JP4117562B2 - Discharge lamp lighting device - Google Patents

Description

  The present invention relates to a discharge lamp lighting device for dimming and lighting a discharge lamp using an inverter circuit.

  A conventional dimmable discharge lamp lighting device includes a lighting detection circuit for detecting that the discharge lamp is lit, and a control circuit for controlling the output of the dimming switching circuit when the lighting detection circuit detects that the discharge lamp is lit. Output control means that enables input to the lamp, even when the dimming switching circuit is switched to the dimming mode when the discharge lamp is lit, until the lighting detection circuit detects that the discharge lamp is lit. The inverter circuit is operated in the lighting mode so that the discharge lamp is easily lit, and when the discharge lamp is lit, the inverter circuit is quickly operated in the dimming mode (for example, Patent Document 1). .

JP-A-2-284389

  In the conventional discharge lamp lighting device, even when the discharge lamp lighting is switched to the dimming mode, the lighting of the discharge lamp is detected by lighting in the full lighting mode until the lighting of the discharge lamp is detected. After switching to the dimming mode, even when trying to turn on the light in the dimming mode, when the discharge lamp is started, the operation is switched to the dimming lighting after the all-lights are on. Even when the lamp is lit with a low luminous flux, the lamp is once lit in a high luminous flux state, which gives the user an unnatural impression, and changes in the stimulus to the eyes are large, which is undesirable from the viewpoint of eye health. .

  The present invention has been made in view of the above problems, and when starting the discharge lamp, the discharge lamp can be started smoothly at a set dimming degree, giving an unnatural impression to the user. It aims at obtaining the discharge lamp lighting device which does not have.

A discharge lamp lighting device according to the present invention outputs a DC power supply, an inverter circuit that converts the DC power supply voltage into a high-frequency voltage by a switching operation of the switching element to light the discharge lamp at a high frequency, and a driving frequency of the switching element. A frequency control circuit, and a drive circuit that drives the switching element based on the frequency output by the frequency control circuit;
Wherein the frequency control circuit, when starting the discharge lamp, within a predetermined period, a period for outputting a first drive frequency causes generate sufficient high frequency voltage to light the discharge lamp in the zero, first A second driving frequency higher than the first driving frequency is output, and thereafter, every time a predetermined period elapses, a period during which the second driving frequency is output is gradually shortened, and the first driving frequency is output. The control is performed so that the period is gradually increased .

The discharge lamp lighting device of this invention, when starting the discharge lamp, within a predetermined period, a period for outputting a first drive frequency causes generate sufficient high frequency voltage to light the discharge lamp in the zero, A second drive frequency higher than the first drive frequency is output, and thereafter, every time a predetermined period elapses, the output period of the second drive frequency is gradually shortened, and the first drive frequency Because the control to gradually increase the output period is performed , the change in the stimulus to the vision is small, and even if it is lit at a low dimming level, it will not be lit once in the high intensity state as before , Does not give the user an unnatural impression.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a circuit configuration of a discharge lamp lighting device according to an embodiment of the present invention.
In FIG. 1, 1 is a DC power source, 2 and 3 are switching elements that are connected in series and convert a DC voltage of the DC power source 1 into a high-frequency voltage, and constitute a half-bridge inverter circuit. 4 is a frequency control circuit that determines an inverter drive frequency in accordance with, for example, a dimming degree command set from the outside, and generates the drive frequency. 5 is an inverter drive frequency generated and output by the frequency control circuit 4. A driving circuit 6 for driving the switching elements 2 and 3 is a load circuit including a discharge lamp 9 including a ballast choke coil 7, a capacitor 8, and a filament (not shown). In the load circuit 6, the ballast choke coil 7 and the capacitor 8 constitute a series resonance circuit, and the discharge lamp 9 is connected in parallel with the capacitor 8.

  First, the basic operation of the discharge lamp lighting device shown in FIG. 1 will be described with reference to FIGS. FIG. 2 shows the relationship between the inverter drive frequency f before the discharge of the discharge lamp 9 and the capacitor voltage VC generated at both ends of the capacitor 8 in the load circuit 6, and FIG. 3 flows through the inverter drive frequency f and the discharge lamp 9. It shows the relationship of the lamp current IL.

  The discharge lamp 9 is started by applying a high voltage to the discharge lamp 9 using the series resonance circuit of the ballast choke coil 7 and the capacitor 8 of the load circuit 6. In this case, as shown in FIG. 2, the inverter drive frequency f is set to f1 in the vicinity of the series resonance frequency f0 of the ballast choke coil 7 and the capacitor 8, a high voltage is generated at both ends of the capacitor 8, and the high voltage is released. The discharge lamp 9 is started by being applied to the electric lamp 9.

In the dimming operation of the discharge lamp 9, the DC voltage of the DC power source 1 is converted into a high frequency voltage by the inverter circuit of the switching elements 2 and 3, and applied to the discharge lamp 9. At this time, the drive frequency of the inverter circuit The discharge lamp 9 is dimmed by utilizing the fact that the impedance of the ballast choke coil 7 varies depending on the frequency. Here, the DC power source 1 is, for example, a constant voltage source. When the drive frequency f of the inverter is increased as shown in FIG. 3 (f2 in FIG. 3), the impedance of the ballast choke coil 7 increases, so that the lamp current IL is When the inverter driving frequency f is decreased (f1 in FIG. 3), the impedance of the ballast choke coil 7 is low, so that the lamp current IL flowing through the discharge lamp 9 becomes the lamp current IL1. To increase. Thus, by changing the drive frequency f of the inverter, the lamp current IL changes and the discharge lamp 9 is dimmed.

Following the basic operation, the operation according to the present invention will be described with reference to FIGS.
FIG. 4 shows an operation state of switching of the inverter drive frequency f, and FIG. 5 is a diagram schematically showing the lamp current IL flowing through the discharge lamp 9 at that time.
As shown in FIG. 4, the inverter drive frequency f is switched between the first drive frequency f1 and the second drive frequency f2 at a predetermined period T.
Here, the first frequency f1 is a frequency at which a high voltage (starting voltage) sufficient for starting the discharge lamp 9 can be generated in the vicinity of the series resonance frequency by the ballast choke coil 7 and the capacitor 8. The second frequency f2 is a frequency set higher than the first frequency f1. (The same applies to Embodiments 2 to 5 below.)

The second frequency f2 cannot generate a sufficiently high voltage (starting voltage) for discharging the discharge lamp 9 before the discharge lamp 9 is discharged as shown in FIG. Since the discharge state of the discharge lamp 9 can be maintained at a voltage lower than the starting voltage after the light 9 is turned on, the light can be turned on with a low luminous flux at the second frequency f2.
Therefore, as shown in FIG. 4, the inverter drive frequency f is switched at the predetermined cycle T between the first drive frequency f1 and the second drive frequency f2 and output, and a high voltage is applied to the discharge lamp 9 for discharge. The frequency control circuit 4 controls the driving period T1 with the first frequency f1 to give a voltage for maintenance and the driving period T2 with the second frequency set to a frequency higher than the first frequency f1. To generate. That is, control is performed so that the period during which the first drive frequency f1 and the second drive frequency f2 of the inverter drive frequency are output is relatively changed within a predetermined period. Based on this inverter drive frequency information, the drive circuit 5 drives the inverter circuit composed of the switching elements 2 and 3.

At this time, the lamp current IL flowing through the discharge lamp 9 has, for example, an inverter driving frequency f with a predetermined period T as shown in FIG. 4 (a), and T1 << T2 during the period T. When set, the lamp current waveform shown in FIG. In this case, when the lamp current IL1 that flows during the driving period of T1 and the lamp current IL2 that flows during the driving period of T2 are set, the lamp current IL that flows through the discharge lamp 9 during the period of T is expressed by the following relationship: Can do.
IL = IL1 * T1 / T + IL2 * T2 / T (1)
Here, for example, the first frequency f1 and the second frequency f2 in the inverter driving frequency f are set so that the lamp current IL1 = 100 mA IL2 = 5 mA, and the ratio of T1 and T2 is set to 1: 9. In this case, the lamp current IL in the period T is 14.5 mA from the above equation (1), and the luminous flux of the discharge lamp 9 is equivalent to the case where an average lamp current of 14.5 mA flows. The period T is preferably set to several hundred Hz or more in a sufficiently short period such that the difference between the lamp currents IL1 and IL2 is not felt as flicker.

  Further, when T1 = T2 (that is, 5: 5) as shown in FIG. 4B, the lamp current IL flowing through the discharge lamp 9 has a current waveform shown in FIG. The lamp current IL in this case is 52.5 mA from the above equation (1), and the speed of light of the discharge lamp 9 is equivalent to the case where an average lamp current of 52.5 mA flows. Further, as shown in FIG. 4C, when T1 >> T2 (for example, T1: T2 = 9: 1), the lamp current IL flowing through the discharge lamp 9 has the current waveform shown in FIG. From (1), the lamp current IL is 90.5 mA, and the speed of light of the discharge lamp 9 is equivalent to the case where an average lamp current of 90.5 mA flows.

  As described above, in the predetermined period T, the driving is performed based on the inverter driving frequency by switching the driving period T1 by the first driving frequency f1 and the driving period T2 by the second driving frequency f2 in the period T. The inverter circuit including the switching elements 2 and 3 is driven by the circuit 5 and the discharge lamp 9 is dimmed. The lamp current IL flowing through the discharge lamp 9 is equal to the first frequency f1 and the second frequency with respect to the period T. Is determined by the time ratio of the frequency f2, i.e., the ratio of T1 and T2. In the time ratios T1 and T2, the time ratio T1 between the first drive frequency f1 and the second drive frequency f2 according to the dimming degree command set from the outside shown in FIG. T2 is determined by the frequency control circuit 4, and is generated by controlling the inverter drive frequency by the frequency control circuit 4 so that the drive period T1 by the first frequency f1 and the drive period T2 by the second frequency f2 are obtained. The circuit will be operated.

For example, when a dimming degree command signal having a dimming degree of 10% (for example, corresponding to the lamp current IL = 14.5 mA described above) is input to the frequency control circuit 4 from the outside, the first frequency f1 is set. And the time ratio between T1 and T2 of the second frequency f2 is determined to be 1: 9, and for example, a dimming degree command signal with a dimming degree of 30% (when the lamp current IL is equivalent to 52.5 mA) is obtained. If input, the time ratio between T1 and T2 is determined to be 5: 5. In this way, the inverter drive frequency is controlled by the frequency control circuit 4 so as to be the first frequency f1 and the second frequency f2 at the time ratio of T1 and T2 determined according to the dimming degree command set from the outside. The drive circuit 5 operates the inverter circuit based on the drive frequency information.

  As described above, in the present embodiment, at the time of dimming, the inverter drive frequency is switched between the first drive frequency f1 and the second drive frequency f2 at a predetermined period T, and a high voltage is applied to the discharge lamp 9. The frequency control circuit 4 has a driving period T1 based on the first frequency f1 for applying a voltage for maintaining discharge and a driving period T2 based on the second frequency f2 set to a frequency higher than the first frequency f1. Based on this inverter drive frequency, the drive circuit 5 drives the inverter circuit composed of the switching elements 2 and 3 based on this inverter drive frequency. The lamp current IL flowing through the discharge lamp 9 at this time is determined by the time ratio between T1 and T2 of the first frequency f1 and the second frequency f2 with respect to the period T, and this time ratio is adjusted from the outside. Since the determination is made according to the luminous intensity command, the discharge lamp 9 can be smoothly dimmed to the dimming degree according to the dimming degree command. For this reason, even when the light is turned on at a low dimming level, the light is not once turned on in the high-light intensity state as in the prior art, so that an unnatural impression is not given to the user.

In the above embodiment, the DC power source 1 is a constant voltage source. However, a DC power source obtained by rectifying and smoothing a commercial power source may be used. (The same applies to Embodiments 2 to 5 below.)

In the above embodiment, the discharge lamp 9 is a discharge lamp provided with a filament. Usually, in the case of such a discharge lamp, an operation for preheating the filament is added before the discharge lamp is turned on. Since is not directly related to the present invention, description thereof is omitted. (The same applies to Embodiments 2 to 5 below.)

Embodiment 2. FIG.
In the first embodiment, the inverter driving frequency is switched between the first driving frequency f1 and the second driving frequency f2 with respect to the predetermined period T, and the lamp current IL flowing through the discharge lamp 9 is changed to the first frequency f1. Is determined by the time ratio between the periods T1 and T2 of the second frequency f2 and is lit smoothly according to a dimming degree command from the outside. In the present embodiment, the discharge lamp When starting and lighting 9, the output is smoothly changed from a low luminous flux to a predetermined dimming level (hereinafter referred to as fade-in lighting).
Note that the circuit configuration and the like of the discharge lamp lighting device in the present embodiment are the same as those in FIG. 1 of the first embodiment, and therefore illustration and description thereof are omitted here.

FIG. 6 is a diagram in which the horizontal axis represents time in the switching operation state of the first drive frequency f1 and the second drive frequency f2 of the inverter drive frequency with respect to the predetermined period T in the present embodiment, and FIG. FIG. 8 is an enlarged view of the switching operation between the first frequency f1 and the second frequency f2 during the period (a) to (f) shown in FIG. 6, and FIG. 8 shows (a) to (f). The figure which represented typically the lamp current IL which flows into the discharge lamp 9 in each period is shown.

Next, the operation in this embodiment will be described with reference to FIGS.
In FIG. 6, the ratio of the period T1 with the first frequency f1 is gradually increased in the time ratio between the driving period T1 with the first frequency f1 and the driving period T2 with the second frequency f2 with respect to the predetermined period T. In the period (a) in the figure, the T1 ratio of the first frequency f1 to the period T is 0%, and similarly, the period (b) is 10% and the period (c). In the following description, it is assumed that 30% is set to 50% in the period (d), 80% in the period (e), and 100% in the period (f).

Due to the change in the T1 ratio of the first drive frequency f1 with respect to the period T in each period from FIG. 6A to FIG. 6F, the lamp current IL flowing through the discharge lamp 9 in each period is shown in FIG. ) To (f). For example, if the lamp current IL1 at the first frequency f1 of the inverter driving frequency is set to 100 mA and the lamp current IL2 at the second frequency f2 is set to 5 mA as in the first embodiment, the period of (a) is set. Since the T1 ratio of the first frequency f1 to the period T is 0% and only the second frequency f2, as described above, the second frequency f2 is sufficient to discharge the discharge lamp 9. Since a high voltage (starting voltage) cannot be generated, the discharge lamp 9 is not lit and the lamp current IL does not flow.

  Next, in the period (b), since the ratio T1 of the first frequency f1 with respect to the period T is 10%, a high voltage sufficient to start the discharge lamp 9 can be generated. The lamp current IL that is lit and then flows through the discharge lamp 9 has a ratio of T1 and T2 of 1: 9. Therefore, an average of 14.5 mA in the period of the period T from the equation (1) described in the first embodiment. It becomes.

Subsequently, in the period (c), since the ratio of T1 to the period T is 30%, the ratio of T1 and T2 is 3: 7. Similarly, the lamp current IL in the period T is averaged from the expression (1). 33.5 mA. Similarly, in the period (d), the T1 ratio is 50%, so the lamp current IL in the period T is an average of 52.5 mA, and in the period (e), the T1 ratio is 80%. The lamp current IL during the period T is an average of 81 mA. Further, in the period (f), since the T1 ratio is 100%, the lamp current IL in the period T is 100 mA.

Then, after receiving a dimming degree command set from the outside, when the first driving frequency f1 and the second driving frequency f2 of the inverter driving frequency are switched for a predetermined period T, the driving is performed as described above. In this manner, the ratio of T1 driven at the first frequency f1 to the period T is gradually increased from zero, so that the lamp current IL flowing through the discharge lamp 9 is gradually increased and fade-in lighting is performed. To work.

That is, for example, the dimming degree is 30% from the outside (when the T1 ratio of the frequency f1 is equivalent to the lamp current IL = 52.5 mA at 50%), or the dimming degree is 50% (the T1 ratio of the frequency f1 is When the dimming degree command signal is input to the frequency control circuit 4 (when the lamp current IL at 100% corresponds to 100 mA), the frequency control circuit 4 sets the inverter drive frequency to the first period T. The ratio of T1 driven at the frequency f1 is controlled so as to gradually become 50% or 100% from zero. Based on this inverter drive frequency information, the drive circuit 5 comprises the switching elements 2 and 3. Drives the inverter circuit. As a result, the lamp current IL flowing through the discharge lamp 9 gradually increases from zero, and fade-in lighting is performed so that the lamp current IL = 52.5 mA or 100 mA corresponding to the dimming degree of 30% or 50%. To do.

In the present embodiment, as described above, the T1 ratio of the first drive frequency f1 to the period T is 100%, that is, the period T1 of the first drive frequency f1 reaches the entire period of the predetermined period T ( Up to a predetermined dimming degree (for example, the dimming degree of 50%) during the period (f) in FIG. 6, for example, the T1 ratio with respect to the cycle T is zero as described above according to the dimming degree command set from the outside. From 10%, 30%, 50%, 80%, and 100%.

  As described above, for example, when the first drive frequency f1 and the second drive frequency f2 of the inverter drive frequency are switched and driven after receiving a dimming degree command set from the outside, the first T with respect to the cycle T Since the operation is performed so that the ratio of T1 driven at the frequency f1 gradually increases from zero, fade-in lighting is possible when lighting at the set dimming level, and the dimming level according to the dimming degree command is smoothly released. The electric light 9 can be turned on. Therefore, even when the light is turned on at a low dimming level, the light is not once turned on in the high light intensity state as in the conventional case, and thus an unnatural impression is not given to the user as in the first embodiment.

Embodiment 3 FIG.
In the first and second embodiments, the inverter drive frequency is switched between the first drive frequency f1 and the second drive frequency f2, and the lamp current IL flowing through the discharge lamp 9 is changed to the first frequency f1 and the second drive frequency f2. It is determined by the time ratio of the frequency f2 to the period T, that is, the ratio of T1 and T2, and when the ratio of the driving period T1 to the period T is 100%, for example, the predetermined dimming degree is set to 50%. Up to this point, the ratio of the period T1 to the period T is gradually increased from zero according to the set dimming degree, and the dimming lighting is performed. In the present embodiment, the ratio of the driving period T1 of the first frequency f1 to the period T is 100%. For example, from the predetermined dimming degree 50%, the dimming degree is further increased and the dimming lighting control is performed until all lights are turned on. The form of the case.
Note that the circuit configuration and the like of the discharge lamp lighting device in the present embodiment are the same as those in FIG. 1 of the first embodiment, and thus illustration and description thereof are omitted here.

Next, the present embodiment will be described with reference to FIGS. 6, 7, and 8 used in the second embodiment. 6 is the same as that in the second embodiment, and thus the description thereof will be omitted. Here, the first driving with respect to the cycle T is omitted. The dimming lighting control from the period (f) in which, for example, the predetermined dimming degree is 50% to the subsequent all-light lighting when the T1 ratio of the frequency f1 is 100% is described.

In order to perform the dimming lighting control so as to increase the dimming degree from the period (f) to the full light lighting, it can be understood from the relationship between the inverter driving frequency f and the lamp current IL shown in FIG. 3 of the first embodiment. As described above, the lamp current IL increases as the inverter drive frequency f is further lowered from the frequency f1, so that the period from the period (f) in FIG. 6 to the subsequent all-light lighting is indicated by a dotted line in the period (g). In addition, the inverter drive frequency f is lowered from the first frequency f1 at which the T1 ratio becomes 100%, for example, to the inverter drive frequency fn where the light is turned on, for example, depending on the dimming degree command set from the outside. By doing so, it is possible to perform dimming lighting control. Incidentally, the lamp current ILn defined by the inverter drive frequency fn when the discharge lamp 9 is in the all-light lighting state is as shown in (g) of FIG.

In the period (g), for example, when a signal of 80% dimming level or an all-lighting lighting command is input from the outside to the frequency control circuit 4, the inverter is driven according to the 80% dimming level or the all-lighting lighting command. The frequency control circuit 4 controls and generates the frequency fx or fn, and the inverter circuit including the switching elements 2 and 3 is driven by the drive circuit 5 on the basis of the drive frequency information. %, Or a lamp current corresponding to the all-light lighting command flows to the discharge lamp 9, and the dimming lighting control is performed.

  As described above, in this embodiment, when the T1 ratio of the first drive frequency f1 is 100%, for example, the dimming degree is further increased from the period (f) in FIG. 6 where the predetermined dimming degree is 50%. When dimming control is performed until all the lights are turned on, the inverter drive frequency is lowered from the drive frequency f1 at which the T1 ratio becomes 100%, and, for example, the inverter drive frequency fn where the all light is turned on is set from the outside. The inverter control frequency is controlled by the frequency control circuit 4 in accordance with the dimming degree command, so that the dimming control is performed. Therefore, from the dimming by frequency switching at the inverter driving frequencies f1 and f2, the one inverter driving frequency is controlled. There is no unnatural switching step or flickering of light caused by the step when shifting to dimming by controlling the user. Without giving an unnatural impression, it can be turned smoothly discharge lamp 9 to set the dimming degree from outside.

Embodiment 4 FIG.
This embodiment shows a mode in which dimming is started by an appropriate fade-in in an environment where the discharge lamp 9 is placed. FIG. 9 shows a circuit configuration of the discharge lamp lighting device according to the present embodiment. In the circuit configuration shown in FIG. 1 of the first embodiment, a lighting detection circuit 10 is provided on one end side of the discharge lamp 9. It is a configuration.
In FIG. 9, the same or corresponding parts as those in FIG.
Reference numeral 10 denotes a lighting detection circuit that detects that the discharge lamp 9 is discharged and lit. The lighting detection signal 11 detected by the lighting detection circuit 10 is output to the frequency control circuit 4.

The operation of the discharge lamp lighting device configured as described above will be described with reference to FIGS. FIG. 10 is a diagram showing the relationship between the switching operation of the inverter drive frequency f and the lighting detection signal 11 detected by the lighting detection circuit 10 as the time after receiving the lighting command on the horizontal axis.
It is known that when a discharge lamp is started and lit in a low temperature environment such as 0 ° C., a larger starting energy is required than at normal temperature. For example, when lighting is performed at a dimming degree of 10%, the time between T1 and T2 of the first drive frequency f1 and the second drive frequency f2 of the inverter drive frequency as described in the first and second embodiments. The ratio was 1: 9. However, when the discharge lamp 9 is similarly performed in a low-temperature environment of 0 ° C., the drive frequency f1 at which a high voltage (starting voltage) sufficient for starting the discharge lamp 9 is generated has a period T Therefore, there is a possibility that sufficient starting energy cannot be given when starting in a low temperature environment, and there is a possibility that the discharge lamp 9 does not light up and the starting fails.

Therefore, until the lighting detection circuit 10 provided at one end of the discharge lamp 9 detects the lighting of the discharge lamp 9, the ratio of the period T1 driven at the first frequency f1 to the period T of the inverter driving frequency is gradually increased from zero. As a result, the discharge lamp 9 is given sufficient starting energy, and the lamp current IL at that time operates as given by the equation (1) described in the first embodiment. Then, after the lighting of the discharge lamp 9 is detected, for example, frequency control is performed so that the time ratio between T1 and T2 of the first frequency f1 and the second frequency f2 according to the dimming degree command set from the outside is obtained. The circuit 4 is generated by controlling the inverter drive frequency, and the drive circuit 5 operates the inverter circuit based on the drive frequency information.

  As described above, in the present embodiment, the lighting detection circuit 10 that detects the lighting of the discharge lamp 9 is provided, and until the lighting of the discharge lamp 9 is detected by the lighting detection circuit 10, the first for the period T of the inverter driving frequency. By operating so that the ratio of the period T1 driven at the frequency f1 gradually increases from zero, it becomes possible to give the discharge lamp 9 sufficient starting energy, and the discharge lamp 9 is discharged in a low temperature environment. Even in a difficult case, it is possible to reliably turn on the light in a low light flux state in an environment where the discharge lamp 9 is placed.

In the present embodiment, for example, after the T1 time ratio of the first drive frequency f1 with respect to the cycle T is 100% at a predetermined dimming degree of 50%, the first dimming is performed as in the third embodiment. The inverter drive frequency is lowered from the drive frequency f1 and the dimming control is performed by controlling the frequency in accordance with the dimming degree command set from the outside, for example, to the inverter drive frequency fn that is in the all-light lighting state. is there.

Embodiment 5. FIG.
The present embodiment is a discharge lamp lighting device provided with the lighting detection circuit 10 of the fourth embodiment, and shows a mode in which a plurality of discharge lamps are lit.
FIG. 11 shows a circuit configuration diagram of a discharge lamp lighting device when, for example, two discharge lamps are lit in the present embodiment. The ballast choke coil has the circuit configuration shown in FIG. 9 of the fourth embodiment. 7b, a capacitor 8b, a discharge lamp 9b, a lighting detection circuit 10b for detecting the lighting of the discharge lamp 9b, and an AND circuit 12 are added. In FIG. 11, the same or corresponding parts as those in FIG.
In FIG. 11, reference numerals 10a and 10b are disposed on one end side of the discharge lamps 9a and 9b of the load circuit, and are lighting detection circuits for detecting that the discharge lamps 9a and 9b are discharged and turned on. The lighting detection signals 11a and 11b detected at 10b are input to the AND circuit 12 that takes a logical product, and the lighting signal 13 output after processing in the AND circuit 12 is input to the frequency control circuit 4. It has a configuration.

The operation of the discharge lamp lighting device configured as described above will be described with reference to FIGS. FIG. 12 is a diagram showing the state of the switching operation of the inverter drive frequency f and the relationship between the lighting detection signals 11a and 11b and the lighting signal 13 with the horizontal axis as the time after receiving the lighting command.
Lighting of the discharge lamps 9a and 9b is detected by the lighting detection circuits 10a and 10b, respectively, and the AND circuit 12 is supplied with two discharge lamps by inputting the lighting detection signals 11a and 11b from the lighting detection circuits 10a and 10b. Until the lighting signal 13 indicating the lighting of 9a and 9b is output to the frequency control circuit 4, the frequency control circuit 4 switches the first driving frequency f1 and the second driving frequency f2 in the inverter driving frequency, Control is performed such that the ratio of the period T1 driven at the first frequency f1 is gradually increased from zero. Then, after each of the discharge lamps 9a and 9b is turned on and the lighting signal 13 is output from the AND circuit 12 to the frequency control circuit 4, for example, the first frequency f1 according to a dimming degree command set from the outside. Is generated by controlling the inverter drive frequency by the frequency control circuit 4 so that the time ratio between T1 and T2 of the second frequency f2 is obtained, and the drive circuit 5 operates the inverter circuit based on the drive frequency information. In FIG. 12, the discharge lamp 9a is turned on first, and then the discharge lamp 9b is turned on.

  As described above, in the present embodiment, for example, when two discharge lamps 9a and 9b are lit, lighting of the discharge lamps 9a and 9b is detected by the lighting detection circuits 10a and 10b, respectively, and the lighting detection circuits 10a and 10b are detected. Until the AND circuit 12 outputs the lighting signal 13 indicating the lighting of the two discharge lamps 9a and 9b to the frequency control circuit 4 by the input of the lighting detection signals 11a and 11b from the frequency control circuit 4, the frequency control circuit 4 Since the drive frequency f1 and the second drive frequency f2 are switched, the inverter drive frequency is controlled so that the ratio of the period T1 driven at the first frequency f1 to the period T gradually increases from zero. Even when the energy required for starting a discharge lamp is slightly different among multiple discharge lamps due to variations in characteristics, etc. It is possible to, reliably discharge lamp under placed environment of the discharge lamp becomes possible to light up in a low light flux state.

In the present embodiment, for example, after the T1 time ratio of the first drive frequency f1 with respect to the cycle T is 100% at a predetermined dimming degree of 50%, the first dimming is performed as in the third embodiment. The inverter drive frequency is lowered from the drive frequency f1 and the dimming control is performed by controlling the frequency in accordance with the dimming degree command set from the outside, for example, to the inverter drive frequency fn that is in the all-light lighting state. is there.

In the above embodiment, two discharge lamps are described as examples of a plurality of discharge lamps. Similarly, in the case of three or more discharge lamps, the AND circuit 12 similarly turns on each discharge lamp. The ratio of the period T1 driven at the first frequency f1 to the period T is set to zero while the first drive frequency f1 and the second drive frequency f2 are switched until the lighting signal 13 indicating is output to the frequency control circuit 4. After the inverter driving frequency is controlled so as to gradually increase from the first driving frequency f1, the inverter driving frequency is similarly lowered from the first driving frequency f1 after the T1 time ratio of the first frequency f1 reaches 100%. The dimming control is performed by controlling the frequency according to the dimming degree command set from the outside until all the lights are turned on.

It is a circuit block diagram of the discharge lamp lighting device in Embodiment 1 of this invention. It is a figure which shows the relationship between the inverter drive frequency f before discharge which concerns on Embodiment 1 of this invention, and the capacitor | condenser voltage Vc generate | occur | produced at the both ends of a capacitor | condenser. It is a figure which shows the relationship between the inverter drive frequency f which concerns on Embodiment 1 of this invention, and the lamp current IL which flows into a discharge lamp. It is a figure which shows the mode of switching operation | movement of the inverter drive frequency which concerns on Embodiment 1 of this invention. FIG. 5 is a schematic diagram showing a lamp current flowing in the discharge lamp during the inverter drive frequency switching operation shown in FIG. 4. It is a figure showing the mode of switching operation | movement of the inverter drive frequency in Embodiment 2 of this invention. It is an enlarged view of the inverter drive frequency switching operation | movement of the said FIG. It is a schematic diagram which shows the lamp current which flows into the discharge lamp at the time of the inverter drive frequency switching operation | movement of the said FIG. It is a circuit block diagram of the discharge lamp lighting device in Embodiment 4 of this invention. It is a figure showing the mode of the switching operation of the inverter drive frequency which concerns on Embodiment 4 of this invention, and the state of the lighting detection signal. It is a circuit block diagram of the discharge lamp lighting device in Embodiment 5 of this invention. It is the figure showing the mode of switching operation of the inverter drive frequency concerning Embodiment 5 of this invention, and the state of a lighting detection signal and a lighting signal.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 DC power source, 2, 3 Switching element, 4 Frequency control circuit, 5 Drive circuit, 6 Load circuit, 7, 7a, 7b Ballast choke coil, 8, 8a, 8b Capacitor, 9, 9a, 9b Discharge lamp, 10, 10a 10b lighting detection circuit 11, 11a, 11b lighting detection signal, 12 AND circuit, 13 lighting signal.

Claims (3)

A DC power supply, an inverter circuit that converts the DC power supply voltage into a high-frequency voltage by a switching operation of the switching element to light a discharge lamp at a high frequency, a frequency control circuit that outputs a driving frequency of the switching element, and the frequency control circuit A drive circuit for driving the switching element based on the output frequency,
Wherein the frequency control circuit, when starting the discharge lamp, within a predetermined period, a period for outputting a first drive frequency causes generate sufficient high frequency voltage to light the discharge lamp in the zero, first A second driving frequency higher than the first driving frequency is output, and thereafter, every time a predetermined period elapses, a period during which the second driving frequency is output is gradually shortened, and the first driving frequency is output. A discharge lamp lighting device characterized by performing control to gradually increase a period . 2. The frequency control circuit according to claim 1, wherein the first drive frequency is controlled so as to be gradually lowered when the output period of the first drive frequency reaches the entire period of a predetermined period. The discharge lamp lighting device described. Equipped with a lighting detection circuit that detects the lighting of the discharge lamp,
3. The discharge lamp according to claim 1 , wherein the frequency control circuit gradually increases a period during which the first drive frequency is output until the lighting detection circuit detects lighting of the discharge lamp. 4. Lighting device.

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