Lighting circuit and vehicle light

Abstract

A lighting circuit is created that is configured to control a light source containing several light-emitting units connected in series. The lighting circuit includes a converter configured to supply a control current to the light source, several high-side switches, each located between one end of a corresponding light-emitting unit and an output of the converter, and several low-side switches, each located between another end of the corresponding light-emitting unit and another output of the converter.

Description

Technical field

[0001] The aspects of the present invention relate to a lighting circuit and a vehicle light used in a motor vehicle or the like. background

[0002] A vehicle light contains several lamps for high beam and low beam. In recent years, these lights have used semiconductor light sources such as light-emitting diodes (LEDs) and laser diodes (LDs).

[0003] US 2011 / 0018441A1 discloses a vehicle-mounted load regulator, a vehicle-mounted headlight assembly, and a vehicle-mounted taillight assembly.

[0004] EP 2 675 247 A1 discloses a light source control device that controls a light source.

[0005] Fig. Figure 1 is a circuit diagram of a vehicle light using a semiconductor light source.

[0006] A vehicle light 1r contains a light source 10 and a lighting circuit 20r for it. The lighting circuit 20r contains a power source 30, several bypass switches 40_1 to 40_N, and a control unit 50. The power source 30 receives a battery voltage V via a switch 4. BAT (also known as input voltage V) IN designated) from a battery 2 and stabilizes a control current I DRV , which flows through the light source 10, to a specific target amount.

[0007] The multiple bypass switches 40_1 to 40_N are assigned to multiple light-emitting units 12_1 to 12_N, and the ON / OFF of each bypass switch 40 can be controlled individually.

[0008] When the i-th bypass switch 40_i is in an ON state, the control current I flows DRVInstead of the light-emitting unit 12_i, the bypass switch 40_i is connected such that the light-emitting unit 12_i is switched off. When the bypass switch 40_i is in an OFF state, the control current I flows. DRV to the light-emitting unit 12_i, such that the light-emitting unit 12_i is switched on. JP-A-2014-017463 discloses an example of a lighting circuit.

[0009] The inventors of the present invention have made the vehicle light 1r from Fig. 1. Analyzed and the following was found.

[0010] The light source 10 and the lighting circuit 20r are connected via wiring (cable bundles). If a fault occurs at any point in the wiring (e.g., a ground fault), some or all of the light-emitting units may not turn on. For example, all light-emitting units 12_1 to 12_N will not turn on if an OUT1 pin is shorted to ground, and if an OUT2 pin is shorted to ground, the light-emitting units 12_2 to 12_N will not turn on in the downstream direction.

[0011] The present invention was made in view of the above circumstances, and an exemplary object of the present invention is to provide a lighting circuit that can reduce functional failures in the event of a fault or an abnormal condition.

[0012] The present invention therefore aims to provide a lighting circuit and a vehicle light that can reduce functional failures in the event of a fault or abnormal condition. This objective is achieved by a lighting circuit according to claim 1, and the objective stated above is also achieved by a vehicle light according to claim 5.

[0013] According to one aspect of the present invention, a lighting circuit is provided which is configured to drive a light source comprising several light-emitting units connected in series. The lighting circuit includes a converter configured to supply a drive current to a light source, several high-side switches, and several low-side switches. Each high-side switch is provided between one end of a corresponding light-emitting unit and one output of the converter. Each low-side switch is provided between another end of the corresponding light-emitting unit and another output of the converter.

[0014] According to this aspect, the ON / OFF state of the multiple light-emitting units can be controlled by controlling the states of the high-side and low-side switches. Furthermore, in the event of a fault, a faulty component can be disconnected, and the illumination of the remaining light-emitting units can be maintained. In this description, the fault may involve a temporary deviation.

[0015] The further output of the converter can be connected to ground, and any low-side switch can be provided between the further end of the corresponding light-emitting unit and ground.

[0016] The lighting circuit can also include a diode placed between adjacent light-emitting units. This prevents reverse current flow.

[0017] The lighting circuit can also include several monitoring circuits, each configured to monitor the electrical state of one end of a corresponding light-emitting unit. Accordingly, the fault can be detected.

[0018] Each monitoring circuit can monitor the voltage at one end of the corresponding light-emitting unit. Accordingly, a short circuit fault, such as a ground fault, a power outage, or an open circuit (disconnection) can be detected.

[0019] According to another aspect of the present invention, a vehicle light is created. The vehicle light can include the light source, which contains the several light-emitting units connected in series, and the lighting circuit described above, which is configured to control the light source.

[0020] Furthermore, any combination of the above configuration elements and the configuration elements and expressions of the present invention can be implemented as methods, devices, systems or the like, which are also effective as aspects of the present invention.

[0021] According to the above configuration, functional failures at the time of the fault can be reduced. Brief description of the drawings Fig. Figure 1 is a circuit diagram of a vehicle light using a semiconductor light source. Fig. Figure 2 is a block diagram of a lighting device which includes a lighting circuit according to one embodiment. Fig. 3A and Fig. 3B are equivalent circuit diagrams of the lighting circuit in a normal state. Fig. 4A and Fig. 4B are equivalent circuit diagrams of the lighting circuit in a fault condition. Fig. Figure 5 is an equivalent circuit diagram of the lighting circuit in a fault condition. Fig. Figure 6 is a circuit diagram of a lighting circuit according to a first modification. Detailed description

[0022] The following describes embodiments of the present invention with reference to the drawings. Identical or equivalent configuration elements, components, and processes shown in each drawing are assigned the same reference numerals, and repeated descriptions have been omitted where appropriate. Furthermore, these descriptions are not intended to limit the invention, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

[0023] In the present description, “a state in which an element A is connected to an element B” includes not only a case in which the element A and the element B are physically and directly connected, but also a case in which the element A and the element B are indirectly connected via other elements that do not substantially affect any electrical connection state of the same or impair any function or effect exerted by the connection of the same.

[0024] Likewise, “a state in which an element C is provided between element A and element B” does not merely include a case in which element A and element C or element B and element C are directly connected, but also a case in which element A and element C or element B and element C are indirectly connected via other elements that do not substantially affect any electrical connection state of the latter or impair any function or effect exerted by the connection of the former.

[0025] In the description, reference symbols assigned to electrical signals such as voltage and current signals, or circuit elements such as resistors and capacitors, represent voltage and current values, or resistance and capacitance values, as needed.

[0026] Fig. Figure 2 is a block diagram of a lighting device 100, which includes a lighting circuit 300 according to the embodiment. The lighting device 100 includes a light source 200 and the lighting circuit 300. The light source 200 includes several light-emitting units 202_1 to 202_N connected in series. The number N of light-emitting units 202 is not specifically limited. N = 4 in the present embodiment. Examples of the light-emitting units 202 include, but are not limited to, a light-emitting diode (LED), a laser diode (LD), and an organic EL element. Each light-emitting unit 202 can contain several light-emitting elements connected in series and / or parallel.

[0027] The light source 200 and the lighting circuit 300 are connected via the cable strands 210. The lighting circuit 300 receives a power supply voltage (i.e., a battery voltage) V via a lighting switch SWB. BAT from battery 2 and controls the light source 200. The lighting circuit 300 contains a converter 310, several high-side switches SW1_1 to SW1_N, several low-side switches SW2_1 to SW2_N, a control unit 320 and several monitoring circuits 330_1 to 330_N.

[0028] The converter 310 supplies a control current I to the light source 200. DRVThe type of converter 310 is not particularly restricted, and a known switching converter such as a buck converter, a boost converter, a buck-boost converter, a Cuk converter, a forward converter, or a reverse converter can be used. The type of converter 310 can be determined according to a forward voltage Vf of the light-emitting unit 202 and its number N. In particular, if Vf × N < V BAT , a buck converter type such as converter 310 can be used, and if Vf × N > V BAT , a boost converter type or a combination of the boost converter type on a front stage and a buck converter type on a rear stage can be used.

[0029] In the present embodiment, the number of high-side switches SW1 and the number of low-side switches SW2 are four, which is equal to the number N of light-emitting units 202.

[0030] The i-th (1 ≤ i ≤ N) high-side switch SW1_i is provided between one end (i.e., an anode) of a corresponding light-emitting unit 202_i and an output (i.e., a positive electrode) of the converter 310. The i-th low-side switch SW2_i is provided between another end (i.e., a cathode) of the corresponding light-emitting unit 202_i and another output (i.e., a negative electrode) of the converter 310. In the present embodiment, the negative electrode of the converter 310 is connected to ground, and a positive voltage V is applied to the positive electrode of the converter 310. OUT generated. Therefore, the lower-side switch SW2_i is provided in an equivalent manner to be located between the other end (i.e., the cathode) of the corresponding light-emitting unit 202_i and ground.

[0031] Several diodes (i.e., rectifier elements) D1 to D3 are provided between respective adjacent light-emitting units 202.

[0032] The monitoring circuits 330_1 to 330_N monitor the electrical state of one end (the anode in the present embodiment) of the corresponding light-emitting unit 202 and determine whether a short-circuit fault or an open-circuit fault has occurred. For example, the monitoring circuit 330 includes a voltage comparator and can detect respective faults by comparing a voltage to be monitored with a threshold for detecting a short circuit and a threshold for detecting an open circuit. For a specific fault detection method and circuit configuration therefor, a monitoring circuit can be used that is similar to the monitoring circuit used in a workaround method described in Fig. 1 is shown.

[0033] The control unit 320 controls the multiple switches SW1 and SW2. For example, the control unit 320 can be a microcomputer or a central processing unit (CPU).

[0034] A basic configuration of the lighting circuit 300 was described above. Its operation is described next. A state of the switches, described below, can be controlled by the control unit 320 and its interaction with other circuits. (Normal state)

[0035] The lighting circuit 300 can switch on any of the light-emitting units 202 that are connected in succession and switch off the remaining light-emitting units 202.

[0036] For example, if all light-emitting units 202 are to be switched on, the high-side switch SW1_1 on the side of the highest potential is switched on, the low-side switch SW2_4 on the side of the lowest potential is switched on, and the remaining switches are switched off.

[0037] It is generalized that when it is intended to switch on the i-th light-emitting unit 202_i up to the j-th light-emitting unit 202_j (1 ≤ i ≤ j ≤ N), the high-side switch SW1_i and the low-side switch SW2_j are switched on.

[0038] While this state is assumed as the basis, some of the light-emitting units 202_i to 202_j can be individually switched off or dimmed. Fig. 3A and Fig. Figure 3B shows equivalent circuit diagrams of the lighting circuit 300 in a normal state. Fig. 3A and Fig. 3B refers to switches that do not contribute to the process; these have been omitted.

[0039] In Fig. 3A i = 1, j = 4, meaning SW1_1 and SW2_4 are set to ON states. Accordingly, all light-emitting units 202_1 to 202_4 can be switched on.

[0040] The high-sided switch SW1_2 also acts as a bypass switch for the light-emitting unit 202_1. The high-sided switch SW1_3 acts as a bypass switch for the light-emitting units 202_1 and 202_2. The high-sided switch SW1_4 acts as a bypass switch for the light-emitting units 202_1 to 202_3. It is generalized that the k-th high-sided switch SW1_k acts as a bypass switch for the light-emitting units 202_1 to 202_(k - 1).

[0041] In Fig. 3A: The upper-side switch SW1_2 is turned on when the light-emitting unit 202_1 is to be temporarily switched off. When the light-emitting unit 202_1 is to be dimmed, the upper-side switch SW1_2 is switched with a duty cycle corresponding to a target brightness.

[0042] In Fig. 3B are i = 2, j = 3, meaning that SW1_2 and SW2_3 are set to ON states. Accordingly, the two light-emitting units 202_2 and 202_3 can be switched on.

[0043] In Fig. 3B, the high-sided switch SW1_3 is turned on when the light-emitting unit 202_2 is to be temporarily switched off. When the light-emitting unit 202_2 is to be dimmed, the high-sided switch SW1_3 is switched with a duty cycle corresponding to a target brightness.

[0044] Fig. 3A and Fig. 3B are merely examples, and any combination of i and j can be selected. (Error state)

[0045] Fig. 4A and Fig. 4B are equivalent circuit diagrams of the lighting circuit 300 in a fault condition.

[0046] Fig. 4A shows a situation in which a fault occurs at an anode (which is called fault node N). SHORT (is designated) the light-emitting unit 202_1 on the side of the highest potential in the state from Fig. 3A a short circuit occurs, such as a ground fault or a power outage. In particular, the fault node can occur at an output pin P1 of the lighting circuit 300, the wiring of a cable harness connected to it, or the like.

[0047] The control unit 320 switches the nearest adjacent high-sided switch SW1_2 on a side with a lower potential than that of node N. SHORTon and switches off the remaining high-side switches SW1_1, SW1_3 and SW1_4.

[0048] Accordingly, the control current I DRV , which is generated by converter 310, the error node N SHORT The high-side switch SW1_2 bypasses the circuit, and power can be continuously supplied to the light-emitting units 202_2 to 202_4. This means that, since the illumination states of the light-emitting units 202_2 to 202_4 can be maintained, the risk of malfunction can be reduced.

[0049] To protect the light-emitting units 202 from overvoltage, a clamping diode (i.e., a Zener diode) 204, acting as a clamping circuit, can be connected in reverse parallel to each light-emitting unit 202. Fig. Figure 4A shows only the clamping diode 204 for the light-emitting unit 202_1; the clamping diodes 204 of the other light-emitting units 202 are omitted. The clamping diode 204 can provide a current path from the cathode to the anode of the light-emitting unit 202 at the time of a short-circuit fault. The diode D1 is provided to prevent the drive current I from DRV , which flows through the high-side switch SW1_2, via the terminal diode 204 to the fault node N SHORT flows. Accordingly, the illumination of the light-emitting units 202_2 to 202_4 can be maintained in this state and an overcurrent flowing through the clamping diode 204 can be prevented.

[0050] Even if the clamping diode 204 is not provided, various fault modes can be avoided by providing diodes D1 to D3. For example, if the cathode of the light-emitting unit 202_1 is short-circuited to ground when the high-side switch SW1_2 is switched on, the light-emitting units 202_2 to 202_4 can be switched on, since the effect of the ground fault is eliminated by the provision of diode D1.

[0051] In Fig. 4B occurs at an anode (which passes through the fault node N). SHORT (as shown) the second light-emitting unit 202_2 experiences a short circuit such as a ground fault or a power failure.

[0052] The control unit 320 switches the nearest adjacent high-sided switch SW1_3 on a side with a lower potential than that of node N. SHORT, where the fault is detected. The remaining high-side switches SW1_1, SW1_2 and SW1_4 are in OFF states.

[0053] Accordingly, the control current I DRV , which is generated by converter 310, the error node N SHORT The high-side switch SW1_3 bypasses the circuit, and power can be continuously supplied to the light-emitting units 202_3 and 202_4. This means that, since the illumination states of the light-emitting units 202_2 to 202_4 can be maintained, the risk of malfunction can be reduced.

[0054] If a fault occurs at an anode of the light-emitting unit 202_3, the high-side switch SW1_4 is activated, and the remaining high-side switches SW1_1 to SW1_3 are deactivated. Accordingly, the illumination of the light-emitting unit 202_4 can be maintained.

[0055] An example has been described here in which the light-emitting units 202 are protected on one side at a lower potential than that of the fault component; however, this is not limited to this. If the fault component in the light-emitting units 202 occurs close to the low potential, the light-emitting units 202 can be protected on one side at a higher potential than that of the faulty light-emitting units 202. Fig. Figure 5 is an equivalent circuit diagram of the lighting circuit 300 in a fault condition. Fig. 5. An open circuit fault occurs at an anode of the fourth light-emitting unit 202_4. In this case, the nearest adjacent low-side switch SW2_3 on a side with a higher potential than that of the fault point is turned on, and the remaining low-side switches are turned off.

[0056] It is generalized that if the light-emitting unit 202_k, whose fault is detected, is within the illumination target range, i.e., if i ≤ k ≤ j, the control unit 320 modifies i or j such that the light-emitting unit 202_k is located outside the illumination target range. If i is modified, the high-side switch SW1_i corresponding to the modified i is turned on, and if j is modified, the low-side switch SW2_j corresponding to the modified j is turned on.

[0057] The above description describes the operation of lighting circuit 300. According to lighting circuit 300, the ON / OFF of several light-emitting units 202 can be controlled by controlling the states of the high-side switches SW1 and the low-side switches SW2. Furthermore, in the event of a fault, the faulty component can be disconnected, and the remaining light-emitting units can be protected in such a way that the lighting is maintained. (Applications)

[0058] The lighting device 100 described above can be a vehicle light. In this case, one of the several light-emitting units 202 can be a low beam, and another can be a high beam. Another can be a daytime running light (DRL), and another can be a DRL / marker light.

[0059] Considering the protection procedure at the time of a fault, a luminaire of relatively high importance may be assigned to the lower potential side, and a luminaire of low importance may be assigned to the higher potential side.

[0060] For example, the high beam and low beam can be considered more important than the DRL and the DRL / outline light. Therefore, for example, with N = 4, the multiple light-emitting units 202 can be assigned from the high-potential side in the order of the DRL lamp, the DRL / outline light, the high beam, and the low beam.

[0061] Although the present invention has been described with reference to certain embodiments, the embodiments merely illustrate the principle and application of the present invention, and various modifications and changes to the configurations can be made in the embodiments without deviating from the inventive concept of the present invention as defined in the claims. (First modification)

[0062] Fig. Figure 6 is a circuit diagram of a 300A lighting circuit according to a first modification. The converter 310 outputs a negative voltage, and, for example, a Cuk converter can be used. In this case, the positive electrode output (+) of the converter 310 is connected to ground, and a negative output voltage -V is applied to the negative electrode output (-). OUT generated. (Second modification)

[0063] When the lighting device 100 is used as a vehicle light, several light-emitting units 202 can be used as a headlight with variable light distribution (i.e., ADB: adaptive driving light).

[0064] The ADB dynamically and adaptively controls a light distribution pattern according to the situation in front of the vehicle (e.g., presence or absence of an oncoming vehicle, vehicles ahead, or pedestrians). (Third modification)

[0065] Although it is explained that the high-side switches in the embodiment can also be used as bypass switches for the light-emitting units on the higher potential side, the high-side switches, bypass switches, can be provided in parallel with the light-emitting units to control PWM dimming or to switch ON / OFF states individually.

[0066] When the lighting device 100 is used as a vehicle light, several light-emitting units 202 can be used as a headlight with variable light distribution (i.e., ADB: adaptive driving light). The ADB dynamically and adaptively controls a light distribution pattern according to the situation in front of the vehicle (e.g., the presence or absence of an oncoming vehicle, vehicles ahead, or pedestrians).

[0067] In this case, the light source can be 200. Fig.2. A light source for a high beam. The vehicle light can include an optical system that projects the light emitted by the multiple light-emitting units 202 into different areas on a virtual, vertical screen in front of the vehicle. By controlling the ON and OFF of the light-emitting units 202, the brightness of the corresponding areas can be changed, and a desired light distribution pattern can be formed.

Claims

[1] Lighting circuit (300) configured to drive a light source (200) containing several light-emitting units (202, 202_1 to 202_N) connected in series, wherein the lighting circuit (300) includes: a converter (310) configured to supply a control current to the light source (200); several high-sided switches (SW1_1 to SW1_N), each of which is provided between one end of a corresponding light-emitting unit (202, 202_1 to 202_N) and an output of the converter (310); and several low-side switches (SW2_1 to SW2_N), each of which is provided between another end of the corresponding light-emitting unit (202) and another output of the converter (310). [2] Lighting circuit (300) according to claim 1, further comprising: a diode (D1 to D3) which is provided between respective adjacent light-emitting units (202, 202_1 to 202_N). [3] Lighting circuit (300) according to claim 1 or 2, further comprising: several monitoring circuits (330_1 to 330_N), each of which is configured to monitor an electrical state of one end of a corresponding light-emitting unit (202, 202_1 to 202_N). [4] Lighting circuit (300) according to one of claims 1 to 3, wherein the further output of the converter (310) is connected to ground, and wherein each low-side switch SW2_1 to SW2_N) is provided between the far end of the corresponding light-emitting unit (202) and ground. [5] Vehicle light comprising the following: a light source (200) containing several light-emitting units (202, 202_1 to 202_N) connected in series; and the lighting circuit (300) according to one of claims 1 to 4, which is configured to control the light source (200).

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