JP2010232064A - Discharge lamp lighting device, lighting device - Google Patents

Abstract

[PROBLEMS] To suppress flickering, extinction, and jump phenomenon during dimming even when the ambient temperature is lowered, to achieve stable dimming lighting, and to perform smooth continuous dimming with a simple circuit configuration. A discharge lamp device is provided.
A first frequency is set to adjust power supplied to a discharge lamp, and a second frequency is set near a resonance frequency of a series resonance circuit including a ballast coil and a resonance capacitor. The first frequency command signal and the second frequency command signal are independently output from the inverter control circuit 15, the first frequency command signal is smoothed through the low pass filter 19a, and the second frequency command value signal is passed through the low pass filter 19b. The slope of rise and fall was moderated.
[Selection] Figure 1

Description

  The present invention relates to a device for lighting a discharge lamp and a lighting device including a discharge lamp to be lit using the device, and particularly to a device capable of dimming lighting.

The structure of the discharge lamp lighting device with dimming lighting function is to turn on the discharge lamp at high frequency using an inverter circuit that converts commercial AC power into high frequency voltage, and adjust the drive frequency of the inverter circuit to adjust the ballast coil and resonance In general, dimming is performed by adjusting the power supplied to the discharge lamp by changing the resonance characteristics of a resonance circuit including a capacitor and a discharge lamp.
In such a discharge lamp lighting device, the lighting state of the discharge lamp becomes unstable during dimming lighting with a low luminous flux, and a phenomenon such as flickering or extinction may occur.

In addition, when the ambient temperature is low, for example, 0 ° C., the characteristics of the discharge lamp are different from those at room temperature, for example, 25 ° C., and the discharge lamp voltage during dimming lighting is very high. For this reason, when the ambient temperature is low, the voltage for stably lighting the discharge lamp cannot be supplied from the discharge lamp lighting device, so that stable lighting becomes difficult, and a phenomenon called a jump phenomenon in which the luminous flux of the lamp changes rapidly occurs. To do.

Therefore, conventionally, “the stability of the light quantity in the region where the light output of the discharge lamp is a low luminous flux is improved, and a wide range of light control is possible. As a technique for the purpose, “the chopper circuit CP outputs a DC voltage, and the inverter circuit INV converts the DC voltage into a high-frequency voltage and supplies high-frequency power to the discharge lamp La through the resonance circuit. The output voltage of the chopper circuit CP and the operating frequency of the inverter circuit INV are determined by a voltage command value and a frequency command value determined by the microcomputer MPU with a dimming signal dim from the outside. The microcomputer MPU periodically generates a first command value and a second command value corresponding to the frequency command value, and a voltage waveform applied to the discharge lamp La in response to the second command value is determined by the microcomputer MPU. In addition, the voltage is set to be equal to or higher than the voltage applied to the discharge lamp La in response to the first command value. Is proposed (see Patent Document 1).

Patent Document 1 states that “a D / A converter that converts a frequency command signal that is a digital signal output from the command value determining means into the frequency command value that is an analog value, and an output from the D / A converter. It is also disclosed that a voltage-controlled oscillator that operates an inverter circuit at a frequency proportional to a frequency command value, which is a voltage signal to be generated, and a D / A converter uses a ladder resistor.

Japanese Patent No. 4175027 (abstract, claim 2)

Regarding the control of the inverter drive frequency, the technique described in Patent Document 1 uses a microcomputer MPU in the control circuit to simplify the configuration of the control unit, and the microcomputer MPU outputs a frequency command signal that is a multi-bit digital signal. Then, an inverter drive frequency is generated using a D / A converter (DAC) and a voltage controlled oscillator (VCO). Further, according to Patent Document 1, “when the command value Df changes abruptly, the first command value generation unit 14 functioning as a low-pass filter delays the first command value Df1 given to the output unit 18. Therefore, flickering of the light output of the discharge lamp La accompanying a sudden change in the dimming signal dim can be prevented, and stress on the switching element of the inverter circuit INV can be suppressed. It is said.

In the above-described technique, in the case where the dimming signal dim changes suddenly, the first command value generation unit 14 functioning as a low-pass filter delays the dimming signal dim even if the dimming signal dim suddenly. Since the delay is made so that the value Df changes slowly, the stress on the switching element of the inverter can be reduced. However, the following problem occurs even when the delay is made.

For example, assume that the frequency command value is changed by the dimming signal. At this time, since the frequency command signal output from the microcomputer MPU is a digital signal, even if the command value is delayed in the first command value generation unit 14 functioning as a low-pass filter, the frequency command signal becomes a discrete value. It will change to (stepped). For this reason, when dimming the discharge lamp, if the frequency change width in one step is large, the brightness changes stepwise, and smooth continuous dimming cannot be performed. This is because the power change to the lamp changes abruptly because the frequency change width of one step is large, and the brightness changes abruptly.

According to Patent Document 1, “the first command value Df1 is set during the timing pulse Tp off period, and the second command value Df2 is set during the on period of the timing pulse Tp. If the dimming signal dim is constant, the first command value command value D1 is constant. On the other hand, the second command value Df2 increases after decreasing with time, so the first command value Df1 and the second command value The frequency command signal Do synthesized with the value Df2 is as shown in FIG. 2 (c) ”. The second frequency command value gradually changes the frequency command value with time, and the switching element of the inverter circuit Suppresses stress. However, as described above, even if the frequency is gradually changed over time, the frequency changes stepwise if the frequency change width of one step is large because it is a digital signal. , Ballast coil noise may occur.

The present invention has been made to solve the above-described problems. Even when the ambient temperature is lowered, flickering, extinction, and jumping phenomenon can be suppressed during dimming, and stable dimming lighting can be achieved. An object of the present invention is to provide a discharge lamp device capable of performing smooth continuous light control.

A discharge lamp lighting device according to the present invention includes a first inverter drive frequency command signal determined in accordance with an inverter circuit that changes a DC power supply to a high frequency voltage and supplies the discharge lamp to the discharge lamp, and a dimming signal input from the outside. And a control means for independently outputting a second inverter drive frequency command signal for applying a predetermined voltage to the discharge lamp at a predetermined cycle, and a terminal for outputting the first and second frequency command signals of the control means. A low-pass filter connected to each; selection means for selecting and outputting the first and second command signals via the low-pass filter; and operating the inverter circuit based on the signal output from the selection means And an inverter driving circuit.

According to the discharge lamp lighting device of the present invention, the inverter control circuit outputs the first frequency command signal and the second frequency command signal independently, and the time constant of the low-pass filter circuit connected to each output is independent. Thus, it is possible to periodically apply a pulsed voltage to the lamp while suppressing flickering of the discharge lamp, noise, and stress increase of the switching element.
In addition, the level difference of light generated by the digital dimming method can be suppressed and smooth continuous dimming can be performed.

1 is a configuration diagram of a discharge lamp lighting device according to Embodiment 1. FIG. The signal waveform of a 1st frequency command signal and a 2nd frequency command signal is shown. The signal waveform of a 1st frequency command signal and a 2nd frequency command signal is shown. The signal waveform of a 1st frequency command signal and a 2nd frequency command signal is shown. The signal waveform of a 1st frequency command signal and a 2nd frequency command signal is shown. The comparison of the signal waveform of a frequency command signal is shown. The signal waveform of a 1st frequency command signal is shown. 1 is a configuration diagram of a discharge lamp lighting device according to Embodiment 1. FIG. The signal waveform of a 1st frequency command signal and a 2nd frequency command signal is shown. It is a block diagram of the discharge lamp lighting device concerning Embodiment 2. The relationship between the 2nd frequency command signal in Embodiment 3, and a light control rate is shown. The signal waveform of a 2nd frequency command signal is shown. FIG. 6 is a side sectional view of a lighting device according to Embodiment 4.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a discharge lamp lighting device according to Embodiment 1 of the present invention.
In FIG. 1, a discharge lamp lighting device is a device that turns on a discharge lamp 10 by receiving power from a commercial AC power supply 1, and includes a rectifier circuit 2, an inductor 3, a switching element 4, a diode 5, a smoothing capacitor 6, and switching. Elements 7a and 7b, ballast coil 8, resonance capacitor 9, discharge lamp 10 (when mounted), DC cut capacitor 11, preheating DC cut capacitor 12, preheating transformer 13, capacitors 14a and 14b, inverter control unit 15, dimmer controller 16, voltage dividing resistors 17a, 17b, 18a, 18b, low-pass filters 19a, 19b, a selection circuit 20, a voltage controlled oscillator (VCO) 21, and a driver 22.

The rectifier circuit 2 performs full-wave rectification on the AC voltage supplied from the commercial AC power supply 1.
The inductor 3, the switching element 4, the diode 5, and the smoothing capacitor 6 constitute a boost chopper circuit, which boosts and smoothes the DC voltage that has been full-wave rectified by the rectifier circuit 2.
The switching elements 7a and 7b and the DC cut capacitor 11 constitute a half-bridge inverter circuit and are connected in parallel to the smoothing capacitor 6 to convert the DC voltage into a high frequency.

The driver 22 drives the switching elements 7a and 7b based on a control signal for turning on / off the switching element output from the voltage controlled oscillator 21. The voltage controlled oscillator 21 outputs an inverter drive frequency based on the frequency command signal output from the selection circuit 20.
The ballast coil 8 and the resonance capacitor 9 connected to the output of the inverter circuit form an LC series resonance circuit.
The DC cut capacitor 11 plays a role of cutting a DC component.

  The primary winding of the preheating transformer 13 is connected to the output of the inverter circuit via a preheating DC cut capacitor 12, and the secondary winding of the preheating transformer 13 is connected to the filament of the discharge lamp 10 via capacitors 14a and 14b. , Preheat the filament.

The inverter control unit 15 is configured by a calculation device such as a microcomputer or a CPU (Central Processing Unit), and a first frequency command signal and a second frequency command signal for instructing a drive frequency (for each of the switching elements 7a and 7b) of the inverter circuit. Is output.
The first frequency is set to adjust the input power to the discharge lamp 10, and the second frequency is set near the resonance frequency of the series resonance circuit including the ballast coil 8 and the resonance capacitor 9. By periodically driving at the second frequency, a high voltage (hereinafter referred to as pulse voltage) is periodically applied to the discharge lamp 10, and the discharge of the discharge lamp 10 is maintained and dimmed when the light is dimmed. -Flicker can be suppressed. Here, the second frequency is set in the vicinity of the resonance frequency of the series resonance circuit including the ballast coil 8 and the resonance capacitor 9, but is set to a value higher than the resonance frequency. If the value is set lower than the resonance frequency, the inverter circuit operates in the phase advance region, and the worst inverter circuit may be damaged.

The selection circuit 20 receives the first frequency command signal and the second frequency command signal output from the inverter control unit 15 as voltage signals via the voltage dividing resistors 17a, 17b, 18a, 18b and the low-pass filters 19a, 19b. The higher (or lower) voltage value of the first frequency command signal or the second frequency command signal is output to the voltage controlled oscillator 21.
The dimming controller 16 outputs a dimming signal that indicates the dimming rate of the discharge lamp 10 (the illuminance ratio when the illuminance during rated lighting is 100%) to the inverter control unit 15. The inverter control unit 15 determines an inverter drive frequency based on the dimming signal.

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

(1) Turning on the commercial AC power source 1 When the commercial AC power source 1 is turned on to the discharge lamp lighting device, the rectifier circuit 2 rectifies the AC voltage supplied from the commercial AC power source 1, and the obtained DC voltage is the inductor 3, switching The voltage is boosted and smoothed by a boost chopper circuit composed of the element 4, the diode 5 and the smoothing capacitor 6.
The DC power source smoothed by the smoothing capacitor 6 is converted into a high-frequency voltage when the switching elements 7a and 7b of the inverter circuit are alternately turned on and off.

(2) Filament preheating mode After the commercial AC power supply 1 is turned on and before the discharge lamp 10 is turned on, the inverter control unit 15 enters a state of operating in a preheating mode in which the filament provided in the discharge lamp 10 is preheated in advance.
Preheating here means that the temperature of the filament is raised to a temperature suitable for the start of discharge in a state before the discharge lamp 10 starts discharge.
The inverter control unit 15 outputs a frequency command value for operating the inverter circuit at a sufficiently high inverter drive frequency so that the voltage applied to the discharge lamp 10 is equal to or lower than the discharge start voltage, and the secondary winding of the preheating transformer 13 More preheating current is supplied to the filament to preheat the filament.
In addition, in order to keep the filament temperature optimal after the start of discharge, supply of preheating current is continued.

(3) Start mode to lighting mode When sufficient time has elapsed since the start of the preheating mode, for example, when the preheating of the filament is completed, the inverter control unit 15 sets the inverter circuit in the start mode to light the discharge lamp 10. To control.
The start mode is a mode in which the drive frequency of the inverter circuit is brought close to the resonance frequency of the LC resonance circuit including the ballast coil 8 and the resonance capacitor 9 from a sufficiently high frequency (preheating frequency) that is equal to or lower than the discharge start voltage. Needless to say, preheating frequency> resonance frequency.
When the drive frequency of the inverter circuit approaches the resonance frequency of the LC resonance circuit described above, a high voltage is applied to the discharge lamp 10, so that the discharge lamp 10 starts to discharge and lights up, and enters a lighting mode.

  Here, FIG. 2 shows the first frequency command signal and the second frequency command signal output from the inverter control unit 15. FIG. 2 (a) is a first frequency command signal, which is a PWM signal, which is sufficiently smoothed through the low-pass filter 19a, and a DC voltage signal proportional to the pulse width is obtained. Fig. 2 (b) is the second frequency command signal, not a PWM signal, but a rectangular wave pulse signal with a constant amplitude and period. The rectangular wave pulse signal output from the inverter control unit 15 is input to the low-pass filter 19b via the voltage dividing resistors 18a and 18b, and is converted into a waveform having a gentle rise and fall.

The first frequency command signal and the second frequency command signal that have passed through the low-pass filters 19a and 19b are input to a selection circuit 20 that constitutes an analog OR circuit (maximum value circuit). The analog OR circuit has a characteristic of outputting the higher voltage of the command signal with respect to the input of the two frequency command signals (see FIG. 2C). Based on this signal, a pulsed voltage is periodically applied to the discharge lamp as shown in FIG. 2 (d). Here, it is assumed that the voltage controlled oscillator 21 has a characteristic that the output frequency decreases when the voltage of the input signal increases, and the output frequency increases when the voltage of the input signal decreases.

Assume that a dimming signal indicating a dimming rate of 100% is output from the dimming controller 16 in the lighting mode. Since the discharge lamp discharge is stable when the dimming rate is near 100%, it is not necessary to apply a pulse voltage with the second frequency to the discharge lamp 10. The inverter control unit 15 receives the dimming signal from the dimming controller 16, and determines and outputs the first frequency command value by a table or conversion equation in which the frequency command value is associated with the dimming signal. As described above, the frequency command value in the vicinity of the resonance frequency of the resonance circuit including the ballast coil 8 and the resonance capacitor 9 is set by the voltage dividing resistors 18a and 18b, and the second frequency command signal is output for a predetermined period. As shown in FIG. 3, when 100% is lit, since the voltage value of the first frequency command signal is higher than the second frequency command signal, only the first frequency command signal is selected via the selection circuit 20. Only the first frequency command signal is input to the voltage controlled oscillator 21. Accordingly, no pulse voltage is applied to the discharge lamp 10.

Next, when a dimming signal (for example, 50% to 30%) in which the dimming rate indicates the middle luminous flux region is output from the dimming controller 16, the first frequency command signal corresponding to the dimming signal (FIG. 4). (a)) and a second frequency command signal (see FIG. 4 (b)) set in the vicinity of the resonance frequency of the resonance circuit composed of the ballast coil 7 and the resonance capacitor 9 is output. The smoothed first frequency command signal and second frequency command signal are input to the selection circuit 20 through the low-pass filters 19a and 19b. Then, as shown in FIG. 4C, the higher voltage value of each of the first frequency command signal and the second frequency command signal is output from the selection circuit 20 and input to the voltage controlled oscillator 21. The frequency is modulated according to the signal waveform output from the selection circuit 20, and a pulsed voltage is periodically applied to the lamp. Note that the dimming rate at which the application of the pulse voltage starts is different depending on the type of discharge lamp used.

Next, the first frequency command signal, the second frequency command signal, and the voltage controlled oscillator input when the dimming controller 16 outputs a dimming signal (for example, 20% to 5%) indicating a light flux region where the dimming rate is low. The waveform is shown in FIG. As described above, the input waveform of the voltage controlled oscillator 21 is that the signal having the higher voltage of each of the first frequency command signal and the second frequency command signal is output from the selection circuit 20, and compared with FIG. It can be seen that the voltage of the command signal is smaller. The frequency is modulated according to this waveform, and a pulsed voltage is periodically applied to the lamp.

Here, the second frequency command signal rises through the low-pass filter 19b, and the slope of the fall is gentle, but when not passing through the low-pass filter circuit 19b, when the pulsed voltage is periodically applied to the discharge lamp, Since the frequency changes abruptly, it leads to flickering due to a rapid change in lamp current and lamp voltage, noise increase, and switching element stress increase. Further, when the frequency command value is output as a digital value as in Patent Document 1 and the command value is input to the voltage controlled oscillator 21 via the D / A converter, the frequency command value as shown in FIG. The value becomes discrete and the frequency changes stepwise. In this method, as shown in FIG. 6 (b), the second frequency command value output from the inverter control unit 15 is converted into a continuous frequency command value via the low-pass filter 19b. It can be applied to the discharge lamp 10. Thereby, it is possible to suppress flickering of the discharge lamp 10, to reduce noise, and to suppress an increase in stress of the switching element.

Also, as shown in FIG. 7, even when the first frequency command value output from the inverter control circuit 15 changes suddenly, the input signal to the selection circuit 20 changes slowly and continuously by the low-pass filter 19a. , Enables smooth continuous dimming.

Further, since the first frequency command value is a PWM signal output from the microcomputer, when the first frequency command value changes due to a change in the dimming signal, the accompanying change in pulse width is discrete, but the low-pass The input signal to the selection circuit 20 is continuously and smoothly changed by the filter circuit 19a, and there is no flicker accompanying a steep frequency change, and smooth continuous light control is possible.

Here, the low-pass filter 19a is set to a sufficiently large time constant Ta so that it does not feel flickering to the human eye when the first frequency command value changes suddenly due to a sudden change in the dimming signal, etc. Is set to a time constant Tb so that the gradient of the voltage applied to the discharge lamp does not become steep when a pulsed voltage is periodically applied to the discharge lamp. In this case, the relationship between the time constants of the low-pass filters 19a and 19b is Ta> Tb. Incidentally, in the example of Patent Document 1, since the first command value and the second command value are alternately output from the same output of the microcomputer, the frequency command signal output from the microcomputer cannot be appropriately smoothed.

As described above, since the first frequency command signal and the second frequency command signal are output independently in this method, the time constants of the low-pass filters 19a and 19b can be set to optimum values independently. This makes it possible to suppress the level difference of light generated by the digital dimming method and to perform smooth continuous dimming.

Therefore, the discharge lamp lighting device of Embodiment 1 can perform smooth continuous light control, and can suppress flickering, extinction, and jump phenomenon during light control even when the ambient temperature decreases, and stable light control. It achieves lighting.

In the present embodiment, the voltage controlled oscillator 21 has a characteristic in which the output frequency is decreased when the frequency command signal voltage is increased and the output frequency is increased when the signal voltage is decreased. When a voltage controlled oscillator having the characteristic that the output frequency is lowered when the signal voltage is lowered and the output frequency is raised when the signal voltage is increased, an analog AND circuit (minimum value circuit) is used for the selection circuit 20 as shown in FIG. A similar function can be achieved. That is, although detailed explanation is omitted, the analog AND circuit has a characteristic of outputting the lower one of the command signal voltages with respect to the input of the two frequency command signals, so the first frequency command value, the second week frequency command The value and voltage controlled oscillator input waveform is a signal as shown in FIG.

Embodiment 2
FIG. 10 is a configuration diagram of a discharge lamp lighting device according to Embodiment 2 of the present invention. In FIG. 10, the discharge lamp lighting device is a device that turns on the discharge lamp 10 by receiving power from the commercial AC power supply 1, and includes a rectifier circuit 2, an inductor 3, a switching element 4, a diode 5, a smoothing capacitor 6, and a switching device. Elements 7a and 7b, ballast coil 8, resonant capacitor 9, discharge lamp 10 (when mounted), DC cut capacitor 11, preheating DC cut capacitor 12, preheating transformer 13, capacitors 14a and 14b, inverter control unit 15, dimming A controller 16, voltage dividing resistors 17a, 17b, 18a, 18b, low-pass filters 19a, 19b, a selection circuit 20, a voltage controlled oscillation (VCO) 21, a driver 22, an inverter current detection resistor 23, and an error amplifier 24 are provided.

The inverter current detection resistor 23 and the error amplifier 24 constitute power feedback control means. The current flowing through the switching element 7b of the inverter circuit is detected by the inverter current detection resistor 23, and the power consumed on the load side of the inverter circuit is detected equivalently. The signal detected by the inverter current detection resistor 23 is input to the inverting input terminal of the error amplifier 24, and the power command signal output from the selection circuit 20 is input to the non-inverting input terminal. The error amplifier 24 amplifies the difference between the detection signal and the power command signal, and the voltage controlled oscillator 21 converts the output voltage of the error amplifier 24 into a frequency and outputs it. The driver 22 drives the switching element in accordance with the frequency output from the voltage controlled oscillator 21 and adjusts the inverter driving frequency in a direction that reduces the difference between the detection signal and the power command signal.

The inverter control unit 15 is configured by an arithmetic device such as a microcomputer or a CPU, as in the first embodiment. However, the part different from the first embodiment is the first power command signal that the inverter control unit instructs the target power value. And a second power command signal is output.
The first power command signal is set to adjust the input power to the discharge lamp 10, and the second power command signal is set so that a larger amount of power is input to the discharge lamp 10 than the first power command signal. Is set. That is, at the time of low luminous flux dimming, the second power command signal is set to a larger power compared to the first power command signal, and therefore the inverter frequency of the resonance circuit including the ballast coil 7 and the resonance capacitor 9 is set during this period. Since it moves to the vicinity of the resonance frequency, a pulse voltage is applied to the discharge lamp, and the discharge of the discharge lamp 10 is maintained when dimming to a low luminous flux state, and extinction and flickering can be suppressed.

The present embodiment is different from the first embodiment in that it has a feedback control function of inverter output. In the absence of a feedback control function, there is a problem that output fluctuations increase due to changes in the characteristics of the discharge lamp due to changes in ambient temperature, life conditions, product variations, and the like.

Next, the operation of the discharge lamp lighting device according to Embodiment 2 will be described. The same parts as those in the first embodiment are omitted.

After the power is turned on, the filament preheating mode and the start mode are entered to enter the lighting mode, and the discharge lamp lights up.
Here, the operation of the inverter control unit 15 when a dimming signal is output from the dimming controller 16 will be described. The inverter control unit 15 that has received the dimming signal from the dimming controller 16 determines the target value of the first power command signal using, for example, a table or conversion formula that associates the power command value according to the dimming signal. The inverter control unit 15 outputs a PWM pulse signal corresponding to the determined target value. For example, when the target power is high, the pulse width is long, and when the target power is low, the pulse width is short. In the present embodiment, the second power command value is fixed, and the pulse level output from the inverter control unit 15 is divided by the voltage dividing resistors 18a and 18b to determine the signal level.

FIG. 3 shows the first power command signal, the second power command signal, and the output signal of the selection circuit 20 when a dimming signal of 100% lighting is output from the dimming controller 16. FIG. 3 is treated as a frequency command signal in the first embodiment, but will be described as a power command signal in this embodiment. The selection circuit 20 is an analog OR circuit (maximum value circuit). The inverter control circuit 15 outputs a first power command signal (see FIG. 3 (a)) and a second power command signal (see FIG. 3 (b)) as PWM signals corresponding to the 100% dimming rate.

The first power command signal is converted into a DC voltage through a low-pass filter 19a, and the second command signal is converted into a waveform with a gradual rise and fall of a pulse through a low-pass filter 19b. The first and second power command signals through the low-pass filter are input to the selection circuit 20, respectively. Since the selection circuit 20 outputs the higher one of the two input signals, a power command signal as shown in FIG. 3 (c) is output. At 100% lighting, the first power command value is higher than the second power command value, so only the first power command value is output and no pulse voltage is applied to the discharge lamp 10.

The power command signal output from the selection circuit 20 is input to the non-inverting input terminal of the error amplifier 24 and is compared with the detection signal of the inverter current detection resistor 23. The voltage controlled oscillator 21 outputs the drive frequency of the inverter circuit according to the output voltage of the error amplifier 24, and performs feedback control by controlling the frequency so as to substantially coincide with the power command value.

FIG. 4 shows the first power command signal, the second power command signal, and the output signal of the selection circuit 20 when a dimming signal (for example, 50% to 30) in the middle luminous flux region is output from the dimming controller 16. FIG. 4 is treated as a frequency command signal in the first embodiment, but will be described as a power command signal in this embodiment. The inverter control unit 15 outputs a first power command signal and a second power command signal of a PWM signal corresponding to the dimming rate. Waveforms passing through the low-pass filters 19a and 19b are each smoothed and input to the selection circuit 20. As shown in FIG. 4C, the output of the selection circuit 20 is output with the higher voltage value of each of the first frequency command signal and the second frequency command signal and is input to the non-inverting input terminal of the error amplifier 24. Thus, it is compared with the detection signal of the inverter current detection resistor 23.

Here, as shown in FIG. 4 (C), the target power command value input to the non-inverting input terminal of the error amplifier 24 is a waveform with a high signal voltage periodically because of the second frequency command value. The feedback control works so that the input power to 10 is increased. Accordingly, during this period, the inverter frequency moves to the vicinity of the resonance frequency of the resonance circuit composed of the ballast coil 8 and the resonance capacitor 9, and a pulse voltage is applied to the discharge lamp 10 as shown in FIG. When this happens, the discharge lamp discharge is maintained, and it is possible to suppress extinction and flickering. Note that the dimming rate at which the application of the pulse voltage starts is different depending on the type of discharge lamp used.

Next, FIG. 5 shows the first power command signal, the second power command signal, and the output signal of the selection circuit 20 when a dimming signal (for example, 20% to 5%) in the low luminous flux region is output from the dimming controller 16. Show. FIG. 5 is treated as a frequency command signal in the first embodiment, but will be described as a power command signal in this embodiment. Similarly, the signal having the higher voltage of the first frequency command signal and the second frequency command signal is output from the selection circuit 20 and input to the non-inverting input terminal of the error amplifier 24 to detect the power of the inverter current detection resistor 23. Compared with signal. The waveform of the power command value is a waveform in which the signal voltage increases periodically because of the second frequency command signal, and a pulsed voltage is periodically applied to the discharge lamp by feedback control.

Here, when the power command signal is output as, for example, a digital value and input directly to the non-inverting input terminal of the error amplifier via the D / A converter as in the conventional case, the power command signal shown in FIG. Similarly, the target power value becomes discrete, and the power command value changes stepwise. When the power command value becomes discrete, the drive frequency of the inverter changes sharply following the change of the power command value by feedback control. In this method, the pulsed voltage can be smoothly applied to the lamp by setting the second power command value output from the inverter control circuit 15 as a continuous power command value via the low-pass filter circuit 19b. Thereby, it is possible to suppress flickering of the discharge lamp, noise reduction, and increase of stress of the switching element.

Even when the first power command value output from the inverter control circuit 15 changes suddenly due to a sudden change in the dimming signal, the low-pass filter 19a causes the input signal to the selection circuit 20 to be gradually continuous. Therefore, smooth continuous dimming is possible.

Furthermore, since the first power command value is a PWM signal output from the microcomputer, when the first power command value changes due to a change in the dimming signal, the accompanying change in pulse width is discrete, but the low-pass The input signal to the selection circuit 20 is continuously and smoothly changed by the filter circuit 19a, and there is no flicker accompanying a steep frequency change, and smooth continuous light control is possible.

Here, the low-pass filter 19a is set to a sufficiently large time constant Ta so that it does not feel flickering to the human eye when the first power command value changes suddenly due to a sudden change in the dimming signal, etc. Is set to a time constant Tb so that the slope of the voltage applied to the discharge lamp does not become steep when a pulsed voltage is periodically applied to the discharge lamp. In this case, the relationship between the time constants of the low-pass filters 19a and 19b is Ta> Tb.

As described above, in this method, by using feedback control, it is possible to suppress changes in characteristics due to changes in ambient temperature of the discharge lamp, life status, product variations, etc., and the first power command signal and the second Since the power command signal is output independently, it is possible to set the time constant of each low-pass filter independently, suppressing the step of light generated by the digital dimming method and performing smooth continuous dimming. it can.

Therefore, the discharge lamp lighting device according to the second embodiment can perform smooth continuous light control, and can suppress flickering, extinction, and jump phenomenon during light control even when the ambient temperature decreases, and stable light control. It achieves lighting.
In this embodiment, the power supplied to the load circuit is detected equivalently from the current detection resistor 23 connected to the switching element 7b of the inverter circuit. For example, the current of the discharge lamp is detected by a current transformer or the like. Thus, the first lamp current command value and the second lamp current command value may be output from the inverter control circuit 15, and any means can be used as long as it can electrically detect the lamp output state. Absent.

Embodiment 3
In the third embodiment of the present invention, a procedure for changing the second frequency command value shown in the first embodiment in accordance with the dimming signal will be described. In addition, since the circuit configuration and the like are the same as those of the first embodiment, description thereof is omitted.

In the first embodiment, the second frequency command value is set in the vicinity of the resonance frequency of the resonance circuit composed of the ballast coil 8 and the resonance capacitor 9, and the value is obtained by dividing the fixed amplitude value output from the inverter control circuit 15 by the voltage dividing resistor. The voltage was divided by 18a and 18b and input to the selection circuit 20. In the present embodiment, a method for variably adjusting the second frequency command value according to the dimming rate will be described.

FIG. 11 shows an example of the second frequency command value with respect to the dimming rate. The region on the right side of the broken line in the figure is a region where the pulse voltage is not applied as a region where the discharge is stable.
In the region on the left side of the broken line, for example, as shown in the figure, the second frequency is made higher than the vicinity of the resonance frequency as the dimming rate (low luminous flux) becomes low. That is, the second frequency gradually increases from the vicinity of the resonance frequency and deviates from the resonance point.
The impedance of the discharge lamp increases as the dimming rate decreases. When the impedance of the discharge lamp increases, the resonance action by the ballast coil 8 and the resonance capacitor 9 becomes stronger, and an excessive voltage may be applied to the discharge lamp. When the second frequency command value is a fixed value, the lamp impedance rises at the time of low dimming, and an excessive voltage may be applied to the discharge lamp 10, and stress is applied to the circuit components of the inverter. Therefore, by controlling the second frequency as shown in the figure, it is possible to suppress an excessive voltage from being applied to the discharge lamp 10 at the time of the low dimming rate.

Therefore, the second frequency command value is output from the inverter control circuit 15 as shown in FIG. The PWM signal is smoothed as shown in the figure via the low-pass filter 19b and input to the selection circuit 20. The time constant of the low-pass filter 19b is set to a value at which the PWM signal is sufficiently smoothed and the rise and fall of the smoothed signal are sufficiently gentle. As the pulse width of the PWM signal becomes smaller, the second frequency command value becomes smaller (see FIG. 12 (a)), and as the pulse width becomes larger, the second frequency command value becomes larger (see FIG. 12 (b)). By varying the pulse width of the PWM signal in accordance with the dimming rate, a pulse voltage corresponding to the dimming rate can be applied to the discharge lamp 10.

In this embodiment, the second frequency command value is output by PWM from the inverter control circuit 15. However, when the second power command value is output as a PWM signal, the dimming rate is adjusted. Accordingly, the second power command value can be adjusted, and similarly, a pulsed voltage can be periodically applied to the discharge lamp. Also, since feedback control is used, output fluctuations due to changes in characteristics due to changes in ambient temperature of the discharge lamp, life state, characteristic variations, and the like can be suppressed.

As described above, the second frequency command value or the second power command value output from the inverter control circuit 15 is set as a PWM signal, and the pulse voltage corresponding to the dimming rate is set through the low-pass filter 19b. It is possible to suppress the component stress of the inverter circuit.
Therefore, smooth continuous dimming can be performed, and even when the ambient temperature decreases, flickering, extinction, and jumping phenomenon during dimming can be suppressed, and stable dimming lighting can be achieved.

Embodiment 4
FIG. 13 is a side cross-sectional view of a lighting apparatus according to Embodiment 4 of the present invention.
The discharge lamp lighting device 29 described in any of the first to third embodiments is housed inside the illumination device main body 25, and the discharge lamp 28 is mounted on a lamp socket 26 outside the illumination device main body 25, and the wiring 27 Is connected to the discharge lamp lighting device 29 to form a lighting device.

  According to the lighting device according to the fourth embodiment, smooth continuous light control can be performed, and even when the ambient temperature decreases, flickering, extinction, and jumping phenomenon can be suppressed, and stable light control can be performed. It achieves lighting.

1 commercial AC power supply, 2 rectifier circuit, 3 boost inductor, 4 switching element Short-circuit prevention diode, 6 Smoothing capacitor, 7a, 7b, Switching element 8 Ballast coil, 9 Resonance capacitor, 10 Discharge lamp 11 DC cut capacitor, 12, Preheating DC cut capacitor, 13 Preheating tonlas, 14, Capacitor, 15 Inverter controller , 16 Dimming controller, 17a / 17b / 18a / 18b voltage dividing resistor, 19a / 19b low pass filter, 20 selection circuit, 21 voltage controlled oscillator, 22 driver, 23 inverter current detection resistor, 24 error amplifier, 25 instrument body, 26 lamp socket, 27 wiring, 28 discharge lamp, 29 discharge lamp lighting device

Claims (10)

  An inverter circuit that changes the DC power supply to a high frequency voltage and supplies it to the discharge lamp, a first inverter drive frequency command signal determined according to a dimming signal input from the outside, and a predetermined voltage to the discharge lamp at a predetermined cycle Control means for independently outputting a second inverter drive frequency command signal to be applied; a low-pass filter connected to each of the terminals for outputting the first and second frequency command signals of the control means; And a selection means for selectively outputting the first and second command signals via a low-pass filter, and an inverter drive circuit for operating the inverter circuit based on the signal output from the selection means. Electric light lighting device. The low-pass filter sets a time constant of a low-pass filter connected to a terminal that outputs the first frequency command signal to be larger than a time constant of a low-pass filter connected to a terminal that outputs the second frequency command signal. The discharge lamp lighting device according to claim 1. 2. The discharge lamp lighting device according to claim 1, wherein the second inverter drive frequency command signal is set to be higher than a resonance frequency of a series resonance circuit including a ballast coil and a resonance capacitor which are components of the inverter circuit. . An inverter circuit that changes the DC power supply to a high-frequency voltage and supplies it to the discharge lamp, a first output command signal determined according to a dimming signal input from the outside, and a predetermined voltage applied to the discharge lamp for a predetermined period A control means for independently outputting a second output command signal, a low-pass filter connected to each of the terminals for outputting the first and second command signals of the control means, and the low-pass filter. Selection means for selectively outputting the first and second output command signals, output detection means for electrically detecting the output of the discharge lamp, detection signal output from the previous output detection means, and the selection circuit A discharge lamp lighting device comprising: feedback control means for comparing the output command signals output from the control circuit and adjusting the frequency of the inverter circuit in a direction in which the detection signal in the previous period coincides with the output command signal. The low-pass filter sets a time constant of a low-pass filter connected to a terminal that outputs the first output command signal to be larger than a time constant of a low-pass filter connected to a terminal that outputs the second output command signal. The discharge lamp lighting device according to claim 4. The control means outputs the first and second frequency command signals as PWM signals, and determines a pulse width of the PWM signal according to a dimming signal input from the outside. And the discharge lamp lighting device in any one of Claim 3 5. The control means outputs the first and second output command signals as PWM signals, and determines a pulse width of the PWM signal according to a dimming signal input from the outside. And the discharge lamp lighting device in any one of Claim 5 8. The maximum value output circuit for comparing the two command signals output independently from the control means and outputting the larger one of the signal voltages. The discharge lamp lighting device according to 1. 8. The minimum value output circuit, wherein the selection unit compares two command signals output independently from the control unit and outputs the smaller one of the signal voltages. The discharge lamp lighting device according to 1.   An illumination device comprising: the discharge lamp lighting device according to any one of claims 1 to 9; and a discharge lamp that is turned on by the discharge lamp lighting device.

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