JP6330439B2 - Lighting control device - Google Patents

Description

  The present invention relates to an illumination control device that controls lighting of a light emitting element such as an LED.

  2. Description of the Related Art Conventionally, an illumination control device that uses a switching power supply to control lighting of a light emitting element such as an LED has been used.

  In this type of lighting control device, when the switching power supply starts operating when the LED is turned off, the voltage applied to the LED gradually increases, and when the voltage reaches a predetermined emission start voltage for the LED, the LED is turned on. Forward current begins to flow.

  When the voltage applied to the LED reaches the light emission start voltage, the LED has a property that the forward current flowing through the LED increases by an amount corresponding to the increase rate corresponding to the rate of increase of the voltage applied until then. There is.

In the illumination control device, feedback control is performed so that the forward current becomes the target value. Therefore, even if the forward current of the LED exceeds the target value, the forward current of the LED reaches the target value.

  As a result, when the LED switches from the off state to the on state, a flash is generated from the LED for a moment, and then the LED settles to a predetermined ambient illuminance.

  In order to suppress the occurrence of such a phenomenon, the LED lighting device described in Patent Document 1 uses a switching power supply until the applied voltage to the LED reaches a threshold value smaller than the light emission start voltage of the LED. It is operated with a pulse signal having a larger duty ratio than after reaching the threshold value.

  On the other hand, after the applied voltage to the LED reaches the threshold value, the switching power supply is operated with a pulse signal having a smaller duty ratio than that until the applied voltage reaches the threshold value until the light emission start voltage is reached.

  As a result, during the period from when the LED applied voltage reaches the threshold value until the light emission start voltage is reached, the rate of increase in the voltage applied to the LED is increased, and the voltage applied until the LED applied voltage reaches the threshold value is increased. Suppress than rate.

  As a result, since the forward current rise when the applied voltage of the LED reaches the light emission start voltage is suppressed, the generation of flash when the LED switches from the off state to the on state is suppressed.

JP 2013-69766 A

  The LED has a property that the light emission start voltage increases as the ambient temperature of the LED decreases, and the light emission start voltage decreases as the ambient temperature of the LED increases.

  In the LED lighting circuit described in Patent Document 1, the rate of increase of the applied voltage is controlled based only on the voltage applied to the LED, regardless of the ambient temperature of the LED. Therefore, for example, the voltage may be applied to the LED at the same rate of increase both at a low temperature when the light emission start voltage increases and at a high temperature when the light emission start voltage decreases.

  When the applied voltage is increased at the same rate of increase both at low temperatures and at high temperatures, the light emission start voltage increases at low temperatures, so it may take time until the LED emits light. On the other hand, since the light emission start voltage decreases at high temperatures, the increase rate of the applied voltage exceeds the increase rate corresponding to the temperature at that time, and flashing may occur when the LED starts to emit light.

  When the LED is used in an in-vehicle device, for example, a HUD (Head-Up Display) device, the range of the ambient temperature of the LED is as large as approximately −40 ° C. to 85 ° C. In such a case, unless the LED is controlled based on the ambient temperature of the LED, the above-described problem becomes significant.

  The present invention has been made under the above circumstances, and provides a lighting control device capable of performing appropriate lighting control according to the ambient temperature even when the ambient temperature range of the light emitting element is wide. Objective.

In order to achieve the above object, an illumination control device according to the present invention includes:
A light emitting element;
A switching power supply unit that applies a DC voltage to the light emitting element by receiving a pulse signal and performing a switching operation;
A temperature measuring unit for measuring the ambient temperature of the light emitting element;
A first storage unit storing ambient temperature information that is information related to the ambient temperature of the light emitting element, and first duty ratio information that is information related to the first duty ratio according to the ambient temperature;
A parameter other than the ambient temperature, a second storage unit which stores information of the second pulse signal which represents the relationship between the second duty ratio corresponding to this parameter,
When the light emitting element is switched from the off state to the on state, the first duty ratio according to the ambient temperature measured by the temperature measuring unit is determined with reference to the first storage unit, and the determination is made. as a pulse signal of a first duty ratio first pulse signal, the output to the switching power supply unit, and a control unit for the switching power supply unit controls the DC voltage applied to the light emitting element,
With
The control unit discriminates the first duty ratio and the second duty ratio with reference to the first storage unit and the second storage unit, respectively, and the first duty ratio and the second duty ratio, respectively. The pulse signal having a duty ratio whichever is greater than the ratio is output to the switching power supply unit.
Moreover, the illumination control device according to the present invention includes:
A light emitting element;
A switching power supply unit that applies a DC voltage to the light emitting element by receiving a pulse signal and performing a switching operation;
A temperature measuring unit for measuring the ambient temperature of the light emitting element;
A first storage unit storing ambient temperature information that is information related to the ambient temperature of the light emitting element, and first duty ratio information that is information related to the first duty ratio according to the ambient temperature;
When the light emitting element is switched from the off state to the on state, the first duty ratio according to the ambient temperature measured by the temperature measuring unit is determined with reference to the first storage unit, and the determination is made. After outputting the pulse signal of the first duty ratio as the first pulse signal to the switching power supply unit,
A second pulse signal having a duty ratio corresponding to parameters other than the ambient temperature, by outputting to the switching power supply unit, and a control section for controlling the DC voltage the switching power supply unit is applied to the light emitting element,
With
The first duty ratio information is information representing an ON period of the pulse signal according to the ambient temperature,
The first pulse signal and the second pulse signal have the same period,
The control unit supplies, to the switching power supply unit, the pulse signal having the divided ON period obtained by dividing the ON period as a plurality of the first duty ratio as the first pulse signal by the divided number. It is characterized by outputting.

  According to the present invention, even when the ambient temperature range of the light emitting element is wide, appropriate lighting control according to the ambient temperature can be performed.

It is a conceptual diagram which shows how the mounting aspect to a vehicle of a HUD apparatus provided with the illumination control apparatus which concerns on one Embodiment of this invention, and a virtual image are imaged. It is a schematic block diagram of a HUD apparatus. It is a circuit diagram showing an example of the basic composition of the lighting control device concerning one embodiment of the present invention. It is a figure showing the relationship between the ambient temperature of LED, and the light emission start voltage. It is a figure showing the relationship between ambient temperature of LED, and the light emission start ON period according to ambient temperature. It is the flowchart which showed an example of the basic operation | movement of the illumination control apparatus shown in FIG. It is a timing chart for demonstrating the basic operation | movement of the illumination control apparatus shown in FIG. It is a timing chart for demonstrating operation | movement of the conventional illumination control apparatus. It is a circuit diagram showing the other example of the basic composition of the illumination control apparatus which concerns on one Embodiment of this invention. It is the flowchart which showed an example of the basic operation | movement of the illumination control apparatus of FIG. It is a circuit diagram showing the further another example of the basic composition of the illumination control apparatus which concerns on one Embodiment of this invention. It is a timing chart for demonstrating the basic operation | movement of the illumination control apparatus of FIG.

  Hereinafter, an illumination control device according to an embodiment of the present invention will be described with reference to the drawings.

  The lighting control apparatus 100 (see FIG. 3) according to the present embodiment is a HUD (Head-Up Display) that displays vehicle information such as vehicle speed and engine speed on a windshield (windshield) 3 of the vehicle 2. The lighting of the light source in the apparatus 1 is controlled.

  The HUD device 1 is provided in the dashboard of the vehicle 2, and reflects the light (display light L) representing the display image for notifying the vehicle information by the windshield 3, thereby converting the virtual image V of the display image into the user 4. (Mainly the driver of the vehicle 2). Thereby, the user 4 can recognize vehicle information such as the vehicle speed and the engine speed without diverting his line of sight from the front during driving.

  As shown in FIG. 2, the HUD device 1 includes a liquid crystal display device 10, an optical system 20, a circuit board 40 including an illumination control device 100, and a housing 50.

  The liquid crystal display device 10 displays a display image for notifying vehicle information. That is, the liquid crystal display device 10 emits light representing the display image (display light L). The liquid crystal display device 10 is composed of, for example, a known transmissive liquid crystal display device.

  The liquid crystal display device 10 includes a light emitting element for illuminating the liquid crystal panel from the back side, for example, one or a plurality of LEDs (Light Emitting Diodes). The liquid crystal display device 10 emits light (display light L) representing a display image by the emitted light of the LED. In order to maintain the visibility of the displayed image, the LED needs to have a higher luminance as the surrounding environment becomes brighter (the higher the ambient illuminance).

  The optical system 20 is provided in the optical path between the liquid crystal display device 10 and the windshield 3 so that the display image of the liquid crystal display device 10 is formed as a virtual image V at a desired position and in a desired size. The optical system 20 according to this embodiment includes two reflecting members, a plane mirror 21 and a concave mirror 22.

  The plane mirror 21 is arranged at a position for receiving the display light L from the liquid crystal display device 10 and reflects the incident display light L toward the concave mirror 22. The concave mirror 22 emits the reflected light toward the windshield 3 by reflecting the display light L reflected by the plane mirror 21 on the concave surface. As a result, the size of the virtual image V to be connected becomes a size obtained by enlarging the display image.

  The circuit board 40 is a printed circuit board in which a predetermined wiring pattern is formed on a plate-like base material made of a resin containing glass fiber. The circuit board 40 is disposed, for example, on the side opposite to the display light L emission side of the liquid crystal display device 10. On the circuit board 40, the illumination control device 100 and LEDs are mounted. Note that the illumination control device 100 and the LED may be mounted on the same substrate, or each may be mounted on a separate substrate, and each substrate may be connected by a harness or the like.

  As shown in FIG. 3, the illumination control device 100 includes a control unit 101, an LED drive circuit (switching power supply unit) 102, an LED 103, a temperature detection circuit (temperature detection unit) 104, and an illuminance sensor (illuminance measurement unit). 105 and first and second storage units 106a and 106b.

  The control unit 101 comprehensively controls the illumination control device 100. The control unit 101 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and the like, and is realized by the CPU executing a predetermined control program.

  The control unit 101 acquires various types of vehicle information from a vehicle ECU (Electronic Control Unit). The various types of vehicle information include information indicating whether the ignition signal is on or off.

  The control unit 101 causes the LED drive circuit 102 to perform a switching operation. The control unit 101 causes the LED drive circuit 102 to perform a dimming control signal to control the LED 103 and a reference voltage indicating a reference value (target value) of a current flowing through the LED 103 (PWM signal) is output. In addition, in order to control the switching operation of the LED drive circuit 102, the illuminance information from the illuminance sensor 105 and the temperature information from the temperature detection circuit 104 are received.

  The control unit 101 includes a reference voltage port P1 that outputs a reference voltage to the differential amplifier 102c, and a dimming signal port P2 that outputs a dimming signal to the AND circuit 102e and the knot circuit 102n. The control unit 101 also includes an illuminance information port P3 that receives a voltage signal that represents the ambient illuminance of the HUD device 1 and a temperature information port P4 that receives a voltage signal that represents the ambient temperature of the LED 103.

  The control unit 101 converts the voltage received at the temperature information port P4 into ambient temperature, and converts the voltage received at the illuminance information port P3 into ambient illuminance. For this purpose, the control unit 101 stores information indicating the relationship between the voltage and the ambient temperature and information indicating the relationship between the voltage and the ambient illuminance in the RAM or ROM of the controller 101.

  Furthermore, a first storage unit 106 a and a second storage unit 106 b are connected to the control unit 101. The first storage unit 106a stores information representing the relationship between the ambient temperature detected by the temperature detection circuit 104 and the first duty ratio. The second storage unit 106b stores information representing the relationship between the ambient illuminance of the HUD device 1 detected by the illuminance sensor 105 and the second duty ratio. The control unit 101 determines the first duty ratio from the ambient temperature, and determines the second duty ratio from the ambient illuminance.

  Here, the second duty ratio is a duty ratio that the dimming signal should take in order to control the effective applied voltage of the LED 103 according to the ambient illuminance of the HUD device 1 detected by the illuminance sensor 105. On the other hand, the first duty ratio is a duty ratio that should be taken by the dimming signal so as to quickly switch to the lighting state without causing flashing according to the ambient temperature of the LED 103 when the LED 103 is activated. Information representing the relationship between the ambient temperature and the first duty ratio and information representing the relationship between the ambient illuminance and the second duty ratio are set based on, for example, experiments and simulations.

  The LED drive circuit 102 includes, for example, a switching regulator type LED driver IC (Integrated Circuit). The LED driving circuit 102 converts the input DC voltage V <b> 1 into a DC voltage having a target voltage value by a switching operation, and applies the DC voltage to the LED 103.

  The LED driving circuit 102 includes a resistor 102a, a P-channel MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) 102j, an inductor 102g, a Schottky barrier diode 102h, a capacitor 102i, an NPN transistor TR, and a resistor 102m. Differential amplifiers 102b to 102d, an AND circuit 102e, a PWM signal generation unit 102f, a knot circuit 102n, and an amplifier 102o.

  The resistor 102a is a current detection resistor for detecting the current flowing through the LED 103, and one end of the resistor 102a is connected to the DC voltage source (for example, battery) V1 via the resistor 109.

  The P-channel MOSFET 102j functions as a first switching circuit SW1 that turns on and off the current path of the LED 103. The drain of the P-channel MOSFET 102j is connected to the anode of the LED 103, the gate of the P-channel MOSFET 102j is connected to the output terminal of the amplifier 102o, and the source of the P-channel MOSFET 102j is connected to the other end of the resistor 102a. The first switching circuit SW1 is turned on / off in a relatively long cycle in response to the voltage level of the inverted signal of the dimming signal (PWM signal) output from the control unit 101.

  The first switching circuit SW1 includes a varistor 102l connected between the gate and source of the P-channel MOSFET 102j. The varistor 102l protects the P-channel MOSFET 102j from static electricity and surge voltage. The diode 102k is a parasitic diode of the P-channel MOSFET 102j.

  The LED 103 is an element that includes a PN junction surface and emits light when the PN junction surface is energized. The anode of the LED 103 is connected to the drain of the P-channel MOSFET 102j, and the cathode is connected to one end of the inductor 102g and the capacitor 102i.

  The inductor 102g is a switching inductor, and one end thereof is connected to the cathode of the LED 103 and one end of the capacitor 102i.

  The Schottky barrier diode 102h has an anode connected to the other end of the inductor 102g, and a cathode connected to one end of the resistor 102a and the other end of the capacitor 102i, and functions as a freewheeling diode. The Schottky barrier diode 102h is used for high-speed switching, and is not limited to a Schottky barrier diode, and a fast recovery diode may be used.

  The capacitor 102i has one end connected to one end of the inductor 102g and the other end connected to the cathode of the Schottky barrier diode 102h, and has a function of stabilizing (smoothing) the cathode voltage of the LED.

  The transistor TR is composed of an NPN type transistor, and its collector is connected to a connection node between the other end of the inductor 102g and the anode of the Schottky barrier diode 102h, and is grounded through the resistor 102m. , And connected to the output terminal of the AND circuit 102e.

  The transistor TR is turned on when the signal level of the output signal of the AND circuit 102e is high, and turned off when the signal level is low. The transistor TR switches at a relatively high speed while the first switching circuit SW1 is on. Thus, the second switching circuit SW2 that controls the current flowing through the LED 103 functions.

  The differential amplifier 102d is a circuit that amplifies the voltage drop at the resistor 102m and outputs it as a bias voltage to the PWM signal generator 102f, and its non-inverting input terminal (+) is connected to the positive terminal of the resistor 102m. The inverting input terminal (−) is connected to the negative terminal of the resistor 102m, and the output terminal is connected to the bias input terminal of the PWM signal generation unit 102f.

  The differential amplifier 102b is a circuit that detects an actual current flowing through the LED 103, and its non-inverting input terminal (+) is connected to one end (plus-side terminal) of the resistor 102a, and its inverting input terminal (−) is a resistance. It is connected to the other end (terminal on the negative side) of 102a.

  The differential amplifier 102c is an error amplifier that calculates a deviation ε between the actual current flowing through the LED 103 indicated by the voltage signal output from the differential amplifier 102b and the reference current value (target current value) indicated by the reference voltage output from the control unit 101. It is. The inverting input terminal (−) of the differential amplifier 102c is connected to the output terminal of the differential amplifier 102b, its non-inverting input terminal (+) is connected to the reference voltage port P1 of the control unit 101, and its output terminal is The PWM signal generator 102f is connected to the deviation input terminal.

  The PWM signal generation unit 102f is a circuit that generates and outputs a PWM signal for switching the second switching circuit SW2 at a relatively high speed. More specifically, the PWM signal generation unit 102f controls the duty so that the deviation ε becomes zero based on the deviation ε output from the differential amplifier 102c and the bias voltage output from the differential amplifier 102d. The generated relatively high frequency PWM signal is output to one input terminal of the AND circuit 102e.

  The AND circuit 102e is a circuit that generates a control signal for switching the second switching circuit SW2 at high speed while the first switching circuit SW1 is on. The AND circuit 102e and the PWM signal output from the PWM signal generation unit 102f The logical product with the dimming signal output from the control unit 101 is obtained and applied to the base of the NPN transistor TR.

  The knot circuit 102n inverts the signal level of the dimming signal from the dimming signal port P2, and outputs it to the input terminal of the amplifier 102o. The amplifier 102o amplifies the dimming signal whose level has been inverted by the knot circuit 102n, and applies it to the gate of the P-channel MOSFET 102j constituting the first switching circuit SW1.

  The temperature detection circuit 104 includes a series circuit of a resistor 104a and a thermistor 104b connected between a DC voltage source (for example, a battery) V2 and the ground. The temperature detection circuit 104 outputs the divided voltage by the resistor 104a and the thermistor 104b to the temperature information port P4 as temperature information indicating the ambient temperature of the LED 103.

  The illuminance sensor 105 measures the ambient illuminance of the HUD device 1 and inputs a voltage signal corresponding to the measured ambient illuminance as illuminance information to the illuminance information port P3.

  A dimming signal output from the control unit 101 will be described.

  The dimming signal is a PWM signal. When the PWM signal is at a high level, the first switching circuit SW1 (P-channel MOS transistor 102j) is turned on, and the current path of the LED 103 is conducted. During the period when the first switching circuit SW1 is on, the second switching circuit SW2 is controlled to switch at high speed so that a current flows through the LED 103.

  The duty of the dimming signal is basically determined by the ambient (environment) illuminance in the usage environment. The brighter the surroundings, the greater the duty ratio. This is because the brightness of the LED of the HUD device 1 needs to be increased as the surroundings become brighter. The relationship between the ambient illuminance of the HUD device 1 and the duty ratio is obtained in advance through experiments or the like and stored in the second storage unit 106b. The control unit 101 obtains a second duty corresponding to the ambient illuminance obtained by the illuminance sensor 105 from the second storage unit 106b, and outputs a dimming signal having the obtained second duty ratio.

  On the other hand, as described in the section of the prior art, as shown in FIG. 4, the LED 103 has a light emission start voltage (Vf) that increases as the ambient temperature (Temp) decreases, and a light emission start voltage that increases as the ambient temperature increases. It has the property of being small. That is, the LED 103 is less likely to be lit as the ambient temperature is lower, and is more likely to be lit as the temperature is higher.

  For this reason, when the LED 103 is activated, it is necessary to perform control to change the rate of increase in the applied voltage of the LED 103 according to the ambient temperature of the LED 103.

  In order to enable this control, as shown in FIG. 5, a plurality of ambient temperature information representing the ambient temperature and the dimming according to each ambient temperature are stored in the first storage unit 106a as the first pulse signal information. Information on the regression line LI representing the relationship with the light emission start ON period information (hereinafter referred to as ON period information) representing the light emission start ON period (hereinafter referred to as ON period) which is the ON period of the signal is stored.

  In order to simplify subsequent calculations, the unit of the light emission start ON period is expressed as a percentage, where one cycle of the dimming signal is 100%.

  Here, the ON period means an ON period of a dimming signal necessary until the LED 103 starts to emit light at a certain ambient temperature, and the ON period information is a first duty ratio corresponding to each ambient temperature. Is stored in the form of a regression line LI as the relationship with each ambient temperature information.

  The first duty ratio is, for example, a value obtained by dividing the ON period represented by the ON period information by a numerical value of 2 or more (for example, a natural number of 2 or more (2, 3, 4,...)). It is a duty ratio. For example, when the result obtained by dividing the ON period obtained by applying the ambient temperature to the regression line LI by 2 is used as the first duty ratio, the dimming signal having the first duty ratio is applied twice, thereby Can be met.

  The relationship shown in FIG. 5 is that the ambient temperature range of the LED is set within a range of approximately −40 ° C. to 90 ° C. in consideration of the use environment of the HUD device 1, and no flash is generated from the LED 103. The ON period of the dimming signal that can be quickly and smoothly switched to the lighting state is obtained by experiment.

The points plotted in FIG. 5 represent an appropriate ON period according to the ambient temperature. The regression line LI is obtained by the present inventor by offsetting each ON period on average about 10% for a plurality of plotted points.

Since the regression line LI represents the relationship between the ambient temperature and the ON period, if the ambient temperature is known, the ON period during which the LED 103 can be appropriately switched to the lighting state is known. Here, the set 10% is set so that the regression line LI obtained by linearly approximating and offsetting a plurality of plotted points does not exceed the ON period of each plotted point in the entire temperature range. The offset value is not limited to 10%.

  Although not shown, the second storage unit 106b stores information on a regression line representing the relationship between the ambient illuminance of the HUD device 1 and the second duty ratio as the second pulse signal information. Based on this information, a second duty ratio corresponding to the ambient illuminance is set in advance.

Hereinafter, the illumination control operation by the control unit 101 will be described with reference to FIGS. 3 and 6 to 8.
When the ignition switch is turned on, a power supply voltage is supplied to each unit, and the control unit 101, the temperature detection circuit 104, the illuminance sensor 105, and the like start operating.

  The temperature detection circuit 104 has a divided voltage of [{R2 / (R1 + R2)} × V2] where the DC voltage value of the DC current source V2 is V2, the resistance value of the resistor 104a is R1, and the resistance value of the thermistor 104b is R2. Is applied to the temperature information port P4. The illuminance sensor 105 applies a voltage signal corresponding to the ambient illuminance of the HUD device 1 to the illuminance information port P3.

  On the other hand, in response to the supply of power, the control unit 101 executes a predetermined initialization process, and then executes a dimming signal generation / output process shown in the flowchart of FIG. 6 to output a dimming signal. The dimming signal generation / output process will be described with reference to the timing charts of FIGS. 7 and 8, it is assumed that application of the DC voltage from the DC voltage source V1 to the control unit 101 is started at time T1.

  When starting the process, the control unit 101 first acquires the divided voltage received at the temperature information port P4 as temperature information, and acquires the voltage received at the illuminance information port P3 as illuminance information (step S1). The control unit 101 converts the voltage received at the temperature information port P4 into the ambient temperature, and converts the voltage received at the illuminance information port P3 into the ambient illuminance (step S1).

  Next, the control unit 101 refers to the first pulse signal information stored in the first storage unit 106a, obtains a first duty ratio according to the ambient temperature, and stores it in the second storage unit 106b. With reference to the second pulse signal information, a second duty ratio corresponding to the ambient illuminance is obtained (step S2). Note that, as described above, the first duty ratio obtained in step S2 is a duty ratio in which the value obtained by dividing the ON period according to the ambient temperature by 2 is the ON period.

  Next, the control unit 101 compares the first duty ratio with the second duty ratio (step S3).

  If it is determined that the second duty ratio is not greater than the first duty ratio (step S3; NO), the process proceeds to step S4. This means that in order to cause the LED 103 to emit light quickly, two pulses of the first pulse signal having a larger duty ratio than the second duty ratio corresponding to the ambient illuminance are output, and the voltage applied to the LED 103 is increased. ing.

  As shown at the timing T2 in FIG. 7B, the control unit 101 continuously outputs two pulses of the first pulse signal having the first duty ratio from the dimming signal port P2 (step S4).

  When the control unit 101 outputs two pulses of the first pulse signal, the control unit 101 stops outputting the first pulse signal (step S5), and thereafter, the determination is made in step S2 as in the timing T3 in FIG. 7B. A second pulse signal having the second duty ratio and having the same cycle as that of the first pulse signal is output from the dimming signal port P2 (step S6).

  Thereafter, the control unit 101 continues to output the second pulse signal as a dimming signal until the power is turned off.

  On the other hand, when the control unit 101 determines in step S3 that the second duty ratio is larger than the first duty ratio (step S3; YES), it is better to output the second pulse without outputting the first pulse signal. The LED 103 can be quickly switched to a lighting state.

  Therefore, the control unit 101 skips steps S4 and S5 and outputs the second pulse signal having the second duty ratio determined in step S2 from the dimming signal port P2 (step S6).

  Thereafter, the control unit 101 continues to output the second pulse signal as a dimming signal until the power is turned off.

  In parallel with the dimming signal generation / output process described above (or prior to the above process), the control unit 101 outputs a reference voltage indicating a reference value of a current flowing from the reference voltage port P1 to the LED 103 from the differential amplifier 102c. Output to the non-inverting input terminal (+).

  The differential amplifier 102b measures a potential difference between both ends of the resistor 102a and outputs a voltage signal indicating a current flowing through the LED 103. The differential amplifier 102c is the difference between the reference voltage output from the control unit 101 and the voltage output from the differential amplifier 102b, that is, the current actually flowing through the LED 103 detected by the resistor 102a and the LED current indicated by the reference voltage. And outputs this to the PWM signal generation unit 102f.

  After the power is turned on, the PWM signal generation unit 102f converts a PWM signal whose frequency is sufficiently higher than the frequency of the dimming signal, as shown in FIG. 7C and FIG. Is output while adjusting the duty ratio so as to approach 0.

  In this state, when a high-level dimming signal is output from the control unit 101 in the above-described step S4 or S6, the AND circuit 102e calculates the logical product of the PWM signal and the dimming signal, and FIG. d) As shown in FIG. 8D, a PWM signal synchronized with the dimming signal is output. Thereby, the second switching circuit SW2 is switched at high speed.

  When the first switching circuit SW1 is turned on by the high level dimming signal and the second switch circuit SW2 is turned on by the high level PWM signal from the AND circuit 102e, the DC voltage source V1 → the capacitor 102i → the inductor 102g → second switching. A first electric circuit of circuit SW2 → resistor 102m → ground is conducted. At this time, the cathode voltage of the LED 103 becomes one terminal voltage of the capacitor 102i, and the anode voltage of the LED 103 becomes the DC voltage of the DC voltage source V1, so that a DC voltage is applied to the LED 103.

  However, since the amount of charge of the junction capacitance existing on the PN junction surface of the LED 103 is initially zero, the voltage applied to the PN junction surface of the LED 103 does not reach the light emission start voltage Vf. For this reason, LED103 does not conduct | electrically_connect, only a junction capacity | capacitance is charged, but an electric current does not flow.

  On the other hand, when the PWM signal input to the AND circuit 102e becomes low level, the output of the AND circuit 102e becomes low level, and the second switching circuit SW2 is turned off. As a result, the first electric circuit is interrupted, and the application of voltage to the LED 103 is also interrupted. While the dimming signal is at the high level, the same operation is repeated thereafter.

  When the dimming signal shown in FIG. 7B and FIG. 8B becomes low level, the first switching circuit SW1 is turned off and the output of the AND circuit 102e becomes low level. Turn off. As a result, the first electric circuit is interrupted, and the application of voltage to the LED 103 is also interrupted.

  Thereafter, the same operation is repeated according to the signal levels of the dimming signal and the PWM signal, and the PN junction capacitance of the LED 103 is gradually charged.

  Thereafter, when the charging voltage of the PN junction capacitance of the LED 103 reaches the light emission start voltage Vf, the LED 103 becomes conductive, and the DC voltage source V1 → resistance 102a → first switching circuit SW1 → LED103 → inductor 102g → second switching circuit SW2 → resistance. The LED current flows through the second electric circuit 102m → ground, and the LED 103 emits light. FIG. 7 shows an example in which charging starts at timing T2 and the charging voltage reaches the light emission start voltage Vf at timing T4. FIG. 8 shows charging started at timing T2 and the charging voltage becomes the light emission start voltage Vf at timing T5. Indicates that this has been reached. When the LED current flows, magnetic energy is accumulated in the inductor 102g.

  Subsequently, when the PWM signal becomes low level, the AND circuit 102e outputs a low level signal, the switching circuit SW2 is turned off, and the second electric circuit is cut off. Then, due to the magnetic energy accumulated in the inductor 102g, a current flows through the third electric path of the inductor 102g → the Schottky barrier diode 102h → the resistor 102a → the first switching circuit SW1 → the LED 103 → the inductor 102g, and the LED 103 is continuously energized. The

  Thereafter, while the dimming signal is at a high level, the same operation is repeated, and a constant current continues to flow through the LED 103. The duty of the PWM signal is adjusted so that the amount of current matches the amount of current indicated by the reference voltage.

  Thereafter, when the dimming signal becomes low level, the switch circuits SW1 and SW2 are turned off, and the power supply to the LED 103 is stopped. When the switch circuit SW1 is turned off, the magnetic energy remaining in the inductor 102g moves to the capacitor 102i via the Schottky barrier diode 102h, and is stored in the form of electrostatic energy. Next time, the switching circuit SW1 and the switching circuit SW2 Released when and are turned on.

  Thereafter, the same operation is repeated according to the voltage levels of the dimming signal and the PWM signal. As a result, a current flows through the LED 103 at a duty (= duty of the dimming signal = second duty ratio) corresponding to the ambient illuminance. Further, the amount of current flowing through the LED 103 is controlled by the PWM signal generation unit 102f so as to coincide with the current indicated by the reference voltage.

As described above, in the LED driving circuit 102 according to the present embodiment, as shown in FIG. 7, immediately after the driving of the LED 103 is started, the first pulse signal having the first duty ratio is 2 pulses as the dimming signal. In the meantime, when the PWM signal is at a high level, a voltage is applied to the LED 103 to charge the PN junction capacitance of the LED 103. Thereafter, a second pulse signal having a second duty ratio defined by the dimming signal is output as the dimming signal.

  Therefore, as shown in FIG. 8, the period for charging the PN junction capacitance of the LED 103 per certain period is longer than when only the second pulse having the second duty ratio is output as the dimming signal. For this reason, since the voltage applied to the PN junction of the LED 103 reaches the light emission start voltage Vf earlier than the case shown in FIG. 8, light emission starts earlier than the case shown in FIG. On the other hand, when the second duty ratio is longer than the first duty ratio, a second pulse signal having a second duty ratio corresponding to the ambient illuminance is output as the dimming signal from the beginning as the dimming signal. . This is to avoid the demerit that when the first pulse is applied even when the second duty ratio is larger, the start of light emission is delayed.

  Therefore, even when the operating environment temperature range of the HUD device 1 is wide, appropriate lighting control can be performed.

  In addition, since the cycle of the first pulse signal and the second pulse signal constituting the dimming signal is the same, the control of the control unit 101 is more effective than the case where the first pulse signal and the second pulse signal having different cycles are output. The burden is small.

(Modification)
In the above-described embodiment, when the LED 103 is activated, two pulses of the first pulse signal are output as the dimming signal, but only one pulse or three or more pulses are very good. In the case of one pulse, for example, control is performed such that one pulse of the first pulse signal in the ON period corresponding to the ambient temperature shown in FIG.

  At this time, the duty ratio may exceed 100%. In that case, a pulse having a corresponding length may be applied over two or more cycles. For example, when applying a pulse with a duty ratio of 120%, applying a pulse of 100% in the first period and a pulse of 20% in the second period is the same as applying a pulse of 120%. At this time, 20% in the second cycle is compared with the second duty ratio, and if the second duty ratio is larger, the second pulse signal having the second duty ratio may be applied.

  When N pulses of 3 pulses or more are used, for example, when the ON period corresponding to the ambient temperature shown in FIG. 5 is divided by N and the division value is larger than the duty ratio of the second pulse signal, the temperature The first pulse signal having a duty ratio corresponding to the duty ratio / N corresponding to is output as N pulses, and then the second pulse signal is output.

  Alternatively, the first pulse signal may be continuously output until the voltage applied to the LED 103 reaches a certain value (threshold).

  Hereinafter, an embodiment for controlling the dimming signal in this way will be described with reference to FIG. 9 and FIG.

  The basic configuration of the illumination control device 100A shown in FIG. 9 is the same as that of the illumination control device 100 shown in FIG. 3 except that a configuration for measuring the applied voltage of the LED 103 is added. Further, the first storage unit 106a is different in that the first duty ratio is stored with a constant value according to the ambient temperature, that is, with a fixed value regardless of the ambient temperature. In this case, the first duty ratio may be stored as a fixed value that does not depend on the ambient temperature, instead of the shape of the regression line LI described above.

  The illumination control device 100A includes an applied voltage detection circuit 107 and a power supply voltage detection circuit 108, and the control unit 101 includes an applied voltage information port P5 and a power supply voltage information port P6.

  The applied voltage detection circuit 107 includes a resistor 107a having one end connected to the cathode of the LED 103, a resistor 107b connected between the other end of the resistor 107a and the ground, and a voltage at a connection point between the resistors 107a and 107b. The voltage is applied to the applied voltage information port P5 of the control unit 101.

  The power supply voltage detection circuit 108 includes a resistor 108a having one end connected to the DC voltage source V1, a resistor 108b connected between the other end of the resistor 108a and the ground, and a connection point between the resistors 108a and 108b. The voltage is applied to the power supply voltage information port P6 of the control unit 101.

  In addition, in the illumination control device 100A, a third storage unit 106c that stores a threshold value is further provided so that the control unit 101 can determine the threshold value.

  The third storage unit 106 c stores information representing a relationship with a threshold value that is in accordance with the ambient temperature and is greater than 0 and smaller than the light emission start voltage Vf of the LED 103. As this information, for example, information on a regression line representing the relationship between the ambient temperature and the threshold value can be cited. Based on this information, a threshold value corresponding to the ambient temperature is set in advance.

  A voltage divided by the resistors 107a and 107b of the applied voltage detection circuit 107 is output to the applied voltage information port P5. For example, assuming that the cathode voltage of the LED 103 is Va, the resistance value of the resistor 107a is R3, and the resistance value of the resistor 107b is R4, the divided voltage [{R4 / (R3 + R4)} × Va] is applied to the applied voltage information port P5. To be applied.

  On the other hand, a voltage divided by the resistors 108a and 108b is output to the power supply voltage information port P6. For example, if the DC voltage of the DC voltage source V1 is V1, the resistance value of the resistor 108a is R5, and the resistance value of the resistor 108b is R6, the divided voltage of [{R6 / (R5 + R6)} × V1] is the power supply voltage information. Applied to port P6.

  When the LED 103 is initially driven, no current flows through the LED 103. For this reason, the voltage drop in the resistors 109 and 102a and the P-channel MOSFET 102j is almost zero. For this reason, the difference between the DC power supply voltage V 1 and the cathode voltage of the LED 103 can be regarded as the voltage applied to the LED 103. The control unit 101 obtains the DC power supply voltage V1 from the divided voltage applied to the power supply voltage information port P6, obtains the cathode voltage of the LED 103 from the divided voltage applied to the applied voltage information port P5, and calculates the difference between them. It is regarded as an applied voltage of the LED 103.

  For example, when the ignition is turned on, the illumination control device 100A starts the dimming signal generation / output process shown in the flowchart of FIG.

  The control unit 101 acquires the voltage received at the temperature information port P4 as temperature information, and acquires the voltage received at the illuminance information port P3 as illuminance information (step S100). In addition, the control unit 101 converts the voltage received at the temperature information port P4 into ambient temperature, and converts the voltage received at the illuminance information port P3 into ambient illuminance (step S100).

  Next, the control unit 101 refers to the third storage unit 106c to determine a threshold value according to the ambient temperature (step S101). And the control part 101 judges the 1st duty ratio and the 2nd duty ratio according to ambient illuminance with reference to the 1st memory | storage part 106a and the 2nd memory | storage part 106b (step S102). The first duty ratio is not a fixed value as described here, but as described above, a value that changes according to the ambient temperature (for example, ON obtained by applying the ambient temperature to the regression line LI). (The first duty ratio obtained by dividing the period by 2).

  Next, the control unit 101 compares the magnitude of the first duty ratio with the magnitude of the second duty ratio (step S103). If it is determined that the second duty ratio is not greater than the first duty ratio (step S103; NO), the control unit 101 drives the first pulse signal having the first duty ratio from the dimming signal port P2 to the LED. It outputs to the circuit 102 (step S104).

  Next, the control unit 101 obtains the cathode voltage and the DC power supply voltage V1 of the LED 103 from the voltage applied to the applied voltage information port P5 and the voltage applied to the power supply voltage information port P6, and calculates the difference between the LED 103 and the LED 103. The applied voltage is obtained. Next, it is determined whether or not the obtained difference has reached a threshold value (step S105). When it is determined that the difference has not reached the threshold (step S105; NO), the process returns to step S104 and continues to output the first pulse signal.

  On the other hand, when the control unit 101 determines that the difference has reached the threshold (step S105; YES), the control unit 101 stops outputting the first pulse signal (step S106), and proceeds to step S107.

  On the other hand, when the control unit 101 determines in step S103 that the second duty ratio is larger than the first duty ratio (step S103; YES), the control unit 101 does not output the first pulse signal and proceeds to step S107. Transition.

  In step S107, the control unit 101 sequentially outputs the second pulse signal having the second duty ratio determined in step S102 and having the same cycle as that of the first pulse signal from the dimming signal port P2.

  For example, the control unit 101 continues step S107 until the ignition is turned off.

  As described above, according to the lighting control apparatus 100A according to the present embodiment, after the output of the first pulse signal is started, the voltage applied to the LED 103 reaches a threshold value determined according to the ambient temperature of the LED 103. The first pulse signal is output, and then the output of the second pulse signal is started.

  Thereby, lighting control of LED103 can be performed more efficiently according to the ambient temperature of LED103.

  In the above description, the LED drive circuit 102 constitutes a step-down converter that steps down the DC voltage from the DC voltage source V1, but the present invention is not limited to this example, and is not limited to this example. A converter may be configured.

  In the above description, only one LED 103 is provided. However, the present invention is not limited to this example, and a configuration in which two or more LEDs are provided in series or in parallel may be used. When N LEDs are arranged in series, light emission starts when the applied voltage of all LEDs exceeds the emission start voltage Vf, and when N LEDs are arranged in parallel, Light emission is started sequentially from the LED whose voltage exceeds the light emission start voltage Vf.

  Furthermore, in the above description, the DC voltage source V1 that supplies a DC voltage to the control unit 101 and the LED drive circuit 102 and the DC voltage source V2 that applies a DC voltage to the temperature detection circuit 104 are provided separately. However, the present invention is not limited to this example, and a DC voltage may be applied to the control unit 101, the LED drive circuit 102, and the temperature detection circuit 104 from the same DC voltage source V1.

  Furthermore, in the present embodiment, the temperature detection circuit 104 uses the thermistor 104b, but the present invention is not limited to this example, and other elements capable of measuring temperature, such as a thermocouple, may be used. Further, the ambient temperature information may be obtained from the vehicle 2 side by communication. However, in this case, since the ambient temperature is not the LED 103, the control becomes more complicated.

  Further, in the present embodiment, the first pulse signal information is information representing the regression line LI. However, the present invention is not limited to this example, and is information representing another shape, for example, information representing a curve shape. May be. Further, it may be in the form of table data or a function related to temperature.

  Further, in the present embodiment, the second duty ratio is set to a value according to the ambient illuminance of the HUD device 1, but the present invention is not limited to this example, and the second duty ratio is dimming in an operation unit (not shown) by the user. The duty ratio may be ambient illuminance determined by the operation. The ambient illuminance may be obtained by communication from the vehicle 2 side.

  In the above embodiment, by adjusting the duty ratio of the dimming signal when the LED 103 is started, the increase in the applied voltage is accelerated and the light emission of the LED 103 is accelerated, but the PWM signal output from the PWM signal generation unit 102f By adjusting the duty ratio, it is possible to accelerate the increase of the applied voltage and accelerate the light emission of the LED 103.

  Hereinafter, an illumination control device 100B capable of speeding up the light emission of the LED by adjusting the duty ratio of the PWM signal output from the PWM signal generation unit 102f will be described with reference to FIGS.

  In this case, for example, as shown in FIG. 11, the control unit 101 outputs a duty control signal from the duty information port P7 to the PWM signal generation unit 102f.

  In this case, the first storage unit 106a stores the duty ratio of the duty control signal in association with the ambient temperature.

  When the LED 103 is activated, the control unit 101 continues to output a dimming signal having a duty ratio corresponding to the illuminance measured by the illuminance sensor 105, as shown in FIG. In addition, when the LED 103 is activated, the control unit 101 controls the PWM signal generation unit 102f with a duty control signal from the duty information port P7, and the control information is shown in FIG. 12C according to the storage information of the first storage unit 106a. As described above, a PWM signal having a larger duty ratio than that in the case where the LED 103 that is turned on is dimmed is set in a predetermined period, for example, i) a period until the dimming signal is output in N pulses, and ii) the PWM signal During the period of M pulses, output is performed until the applied voltage of the LED 103 exceeds the threshold value, and then a PWM signal having a duty ratio corresponding to the deviation ε is output. Even with this method, the same effects as those of the above embodiment can be obtained.

  Furthermore, in the above-described embodiment, the method of controlling the applied voltage on the PN junction surface of the LED 103 by performing PWM control on the effective voltage applied to the LED 103 from the outside has been described, but the present invention is not limited to this example. The configuration may be such that the effective voltage applied from the outside is controlled by PAM (Pulse Amplitude Modulation) control instead of PWM control.

  Furthermore, in this embodiment, the difference between the DC power supply voltage V1 and the cathode voltage of the LED 103 is regarded as the voltage applied to the LED, but the present invention is not limited to this example. For example, a divided voltage by the resistors 107 a and 107 b in the voltage detection circuit 107 may be regarded as an applied voltage to the LED 103. In this way, the voltage detection unit can be configured by the voltage detection circuit 107 and the control unit 101, and therefore the number of parts can be reduced as compared with the configuration of the voltage detection unit described above.

  It should be noted that the present invention can be variously modified and modified without departing from the broad spirit and scope of the present invention. Further, the above-described embodiment is for explaining the present invention, and does not limit the scope of the present invention.

  The present invention is suitable for switching the LED from the unlit state to the lit state.

DESCRIPTION OF SYMBOLS 1 HUD apparatus 2 Vehicle 3 Windshield 4 User 10 Liquid crystal display device 20 Optical system 21 Plane mirror 22 Concave mirror 40 Circuit board 50 Housing 100, 100A, 100B Illumination control apparatus 101 Control part 102 LED drive circuit 102a, 102m Resistance 102b-102d Differential Amplifier 102e AND circuit 102f PWM signal generator 102g Inductor 102h Schottky barrier diode 102i Capacitor 102j P-channel MOSFET
102k Parasitic diode 102l Varistor 102n Knot circuit 102o Amplifier 103 LED
104 Temperature detection circuit 104a Resistance 104b Thermistor 105 Illuminance sensor 106a First storage unit 106b Second storage unit 106c Third storage unit 107 Applied voltage detection circuit L Display light LI Regression line P1 Reference voltage port P2 Dimming signal port P3 Illuminance information port P4 Temperature information port P5 Applied voltage information port P6 Power supply voltage information port V Virtual image

Claims (5)

A light emitting element;
A switching power supply unit that applies a DC voltage to the light emitting element by receiving a pulse signal and performing a switching operation;
A temperature measuring unit for measuring the ambient temperature of the light emitting element;
A first storage unit storing ambient temperature information that is information related to the ambient temperature of the light emitting element, and first duty ratio information that is information related to the first duty ratio according to the ambient temperature;
A parameter other than the ambient temperature, a second storage unit which stores information of the second pulse signal which represents the relationship between the second duty ratio corresponding to this parameter,
When the light emitting element is switched from the off state to the on state, the first duty ratio according to the ambient temperature measured by the temperature measuring unit is determined with reference to the first storage unit, and the determination is made. as a pulse signal of a first duty ratio first pulse signal, the output to the switching power supply unit, and a control unit for the switching power supply unit controls the DC voltage applied to the light emitting element,
With
The control unit discriminates the first duty ratio and the second duty ratio with reference to the first storage unit and the second storage unit, respectively, and the first duty ratio and the second duty ratio, respectively. An illumination control device that outputs the pulse signal having a duty ratio that is larger than the ratio to the switching power supply unit. A light emitting element;
A switching power supply unit that applies a DC voltage to the light emitting element by receiving a pulse signal and performing a switching operation;
A temperature measuring unit for measuring the ambient temperature of the light emitting element;
A first storage unit storing ambient temperature information that is information related to the ambient temperature of the light emitting element, and first duty ratio information that is information related to the first duty ratio according to the ambient temperature;
When the light emitting element is switched from the off state to the on state, the first duty ratio according to the ambient temperature measured by the temperature measuring unit is determined with reference to the first storage unit, and the determination is made. After outputting the pulse signal of the first duty ratio as the first pulse signal to the switching power supply unit,
A second pulse signal having a duty ratio corresponding to parameters other than the ambient temperature, by outputting to the switching power supply unit, and a control section for controlling the DC voltage the switching power supply unit is applied to the light emitting element,
With
The first duty ratio information is information representing an ON period of the pulse signal according to the ambient temperature,
The first pulse signal and the second pulse signal have the same period,
The control unit supplies, to the switching power supply unit, the pulse signal having the divided ON period obtained by dividing the ON period as a plurality of the first duty ratio as the first pulse signal by the divided number. An illumination control device characterized by outputting. The first storage unit stores information of a regression line representing a relationship between the ambient temperature information and the first duty ratio information.
The illumination control device according to claim 1 or 2. An illuminance measurement unit that measures the illuminance around the device on which the light emitting element is mounted;
The parameter is the ambient illuminance,
The lighting control device according to claim 1. A voltage detection unit for detecting a value of a DC voltage applied to the light emitting element;
A third storage unit that stores information representing a relationship between the ambient temperature and a threshold value that is in accordance with the ambient temperature and is greater than 0 and smaller than the light emission start voltage of the light emitting element; In addition,
The control unit determines the threshold according to the ambient temperature measured by the temperature measurement unit with reference to the third storage unit, starts output of the first pulse signal, and then outputs the voltage. When the value of the DC voltage detected by the detection unit reaches the threshold value , the output of the first pulse signal is stopped and the output of the second pulse signal is started.
The illumination control device according to any one of claims 1 to 4.

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