JP2015082451A - Discharge lamp turn-on device and lighting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge lamp turn-on device capable of maintaining a discharge with small incremental power even when a lamp voltage rises when the discharge lamp is dimmed.SOLUTION: A discharge lamp turn-on device (1) comprises: a step-up converter (3) for boosting an input voltage and converting the boosted voltage to a direct-current output voltage; a step-down converter (4) for accepting an output voltage as input, limiting the output current, and supplying the limited current to a discharge lamp (9); a detection circuit (5) for detecting the current of the discharge lamp (9) and outputting the detected current, as well as detecting the voltage of the discharge lamp (9) and outputting the detected voltage; and a control circuit (8) for controlling the step-down converter (4) so that the detected current matches a target current value or a multiplied value of the detected current and detected voltage matches a target power value, and controlling the step-up converter (3) so that the output voltage is temporarily raised within a prescribed period before the voltage of the discharge lamp (9) stabilizes after the detected voltage starts rising in response to a reduction in the target current value or target power value.

Description

  The present invention relates to a discharge lamp lighting device and an illumination device using the same.

  2. Description of the Related Art Discharge lamp lighting devices are known in which the boost output of a boost converter is current-limited by a buck converter and supplied to a discharge lamp. Here, when dimming the lighting discharge lamp, if the lamp current is sharply reduced, the lamp voltage may temporarily rise. In this case, if the output voltage of the boost converter is insufficient with respect to the lamp voltage, the discharge is not maintained and the discharge lamp may go out.

  Patent Document 1 discloses a dimmable discharge lamp lighting device including a step-up converter (chopper circuit 1) and a step-down converter (chopper circuit 2). In the transition period from the start of the dimming operation until the discharge state of the lamp is stabilized, the output voltage of the boost converter is maintained at the output when all the lights are lit, and the output voltage is reduced when the transition period ends. Alternatively, the output voltage of the boost converter is increased during the entire period from the start to the end of the transient period. Thereby, the extinction during the dimming transition period in which the lamp voltage temporarily rises is prevented.

Japanese Patent No. 4239356

  According to the configuration of Patent Document 1, it is necessary to keep the output voltage of the boost converter high over the entire dimming transition period (and even before the synchronization period). However, if the period during which the output of the boost converter is high is longer than necessary, unnecessary power consumption occurs, which is not preferable from the viewpoint of energy saving.

  Accordingly, the present invention provides a discharge lamp lighting device and a lighting device using the same that maintain the discharge of the lamp with a small increase in power even when the lamp voltage increases when the discharge lamp is dimmed, thereby realizing high energy saving performance. The issue is to provide.

  A discharge lamp lighting device according to the present invention includes a boost converter that boosts an input voltage to convert it into a DC output voltage, a step-down converter that receives the output voltage and limits the output current to supply the discharge lamp, and a discharge lamp. A detection circuit that detects the current of the lamp and outputs a detection current and also detects the voltage of the discharge lamp and outputs the detection voltage, and a detection current and a detection voltage multiplied by the detection current so that the detection current matches the target current value The step-down converter is controlled so as to match the power target value, and after the detection voltage starts to rise in response to the reduction of the current target value or the power target value, it temporarily falls within a predetermined period until the discharge lamp voltage becomes stable. And a control circuit for controlling the boost converter so as to increase the output voltage.

  According to the discharge lamp lighting device having the above configuration, when the light is dimmed, after the lamp current or lamp power is reduced and the lamp voltage starts to rise, the boost converter is temporarily set within a predetermined period until the discharge lamp voltage becomes stable. The output voltage is increased. Therefore, unnecessary power consumption accompanying an increase in output voltage can be reduced as compared with a configuration in which the output voltage of the boost converter is increased over the entire dimming transition period (and before the same period).

  Here, it is preferable that the control circuit increases the output voltage over a period in which the voltage of the discharge lamp exceeds the threshold value. Thereby, the period during which the output voltage of the boost converter is raised can be optimized.

  Furthermore, when the current target value or the power target value is reduced, the control circuit may gradually decrease the current target value or the power target value continuously or stepwise. Thereby, since the rise width of the voltage of a discharge lamp is suppressed, the period and / or voltage width which raise the output voltage of a boost converter can be reduced, and further energy saving is attained.

  Further, the increase range of the output voltage may be determined according to the reduction range of the current target value or the power target value. Thereby, the increase width of the output voltage of the boost converter can be reduced as necessary, and further energy saving is possible.

  Further, the increase range of the output voltage may be determined corresponding to the difference between the voltage of the discharge lamp and the threshold value. As a result, the increase width and the increase period of the output voltage of the boost converter can be minimized, and further energy saving can be achieved.

  An illumination device of the present invention includes the discharge lamp lighting device and a discharge lamp, and the control circuit determines a current target value or a power target value according to a dimming signal input from the dimmer. Composed. Thereby, the illuminating device for light control which implement | achieves high energy-saving property can be provided.

It is a circuit block diagram which shows the discharge lighting device by embodiment of this invention, and an illuminating device containing the same. It is a figure explaining operation | movement of the discharge lighting device by 1st Example of this invention. It is a flowchart which shows operation | movement of the discharge lighting device by 1st Example of this invention. It is a figure explaining operation | movement of the discharge lighting device by the 2nd Example of this invention. It is a flowchart which shows operation | movement of the discharge lighting device by the 2nd Example of this invention. It is a figure explaining operation | movement of the discharge lighting device by the 3rd Example of this invention. It is a flowchart which shows operation | movement of the discharge lighting device by the 3rd Example of this invention.

  FIG. 1 shows an illumination device 10 including a discharge lamp lighting device 1 (hereinafter referred to as “lighting device 1”) according to an embodiment of the present invention. A power supply voltage from an AC power supply AC such as a commercial power supply and a dimming signal from the dimmer D are input to the lighting device 1, and all light or dimming output from the lighting device 1 is supplied to the discharge lamp 9. In this specification, dimming or dimming is not only the transition from full-light lighting to dimming lighting, but also from lighting at a predetermined dimming rate to lighting at a lower dimming rate. Including migration. In this specification, it is assumed that dimming or dimming is possible by reducing lamp current or lamp power.

  The lighting device 1 includes a rectifier circuit 2, a step-up converter 3, a step-down converter 4, a detection circuit 5, a full bridge circuit 6, a start circuit 7, and a control circuit 8. In the present embodiment, the discharge lamp 9 is a high-pressure discharge lamp. The rectifier circuit 2 is composed of a diode bridge, and full-wave rectifies the input voltage from the AC power supply AC. Note that the rectifier circuit 2 is not required when a DC power supply is input instead of an AC power supply.

  The step-up converter 3 includes a transistor 31 such as a MOSFET, a coil 32, a diode 33, and a smoothing capacitor 34. The step-up converter 3 steps up the rectified output of the rectifier circuit 2 and converts it to direct current. When the transistor 31 is turned on, a current flows from the coil 32 to the transistor 31, and energy is stored in the coil 32. When the transistor 31 is turned off, the current stored in the coil 32 causes a current to flow from the coil 32 to the diode 33 to the smoothing capacitor 34, and the smoothing capacitor 34 is charged. The transistor 31 is driven by a driver circuit included in the control circuit 8 described later, and the ON width (ON duty) of the transistor 31 is determined by the control circuit 8. In other words, the transistor 31 is PWM-controlled by the control circuit 8 and the output voltage of the boost converter 3 is determined.

  The step-down converter 4 includes a transistor 41 such as a MOSFET, a coil 42, a diode 43, and a capacitor 44, and outputs a limited current from the step-up output of the step-up converter 3. When the transistor 41 is turned on, current flows through the transistor 41 → the coil 42 → the full bridge circuit 6 described later → the discharge lamp 9, and energy is stored in the coil 42. When the transistor 41 is turned off, current flows in the coil 42 → the full bridge circuit 6 → the discharge lamp 9 → the diode 43 due to the energy stored in the coil 42. Capacitor 44 smoothes the output of step-down converter 4. The transistor 41 is driven by a driver circuit included in the control circuit 8, and the ON width (ON duty) of the transistor 41 is determined by the control circuit 8. In other words, the transistor 41 is PWM-controlled by the control circuit 8 and the output current of the step-down converter 4 is determined.

  The detection circuit 5 includes a voltage detection unit composed of a series circuit of resistors 51 and 52 and a current detection unit composed of a resistor 53. The resistors 51 and 52 are connected in parallel to the output terminal of the step-down converter 4 and detect the voltage of the discharge lamp 9 (hereinafter referred to as “lamp voltage”). A voltage generated in the resistor 52 shown at the node A is output to the control circuit 8 as a detection voltage. The resistor 53 is formed of a low resistance element, is inserted into the output current path of the step-down converter 4, and detects a current flowing through the discharge lamp 9 (hereinafter referred to as “lamp current”). A voltage generated in the resistor 53 shown at the node B is output to the control circuit 8 as a detection current. In the following description, the detection voltage and the detection current refer to either a voltage generated in the resistor 52 and the resistor 53, or a lamp voltage and a lamp current represented by these voltages, respectively.

  The full bridge circuit 6 constitutes a full bridge including transistors 61, 62, 63 and 64 made of MOSFET or the like, converts the DC output of the step-down converter 4 to AC, and supplies the AC output to the discharge lamp 9. Transistors 61 and 64 and transistors 62 and 63 are alternately turned on and off at a frequency of about 50 Hz to 1 kHz by a driver included in the control circuit 8. As a result, a rectangular wave lamp current having the above frequency is supplied to the discharge lamp 9.

  The start circuit 7 includes a resistor 71, a capacitor 72, a discharge gap 73, and a pulse transformer 74, and applies a start pulse to the discharge lamp 9 when the discharge lamp 9 is started. When the step-down converter 4 is activated, the output voltage is charged to the capacitor 72 via the resistor 71. When the charging voltage of the capacitor 72 exceeds the breakdown voltage of the discharge gap 73, the discharge gap 73 is conducted and the voltage of the capacitor 72 is applied to the primary winding of the pulse transformer 74. In response to this, a pulse voltage corresponding to the turn ratio of the pulse transformer 74 is generated in the secondary winding connected in series to the discharge lamp 9, and this pulse voltage is superimposed on the output voltage of the full bridge circuit 6 and released. Applied to the lamp 9. With this pulse superimposed voltage, the discharge lamp 9 breaks down and starts discharging. The starting circuit 7 stops after the discharge lamp 9 is started, and does not substantially affect the lighting operation of the discharge lamp.

  As described above, the detection voltage at the node A, the detection current at the node B, and the dimming signal from the external dimmer D are input to the control circuit 8. The control circuit 8 drives the transistor 31 of the step-up converter 3, the transistor 41 of the step-down converter 4, and the transistors 61 to 64 of the full bridge circuit 6. Specifically, the control circuit 8 performs PWM control on the transistor 31 so that the output voltage of the boost converter 3 becomes a predetermined value. For example, in boost converter 3 and control circuit 8, the output voltage may be feedforward controlled, or the output voltage is fed back so that the output voltage detected by an output voltage detection circuit (not shown) matches the voltage target value. It may be controlled. It is assumed that the output voltage is set to an appropriate value at each dimming rate, that is, a minimum voltage at which discharge of the discharge lamp 9 can be maintained or a voltage slightly higher than that.

  The control circuit 8 also PWM-controls the transistor 41 of the step-down converter 4 so that the detected current matches the current target value. That is, in the step-down converter 4 and the control circuit 8, the lamp current is feedback-controlled. The current target value is determined according to the dimming signal. Alternatively, the control circuit 8 performs PWM control on the transistor 41 of the step-down converter 4 so that the product of the detected current and the detected voltage matches the power target value. In this case, in the step-down converter 4 and the control circuit 8, the lamp power is feedback-controlled. The power target value is determined according to the dimming signal.

  As an outline of the operation at the time of dimming transition (when dimming), the control circuit 8 reduces the current target value or the power target value according to the dimming signal, and the lamp according to the reduction of the current target value or the power target value. After the voltage starts to rise, the output voltage of the boost converter 3 is temporarily raised within a predetermined period until the lamp voltage becomes stable. Thereby, unnecessary power consumption can be reduced as compared with the configuration in which the output voltage of the boost converter 3 is increased over the entire dimming transition period (particularly before the start of dimming). More specifically, the control circuit 8 increases the output voltage of the boost converter 3 over a period in which the lamp voltage exceeds a predetermined threshold in response to a temporary increase in the lamp voltage that occurs when the lamp current is reduced or the lamp power is reduced. . Thereby, the period during which the output voltage of boost converter 3 is raised can be optimized and shortened, and an increase in circuit power consumption can be suppressed. In the following embodiments, it is assumed that the lighting device 1 having the circuit configuration shown in FIG. 1 is used.

Example 1.
The operation of the lighting device 1 according to the first embodiment will be described with reference to FIG. In FIG. 2, the horizontal axis represents time, and the vertical axis represents the lamp current IL (or lamp power PL, hereinafter the same) before and after dimming transition, the lamp voltage VL, and the output voltage Vout of the boost converter 3. Note that the output voltage Vout before dimming transition (for example, at the time of all light) is set to V1.

  When the dimming signal from the dimmer D is received at the time t1, the control circuit 8 reduces the current target value (or power target value, the same applies hereinafter) to reduce the output current (or output power, the same applies hereinafter) of the step-down converter 4. ), That is, the lamp current IL is decreased. Thereafter, the lamp voltage VL starts to rise due to a sharp drop in the lamp current IL.

  When ramp voltage VL exceeds threshold value Vth at time t2, control circuit 8 raises output voltage Vout of boost converter 3 from V1 to V2.

  When ramp voltage VL becomes equal to or lower than threshold value Vth at time t3, control circuit 8 returns output voltage Vout of boost converter 3 from V2 to V1. Thereafter, the lamp voltage VL is stabilized at a predetermined voltage. In addition, after the time t3, for example, after the lamp voltage VL is stabilized, the output voltage Vout of the boost converter 3 may be lowered to a voltage Vd lower than V1 before dimming is started, as indicated by a broken line.

FIG. 3 shows a flowchart of the operation of the lighting device 1 according to this embodiment.
First, in step S100, the output voltage Vout of the boost converter 3 is set to the initial value V1.
In step S105, the control circuit 8 receives the dimming signal from the dimmer D.
In step S110, the control circuit 8 reduces the output current of the step-down converter 4 according to the dimming signal.

In step S115, the control circuit 8 determines whether or not the lamp voltage (detection voltage) VL exceeds the threshold value Vth. If the lamp voltage VL exceeds the threshold value Vth (step S115, YES), the process proceeds to step S120. Otherwise (step S115, NO), the process proceeds to step S135.
In step S120, control circuit 8 raises output voltage Vout of boost converter 3 to V2.

In step S125, the control circuit 8 determines whether or not the lamp voltage VL is equal to or lower than the threshold value Vth. If the lamp voltage VL is equal to or lower than the threshold value Vth (step S125, YES), the process proceeds to step S130. Otherwise (step S125, NO), the process repeats step S125.
In step S130, the control circuit 8 reduces the output voltage Vout of the boost converter 3 to V1.

In step S135, the control circuit 8 determines whether or not the lamp voltage VL is stable, that is, whether or not the discharge state of the discharge lamp 9 is stable. For example, the control circuit 8 can determine that the discharge state is stable when the differential value of the lamp voltage VL is acquired and the differential value becomes less than a predetermined value. If the lamp voltage VL is stable (step S135, YES), the process proceeds to step S140. Otherwise (step S135, NO), the process returns to step S115.
In step S140, control circuit 8 resets output voltage Vout of boost converter 3 to Vd, and the process ends. Note that step S140 may be omitted.

  As described above, since the output voltage Vout is increased from V1 to V2 only during the period when the lamp voltage VL exceeds the threshold value Vth, the output voltage is set to be high particularly before the start of dimming throughout the dimming transition period (for example, , V2), an increase in power consumption accompanying an increase in the output voltage of boost converter 3 can be reduced.

Example 2
In the first embodiment, the lamp current decrease at the time of dimming showed an instantaneous configuration, but in this embodiment, the lamp current at the time of dimming shows a continuous configuration. With reference to FIG. 4, operation | movement of the lighting device 1 by a present Example is demonstrated. 4, the horizontal axis represents time, and the vertical axis represents the lamp current IL (or lamp power PL, hereinafter the same), the lamp voltage VL, and the output voltage Vout of the boost converter 3 before and after the dimming transition. The output voltage Vout before light transition (for example, all light) is set to V1. In this embodiment, an example in which the lamp current is continuously reduced is shown, but a configuration in which the lamp current is gradually reduced over a plurality of stages may be employed.

  When the dimming signal from the dimmer D is received at time t1, the control circuit 8 gradually reduces the current target value (or power target value, hereinafter the same) at a predetermined speed, and outputs the output current of the step-down converter 4 ( Alternatively, the output power (hereinafter the same), that is, the lamp current IL is gradually decreased. Here, the lamp voltage VL starts to rise gently due to the decrease in the lamp current IL. As described above, by slowing down the decrease rate of the lamp current IL, the temporary increase of the lamp voltage VL is reduced as compared with the case where the lamp current IL is instantaneously decreased.

  When ramp voltage VL exceeds threshold value Vth at time t2, control circuit 8 raises output voltage Vout of boost converter 3 from V1 to V2. In the present embodiment, the voltage width over which the lamp voltage VL exceeds the threshold value Vth is expected to be smaller than that in the first embodiment. Therefore, V2 in this embodiment may be lower than V2 in the first embodiment. .

  When ramp voltage VL becomes equal to or lower than threshold value Vth at time t3, control circuit 8 returns output voltage Vout of boost converter 3 from V2 to V1. Thereafter, the lamp voltage VL is stabilized at a predetermined voltage. Note that, for example, after the lamp voltage VL is stabilized after the time t3, the output voltage Vout of the boost converter 3 may be lowered to a voltage Vd lower than V1 before dimming starts, as indicated by a broken line.

FIG. 5 shows a flowchart of the operation of the lighting device 1 according to this embodiment.
As in the first embodiment, the output voltage Vout is set to the initial value V1 in step S100, and the dimming signal from the dimmer D is received in step S105.
In step S112, the control circuit 8 starts reducing the output current of the step-down converter 4 at a predetermined rate of reduction according to the dimming signal.

In step S115, the control circuit 8 determines whether or not the lamp voltage (detection voltage) VL exceeds the threshold value Vth. If the lamp voltage VL exceeds the threshold value Vth (step S115, YES), the process proceeds to step S120. Otherwise (step S115, NO), the process proceeds to step S132.
In step S120, control circuit 8 raises output voltage Vout of boost converter 3 to V2.

In step S125, the control circuit 8 determines whether or not the lamp voltage VL is equal to or lower than the threshold value Vth. If the lamp voltage VL is equal to or lower than the threshold value Vth (step S125, YES), the process proceeds to step S130. Otherwise (step S125, NO), the process repeats step S125.
In step S130, the control circuit 8 reduces the output voltage Vout of the boost converter 3 to V1.

  In step S132, when the reduction of the output current of step-down converter 4 is completed, that is, when the dimming transition is completed (YES in step S132), the process proceeds to step S135, and the dimming transition is completed. If not (NO in step S132), the process returns to step S115.

  As in the first embodiment, in step S135, it is determined whether or not the lamp voltage VL is stable. If the lamp voltage VL is stable (YES in step S135), the process proceeds to step S140, and otherwise ( In step S135, NO), the process returns to step S115. In step S140, the output voltage Vout is reset to Vd, and the process ends. Note that step S140 may be omitted.

  In the present embodiment, a temporary increase in the lamp voltage VL is suppressed by reducing the decrease in the lamp current IL, and as a result, the period and voltage in which the lamp voltage VL exceeds the threshold value Vth are reduced as compared with the first embodiment. . Therefore, the period (t2-t1) and / or the voltage width (V2-V1) during which the output voltage Vout of the boost converter 3 is raised can be further reduced, and the power consumption can be further reduced.

Example 3
In the first embodiment, the configuration in which the increase in the output voltage of the boost converter 3 is a constant voltage width is shown. However, in this embodiment, the configuration in which the increase width of the output voltage is determined according to the difference between the ramp voltage and the threshold value. Show. The operation of the lighting device 1 according to the third embodiment will be described with reference to FIG. Also in FIG. 6, the horizontal axis represents time, and the vertical axis represents the lamp current IL (or lamp power PL, the same applies hereinafter), the lamp voltage VL, and the output voltage Vout of the boost converter 3 during the dimming transition. The output voltage Vout before light transition (for example, all light) is set to V1.

  When the dimming signal is received from the dimmer D at time t1, the control circuit 8 reduces the current target value (or power target value, the same applies hereinafter) to output current of the step-down converter 4 as in the first embodiment. (Or output power, the same applies hereinafter), that is, the lamp current IL is reduced. Here, the lamp voltage VL starts to increase due to the steep decrease in the lamp current IL.

  When the ramp voltage VL exceeds the threshold Vth at time t2, the control circuit 8 increases the output voltage corresponding to the difference ΔVL between the ramp voltage VL and the threshold Vth, and the difference in the increase width ΔVout of the output voltage Vout of the boost converter 3 Corresponding to ΔVL sequentially. For example, the increase width ΔVout may be monotonously increased (proportional or the like) with respect to the difference ΔVL.

  When ramp voltage VL becomes equal to or lower than threshold value Vth at time t3, control circuit 8 returns output voltage Vout of boost converter 3 to V1. Thereafter, the lamp voltage VL is stabilized at a predetermined voltage. Note that, for example, after the lamp voltage VL is stabilized after the time t3, the output voltage Vout of the boost converter 3 may be lowered to a voltage Vd lower than V1 before dimming starts, as indicated by a broken line.

FIG. 7 shows a flowchart of the operation of the lighting device 1 according to this embodiment.
As in the first embodiment, the output voltage Vout is set to the initial value V1 in step S100, the dimming signal from the dimmer D is received in step S105, and the voltage is stepped down according to the dimming signal in step S110. The output current of the converter 4 is reduced.

  In step S115, the control circuit 8 determines whether or not the lamp voltage (detection voltage) VL exceeds the threshold value Vth. If the lamp voltage VL exceeds the threshold value Vth (step S115, YES), the process proceeds to step S122. Otherwise (step S115, NO), the process proceeds to step S135.

  In step S122, the control circuit 8 increases the output voltage Vout of the boost converter 3 according to the difference ΔVL between the ramp voltage VL and the threshold value Vth. For example, the output voltage Vout may be determined so that Vout = V1 + α × ΔVL (α is a constant).

  In step S125, the control circuit 8 determines whether or not the lamp voltage VL is equal to or lower than the threshold value Vth. If the lamp voltage VL is equal to or lower than the threshold value Vth (step S125, YES), the process proceeds to step S130. Otherwise (step S125, NO), the process returns to step S122. At step S130, the output voltage Vout of the boost converter 3 is V1.

  As in the first embodiment, in step S135, it is determined whether or not the lamp voltage VL is stable. If the lamp voltage VL is stable (YES in step S135), the process proceeds to step S140, and otherwise ( In step S135, NO), the process returns to step S115. In step S140, the output voltage Vout is reset to Vd, and the process ends. Note that step S140 may be omitted.

  As described above, the increase width ΔVout of the output voltage Vout of the boost converter 3 is determined in accordance with the difference between the ramp voltage VL and the threshold value Vth, so that the output voltage increase width of the boost converter 3 is minimized. This can further reduce power consumption.

<Modification>
Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above-described configuration, and various modifications can be made as described below.

Determination of output voltage increase width of boost converter 3 In the first and second embodiments, the configuration in which the output voltage increase width of the boost converter 3 is determined in advance is shown. It is good also as a structure determined according to the fall of the dimming rate which the dimming signal from No. shows. That is, in the control circuit 8, the increase width of the output voltage may be determined in accordance with the reduction range of the target current value or the power target value. Specifically, the larger the dimming rate drop (decrease width, lowering rate, etc.), the larger the output voltage rise, and conversely, the smaller the dimming rate drop, the smaller the output voltage rise. You can do it. Thus, by reducing the increase width of the output voltage of the boost converter, an increase in circuit power consumption can be further suppressed.

In the above-described embodiments, the output voltage increase mode of the boost converter 3 is determined based on the relationship between the lamp voltage and the threshold value. It is good also as a structure determined by the data previously memorize | stored in FIG. For example, the relationship between the drop in the dimming rate and the rise curve of the lamp voltage may be acquired in advance by experiment and stored in the memory of the control circuit 8. The control circuit 8 determines the output voltage rise start timing, the length of the rise period, and / or the voltage rise width in accordance with the drop in the dimming rate indicated by the dimming signal from the dimmer D. It is good. Note that when the drop of the dimming rate is large, the output voltage rise start timing of the boost converter 3 may be early, the rise period may be long, and / or the voltage rise width may be large.

-Combination of Embodiments Although each of the above-described embodiments has been shown as being individual, Embodiment 2 and Embodiment 3 may be applied in combination. That is, while the current target value or the power target value, that is, the output current or output power of the step-down converter 4 is gradually decreased stepwise or stepwise, the step-up converter 3 is increased by the increase width corresponding to the difference between the lamp voltage and the threshold value. The output voltage may be increased.

-Types of discharge lamps In the above embodiment, a discharge lamp lighting device for alternating current lighting has been shown. However, the present invention, for example, discharge lamp lighting for direct current lighting for lighting a high pressure discharge lamp for direct current lighting, etc. It can also be applied to the device. In the case of DC lighting, the full bridge circuit 6 is not necessary. In the above embodiment, a high pressure discharge lamp is exemplified as the discharge lamp 9. However, the present invention is directed to any discharge lamp lighting device having the property that the lamp voltage temporarily rises when the lamp current is reduced or the lamp power is reduced. It is applicable to.

1 Discharge lamp lighting device (lighting device)
DESCRIPTION OF SYMBOLS 3 Boost converter 4 Buck converter 5 Detection circuit 8 Control circuit 9 Discharge lamp 10 Illumination device

Claims (6)

A discharge lamp lighting device,
A boost converter that boosts the input voltage and converts it to a DC output voltage;
A step-down converter that receives the output voltage and limits the output current to supply the output to the discharge lamp;
A detection circuit for detecting a current of the discharge lamp and outputting a detection current and detecting a voltage of the discharge lamp and outputting a detection voltage;
The step-down converter is controlled so that the detected current matches a current target value or a multiplication value of the detected current and the detected voltage matches a power target value, and the current target value or the power target value A control circuit that controls the boost converter so as to temporarily increase the output voltage within a predetermined period after the detection voltage starts increasing according to the decrease until the voltage of the discharge lamp becomes stable. Discharge lamp lighting device.   The discharge lamp lighting device according to claim 1, wherein the control circuit increases the output voltage over a period in which the detected voltage exceeds a threshold value.   3. The discharge lamp lighting device according to claim 2, wherein when the current target value or the power target value is reduced, the control circuit gradually increases the current target value or the power target value continuously or stepwise. A discharge lamp lighting device configured to be lowered.   The discharge lamp lighting device according to any one of claims 1 to 3, wherein an increase width of the output voltage is determined in accordance with a reduction width of the current target value or the power target value.   The discharge lamp lighting device according to claim 2 or 3, wherein an increase width of the output voltage is determined according to a difference between the detected voltage and the threshold value. The discharge lamp lighting device according to any one of claims 1 to 5 and the discharge lamp, wherein the control circuit determines the current target value or the current according to a dimming signal input from a dimmer. A lighting device configured to determine a power target value.

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