Vehicle light and lighting circuit for a light source

Abstract

Lighting circuit (200R) configured to operate a light source (300) comprising several light-emitting elements (302_1... 302_N) connected in series, wherein the lighting circuit (200R) comprises: several bypass switches (SWB1...SWB i , which are connected in parallel to the light-emitting elements (302_1... 302_N); a switching converter (210); and a converter control device (500) which is configured to (i) a luminaire current (I LAMP ), generated by the switching converter (210), in a switched-on lighting state in which at least one of the several light-emitting elements (302_1... 302_N) is switched on, to a first setpoint (I REF1 ) to stabilize, and (ii) the luminaire current (I LAMP) in a completely switched-off lighting state, in which all of the several light-emitting elements (302_1...302_N) are switched off, to a second setpoint (I REF2 ), which is smaller than the first setpoint (I REF1 ) is to stabilize, wherein the converter control unit (500) comprises: a first control device (510) which is configured to issue a first control pulse (S) in the switched-on lighting state CNT1 ) to generate with a comparatively high degree of accuracy using a control method; a second control device (520) which is configured to issue a second control pulse (S) when the lighting is completely switched off CNT2 ) to produce a process with comparatively low accuracy; and a driver circuit (530) configured to control the switching converter (210) according to the first control pulse (S CNT1) and the second control impulse (S CNT2 ) to head towards.

Description

TECHNICAL FIELD

[0001] Aspects of the present invention relate to an illumination circuit for a semiconductor light source. BACKGROUND

[0002] A vehicle headlight can usually be switched between low beam and high beam. The low beam provides a specific illumination for a close range and a light distribution designed to avoid dazzling an oncoming vehicle or a vehicle ahead, so the low beam is primarily used when driving in urban areas.

[0003] The high beam provides bright illumination for a wide, distant area ahead and is primarily used when driving at high speed on a road with few oncoming or preceding vehicles. Although the high beam provides the driver with better visibility than the low beam, the high beam could dazzle the driver of a vehicle ahead or a pedestrian in front of the vehicle.

[0004] Recently, an adaptive driving beam (ADB) technology has been proposed that dynamically and adaptively adjusts the high beam light distribution pattern based on the vehicle's environmental conditions. ADB technology reduces glare to a vehicle or pedestrian by detecting a preceding vehicle, an oncoming vehicle, or a pedestrian in front of the vehicle and dimming or turning off the light for an area corresponding to the detected vehicle or pedestrian.

[0005] Fig. 1 is a circuit block diagram of a vehicle lamp 100R studied by the inventors of the present application. The vehicle lamp 100R includes a lighting circuit 200R and a light source 300.

[0006] The light source 300 includes a plurality of (N; N ≥ 2) light-emitting elements 302_1 to 302_N. The lighting circuit 200R is configured to independently control the switching on / off of the light source 300 by a bypass method. The lighting circuit 200R includes a constant current circuit 202R, a bypass circuit 280, and a bypass controller 290.

[0007] The constant current circuit 202R generates a driver current (luminaire current) I stabilized to a setpoint LAMP . The bypass circuit 280 has a plurality of bypass switches SWB1 to SWB N A bypass switch SWB i (1 ≤ i ≤ N) is provided between both ends of a corresponding light-emitting element 302_i. The bypass control device 290 individually controls the turning on / off of the plurality of bypass switches SWB1 to SWB Nto obtain a desired light distribution pattern. If an i-th bypass switch SWB i is switched off, the luminaire current I LAMP into the light-emitting element 302_i, and consequently the light-emitting element 302_i is turned on. When the i-th bypass switch SWB i is switched on, the light-emitting element 302_i is switched off, since the luminaire current I LAMP through the bypass switch SWB i and no current flows into the light-emitting element 302_i.

[0008] The constant current circuit 202R comprises a switching converter 204, a measuring resistor R s , a current detection circuit 206 and a converter control device 208.

[0009] The measuring resistor R s is on a path of the luminous flux I LAMP provided, and a voltage drop proportional to the luminaire current I LAMP between both ends of the measuring resistor R sThe current detection circuit 206 generates a current detection signal V cs based on the voltage drop of the measuring resistor R s .

[0010] The switching converter 204 is a buck converter or a boost converter. The converter control device 208 controls the switching converter 204 so that the detection signal V cs a reference voltage V REF according to the target value of the luminaire current. For example, JP-A-2014-180099 discloses a lighting control device.

[0011] Further prior art helpful for understanding the present invention can be found in the following documents: DE 10 2015 204 526 A1 relates to a control device used together with a light source comprising a plurality of light emitting units connected in series to form a vehicle lamp.

[0012] DE 10 2015 219 100 A1 concerns a lighting circuit mounted in a vehicle lamp that can change the luminous intensity at high speeds.

[0013] The inventors of the present application have, after examining the vehicle lamp 100R according to the Fig. 1 identified the following problems.

[0014] There may be a period of time in which all of the plurality of light-emitting elements 302_1 to 302_N are turned off (in a completely off lighting state) according to a light distribution pattern. It is possible to stop or deactivate the constant current circuit 200R, thereby reducing the luminaire current I LAMP is set to zero to achieve a sufficiently long, completely off lighting state.

[0015] However, in a situation where a temporary fully off state repeatedly occurs (for example, a situation where PWM control is performed for each bypass switch of the bypass circuit 280), the constant current circuit 202R cannot be deactivated to the fully off lighting state. This is because a delay occurs when the constant current circuit 202R is stabilized from the deactivated state to an operating state, and the luminaire current I LAMP is not stabilized at the set value during the delay, so that the luminous intensity of the light-emitting element becomes unstable. Therefore, it is necessary that the constant current circuit 202R maintains a constant luminaire current I even in the fully off lighting state. LAMP generated.

[0016] If the switching operation of the switching converter 204 is maintained in the completely switched-off lighting state, the same amount of the luminaire current I continues to flow. REF into a switching transistor M1 and the bypass switches SWB, as in the normal lighting-on state. Consequently, the lighting circuit consumes 200R of electrical power even though the light source is off, causing the transistors that configure the bypass switches SWB to generate heat. Furthermore, a transistor that can withstand heat is large and expensive.

[0017] The present invention has been made in view of the above circumstances, and according to one aspect of the present invention, there is provided a lighting circuit configured to maintain switching operations of a switching converter capable of reducing power consumption in a fully off lighting state.

[0018] According to one aspect of the present invention, a lighting circuit is provided configured to operate a light source having a plurality of light-emitting elements connected in series. The lighting circuit includes: a plurality of bypass switches connected in parallel with the light-emitting elements, respectively; a switching converter; and a converter controller configured to stabilize a lamp current generated by the switching converter to a first set value in an on-illumination state in which at least one of the plurality of light-emitting elements is turned on, and to stabilize the lamp current to a second set value, which is smaller than the first set value, in a fully off-illumination state in which all of the plurality of light-emitting elements are turned off.

[0019] According to this structure, heat generation can be reduced because the current flowing into the multiple bypass switches in the fully off state can be reduced. Since the amount of heat generation is thus reduced, inexpensive, small-sized parts can be used.

[0020] According to the invention, the converter control device comprises: a first control device which is configured to generate a first control pulse in the switched-on lighting state by a control method with a comparatively high accuracy, a second control device which is configured to generate a second control pulse in a completely switched-off lighting state by a control method with a comparatively low accuracy, and a driver circuit which is configured to operate or address the switching converter according to the first control pulse and the second control pulse.

[0021] The lighting circuit may further comprise a determination circuit configured to compare a voltage across the light source with a threshold voltage and to determine that the light source is in the fully off lighting state when the voltage across the light source is less than the threshold voltage.

[0022] The lighting circuit may further include: a bypass control device configured to control the plurality of bypass switches; and a determination circuit configured to detect the fully off lighting state according to a control signal from the bypass control device.

[0023] According to another aspect of the present invention, a vehicle lamp is provided. The vehicle lamp includes: the light source having the plurality of light-emitting elements connected in series; and the lighting circuit set forth above, which is configured to turn on the light source.

[0024] The vehicle lamp may further include a scanning optical system configured to receive light emitted from the light source and to scan or scan the area in front of the vehicle.

[0025] It should be noted that all combinations of the above components and the components and expressions that are applicable or replaceable in methods, devices, systems or the like are also considered aspects of the present invention.

[0026] According to the above structure, the heat generation in the fully off lighting state can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a circuit block diagram of a vehicle lamp studied by the inventors. Fig. 2 is a block diagram of a lamp system including the vehicle lamp according to an embodiment of the present invention. Fig. 3 is a diagram of functional waveforms of the vehicle lamp according to Fig. 2. Fig. 4 is a block diagram of a lighting circuit according to an embodiment of the present invention. Fig. 5 is a diagram showing a specific example of the structure of a converter control device. Fig. 6 is a diagram illustrating overcurrent protection by a second control device. Fig. Figure 7 is a simplified block diagram of a driver IC. Fig. 8 is a circuit diagram of a lighting circuit using the driver IC according to Fig. 7. Fig. 9 is a perspective view of a scanning vehicle lamp. Fig. 10A to 10D are diagrams illustrating the formation of light distribution patterns. DESCRIPTION OF EMBODIMENTS

[0027] Embodiments of the present invention will be described below with reference to the drawings. Identical or equivalent components, elements, and processes shown in the drawings are denoted by the same reference numerals, and repetitive descriptions are omitted where appropriate.

[0028] In the specification, the phrase "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 to each other, but also a case in which the element A and the element B are indirectly connected via other elements without causing any significant effects on the electrical connection state thereof or impairing any functions or effects due to the connection thereof.

[0029] Similarly, the phrase "a state in which an element C is provided between an element A and an element B" includes not only a case in which the element A and the element C or the element B and the element C are directly connected to each other, but also a case in which the element A and the element C or the element B and the element C are indirectly connected via other elements, without causing any substantial effects with respect to the electrical connection thereof or impairing any functions or effects due to the connection thereof.

[0030] Furthermore, in the specification, reference numerals assigned to electrical signals such as voltage signals and current signals, or electrical elements such as resistors and capacitors, denote voltage values ​​and current values ​​or resistance values ​​and capacitance values, where necessary.

[0031] Fig. Figure 2 is a block diagram of a lighting system 1 including a vehicle lamp 100 according to an embodiment of the present invention. The lighting system 1 includes a battery 2, a vehicle electronic control unit (ECU) 4, and a vehicle lamp 100. The vehicle lamp 100 receives power of a DC voltage (battery voltage) V BAT from the battery 2. The vehicle lamp 100 is connected to the vehicle ECU 4 via a Controller Area Network (CAN), a Local Interconnect Network (LIN) or the like.

[0032] The vehicle lamp 100 includes a lighting circuit 200, a light source 300, and a lamp electronic control unit (ECU) 400. The lamp ECU 400 is connected to the vehicle ECU 4 and controls the lighting circuit 200 based on control signals or information from the vehicle ECU 4. In addition to on / off commands, information indicating conditions of the vehicle or its surroundings is also transmitted from the vehicle ECU 4 to the lamp ECU 400. This information includes position information about a preceding vehicle and a pedestrian, vehicle speed, and the like.

[0033] The lamp ECU 400 includes a switch 402 and a processor 404. The switch 402 is provided on a supply path of a power supply voltage from the battery 2 to the lighting circuit 200. The processor 404 is a CPU or a microcomputer and controls the switch 402 based on on / off commands from the vehicle ECU 4. When the switch 402 is turned on in response to a vehicle-side turn-on command, power is supplied to the lighting circuit 200. Based on the information from the vehicle ECU 4, the processor 404 determines a light distribution pattern and controls the lighting circuit 200.

[0034] The light source 300 includes a plurality of (N; N ≥ 2) light-emitting elements 302_1 to 302_N. The lighting circuit 200 is configured to independently control the switching on / off of the light source 300 by a bypass method.

[0035] The lighting circuit 200 comprises a constant current circuit 202, a bypass circuit 280 and a bypass control device 290, comparable to the lighting circuit 200R according to Fig. 1. The bypass circuit 280 and the bypass control device 290 are identical to those according to Fig. 1. The function of the bypass control device 290 can be implemented by the processor 404.

[0036] The constant current circuit 202 includes a switching converter 210 and a converter controller 500. The switching converter 210 is a buck converter, a boost converter, or a buck / boost converter.

[0037] The converter control device 500 controls the switching converter 210 so that a luminaire current I LAMP a setpoint I REF Approximation. In particular, the converter control device 500 is configured to (i) determine a luminaire current I LAMP, generated by the switching converter 210, in a switched-on lighting state in which at least one of the plurality of light-emitting elements 302 is switched on, to a first setpoint value I REF1 to stabilize, and (ii) the luminaire current I LAMP in a fully off lighting state in which all of the plurality of light-emitting elements 302 are turned off, to a second setpoint I REF2 which is smaller than the first setpoint I REF1 is to stabilize.

[0038] For example, a current detection unit 211 is provided on an output side of the switching converter 210 in order to detect the luminaire current I LAMP directly monitor and a first detection signal V CS1 corresponding to the luminaire current I LAMP The current detection unit 211 may be a combination of the measuring resistor R S and the current detection circuit 206 according to Fig. 1. The current detection unit 211 can detect a luminaire current I LAMP on an anode side (high side) of the light source 300 or the luminaire current I LAMP on a cathode side (lower side) of the light source 300.

[0039] The converter control device 500 includes a controller 502, a driver circuit 530, and a determination circuit 540. The determination circuit 540 determines whether the light source is in an on-illumination state or in a completely off-illumination state and generates a determination signal DET indicating the determination result. For example, the determination signal DET is at a low level in the on-illumination state, while it is at a high level in the off-illumination state.

[0040] When the determination signal DET indicates the switched-on lighting state, the control device 502 generates a first control pulse S CNT1 , so that the luminaire current I LAMP , characterized by the first detection signal V CS1 , the first current value I REF1 When the determination signal DET indicates the completely switched-off lighting state, the control device 502 generates a second control pulse S CNT2 , so that the luminaire current I LAMP , characterized by the first detection signal V CS1 , the second current value I REF2 Based on the control pulses S CNT1 / S CNT2 , output from the control device 502, the driver circuit 530 generates a gate drive signal S Gate to control the switching converter 210.

[0041] The structure of the vehicle lamp 100 has been described, and its operation is described below.

[0042] Fig. 3 is a diagram of functional waveforms of the vehicle lamp 100 according to Fig. 2. Here, N = 3. During a time period T0, all bypass switches SWB1 to SWB3 are turned off, and all light-emitting elements 302_1 to 302_3 emit light. At the same time, the output voltage V o of the switching converter 210 to 3 × V F . V F is a forward voltage of the light-emitting elements 302. The luminaire current I LAMP is characterized by a straight line, although small waves or irregularities may occur.

[0043] During a time period T1, the bypass switch SWB1 is turned on, and the light-emitting element 302_1 is turned off. At the same time, the output voltage V o of the switching converter 210 to 2 × V F. During a time period T2, the bypass switches SWB1 and SWB2 are turned on, and the light-emitting elements 302_1 and 302_2 are turned off. At the same time, the output voltage V o of the switching converter 210 to 1 × V F .

[0044] During the time periods T0 to T2, the light source is in the on-illumination state in which at least one of the light-emitting elements 302 is turned on, so that the determination signal DET is at a low level. Consequently, the switching converter 210 is controlled according to a gate control signal S GATE correspond to the first control pulse S CNT1 controlled, and the luminaire current I LAMP is set to the first setpoint I REF1 stabilized.

[0045] During a period T3, all bypass switches SWB1 to SWB3 are turned off, and the light source is in a fully off illumination state in which all light-emitting elements 302_1 to 302_3 are turned off, so that the determination signal DET is at a high level. The switching converter 210 is controlled according to a gate drive signal S GATE according to the second control pulse S CNT2 controlled, and the luminaire current I LAMP is set to the second setpoint I REF2 stabilized.

[0046] In a subsequent time period T4, the output voltage V O to 1 × V F when the bypass switch SWB1 is turned off. Subsequently, the switching converter 210 is switched on according to the first control pulse S CNT1 controlled, and the luminaire current I LAMP is set to the first setpoint I REF1 stabilized.

[0047] The operation of the vehicle lamp 100 has been described. The operation of the vehicle lamp 100 will become even clearer from a comparison with the following comparative technique. In the comparative technique, the switching converter 210 is completely stopped or deactivated, and the lamp current I LAMP becomes zero in the fully off lighting state T3. Since a soft start or activation control is performed when operation is resumed after the switching converter 210 has been fully deactivated, a long delay normally results when the luminaire current I LAMP returns to an original target current.

[0048] On the other hand, according to the vehicle lamp 100 of the embodiment, even in the fully off lighting state T3, the switching operation of the switching converter 210 can be performed according to the second control pulse S CNT2 be continued, and the luminaire current ILAMP can be maintained at a non-zero value. Thus, at a later time when the light-emitting elements 302 are turned on, they can be turned on quickly without controlling the soft start.

[0049] The luminaire current I LAMP In the fully off lighting state T3, it does not contribute to the light emission of the light-emitting elements 302 and is thus consumed unnecessarily. Since the second setpoint I REF2 is set smaller than the first setpoint I REF1 , it is possible to reduce the power consumption in the bypass circuit 280, which in turn reduces the amount of heat generated. This means that it is possible to use small and inexpensive parts that have a lower heat capacity than the bypass switches SWB.

[0050] The inventive concept of the present invention can be applied to various devices, circuits and methods which are shown in the block diagram and the circuit diagram of the Fig. 2 or can be deduced from the above description. To simplify and clarify the understanding of an aspect of the invention and the operation of the circuit, more specific embodiments and modifications are described in detail below.

[0051] Fig. Figure 4 is a block diagram of a lighting circuit 200A according to an embodiment of the present invention. The switching converter 210 is a buck converter and includes a switching transistor M1, an inductor L1, and a rectifier element D1. A first current detection unit 212 includes a first measuring resistor R S1 , provided on a path of the luminaire current I LAMP, and a first current detection circuit 216 for converting a voltage drop of the first measuring resistor R S1 into a first detection signal V CS1 on.

[0052] The converter control device 500A generates the first control pulse S in the switched-on lighting state CNT1 based on the first detection signal V CS1 , which is generated by the first current detection unit 212. According to Fig. 4 is the first measuring resistor R S1 on the anode side (high side) of the light source 300, wherein the power supply of the first current detection circuit 216 is determined from the output V O of the switching converter 210. Since a voltage V L across the light source 300 (bypass circuit 280) drops substantially to zero in the fully off illumination state, the output voltage V Oof the switching converter 210 is very small. As a result, the power supply voltage of the first current detection circuit 216 is insufficient, and no detection signal V CS1 , which is related to the luminaire current I LAMP related to, and the switching converter 210 cannot be controlled.

[0053] A second current detection unit 214 is provided separately from the first current detection unit 212 and is configured to generate a second detection signal V CS2 to generate the luminaire current I LAMP in the completely off lighting state in which the first current detection unit 212 is not operating. It can be said that the second current detection unit 214 detects the luminaire current I LAMP indirectly monitored by monitoring a current or voltage that is related to the luminaire current I LAMPThe second current detection unit 214 may be, for example, an input current of the switching converter 210, a winding current flowing into a winding of the switching converter 210, a current flowing into a switching element of the switching converter 210, or the like.

[0054] The converter control device 500A comprises a first control device 510, a second control device 520, a driver circuit 530, and a determination circuit 540. The control device 510 generates the first control pulse S CNT1 based on the first detection signal V CS1 , which is generated by the first current detection unit 212. The first control device 510 controls a duty cycle and / or frequency and / or ON time and / or OFF time of the first control pulse S CNT1 , so that the luminaire current I LAMP the first setpoint I REF1 approaches.

[0055] In a case where the first current detection unit 212 is provided on an output side of the switching converter 210, as described with reference to Fig. 1, the power supply voltage of the first current detection unit 212 is insufficient in the fully off illumination state of the light source 300, wherein the correlation between the first detection signal V CS1 and the luminaire current I LAMP is lost, so that the first control device 510 does not work.

[0056] In the completely switched off lighting state, the second control device 520 generates a second control pulse S CNT2 , so that the luminaire current I LAMP the second current value or setpoint I REF2 The second control device 520 can generate the second control pulse S CNT2preferably by feedback. In particular, the second control device 520 controls a duty cycle and / or frequency and / or ON time and / or OFF time of the second control pulse S CNT2 based on the second detection signal V CS2 , which is generated by the second current detection unit 214, so that the luminaire current I LAMP to the second setpoint I REF2 approaches.

[0057] The structure of the first controller 510 and the second controller 520 and the configuration of the pulse generation method are not particularly limited. For example, voltage mode, peak current mode, or medium current mode architectures can be adopted for the controllers, and ripple control architectures (hysteresis control, low detection and ON timing, high detection and OFF timing) can also be adopted. In the case of controlling the light source 300 by the bypass method, the first controller 510 and the second controller 520 may preferably be ripple controllers because high-speed response is required.It should be noted that the second control device 520 may operate continuously during a period in which the first control device 510 operates normally.

[0058] The luminaire current I LAMP in the switched-on state defines the luminous intensity of the light source 300, and the luminous current I LAMP in the completely switched-off illumination state, the luminous intensity of the light source 300 is not affected. Thus, the first control device 510 is configured to generate the first control pulse S CNT1 by a control method with a comparatively high accuracy, and the second control device 520 is arranged to generate the second control pulse S CNT2 to be controlled by a control method with comparatively low accuracy.

[0059] The driver circuit 530 controls the switching converter 210 based on the first control pulse S CNT1 and the second control pulse SCNT2 The driver circuit 530 can generate the first control pulse S CNT1 or the second control pulse S CNT2 to select a gate drive signal S GATE Alternatively, the driver circuit 530 may generate the first control pulse S CNT1 and the second control pulse S CNT2 combine to generate the gate drive signal S GATE to generate.

[0060] An example of the structure of a converter control device 500A is described below. The first control device 510 comprises a hysteresis control device. In particular, an upper threshold value I UPPER1 and a lower threshold I BOTTOM1 near the first setpoint I REF1 The first control device 510 shifts the first control pulse S CNT1 to an OFF level (for example, a low level) when the first detection signal V CS1 a voltage V UPPER1corresponding to the upper threshold I UPPER1 reached, and shifts the first control pulse S CNT1 to an ON level (for example, a high level) when the first detection signal V CS1 to a voltage V BOTTOM1 corresponding to the lower threshold I BOTTOM1 falls.

[0061] On an input side of the switching converter 210, the second current detection unit 214 is provided to detect an input current I IN of the switching converter 210 and a second detection signal V CS2 according to the luminaire current I LAMP During a period in which the switching transistor M1 is switched on, the input current I N equal to an output current I LAMP . During a period in which the switching transistor M1 is switched off, the second detection signal V CS2 no correlation with the luminaire current I LAMP on.

[0062] For example, the second current detection unit 214 has a second measuring resistor R S2 , which follows a path of the input stream I IN is provided, and a second current detection circuit 218 for converting a voltage drop of the second measuring resistor R S2 into a second detection signal V CS2 An ON resistor of the switching transistor M1 can be used to set the second measuring resistor R S2 to replace.

[0063] The power supply voltage of the second current detection circuit 218 may be an input voltage of the lighting circuit 200A or an internal voltage obtained by stabilizing the input voltage V IN is obtained. Consequently, it is possible to maintain the operation of the second current detection circuit 218 even in the fully off lighting state.

[0064] The second control device 520 may be a control device for the upper detection and the OFF time setting mode. In particular, the second control device 520 defines an upper threshold I UPPER2 based on the second setpoint I REF2 . The second control device 520 shifts the second control pulse S CNT2 to an OFF level (for example, a low level) when the second detection signal V CS2 a voltage V UPPER2 corresponding to the upper threshold I UPPER2 Furthermore, the second control pulse S CNT2 shifted to an ON level (for example, a high level) when a certain OFF time T OFF has expired. The OFF time T OFF can be constant or adjustable. According to the top detection and OFF time setting method, the second control pulse S CNT2 based on the second detection signal V CS2 be generated.

[0065] In the hysteresis control method, an upper limit and a lower limit of the luminaire current I LAMP defined, whereby only an upper limit of the luminaire current I LAMP upon top detection of the OFF-time setting mode. Thus, it can be said that the current control accuracy of the first control device 510 is greater than that of the second control device 520.

[0066] The determination circuit 540 determines whether the light source is in the fully off illumination state and uses the determination signal DET to activate the second control device 520 when the light source is in the fully off illumination state.

[0067] Fig. Figure 5 is a diagram showing an example of the specific structure of the converter control device 500A. The first control device 510 includes a hysteresis comparator. The hysteresis comparator includes, for example, a variable voltage source 512 and a comparator 514. The variable voltage source 512 outputs the voltage V UPPER1 or V BOTTOM1 according to a state of the output (first control pulse S CNT1 ) of the comparator 514. The comparator 514 compares the first detection signal V CS1 with the output of the variable voltage source 512 and generates a first control pulse S CNT1 .

[0068] The second control device 520 has a comparator 522 and a pulse generator 524. The comparator 522 compares the second detection signal V CS2 with the voltage V UPPER2 corresponding to the upper threshold I UPPER2 and generates an OFF signal S OFF, which is used or used (for example, high level) when the second detection signal V CS2 the voltage V UPPER2 The pulse generator 524 shifts the OFF level in response to the onset of the OFF signal and then generates a second control pulse S shifted to the ON level CNT2 . The pulse generator 524 has a flip-flop 526 and an OFF-time timer 528. The OFF signal S OFF is input to a reset terminal of the flip-flop 526. The OFF-time timer 528 sets an ON signal S ON on after the OFF time T OFF has expired, since the second control pulse S CNT2 is shifted to the OFF navigation. The ON signal S ON is input to a setting terminal of the flip-flop 526. The structure of the flip-flop 526 is not limited to the one shown in Fig. 5 is shown.

[0069] The determination circuit 540 may include a comparator 542 for comparing a voltage corresponding to the voltage across the light source 300 (load voltage V L ), with a certain threshold voltage V TH The determination circuit 540 may determine the output voltage V O of the switching converter 210 with the threshold voltage V TH The determination signal DET, generated by comparator 542, is used in the fully off state (high level) and negated in the on state (low level). By setting the threshold voltage V TH , so that it is smaller than the forward voltage V F of the light-emitting elements 302, it is possible to determine the fully off lighting state based on V O < V F The comparator 542 can also be used as a short-circuit detection circuit.

[0070] In a case where the second control device 520 is a control device of the upper detection and OFF-time setting mode, the second control device 520 may be operated as an overcurrent protection circuit instead of being completely deactivated during a period in which the first control device 510 is operating. In this case, the second upper threshold I UPPER2 by a first threshold I TH1 and a second threshold I TH2 In particular, the upper threshold I UPPER2 the second control device 520 in a state in which the control device 510 is not operating, to the first value I TH1 according to the second setpoint I REF2 Furthermore, the upper threshold I UPPER2 in a state in which the first control device 510 is ready for operation, to the second value I TH2 corresponding to an overcurrent threshold I OCPwhich is greater than the first setpoint I REF1 is set.

[0071] In particular, when the determination signal DET is used, a voltage generated by a voltage source 523 can be set to a first level V REF2 according to the second setpoint I REF2 be set, and when the determination signal DET is negated, the voltage generated by the voltage source 523 can be set according to the overcurrent threshold I OCP to a second level V OCP be set.

[0072] Fig. 6 is a diagram illustrating the operation of the second control device 520. In a state in which at least one of the light-emitting elements 302 is turned on (referred to as the lighting-on state), the determination signal DET is negated. Before a time t0, the first control device 510 operates normally, and the switching transistor M1 is turned on according to the first control pulse S CNT1 , generated by the first control device 510, so that the luminaire current I LAMP in a range between I UPPER1 and I BOTTOM1 corresponding to the first setpoint I REF1 is stabilized. When the first control device 510 operates normally, the second control device 520 does not affect the control of the switching transistor M1.

[0073] Before time t0, the value of the upper threshold I UPPER2 the second control device 520 the second value I TH2corresponding to an overcurrent threshold I OCP2 . It is assumed that at time t0 a malfunction or abnormality occurs in the first control device 510. In the abnormal state, the value of the upper threshold I UPPER2 the second control device 520 to the first value I TH1 , which determines the second setpoint I REF2 defined.

[0074] At time t1, the OFF signal S OFF in the second control device 520. Subsequently, the ON signal S AN at a time t2 after the OFF time T has elapsed OFF used, whereby the second control pulse S CNT2 and the gate drive signal S GATE are at the ON level, so that the switching transistor M1 is turned on. When the switching transistor M1 is turned on, the input current I IN and the second detection signal V increases CS2 . If furthermore I IN> I OCP is fulfilled, in other words, if V CS2 > V OCP is met, the OFF signal S OFF used or accepted in the second control device 520, wherein the second control pulse S CNT2 is shifted to the OFF level and the gate control signal S GATE is at the OFF level, so that the switching transistor M1 is turned off. Furthermore, at a time t4 after the OFF time T OFF the ON signal S ON accepted, and the second control pulse S CNT2 is moved to the AN level.

[0075] Next, an embodiment will be described which, using a commercially available LED driver integrated circuit (IC), provides the same functionality as the lighting circuit 200A of the Fig. 4. Here, the LM3409 from TEXAS INSTRUMENTS INC., United States, is described as an example of an LED driver IC.

[0076] Fig. 7 is a simplified block diagram of a driver IC 600. It should be noted that the driver IC 600 includes the driver circuit 530, the second control device 520 and the second current detection circuit 218 according to Fig. 4 integrated.

[0077] The driver IC 600 includes a control device for the top detection and the OFF time setting process. According to the present embodiment, the control device provided in the driver IC 600 is used as the second control device 520 (and overcurrent protection circuit) according to Fig. 4 used.

[0078] A PGate terminal of the driver IC 600 is connected to a gate of the switching transistor M1. A current adjustment terminal (IADJ) is configured to set a peak current I UPPER, which is used in the top detection and the OFF time setting procedure. A CSP terminal and a CSN terminal for current detection are connected to the second measuring resistor R S2 connected. A voltage V CS2 proportional to the input current I IN is generated between the CSP port and the CSN port.

[0079] A level shifter 610 has resistances R 21 and R 22 and a V / I conversion circuit 612. The V / I conversion circuit 612 generates a current I ADJ proportional to a voltage V IADJ , which is input to the IADJ connector. A voltage drop I ADJ × R 21 , corresponding to the upper threshold I UPPER2 , is applied to the resistor R 21 generated, and a voltage V CSP - I ADJ × R 21 is at a low potential at one end of the resistor R 21A voltage drop across the resistor R 22 is essentially zero. The level shifter 610 corresponds to the second current detection circuit 218 and the voltage source 523 according to Fig. 5.

[0080] The comparator 614 corresponds to the comparator 522 according to Fig. 5. The comparator 614 compares a voltage at one end of the resistor R 21 with a voltage at one end of the resistor R 22 and generates an OFF signal S OFF . That is, the comparator 614 compares V CSP - I ADJ × R 21 with V CSP - R S2 × I IN This is equivalent to a comparison between I ADJ × R 21 and R S2 × I IN . The OFF signal S OFF is used or accepted if I IN > I ADJ × R 21 / R S2 is fulfilled.

[0081] The IADJ pin of the driver IC 600 is an adjustment pin for setting the upper threshold I UPPER2 (and I OCP ). A voltage V IADJ , which has a level that I OCP when the first control device 510 is ready for operation and has a level that I UPPER2 when the first control device 510 is not operational is input to the IADJ port.

[0082] A capacitor for the OFF time setting is attached to the outside of the COFF terminal. A GND terminal is grounded. The input voltage V IN is a V IN -connection.

[0083] The pulse generator 616 includes a logic circuit 620 and an OFF-time timer circuit 622. When the output S OFF of the comparator 614, the logic circuit 620 shifts the second control pulse S CNT2to the OFF level and provides a start trigger for the OFF-time timer circuit 622. The logic circuit 620 is equivalent to the flip-flop 526 according to Fig. 5, and the OFF-time timer circuit 622 is equivalent to the OFF-time timer 528 according to Fig. 5.

[0084] The OFF-time timer circuit 622 starts operating in response to the start trigger and sets an ON signal S ON after the OFF time T has elapsed OFF The OFF-time timer circuit 622 includes, for example but without limitation, a switch connected in parallel with the capacitor C tm which is mounted externally between the COFF terminal and the earth, and a comparator which measures the voltage V COFF and the COFF terminal with a certain voltage V OFF Furthermore, a charging voltage V C via a resistor R tm applied to the COFF terminal. If V COFF > VOFF is met, the switch of the OFF-time timer circuit 622 is turned on and the capacitance C tm discharged. It is possible to set the OFF time according to a capacity value of the capacity C tm , a charging voltage V C and a resistance value R tm The logic circuit 620 shifts the second control pulse S CNT2 in response to the use of the ON signal S ON to an AN level.

[0085] An output of the driver circuit 530 is connected to the gate of the switching transistor M1 via the PGATE terminal.

[0086] Driver IC 600 has an enable terminal (EN) and is enabled when a high level is input to the enable terminal. During a time when a low level is input to the enable terminal, driver IC 600 is disabled, and the gate output PGATE is fixed at the low level, so switching transistor M1 is turned off.

[0087] Fig. Fig. 8 is a circuit diagram of a lighting circuit 200B including the driver IC 600 according to Fig. 7. The first control pulse S CNT1 , generated by the first control device 510, is input to the enable terminal of the driver IC 600. That is, the entire driver IC 600 is turned on according to the first control pulse S CNT1 switched on / off, and thus a gate control signal S GATE according to the first control pulse S CNT1generated. When all lights are off, the enable terminal EN is fixed at the high level, and a gate drive signal S GATE is determined according to the second control pulse S CNT2 , generated in the driver IC 600, at the PGATE terminal.

[0088] The determination circuit 540 compares the load voltage V L , which is supplied to the light source 300, with the threshold voltage V TH and generates a determination signal DET. When the determination signal DET indicates an on lighting state, a first voltage level is applied to the IADJ terminal, and thus a higher or upper current in the driver IC 600 is set to I OCPand the overcurrent protection function is activated. When the determination signal DET indicates a completely off lighting state, a second voltage level is applied to the IADJ terminal, thus reducing the overcurrent in the driver IC 600 to I UPPER2 set and the second control pulse S CNT2 generated according to the top detection and the OFF time setting mode. That is, the second control device 520 is activated. A filter 270 for removing ripples can be inserted between the switching converter 210 and the light source 300.

[0089] The lighting circuit 200 can be installed in vehicle lights of 100 different types, preferably in a scanning light. Fig. 9 is a perspective view of a scanning vehicle lamp. The vehicle lamp 100 of the Fig. 9 can select multiple light distribution modes according to the driving environment.

[0090] The vehicle lamp 100 essentially comprises: a light source section 110, a scanning optical system 120, a projection optical system 130, and the above-described illumination circuit 200. The light source section 110 has a plurality of light-emitting units 112. The light source section 110 and the light-emitting units 112 correspond to the light source 300 and the light-emitting elements 302 according to Fig. 2. The plurality of light-emitting units 112 are connected to the lighting circuit 200 (not shown) via a connector 114. The light-emitting units 112 comprise semiconductor light sources, such as light-emitting diodes (LEDs) and / or laser diodes (LDs). A light-emitting unit 112 forms a minimal control unit for the light intensity and switching on / off. A light-emitting unit 112 may be an LED chip (LD chip) or may comprise multiple LED chips (LD chips) connected in series and / or parallel.

[0091] The scanning optical system 120 receives light L1 emitted from the light source section 110 and repeats a certain periodic movement so that reflected light L2 of the scanning optical system 120 scans or passes over a front area of ​​the vehicle in a lateral direction (an H direction in the figure). The projection optical system 130 projects the reflected light L2 of the scanning optical system 120 onto a virtual screen 10 in front of the vehicle. The projection optical system 130 may include a reflection optical system, a transmission optical system, or a combination thereof.

[0092] Specifically, the scanning optical system 120 includes a reflector 122 and a motor 124. The reflector 122 is mounted on a rotor of the motor 124 and performs a rotational movement. According to the present embodiment, two reflectors 122 are provided, and the emitted light L2 performs a scan twice per rotation of the motor 124. Consequently, the scanning frequency is twice the rotational speed of the motor. The number of reflectors 122 is not particularly limited.

[0093] At a certain time t0, the light L1 emitted by the light source section 110 is reflected at an angle corresponding to a position of the reflector 122 (a rotation angle of the rotor), and the reflected light L2 at this time forms an irradiation area 12 on the virtual screen 10 in front of the vehicle. For the sake of simplicity of description, the irradiation area 12 is shown in the Fig. 9 is shown rectangular, but the irradiation area 12 is not limited to a rectangular shape, as described below.

[0094] At another time t1, when the position of the reflector 122 changes, a reflection angle changes, at which time reflected light L2' forms an irradiation area 12'. Furthermore, at another time t2, when the position of the reflector 122 changes, at which time reflected light L2'' forms an irradiation area 12''.

[0095] The irradiation section 12 performs scanning on the virtual screen 10 by rotating the scanning optical system 120 at a high speed, and thus light distribution patterns are formed in front of the vehicle.

[0096] Fig. 10A to 10D are diagrams illustrating the formation of light distribution patterns. Fig. 10A shows a layout of the plurality of light-emitting units 112 in the light source section 110. According to the present embodiment, the number of the plurality of light-emitting units 112 is nine.

[0097] The plurality of light-emitting units 112 are arranged at two or more levels (three levels in this example) in the height direction, and the number of light-emitting units 112 is largest at the lowest level. Consequently, it is possible to form a region around a line H on the virtual screen with high luminance.

[0098] The vehicle lamp 100 according to the present embodiment forms the light distribution patterns by superimposing the light distribution based on scanning and the light distribution without scanning. In addition to the plurality of light-emitting units 112_1 to 112_9 for scanning, the light distribution section 110 includes at least one of the light-emitting units 113_1 and 113_2 for widely irradiating a front area of ​​the vehicle in a non-scanning manner. Light emitted from the light-emitting units 113_1 and 113_2 is irradiated onto the virtual screen 10 via an optical system (not shown) different from the scanning optical system 120.

[0099] Fig. 10B is a diagram showing an irradiation spot formed on the virtual screen 10 by the light emitted from the light-emitting units 112, 113 when the reflector 122 is located at a certain position.

[0100] The irradiation point formed by the light-emitting units 112 for scanning or in a scanning manner is referred to as a focal point Sc. Sc i denotes a focus point formed by an i-th illumination unit 112_i (1 ≤ i ≤ 9). A combination of several focus points Sc1 to Sc9 according to Fig. 10B corresponds to an irradiation area 12 according to Fig. 9.

[0101] The diffuse irradiation point formed by the light-emitting units 113 on the virtual screen 10 is referred to as the diffuse point Sd. Sd idenotes a diffuse point formed by an i-th illumination unit 113_i. The diffuse point Sd does not depend on the rotation of the reflector 122. A combination of the diffuse points Sd1 and Sd2 is referred to as a diffuse region 14.

[0102] Fig. Figure 10B shows only the irradiation points Sc and Sd based on the right lamp. In a case where the right lamp and the left lamp are symmetrical, the irradiation points of the left lamp are obtained by left / right inverting the irradiation points of the Fig. 10B formed along a line V.

[0103] Fig. 10C shows areas SR (referred to as scan areas) through which each focus point Sc passes when the reflector 122 rotates. SR i denotes an area through which an i-th focus point SC iA combination of the scan areas SR1 to SR9, i.e., the areas scanned or traversed by the irradiation area 12, is referred to as the focal area 15. The focal area 15 overlaps the diffuse area 14.

[0104] Fig. 10D shows an illumination distribution in a horizontal direction of the light distribution pattern in the vicinity of the line H formed by the light-emitting units 112_1 to 112_5 at the lowest level.

[0105] The actual light distribution pattern is a superposition of a light distribution pattern of the right luminaire and a light distribution pattern of the left luminaire. In this example, the focal area 15 of the left luminaire substantially overlaps the focal area 15 of the right luminaire. The diffuse area 14 of the right luminaire is located primarily on a right side of line V, and the diffuse area 14 (not shown) of the left luminaire is located primarily on a left side of line V.

[0106] Thus, the plurality of light-emitting units 112_1 to 112_9 are arranged for scanning such that the emitted light separately irradiates different portions on the virtual screen. The plurality of light-emitting units 112 may be arranged in a U-shape, as shown in Fig. 10A. It is possible to form left and right ends of the focus areas of the light-emitting units 112 by U-shaped (or E-shaped according to Fig. 10B) Arranging the plurality of light-emitting units 112 on the first, second and third levels.

[0107] For example, the relationship between the plurality of light-emitting units 112 and channels is as follows: First channel CH1 = light-emitting units 112_1 and 112_2; Second channel CH2 = light-emitting unit 112_3; Third channel CH3 = light-emitting units 112_4 and 122_5; Fourth channel CH4 = light-emitting units 112_6 and 122_7; Fifth channel CH5 = light-emitting units 112_8 and 122_9; and light-emitting units 113_1 and 113_2 for the diffuse region are a sixth channel CH6.

[0108] The plurality of light-emitting units 112 are arranged at three levels in the height direction, and the light-emitting units 112 irradiating the same height are assigned to or classified within the same channel to supply the same driving current to the light-emitting units 112 in the same channel. The plurality of light-emitting units 112 provided in the same channel are connected in series to form a light source 300. The lighting circuit 200 is provided in each channel to turn on the light-emitting units included in the corresponding channel.

[0109] In a scanning luminaire, a completely off lighting state in which multiple light-emitting units 112 of the same channel are simultaneously off may occur periodically during a scanning period. Thus, it is possible to reduce power consumption by operating the lighting circuit 200 described above.

[0110] The present invention has been described based on the embodiment. It will be apparent to those skilled in the art that this embodiment is merely an example. Various modifications regarding the combination of components and process sequences can be made, and such modifications are also included within the scope of the present invention. Such modifications are described below. (First modification)

[0111] The switching on / off of the plurality of light-emitting elements 302 is controlled by the bypass controller 290. Consequently, the bypass controller 290 controls when the fully off illumination state occurs. The determination circuit 540 can determine whether the light source is in a fully off illumination state or in an on illumination state based on information from the bypass controller 290. The first modification is indicated by a dot-dash line in Fig. 2. Alternatively, functionality of the determination circuit 540 may be implemented by the bypass controller 290. (Second modification)

[0112] Although in the embodiment the switching converter 210 is a buck converter, the switching converter 210 may also be a boost converter or a buck / boost converter. (Third modification)

[0113] According to the embodiment, the second converter control device 520 generates the second control pulse S CNT2 based on the detection of the detection signal V CS2 from the second current detection unit 214. The present invention is not limited thereto. The second control device 520 may generate the second control pulse S CNT2 in a completely open loop. Although the level at which the luminaire current I LAMP stabilized depends on the input voltage, the second control device 520 can be simplified in this case. For example, the second control device 520 can include an oscillator.

[0114] Although the present invention has been described with specific terms and phrases based on the embodiments, the embodiments merely show one aspect of the principle and application of the present invention, and various modifications and changes of structure may be made to the embodiments without departing from the spirit of the present invention as defined in the claims.

Claims

[1] Lighting circuit (200R) configured to operate a light source (300) comprising a plurality of series-connected light-emitting elements (302_1... 302_N), the lighting circuit (200R) comprising: several bypass switches (SWB1...SWB i which are connected in parallel to the light-emitting elements (302_1... 302_N); a switching converter (210); and a converter control device (500) which is arranged to (i) control a luminaire current (I LAMP ), generated by the switching converter (210), in a switched-on lighting state in which at least one of the plurality of light-emitting elements (302_1... 302_N) is switched on, to a first setpoint value (I REF1 ) and (ii) to stabilize the luminaire current (I LAMP) in a completely switched-off lighting state in which all of the plurality of light-emitting elements (302_1...302_N) are switched off, to a second setpoint value (I REF2 ) which is smaller than the first setpoint (I REF1 ) is to stabilize, wherein the converter control device (500) comprises: a first control device (510) which is arranged to generate a first control pulse (S CNT1 ) by a control method with a comparatively high accuracy; a second control device (520) which is arranged to generate a second control pulse (S CNT2 ) by a process with a comparatively low accuracy; and a driver circuit (530) configured to drive the switching converter (210) in accordance with the first control pulse (S CNT1) and the second control pulse (S CNT2 ) to control. [2] The lighting circuit (200R) according to claim 1, further comprising a determination circuit (540) configured to determine a voltage (V L ) across the light source (300) with a threshold voltage (V TH ) and to determine that the light source (300) is in the fully off illumination state when the voltage (V L ) across the light source (300) is less than the threshold voltage (V TH ) is. [3] The lighting circuit (200R) of claim 1, further comprising: a bypass control device (290) configured to control the plurality of bypass switches (SWB1...SWB i ) and a determination circuit (540) configured to detect the fully off lighting state according to a control signal from the bypass control device (290). [4] Vehicle lamp (100R) which has: a light source (300) comprising a plurality of series-connected light-emitting elements (302_1...302_N); and the lighting circuit (200R) according to one of claims 1 to 3, which is arranged to switch on the light source (300). [5] The vehicle lamp (100R) according to claim 4, further comprising a scanning optical system (120) configured to receive light emitted from the light source (300) and scan an area in front of a vehicle.

Images