JP7636873B2 - Vehicle lighting fixture and lamp control module - Google Patents

Description

This disclosure relates to lighting fixtures for use in vehicles such as automobiles.

In recent years, vehicle lighting has become more and more sophisticated, and headlamps are now equipped with multiple lamps with different functions, such as low beam, high beam, turn signal lamp, position lamp, and daytime running lamp, and it is necessary to control the light sources of these multiple lamps to emit light at an appropriate brightness in response to control signals from the vehicle.

JP 2019-057468 A

The temperature inside a headlamp can become extremely high. If the electrical circuits inside the headlamp continue to operate in a high-temperature state, the lifespan of the components will be shortened. For this reason, headlamps are equipped with temperature sensors and a temperature derating function that reduces the drive current supplied to the semiconductor light-emitting element when the temperature rises.

The temperature derating characteristics need to be optimized for each headlamp depending on the components used in the headlamp and the characteristics of the vehicle in which the headlamp is installed.

Conventionally, it was necessary to design a headlamp by modifying the software program or hardware (e.g., circuit constants) to conform to the headlamp specifications.

This disclosure has been made in consideration of these problems, and one exemplary purpose of one embodiment of the disclosure is to provide a vehicle lamp that allows for flexible setting of derating characteristics.

An aspect of the present disclosure relates to a vehicle lamp, the vehicle lamp including a first light source, a first drive circuit that supplies a first drive current stabilized to a first target current _IREF1 to the first light source, an A/D converter that receives at least one electrical signal indicating a state of the vehicle lamp and generates at least one detection value corresponding to the at least one electrical signal, a non-volatile memory that stores at least one parameter group that defines a derating characteristic of the first light source based on (i) a base current value _IBASE1 of the first drive current and (ii) the at least one detection value, and a signal processing device that receives the at least one detection value and executes a software program to calculate a first target current _IREF1 according to the base current value _IBASE1 and the at least one parameter group.

An aspect of the present disclosure relates to a lamp control module for use in a vehicle lamp having a first light source, the lamp control module including: a first drive circuit for supplying a first drive current stabilized to a first target current _IREF1 to the first light source; an A/D converter for receiving at least one electrical signal indicating a state of the vehicle lamp and generating at least one detection value corresponding to the at least one electrical signal; a non-volatile memory for storing at least one parameter group defining a derating characteristic of the first light source based on (i) a base current value _IBASE1 of the first drive current and (ii) the at least one detection value; and a signal processing device for receiving the at least one detection value and calculating the first target current _IREF1 according to the base current value _IBASE1 and the at least one parameter group by executing a software program.

In addition, any combination of the above components or mutual substitution of the components or expressions of the present invention between methods, devices, systems, etc. are also valid aspects of the present invention.

According to certain aspects of the present disclosure, derating characteristics can be flexibly designed.

1 is a block diagram of a lighting system according to a first embodiment. FIG. 2A and 2B are diagrams showing the relationship between the derating characteristic and the parameter group PRM in the control example 1. 3A and 3B are diagrams showing the relationship between the derating characteristic and the parameter group PRM. FIG. 11 is a block diagram of a lighting system according to a second embodiment. FIG. 2 is a block diagram showing a specific configuration example of a vehicle lamp.

(Overview of the embodiment)
A summary of some exemplary embodiments of the present disclosure will be described. This summary is intended to provide a basic understanding of one or more embodiments as a prelude to the detailed description that follows, and is not intended to limit the scope of the invention or disclosure. Additionally, this summary is not an exhaustive overview of all possible embodiments, nor does it limit essential components of the embodiments. For convenience, the term "one embodiment" may be used to refer to one embodiment or multiple embodiments disclosed herein.

A vehicle lamp according to an embodiment includes a first light source and a lamp control module. The lamp control module includes a first drive circuit that supplies a first drive current stabilized to a first target current _IREF1 to the first light source, an A/D converter that receives at least one electrical signal indicating a state of the vehicle lamp and generates at least one detection value corresponding to the at least one electrical signal, a non-volatile memory that stores at least one parameter group that defines a derating characteristic of the first light source based on (i) a base current value _IBASE1 of the first drive current and (ii) the at least one detection value, and a signal processing device that receives the at least one detection value and executes a software program to calculate the first target current _IREF1 according to the base current value _IBASE1 and the at least one parameter group.

With this configuration, it is possible to change the derating characteristics according to the product specifications by changing the values of the parameter group written to the non-volatile memory without changing the software program, circuit constants, etc. This has the effect of shortening the design period and reducing the design costs.

In one embodiment, the at least one detection value may include a temperature detection value T based on an output of the first temperature sensor, and a voltage detection value V _DD based on an input voltage of the first drive circuit. The parameter group related to the temperature detection value T may include a derating start temperature T _S , a derating end temperature T _E , and a decrease rate α. The parameter group related to the voltage detection value V _DD may include a derating start voltage V _S , a derating end voltage V _E , and a decrease rate β. The signal processing device calculates the amount of current I _{TEMP_DER} after derating related to the temperature detection value T as follows:
I _{TEMP_DER} = I _BASE1 (T<T _S )
I _{TEMP_DER} = I _BASE1 {1-α(T-T _S )} (T _S <T<T _E )
I _{TEMP_DER} =I _BASE1 {1-α(T _E -T _S )} (T _E <T)
The signal processing device may also calculate the amount of current I _{VOLT_DER} after derating related to the voltage detection value V _DD based on the following:
I _{VOLT_DER} = I _BASE1 (V _DD <V _S )
I _{VOLT_DER} = I _BASE1 {1-β(V _DD -V _S )} (V _S <V _DD <V _E )
I _{VOLT_DER} = I _BASE1 {1-β(V _E -V _S )} (V _E <V _DD )
The signal processing device may determine the smaller of the current amounts I _{TEMP_DER} and I _{VOLT_DER} as the first target current I _REF1 .

The parameter group related to the detected temperature value T may further include an abnormality determination temperature T _MAX . The signal processing device may set I _{TEMP — DER} =0 in the range of T _MAX <T.

In one embodiment, the at least one detected value may include a temperature detected value _T1 based on an output of a first temperature sensor and a temperature detected value _T2 based on an output of a second temperature sensor. The parameter group related to the temperature detected value T1 may include a derating start temperature T _S1 , a derating end temperature T _E1 , and a decrease rate α _1. The parameter group related to the temperature detected value _T2 may include a derating start temperature T _S2 , a derating end temperature T _E2 , and a decrease rate α _2. The signal processing device calculates the amount of current I _{TEMP_DER1} after derating related to the temperature detected value _T1 as follows:
I _{TEMP_DER1} = I _BASE1 (T ₁ <T _S1 )
I _{TEMP_DER1} = I _BASE1 {1-α ₁ (T ₁ -T _S1 )} (T _S1 < T ₁ < T _E1 )
I _{TEMP_DER1} = I _BASE1 {1-α ₁ (T _E1 - _{T S1} )} (T _E1 < T ₁ )
The signal processing device may calculate the amount of current I _{TEMP_DER2} after derating related to the temperature detection value _T2 based on the following:
I _{TEMP_DER2} = I _BASE1 (T ₂ <T _S2 )
I _{TEMP_DER2} = I _BASE1 {1-α ₂ (T ₂ -T _S2 )} (T _S2 < T ₂ < T _E2 )
I _{TEMP_DER2} = I _BASE1 {1-α ₂ (T _E2 - _{T S2} )} (T _E2 < T ₂ )
The signal processing device may determine the smaller of the current amounts I _{TEMP_DER1} and I _{TEMP_DER2} as the first target current I _REF1 .

In one embodiment, the at least one detection value may include a temperature detection value _T1 based on an output of a first temperature sensor, a temperature detection value _T2 based on an output of a second temperature sensor, and a voltage detection value V _DD based on an input voltage of the first drive circuit. The parameter group related to the temperature detection value _T1 may include a derating start temperature T _S1 , a derating end temperature T _E1 , and a decrease rate α _1. The parameter group related to the temperature detection value T2 may include a derating start temperature T _S2 , a derating end temperature T _E2 , and a decrease rate α _2. The parameter group related to the voltage detection value V _DD may include a derating start voltage V _S , a derating end voltage V _E , and a decrease rate β. The signal processing device calculates the amount of current I _{TEMP_DER1} after derating related to the temperature detection value _T1 as follows:
I _{TEMP_DER1} = I _BASE1 (T ₁ <T _S1 )
I _{TEMP_DER1} = I _BASE1 {1-α ₁ (T ₁ -T _S1 )} (T _S1 < T ₁ < T _E1 )
I _{TEMP_DER1} = I _BASE1 {1-α ₁ (T _E1 - _{T S1} )} (T _E1 < T ₁ )
The signal processing device may calculate the amount of current I _{TEMP_DER2} after derating related to the temperature detection value _T2 based on the following:
I _{TEMP_DER2} = I _BASE1 (T ₂ <T _S2 )
I _{TEMP_DER2} = I _BASE1 {1-α ₂ (T ₂ -T _S2 )} (T _S2 < T ₂ < T _E2 )
I _{TEMP_DER2} = I _BASE1 {1-α ₂ (T _E2 - _{T S2} )} (T _E2 < T ₂ )
The signal processing device may calculate the amount of current I _{VOLT_DER} after derating related to the voltage detection value V _DD based on the following:
I _{VOLT_DER} = I _BASE1 (V _DD <V _S )
I _{VOLT_DER} = I _BASE1 {1-β(V _DD -V _S )} (V _S <V _DD <V _E )
I _{VOLT_DER} = I _BASE1 {1-β(V _E -V _S )} (V _E <V _DD )
The signal processing device may determine the smallest one of the current amounts I _{TEMP — DER1} , I _{TEMP — DER2} , and I _{VOLT — DER} as the first target current I _REF1 .

The parameter group related to the temperature detection value _T1 may further include an abnormality determination temperature _TMAX1 , and the parameter group related to the temperature detection value _T2 may further include an abnormality determination temperature _TMAX2 . The signal processing device may set I _{TEMP_DER1} =0 in the range of T _MAX1 < _T1 , and set I _{TEMP_DER2} =0 in the range of T _MAX2 < _T2 .

In one embodiment, the first drive circuit, the A/D converter, the non-volatile memory, and the signal processing device may be configured as the same module. The first temperature sensor may be provided inside the module, and the second temperature sensor may be provided outside the module. By monitoring the temperatures both inside and outside the module and performing derating control based on separate parameters, it becomes possible to design the derating characteristics more flexibly.

In one embodiment, the vehicle lamp may further include a second light source. The lamp control module may further include a second drive circuit that supplies the second light source with a second drive current stabilized to a second target current _IREF2 . The non-volatile memory may further store a base current value _IBASE2 of the second drive current, and the signal processing device may calculate the second target current _IREF2 according to the base current value _IBASE2 and at least one parameter group. By sharing the parameter group for each detection value among multiple light sources, control can be simplified.

(Embodiment)
The present invention will be described below based on preferred embodiments with reference to the drawings. The same or equivalent components, parts, and processes shown in each drawing are given the same reference numerals, and duplicated descriptions are omitted as appropriate. In addition, the embodiments are illustrative rather than limiting the invention, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

In this specification, "a state in which component A is connected to component B" includes not only cases in which component A and component B are directly physically connected, but also cases in which component A and component B are indirectly connected via other components that do not substantially affect their electrical connection state or impair the function or effect achieved by their combination.

Similarly, "a state in which component C is provided between components A and B" includes not only cases in which components A and C, or components B and C, are directly connected, but also cases in which they are indirectly connected via other components that do not substantially affect their electrical connection state or impair the function or effect achieved by their combination.

(Embodiment 1)
1 is a block diagram of a lighting system 100 according to embodiment 1. The lighting system 100 includes a vehicle 110 and a vehicle lamp (headlamp) 200. The vehicle 110 includes an electronic control unit (ECU) and a battery on the vehicle side, switches for each lamp, and the like.

The vehicle lamp 200 has functions such as low beam (Lo), high beam (Hi), daytime running lamp (DRL), position lamp (POS), and turn signal lamp (TURN). Figure 1 shows only the configuration related to one of them.

The vehicle lamp 200 includes a first light source 202 and a lamp control module 300. The first light source 202 is one of low beam (Lo), high beam (Hi), daytime running lamp (DRL), and position lamp (POS).

The first light source 202 can be composed of one semiconductor light-emitting element, or multiple semiconductor light-emitting elements connected in series and/or parallel. Examples of semiconductor light-emitting elements include white LEDs (light-emitting diodes), laser diodes, and organic EL (Electro Luminescence) elements. In FIG. 1, the first light source 202 is an LED bar (LED string) consisting of multiple LEDs connected in series. The number of LEDs constituting the first light source 202 may be determined taking into consideration the required brightness and design, and is not particularly limited.

The vehicle lamp 200 is supplied with a power supply voltage +B from the vehicle 110 via the power supply line 102.

The vehicle lamp 200 receives a first lighting request REQ1 from the vehicle 110 via the vehicle bus 106, which instructs the vehicle lamp 200 to turn on or off the first light source 202. The type of vehicle bus is not particularly limited, and a controller area network (CAN) or a local interconnect network (LIN) can be used.

The lamp control module 300 includes an A/D converter 306, a non-volatile memory 308, a bus interface circuit 320, and a first drive circuit 330. The main components of the lamp control module 300 are housed in a single housing and modularized.

The bus interface circuit 320 is a transceiver capable of bidirectional communication with the vehicle 110 via the vehicle bus 106. The data received by the bus interface circuit 320 includes the first lighting request REQ1.

The first drive circuit 330 generates a drive current I _LED1 stabilized to a first target current I _REF1 , and supplies the drive current I LED1 to the first light source 202. The first drive circuit 330 is configured to be able to set the first target current I _REF1 in response to a control signal CNT1.

The signal processing device 400 includes a processor capable of executing software programs. The signal processing device 400 can be configured with a microcontroller, a CPU (Central Processing Unit), a DSP (Digital Signal Processor), etc.

The A/D converter 306 receives at least one (n≧1) electric signal Vs ₁ to Vs _n indicating the state of the vehicle lamp 200, and generates at least one detection value Ds ₁ to Ds _n corresponding to the at least one electric signal Vs ₁ to Vs _n . As described later, a certain electric signal may be the output of a temperature sensor such as a thermistor, or may be the input voltage (power supply voltage) of the first drive circuit 330.

The non-volatile memory 308 stores at least one parameter group PRM ₁ to PRM n that defines the derating characteristics of the first light source 202 based on the base current value I _BASE1 of the first drive current I _LED1 and at least one detection value _{Ds 1} to Ds _n . The i-th (1≦i≦n) parameter group PRM _i defines the derating characteristics based on the corresponding i-th detection value Ds _i . The non-volatile memory 308 may be built in the same package as the signal processing device 400.

The signal processing device 400 receives at least one detection value Ds ₁ to Ds _n and executes a software program to calculate a first target current I _REF1 according to the base current value I _BASE1 and at least one set of parameters PRM ₁ to PRM _n .

For example, the signal processing device 400 calculates a post-derating current amount I _DERi for each detection value Ds _i (i=1 to n), and may set the smallest current amount among the post-derating current amounts I _DER1 to I _DERn as the first target current I _REF1 .
I _REF1 = min (I _DER1 , I _DER2 ,..., I _DERn )
min( ) is a function that selects the minimum value of multiple elements.

In response to the lighting request REQ1, the signal processing device 400 enables the first drive circuit 330. Then, the signal processing device 400 provides the first drive circuit 330 with a control signal CNT1 including the first target current _IREF1 calculated by the above-mentioned software processing.

The above is the configuration of the vehicle lamp 200. With this vehicle lamp 200, the derating characteristics can be changed according to the product specifications by changing the values of the parameter group PRM written to the non-volatile memory 308 without changing the software program, circuit constants, etc. This provides the effects of shortening the design period and reducing the design costs.

Next, we will explain a specific example of derating control.

<Control Example 1>
In control example 1, the signal processing device 400 performs derating based on n=2 detection values _Ds1 and _Ds2 . The detection value _Ds1 is a temperature detection value T based on the output of the temperature sensor, and the detection value _Ds2 is a voltage detection value V _DD based on the input voltage of the first drive circuit 330.

The parameter group describing the derating characteristic will be described. FIGS. 2A and 2B are diagrams showing the relationship between the derating characteristic and the parameter group PRM in control example 1. FIG. 2A shows the temperature derating characteristic based on a detection value _Ds1 representing a temperature T. The horizontal axis represents a detection value (i.e., temperature T) based on the output of a temperature sensor (e.g., a thermistor), and the vertical axis represents the magnitude of the current amount I _{TEMP_DER} after temperature derating for the detection value _Ds1 . In this example, the parameter group _PRM1 includes four parameters, namely, derating start temperature T _S
Derating end temperature T _E
Decrease rate α
Abnormality judgment temperature T _MAX
The temperature derating characteristic is defined by four parameters including the above. The amount of current after derating, I _{TEMP_DER} , is expressed by the following formula.
I _{TEMP_DER} = I _BASE1 (T<T _S )
I _{TEMP_DER} = I _BASE1 {1-α(T-T _S )} (T _S <T<T _E )
I _{TEMP_DER} = I _BASE1 {1-α(T _E -T _S )} (T _E < T < T _MAX )
I _{TEMP_DER} =0 (T _MAX <T)

2B shows a voltage derating characteristic based on a detection value _Ds2 representing a voltage. The horizontal axis represents the detection value V _DD based on the voltage, and the vertical axis represents the magnitude of the current amount I _{VOLT_DER} after voltage derating for the detection value _Ds2 . The parameter group _PRM2 includes four parameters, namely:
Derating start voltage V _S
Derating end voltage V _E
Decrease rate β
Abnormality judgment temperature V _MAX
The voltage derating characteristic is defined by four parameters including: The amount of current I _{VOLT_DER} after derating is expressed by the following formula.
I _{VOLT_DER} = I _BASE1 (V _DD <V _S )
I _{VOLT_DER} = I _BASE1 {1-β(V _DD -V _S )} (V _S <V _DD <V _E )
I _{VOLT_DER} = I _BASE1 {1-β(V _E -V _S )} (V _E <V _DD <V _MAX )
I _{VOLT_DER} = 0 (V _MAX < V _DD )

The target current _IREF1 after considering both temperature and voltage is:
I _REF1 = min (I _{TEMP_DER} , I _{VOLT_DER} )
It becomes.

<Control Example 2>
In control example 2, the signal processing device 400 performs derating based on n=2 detection values _Ds1 and _Ds2 . The detection value _Ds1 is a temperature detection value _T1 based on the output of a first temperature sensor, and the detection value _Ds2 is a temperature detection value _T2 based on the output of a second temperature sensor.

The parameter group describing the derating characteristic will be described. Figures 3(a) and (b) are diagrams showing the relationship between the derating characteristic and the parameter group PRM. Figure 3(a) shows the temperature derating characteristic based on the detection value _Ds1 representing the temperature _{T1 .} The parameter group _PRM1 includes four parameters, namely,
Derating end temperature T _E1
Decrease rate α ₁
Abnormality judgment temperature T _MAX1
The temperature derating characteristic is defined by four parameters including the above. The amount of current I _{TEMP_DER1} after derating is expressed by the following formula.
I _{TEMP_DER1} = I _BASE1 (T ₁ <T _S1 )
I _{TEMP_DER1} = I _BASE1 {1-α ₁ (T ₁ -T _S1 )} (T _S1 < T ₁ < T _E1 )
I _{TEMP_DER1} = I _BASE1 {1-α ₁ (T _E1 - _{T S1} )} (T _E1 < T ₁ < T _MAX1 )
I _{TEMP_DER1} = 0 (T _MAX1 < T ₁ )

3B shows a temperature derating characteristic based on a detection value _Ds2 representing a temperature _T2 . The parameter group _PRM2 includes four parameters, namely:
Derating start temperature T _S2
Derating end temperature T _E2
Decrease rate α ₂
Abnormality judgment temperature T _MAX2
The temperature derating characteristic is defined by four parameters including the above. The amount of current I _{TEMP_DER2} after derating is expressed by the following formula.
I _{TEMP_DER2} = I _BASE1 (T ₂ <T _S2 )
I _{TEMP_DER2} = I _BASE1 {1-α(T ₂ -T _S2 )} (T _S2 < T ₂ < T _E2 )
I _{TEMP_DER2} = I _BASE1 {1-α ₂ (T _E2 - _{T S2} )} (T _E2 < T ₂ < T _MAX2 )
I _{TEMP_DER2} = 0 (T _MAX2 < T ₂ )

The target current _IREF1 after considering both temperatures _T1 and _T2 is:
I _REF1 = min (I _{TEMP_DER1} , I _{TEMP_DER2} )
It becomes.

<Control Example 3>
In control example 3, the signal processing device 400 performs derating based on n=3 detection values Ds ₁ to Ds _3. The detection value Ds ₁ is a temperature detection value T ₁ based on the output of a first temperature sensor, the detection value Ds ₂ is a temperature detection value T ₂ based on the output of a second temperature sensor, and the detection value Ds ₃ is a voltage detection value V _DD representing a voltage. Three parameter groups are defined corresponding to the three detection values T ₁ , T ₂ , and V _DD . Each parameter group is as described in control examples 1 and 2. The signal processing device 400 calculates the three current amounts I _{TEMP_DER1} , I _{TEMP_DER2} , and I _{VOLT_DER} , and sets the minimum value min(I _{TEMP_DER1} , I _{TEMP_DER2} , I _{VOLT_DER} ) as the first target current I _REF1 .

(Embodiment 2)
In the first embodiment, the derating control for one light source has been described, but the present technology is not limited thereto and can also be applied to derating control for two or more light sources.

Figure 4 is a block diagram of the lighting system 100 according to the second embodiment. The configuration of the vehicle lamp 200 will be described, focusing on the differences from the first embodiment. The vehicle lamp 200 includes a first light source 202, a second light source 204, and a lamp control module 300. The first light source 202 is one of low beam (Lo), high beam (Hi), daytime running lamp (DRL), and position lamp (POS), and the second light source 204 can be another one of the light sources or a turn signal lamp.

A first lighting request REQ1 instructing the first light source 202 to be turned on or off and a first lighting request REQ2 instructing the second light source 204 to be turned on or off are supplied to the vehicle lamp 200 from the vehicle 110 via the vehicle bus 106.

The lamp control module 300 includes an A/D converter 306, a non-volatile memory 308, a bus interface circuit 320, a first drive circuit 330, and a second drive circuit 340.

The bus interface circuit 320 is a transceiver capable of bidirectional communication with the vehicle 110 via the vehicle bus 106. The data received by the bus interface circuit 320 includes a first lighting request REQ1 and a second lighting request REQ2.

The first drive circuit 330 generates a drive current I _LED1 stabilized to a first target current I _REF1 , and supplies the drive current I LED1 to the first light source 202. The first drive circuit 330 is configured to be able to set the first target current I _REF1 in response to a first control signal CNT1.

The second drive circuit 340 generates a drive current I _LED2 stabilized to a second target current I _REF2 and supplies the drive current I LED2 to the second light source 204. The second drive circuit 340 is configured to be able to set the second target current I _REF2 in response to a second control signal CNT2.

The signal processing device 400 enables the first drive circuit 330 in response to the lighting request REQ1. Then, it provides the first drive circuit 330 with a control signal CNT1 including the first target current _IREF1 calculated by the above-mentioned software processing. Also, it enables the second drive circuit 340 in response to the lighting request REQ2. Then, it provides the second drive circuit 340 with a control signal CNT2 including the second target current _IREF2 calculated by the above-mentioned software processing.

The non-volatile memory 308 stores at least one parameter group PRM _{1 to PRM n that defines a derating characteristic based on a base current value I BASE1 of the first drive current I LED1, a base current value I BASE2 of the second drive current I LED2, and at least one detection value Ds 1 to Ds n . The i - th (} 1≦i≦n) parameter group PRM _i defines a derating characteristic based on the corresponding i-th detection value Ds _i .

In this embodiment, the multiple parameter groups PRM ₁ to PRM _n are shared in the derating control of the two light sources (drive currents). The signal processing device 400 receives at least one detection value Ds ₁ to Ds _n and executes a software program to calculate a first target current I _REF1 in accordance with the base current value I _BASE1 and at least one parameter group PRM ₁ to PRM _n . The signal processing device 400 also receives at least one detection value Ds ₁ to Ds _n and executes a software program to calculate a second target current I _REF2 in accordance with the base current value I _BASE2 and at least one parameter group PRM ₁ to PRM _n .

An example of derating control in embodiment 2 is described below.

<Control Example 4>
In control example 4, the signal processing device 400 performs derating based on n=2 detected values Ds ₁ and Ds _2. The detected value Ds ₁ is a temperature detected value T based on the output of the temperature sensor, and the detected value Ds ₂ is a voltage detected value V _DD .

The parameter group describing the derating characteristics is as described in Control Example 1. The current amount _{I1_TEMP_DER} of the first drive current _ILED1 after derating is expressed by the following formula.
I _{1_TEMP_DER} = I _BASE1 (T<T _S )
I _{1_TEMP_DER} = I _BASE1 {1-α(T-T _S )} (T _S <T<T _E )
I _{1_TEMP_DER} = I _BASE1 {1-α(T _E -T _S )} (T _E < T < T _MAX )
I _{1_TEMP_DER} = 0 (T _MAX <T)

The amount of current after derating _{I1_VOLT_DER} is expressed by the following formula.
I _{1_VOLT_DER} =I _BASE1 (V _DD <V _S )
I _{1 _V OLT_DER} = I _BASE1 {1-β(V _DD -V _S )} (V _S <V _DD <V _E )
I _{1_VOLT_DER} = I _BASE1 {1-β(V _E -V _S )} (V _E <V _DD <V _MAX )
I _{1_VOLT_DER} = 0 (V _MAX < V _DD )

The first target current _IREF1 after considering both temperature and power supply voltage is:
I _REF1 = min (I _{1_TEMP_DER} , I _{1_VOLT_DER} )
It becomes.

The current amount _{I2_TEMP_DER} of the second drive current _ILED2 after temperature derating is expressed by the following formula.
_{I2_TEMP_DER} = _IBASE2 (T< _TS )
I _{2_TEMP_DER} =I _BASE2 {1-α(T-T _S )} (T _S <T<T _E )
I _{2_TEMP_DER} = I _BASE2 {1-α(T _E -T _S )} (T _E < T < T _MAX )
_{I2_TEMP_DER} =0 (T _MAX <T)

The amount of current _{I2_VOLT_DER} after voltage derating is expressed by the following formula.
I _{2_VOLT_DER} =I _BASE2 (V _DD <V _S )
I _{2 _V OLT_DER} = I _BASE2 {1-β(V _DD -V _S )} (V _S <V _DD <V _E )
I _{2_VOLT_DER} = I _BASE2 {1-β(V _E -V _S )} (V _E <V _DD <V _MAX )
I _{2_VOLT_DER} = 0 (V _MAX < V _DD )

The second target current _IREF2 after considering both temperature and power supply voltage is:
I _REF2 = min (I _{2_TEMP_DER} , I _{2_VOLT_DER} )
It becomes.

<Control Example 5>
In control example 5, the signal processing device 400 performs derating based on n=2 detection values _Ds1 and _Ds2 . The detection value _Ds1 is a temperature detection value _T1 based on the output of a first temperature sensor, and the detection value _Ds2 is a temperature detection value _T2 based on the output of a second temperature sensor.

The signal processor 400 calculates the following values related to the derating of the first light source 202:
I _{1_TEMP_DER1} = I _BASE1 (T ₁ <T _S1 )
I _{1_TEMP_DER1} = I _BASE1 {1-α ₁ (T ₁ -T _S1 )} (T _S1 < T ₁ < T _E1 )
I _{1_TEMP_DER1} = I _BASE1 {1-α ₁ (T _E1 - _{T S1} )} (T _E1 < T ₁ < T _MAX1 )
I _{1_TEMP_DER1} = 0 (T _MAX1 < T ₁ )
I _{1_TEMP_DER2} = I _BASE1 (T ₂ <T _S2 )
I _{1_TEMP_DER2} = I _BASE1 {1-α(T ₂ -T _S2 )} (T _S2 < T ₂ < T _E2 )
I _{1_TEMP_DER2} = I _BASE1 {1-α ₂ (T _E2 - _{T S2} )} (T _E2 < T ₂ < T _MAX2 )
I _{1_TEMP_DER2} = 0 (T _MAX2 < T ₂ )

The target current _IREF1 after considering both temperatures _T1 and _T2 is:
I _REF1 = min (I _{1_TEMP_DER1} , I _{1_TEMP_DER2} )
It becomes.

Similarly, the signal processor 400 calculates the following values related to the derating of the second light source 204:
I _{2_TEMP_DER1} = I _BASE2 (T ₁ <T _S1 )
I _{2_TEMP_DER1} = I _BASE2 {1-α ₁ (T ₁ -T _S1 )} (T _S1 < T ₁ < T _E1 )
I _{2_TEMP_DER1} = I _BASE2 {1-α ₁ (T _E1 - _{T S1} )} (T _E1 < T ₁ < T _MAX1 )
I _{2_TEMP_DER1} = 0 (T _MAX1 < T ₁ )
I _{2_TEMP_DER2} = I _BASE2 (T ₂ <T _S2 )
I _{2_TEMP_DER2} = I _BASE2 {1-α(T ₂ -T _S2 )} (T _S2 < T ₂ < T _E2 )
I _{2_TEMP_DER2} = I _BASE2 {1-α ₂ (T _E2 - _{T S2} )} (T _E2 < T ₂ < T _MAX2 )
I _{2_TEMP_DER2} = 0 (T _MAX2 < T ₂ )

The target current _IREF2 after considering both temperatures _T1 and _T2 is:
I _REF2 = min (I _{2_TEMP_DER1} , I _{2_TEMP_DER2} )
It becomes.

<Control Example 6>
In control example 6, similarly to control example 3, the signal processing device 400 performs derating based on n=3 detection values _Ds1 to _Ds3 . The detection value _Ds1 is a temperature detection value _T1 based on the output of the first temperature sensor, the detection value _Ds2 is a temperature detection value _T2 based on the output of the second temperature sensor, and the detection value _Ds3 is a voltage detection value V _DD representing the power supply voltage.

The signal processing device 400 calculates three current amounts _{I1_TEMP_DER1} , _{I1_TEMP_DER2} , and _{I1_VOLT_DER} in relation to the first light source 202, and sets the minimum value min( _{I1_TEMP_DER1} , _{I1_TEMP_DER2} , _{I1_VOLT_DER} ) among them as the first target current _IREF1 . Furthermore, the signal processing device 400A calculates three current amounts _{I2_TEMP_DER1} , _{I2_TEMP_DER2} , and _{I2_VOLT_DER} in relation to the second light source 204, and sets the minimum value min( _{I2_TEMP_DER1} , _{I2_TEMP_DER2} , _{I2_VOLT_DER} ) as the second target current _IREF2 .

Next, we will explain a more specific example configuration of the vehicle lamp 200.

5 is a block diagram showing a specific example of the configuration of the vehicle lamp 200A. The vehicle lamp 200A includes a lamp control module 300A and the first light source 202 to the fifth light source 210. As described above, the first light source 202 is for a turn signal lamp, and the second light source 204 is for both DRL and position lamp. The third light source 206 is for a low beam, the fourth light source 208 is for a high beam, and the fifth light source 210 is for SM .

The voltages and signals applied to the vehicle lamp 200A will be described.
+BLCM: Main power supply for vehicle lighting fixtures 200A (12V or 24V)
+VBU:
CAN-H, CAN-L: Vehicle bus IG1: Ignition status HL_BU:
TURN_SYNC: Turn synchronization signal

A power supply circuit 302 receives the voltage VBU and generates a power supply voltage V _DD of about 5 V. The power supply voltage V _DD is supplied to the microcontroller 390 and other circuits.

The protection circuit 305 includes a diode for preventing reverse polarity and a Zener diode for surge protection, and protects the vehicle lamp 200A from the main power supply voltage +BLCM.

The power supply circuit 304 is a step-up type DC/DC converter that steps up the power supply voltage +BLCM from the vehicle to generate a high power supply voltage _VDDH of, for example, about 40V.

Thermistors 220 and 222 are provided to monitor the temperatures of the third light source 206 and the second light source 204. A thermistor 224 is also provided on the circuit board of the lamp control module 300A.

The A/D converter 306 converts the voltages and currents of multiple nodes of the lamp control module 300A and the thermistor voltage into digital signals. In this example, one of the inputs of the A/D converter 306 is the output voltage of the power supply circuit 304, i.e., the input voltages of the first drive circuit 330 and the second drive circuit 340. The output ADC_OUT of the A/D converter 306 is supplied to the microcontroller 390. The microcontroller 390 incorporates the above-mentioned signal processing device 400 and non-volatile memory 308. The microcontroller 390 may incorporate the A/D converter 306.

The input interface circuit 310 receives the turn synchronization signal TURN_SYNC from the vehicle 110 via the direct line 104. The turn synchronization signal TURN_SYNC is a signal that instructs the turn signal lamp to blink, and when the turn signal lamp blinks, it becomes a pulse signal that alternates between high and low levels at a predetermined cycle, with the high section corresponding to lighting and the low section corresponding to turning off. When the turn signal lamp is not blinking (off state), the turn synchronization signal TURN_SYNC is fixed to low. The input interface circuit 310 may simply be a buffer, and shapes the turn synchronization signal TURN_SYNC.

(Turn signal lamp)
The first drive circuit 330 includes a constant current output step-down DC/DC converter 332 and generates a drive current I _LED1 . The step-down DC/DC converter 332 is supplied with an enable signal EN_BUCK1 and a dimming signal CURRENT_PWM1 as a control signal CNT1. The step-down DC/DC converter 332 is in an operating state when the enable signal EN_BUCK1 is asserted (e.g., high), and generates a drive current I _LED1 with a current amount according to the dimming signal CURRENT_PWM1. The dimming signal CURRENT_PWM1 is a PWM signal, and the controller IC of the step-down DC/DC converter 332 detects the duty cycle of the dimming signal CURRENT_PWM1 and changes the current amount of the drive current I _LED1 according to the duty cycle (analog dimming). That is, the target value _IREF1 of the driving current _ILED1 is set according to the duty cycle of the dimming signal CURRENT_PWM1. In order to blink the first light source 202 as described above, the signal processing device 400 switches the enable signal EN_BUCK1 according to the turn synchronization signal TURN_SYNC.

The DC/DC converter 332 transmits fail information and diagnostic information DC1_Diag to the signal processing device 400.

(DRL and position lamps)
In this embodiment, the second light source 204 and the third light source 206 are connected in series. The light sources 204 and 206 are driven by a common step-down DC/DC converter 342 and two bypass switches 344 and 354. The second light source 204 is driven by a second drive circuit 340 which is a combination of the step-down DC/DC converter 342 and the bypass switch 344.

The enable signal EN_BUCK2 and dimming signal CURRENT_PWM2 supplied to the step-down DC/DC converter 342, and the PWM signal DRL_PWM supplied to the bypass switch 344 correspond to the control signal CNT2 described above.

The step-down DC/DC converter 342 is in an operating state when the enable signal EN_BUCK2 is asserted (e.g., high), and generates a drive current I _DRV having a current amount according to the dimming signal CURRENT_PWM2. The dimming signal CURRENT_PWM2 is a PWM signal, and the controller IC of the step-down DC/DC converter 342 changes the current amount of the drive current I _DRV according to the duty cycle of the dimming signal CURRENT_PWM2 (analog dimming).

The on/off of the bypass switch 344 is controlled by a PWM signal DRL_PWM. When the bypass switch 344 is off, the drive current I _DRV is supplied to the second light source 204, and when the bypass switch 344 is on, the drive current I _DRV is not supplied to the second light source 204. By changing the PWM signal DRL_PWM, the signal processing device 400 can change the average value of the drive current I _LED2 supplied to the second light source 204 and change the effective luminance of the second light source 204.

For example, the signal processing device 400 changes the duty cycle of the PWM signal DRL_PWM according to the table value VAL, thereby changing the brightness of the second light source 204 and switching between the functions of the DRL and the position lamp.

(Low beam)
The combination of the step-down DC/DC converter 342 and the bypass switch 354 is understood to be a third drive circuit 350 that drives the third light source 206. The bypass switch 354 is controlled to be turned on and off in response to the Lo_PWM signal.

The DC/DC converter 342 transmits fail information and diagnostic information DC2_Diag to the signal processing device 400.

(High beam)
The fourth drive circuit 360 that drives the fourth light source 208 includes a step-down DC/DC converter 362. The step-down DC/DC converter 362 is in an operating state when the enable signal EN_BUCK3 is asserted (e.g., high), and generates a drive current I _LED4 having a current amount according to the dimming signal CURRENT_PWM4. The dimming signal CURRENT_PWM4 is a PWM signal, and the controller IC of the step-down DC/DC converter 362 changes the current amount of the drive current I _LED4 according to the duty cycle of the dimming signal CURRENT_PWM4 (analog dimming).

The high beam may be an ADB (Adaptive Driving Beam) lamp. In this case, the multiple LEDs constituting the fourth light source 208 for the high beam may be configured so that they can be individually controlled to be turned on and off. Specifically, a bypass switch may be provided for each LED chip, and the bypass switch in parallel with the LED corresponding to the light-blocking area may be controlled to be turned on.

(S.M.)
The fifth drive circuit 370 is controlled to be turned on or off in response to a control signal IPD1_On, and in the on state, supplies a drive current I _LED5 to the fifth light source 210 to turn on the fifth light source 210 .

The derating control in the vehicular lamp 200A of Fig. 5 will now be described. The microcontroller 390 performs the derating control based on the outputs of the thermistors 220, 222, and 224 (i.e., temperature information) and the detection value indicating the voltage V _DDH .

For example, for the second light source 204 for DRL/POS, the drive current I _LED2 may be derated based on three detection values based on the input voltage V _DDH of the second drive circuit 340 , the output of the thermistor 222 , and the output of thermistor 224 .

Furthermore, for the third light source 206 for low beam, the drive current I _LED3 may be derated based on three detection values based on the input voltage V _DDH of the drive circuit 350 , the output of the thermistor 220 , and the output of thermistor 224 .

Furthermore, for the first light source 202 for the turn signal lamp, the drive current I _LED1 may be derated based on two detection values based on the input voltage V _DDH of the drive circuit 330 and the output of the thermistor 224 .

Furthermore, for the fourth light source 208 for high beam, the drive current I _LED4 may be derated based on two detection values based on the input voltage V _DDH of the drive circuit 360 and the output of the thermistor 224 .

In this case, a group of parameters that specifies the derating for voltage V _DDH , a group of parameters that specifies the derating for thermistor 220, a group of parameters that specifies the derating for thermistor 222, and a group of parameters that specifies the derating for thermistor 224 may be written into non-volatile memory 308.

The present invention has been described above based on an embodiment. This embodiment is merely an example, and those skilled in the art will understand that various modifications are possible in the combination of each component and each processing process, and that such modifications are also within the scope of the present invention. Below, such modifications are described.

In the vehicle lamp 200A of FIG. 5, the power supply circuit 304 may be omitted, and the DC/DC converters 342, 332, and 352 may be configured as boost converters.

In the vehicle lamp 200A of FIG. 5, the second light source 204 and the third light source 206 are driven by a common converter, but this is not limited thereto, and the second light source 204 and the third light source 206 may be driven by separate converters.

The parameters that define the derating characteristics are not limited to those described above, and may be defined so that the derating characteristics are uniquely determined. Furthermore, the shape of the derating characteristics is not limited to those described above, and may be expressed using a quadratic function or other functions.

In the embodiment, the components of the lamp control module 300 are modularized by being housed in the same housing, but this is not limited thereto, and the components may be divided into multiple housings, packages, modules, or boards.

The present invention has been described using specific terms based on the embodiments, but the embodiments merely show the principles and applications of the present invention, and many modifications and changes in arrangement are permitted to the embodiments as long as they do not deviate from the concept of the present invention as defined in the claims.

100...lighting system, 102...power line, 104...Zika line, 106...vehicle bus, 110...vehicle, 200...vehicle lamp, 202...first light source, 204...second light source, 206...third light source, 208...fourth light source, 210...fifth light source, 300...lamp control module, 302, 304...power supply circuit, 305...protection circuit, 306...A/D converter, 310...input interface circuit, 320...bus interface circuit, 330...first drive circuit, 340...second drive circuit, 350...third drive circuit, 360...fourth drive circuit, 370...fifth drive circuit, 390...microcontroller, 400...signal processing device.

Claims (9)

A vehicle lamp,
A first light source;
a first drive circuit that supplies a first drive current stabilized to a first target current _IREF1 to the first light source;
an A/D converter that receives at least one electrical signal indicating a state of the vehicle lamp and generates at least one detection value corresponding to the at least one electrical signal;
(i) a base current value I _BASE1 of the first drive current; and (ii) a non-volatile memory that stores at least one parameter group that defines a derating characteristic of the first light source based on each of the at least one detection value.
a signal processor configured to receive the at least one detected value and to execute a software program to calculate the first target current _IREF1 in response to the base current value _IBASE1 and the at least one parameter set;
and by changing values of a group of parameters to be written to the non-volatile memory, the derating characteristic can be changed without changing the software program. The at least one detection value is
a temperature detection value T based on the output of a temperature sensor;
a voltage detection value V _DD based on an input voltage of the first drive circuit;
Including,
The parameter group related to the temperature detection value T includes a derating start temperature T _S , a derating end temperature T _E , and a reduction rate α,
The parameter group related to the voltage detection value V _DD includes a derating start voltage V _S , a derating end voltage V _E , and a reduction rate β,
The signal processing device calculates a current amount I _{TEMP_DER} after derating related to the temperature detection value T as follows:
I _{TEMP_DER} = I _BASE1 (T<T _S )
I _{TEMP_DER} = I _BASE1 {1-α(T-T _S )} (T _S <T<T _E )
I _{TEMP_DER} =I _BASE1 {1-α(T _E -T _S )} (T _E <T)
Calculate based on
The amount of current I _{VOLT_DER} after derating regarding the voltage detection value V _DD is defined as:
I _{VOLT_DER} = I _BASE1 (V _DD <V _S )
I _{VOLT_DER} = I _BASE1 {1-β(V _DD -V _S )} (V _S <V _DD <V _E )
I _{VOLT_DER} = I _BASE1 {1-β(V _E -V _S )} (V _E <V _DD )
2. The vehicular lamp according to claim 1, wherein the first target current IREF1 is calculated based on the current amounts _{ITEMP_DER} and _{IVOLT_DER} , whichever is smaller, and the first target current IREF1 is determined as the first target current _IREF1 . The parameter group related to the temperature detection value T further includes an abnormality determination temperature T _MAX ,
3. The vehicular lamp according to claim 2, wherein the signal processing device sets I _{TEMP_DER} =0 in a range of T _MAX <T. The at least one detection value is
a temperature detection value _T1 based on an output of a first temperature sensor;
a temperature detection value _T2 based on the output of the second temperature sensor;
Including,
The parameter group related to the temperature detection value _T1 includes a derating start temperature T _S1 , a derating end temperature T _E1 , and a reduction rate α ₁ ,
The parameter group related to the temperature detection value _T2 includes a derating start temperature T _S2 , a derating end temperature T _E2 , and a reduction rate α ₂ ,
The signal processing device calculates a current amount I _{TEMP_DER1} after derating for the temperature detection value _T1 as follows:
I _{TEMP_DER1} = I _BASE1 (T ₁ <T _S1 )
I _{TEMP_DER1} = I _BASE1 {1-α ₁ (T ₁ -T _S1 )} (T _S1 < T ₁ < T _E1 )
I _{TEMP_DER1} = I _BASE1 {1-α ₁ (T _E1 - _{T S1} )} (T _E1 < T ₁ )
Calculate based on
The amount of current I _{TEMP_DER2} after derating for the temperature detection value _T2 is defined as
I _{TEMP_DER2} = I _BASE1 (T ₂ <T _S2 )
I _{TEMP_DER2} = I _BASE1 {1-α ₂ (T ₂ -T _S2 )} (T _S2 < T ₂ < T _E2 )
I _{TEMP_DER2} = I _BASE1 {1-α ₂ (T _E2 - _{T S2} )} (T _E2 < T ₂ )
2. The vehicular lamp according to claim 1, wherein the first target current _IREF1 is calculated based on the current amounts _{ITEMP_DER1} and _{ITEMP_DER2} , whichever is smaller. The at least one detection value is
a temperature detection value _T1 based on an output of a first temperature sensor;
a temperature detection value _T2 based on the output of the second temperature sensor;
a voltage detection value V _DD based on an input voltage of the first drive circuit;
Including,
The parameter group related to the temperature detection value _T1 includes a derating start temperature T _S1 , a derating end temperature T _E1 , and a reduction rate α ₁ ,
The parameter group related to the temperature detection value _T2 includes a derating start temperature T _S2 , a derating end temperature T _E2 , and a reduction rate α ₂ ,
The parameter group related to the voltage detection value V _DD includes a derating start voltage V _S , a derating end voltage V _E , and a reduction rate β,
The signal processing device calculates a current amount I _{TEMP_DER1} after derating for the temperature detection value _T1 as follows:
I _{TEMP_DER1} = I _BASE1 (T ₁ <T _S1 )
I _{TEMP_DER1} = I _BASE1 {1-α ₁ (T ₁ -T _S1 )} (T _S1 < T ₁ < T _E1 )
I _{TEMP_DER1} = I _BASE1 {1-α ₁ (T _E1 - _{T S1} )} (T _E1 < T ₁ )
Calculate based on
The amount of current I _{TEMP_DER2} after derating for the temperature detection value _T2 is defined as
I _{TEMP_DER2} = I _BASE1 (T ₂ <T _S2 )
I _{TEMP_DER2} = I _BASE1 {1-α ₂ (T ₂ -T _S2 )} (T _S2 < T ₂ < T _E2 )
I _{TEMP_DER2} = I _BASE1 {1-α ₂ (T _E2 - _{T S2} )} (T _E2 < T ₂ )
Calculate based on
The amount of current I _{VOLT_DER} after derating regarding the voltage detection value V _DD is defined as:
I _{VOLT_DER} = I _BASE1 (V _DD <V _S )
I _{VOLT_DER} = I _BASE1 {1-β(V _DD -V _S )} (V _S <V _DD <V _E )
I _{VOLT_DER} = I _BASE1 {1-β(V _E -V _S )} (V _E <V _DD )
2. The vehicular lamp according to claim 1, wherein the first target current _IREF1 is calculated based on the current amounts _{ITEMP_DER1} , _{ITEMP_DER2} , and _{IVOLT_DER} , and the smallest one of the current amounts ITEMP_DER1, ITEMP_DER2, and IVOLT_DER is set as the first target current IREF1. The parameter group related to the temperature detection value _T1 further includes an abnormality determination temperature _TMAX1 ,
The parameter group related to the temperature detection value _T2 further includes an abnormality determination temperature _TMAX2 ,
6. The vehicular lamp according to claim 4, wherein the signal processing device sets I _{TEMP_DER1} =0 in a range of T _MAX1 < _T1 , and sets I _{TEMP_DER2} =0 in a range of T _MAX2 < _T2 . the first drive circuit, the A/D converter, the non-volatile memory, and the signal processing device are configured as a single module;
the first temperature sensor is provided inside the module,
7. The vehicular lamp according to claim 5, wherein the second temperature sensor is provided outside the module. A second light source;
a second drive circuit that supplies a second drive current stabilized to a second target current _IREF2 to the second light source;
Further equipped with
the non-volatile memory further stores a base current value I _BASE2 of the second drive current;
8. The vehicular lamp according to claim 1, wherein the signal processor calculates the second target current _IREF2 in response to the base current value _IBASE2 and the at least one parameter group. A lamp control module for use in a vehicle lamp having a first light source,
a first drive circuit that supplies a first drive current stabilized to a first target current _IREF1 to the first light source;
an A/D converter that receives at least one electrical signal indicating a state of the vehicle lamp and generates at least one detection value corresponding to the at least one electrical signal;
(i) a base current value I _BASE1 of the first drive current; and (ii) a non-volatile memory that stores at least one parameter group that defines a derating characteristic of the first light source based on each of the at least one detection value.
a signal processor configured to receive the at least one detected value and to execute a software program to calculate the first target current _IREF1 in response to the base current value _IBASE1 and the at least one parameter set;
and wherein the derating characteristic can be changed by changing the values of a group of parameters to be written to the non-volatile memory, without changing the software program.

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