage of the constant current source circuit to a saturation voltage.

[0015] In some embodiments, when the output voltage of the constant current source circuit is constant at the saturation voltage within a preset time, the lighting device turns on the overvoltage protection function and turns off the constant current source circuit, so that the N light-emitting branches all stop emitting light, thereby realizing the OFAF function.

[0016] In some embodiments, the overvoltage protection circuit includes a voltage source and a first diode connected in series, the voltage of the voltage source is equal to the saturation voltage,

[0017] The positive electrode of the first diode is electrically connected to the output positive electrode, the negative electrode of the first diode is electrically connected to the positive electrode of the voltage source, and the negative electrode of the voltage source is electrically connected to the output negative electrode; or, the positive electrode of the voltage source (Vs) is electrically connected to the output positive electrode (Vo+), the negative electrode of the voltage source (Vs) is electrically connected to the positive electrode of the first diode (D1), and the negative electrode of the first diode (D1) is electrically connected to the output negative electrode (GND).

[0018] In some embodiments, the current balancing circuit includes N balancing branches, each of the balancing branches includes a first end, a second end and a third end, the first ends of the N balancing branches are electrically connected to the output positive electrode, the second ends of the N balancing branches are electrically connected to the first ends of the N light-emitting branches in a one-to-one correspondence, and the third ends of the N balancing branches are electrically connected together.

[0019] In some embodiments, each of the balancing branches includes a balanced PNP transistor, and the balanced PNP transistors of the N balancing branches are the same;

[0020] In each of the balanced branches, the emitter of the balanced PNP transistor is electrically connected to the first end of the corresponding balanced branch, the collector of the balanced PNP transistor is electrically connected to the second end of the corresponding balanced branch, and the base of the balanced PNP transistor is electrically connected to the third end of the corresponding balanced branch.

[0021] In some embodiments, each of the balancing branches further comprises a bias resistor, and the bias resistors of the N balancing branches are the same;

[0022] In each of the balanced branches, the bias resistor is electrically connected between the first end of the corresponding balanced branch and the emitter of the balanced PNP transistor.

[0023] In some embodiments, the current balancing circuit includes a reference branch, wherein the reference branch is used to provide a bias current for the balanced PNP transistor and limit the collector current of the balanced PNP transistor within a preset range.

[0024] In some embodiments, the reference branch includes a first end and a second end, the first end of the reference branch is electrically connected to the third ends of the N balancing branches, and the second end of the reference branch is electrically connected to the output cathode.

[0025] In some embodiments, the reference branch includes a reference PNP transistor, a second diode, a third diode, a first reference resistor, and a second reference resistor;

[0026] Among them, the anode of the second diode is electrically connected to the first end of the reference branch, the cathode of the second diode is electrically connected to the anode of the third diode, the cathode of the third diode is electrically connected to the base of the reference PNP transistor, the emitter of the reference PNP transistor is electrically connected to the first end of the reference branch through the first reference resistor, the collector of the reference PNP transistor is electrically connected to the second end of the reference branch, and the base of the reference PNP transistor is electrically connected to the second end of the reference branch through the second reference resistor.

[0027] A second aspect of the present application provides a motor vehicle, which includes a lighting device as provided in the first aspect and the above-mentioned embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A circuit diagram of a lighting device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0029] The following is a detailed description of the embodiments of the present application in conjunction with the accompanying drawings. It should be understood that the embodiments of the present application are mainly intended to illustrate possible implementation methods of the technical solution of the present application and should not be construed as limiting the technical solution of the present application. In this specification, identical or similar components are indicated by identical or similar figure numerals. Electrical connection / connection refers to the existence of an electrical connection relationship between two elements / nodes, which can be a direct electrical connection or an indirect electrical connection through other elements, such as an indirect electrical connection through a resistor, a connecting wire or other electronic components.

[0030] Figure 1 This is a circuit diagram of a lighting device provided in an embodiment of the present application. Figure 1 As shown, an embodiment of the present application provides a lighting device 100, which includes a constant current source circuit 10, a current balancing circuit 20 and a light-emitting component 30. The constant current source circuit 10 includes an output positive electrode Vo+ and an output negative electrode GND, and the output negative electrode is, for example, a ground terminal. The constant current source circuit 10 is used to output an output current Io in a loop between the output positive electrode Vo+ and the output negative electrode GND.

[0031] The light emitting assembly 30 is used to emit light, and the light emitting assembly 30 includes N light emitting branches, where N is an integer greater than or equal to 2. Figure 1 As shown, the light-emitting component 30 includes 3 (N=3) light-emitting branches, which are respectively recorded as the first light-emitting branch 31, the second light-emitting branch 32 and the third light-emitting branch 33. In other embodiments, the number of light-emitting branches can also be 2, 4 or any other number, and the present application does not limit this. The first end of each light-emitting branch is electrically connected to the output positive pole Vo+ through the current balancing circuit 20. Specifically, the first end 31a of the first light-emitting branch 31 is electrically connected to the output positive pole Vo+ through the current balancing circuit 20, the first end 32a of the second light-emitting branch 32 is electrically connected to the output positive pole Vo+ through the current balancing circuit 20, and the first end 33a of the third light-emitting branch 33 is electrically connected to the output positive pole Vo+ through the current balancing circuit 20. The second end of each light-emitting branch is electrically connected to the output negative pole GND. Specifically, the second end 31b of the first light-emitting branch 31 is electrically connected to the output cathode GND, the second end 32b of the second light-emitting branch 32 is electrically connected to the output cathode GND, and the second end 33b of the third light-emitting branch 33 is electrically connected to the output cathode GND.

[0032] The current balancing circuit 20 is used to receive and balance the output current Io, and provide balanced driving currents for the N light-emitting branches. The current balancing circuit 20 provides a first driving current I1 for the first light-emitting branch 31, a second driving current I2 for the second light-emitting branch 32, and a third driving current I3 for the third light-emitting branch 33.

[0033] In the embodiment of the present application, the current balancing circuit 20 is electrically connected between the constant current source circuit 10 and the light emitting component 30, so that the current balancing circuit 20 can adjust the received output current Io into N balanced driving currents, and provide the N balanced driving currents to the corresponding N light emitting branches, so that the N light emitting branches emit uniform and consistent light. This avoids inconsistent driving currents caused by inconsistent parameters of each light emitting branch, and thus avoids uneven brightness of each light emitting branch.

[0034] When the light-emitting component 30 works normally, the current balancing circuit 20 can provide balanced driving currents for the N light-emitting branches. Theoretically, the driving currents of the N light-emitting branches are the same at this time. However, considering some interference factors, the driving currents of the N light-emitting branches may have a slight difference. As long as the difference is within a reasonable error range, they can also be considered balanced. It is defined here that as long as the difference between the driving currents of the N light-emitting branches is less than 1mA, the driving currents of the N light-emitting branches are considered to be the same or almost the same, and the driving currents of the N light-emitting branches are balanced. For example, when the light-emitting component 30 operates normally, the current balancing circuit 20 provides the same or almost the same driving current to the first light-emitting branch 31, the second light-emitting branch 32 and the third light-emitting branch 33 respectively. At this time, |I1-I2|<1mA, |I1-I3|<1mA, |I2-I3|<1mA, that is, the difference between the first driving current I1, the second driving current I2 and the third driving current I3 is equal to 0 or close to 0, and the driving currents of the three light-emitting branches are balanced.

[0035] In some embodiments, each light-emitting branch includes a plurality of light-emitting elements, and the light-emitting elements may be, for example, LEDs. In other embodiments, the light-emitting elements may also be other types of elements, as long as they can emit light and achieve the corresponding lighting effect. In each light-emitting branch, a plurality of light-emitting elements are connected in series between the first end and the second end of the corresponding light-emitting branch. For example, the first light-emitting branch 31 includes 8 LEDs, which are respectively denoted as D11, D12, D13, D14, D15, D16, D17, and D18. In the first light-emitting branch 31, the 8 light-emitting elements D11, D12, D13, D14, D15, D16, D17, and D18 are connected in series between the first end 31a and the second end 31b of the corresponding first light-emitting branch 31. The second light-emitting branch 32 also includes 8 LEDs, which are respectively denoted as D21, D22, D23, D24, D25, D26, D27, and D28. In the second light-emitting branch 32, the 8 light-emitting elements D21, D22, D23, D24, D25, D26, D27, and D28 are connected in series between the first end 32a and the second end 32b of the corresponding second light-emitting branch 32. The third light-emitting branch 33 also includes 8 LEDs, which are respectively denoted as D31, D32, D33, D34, D35, D36, D37, and D38. In the third light-emitting branch 33, the 8 light-emitting elements D31, D32, D33, D34, D35, D36, D37, and D38 are connected in series between the first end 33a and the second end 33b of the corresponding third light-emitting branch 33.

[0036] When any light-emitting element is short-circuited, the current difference of the N light-emitting branches is still less than 1 mA. Assuming that the light-emitting element D38 in the third light-emitting branch 33 is short-circuited, the driving currents on the N light-emitting branches are still balanced due to the regulation of the current balancing circuit 20. Even if an individual light-emitting element is short-circuited, the N light-emitting branches can still provide a uniform lighting effect.

[0037] Preferably, the number of light-emitting elements in each light-emitting branch is the same, and the model of each light-emitting element in the N light-emitting branches is the same. When the driving current flowing through the N light-emitting branches is balanced, the brightness of each light-emitting element is consistent. Figure 1 As shown, the first light-emitting branch 31, the second light-emitting branch 32 and the third light-emitting branch 33 all include 8 identical LEDs, so that the lighting effects of each light-emitting branch can be the same. However, in other embodiments, the number of light-emitting elements of each light-emitting branch can also be different from each other, and the number of light-emitting elements of each light-emitting branch can be any number, which is not limited in the present application.

[0038] The basic working principle of the constant current source circuit 10 is described in detail below.

[0039] In some embodiments, the constant current source circuit 10 includes a current source Is, the current source Is is electrically connected between the output positive pole Vo+ and the output negative pole GND, and the current source Is is used to provide an output current Io. The current source Is may include at least one of a DC working mode and a PWM working mode. In the DC working mode, the constant current source circuit 10 is used to output a constant DC current. In the PWM working mode, the constant current source circuit 10 is used to output a constant PWM current. In addition, the constant current source circuit 10 may also include an output capacitor Co, which is connected in parallel with the current source Is, and the output capacitor Co is electrically connected between the output positive pole Vo+ and the output negative pole GND, and is used to filter the output current Io.

[0040] Preferably, the constant current source circuit 10 further includes an output overvoltage protection circuit 11 , and the output overvoltage protection circuit 11 is electrically connected between the output positive electrode Vo+ and the output negative electrode GND.

[0041] When an open circuit fault occurs in any light-emitting branch, the driving current of other light-emitting branches that have not experienced open circuit faults becomes smaller through the adjustment of the current balancing circuit 20, the output voltage of the constant current source circuit 10 increases, and the output overvoltage protection circuit 11 clamps the output voltage of the constant current source circuit 10 to the saturation voltage.

[0042] For example, assuming that an open circuit fault occurs in the third light-emitting branch 33, the driving current I3 of the third light-emitting branch 33 becomes 0. Through the regulation of the current balancing circuit 20, the driving current I1 of the first light-emitting branch 31 and the driving current I2 of the second light-emitting branch 32 become smaller. In this dynamic process, the constant current source circuit 10 will continuously increase the output voltage to maintain a constant output current Io. When the output voltage increases to the saturation voltage, due to the protection of the output overvoltage protection circuit 11, the output overvoltage protection circuit 11 will clamp the output voltage of the constant current source circuit 10 to the saturation voltage, so that the output voltage no longer continues to increase.

[0043] When an open circuit fault occurs in the light-emitting branch, this embodiment triggers the overvoltage protection circuit 11 inside the constant current source circuit 10 through the current balancing circuit 20 to play a protective role, so that the entire lighting device 100 does not need to be equipped with additional open circuit fault detection and protection circuits, thereby saving the software and hardware costs of the lighting device.

[0044] In some embodiments, when the output voltage of the constant current source circuit 10 is constant at a saturation voltage within a preset time, for example, the output voltage Vo is maintained at a saturation voltage for several hundred milliseconds, it can be determined that the lighting device 100 has failed at this time, and the lighting device 100 will turn on the overvoltage protection function, which can be specifically embodied by turning off the constant current source circuit 10 so that it no longer outputs the output current Io, thereby causing the driving currents on the N light-emitting branches to become 0, and the N light-emitting branches all stop emitting light, thereby realizing the OFAF (one failall fail) function. It is worth noting that in some embodiments, the lighting device 100 can be used as a headlight for a motor vehicle. The OFAF function is a prescribed requirement in motor vehicle lighting, that is, when an open circuit fault occurs in a light-emitting element, all light-emitting elements need to be turned off.

[0045] In some embodiments, the overvoltage protection circuit 11 includes a voltage source Vs and a first diode D1 connected in series, the voltage of the voltage source Vs is equal to the saturation voltage, wherein the positive electrode of the first diode D1 is electrically connected to the output positive electrode Vo+, the negative electrode of the first diode D1 is electrically connected to the positive electrode of the voltage source Vs, and the negative electrode of the voltage source Vs is electrically connected to the output negative electrode GND. The first diode D1 is reversely connected in series to the positive electrode of the voltage source Vs, so that the maximum output voltage of the constant current source circuit 10 is equal to the voltage of the voltage source Vs. In other embodiments, the positions of the first diode D1 and the voltage source Vs can be interchanged, specifically, the positive electrode of the voltage source Vs is electrically connected to the output positive electrode Vo+, the negative electrode of the voltage source Vs is electrically connected to the positive electrode of the first diode D1, and the negative electrode of the first diode D1 is electrically connected to the output negative electrode GND. In other embodiments, the overvoltage protection circuit can also be in other forms.

[0046] The basic working principle of the current balancing circuit 20 is described in detail below.

[0047] In some embodiments, the current balancing circuit 20 can balance the driving currents on the N light-emitting branches. Figure 1 A circuit architecture of the current balancing circuit 20 is provided, but the present application is not limited thereto. In other embodiments, the current balancing circuit 20 may also be transformed into other forms as long as it can be used to balance the driving current.

[0048] like Figure 1 As shown, the current balancing circuit 20 includes three balancing branches, which are respectively denoted as a first balancing branch 21, a second balancing branch 22 and a third balancing branch 23. It is worth noting that the number of balancing branches is not limited to 3, and can also be any other number, as long as the number of balancing branches and the number of light-emitting branches are the same N, where N is an integer greater than 2.

[0049] Each balancing branch includes a first end, a second end and a third end. The first ends of the N balancing branches are electrically connected to the output positive electrode Vo+, the second ends of the N balancing branches are electrically connected to the first ends of the N light-emitting branches in a one-to-one correspondence, and the third ends of the N balancing branches are electrically connected together. Specifically, the first balancing branch 21 includes a first end 21a, a second end 21b and a third end 21c, the second balancing branch 22 includes a first end 22a, a second end 22b and a third end 22c, and the third balancing branch 23 includes a first end 23a, a second end 23b and a third end 23c. The first ends 21a, 22a, 23a of the three balancing branches 21, 22, 23 are electrically connected to the output positive electrode Vo+. The second ends 21b, 22b, 23b of the three balancing branches 21, 22, 23 are electrically connected to the first ends 31a, 32a, 33a of the three light-emitting branches 31, 32, 33 in a one-to-one correspondence. That is, the second end 21b of the first balancing branch 21 is electrically connected to the first end 31a of the first light-emitting branch 31, the second end 22b of the second balancing branch 22 is electrically connected to the first end 32a of the second light-emitting branch 32, and the second end 23b of the third balancing branch 23 is electrically connected to the first end 33a of the third light-emitting branch 33. The third ends 21c, 22c, and 23c of the three balancing branches 21, 22, and 23 are electrically connected together.

[0050] In some embodiments, each balanced branch includes a balanced PNP transistor, and the balanced PNP transistors of the N balanced branches are the same. In each balanced branch, the emitter of the balanced PNP transistor is electrically connected to the first end of the corresponding balanced branch, the collector of the balanced PNP transistor is electrically connected to the second end of the corresponding balanced branch, and the base of the balanced PNP transistor is electrically connected to the third end of the corresponding balanced branch. Figure 1As shown, the first balanced branch 21 includes a first balanced PNP transistor Q1, the second balanced branch 22 includes a second balanced PNP transistor Q2, and the third balanced branch 23 includes a third balanced PNP transistor Q3. In the first balanced branch 21, the emitter of the first balanced PNP transistor Q1 is electrically connected to the first end 21a of the corresponding first balanced branch 21, the collector of the first balanced PNP transistor Q1 is electrically connected to the second end 21b of the first balanced branch 21, and the base of the first balanced PNP transistor Q1 is electrically connected to the third end 21c of the first balanced branch 21. In the second balanced branch 22, the emitter of the second balanced PNP transistor Q2 is electrically connected to the first end 22a of the corresponding second balanced branch 22, the collector of the second balanced PNP transistor Q2 is electrically connected to the second end 22b of the second balanced branch 22, and the base of the second balanced PNP transistor Q2 is electrically connected to the third end 22c of the second balanced branch 22. In the third balanced branch 23, the emitter of the third balanced PNP transistor Q3 is electrically connected to the first end 23a of the corresponding third balanced branch 23, the collector of the third balanced PNP transistor Q3 is electrically connected to the second end 23b of the third balanced branch 23, and the base of the third balanced PNP transistor Q3 is electrically connected to the third end 23c of the third balanced branch 23.

[0051] In addition, each balanced branch includes a capacitor electrically connected between the emitter and base of the corresponding balanced PNP transistor for filtering. For example, the first balanced branch 21 includes a first capacitor C1, which is electrically connected between the emitter and base of the first balanced PNP transistor Q1. The second balanced branch 22 includes a second capacitor C2, which is electrically connected between the emitter and base of the second balanced PNP transistor Q2. The third balanced branch 23 includes a third capacitor C3, which is electrically connected between the emitter and base of the third balanced PNP transistor Q3.

[0052] In some embodiments, each balancing branch may further include a bias resistor, and the bias resistors of the N balancing branches are the same; in each balancing branch, the bias resistor is electrically connected between the first end of the corresponding balancing branch and the emitter of the balancing PNP transistor. The N bias resistors play a role in assisting in balancing the driving currents of the N light-emitting branches, ensuring that the driving currents of the N light-emitting branches are the same or almost the same. Figure 1As shown, the first balanced branch 21 includes a first bias resistor R1, the second balanced branch 22 includes a second bias resistor R2, and the third balanced branch 23 includes a third bias resistor R3. In the first balanced branch 21, the first bias resistor R1 is electrically connected between the first end 21a of the corresponding first balanced branch 21 and the emitter of the first balanced PNP transistor Q1. In the second balanced branch 22, the second bias resistor R2 is electrically connected between the first end 22a of the corresponding second balanced branch 22 and the emitter of the second balanced PNP transistor Q2. In the third balanced branch 23, the third bias resistor R3 is electrically connected between the first end 23a of the corresponding third balanced branch 23 and the emitter of the third balanced PNP transistor Q3.

[0053] Since the three balanced PNP transistors are transistors of the same model, they have the same amplification factor β, the same conduction voltage drop and the same other parameters. When the total voltages of the three light-emitting branches are the same or almost the same, the first balanced PNP transistor Q1, the second balanced PNP transistor Q2 and the third balanced PNP transistor Q3 all work in the saturation region. In combination with the same bias resistors R1, R2 and R3, the collector currents of the three balanced PNP transistors Q1, Q2 and Q3 are balanced, because the driving current of each light-emitting branch is equal to the collector current of the balanced PNP transistor of the corresponding connected balanced branch, that is, the driving currents I1, I2 and I3 on ​​the three light-emitting branches 31, 32 and 33 are balanced, that is, I1, I2 and I3 are exactly the same or almost the same within the error range.

[0054] exist Figure 1In the illustrated embodiment, when any light-emitting element is short-circuited, for example, assuming that the light-emitting element D38 on the third light-emitting branch 33 is short-circuited, the total voltage of the third light-emitting branch 33 will be less than the total voltage of the first light-emitting branch 31 and the total voltage of the second light-emitting branch 32. At this time, the third balanced PNP transistor Q3 will raise its voltage drop to compensate for the voltage of the lost light-emitting element D38, and the first balanced PNP transistor Q1, the second balanced PNP transistor Q2 and the third balanced PNP transistor Q3 will change from working in the saturation region to working in the amplification region. Since the base of the first balanced PNP transistor Q1, the base of the second balanced PNP transistor Q2 and the base of the third balanced PNP transistor Q3 are electrically connected together, the base voltages of the three balanced PNP transistors are the same, which is recorded as the reference voltage Vr. Since the conduction voltage drop between the emitter and base of the three balanced PNP transistors Q1, Q2, and Q3 is the same, for example, 0.7V; therefore, the emitter voltage of the three balanced PNP transistors Q1, Q2, and Q3 is the same, which is the base voltage plus 0.7V. This makes the base currents of the three balanced PNP transistors Q1, Q2, and Q3 the same, specifically Ib1=Ib2=Ib3=1 / 3*Ir, where Ir is the reference current flowing into the first end 200a of the reference branch 200. Since the driving currents of the three light-emitting branches 31, 32, and 33 are equal to the collector currents of the three balanced PNP transistors Q1, Q2, and Q3, that is, I1=β*Ib1, I2=β*Ib2, and I3=β*Ib3. Therefore, the driving currents of the three light-emitting branches 31, 32, and 33 are the same, that is, I1=I2=I3. When the number of light-emitting branches is N, where N is an integer greater than or equal to 2, the same principle applies. The current difference of the N light-emitting branches is less than 1 mA, so that current balancing is achieved through the current balancing circuit 20.

[0055] When an open circuit fault occurs in any light-emitting element, for example, assuming that the light-emitting element D38 on the third light-emitting branch 33 is open-circuited, the third light-emitting branch 33 is open-circuited, and the driving current I3 of the third light-emitting branch 33 becomes 0. The saturation state or amplification state of the third balanced PNP transistor Q3 is broken, and the third balanced PNP transistor Q3 will become a diode mode. At this time, the base current of the third balanced PNP transistor Q3 is equal to the emitter current, then Ib3 is approximately equal to Ir, and Ib3 is much larger than Ib2 and Ib1. The first balanced PNP transistor Q1 and the second balanced PNP transistor Q2 are transformed from the saturation state or amplification state to the cut-off state, and at this time, the sum of the collector currents of the three balanced PNP transistors is much smaller than the output current Io of the constant current source circuit 10. The constant current source circuit 10 continuously raises the output voltage Vo to maintain a constant output current Io until the output voltage Vo reaches the saturation voltage, thereby triggering the overvoltage protection function of the lighting device 100 to turn off the constant current source circuit 10.

[0056] In some embodiments, the current balancing circuit 20 further includes a reference branch 200, which is used to provide bias current for the balanced PNP transistors Q1, Q2, and Q3, and to limit the collector current of the balanced PNP transistors Q1, Q2, and Q3 within a preset range. In particular, when an open circuit fault occurs in a light-emitting branch, a transient large current may occur in the collector of the PNP transistor in other light-emitting branches that do not have an open circuit fault. The reference branch 200 limits it within a preset range to ensure that the PNP transistor operates in a safe working area to avoid breakdown.

[0057] like Figure 1 As shown, the reference branch 200 includes a first end 200a and a second end 200b. The first end 200a of the reference branch 200 is electrically connected to the third ends 21c, 22c, and 23c of the three balancing branches, and the second end 200b of the reference branch 200 is electrically connected to the output negative electrode GND.

[0058] Specifically, the reference branch 200 includes a reference PNP transistor Qr, a second diode D2, a third diode D3, a first reference resistor Rr1, and a second reference resistor Rr2. The second diode D2 and the third diode D3 are connected in series, the anode of the second diode D2 is electrically connected to the first end 200a of the reference branch 200, the cathode of the second diode D2 is electrically connected to the anode of the third diode D3, the cathode of the third diode D3 is electrically connected to the base of the reference PNP transistor Qr, the emitter of the reference PNP transistor Qr is electrically connected to the first end 200a of the reference branch 200 through the first reference resistor Rr1, the collector of the reference PNP transistor Qr is electrically connected to the second end 200b of the reference branch 200, and the base of the reference PNP transistor Qr is electrically connected to the second end 200b of the reference branch 200 through the second reference resistor Rr2. In addition, the reference branch 200 also includes a reference capacitor Cr, which is connected in parallel with the second diode D2 and the third diode D3 connected in series for filtering. At this time, the reference current Ir is approximately equal to the voltage drop 0.7V on the second diode D2 divided by the resistance value of the resistor Rr1.

[0059] An embodiment of the present application further provides a motor vehicle, which includes a lighting device, and the lighting device may be the lighting device described in any of the above embodiments.

[0060] Although the present application is described in conjunction with the accompanying drawings, the embodiments disclosed in the accompanying drawings are intended to exemplify the preferred implementation modes of the present application and should not be construed as a limitation on the present application.

[0061] Although some embodiments of the overall concept of the present application have been shown and described, those skilled in the art will understand that the present application may include more other equivalent embodiments without departing from the overall inventive concept of the present application, and the protection scope of the present application is defined by the claims.

Claims

1. A lighting device (100), characterized in that: It comprises a constant current source circuit (10), a current balancing circuit (20) and a light-emitting component (30); Wherein, the constant current source circuit (10) comprises an output positive electrode (Vo+) and an output negative electrode (GND), and the constant current source circuit (10) is used to output an output current (Io) between the output positive electrode (Vo+) and the output negative electrode (GND); The light-emitting component (30) comprises N light-emitting branches (31, 32, 33), N being an integer greater than or equal to 2, the first end (31a, 32a, 33a) of each light-emitting branch being electrically connected to the output positive electrode (Vo+) through the current balancing circuit (20), and the second end (31b, 32b, 33b) of each light-emitting branch being electrically connected to the output negative electrode (GND); The current balancing circuit (20) is used to receive and balance the output current (Io), and provide balanced driving currents (I1, I2, I3) for the N light-emitting branches.

2. The lighting device according to claim 1, characterized in that: When the light-emitting component (30) works normally, the difference between the driving currents of the N light-emitting branches is less than 1 mA.

3. The lighting device according to claim 1, characterized in that: Each of the light-emitting branches includes a plurality of light-emitting elements. In each of the light-emitting branches, the plurality of light-emitting elements are connected in series between the first end and the second end of the corresponding light-emitting branch. When any of the light-emitting elements is short-circuited, the difference in current of the N light-emitting branches is less than 1 mA.

4. The lighting device according to claim 3, characterized in that: The number of the light-emitting elements in each of the light-emitting branches is the same, and the model of each of the light-emitting elements in the N light-emitting branches is the same. When the driving current flowing through the N light-emitting branches is balanced, the brightness of each of the light-emitting elements is consistent.

5. The lighting device according to any one of claims 1 to 4, characterized in that: The constant current source circuit (10) comprises a current source (Is), the current source (Is) is electrically connected between the output positive electrode (Vo+) and the output negative electrode (GND), and the current source (Is) is used to provide the output current (Io); The current source (Is) includes a DC working mode and / or a PWM working mode. In the DC working mode, the constant current source circuit (10) is used to output a constant DC current. In the PWM working mode, the constant current source circuit (10) is used to output a constant PWM current.

6. The lighting device according to any one of claims 1 to 4, characterized in that: The constant current source circuit (10) further comprises an output overvoltage protection circuit (11), wherein the output overvoltage protection circuit (11) is electrically connected between the output positive electrode (Vo+) and the output negative electrode (GND); When an open circuit fault occurs in any of the light-emitting branches, the drive current of other light-emitting branches that have not experienced an open circuit fault decreases through regulation of the current balancing circuit (20), the output voltage of the constant current source circuit (10) increases, and the output overvoltage protection circuit (11) clamps the output voltage of the constant current source circuit (10) to a saturation voltage.

7. The lighting device according to claim 6, characterized in that: When the output voltage of the constant current source circuit (10) is constant at the saturation voltage within a preset time, the lighting device turns on the overvoltage protection function and turns off the constant current source circuit (10), so that the N light-emitting branches all stop emitting light, thereby realizing the OFAF function.

8. The lighting device according to claim 6, characterized in that: The overvoltage protection circuit (11) comprises a voltage source (Vs) and a first diode (D1) connected in series, the voltage of the voltage source (Vs) being equal to the saturation voltage, The positive electrode of the first diode (D1) is electrically connected to the output positive electrode (Vo+), the negative electrode of the first diode (D1) is electrically connected to the positive electrode of the voltage source (Vs), and the negative electrode of the voltage source (Vs) is electrically connected to the output negative electrode (GND); or, the positive electrode of the voltage source (Vs) is electrically connected to the output positive electrode (Vo+), the negative electrode of the voltage source (Vs) is electrically connected to the positive electrode of the first diode (D1), and the negative electrode of the first diode (D1) is electrically connected to the output negative electrode (GND).

9. The lighting device according to any one of claims 1 to 4, characterized in that: The current balancing circuit (20) comprises N balancing branches (21, 22, 23), each of the balancing branches comprises a first end, a second end and a third end, the first ends (21a, 22a, 23a) of the N balancing branches are electrically connected to the output positive electrode (Vo+), the second ends (21b, 22b, 23b) of the N balancing branches are electrically connected to the first ends (31a, 32a, 33a) of the N light-emitting branches in a one-to-one correspondence, and the third ends (21c, 22c, 23c) of the N balancing branches are electrically connected together.

10. The lighting device according to claim 9, characterized in that: Each of the balanced branches (21, 22, 23) comprises a balanced PNP transistor (Q1, Q2, Q3), and the balanced PNP transistors (Q1, Q2, Q3) of the N balanced branches are the same; In each of the balanced branches (21, 22, 23), the emitter of the balanced PNP transistor (Q1, Q2, Q3) is electrically connected to the first end (21a, 22a, 23a) of the corresponding balanced branch, the collector of the balanced PNP transistor (Q1, Q2, Q3) is electrically connected to the second end (21b, 22b, 23b) of the corresponding balanced branch, and the base of the balanced PNP transistor (Q1, Q2, Q3) is electrically connected to the third end (21c, 22c, 23c) of the corresponding balanced branch.

11. The lighting device according to claim 10, characterized in that: Each of the balancing branches (21, 22, 23) further comprises a bias resistor (R1, R2, R3), and the bias resistors of the N balancing branches are the same; In each of the balanced branches, the bias resistor is electrically connected between the first end of the corresponding balanced branch and the emitter of the balanced PNP transistor (Q1, Q2, Q3).

12. The lighting device according to claim 9, characterized in that: The current balancing circuit (20) comprises a reference branch (200), wherein the reference branch is used to provide a bias current for the balancing PNP transistor and to limit the collector current of the PNP transistor within a preset range.

13. The lighting device according to claim 12, characterized in that: The reference branch (200) comprises a first end (200a) and a second end (200b), the first end (200a) of the reference branch (200) being electrically connected to the third ends (21c, 22c, 23c) of the N balancing branches, and the second end (200b) of the reference branch (200) being electrically connected to the output negative electrode (GND).

14. The lighting device according to claim 13, characterized in that: The reference branch (200) comprises a reference PNP transistor (Qr), a second diode (D2), a third diode (D3), a first reference resistor (Rr1) and a second reference resistor (Rr2); The anode of the second diode (D2) is electrically connected to the first end (200a) of the reference branch (200), the cathode of the second diode (D2) is electrically connected to the anode of the third diode (D3), the cathode of the third diode (D3) is electrically connected to the base of the reference PNP transistor (Qr), the emitter of the reference PNP transistor (Qr) is electrically connected to the first end (200a) of the reference branch (200) through the first reference resistor (Rr1), the collector of the reference PNP transistor (Qr) is electrically connected to the second end (200b) of the reference branch (200), and the base of the reference PNP transistor (Qr) is electrically connected to the second end (200b) of the reference branch (200) through the second reference resistor (Rr2).

15. A motor vehicle, characterized in that: The motor vehicle comprises a lighting device according to any one of claims 1-14.

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