JP5874049B2 - Discharge lamp lighting device, headlamp using the same, and vehicle - Google Patents

Description

  The present invention relates to a discharge lamp lighting device, a headlamp using the same, and a vehicle.

  High-intensity discharge lamps such as metal halide lamps are also used for in-vehicle applications because of their high luminance. In in-vehicle applications, it is necessary to quickly start up the luminous flux at the start, especially in order to ensure early visibility, and the rising of the luminous flux can be achieved by supplying more power than the rated power to the discharge lamp immediately after the discharge lamp is lit. There is a discharge lamp lighting device that accelerates (see, for example, Patent Documents 1 and 2).

  In FIG. 11, the circuit block diagram of the discharge lamp lighting device 1 is shown. The discharge lamp lighting device 1 has a DC / DC converter unit 2, an inverter unit 3, an igniter unit 4 and a control unit 5 as main components, and is discharged by supplying power to the discharge lamp La using a DC power source E1 as an input power source. The light La is turned on. The DC / DC converter unit 2 raises or lowers the power supply voltage Vin applied from the DC power supply E1 to generate a DC voltage V1 necessary for lighting the discharge lamp La. The inverter unit 3 converts the DC voltage V1 into an AC voltage V2 composed of a low-frequency rectangular wave. The igniter unit 4 generates a high voltage of several tens of kV that starts the discharge lamp La. The control unit 5 detects the output voltage (DC voltage V1) and output current (current I1) of the DC / DC converter unit 2, and the DC / DC converter so that the output power calculated from the detection result becomes a target value. Control part 2.

  Below, the specific structure of the discharge lamp lighting device 1 is demonstrated.

  In the DC / DC converter unit 2, the capacitors C1 and C2, the switching element Q1, the transformer Tr1, the diode D1, and the switching element Q1 constitute a flyback type DC / DC converter circuit.

  A capacitor C1 is connected between the output terminals of the DC power supply E1 via a switch S1. When the switch S1 is turned on, a DC power supply voltage Vin output from the DC power supply E1 is applied between both ends of the capacitor C1. Between both ends of the capacitor C1, a primary winding n11 of the transformer Tr1 and a switching element Q1 formed of an n-channel MOSFET are connected in series. A diode D1 and a capacitor C2 are connected in series between both ends of the secondary winding n12 of the transformer Tr1. When the switching control unit 21 turns on the switching element Q1, a current flows through the primary winding n11 of the transformer Tr1, and energy is accumulated in the transformer Tr1. When the switching element Q1 is turned off, current flows through the path of the secondary winding n12 → the capacitor C2 → the diode D1 by the energy accumulated in the transformer Tr1, and the capacitor C2 is charged. Then, the switching element Q1 is repeatedly turned on and off, so that a DC voltage V1 is generated between both ends of the capacitor C2.

  The inverter unit 3 constitutes a full-bridge inverter circuit with switching elements Q2 to Q5 composed of four n-channel MOSFETs. A series circuit composed of switching elements Q2 and Q4 and a series circuit composed of switching elements Q3 and Q5 are connected in parallel between the output terminals of the DC / DC converter unit 2, and the switching elements Q4 and Q5 are connected to the high voltage side. Switching elements Q2, Q3 are connected to the low voltage side. In the inverter unit 3, a connection point between the switching elements Q2 and Q4 and a connection point between the switching elements Q3 and Q5 constitute an output end.

  The igniter unit 4 includes a capacitor Cs, a transformer Tr2, and a spark gap SG1. The capacitor Cs is connected between the output terminals of the inverter unit 3. In parallel with the capacitor Cs, a series circuit composed of the primary winding n21 of the transformer Tr2 and the spark gap SG1, and a series circuit composed of the secondary winding n22 of the transformer Tr2 and the discharge lamp La are connected.

  The control unit 5 includes a power target storage unit 51, a stable power limiting unit 52, a current target calculation unit 53, and an error amplifier 54. The power target storage unit 51 stores an output power target value to be supplied to the discharge lamp La, and the stable power limiting unit 52 acquires the output power target value. The stable power limiting unit 52 corrects the acquired output power target value and outputs the corrected output power target value to the current target calculation unit 53. The current target calculation unit 53 detects the DC voltage V1 output from the DC / DC converter unit 2, calculates a target current from the corrected output power target value and the DC voltage V1, and outputs the target current to the error amplifier 54. . The error amplifier 54 receives the detection result of the current I1 output from the DC / DC converter unit 2, and outputs the output control signal to the DC / DC converter unit so that the difference between the target current and the current I1 does not occur. Output to 2. The resistor R1 is configured as a current detection unit, and the detection result of the current I1 is output to the error amplifier 54.

  Next, the operation of the discharge lamp lighting device 1 will be described.

  When the switch S1 is turned on, the power supply voltage Vin is applied from the DC power supply E1 to the DC / DC converter unit 2. And the DC / DC converter part 2 produces | generates DC voltage V1 by turning ON / OFF the switching element Q1. The DC / DC converter unit 2 varies the DC voltage V1 by varying the on-time and the driving frequency of the switching element Q1 based on the output control signal output from the control unit 5.

  The inverter unit 3 maintains the switching elements Q2 and Q5 in the on state and maintains the switching elements Q3 and Q4 in the off state before starting the discharge lamp La. Before the discharge lamp La is started, since the discharge lamp La is in an open state, when the DC voltage V1 generated across the capacitor C2 increases, the voltage across the capacitor Cs also increases. When the DC voltage V1 rises and exceeds a predetermined voltage, the spark gap SG1 breaks down and a voltage is instantaneously applied to the primary winding n21 of the transformer Tr2. As a result, a high voltage (about several tens of kV) that is twice the turn ratio of the voltage applied to the primary winding n21 is applied to the secondary winding n22 of the transformer Tr2. This high voltage breaks down the discharge lamp La. At that moment, current flows from the DC / DC converter section 2 through the switching elements Q2 and Q5, the discharge lamp La shifts to arc discharge, and the discharge lamp La is started.

  After starting the discharge lamp La, the switching elements Q2 to Q5 are alternated at predetermined time intervals to generate an alternating voltage V2 and supply it to the discharge lamp La. In addition, the control unit 5 performs feedback control of the DC / DC converter unit 2 so that the output power of the DC / DC converter unit 2 matches the output power target value. Thereby, stable lighting of the discharge lamp La is realized.

  Further, the discharge lamp lighting device 1 varies the output power target value according to the temperature rise of the discharge lamp La in order to prevent overshoot and undershoot of the light flux while ensuring the rising performance of the light flux of the discharge lamp La. Yes. The power target storage unit 51 stores a target power curve K1 shown in FIG. This target power curve K1 shows the output power target value with respect to the time after the start of the discharge lamp La. In the target power curve K1, when the time when the discharge lamp La is started is t0, the power (maximum power) is more than twice the rated power Ws0 (35W) of the discharge lamp La during the period TA from the time t0 to the time t1. ) Is the output power target value. Hereinafter, the output power target value in the period TA is referred to as the maximum power target value, and here, the maximum allowable power value Wp0 (about 70 to 90 W) of the discharge lamp La is set as the maximum power target value. Immediately after the start of the discharge lamp La, a large amount of electric power is supplied to the discharge lamp La, whereby the luminous flux of the discharge lamp La is rapidly raised. The period TA is preferably about 4 seconds.

  During the period TB from time t1 to time t2, the output power target value is smoothly reduced from the maximum power target value Wp0 to be stable so that the luminous flux of the discharge lamp La does not cause overshoot or undershoot. Asymptotically approach the power target value. Here, the rated power Ws0 of the discharge lamp La is set as the stable power target value. The period TB is preferably about 40 to 50 seconds. In the period TC after time t2, the discharge lamp La is stably lit by maintaining the output power target value at the stable power target value Ws0. Hereinafter, the power supplied to the discharge lamp La in the period TC is referred to as stable power.

  The above-described control is performed only when the discharge lamp La is started from a cold state (hereinafter referred to as initial start). If control at the initial start (cold start) is performed in a state where the temperature of the discharge lamp La is high immediately after the discharge lamp La is turned off for a short period of time, the discharge lamp La emits excessive light during the periods TA and TB. Therefore, when starting the discharge lamp La that has been turned on for a short period of time (hereinafter referred to as restart), the following control is performed.

  As shown in FIG. 13, in accordance with the turn-off time of the discharge lamp La, the fluctuation of the output power target value is started from times ta and tb during the periods TA and TB in the target power curve K1. Thereby, the electric power supplied to the discharge lamp La after restart is suppressed, and excessive light emission at the time of restart is suppressed.

  That is, as shown in FIG. 13, when the turn-off period before relighting is relatively long, starting from the output power target value Wa at the time ta of the target power curve K1, and when the turn-off period before relighting is relatively short, It starts from the output power target value Wb (<Wa) at the time tb (> ta) of the target power curve K1. Thereby, the shorter the extinction period before relighting, that is, the higher the temperature of the discharge lamp La, the more the power (maximum power) supplied to the discharge lamp La immediately after the discharge lamp La is started.

  At the time of restarting, for example, a timer circuit configured by a capacitor charging / discharging circuit is used to determine the power to be supplied to the discharge lamp La according to the voltage across the capacitor (charge charge amount) at the time of restarting.

  In addition, when the discharge lamp lighting device 1 is used in a high temperature environment such as an in-vehicle application and the ambient temperature of the discharge lamp lighting device 1 is high or the power supply voltage Vin is lowered, the circuit loss and the thermal stress of the components increase. There is a risk of circuit destruction. In order to prevent this, the power supply voltage Vin and the ambient temperature Ta are detected, and control is performed to reduce the maximum power target value based on the detection result (see, for example, Patent Documents 3 and 4).

  A discharge lamp lighting device 1 shown in FIG. 11 includes a power supply voltage detection unit 6 and a temperature detection unit 7. The power supply voltage detection unit 6 detects the power supply voltage Vin applied from the direct current power supply E <b> 1 to the DC / DC converter unit 2 and outputs it to the stable power limiting unit 52. Further, the temperature detection unit 7 detects the ambient temperature Ta of the discharge lamp lighting device 1 and outputs it to the stable power limiting unit 52. The temperature detector 7 may be configured to detect the temperature of the discharge lamp lighting device 1.

  Then, stable power limiting unit 52 reduces the maximum power target value from allowable maximum power value Wp0 based on the detection results of power supply voltage detection unit 6 and temperature detection unit 7.

  For example, as shown in FIG. 14, the target power curve when the ambient temperature Ta is Ta0 (normal temperature) is K1, and the target power curve when the ambient temperature Ta is increased from Ta0 to Ta1 is K1a. When the ambient temperature Ta rises from Ta0 to Ta1, the stable power limiting unit 52 corrects the maximum power target value to Wpc lower than Wp0 and maintains Wpc until time tc. After time tc, the output power target value is changed along the target power curve K1. Further, the target power curve when the ambient temperature Ta rises to Ta2 (> Ta1) is defined as K1b. In this case, the stable power limiting unit 52 corrects the maximum power target value to Wpd (<Wpc) lower than Wp0 and maintains Wpd until time td. After time td, the output power target value is changed along the target power curve K1.

  Further, in the above, control is performed so as to reduce only the maximum power target value, but based on the detection results of the power supply voltage detection unit 6 and the temperature detection unit 7, the output power target value over the entire period (TA to TC). You may comprise so that may be reduced. Thereby, the thermal stress of the components of the discharge lamp lighting device 1 can be reduced.

Patent No. 2946384 JP 2000-235899 A Japanese Patent Laid-Open No. 2002-216989 JP 2001-43991 A

  One important function required of the discharge lamp lighting device 1 is the lighting maintenance performance of the discharge lamp La. However, as described above, when the output power target value is reduced according to the increase degree of the ambient temperature Ta and the reduction degree of the power supply voltage Vin, the power supplied to the discharge lamp La is used to maintain the lighting of the discharge lamp La. There is a risk of lower than the required power. As a result, the discharge lamp La disappears or flickers.

  The present invention has been made in view of the above-described reasons, and its object is to reduce a thermal stress at a high temperature and a low power supply voltage, and to ensure a discharge lamp lighting maintenance performance. And it is providing the headlamp and vehicle using this.

The discharge lamp lighting device of the present invention, in the discharge lamp lighting device for supplying electric power to the discharge lamp as the input DC power, a drive circuit for supplying electric power to the discharge lamp, and a control circuit for controlling the drive circuit, ambient A temperature detection unit that detects the temperature or the temperature of the device itself, and a power supply voltage detection unit that detects the voltage of the DC power supply, the control circuit in the first period after the discharge lamp is started, The power supplied to the discharge lamp is reduced from the first power toward the second power lower than the first power in accordance with the rise in the temperature of the discharge lamp, and the second continuous in the first period. In this period, the second power is supplied to the discharge lamp, and the second power is reduced according to the degree of increase in the detection value of the temperature detection unit and the degree of decrease in the detection value of the power supply voltage detection unit. And let the second power have a lower limit value. Provided, wherein said second power by the reduction amount of the second power to the upper limit value becomes the lower limit value, the control circuit, the reduction amount of the second power, the detection value of the temperature detecting portion Is determined by the sum of a first reduction amount obtained by a function having a variable as a variable and a second reduction amount obtained by a function having a detection value of the power supply voltage detection unit as a variable, and the first reduction amount The sum of the maximum value of the amount and the maximum value of the second reduction amount is larger than the upper limit value of the reduction amount of the second power .

  In this discharge lamp lighting device, it is preferable that the control circuit reduces the lower limit value when the detection value of the temperature detection unit is equal to or higher than a first temperature.

  In the discharge lamp lighting device, it is preferable that the control circuit reduces the lower limit value when the time when the detected value of the temperature detection unit is equal to or higher than the first temperature is equal to or longer than the first time.

  In this discharge lamp lighting device, the control circuit preferably stops power supply from the drive circuit to the discharge lamp when the detected value of the temperature detection unit is equal to or higher than a second temperature.

  In this discharge lamp lighting device, the control circuit is configured to supply power from the drive circuit to the discharge lamp when the time when the detected value of the temperature detection unit is equal to or higher than the second temperature is equal to or longer than the second time. It is preferable to stop the supply.

  In this discharge lamp lighting device, the control circuit detects the temperature detection unit after the detection value of the temperature detection unit becomes equal to or higher than the second temperature and stops the power supply from the drive circuit to the discharge lamp. When the value reaches a third temperature lower than the second temperature or lower, it is preferable to restart the power supply from the drive circuit to the discharge lamp.

  In this discharge lamp lighting device, the control circuit is configured to switch from the drive circuit to the discharge lamp when the detection value of the temperature detection unit is equal to or less than the third time. It is preferable to restart the power supply.

In this discharge lamp lighting device, the control circuit reduces the lower limit value when the detection value of the temperature detection unit is equal to or higher than a first temperature,
The third temperature is preferably equal to or higher than the first temperature.

  In this discharge lamp lighting device, it is preferable that the lower limit value is not less than a power value at which the discharge lamp can be kept lit at least within a lifetime.

  The headlamp of the present invention is a discharge lamp lighting device for supplying power to a discharge lamp with a DC power supply as an input, a drive circuit for supplying power to the discharge lamp, a control circuit for controlling the drive circuit, an ambient temperature or A temperature detection unit that detects a temperature of the device itself; and a power supply voltage detection unit that detects a voltage of the DC power supply, wherein the control circuit includes the discharge lamp in a first period after the discharge lamp is started. The electric power supplied to the second electric power is reduced from the first electric power toward the second electric power lower than the first electric power in accordance with the rise in the temperature of the discharge lamp, and the second period continuous to the first period The second power is supplied to the discharge lamp, and the second power is reduced according to the degree of increase in the detection value of the temperature detection unit and the degree of reduction in the detection value of the power supply voltage detection unit, Discharging to provide a lower limit for the second power A lighting device, characterized in that it comprises a discharge lamp to be lighted by the discharge lamp lighting device.

  A vehicle according to the present invention is a discharge lamp lighting device that supplies power to a discharge lamp with a DC power supply as an input, a drive circuit that supplies power to the discharge lamp, a control circuit that controls the drive circuit, and an ambient temperature or its own device. And a power supply voltage detection unit for detecting the voltage of the DC power supply, and the control circuit supplies the discharge lamp to the discharge lamp in a first period after the discharge lamp is started. The power to be reduced from the first power toward the second power lower than the first power according to the rise in the temperature of the discharge lamp, and in a second period that is continuous with the first period, Supplying the second electric power to the discharge lamp, reducing the second electric power according to the degree of increase in the detection value of the temperature detection unit and the degree of reduction in the detection value of the power supply voltage detection unit; Discharging to set a lower limit for power of 2 A lighting device, a headlight and a discharge lamp to be lighted by the discharge lamp lighting apparatus, characterized by comprising a vehicle body in which the headlamp is attached.

  As described above, the present invention has the effects of reducing the thermal stress at high temperatures and low power supply voltages and ensuring the lighting maintenance performance of the discharge lamp.

It is a circuit block diagram of the discharge lamp lighting device of this invention. It is a graph which shows the 1st reduction amount. It is a graph which shows the 2nd reduction amount. It is a graph which shows the fluctuation | variation of the output electric power target value with respect to time. (A) It is a graph which shows the power supply voltage with respect to time. (B) It is a graph which shows the discharge lamp point pressure with respect to time. (C) It is a graph which shows the discharge lamp electric current with respect to time. It is a graph which shows the fluctuation | variation of a lower limit. It is a graph which shows the fluctuation | variation of a lower limit. It is a graph which shows the fluctuation | variation of a lower limit. It is a graph which shows the fluctuation | variation of a lower limit. It is a schematic block diagram of a headlamp and a vehicle. It is a circuit block diagram of the conventional discharge lamp lighting device. It is a graph which shows the fluctuation | variation of the output electric power target value with respect to time. It is a graph which shows the fluctuation | variation of the output electric power target value with respect to time. It is a graph which shows the fluctuation | variation of the output electric power target value with respect to time.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
The circuit block diagram of the discharge lamp lighting device 1 of this embodiment is shown in FIG. In addition, the same code | symbol is attached | subjected to the structure similar to the conventional discharge lamp lighting device 1 shown in FIG. 11, and description is abbreviate | omitted.

The control unit 5 of the discharge lamp lighting device 1 of the present embodiment includes a power target storage unit 51, a stable power limit unit 52, a current target calculation unit 53, an error amplifier 54, and a stable power lower limit limit unit 55. The stable power lower limit limiting unit 55 is interposed between the stable power limiting unit 52 and the current target calculation unit 53, and sets an upper limit for the amount of reduction in the output power target value (stable power target value) in the period TC. Thus, a lower limit is provided for the stable power target value. The DC / DC converter unit 2, the inverter unit 3, and the igniter unit 4 correspond to the drive circuit of the present invention, and the control unit 5 corresponds to the control circuit of the present invention. The period TA and the period TB correspond to the first period of the present invention, and the power (maximum power) immediately after the discharge lamp La is started and lit corresponds to the first power of the present invention. The period TC corresponds to the second period of the present invention, and the stable power corresponds to the second power of the present invention.

  This embodiment is characterized in that a lower limit value is set for stable power by setting a lower limit value for the stable power target value, which will be described below.

  As shown in FIG. 2, the stable power limiting unit 52 uses a function having the detection value (ambient temperature Ta) of the temperature detection unit 7 as a variable to reduce the stable power target value by the ambient temperature Ta (hereinafter, the first (Referred to as a reduction amount Wt). When the ambient temperature Ta is equal to or lower than the temperature Tth1, the first reduction amount Wt is zero. Further, the first reduction amount Wt increases as the ambient temperature Ta exceeds the temperature Tth1, and when the ambient temperature Ta reaches the temperature Tth2, the first reduction amount Wt becomes Wt1 (= 6 W). Further, when the ambient temperature Ta exceeds the temperature Tth2, the first reduction amount Wt becomes constant at Wt1.

Further, as shown in FIG. 3, the stable power limiting unit 52 uses a function having the detection value (power supply voltage Vin) of the power supply voltage detection unit 6 as a variable to reduce the stable power target value by the power supply voltage Vin (hereinafter referred to as “reduction power target value”) , Referred to as a second reduction amount Wv). When the power supply voltage Vin is equal to or higher than the voltage Vth1, the second reduction amount Wv is zero. Further, the second reduction amount Wv increases as the power supply voltage Vin falls below the voltage Vth1, and when it reaches the voltage Vth2, the second reduction amount Wv becomes Wv1 (= 6 W). When the power supply voltage Vin falls below the voltage Vth2, the second reduction amount Wv is constant at Wv1.

  Then, when the stable power target value acquired from the power target storage unit 51 is Ws0 that is the rated power of the discharge lamp La, the stable power limiting unit 52 starts from Ws0 to the first, as shown in the following formula (1). The stable power target value Wla1 corrected by subtracting the second reduction amount is generated.

Wla1 = Ws0−Wt−Wv (1)
Then, stable power limiting unit 52 outputs stable power target value Wla1 to stable power lower limit limiting unit 55.

The stable power lower limit limiting unit 55 compares the stable power target value Wla1 with the preset lower limit value Wla2 of the stable power target value. The lower limit value Wla2 is set to be equal to or higher than a power value that can maintain lighting even at the end of the life of the discharge lamp La. Then, when the stable power target value Wla1 is larger than the lower limit value Wla2, the stable power lower limit limiting unit 55 outputs the stable power target value Wla1 to the current target calculation unit 53. Thereafter, feedback control is performed so that the output power (stable power) of the DC / DC converter unit 2 matches the stable power target value Wla1 as in the conventional case.

However, for example, it is assumed that the stable power target value Ws0 is 35 W and the lower limit value Wla2 is 26 W. Then, and ambient temperature Ta is Tth2, if the power supply voltage V in is Vth2, stable power target value Wla1 is 23W (= Ws0-Wt1-Wv1 = 35-6-6) , and the stable power target value Wla1 lower limit It becomes smaller than Wla2.

In this case, the stable power lower limit limiting unit 55 outputs the lower limit value Wla2 to the current target calculation unit 53. Thereafter, feedback control is performed so that the output power (stable power) of the DC / DC converter unit 2 matches the lower limit value Wla2, as in the conventional case.

Thus, in the present embodiment, by providing the lower limit value to a stable power target value, upon reduction of the power supply voltage V in and, when the ambient temperature rises Ta, stable power restrain the greatly reduced. Since the lower limit value Wla2 is set to be equal to or higher than a power value that can maintain the lighting of the discharge lamp La, it is possible to ensure the lighting maintaining performance when the discharge lamp La is stable.

  It should be noted that the power value that can maintain the lighting of the discharge lamp La varies depending on variations in the sealing material, the electrode shape, or the degree of aging that constitutes the discharge lamp La. 20 to 26W. The above effect can be obtained even if the type of the discharge lamp La is a mercury-free high-intensity discharge lamp or a mercury-containing discharge lamp. Further, the discharge lamp La may contain less than 2 mg (more preferably less than 1 mg) of mercury per cc of the hermetic container.

  In the present embodiment, as shown in FIG. 4, the reduction value of the detection value (power supply voltage Vin) of the power supply voltage detection unit 6 and the detection value (ambient temperature Ta) of the temperature detection unit 7 in all periods TA to TC. ), The output power target value is reduced according to the increase degree. In FIG. 4, K1 is a target power curve stored in the power target storage unit 51, and K2 is a target power curve after correction by the stable power limiting unit 52. As the ambient temperature Ta increases and the power supply voltage Vin decreases, the stable power limiter 52 generates a target power curve K2 in which the output power target value is reduced from the target power curve K1. Then, feedback control is performed so that power along the target power curve K2 is supplied to the discharge lamp La. The maximum power target value in the target power curve K2 is set to Wp1 (<Wp0), and the stable power target value is set to Ws1 (<Ws0).

  With the above control, when the temperature of the discharge lamp lighting device 1 rises due to the installation environment of the discharge lamp lighting device 1 or the effect of self-heating of the device itself, the discharge lamp lighting device 1 reaches a thermal runaway state and the device itself is destroyed. Can be prevented. Further, the higher the temperature of the discharge lamp lighting device 1, the greater the heat loss of the device itself. Therefore, in addition to the increase in the ambient temperature Ta of the discharge lamp lighting device 1, the self-heating of the discharge lamp lighting device 1 due to power loss. Will also increase. However, since the electric power supplied to the discharge lamp La is reduced according to the increase degree of the ambient temperature Ta, the power loss that causes the self-heating can be reduced, and the increase in the apparatus temperature can be suppressed. As a result, even when the ambient temperature Ta is high or the power supply voltage Vin is low, the thermal stress is reduced and the device temperature is stabilized at a temperature at which the discharge lamp lighting device 1 does not run out of heat.

In addition, as an important function of the discharge lamp lighting device 1, there is a need to constantly supply a constant power with respect to fluctuations in the power supply voltage Vin. However, when the battery voltage (power supply voltage Vin) drops abnormally, if a constant power is supplied to the discharge lamp La, the power supply current Iin increases and power loss due to heat generation or the like increases. In particular, if the power supply voltage Vin continues to decrease in a high temperature environment, the circuit elements may generate heat and cause deterioration or destruction.

  However, in the present embodiment, the power supplied to the discharge lamp La is reduced according to the degree of decrease in the power supply voltage Vin, so that power lower than the rated power Ws0 is supplied to the discharge lamp La in the period TC. As a result, when the power supply voltage Vin decreases, an increase in the amount of heat generated with an increase in the power supply current Iin can be suppressed, and power loss can be reduced.

  Further, when the above-described discharge lamp lighting device 1 is configured as a vehicle-mounted headlamp using a discharge lamp La (high-intensity discharge lamp) with a rated power of 35 W, the ambient temperature Ta rises to 85 to 105 ° C. Therefore, the stable power target value is set in the range of 26 W to 35 W in consideration of the stable lighting of the discharge lamp La and the thermal stress of the components. In the present embodiment, the lower limit value Wla2 of the stable power target value is set to 26W, but the present invention is not limited to this.

Further, when a discharge lamp La (high-intensity discharge lamp) used for an on-vehicle headlamp is lit, as shown in FIGS. 5A to 5C, in order to stabilize the discharge lamp immediately after starting. , the provision of the electrode pressurizing heat period TE of raising the electrode temperature in a short period of time. As shown in FIG. 5 (b), when the DC power supply E1 is turned on, the voltage (discharge lamp voltage) supplied to the discharge lamp La rises, and the spark gap SG1 breaks down at time t0, so that the discharge lamp La Start (no-load period TD). Then, as shown in FIGS. 5B and 5C, in the electrode heating period TE, the electrodes of the discharge lamp La are heated by supplying predetermined power (discharge lamp voltage, discharge lamp current) to the discharge lamp La. To do. The length of the electrode heating period TE varies depending on the state of the discharge lamp La, but is set to several tens ms to several hundred ms. Further, since the discharge lamp La is likely to be extinguished when the electric power is changed during the electrode heating period TE, it is desirable to secure the period TA in FIG. 4 for 200 ms or more. Then, the luminous flux is raised by increasing the AC voltage supplied to the discharge lamp La in the luminous flux rising period TF, and predetermined alternating current power is supplied to the discharge lamp La in the stable lighting period TG (period TC).

  In addition, after starting the discharge lamp La, by keeping the maximum power Wp on, the discharge is more stabilized while promptly raising the luminous flux, thereby preventing flickering when the power is reduced in the period TB. Is possible. On the other hand, since the thermal stress of the component tends to increase as the maintenance time (period TA) of the maximum power Wp is increased, the period TA is preferably set to 5 seconds or less.

(Embodiment 2)
The discharge lamp lighting device 1 of the present embodiment is characterized in that the lower limit value Wla2 is reduced when the ambient temperature Ta is equal to or higher than the temperature Tth2 (first temperature).

  As shown by the broken line in FIG. 6, in the discharge lamp lighting device 1 of the first embodiment, the lower limit value Wla2 is constant at 26 W even if the ambient temperature Ta varies. However, in the discharge lamp lighting device 1 of the present embodiment, as shown by the solid line in FIG. 6, when the ambient temperature Ta exceeds the temperature Tth2, the stable power lower limit limiting unit 55 reduces the lower limit value Wla2.

  When the ambient temperature Ta exceeds the temperature Tth2, the amount of heat generated by the components increases, and the circuit loss increases relatively. Therefore, in the present embodiment, by reducing the lower limit value Wla2, it is possible to suppress the thermal stress of the circuit components and prevent the thermal destruction.

  In the present embodiment, the lower limit value Wla2 is gradually reduced as the ambient temperature Ta exceeds the temperature Tth2. Thereby, the lighting of the discharge lamp La can be maintained as much as possible. The stable power supplied to the discharge lamp La is reduced below the power necessary to keep the discharge lamp La lit by reducing the lower limit value Wla2, and the discharge lamp La is turned off naturally to stop the circuit operation. May be.

  In the present embodiment, the present invention is not limited to the case where the power supply voltage Vin that increases the circuit loss is low.

  Alternatively, the lower limit value Wla2 may be reduced when the time during which the ambient temperature Ta is equal to or higher than the temperature Tth2 is equal to or longer than a predetermined time ts1 (first time). For example, when the time ts1 is set to 10 seconds and the time when the ambient temperature Ta exceeds the temperature Tth2 is 10 seconds or more, the lower limit value Wla2 is reduced. As a result, even when the ambient temperature Ta exceeds the temperature Tth2, it is possible to maintain the discharge lamp La as much as possible. In this embodiment, the time ts1 is set to 10 seconds, but the time is not limited to 10 seconds.

  The above control is performed regardless of the power supply voltage Vin, and is not limited to, for example, the case where the power supply voltage Vin at which power loss increases is low.

(Embodiment 3)
The discharge lamp lighting device 1 according to the present embodiment is characterized in that when the ambient temperature Ta is equal to or higher than a temperature Tth3 (second temperature) higher than the temperature Tth2, power supply to the discharge lamp La is stopped.

  As shown by the broken line in FIG. 7, in the discharge lamp lighting device 1 of the second embodiment, the lower limit value Wla2 is reduced as the ambient temperature Ta exceeds the temperature Tth2, thereby maintaining the lighting of the discharge lamp La as much as possible. However, even when the ambient temperature Ta exceeds the abnormal temperature Tth3, the circuit operation is continued unless the discharge lamp La is naturally turned off. The abnormal temperature indicates a temperature that is outside the operating temperature range of the discharge lamp lighting device 1 or greatly exceeds the rated temperature of the components. In this embodiment, the temperature Tth3 = 160 ° C. is set.

  In the present embodiment, as shown by the solid line in FIG. 7, when the ambient temperature Ta exceeds the temperature Tth3, the control unit 5 stops the circuit operations of the DC / DC converter unit 2 and the inverter unit 3. Thereby, it is possible to prevent the thermal destruction of the circuit component due to the thermal stress. In the present embodiment, the temperature Tth3 = 160 ° C., which is an abnormal temperature, is set, but is not limited to this, and is generally set to 140 to 160 ° C.

  Further, the circuit operation is stopped and the power supply to the discharge lamp La is stopped when the time during which the ambient temperature Ta is equal to or higher than the temperature Tth3 is equal to or longer than a predetermined time ts2 (second time). May be. For example, when the time ts2 is set to 10 seconds and the time when the ambient temperature Ta exceeds the temperature Tth3 is 10 seconds or more, the circuit operation is stopped and the power supply to the discharge lamp La is stopped. Accordingly, even when the ambient temperature Ta exceeds the temperature Tth3, it is possible to maintain the lighting of the discharge lamp La as much as possible. In this embodiment, the time ts2 is set to 10 seconds, but is not limited to 10 seconds.

  The above control is performed regardless of the power supply voltage Vin, and is not limited to, for example, the case where the power supply voltage Vin at which power loss increases is low.

(Embodiment 4)
In the discharge lamp lighting device 1 of the present embodiment, the ambient temperature Ta becomes equal to or higher than the abnormal temperature Tth3, and after the power supply to the discharge lamp La is stopped, the ambient temperature Ta is lower than the temperature Tth3 (Tth4) When the temperature reaches below, the power supply to the discharge lamp La is resumed.

  In the discharge lamp lighting device 1 of the third embodiment, after the ambient temperature Ta exceeds the temperature Tth3 and the power supply to the discharge lamp La is stopped, the power supply to the discharge lamp La is performed even if the ambient temperature Ta becomes the temperature Tth3 or less. It remains stopped and the discharge lamp La is not lit.

  However, in the discharge lamp lighting device 1 of the present embodiment, after the ambient temperature Ta reaches the temperature Tth3 or higher and the power supply to the discharge lamp La stops, the ambient temperature Ta reaches a temperature Tth4 or lower that is lower than the temperature Tth3. Then, the power supply to the discharge lamp La is restarted, and the discharge lamp La is turned on. Accordingly, when the ambient temperature Ta is equal to or lower than the temperature Tth3 that is an abnormal temperature, it is possible to maintain the lighting of the discharge lamp La as much as possible.

  In the present embodiment, as shown in FIG. 8, the temperature Tth4 is set to be lower than the temperature Tth3. If it is set so that Tth4 = Tth3, the discharge lamp La is repeatedly turned on and off, whereby the self-temperature rise of the circuit repeatedly increases and decreases, and the circuit operation is repeated between circuit stop and operation return. Become. When this discharge lamp lighting device 1 is used for a vehicle headlamp, it may be recognized as flickering or passing of the discharge lamp La, and in order to prevent this, the temperature Tth4 is made smaller than the temperature Tth3. It is set. The temperature Tth4 is a uniquely determined temperature and is generally set at 110 to 130 ° C., but is not limited thereto.

  In this embodiment, as shown in FIG. 8, the temperature Tth4 is set to be lower than the temperature Tth2, but as shown in FIG. 9, the temperature Tth4 is set to be higher than the temperature Tth2. May be. Accordingly, by lowering the lower limit value Wla2, it is possible to prevent the thermal destruction of the thermal stress of the circuit component.

  In addition, when the time during which the ambient temperature Ta is equal to or lower than the temperature Tth4 is equal to or longer than the predetermined time ts3 (third time), the power supply to the discharge lamp La may be resumed. For example, when the time ts3 is set to 10 seconds and the time when the ambient temperature Ta is equal to or lower than the temperature Tth4 is 10 seconds or longer, the power supply to the discharge lamp La is resumed. Accordingly, when the ambient temperature Ta surely falls below the temperature Tth4, the power supply of the discharge lamp La is resumed, so that it is possible to suppress the thermal stress of the circuit components and prevent the thermal destruction. In this embodiment, the time ts3 is set to 10 seconds, but is not limited to 10 seconds.

  The above control is performed regardless of the power supply voltage Vin, and is not limited to, for example, the case where the power supply voltage Vin at which power loss increases is low.

(Embodiment 5)
FIG. 10 shows a schematic external view of the vehicle according to the present embodiment.

  In recent years, the engine room tends to be made smaller by securing the living space in the car as much as possible and reducing the weight to improve fuel efficiency. Therefore, in addition to the temperature in the engine room becoming higher, the discharge lamp lighting device 1 is set closer to the engine that generates a large amount of heat, so that the discharge lamp La is stable even in a small and higher temperature environment. There is a need for a discharge lamp lighting device 1 that can be lit.

  FIG. 10 shows a headlamp 11 composed of any one of the discharge lamp lighting devices 1 of Embodiments 1 to 4 and a discharge lamp La that is lit by the discharge lamp lighting device 1, and the headlamp 11. It is a schematic external view of the vehicle 12 provided with. When power is supplied from the low beam switch power supply 13 to the discharge lamp lighting devices 1 provided on the left and right sides, power is supplied from the discharge lamp lighting device 1 to the discharge lamp La, and the discharge lamp La is lit.

The headlamp 11 and the vehicle 12 use any one of the discharge lamp lighting devices 1 of the first to fourth embodiments. Thereby, even at a high temperature of the power supply voltage V in reducing the time and the ambient temperature Ta of, while reducing the thermal stress, since the lighting maintenance performance of the discharge lamp La can be secured, and safety is improved.

DESCRIPTION OF SYMBOLS 1 Discharge lamp lighting device 2 DC / DC converter part 3 Inverter part 4 Igniter part 5 Control part 6 Power supply voltage detection part 7 Temperature detection part 51 Power target memory | storage part 52 Stable power limiting part 53 Current target calculation part 54 Error amplifier 55 Stable power Lower limit part E1 DC power supply La discharge lamp

Claims (11)

In a discharge lamp lighting device that supplies power to a discharge lamp using a DC power supply as input,
A drive circuit for supplying power to the discharge lamp,
A control circuit for controlling the drive circuit;
A temperature detector that detects the ambient temperature or the temperature of the device itself;
A power supply voltage detector for detecting the voltage of the DC power supply,
The control circuit includes:
In the first period after the discharge lamp is started, the electric power supplied to the discharge lamp is increased from the first electric power to the second electric power lower than the first electric power to increase the temperature of the discharge lamp. To reduce accordingly,
In a second period that is continuous with the first period, the second power is supplied to the discharge lamp, and the degree of increase in the detection value of the temperature detection unit and the degree of reduction in the detection value of the power supply voltage detection unit reduce the second power according to the lower limit value is provided to the second power,
By making the amount of reduction of the second power an upper limit value, the second power becomes the lower limit value,
The control circuit includes a function using the first power reduction amount as a variable, and a first power reduction amount obtained by a function using the detection value of the temperature detection unit as a variable. The sum of the maximum value of the first reduction amount and the maximum value of the second reduction amount is the sum of the reduction amount of the second power. A discharge lamp lighting device characterized by being larger than an upper limit value .   The discharge lamp lighting device according to claim 1, wherein the control circuit reduces the lower limit value when a detection value of the temperature detection unit is equal to or higher than a first temperature. Wherein the control circuit, the time value detected by the temperature detector is the first temperature or higher, if it is the first time or more, release of claim 2, wherein the reducing the lower limit value Electric light lighting device.   4. The control circuit according to claim 1, wherein the control circuit stops power supply from the drive circuit to the discharge lamp when a detection value of the temperature detection unit is equal to or higher than a second temperature. The discharge lamp lighting device according to any one of the above.   The control circuit stops power supply from the drive circuit to the discharge lamp when the time when the detected value of the temperature detection unit is equal to or higher than the second temperature is equal to or longer than the second time. The discharge lamp lighting device according to claim 4.   The control circuit, after the detected value of the temperature detection unit is equal to or higher than the second temperature, and stops power supply from the drive circuit to the discharge lamp,
  6. The power supply from the drive circuit to the discharge lamp is resumed when a detection value of the temperature detection unit reaches a third temperature lower than the second temperature. The discharge lamp lighting device described.   The control circuit restarts the power supply from the drive circuit to the discharge lamp when the detection value of the temperature detection unit is equal to or less than the third time. The discharge lamp lighting device according to claim 6.   The control circuit, when the detection value of the temperature detection unit is equal to or higher than a first temperature, reduces the lower limit value,
  The discharge lamp lighting device according to claim 6 or 7, wherein the third temperature is equal to or higher than the first temperature.   The discharge lamp lighting device according to any one of claims 1 to 8, wherein the lower limit value is at least equal to or higher than a power value at which the discharge lamp within a lifetime can be kept on.   The discharge lamp lighting device according to any one of claims 1 to 9,
  A headlamp comprising: a discharge lamp that is turned on by the discharge lamp lighting device.   A headlamp according to claim 10;
  A vehicle comprising: a vehicle body to which the headlamp is attached.

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