JP5447959B2 - Discharge lamp lighting device and lighting control method thereof - Google Patents

Description

  The present invention relates to a discharge lamp lighting device for lighting a high-pressure discharge lamp used for projectors, indoor and outdoor lighting, and the lighting control method thereof.

  Conventionally, high-pressure discharge lamps such as metal halide lamps have been realized in small size, high brightness, and high efficiency, so they are widely used as light sources for projection devices such as liquid crystal projectors or outdoor lighting such as road lighting. It has come to be.

  However, for example, when high-frequency lighting is performed at a high frequency of 1 kHz or more, a standing wave is generated by the interference action between the traveling wave of the sound wave generated in the lamp and the reflected wave, and there is an amplitude of the pressure change in the tube caused by the standing wave. If the limit is exceeded, a so-called acoustic resonance phenomenon that causes a turn-off or lamp breakage is likely to occur, and the problem of arc instability due to this acoustic resonance phenomenon has been conventionally known.

  Conventionally, in a high pressure discharge lamp lighting device, in order to avoid the occurrence of such an acoustic resonance phenomenon, a configuration in which a relatively low-frequency rectangular wave alternating voltage is applied has been widely adopted. In such a configuration, a discharge lamp driving method has been proposed that stabilizes the starting position of an arc that is likely to be unstable (see, for example, Patent Document 1).

  The high pressure discharge lamp lighting device in Patent Document 1 includes a power conversion circuit in which the power supplied to the discharge lamp, which is a high-intensity discharge lamp, is variable by controlling on / off of the switching element, and the discharge lamp when the discharge lamp is stably lit. A control circuit for controlling on / off of a switching element of the power conversion circuit in a constant power mode in which constant power is supplied, and flicker detection means for detecting occurrence of flicker (flickering of light output) in the discharge lamp. The high power mode in which the power conversion circuit supplies more power than the power supplied to the discharge lamp in the constant power mode is selected during the lighting period of the discharge lamp and the flicker detection means detects flicker. As a result, the discharge lamp electrode and the bar can be controlled simply by changing the power supplied to the discharge lamp. It is possible to keep the temperature inside the lamp in an appropriate state, and as a result, it is possible to promote the formation of protrusions on the electrode and stabilize the position of the starting point of the arc, thereby suppressing the occurrence of flicker and further deteriorating the electrode It is said that the life of the discharge lamp can be extended by suppressing the above.

JP 2005-327744 A

However, the high pressure discharge lamp lighting device of Patent Document 1 has the following problems.
That is, in the technique described in Patent Document 1, when flicker is generated due to a temperature drop in the electrode or the bulb, the value of power supplied to the discharge lamp is higher than that in the steady state for a predetermined period from the occurrence of flicker. Therefore, during this period, the discharge lamp becomes brighter than normal, and as a result, the phenomenon that the discharge lamp becomes brighter or darker occurs, resulting in a problem that flicker (flicker) other than the original flicker occurs. is there.
Moreover, since the discharge lamps have variations in characteristics, it is difficult to determine whether or not the temperature in the bulb is appropriate for various discharge lamps by the control method of Patent Document 1.

  The present invention has been made in view of the above problems, and it is possible to accurately determine the occurrence of an acoustic resonance phenomenon with a simple and inexpensive circuit configuration, and to keep flicker (light output) while keeping the power supplied to the discharge lamp constant. It is an object of the present invention to provide a discharge lamp lighting device that suppresses the occurrence of flickering and suppresses deterioration of an electrode and extends the life of the discharge lamp.

  To achieve the above object, a discharge lamp lighting device according to the present invention includes a DC / DC converter circuit that boosts and / or steps down a DC voltage, and an inverter circuit that converts an output voltage of the DC / DC converter circuit into an AC voltage. A digital control means having a PWM control circuit for controlling a switching frequency of the DC / DC converter circuit and a lighting frequency of the inverter circuit, and an output voltage detection circuit for detecting the output voltage or the DC / DC converter circuit. In a discharge lamp lighting device comprising: at least one of output current detection circuits for detecting an output current; and supplying the AC voltage to the discharge lamp at a predetermined lighting cycle from the inverter circuit. The control means includes the output voltage detection circuit or the output in the lighting cycle. A moving average value for a predetermined number of detection values detected by the current detection circuit is calculated, and based on the difference information between the moving average value and the newly detected value, at the polarity switching timing of the next lighting cycle. A frequency switching determination processing circuit for outputting a frequency switching signal for instructing to change the switching frequency by a predetermined frequency to the PWM control circuit is provided (Claim 1).

  Further, in the discharge lamp lighting device according to claim 1, the switching frequency has an upper limit value and a lower limit value of a switchable frequency, and the switching frequency changed by the predetermined frequency is the switching before the change. The frequency change direction and the change amount are determined within the range of the upper limit value and the lower limit value in accordance with a frequency value (claim 2).

The discharge lamp lighting device according to claim 1, wherein the frequency switching determination processing circuit includes a moving average arithmetic circuit that calculates the moving average value, an offset circuit that outputs a predetermined offset value, and the moving An output signal when the newly detected value deviates from the threshold region by comparing the threshold value obtained by adding or subtracting the predetermined offset value to the average value and the newly detected value. And a counter that outputs the frequency switching signal to the PWM control circuit when the output signal is input and the number of inputs exceeds a predetermined number of times (Claim 3).

The discharge lamp lighting device according to claim 1, wherein the frequency switching determination processing circuit includes a moving average calculation circuit that calculates the moving average value, the moving average value, and a detection value that is newly detected. And a second comparator that outputs an output signal when the absolute value of the differential voltage exceeds a predetermined threshold, and the output signal And a counter that outputs the frequency switching signal to the PWM control circuit when the number of inputs exceeds a predetermined number of times (Claim 4).

The discharge lamp lighting device according to the present invention includes a DC / DC converter circuit that steps up or down a DC voltage, an inverter circuit that converts an output voltage of the DC / DC converter circuit into an AC voltage, and the DC / DC converter circuit. A control means having a PWM control circuit for controlling a switching frequency of the inverter circuit and a lighting frequency of the inverter circuit, and an output voltage detection circuit for detecting the output voltage or an output current detection circuit for detecting an output current of the DC / DC converter circuit. In a discharge lamp lighting device comprising at least one of the above and supplying the AC voltage to the discharge lamp at a predetermined lighting cycle from the inverter circuit, the control means includes: Detection value detected by the output voltage detection circuit or the output current detection circuit Based on difference information between the analog calculation circuit that performs an analog calculation of the average value for a predetermined number of times, and the average value and a detection value that is newly detected by inputting the signal of the average value from the analog calculation circuit, A frequency switching determination processing circuit for outputting a frequency switching signal for instructing to change the switching frequency by a predetermined frequency at the polarity switching timing of the lighting cycle is provided to the PWM control circuit. .

Further, a lighting control method for a discharge lamp lighting device according to the present invention includes a DC / DC converter circuit that boosts and / or steps down a DC voltage, an inverter circuit that converts an output voltage of the DC / DC converter circuit into an AC voltage, Digital control means having a PWM control circuit for controlling the switching frequency of the DC / DC converter circuit and the lighting frequency of the inverter circuit, and the output voltage detection circuit for detecting the output voltage or the output of the DC / DC converter circuit A lighting control method for a discharge lamp lighting device, comprising: at least one of output current detection circuits for detecting current; and supplying the AC voltage to the discharge lamp at a predetermined lighting cycle from the inverter circuit. The output voltage detection circuit or the output current detection circuit Based on difference information between a detection step for detecting the voltage or the output current, a moving average value calculation step for calculating a moving average value for a predetermined number of detection values, and the detected value newly detected. A comparison step of sending an output signal, and instructing to change the switching frequency by a predetermined frequency at the polarity switching timing of the next lighting cycle when the output signal is input and the number of inputs exceeds a predetermined number of times A counting step for outputting a frequency switching signal to the PWM control circuit; a PWM frequency changing step for changing an oscillation frequency based on the frequency switching signal at a polarity switching timing of the next lighting cycle; A switching frequency switching step for switching the switching frequency based on the oscillation frequency changed at the polarity switching timing; Characterized by comprising for each of the lighting cycle (claim 6).

Further, in the lighting control method for a discharge lamp lighting device according to claim 6, in the comparison step, a threshold value area obtained by adding / subtracting a predetermined offset value to / from the moving average value and the detected value newly detected. Is compared (claim 7).

Further, in the lighting control method for a discharge lamp lighting device according to claim 7, the offset value set in the comparison step is different for each switching frequency (claim 8).

Further, in the lighting control method for the discharge lamp lighting device according to claim 6, in the comparison step, an absolute value of a differential voltage between the moving average value and the newly detected value is compared with a predetermined threshold value. (Claim 9).

In the lighting control method for a discharge lamp lighting device according to claim 9, the predetermined threshold set in the comparison step is different for each switching frequency (claim 10).

Further, in the lighting control method for a discharge lamp lighting device according to any one of claims 6 to 10, the switching frequency switched at each polarity switching timing of the next lighting cycle is an upper limit value of the switchable frequency. The frequency change direction and the change amount are determined within the range of the upper limit value and the lower limit value according to the value of the switching frequency before the change (claim 11). ).

Further, in the lighting control method for a discharge lamp lighting device according to any one of claims 6 to 11, the switching frequency switched at each polarity switching timing of the next lighting cycle is the first switching frequency and the second switching frequency. The switching frequency is alternately switched (claim 12).

In the lighting control method for a discharge lamp lighting device according to any one of claims 6 to 12, the predetermined number of times set in the counting step is different for each switching frequency. 13).

Since the discharge lamp lighting device according to the present invention is configured as described above, it is possible to accurately determine the occurrence of an acoustic resonance phenomenon with a simple and inexpensive circuit configuration, and to keep flicker (light) while keeping the power supplied to the discharge lamp constant. It is possible to extend the life of the discharge lamp by suppressing the occurrence of output flicker) and suppressing electrode deterioration.

It is a circuit block diagram which shows the discharge lamp lighting device which concerns on 1st Embodiment of this invention. It is a flowchart figure which shows the flow of control operation of the switching frequency in 1st Embodiment of this invention. It is a figure which shows typically the output voltage waveform of the DC / DC converter circuit in the discharge lamp lighting device which concerns on 1st Embodiment of this invention. It is a figure which shows typically the lamp current waveform which flows into the discharge lamp of the discharge lamp lighting device which concerns on 1st Embodiment of this invention, (a) is a lamp current fluctuation by the influence of the acoustic resonance phenomenon before switching frequency switching. The generated lamp current waveform diagram, (b) is a lamp current waveform diagram when the influence of the acoustic resonance phenomenon after switching the switching frequency is avoided. It is a circuit block diagram which shows the discharge lamp lighting device which concerns on 2nd Embodiment of this invention. It is a circuit block diagram which shows the discharge lamp lighting device which concerns on 3rd Embodiment of this invention. It is a flowchart figure which shows the flow of control operation of the switching frequency in 3rd Embodiment of this invention. It is a circuit block diagram which shows the discharge lamp lighting device which concerns on 4th Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, the same components are denoted by the same reference numerals, and the description of the overlapping portions in the description of each embodiment is omitted as appropriate.

(First embodiment)
FIG. 1 is a circuit configuration diagram showing a discharge lamp lighting device according to a first embodiment of the present invention.

As shown in FIG. 1, a discharge lamp lighting device 1 according to a first embodiment of the present invention includes a DC / DC converter circuit 2 that steps down a DC voltage output from a DC power supply Vdc, and a DC / DC converter circuit 2. Control circuit (control means) having an inverter circuit (DC / AC inverter circuit) 3 for converting the output voltage into an AC voltage, and a PWM control circuit for controlling the switching frequency of the DC / DC converter circuit 2 and the lighting frequency of the inverter circuit 3 4, an output voltage detection circuit 5 that detects the output voltage, and an output current detection circuit 6 that detects the output current of the DC / DC converter circuit. The control circuit 4 is a DSP (Digital
(Signal Processor). In addition, a high voltage generation circuit 7 is connected to the output terminal of the inverter circuit 3, and an AC voltage is output from the inverter circuit 3 at a predetermined lighting cycle at the time of start-up, and a high voltage pulse is generated by the high voltage generation circuit 7, thereby discharging. The lamp 8 is turned on. The DC power supply Vdc is, for example, a DC voltage obtained by rectifying and smoothing a commercial AC power supply, and may be a boost chopper circuit (not shown) connected to the output of the full-wave rectifier circuit.

The DC / DC converter circuit 2 is a MOS
A switching element Q1 made of an FET and performing an on / off operation at a predetermined switching period, an inductor L1 having one end connected to the source terminal of the switching element Q1, and an anode terminal connected to the negative electrode of the DC power supply Vdc to the cathode terminal Includes a diode D1 connected to an intermediate point between the switching element Q1 and the inductor L1, and a capacitor C1 having one end connected to the negative electrode of the DC power supply Vdc and the other end connected to the other end of the inductor L1. The switching period in the present invention refers to the time from the rising edge at a certain point to the next rising edge in the output signal of the switching element Q1, or the time from the falling edge at a certain point to the next falling edge. .

The inverter circuit 3 is a MOS
A full bridge circuit is configured by switching elements Q2 to Q5 made of FETs. A series circuit of switching elements Q2 and Q3 and a series circuit of switching elements Q4 and Q5 are connected in parallel to both ends of the capacitor C1. Yes. A driving circuit 9 for outputting a drive signal to the switching elements Q2 to Q5 is connected to the gate terminals of the switching elements Q2 to Q5. The configuration of the inverter circuit 3 is not limited to a full bridge circuit, and may be, for example, a half bridge circuit.

  The control circuit 4 includes an inverter control unit 10 that outputs a control signal to the drive circuit 9 of the inverter circuit 3, and a power calculation circuit 11 that inputs an output signal from the output voltage detection circuit 5 and an output signal from the output current detection circuit 6. And a PWM control circuit 12 that controls the on / off operation of the switching element Q1 of the DC / DC converter circuit 2. Further, the control circuit 4 outputs a frequency switching signal that instructs the PWM control circuit 12 to switch the switching frequency to a switching frequency outside the acoustic resonance frequency region when the acoustic resonance phenomenon occurs. It has. Although details will be described later, the frequency switching determination processing circuit 13 includes a moving average calculation circuit 14, an offset circuit 15, a comparator 17, and a counter 18. Note that the control circuit 4 in this embodiment is all configured by a digital circuit unit (DSP).

  The output voltage detection circuit 5 includes resistance elements R1 and R2 connected in series between both the output terminal of the DC / DC converter circuit 2 and the input terminal of the inverter circuit 3, and the output current detection circuit 6 includes the DC / DC The detection resistor R3 is connected between the negative side of the converter circuit 2 and the negative side of the output voltage detection circuit 5.

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

The DC / DC converter circuit 2 receives PWM (Pulse) from the PWM control circuit 12 included in the control circuit 4.
In response to the (Width Modulation) control signal, a DC current of a predetermined magnitude is supplied to the inverter circuit 3. That is, at the time of stable lighting (at the time of steady lighting), it is necessary to control the lamp power to be constant in order to keep the light output from the discharge lamp 8 constant, but the control circuit 4 is the output current detection circuit 6 for that purpose. The output current detected by the detection resistor R3 and the output voltage detected by the output voltage detection circuit 5 are input to the power calculation circuit 11 to calculate the lamp power, and a PWM control signal for making it constant is supplied to the PWM control circuit 12. To the DC / DC converter circuit 2. In response to this, the DC / DC converter circuit 2 converts the DC voltage from the DC power supply Vdc into a DC current of a predetermined magnitude. By changing the on-duty (ratio of on-time occupying one period) of the switching element Q1 by the PWM control circuit 12, the voltage obtained in the capacitor C1 can be variably controlled. As described above, the DC / DC converter circuit 2 constitutes a step-down chopper circuit.

Further, as will be described later, when the fluctuation of the lamp current due to the acoustic resonance phenomenon occurs, the control circuit 4 determines whether or not the acoustic resonance phenomenon has occurred in the frequency switching determination processing circuit 13, and A PWM control signal for changing the switching frequency of the DC / DC converter circuit 2 by a predetermined frequency is sent to the switching element Q1 of the DC / DC converter circuit 2 so as to avoid the influence. The control circuit 4 sends a PWM control signal to the DC / DC converter circuit 2 so as to control with a constant output current until a constant lamp power is obtained (a predetermined output voltage is reached) from the start. .

  The inverter circuit 3 is configured to switch the switching elements Q2 and Q5 and the switching elements Q3 and Q4 based on a control signal having a predetermined lighting cycle from the inverter control unit 10 included in the control circuit 4 with respect to the direct current from the DC / DC converter circuit 2. Alternately repeat on / off operations to generate a rectangular wave current having a predetermined lighting frequency.

  The high voltage generation circuit 7 has, for example, a transformer (not shown), promotes dielectric breakdown between the electrodes of the discharge lamp 8, generates a high voltage to start the discharge lamp 8, and applies it to the discharge lamp 8. To do.

  Next, the operation of the frequency switching determination processing circuit 13 will be described in detail with reference to FIGS.

  FIG. 2 is a flowchart showing the flow of the switching frequency control operation of the discharge lamp lighting device 1 according to the first embodiment of the present invention, and FIG. 3 shows the output voltage waveform of the DC / DC converter circuit 2 in the discharge lamp lighting device 1 ( 4 is a diagram schematically showing a lamp current waveform flowing in the discharge lamp 8 of the discharge lamp lighting device 1, and FIG. 4A is a diagram showing acoustic resonance before switching frequency switching. FIG. 6B is a lamp current waveform diagram in which current fluctuation is caused by the influence of the phenomenon, and FIG. 5B is a lamp current waveform diagram when the influence of the acoustic resonance phenomenon after switching of the switching frequency is avoided.

(Flow of control operation)
The switching frequency control (current fluctuation detection) in the discharge lamp lighting device 1 is started after shifting to the constant power control mode after the discharge lamp 8 lighting command (step S1 in FIG. 2). In each lighting cycle, the following steps (S2 to S6) are executed. First, the detected value of the output voltage Vo is detected by the output voltage detection circuit 5 (step S2). Next, the detected value of the output voltage Vo is input to the control circuit 4, and the moving average calculation circuit 14 provided in the frequency switching determination processing circuit 13 is a predetermined number of consecutive times (for example, 30 times) for each switching period. A moving average value Vave is calculated based on the detected value (step S3). At the addition point 16, the offset value Voff output from the offset circuit 15 is added to or subtracted from the moving average value Vave, and the threshold voltage Vref having a threshold region centered on the moving average value Vave is obtained by the following equation (1). (A region of Voff1 to Voff2 shown in FIG. 3) is calculated (step S4).
Vref = Vave ± Voff (1)
Next, the detection values of the output voltage Vo newly detected after detection of the detection value for a predetermined number of times used for the threshold voltage Vref and the moving average value Vave are input to the two input terminals of the comparator 17, respectively. If the detected value newly deviates from the threshold region of the threshold voltage Vref, an output signal is sent from the output terminal of the comparator 17 to the counter 18 (step S5). The counter 18 counts the number of signals input from the comparator 17 (step S6). When the number of input signals to the counter 18 exceeds a predetermined number (for example, 20 times), a frequency switching signal is output to the PWM control circuit 12 for instructing switching of the switching frequency at the polarity switching timing of the next lighting cycle. (Step S7). When the frequency switching signal from the counter 18 is input, the PWM control circuit 12 outputs a PWM control signal with the PWM frequency changed at the polarity switching timing of the next lighting cycle (step S8), and the DC / DC converter circuit. The switching frequency of the second switching element Q1 is shifted by a predetermined frequency (for example, 1 kHz) (step S9).
Although not described in FIG. 2, after the number of signals input to the counter 18 exceeds a predetermined number in step S6, the operation from step S2 to S6 continues until the next lighting cycle switching timing. It may be executed repeatedly or may not be executed (waiting).

As described above, the frequency switching determination processing circuit 13 repeats the procedure from step S2 to step S9 shown in FIG. 2 for each switching period, determines whether or not current fluctuation occurs due to the acoustic resonance phenomenon, and performs acoustic resonance. If it is determined that the phenomenon has occurred, a frequency switching signal that instructs switching of the switching frequency by a predetermined frequency at the polarity switching timing of the next lighting cycle is output to the PWM control circuit 12.
As a result, the lamp current waveform that has fluttered due to the fluctuation of the current due to the influence of the acoustic resonance phenomenon shown in FIG. 4A is changed to a switching frequency obtained by shifting the switching frequency by a predetermined frequency at the polarity switching timing of the next lighting cycle. By switching, the switching frequency becomes a frequency at which the acoustic resonance phenomenon can be avoided. Therefore, as shown in FIG. 4B, the lamp current waveform becomes a voltage waveform without current fluctuation due to the acoustic resonance phenomenon. In FIG. 4B, the waveform portion that appears to be somewhat fluttered is due to the current ripple component.

  As the switching frequency of the switching element Q1 in the DC-DC converter circuit 2, an upper limit frequency and a lower limit frequency that can be switched are determined in advance. Therefore, the switching frequency switched by the instruction of the frequency switching determination processing circuit 13 is shifted within the range of the upper limit frequency and the lower limit frequency.

Although various modes can be considered as a switching method of the switching frequency that is switched at every timing of switching the polarity of the lighting cycle, for example, the following method is applicable.
(1) The switching frequency that can be switched is limited to only two switching frequencies, and a frequency switching signal instructing the switching frequency to be switched is output from the frequency switching determination processing circuit 13 to the PWM control circuit 12 during a certain lighting cycle. In this case, the switching frequency is alternately switched from one switching frequency to the other switching frequency at the polarity switching timing of the next lighting cycle.
(2) The switching frequency that can be switched has three or more frequencies, and the frequency switching signal that instructs the frequency switching determination processing circuit 13 to switch the switching frequency at the polarity switching timing of the next lighting cycle is a PWM control circuit. When output to 12, the switching frequency is sequentially switched from the original switching frequency to the higher or lower frequency at the polarity switching timing of the next lighting cycle. For example, when the original switching frequency is a frequency close to the upper limit frequency, the frequency is switched to a lower frequency at the polarity switching timing of the next lighting cycle.

  The switching methods shown above are merely examples, and are not limited to these, and each switching method can be arbitrarily designed according to circuit specifications.

  In addition, the detection accuracy of the detection value of the output voltage Vo input to the moving average arithmetic circuit 14 is increased as the number of times increases, but the processing time increases as the number of times increases. The optimal number of times is set.

  Further, the predetermined number of times set by the counter 18 may always be a constant value with respect to the switching frequency to be switched, but it is preferable to set a desired number of times for each switching frequency.

  The offset value output from the offset circuit 15 may always be a constant value with respect to the switching frequency to be switched. However, when the switching frequency changes, it is superimposed on the output voltage detected by the output voltage detection circuit 5. Since the magnitude of the ripple voltage also changes, it is desirable to set the offset value according to the switching frequency.

  The predetermined frequency changed at the polarity switching timing of the next lighting cycle is preferably at least about 1 kHz in order to avoid the acoustic resonance frequency band, but can be arbitrarily set by individual circuit design. Yes, it is not limited.

  As described above, in the discharge lamp lighting device 1 according to this embodiment, the control circuit 4 moves the detection value detected by the output voltage detection circuit 5 for a predetermined number of consecutive times for each switching cycle in each lighting cycle. A frequency switching signal that calculates an average value and instructs the switching frequency to be changed by a predetermined frequency at the polarity switching timing of the next lighting cycle based on the difference information between the moving average value and the newly detected value Is provided with a frequency switching determination processing circuit 13 that outputs to the PWM control circuit 12, so that the occurrence of the acoustic resonance phenomenon is accurately determined and switching is performed when the acoustic resonance phenomenon occurs even though the circuit configuration is simple and inexpensive. By switching the frequency to a frequency at which the acoustic resonance phenomenon can be avoided, the fluctuation of the lamp current is avoided while keeping the power supplied to the discharge lamp constant. It suppresses the generation of Tsu mosquitoes to realize an extended service life of the discharge lamp by suppressing the deterioration of the electrodes.

(Second Embodiment)
FIG. 5 is a diagram showing a circuit configuration of a discharge lamp lighting device 1a according to the second embodiment of the present invention. In FIG. 5, the same reference numerals are given to the same components as those in FIG. 1, and in the following description, the description of the parts overlapping with the above-described discharge lamp lighting device 1 is omitted.

  As shown in FIG. 5, the discharge lamp lighting device 1a is different from the discharge lamp lighting device 1, in the control circuit 4a, the moving average calculation circuit 14 of the frequency switching determination processing circuit 13a is connected to the output voltage detection circuit 5. The detection value is not input, but the detection value in the output current detection circuit 6 is input. Except for the above, the configuration is the same as that of the discharge lamp lighting device 1.

  In the discharge lamp lighting device 1a, in each lighting cycle, the output current detection circuit 6 detects the detected value of the output current of the DC / DC converter circuit (the value converted into the voltage value). The detected value of the output current is input to the control circuit 4a, and the detected value for a predetermined number of consecutive times (for example, 30 times) for each switching period is obtained by the moving average arithmetic circuit 14 provided in the frequency switching determination processing circuit 13a. And a moving average value is calculated. At the addition point 16, the offset value output from the offset circuit 15 is added to or subtracted from the moving average value to calculate a threshold voltage having a threshold region centered on the moving average value. Next, the comparator 17 compares the threshold voltage with the detection value of the output current newly detected after detection of the detection value for the predetermined number of times used for the moving average value, and the newly detected detection value is the threshold value. When the voltage is out of the threshold region, the output signal is sent to the counter 18. The counter 18 counts the number of signals input from the comparator 17 and switches the switching frequency at the polarity switching timing of the next lighting cycle when the number of inputs exceeds a predetermined number (for example, 20 times). The instructed frequency switching signal is output to the PWM control circuit 12. When the frequency switching signal from the counter 18 is input, the PWM control circuit 12 outputs a PWM control signal in which the PWM frequency is changed at the polarity switching timing of the next lighting cycle, and the switching element of the DC / DC converter circuit 2 The switching frequency of Q1 is shifted by a predetermined frequency (for example, 1 kHz).

  Also in the discharge lamp lighting device 1a configured as described above, the control circuit 4a has the moving average value for a predetermined number of consecutive times for each switching cycle of the detected value detected by the output current detection circuit 6 in each lighting cycle. Based on the difference information between the moving average value and the newly detected value, a frequency switching signal for instructing to change the switching frequency by a predetermined frequency at the polarity switching timing of the next lighting cycle is PWM Since the frequency switching determination processing circuit 13a that outputs to the control circuit 12 is provided, the acoustic resonance phenomenon is generated when the acoustic resonance phenomenon occurs even though the circuit configuration is simple and inexpensive like the discharge lamp lighting device 1. Flickering is avoided by avoiding lamp current fluctuations by switching the switching frequency to a frequency that can avoid the acoustic resonance phenomenon. In addition, the life of the discharge lamp can be extended by suppressing the deterioration of the electrode.

(Third embodiment)
FIG. 6 is a diagram showing a circuit configuration of a discharge lamp lighting device 1b according to the third embodiment of the present invention, and FIG. 7 is a flowchart showing a flow of a switching frequency control operation of the discharge lamp lighting device 1b. In FIG. 6, the same reference numerals are given to the same components as those in FIG. 1, and in the following description, description of portions overlapping with the above-described discharge lamp lighting device 1 is omitted.

  As shown in FIG. 6, in the discharge lamp lighting device 1b, in the control circuit 4b, the frequency switching determination processing circuit 13b is a component of the frequency switching determination processing circuit 13 of the discharge lamp lighting device 1 and the acoustic resonance phenomenon determination processing procedure. Is different. Except for the frequency switching determination processing circuit 13b, the configuration is the same as that of the discharge lamp lighting device 1.

The frequency switching determination processing circuit 13 b includes a moving average calculation circuit 14, a first comparator 19, a second comparator 20, and a counter 18.

(Flow of control operation)
Control of the switching frequency (current fluctuation detection) in the discharge lamp lighting device 1b is started after shifting to the constant power control mode after the discharge lamp 8 lighting command (step S11 in FIG. 7). In each lighting cycle, the following steps (S12 to S19) are executed. First, the detected value of the output voltage Vo is detected by the output voltage detection circuit 5 (step S12). Next, the detected value of the output voltage Vo is input to the control circuit 4, and the moving average calculation circuit 14 provided in the frequency switching determination processing circuit 13b is a predetermined number of consecutive times (for example, 30 times) for each switching period. A moving average value Vave is calculated based on the detected value (step S13). The two input terminals of the first comparator 19 have a moving average value Vave and detection values of the output voltage Vo newly detected after detection of the detection value for a predetermined number of times used for the moving average value Vave. And the difference voltage (absolute value) Vdif is calculated by the following equation (2) and output from the output terminal of the first comparator 19 (step S14).
Vdif = | Vave−Voff | (2)
Next, the differential voltage Vdif and the threshold voltage Vref are respectively input to the two input terminals of the second comparator 20, and when the differential voltage Vdif is out of the threshold region of the threshold voltage Vref, the second comparator 20 An output signal is sent from the 20 output terminals to the counter 18 (step S15). The counter 18 counts the number of signals input from the second comparator 20 (step S16). When the number of inputs to the counter 18 exceeds a predetermined number (for example, 20 times), a frequency switching signal for instructing switching of the switching frequency at the polarity switching timing of the next lighting cycle is output to the PWM control circuit 12 ( Step S17). When the frequency switching signal from the counter 18 is input, the PWM control circuit 12 outputs a PWM control signal in which the PWM frequency is changed at the polarity switching timing of the next lighting cycle (step S18), and the DC / DC converter circuit 2 The switching frequency of the switching element Q1 is shifted by a predetermined frequency (for example, 1 kHz) (step S19).

  As described above, the frequency switching determination processing circuit 13b repeats the procedure from step S12 to step S19 shown in FIG. 7 for each switching period, determines whether or not current fluctuation has occurred due to the acoustic resonance phenomenon, and performs acoustic resonance. If it is determined that the phenomenon has occurred, a frequency switching signal for instructing to switch the switching frequency at the next lighting cycle switching timing is output to the PWM control circuit 12.

  Also in the discharge lamp lighting device 1b configured as described above, the control circuit 4b has a moving average value for a predetermined number of consecutive times for each switching cycle of the detection value detected by the output voltage detection circuit 5 in each lighting cycle. Based on the difference information between the moving average value and the newly detected value, a frequency switching signal for instructing to change the switching frequency by a predetermined frequency at the polarity switching timing of the next lighting cycle is PWM Since the frequency switching determination processing circuit 13b for outputting to the control circuit 12 is provided, the acoustic resonance phenomenon is generated when the acoustic resonance phenomenon occurs even though the circuit configuration is simple and inexpensive like the discharge lamp lighting device 1. By accurately determining and switching the switching frequency to a frequency that can avoid the acoustic resonance phenomenon at the polarity switching timing of the next lighting cycle, Suppresses the generation of avoiding fluctuations in the flow flicker, it is possible to extend the life of the discharge lamp by suppressing the deterioration of the electrodes.

  Note that the value of the threshold voltage Vref input to the second comparator 20 may always be a constant value with respect to the switching frequency to be switched, but the output detected by the output voltage detection circuit 5 when the switching frequency changes. Since the magnitude of the ripple voltage superimposed on the voltage also changes, it is desirable to set the value of the threshold voltage Vref according to the switching frequency.

(Fourth embodiment)
FIG. 8 is a diagram showing a circuit configuration of a discharge lamp lighting device 1c according to the fourth embodiment of the present invention. In FIG. 8, the same components as those in FIG. 1 are denoted by the same reference numerals, and in the following description, description of portions overlapping with the above-described discharge lamp lighting device 1 is omitted.

  As shown in FIG. 8, in the discharge lamp lighting device 1c, the control circuit 4c is configured by a digital control unit 21 and an analog arithmetic circuit 14a configured by an analog circuit. The digital control unit 21 includes an inverter control unit 10, a power calculation circuit 11, a PWM control circuit 12, and a frequency switching determination processing circuit 13c. The frequency switching determination processing circuit 13 c includes an offset circuit 15, a comparator 17, and a counter 18. The analog arithmetic circuit 14a includes a resistance element R4 and a capacitor C2 connected in series between the output terminal of the output voltage detection circuit 5 and the ground. The configuration is the same as that of the discharge lamp lighting device 1 except for the configuration of the control circuit 4c.

In the discharge lamp lighting device 1c, the following lighting control operation is performed in each lighting cycle.
The detection value of the output voltage Vo detected by the output voltage detection circuit 5 is input to the control circuit 4c, and the average value Vave of the detection values is calculated by the analog arithmetic circuit 14a. Then, the average value Vave calculated by the analog arithmetic circuit 14 a is input to the addition point 16 of the frequency switching determination processing circuit 13 c provided in the digital control unit 21. The offset value Voff output from the offset circuit 15 is added to or subtracted from the average value Vave to calculate a threshold voltage Vref having a threshold region centered on the average value Vave.
Next, the detection values of the output voltage Vo newly detected after the calculation of the threshold voltage Vref and the average value Vave are respectively input to the two input terminals of the comparator 17, and the newly detected value is the threshold voltage Vref. If it is outside the threshold region, an output signal is sent from the output terminal of the comparator 17 to the counter 18. The counter 18 counts the number of signals input from the comparator 17 and instructs the switching frequency to be switched at the next lighting cycle switching timing when the number of inputs exceeds a predetermined number (for example, 20 times). The frequency switching signal to be output is output to the PWM control circuit 12. When the frequency switching signal from the counter 18 is input, the PWM control circuit 12 outputs a PWM control signal in which the PWM frequency is changed at the polarity switching timing of the next lighting cycle, and the switching element of the DC / DC converter circuit 2 The switching frequency of Q1 is shifted by a predetermined frequency (for example, 1 kHz).

  Also in the discharge lamp lighting device 1c configured as described above, the control circuit 4c calculates an average value of detection values detected by the output voltage detection circuit 5 in each lighting cycle by the analog arithmetic circuit 14a, and this average value. And a frequency switching signal for instructing the PWM control circuit 12 to change the switching frequency by a predetermined frequency at the polarity switching timing of the next lighting cycle based on the difference information from the newly detected value. Since the switching determination processing circuit 13c is provided, as in the case of the discharge lamp lighting devices 1, 1a, 1b according to the first to third embodiments, the acoustic resonance phenomenon occurs when the circuit configuration is simple and inexpensive. The occurrence of the acoustic resonance phenomenon is accurately determined, and the switching frequency is switched to a frequency at which the acoustic resonance phenomenon can be avoided at the polarity switching timing of the next lighting cycle. And allows to avoid the fluctuation of the lamp current is suppressed flickering, it is possible to extend the life of the discharge lamp by suppressing the deterioration of the electrodes.

  The representative embodiment of the present invention has been described above, but the present invention is not limited to the circuit configuration of the above embodiment, and various modifications can be made without departing from the spirit of the present invention. .

  For example, in the above first to third embodiments, the detection value used for the moving average in the moving average arithmetic circuit is not limited to a value corresponding to a predetermined number of consecutive times for each switching cycle. Among these detection values, a value for a predetermined number of times with a predetermined interval, or a value for a predetermined number of detection values detected at an interval other than every switching period may be used.

  Further, the predetermined number of detection values used for moving average in the moving average arithmetic circuit, the predetermined number of times set by the counter, and the predetermined frequency of the shifted switching frequency set by the PWM control circuit are as described in the above embodiment. It is not limited to the specific examples shown in the above, but is appropriately determined according to the circuit specifications and the like.

  Further, in the third and fourth embodiments, a configuration in which the detection value input to the moving average calculation circuit is replaced with the detection value of the output current detection circuit from the detection value of the output voltage detection circuit is possible.

  In the above embodiment, the DC / DC converter circuit is a step-down chopper circuit that steps down the DC voltage output from the DC power supply Vdc, but may be a step-up chopper circuit or a step-up / step-down chopper circuit.

  In the above embodiment, the control circuit is a DSP. However, the present invention is not limited to this, and a programmable device such as an FPGA or a microcomputer can be used.

1, 1a, 1b, 1c: discharge lamp lighting device, 2: DC / DC converter circuit, 3: inverter circuit (DC / AC inverter circuit), 4, 4a, 4b, 4c: control circuit, 5: output voltage detection circuit , 6: output current detection circuit, 7: high voltage generation circuit, 8: discharge lamp, 9: drive circuit, 10: inverter control unit, 11: power calculation circuit, 12: PWM control circuit, 13, 13a, 13b, 13c: Frequency switching determination processing circuit, 14: moving average arithmetic circuit, 14a: analog arithmetic circuit, 15: offset circuit, 16: addition point, 17: comparator, 18: counter, 19: first comparator, 20: second comparator , 21: digital control unit, D1: diode, L1: inductor, C1, C2: capacitor, R1, R2, R4: resistance element, R3: detection resistor, Q1 to Q 5: switching element, Vdc: DC power supply, Vref: threshold voltage

Claims (13)

DC / DC converter circuit for boosting and / or stepping down DC voltage, inverter circuit for converting output voltage of DC / DC converter circuit to AC voltage, switching frequency of DC / DC converter circuit and lighting of inverter circuit A digital control means having a PWM control circuit for controlling the frequency, and at least one of an output voltage detection circuit for detecting the output voltage and an output current detection circuit for detecting an output current of the DC / DC converter circuit; A discharge lamp lighting device for lighting the discharge lamp by supplying the AC voltage to the discharge lamp at a predetermined lighting cycle from the inverter circuit,
The control means calculates a moving average value for a predetermined number of detection values detected by the output voltage detection circuit or the output current detection circuit in the lighting cycle, and newly detects the moving average value. A frequency switching determination processing circuit for outputting to the PWM control circuit a frequency switching signal for instructing to change the switching frequency by a predetermined frequency at the polarity switching timing of the next lighting cycle based on the difference information from the value A discharge lamp lighting device characterized by that.   The switching frequency has an upper limit value and a lower limit value of the switchable frequency, and the switching frequency changed by the predetermined frequency is the upper limit value and the lower limit value according to the value of the switching frequency before the change. 2. The discharge lamp lighting device according to claim 1, wherein the frequency changing direction and the changing amount are determined within a range. The frequency switching determination processing circuit includes a moving average arithmetic circuit that calculates the moving average value, an offset circuit that outputs a predetermined offset value, and a threshold value obtained by adding and subtracting the predetermined offset value to the moving average value A comparator that sends an output signal when the newly detected value deviates from the threshold region by comparing the region and the newly detected value, and the number of inputs to which the output signal is input The discharge lamp lighting device according to claim 1, further comprising: a counter that outputs the frequency switching signal to the PWM control circuit when the number of times exceeds a predetermined number. The frequency switching determination processing circuit inputs a moving average calculation circuit that calculates the moving average value, and outputs the absolute value of the differential voltage by inputting the moving average value and the newly detected value. A comparator, a second comparator for transmitting an output signal when the absolute value of the differential voltage exceeds a predetermined threshold, and the frequency switching signal when the output signal is input and the number of inputs exceeds a predetermined number of times. The discharge lamp lighting device according to claim 1, further comprising: a counter that outputs to the PWM control circuit. A DC / DC converter circuit that boosts or reduces a DC voltage, an inverter circuit that converts an output voltage of the DC / DC converter circuit into an AC voltage, a switching frequency of the DC / DC converter circuit, and a lighting frequency of the inverter circuit A control means having a PWM control circuit for controlling, and at least one of an output voltage detection circuit for detecting the output voltage and an output current detection circuit for detecting an output current of the DC / DC converter circuit, and the inverter circuit In a discharge lamp lighting device for lighting the discharge lamp by supplying the alternating voltage to the discharge lamp at a predetermined lighting cycle,
The control means is configured to calculate an average value of detection values detected by the output voltage detection circuit or the output current detection circuit in the lighting cycle, and input the average value signal from the analog calculation circuit Based on the difference information between the average value and the newly detected value, a frequency switching signal for instructing to change the switching frequency by a predetermined frequency at the polarity switching timing of the next lighting cycle A discharge lamp lighting device comprising a frequency switching determination processing circuit for outputting to a control circuit. DC / DC converter circuit for boosting and / or stepping down DC voltage, inverter circuit for converting output voltage of DC / DC converter circuit to AC voltage, switching frequency of DC / DC converter circuit and lighting of inverter circuit A digital control means having a PWM control circuit for controlling the frequency, and at least one of an output voltage detection circuit for detecting the output voltage and an output current detection circuit for detecting an output current of the DC / DC converter circuit; A discharge lamp lighting device lighting control method for lighting the discharge lamp by supplying the AC voltage to the discharge lamp at a predetermined lighting cycle from the inverter circuit,
A detection step of detecting the output voltage or the output current by the output voltage detection circuit or the output current detection circuit; a moving average value calculating step of calculating a moving average value for a predetermined number of detection values; and the moving average value A comparison step of sending an output signal based on difference information between the detected value and a newly detected value, and at the polarity switching timing of the next lighting cycle when the output signal is inputted and the number of inputs exceeds a predetermined number A counting step for outputting a frequency switching signal for instructing to change the switching frequency by a predetermined frequency to the PWM control circuit, and an oscillation frequency based on the frequency switching signal at the polarity switching timing of the next lighting cycle. Based on the PWM frequency changing step to be changed and the oscillation frequency changed at the polarity switching timing of the next lighting cycle Lighting control method of a discharge lamp lighting device characterized by comprising a switching frequency switching step of switching the switching frequency for each of the lighting cycle.   7. The discharge lamp lighting device according to claim 6, wherein in the comparison step, a threshold value region obtained by adding / subtracting a predetermined offset value to / from the moving average value is compared with the newly detected value. Lighting control method.   The lighting control method for a discharge lamp lighting device according to claim 7, wherein the offset value set in the comparison step is different for each switching frequency.   The lighting control of the discharge lamp lighting device according to claim 6, wherein in the comparison step, an absolute value of a differential voltage between the moving average value and the newly detected value is compared with a predetermined threshold value. Method.   10. The lighting control method for a discharge lamp lighting device according to claim 9, wherein the predetermined threshold set in the comparison step is different for each switching frequency.   The switching frequency to be switched at each polarity switching timing of the next lighting cycle has an upper limit value and a lower limit value of the switchable frequency, and the upper limit value and the lower limit value according to the value of the switching frequency before the change. 11. The lighting control method for a discharge lamp lighting device according to claim 6, wherein the frequency changing direction and the changing amount are determined within a range of the above.   The switching frequency to be switched at each polarity switching timing of the next lighting cycle is such that the first switching frequency and the second switching frequency are alternately switched. Lighting control method for a discharge lamp lighting device. 13. The lighting control method for a discharge lamp lighting device according to any one of claims 6 to 12, wherein the predetermined number of times set in the counting step is different for each switching frequency.

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