JP2009199876A - Discharge lamp lighting device, and illumination fixture equipped with this discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent lighting failure of a discharge lamp 7 when switching from an all-light lighting state to a dimming lighting state. <P>SOLUTION: Since this is equipped with: a direct current power supply circuit 12 to boost and smoothen a voltage in which a commercial power supply AC is rectified; an inverter circuit 14 to convert a direct current voltage supplied from the direct current power supply circuit 12 into a high frequency current; a load circuit 13 which is connected to the inverter circuit 14, and comprises a series circuit of a choke coil T2, a capacitor C5 for start-up which is connected in parallel via a filament of the discharge lamp 7 subjected to lighting, and a coupling capacitor C6; and a control circuit 16 which controls an oscillation frequency of the inverter circuit 14, controls a set value of a boosted voltage value boosted by the direct current power supply circuit 12, and when the discharge lamp 7 is switched to dimming lighting, changes the boosted voltage value to a voltage value at the time of dimming lighting after changing the oscillation frequency of the inverter circuit 14, the lighting failure of the discharge lamp 7 when switching from the all-light lighting state to the dimming lighting state can be prevented. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technique for controlling a discharge lamp lighting device when changing the brightness of a discharge lamp.

  In a discharge lamp lighting device for lighting a general fluorescent lamp, as a method for dimming the lamp, an oscillation frequency of a switching circuit is increased, and an LCR of a load circuit composed of an inductance, a resonance capacitor, a coupling capacitor, and a lamp equivalent resistance There is a technique for dimming by reducing the lamp current by weakening the resonance of the series resonant circuit (see, for example, Patent Document 1).

  Further, as a method of dimming the lamp, there is a technique of dimming by reducing the voltage value of the DC voltage supplied to the inverter circuit (see, for example, Patent Document 2).

Japanese Patent Laid-Open No. 11-238589 (paragraph “0047”, FIG. 15) Japanese Patent Laid-Open No. 5-25889 (paragraph “0006”, FIG. 2)

  However, many discharge lamps such as high-frequency lamps (for example, FHF type, FHC type, FHD type, and FHT type discharge lamps defined in JIS C 7601: 2004) are designed to have a high rated lamp voltage. When the discharge lamp is dimmed, the lamp voltage (re-ignition voltage) increases rapidly as the dimming degree increases at the time of dimming transition, and the discharge lamp may be extinguished.

  An object of the present invention is, for example, to prevent a discharge lamp from turning off when switching from an all-light lighting state to a dimming lighting state.

  A discharge lamp lighting device according to the present invention includes a DC power supply circuit that rectifies an input commercial power supply, boosts and smoothes the rectified voltage, and a switching element, and is supplied from the DC power supply circuit. A load comprising a series circuit of an inverter circuit for converting a high frequency current, a choke coil, a starting capacitor connected in parallel via a filament of a discharge lamp used for lighting, and a coupling capacitor connected to the inverter circuit The oscillation frequency of the inverter circuit is changed when the discharge lamp is switched to dimming lighting by controlling the oscillation frequency of the circuit and the inverter circuit and controlling the set value of the boost voltage value boosted by the DC power supply circuit And a control circuit that changes the boosted voltage value to a voltage value at the time of dimming lighting.

  According to the present invention, when switching the discharge lamp to dimming lighting, the boosted voltage value is changed to the voltage value at the time of dimming lighting after changing the oscillation frequency of the inverter circuit. It is possible to prevent the discharge lamp from extinguishing when switching from one to the dimming lighting state.

Embodiment 1 FIG.
FIG. 1 is a perspective view showing the lighting fixture of the present embodiment, and FIG. 2 is an exploded perspective view of the lighting fixture of FIG.

  The luminaire 1 includes a luminaire body 2 and a shade 3, and the discharge lamp lighting device 4, the lamp holder 6 to which the discharge lamp 5 is detachably attached, the discharge lamp lighting device 4 and the discharge lamp lighting device 4. A lamp socket 7 electrically connected to the electric lamp 5 is provided.

Next, a discharge lamp lighting device built in the lighting fixture 1 will be described.
FIG. 3 is a circuit block diagram showing a discharge lamp lighting device built in the lighting fixture shown in FIG.

  The discharge lamp lighting device 4 includes a rectifier circuit 11 that rectifies an AC voltage to which a commercial power supply AC is input, a boost chopper circuit 12 that boosts a voltage output from the rectifier circuit 11, and a voltage output from the boost chopper circuit 12 at a high frequency. An inverter circuit 14 that converts the current into electric power to be supplied to the discharge lamp 5 connected via the load circuit 13, a drive circuit 15 that controls oscillation of the inverter circuit 14, and an oscillation frequency of the inverter circuit 14 in the drive circuit 15 A control circuit 16 for outputting a switching control signal for switching the output voltage of the step-up chopper circuit 12 and a dimming signal for switching the brightness of the discharge lamp 5 to be lit. A dimming signal output unit 17 for outputting to the control circuit 16 is provided.

  The step-up chopper circuit 12 includes a pulsating voltage detector 18 connected in parallel to the output terminal of the rectifier circuit 11, a switching circuit 19 connected via the transformer T1, and a diode D1 connected between the transformer T1 and the anode side. A capacitor C1 connected to the cathode side of the diode D1 and the low potential side of the rectifier circuit 11, an output voltage detection unit 20 connected in parallel to the capacitor C1 to detect the voltage charged in the capacitor C1, and a pulsating voltage A detection signal detected by the detection unit 18, the output voltage detection unit 20 and the switching circuit 19 and a detection voltage generated on the secondary side of the transformer T1 are input via the resistor R14, and based on the input detection signal and detection voltage. And a step-up chopper control circuit 21 for controlling the switching circuit 19.

  The pulsating voltage detection unit 18 includes resistors R1 to R3 connected in series.

  The switching circuit 19 includes a MOS-FET Q1 serving as a switching element, a resistor R4 connected to the gate terminal of the MOS-FET Q1, and a resistor R5 connected to the source terminal of the MOS-FET Q1. The MOS-FET Q1 is turned on / off according to the control signal output from the circuit 21.

  The output voltage detection unit 20 includes feedback resistors 21 to R23 connected in series, and a setting change unit 22 connected in parallel to the feedback resistor R23.

  The setting changing unit 22 includes a resistor R24, a transistor Q7 having a collector terminal connected to one end of the resistor R24, and a capacitor C4 connected in parallel to the collector terminal-emitter terminal of the transistor Q7.

  The load circuit 13 includes an inductor T2 connected to the inverter circuit 14, a starting capacitor C5 connected via one filament of the discharge lamp 5 used for lighting, and a coupling connected via the other filament. A capacitor C6 is provided.

  The inverter circuit 14 includes MOS-FETs Q2 and Q3 which are switching elements connected in series. The inverter circuit 14 is connected to the step-up chopper circuit 12, and a load circuit 13 is connected in parallel between the drain terminal and the source terminal of the MOS-FET Q3. Connected.

  The drive circuit 15 includes a transistor Q4 to which the oscillation control signal output from the control circuit 16 is input to the base terminal via the resistor R6, a resistor R7 connected to the control power supply Vcc and the collector terminal of the transistor Q4, and a transistor Q4 Transistor Q5 and transistor Q6 connected to their respective base terminals via a resistor R8, and an emitter terminal of transistor Q5 and a collector terminal of transistor Q6 are connected to a collector terminal of the transistor Q5, and a transformer connected via a resistor R9. CT1 and a capacitor C3 connected between the other terminal of the transformer CT1 and the ground terminal are provided.

  The same signal output from the transistor Q4 is input to the base terminals of the transistor Q5 and the transistor Q6, but the transistor Q5 is an NPN type and the transistor Q6 is a PNP type so that the transistor Q5 and the transistor Q6 are not simultaneously turned on. Yes.

  The transformer CT1 of the drive circuit 15 has two secondary windings CT1-1 and CT1-2, and is connected to the gate terminals of MOS-FETs Q2 and Q3 of the inverter circuit via resistors R10 and R11, respectively.

  Resistors R12 and R13 are connected in parallel between the gate terminals and source terminals of the respective MOS-FETs Q2 and Q3.

  The control circuit 16 includes a microcomputer IC1 and outputs an oscillation control signal corresponding to the oscillation frequency of the inverter circuit 14 to turn on / off the transistor Q4, and a switching control signal for changing the output voltage of the boost chopper circuit 12. The output of the transistor Q7 is controlled on / off.

  The dimming signal output unit 17 includes a switch element SW and a diode D2 connected in series, is connected between the rectifier circuit 11 and the control circuit 16, and outputs a dimming signal to the microcomputer IC1 of the control circuit 16.

  Next, the operation of the discharge lamp lighting device 4 will be described.

  When electric power from the commercial power supply AC is supplied to the discharge lamp lighting device 4, the boost chopper circuit 12 operates and the boosted voltage is applied to the inverter circuit 14.

  The microcomputer IC1 turns off the transistor Q7 of the output voltage detection circuit 19 and inputs an oscillation control signal composed of a PWM signal to the transistor Q4 of the drive circuit 15.

  The transistor Q4 is turned on / off according to the input oscillation control signal, and the transistors Q5 and Q6 are alternately turned on / off. Note that the transistors Q5 and Q6 have different polarities and are not turned ON at the same time. The transistor Q5 and the transistor Q6 are alternately turned on / off, whereby the primary side of the transformer CT1 is charged / discharged. At this time, the primary side of the transformer CT1 and the capacitor C3 resonate, and an alternating voltage is generated on the secondary sides CT-1 and CT-2 of the transformer CT1.

  The AC voltage generated on the secondary side CT-1 and CT-2 of the transformer CT1 is input to the gate terminals of the MOS-FETs Q2 and Q3 of the inverter circuit 14, and the MOS-FETs Q2 and Q3 are alternately turned on and off. The DC voltage output from the step-up chopper circuit 12 is converted into a high-frequency AC current and supplied to the discharge lamp via the load circuit 13.

  Next, characteristics of the boost chopper circuit 12, the load circuit 13, and the inverter circuit 14 will be described.

  4 is a diagram showing resonance characteristics of the inductor T2, the starting capacitor C5, and the discharge lamp 5 of the load circuit 13. As shown in FIG.

  Until the discharge lamp 5 is turned on, the impedance of the discharge lamp 5 becomes very large, so that the resonance state is substantially caused by the inductor T2 and the starting capacitor C5, and the resonance characteristic A shown in FIG.

  When the discharge lamp 5 is turned on, the impedance of the discharge lamp 5 is lowered, and therefore, a resonance state is established by the inductor T2 and the impedance synthesized by connecting the discharge lamp 5 and the starting capacitor C5 in parallel, and the resonance frequency f0 ′ is obtained. The resonance characteristics B and the resonance characteristics C shown in FIG.

  The resonance frequency f0 ′ shown in the resonance characteristics B and the resonance characteristics C is substantially equal, and when the voltage output from the boost chopper circuit 12 is high, Q increases as shown in the resonance characteristics B, and the voltage output from the boost chopper circuit 12 is When low, the resonance characteristic C has a characteristic that Q is small.

  The preheating frequency fp is the oscillation frequency of the inverter circuit 14 when the filament of the discharge lamp 5 is preheated, the starting frequency fs is the oscillation frequency of the inverter circuit 14 for starting (lighting) the discharge lamp 5 and the all-light lighting frequency. f is the oscillation frequency of the inverter circuit 14 for lighting the discharge lamp 5 in all light, the dimming lighting frequency fd is the oscillation frequency of the inverter circuit 14 for dimming and lighting the discharge lamp 5, and the resonance frequency f0 is the discharge frequency. The resonance frequency before the lamp 5 is lit, the resonance frequency f0 ′ is the resonance frequency when the discharge lamp 5 is lit, and the relationship between these frequencies is preheating frequency fp> starting frequency fs ≧ all-light lighting frequency. f> resonance frequency f0 before lighting> resonance frequency f0 ′ during lighting.

  Next, the operation until the discharge lamp 5 is turned on will be described.

  The oscillation control signal (oscillation frequency) output from the microcomputer IC1 becomes the preheating frequency fp when the commercial power source AC is turned on, the load current indicated by the point a of the resonance characteristic A flows, and the filament of the discharge lamp 5 is preheated.

  After preheating the filament of the discharge lamp 5, the oscillation control signal output from the microcomputer IC1 is switched, the oscillation frequency of the inverter circuit 14 becomes the starting frequency fs, the load current indicated by the point b of the resonance characteristic A flows, and the discharge lamp A discharge start voltage is applied to both ends of 5 and discharge (lighting) of the discharge lamp 5 is started.

  When the discharge lamp 5 is lit, the oscillation control signal output from the microcomputer IC1 is switched, the oscillation frequency of the inverter circuit 14 is changed to the all-light lighting frequency f, and the load current indicated by the point c of the resonance characteristic B flows.

  In this way, the discharge lamp 5 is lit by changing the oscillation frequency of the inverter circuit 14 and the lighting frequency f is maintained. The brightness of the discharge lamp 5 when the lamp is lit at this lighting frequency f is turned on in all light. (Lighting at 100% light output).

  When the polarity of the AC load current supplied to the discharge lamp 5 is switched after the discharge lamp 5 starts discharging (lights on), the re-ignition voltage is continuously applied, so that the lighting is maintained. This re-ignition voltage is lower than the discharge start voltage generated when the oscillation frequency of the inverter circuit 14 is the start frequency fs, but the current is reversed when the polarity of the load current applied to the discharge lamp 5 is switched. When the voltage applied to the discharge lamp 5 is lower than the re-ignition voltage, the discharge stops (extinguishes).

  Next, the case where the brightness of the discharge lamp 5 is switched from all-light lighting to dimming lighting (for example, lighting at 71% light output) will be described.

  FIG. 5 is a diagram showing the oscillation state of the inverter circuit when the discharge lamp is lit, the lamp current, the lamp voltage, and the output voltage of the boost chopper circuit. FIG. 5A shows the oscillation control output by the microcomputer. FIG. 5 (b) is a diagram showing a signal, FIG. 5 (b) is a diagram showing a lamp current flowing through the discharge lamp, FIG. 5 (c) is a diagram showing a lamp voltage applied to both ends of the discharge lamp, and FIG. It is a figure which shows the output voltage which a step-up chopper circuit outputs.

  The microcomputer IC1 outputs an oscillation control signal, switches the transistor Q4, and lights up all the light (time t0 to time t1).

  During time t0 to time t1, the boost chopper circuit 12 outputs a DC voltage of 400V. For example, when an FHC34 type discharge lamp is used, the lamp current is 380 mA (effective value) and the lamp voltage is 125 V (effective value). It is supplied from the inverter circuit 14 to the discharge lamp 5.

  Next, when the switch SW of the dimming signal output unit 17 is operated, the commercial power supply AC is input, and the dimming signal half-wave rectified by the diode D2 is input to the microcomputer IC1.

  When a dimming signal is input to the microcomputer IC1, internal processing time of the microcomputer IC1 is generated in order to switch the oscillation frequency of the inverter circuit 14 (time t1 to t2).

  While the microcomputer IC1 is performing internal processing, the oscillation control signal output from the microcomputer IC1 is stopped in the Hi or Lo state, and the oscillation of the inverter circuit 14 is stopped.

  Here, a lamp current waveform and a lamp voltage waveform appear during the period from the time t1 to the time t2, and this is due to resonance due to residual charges charged in the inductor T2, the coupling capacitor C6, and the starting capacitor C5.

  For example, when the microcomputer IC1 has a low operating frequency, the period during which the output of the oscillation control signal for controlling the oscillation frequency is stopped when the oscillation frequency of the inverter circuit 14 is switched becomes long.

  Since the period of the stop is prolonged, that is, the oscillation of the inverter circuit 14 is stopped and the power supply to the discharge lamp 5 is interrupted for a long time, it is difficult to maintain the re-ignition voltage when shifting to dimming lighting. Thus, the discharge lamp 5 is easily turned off.

  The internal processing time varies depending on the characteristics of the microcomputer IC1, but the operating frequency of the microcomputer IC1 generally used in the discharge lamp lighting device 4 is about 40 kHz to 100 kHz. The internal processing time required for this case (oscillation control) Signal stop time) is about several μs to several hundred μs.

  Therefore, when shifting to dimming lighting, the oscillation control signal for controlling the oscillation frequency is stopped, but the oscillation control signal with the oscillation frequency when the output of the oscillation control signal is started as the starting frequency fs is output, A state in which Q due to resonance between the inductor T2 and the starting capacitor C5 is large (“point d” shown in FIG. 4) is set (time t2 to time t3).

  As described above, since the Q due to the resonance between the inductor T2 and the starting capacitor C5 becomes large, a voltage higher than the re-ignition voltage is applied to both ends of the discharge lamp 5, and the lighting of the discharge lamp 5 is continued.

  Even if the discharge lamp 5 is extinguished due to a voltage lower than the re-ignition voltage, since the oscillation frequency of the inverter circuit 14 is the starting frequency fs, the resonance characteristics of the load circuit 13 are 4, the load current indicated by “point b” in FIG. 4 flows in the load circuit 13, so that the discharge lamp 5 can be started again (lighted).

  However, since the starting frequency fs is close to the all-light lighting frequency f, the dimming rate of the discharge lamp 5 cannot be set to the intended dimming rate when the oscillation frequency of the inverter circuit 14 is the starting frequency.

  Next, the transistor Q7 of the setting changer 22 of the boost chopper circuit 12 is turned on, the voltage dividing ratio of the feedback resistors R21 to R23 is increased, the oscillation frequency of the boost chopper control circuit 21 is changed, and the output of the boost chopper circuit 12 is output. The voltage is reduced from 400 V to 300 V (voltage corresponding to the dimming rate) (after time t3).

  Therefore, since the voltage input to the inverter circuit 14 decreases, the Q of resonance of the load circuit 13 becomes small (Q value becomes low).

  The lamp voltage applied to the discharge lamp 5 is determined depending on the lighting state of the discharge lamp 5 (for example, the lamp current flowing through the discharge lamp 5 and the oscillation frequency of the inverter circuit 14). When lit, the lamp voltage is 125 V (effective value), and when lit at a dimming rate of 71%, the lamp voltage is 157 V (effective value).

  Therefore, the output voltage of the step-up chopper circuit 12 is lowered, the Q value of the load circuit 13 is lowered, and the lamp voltage is further raised, so that the lamp current flowing through the discharge lamp 5 is lowered.

  In this way, by controlling the output voltage of the boost chopper circuit 12, the dimming rate of the discharge lamp 5 is controlled to be the intended dimming rate.

  Here, based on the resonance characteristics of FIG. 4, the operation flow of preheating → starting → all-light lighting → dimming lighting is arranged. The resonance state “point a” at the preheating frequency fd → resonance state “at the starting frequency fs” Resonance state "point c" at all light lighting frequencies f → resonance state "point e" after transition to resonance state "point d" or "point b" at dimming lighting frequency fd Become.

  In this way, when switching from all-light lighting to dimming lighting, since the Q due to resonance between the inductor T2 and the starting capacitor C5 is shifted to a large state, the discharge lamps 5 are required to continue lighting at both ends of the discharge lamp 5. Therefore, it is possible to prevent the discharge lamp 5 from being extinguished by applying a re-ignition voltage.

  Further, since the output voltage of the step-up chopper circuit 12 can be adjusted after shifting to a state where the Q due to resonance between the inductor T2 and the starting capacitor C5 is large, the discharge lamp 5 is turned on when the dimming rate is switched. It can be prevented from disappearing and can be easily changed to an arbitrary dimming rate.

  In this embodiment, the case where the dimming lighting frequency fd at the time of dimming lighting is set to the starting frequency fs has been described. However, the re-ignition voltage of the discharge lamp 5 is applied when the dimming lighting frequency fd is transitioned to. Therefore, when the relationship between the preheating frequency fp, the starting frequency fs, the all-light lighting frequency f, and the resonance frequencies f0 and f0 ′ is fp> fs ≧ f> f0> f0 ′, the dimming lighting frequency fd May be controlled so as to maintain the relationship of f0 <fd ≦ fs.

  In the present embodiment, the transistor Q7 of the setting changer 22 of the boosting chopper circuit 12 is turned on to increase the voltage dividing ratio of the feedback resistors R21 to R23, and the oscillation frequency of the boosting chopper control circuit 21 is changed to increase the boosting chopper circuit. Although the output voltage of 12 is lowered, the control circuit 16 directly outputs a signal for lowering the boost voltage value to the boost chopper control circuit 21 to change the boost set value in the boost chopper control circuit 21 to increase the boost chopper. The output voltage of the circuit 12 may be lowered.

  In the present embodiment, the case where the discharge lamp 5 is switched from the all-light lighting state to the dimming lighting state has been described. However, when the discharge lamp 5 is switched from the dimming lighting state to the all-light lighting state, the dimming lighting is performed. Since the resonance state at the time of all light lighting becomes a resonance state having a larger Q than the resonance state of the above, the output voltage of the boost chopper circuit 12 is increased while maintaining the starting frequency fs, and then the all light lighting frequency f. It is obvious that the output voltage of the step-up chopper circuit 12 may be increased and the transition to the all-light lighting frequency f may be made.

  Further, in the present embodiment, the dimming control using the two-step dimming signal by the on / off operation of the switch SW has been described, but the dimming control using the three-step or more dimming signal may be used.

Embodiment 2. FIG.
The present embodiment is the same as the circuit configuration of the discharge lamp lighting device shown in the first embodiment, and shows another operation of the control circuit.

  In the present embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  The characteristics of the boost chopper circuit 12, the load circuit 13, and the inverter circuit 14 will be described.

  FIG. 6 is a diagram illustrating resonance characteristics of the inductor, the starting capacitor, and the discharge lamp of the load circuit.

  Until the discharge lamp 5 is lit, the impedance of the discharge lamp 5 becomes very large, so that the resonance state is substantially caused by the inductor T2 and the starting capacitor C5, and the resonance characteristic A shown in FIG.

  When the discharge lamp 5 is turned on, the impedance of the discharge lamp 5 is lowered, and therefore, a resonance state is established by the inductor T2 and the impedance synthesized by connecting the discharge lamp 5 and the starting capacitor C5 in parallel, and the resonance frequency f0 ′ is obtained. The resonance characteristics B and the resonance characteristics C shown in FIG.

  When the resonance frequency f0 ′ shown in the resonance characteristics B and the resonance characteristics C is substantially equal, and the voltage output from the boost chopper circuit 12 is high, the load current increases as shown in the resonance characteristics B, and the voltage output from the boost chopper circuit 12 Is low, the load current is reduced as shown in the resonance characteristic C.

  The relationship between the frequencies is preheating frequency fp> starting frequency fs ≧ all light lighting frequency f> resonance frequency f0 before lighting> resonance frequency f0 ′ during lighting.

  Next, the operation until the discharge lamp 5 is turned on will be described.

  The oscillation control signal (oscillation frequency) output from the microcomputer IC1 becomes the preheating frequency fp when the commercial power source AC is turned on, the load current indicated by the point a of the resonance characteristic A flows, and the filament of the discharge lamp 5 is preheated.

  After preheating the filament of the discharge lamp 5, the oscillation control signal (oscillation frequency) output from the microcomputer IC 1 becomes the starting frequency fs, the load current indicated by the point b of the resonance characteristic A flows, and discharge occurs at both ends of the discharge lamp 5. A start voltage is applied, and discharge (lighting) of the discharge lamp 5 is started.

  When the discharge lamp 5 is lit, the oscillation control signal (oscillation frequency) output from the microcomputer IC1 transitions to the lighting frequency f, and the load current indicated by the point c of the resonance characteristic B flows.

  In this way, the discharge lamp 5 is lit by changing the oscillation frequency of the inverter circuit 14 and the lighting frequency f is maintained. The brightness of the discharge lamp 5 when the lamp is lit at this lighting frequency f is turned on in all light. (Lighting at 100% light output).

  A case where the brightness of the discharge lamp 5 is switched from all-light lighting to dimming lighting (for example, lighting at 71% light output) will be described.

  FIG. 7 is a diagram showing the oscillation state of the inverter circuit when the discharge lamp is lit, the lamp current, the lamp voltage, and the output voltage of the boost chopper circuit. FIG. 7A shows the oscillation control output by the microcomputer. FIG. 7 (b) is a diagram showing a signal, FIG. 7 (b) is a diagram showing a lamp current flowing through the discharge lamp, FIG. 7 (c) is a diagram showing a lamp voltage applied to both ends of the discharge lamp, and FIG. It is a figure which shows the boost voltage which a boost chopper circuit outputs.

  The microcomputer IC1 outputs an oscillation control signal, switches the transistor Q4, and lights up all the light (time t0 to time t1).

  For example, when an FHC34 type discharge lamp is used from time t0 to time t1, power of a lamp current of 380 mA (effective value) and a lamp voltage of 125 V (effective value) is supplied from the inverter circuit 14 to the boost chopper circuit 12. Outputs a DC voltage of 400V.

  Next, when the switch SW of the dimming signal output unit 17 is operated, the commercial power supply AC is input, and the dimming signal half-wave rectified by the diode D2 is input to the microcomputer IC1.

  When a dimming signal is input to the microcomputer IC1, internal processing time of the microcomputer IC1 is generated in order to switch the oscillation frequency of the inverter circuit 14 (time t1 to t2).

  While the microcomputer IC1 is performing internal processing, the oscillation control signal output from the microcomputer IC1 is stopped in the Hi or Lo state, and the oscillation of the inverter circuit 14 is stopped.

  Here, a lamp current waveform and a lamp voltage waveform appear during the period from the time t1 to the time t2, and this is due to resonance due to residual charges charged in the inductor T2, the coupling capacitor C6, and the starting capacitor C5.

  When shifting to dimming lighting, the oscillation control signal for controlling the oscillation frequency is stopped, but an oscillation control signal with the oscillation frequency when the oscillation control signal output is started as the starting frequency fs is output, and the inductor T2 And the resonance capacitor Q5 has a large resonance Q ("point d" shown in FIG. 7) (time t2 to time t3 ').

  Since the Q due to the resonance between the inductor T2 and the starting capacitor C5 increases in this way, a voltage higher than the re-ignition voltage is applied to both ends of the discharge lamp 5, and the lighting of the discharge lamp 5 is continued.

  Even if the discharge lamp 5 is extinguished due to a voltage lower than the re-ignition voltage, since the oscillation frequency of the inverter circuit 14 is the starting frequency fs, the resonance characteristics of the load circuit 13 are 7, the load current indicated by “point b” in FIG. 6 flows in the load circuit 13, so that the discharge lamp 5 can be started again (lighted).

  However, since the starting frequency fs is close to the all-light lighting frequency f, the dimming rate of the discharge lamp 5 cannot be set to the intended dimming rate when the oscillation frequency of the inverter circuit 14 is the starting frequency fs.

  Next, the transistor Q7 of the setting changer 22 of the boost chopper circuit 12 is gradually turned on over, for example, about 3 seconds to increase the voltage dividing ratio of the feedback resistors R21 to R23, and the oscillation frequency of the boost chopper control circuit 21 And the DC boost voltage is gradually decreased from 400V to 300V (voltage corresponding to the dimming rate) (time t3 ′ to time t4).

  At this time, since the output voltage of the step-up chopper circuit 12 gradually decreases, the resonance Q value of the load circuit 13 gradually decreases (from “point d” to “point e” in FIG. 7).

  The lamp voltage applied to the discharge lamp 5 is determined depending on the lighting state of the discharge lamp 5 (for example, the lamp current flowing through the discharge lamp 5 and the oscillation frequency of the inverter circuit 14). When lit, the lamp voltage is 125 V (effective value), and when lit at a dimming rate of 71%, the lamp voltage is 157 V (effective value).

  Therefore, the output voltage of the step-up chopper circuit 12 is gradually decreased, the Q value of the load circuit 13 is decreased, and the lamp voltage is further increased. Therefore, the lamp current flowing through the discharge lamp 5 is gradually decreased.

  In this way, the output voltage of the step-up chopper circuit 12 is controlled so as to gradually decrease to the intended dimming rate of the discharge lamp 5, and this output voltage is maintained (after time t4).

  Here, based on the resonance characteristics of FIG. 7, the operation flow of preheating → starting → all-light lighting → dimming lighting is arranged. The resonance state “point a” at the preheating frequency fd → resonance state “at the starting frequency fs” Resonance state "point c" at all light lighting frequencies f → resonance state "point e" after transition to resonance state "point d" or "point b" at dimming lighting frequency fd Become.

  Thus, since the resonance Q by the inductor T2 and the starting capacitor C5 is shifted to a large state, the re-ignition voltage necessary for continuing the lighting of the discharge lamp 5 is applied to both ends of the discharge lamp 5, and the discharge lamp 5 Can be prevented from disappearing.

  Therefore, flickering of the discharge lamp 5 that occurs during the dimming transition can be suppressed.

  Further, since the output voltage of the step-up chopper circuit 12 is gradually reduced, the brightness of the discharge lamp 5 does not change suddenly, and a gradual change in light output can be produced.

  By gradually changing (decreasing) the DC voltage in this way, the voltage input to the inverter circuit 14 does not change steeply, so that the resonance Q by the inductor T2 and the starting capacitor C5 does not change steeply. .

  Therefore, it is possible to suppress a vibration phenomenon that occurs due to abrupt changes in the voltage applied to the inductor T2 and the starting capacitor C5. In particular, the output power of the inverter circuit 14 is detected and the actual output power of the inverter circuit 14 is determined. Thus, feedback control for adjusting the output voltage of the boost chopper circuit 12 is facilitated.

Embodiment 3 FIG.
The present embodiment shows another configuration of the lighting device shown in Embodiments 1 and 2.

  In the present embodiment, the same parts as those in the first embodiment and the second embodiment are denoted by the same reference numerals, and the description thereof is omitted.

FIG. 8 is a diagram illustrating a circuit configuration of the discharge lamp lighting device according to the present embodiment.
In the discharge lamp lighting device 1, two discharge lamps 5 a and 5 b connected in series are connected to a load circuit 13.

  A starting capacitor C5 is connected in parallel to the two discharge lamps 5a and 5b connected in series.

  A secondary winding T2b of the inductor T2a and a preheating capacitor C7 are connected to the filament where the two discharge lamps 5a and 5b are connected to each other. The resonance of the secondary winding T2b and the preheating capacitor C7 results in resonance. The filament is preheated to maintain a temperature at which it can be easily discharged.

  Since the operation of the control circuit for switching from all-light lighting to dimming lighting is the same as that in the first or second embodiment, the description thereof is omitted.

  When the discharge lamps 5a and 5b are connected in series as described above, the output voltage of the inverter circuit 14 corresponding to the number of the discharge lamps 5a and 5b connected in series is required, but the dimming lighting frequency fd at the time of dimming lighting is set as the starting frequency. Since fs is set, the Q value due to the resonance of the inductor T2a and the capacitor C5 can be increased, and the discharge lamps 5a and 5b can be prevented from disappearing.

  In the present embodiment, the case where two discharge lamps 5a and 5b are connected in series has been described, but three or more discharge lamps may be connected in series.

Embodiment 4 FIG.
This embodiment shows another configuration of the lighting circuit shown in Embodiments 1 to 3.

  In the present embodiment, the same parts as those in the first to third embodiments are denoted by the same reference numerals, and description thereof is omitted.

  FIG. 9 is a circuit diagram of the discharge lamp lighting device showing the present embodiment.

  The drive circuit 15 includes a high voltage integrated circuit 23 (hereinafter referred to as HVIC 23), and performs ON / OFF control of the MOS-FETs Q2 and Q3 of the inverter circuit 14.

  The HVIC 23 receives a control signal from the microcomputer and causes the inverter circuit 14 to oscillate at an oscillation frequency corresponding to the input control signal.

  The HVIC 23 does not stop the oscillation of the inverter circuit 14 when the oscillation frequency of the inverter circuit 14 is switched as in the microcomputer, but shifts to the dimming frequency fd as the dimming rate of the discharge lamp 5 increases. Since the lamp current that flows in the discharge lamp 5 instantaneously decreases rapidly, it tends to be difficult to maintain the discharge. In particular, the lower the ambient temperature (environment temperature) where the discharge lamp 5 is placed, the more difficult it is to maintain the discharge. Become.

  However, since the shift to the starting frequency fs when the dimming is turned on and the resonance Q of the load circuit 13 is set to a large state, the output voltage of the boost chopper circuit 12 is lowered. Can continue to apply a voltage higher than the re-ignition voltage.

  Therefore, even when the discharge lamp 5 is placed in an environment where the ambient temperature is low, it can be made difficult to disappear.

  In this embodiment, the case where the HVIC 23 is used has been described. However, the present invention is not limited to the HVIC 23, and a gate drive circuit that causes the inverter circuit 14 to oscillate with a current fed back from the output of the inverter circuit 14 using a transformer or the like. Also good.

  As described above, when shifting from all-light lighting to dimming lighting, the output voltage of the step-up chopper circuit 12 is lowered after the dimming frequency fd is shifted to the starting frequency fs. Even if it is going to go out, a voltage necessary for starting the discharge lamp 5 is applied, and the discharge lamp 5 is kept on.

FIG. 3 is a perspective view showing the lighting apparatus in the first embodiment. 3 is an exploded perspective view showing the lighting apparatus in Embodiment 1. FIG. It is a figure which shows the circuit structure of the discharge lamp lighting device in Embodiment 1. FIG. FIG. 4 is a diagram illustrating resonance characteristics of a load circuit in the first embodiment. 3 is a time chart showing an output of a load circuit in the first embodiment. 6 is a diagram illustrating resonance characteristics of a load circuit according to Embodiment 2. FIG. 6 is a time chart showing an output of a load circuit in the second embodiment. It is a figure which shows the circuit structure of the discharge lamp lighting device in Embodiment 3. FIG. It is a figure which shows the circuit structure of the discharge lamp lighting device in Embodiment 4. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lighting fixture, 2 Lighting fixture main body, 3 Cade, 4 discharge lamp lighting device, 5, 5a, 5b discharge lamp, 6 lamp holder, 7 lamp socket, 11 rectifier circuit, 12 boost chopper circuit, 13 load circuit, 14 inverter circuit , 15 drive circuit, 16 control circuit, 17 dimming signal output unit, 18 pulsating voltage detection unit, 19 output voltage detection unit, 20 switching circuit, 21 step-up chopper control circuit, 22 setting change unit, R1 to R14, R21 to R23 feedback resistor, R24 resistor, C1-C4 capacitor, C5 starting capacitor, C6 coupling capacitor, C
.7 Preheating capacitor, D1, D2 diode, T1, CT1 transformer, T2, T2a inductor, IC1 microcomputer, SW switch, Q1-Q3 MOS-FET, Q4-Q7 transistor.

Claims (6)

A DC power supply circuit that rectifies the commercial power input and boosts and smoothes the rectified voltage;
An inverter circuit having a switching element and converting a DC voltage supplied from the DC power supply circuit into a high-frequency current;
Connected to the inverter circuit, a choke coil, a starting capacitor connected in parallel via a filament of a discharge lamp used for lighting, and a load circuit comprising a series circuit of a coupling capacitor;
While controlling the oscillation frequency of the inverter circuit and controlling the set value of the boosted voltage value boosted by the DC power supply circuit, when switching the discharge lamp to dimming lighting, after changing the oscillation frequency of the inverter circuit A control circuit for changing the boost voltage value to a voltage value at the time of dimming lighting;
A discharge lamp lighting device comprising: The oscillation frequency changed by the control circuit is
The starting frequency when starting the discharge of the discharge lamp is fs, the all-light lighting frequency at the time of all-light lighting is f, the dimming lighting frequency at the time of dimming lighting is fd, and the resonance frequency of the inductor and the starting capacitor is f0, 2. The discharge lamp lighting device according to claim 1, wherein the dimming lighting frequency fd satisfies f0 <fd ≦ fs when the start frequency fs ≧ the total light lighting frequency f is satisfied. The oscillation frequency changed by the control circuit is
The discharge lamp lighting device according to claim 1 or 2, wherein a starting frequency when starting discharge of the discharge lamp and a dimming lighting frequency during dimming lighting are made substantially equal.   4. The control circuit according to claim 1, wherein when the boosted voltage value is changed, the control circuit gradually decreases the set value of the boosted voltage value until the voltage value at the time of dimming lighting is reached. The discharge lamp lighting device according to 1. The control circuit comprises a microcomputer,
5. The discharge lamp lighting device according to claim 1, wherein the inverter circuit controls ON / OFF of the switching element in response to a pulse signal output from the microcomputer. 6. The discharge lamp lighting device according to any one of claims 1 to 5,
A lamp socket for electrically connecting a discharge lamp to be lit and the discharge lamp lighting device;
A lighting apparatus comprising:

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