JP2009123409A - High-pressure discharge lamp lighting device, and illumination device using this - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a high voltage discharge lamp lighting device capable of realizing cost reduction using a commercial alternate current power supply and standardization of equipment specifications since noise regulation is not exceeded by evading occurrence of an acoustic resonance phenomenon by using characteristics of a high voltage discharge lamp having downsizing, high brightness, and high efficiency. <P>SOLUTION: This is equipped with a converter 1 to convert an alternate current voltage of the commercial alternate current power supply 10 into a fixed direct current voltage, a half bridge inverter 2 to convert its direct current voltage into the alternate current voltage of variable frequencies, and a resonance circuit 3 including the high voltage discharge lamp 4. Output frequency is set between the lower limit value of the frequency in which the acoustic resonance phenomenon does not occur, and the higher limit value of the frequency in which the noise regulation caused by an electric current flow-out into the commercial alternate current power supply 10 does not exist, and duty ratio is controlled within a prescribed range so that harmonic components of an output of the half bridge inverter 2 do not exceed the noise regulation. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a lighting device for a high-pressure discharge lamp such as a metal halide lamp or a high-pressure mercury lamp, and an illumination device using the same.

  A high-pressure discharge lamp is a light source for illumination that is small, high-intensity, and high-efficiency. However, since a well-known acoustic resonance phenomenon occurs when this high-pressure discharge lamp is lit with a sinusoidal voltage having a frequency of several tens of kHz, This causes bending, rotation, and fluctuations, resulting in flickering of the light, and sometimes the lamp is damaged. For this reason, generally, a high-pressure discharge lamp is lit by applying a rectangular wave voltage of about several hundred Hz. Since it is necessary to apply such a low-frequency rectangular wave voltage, it is difficult to realize a lighting device that drives a high-pressure discharge lamp in a small size and at low cost.

  However, it is known that this acoustic resonance phenomenon does not occur when lighting is performed with a high-frequency sine wave voltage of several hundred kHz. For example, in Patent Document 1, a high-pressure discharge lamp is connected by connecting a resonance circuit including a high-pressure discharge lamp, an inductor, and a capacitor to an AC output terminal of a half-bridge inverter, and a high-frequency voltage of about 500 kHz is output from the half-bridge inverter. A lighting device is introduced.

JP-T-2004-538612

As described above, by driving the high pressure discharge lamp lighting device with a high frequency voltage of about several hundred kHz instead of a low frequency, it is possible to avoid the occurrence of an acoustic resonance phenomenon and to reduce the size of the lighting device. By combining the original features of the lamp, such as small size, high brightness, and high efficiency, it is expected to be widely applied to lighting equipment such as commercial facilities and large facilities.
In pursuit of such versatility, it is desirable in terms of cost to use a commercial AC power source that can easily obtain power from an outlet. In addition, since the DC voltage on the input side of the half-bridge inverter is applied as it is to the resonant circuit consisting of the high-pressure discharge lamp, inductor, and capacitor on the output side, the input of the inverter is taken into consideration when standardizing the equipment specifications. It is desirable in terms of cost to set the voltage to a constant DC voltage.

However, when a commercial AC power source is used as a power source and the input DC voltage of the inverter is set to a constant value, the following problems occur.
That is, the inverter generally becomes a source of distortion wave current due to the on / off operation of the switching element. Therefore, this distorted wave current flows out to the commercial AC power source connected to the lighting device. In this case, there is almost no problem when the output frequency of the inverter corresponding to the frequency of the distorted wave current is relatively low, but in this type of device, as described above, it is considerably high in order to avoid the occurrence of the acoustic resonance phenomenon. It is necessary to set the frequency, and the flowing out current may exceed the noise regulation level set in the commercial AC power supply system.

  As noise regulations, for example, there are standards in Japan based on the Electrical Appliance and Material Safety Law, and internationally, CISPR15 “Permissible Values and Measurement Methods for Radio Interference Characteristics of Electric Lighting and Similar Devices”. In the Electrical Appliance and Material Safety Law, a noise terminal voltage of 526.5 kHz or higher is standardized, and in CISPR15, a low level is standardized particularly at 500 kHz or higher. Therefore, the high-pressure discharge lamp lighting device needs to satisfy these standards. Whether the lighting frequency is 500 kHz or less or 526.5 kHz or less is based on a standard that matches the region where the high-pressure discharge lamp lighting device is used.

  Further, when the high-pressure discharge lamp enters the lighting operation, the inverter controls the power supplied to the high-pressure discharge lamp according to the operating condition. However, since the input DC voltage of the inverter is set to a constant value, the effective value of the output voltage is adjusted by controlling a so-called duty ratio (Duty ratio) based on on / off of the switching element. In this case, depending on the value of the duty ratio, a new harmonic, that is, a harmonic having a frequency that is an integral multiple of the output frequency of the inverter, is generated. Even if it is set to a frequency that is not related to the above, there is a possibility that the noise regulation level is exceeded due to the harmonic component.

  The inventors of the present application described above in the case where wide application to lighting devices such as commercial facilities and large facilities is intended for high-pressure discharge lamp lighting devices that avoid the occurrence of an acoustic resonance phenomenon and are driven at a relatively high frequency, as described above. It has been newly found that there are problems specific to noise regulation, but it has also been found that none of the conventional high-pressure discharge lamp lighting devices can solve these problems.

  The present invention solves the above-mentioned problems that have not been solved so far, and can take advantage of the features of high-pressure discharge lamps such as small size, high brightness, and high efficiency to avoid the occurrence of acoustic resonance and to exceed noise regulations. An object of the present invention is to obtain a high-pressure discharge lamp lighting device that can realize a reduction in the cost of the lighting device by using a commercial AC power source and standardizing the equipment specifications.

The high-pressure discharge lamp lighting device according to the present invention comprises a converter connected to a commercial AC power source and converts the AC voltage of the commercial AC power source into a predetermined constant DC voltage, and converts the DC voltage of the converter into an AC voltage of variable frequency. The half-bridge inverter is connected to the AC output terminal of this half-bridge inverter, and the high-pressure discharge lamp resonates at a predetermined frequency. The inductor and capacitor and the switching element of the half-bridge inverter resonate. High-voltage discharge lamp lighting with a control circuit that controls the duty ratio of the half-bridge inverter so that the high-voltage discharge lamp in the circuit is applied with a high voltage to start discharge and the power of the high-pressure discharge lamp during discharge is maintained at a predetermined value. In the device
When the lower limit value of the frequency at which the acoustic resonance phenomenon does not occur in the high pressure discharge lamp is the first frequency, and the upper limit value of the frequency at which noise regulation due to current outflow to the commercial AC power supply does not exist, the second frequency,
The control circuit sets the output frequency of the half bridge inverter between the first frequency and the second frequency, and the duty of the half bridge inverter so that the harmonic component of the output of the half bridge inverter does not exceed the noise regulation. The ratio is controlled within a predetermined range.

  An illumination device according to the present invention includes the above-described high-pressure discharge lamp lighting device and the high-pressure discharge lamp that is turned on by the high-pressure discharge lamp lighting device.

As described above, the control circuit of the high pressure discharge lamp lighting device according to the present invention uses the first frequency which is the lower limit value of the frequency at which the acoustic resonance phenomenon does not occur in the high pressure discharge lamp, as the output frequency of the half bridge inverter, Since it is set between the second frequency, which is the upper limit of the frequency at which noise regulation due to current outflow to the commercial AC power supply does not exist, the acoustic resonance phenomenon does not occur, of course, from the half-bridge inverter to the commercial AC power supply. The fundamental wave component of the outflowed current is not related to noise regulation. Furthermore, since the duty ratio of the half-bridge inverter is controlled within a predetermined range, the harmonic component of the outflow current does not exceed the noise regulation.
Therefore, taking advantage of the features of high-pressure discharge lamps such as small size, high brightness, and high efficiency, it is possible to reduce the cost of lighting devices by using a commercial AC power source and standardizing equipment specifications. Can be easily applied in a wide range.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a circuit configuration of a high-pressure discharge lamp lighting device according to Embodiment 1 of the present invention. Converter 1 converts the AC voltage from commercial AC power supply 10 into a constant DC voltage. This constant DC voltage is supplied to a half-bridge inverter 2 composed of two switching elements such as MOS-FETs, and is converted into a variable frequency AC voltage. A resonance circuit 3 including a high-pressure discharge lamp 4, an inductor L1, a first capacitor C1, and a second capacitor C2 is connected to the AC output terminal of the half-bridge inverter 2. In the resonance circuit 3, an inductor L1 and a second capacitor C2 are connected in series to the AC output terminal of the half-bridge inverter 2, and the first capacitor C1 and the high-pressure discharge lamp are connected between the terminals of the second capacitor C2. 4 are connected in series.

The converter 1 also rectifies the AC voltage from the commercial AC power supply 10 and converts it to a DC voltage, and boosts the output voltage from the AC / DC converter 5 to convert it to a predetermined constant DC voltage. And a smoothing capacitor C3 connected to the output terminal of the boost chopper 6, and a filter 7 for cutting noise generated in the high pressure discharge lamp lighting device.
The converter 1 is based on a power supply voltage-free design so that it can be commonly used in a plurality of types of commercial AC power supplies having different voltages around the world, and is 100 to 240 V ± 20% (80 V to 288 V). A predetermined constant DC voltage, for example, 415 V is output in response to the commercial AC voltage input. The voltage value of the DC voltage is 240V + 20%, which is the maximum value, that is, the peak value of the 288V sine wave voltage is 407V, so that the voltage value is set to 415V, for example.

  The input DC voltage of the half-bridge inverter 2 is set to 415 V based on the highest voltage value among a plurality of types of commercial AC power supplies 10 that can be used, and becomes a relatively high value, but a general-purpose high-pressure discharge lamp 4 is used. There is no particular obstacle to this, and there is an advantage that it can be realized by the boost chopper 6 which is generally less expensive than the step-up / step-down chopper. Further, by setting the DC voltage to a constant value regardless of the type of the commercial AC power supply 10, the withstand voltage specifications of the components of the resonance circuit 3 to which the voltage is applied can be made uniform, which is advantageous in terms of cost. Become.

  The two switching elements of the half-bridge inverter 2 are on / off controlled by the voltage or current from the driver circuit 8. A rectangular wave voltage is output from the output terminal of the half-bridge inverter 2 by alternately turning on and off the two switching elements. The driver circuit 8 is connected to the control circuit 9 and outputs a voltage or current for controlling the switching element based on a signal from the control circuit 9.

  A capacitor C4 for detecting the lamp voltage is connected to the high voltage side of the high pressure discharge lamp 4, and a current transformer CT for detecting the lamp current is connected to the low voltage side. The capacitor C4 has a sufficiently small capacitance and a large impedance compared to the capacitors C1 and C2, and therefore can be substantially ignored in the operation of lighting the high-pressure discharge lamp 4. In addition, since the current transformer CT has a sufficiently small inductance and a small impedance, it can be substantially ignored in the operation of lighting the high-pressure discharge lamp 4. A resistor R is connected to the secondary winding of the current transformer CT, and the detected magnitude of the lamp current is converted into a voltage. Information on the lamp voltage and lamp current detected by the capacitor C4 and the current transformer CT is sent to the control circuit 9, and the control circuit 9 controls the operation of the half-bridge inverter 2 based on this information.

  Next, the operation of the high pressure discharge lamp lighting device of the present invention will be described. As a suitable example, it shows with the specific characteristic value of each circuit element. The inductor L1 is an inductor having an inductance of 60 μH manufactured using a ferrite core, the first capacitor C1 is a chip multilayer ceramic capacitor having a DC withstand voltage of 630 V and a capacitance of 2200 pF, and the second capacitor C2 has a DC withstand voltage of 10 kV. Two high voltage ceramic capacitors 1000 pF were used in parallel to make 2000 pF. The resonance frequency f1 before the high pressure discharge lamp is turned on is

Therefore, f1 = about 459 kHz.
When an AC voltage is input from the commercial AC power supply 10 to the high-pressure discharge lamp lighting device, a DC voltage of 415 V is applied to the half-bridge inverter 2 by the converter 1. Although not shown, a control DC voltage such as 5 V or 15 V is simultaneously generated from the commercial AC voltage, and necessary power is supplied to the control circuit 9 and the driver circuit 8.

  The control circuit 9 starts operation when electric power is supplied, and performs a sequence for starting the high-pressure discharge lamp 4. That is, a signal is sent to the driver circuit 8 so that a rectangular wave having a frequency slightly higher than the resonance frequency before lighting is output from the half-bridge inverter 2, and the driver circuit 8 drives the half-bridge inverter 2. At this time, the maximum value of the rectangular wave voltage output from the half-bridge inverter 2 is 415 V, which is the same as the output of the converter 1. Further, it is desirable that the duty ratio of the rectangular wave voltage is approximately 50%. The duty ratio controlled by the control circuit 9 will be described in detail later.

  A sinusoidal current flows through the inductor L1 and the second capacitor C2, and a sinusoidal voltage is applied to both ends of the second capacitor C2. This voltage is also applied to the first capacitor C1 and the high-pressure discharge lamp 4, but the impedance of the high-pressure discharge lamp 4 at the time of extinction (before lighting) is sufficiently large, and the capacitance is much higher than that of the first capacitor C1. Since the voltage is small, a voltage substantially the same as the voltage generated at both ends of the second capacitor C2 is applied to the high-pressure discharge lamp 4. The frequency of the output rectangular wave voltage of the half-bridge inverter 2 is swept gradually from 500 kHz to 495 kHz, 490 kHz, 485 kHz, 480 kHz. However, the lower limit for sweeping the frequency is the resonance frequency f1 before lighting, and it is desirable to stop the sweep at a frequency slightly higher than the resonance frequency f1. Note that the frequency sweep may be performed by continuously changing the frequency, or may be performed discretely as in the above example.

  Here, the reason why the output frequency of the half-bridge inverter 2 is set to a frequency range higher than the resonance frequency f1 is to prevent the current flowing in the switching element from being in a slow phase and destroying the switching element.

As the output frequency sweeps toward the resonance frequency f1 before lighting, a high voltage is generated across the second capacitor C2. When a voltage substantially equal to the high voltage is applied to the high-pressure discharge lamp 4 and the voltage becomes equal to or higher than the discharge start voltage of the high-pressure discharge lamp 4, the high-pressure discharge lamp 4 starts to discharge and lights up. The discharge start voltage of the high pressure discharge lamp is about 1 to 3 kV, and such a high voltage is generated at both ends of the second capacitor C <b> 2 and applied to the high pressure discharge lamp 4.
As described above, since a high voltage is applied to the second capacitor C2, a capacitor having a high withstand voltage is required. In general, the AC withstand voltage of a ceramic capacitor becomes lower as the frequency becomes higher. Less than half of the withstand voltage. The cause of this is thought to be due to the dielectric loss tangent of the capacitor, the floating resistive component, and the inductive component, and is largely due to the structure of the capacitor element. In addition, a decrease in withstand voltage at high frequencies becomes more significant as the capacitance increases. This is also considered to be caused by the shape of the capacitor element.
On the other hand, since almost no voltage is applied to the first capacitor C1, the first capacitor C1 is a type that is formed on the surface of the substrate, and is a small chip capacitor that is inferior in withstand voltage characteristics between terminals. Can be used.

For the above reasons, in the first embodiment, the first capacitor C1 to which a high voltage is not applied is a small and large-capacity chip multilayer ceramic capacitor that has a low withstand voltage between terminals, and a high voltage is applied. As the second capacitor C2, two high-voltage ceramic capacitors are used in parallel, and the withstand voltage characteristics are secured by reducing the capacitance per capacitor.
With the above configuration, sufficient withstand voltage characteristics can be obtained without increasing the size of the circuit board of the apparatus.

  When the high-pressure discharge lamp 4 starts to discharge and lights up, a current also flows through the first capacitor C1. The resonant frequency f2 of the circuit at this time is not strict, but roughly

It is represented by Under the above-mentioned preferable conditions, f2 = about 317 kHz.
When the high-pressure discharge lamp 4 is lit, the control circuit 9 performs power control in order to light the high-pressure discharge lamp 4 with rated power. The power control of the high-pressure discharge lamp 4 may be performed by controlling the duty ratio of the rectangular wave voltage output from the half-bridge inverter 2 or by controlling the frequency. Naturally, both the frequency and the duty ratio may be controlled.

Here, the frequency of the voltage output from the half-bridge inverter 2 is set within the following range. That is, first, it is necessary to set the frequency higher than the lower limit value (first frequency) at which the acoustic resonance phenomenon does not occur so that the high-pressure discharge lamp 4 is not damaged by the acoustic resonance phenomenon. Note that, as will be exemplified later, this lower limit value varies depending on the type and capacity of the high-pressure discharge lamp 4.
Then, from the viewpoint of noise regulation that needs to be considered since this lighting device is connected to the commercial AC power supply 10, an upper limit value (second frequency) of the frequency at which this noise regulation does not exist, for example, as described above The output frequency is set to 526.5 or 500 kHz or less. In FIG. 1, a filter 7 for suppressing noise flowing from the lighting device to the commercial AC power supply 10 is provided. However, the noise suppression effect is practically limited in terms of cost and size. Therefore, it is necessary to manage the noise generation amount in the half-bridge inverter 2 that is a noise generation source.

As described above, the power control of the high-pressure discharge lamp 4 can be performed by controlling the duty ratio and / or the frequency of the rectangular wave voltage output from the half-bridge inverter 2. Since it is limited to a predetermined range in terms of acoustic resonance phenomenon and noise regulation, control by the duty ratio is also required. In this case, depending on the value of the duty ratio to be controlled, harmonics are generated, and even if the fundamental frequency output from the half-bridge inverter 2 is set to a frequency that is not related to noise regulation, the harmonic component is noise. There is a possibility of exceeding the level of regulation.
Thus, hereinafter, the generation state of harmonics when the duty ratio is changed will be described.

  FIG. 2 defines the duty ratio when the output voltage waveform of the half-bridge inverter 2 is regarded as a complete rectangular waveform. FIG. 3 shows the relationship between the duty ratio and the harmonic component by Fourier transforming the rectangular waveform of FIG. As can be seen from the figure, the second harmonic is the main component as the harmonic, but in the actual circuit, the inductor L1 and the capacitors C1 and C2 constituting the resonance circuit 3 function as a filter, and these harmonic components. Is smaller than the calculated value of FIG.

FIG. 4 and FIG. 5 show the frequency spectrum of the voltage of the half-bridge inverter 2, the current waveform actual measurement value, and the noise terminal voltage measurement result of the high-pressure discharge lamp lighting device, respectively. All of these are measurement results for (a) when the duty ratio is small and when the duty ratio is large and is approximately 50%. It can be seen that the harmonics, particularly the second harmonics tend to increase as the duty ratio decreases.
Therefore, even if the output frequency (fundamental wave frequency) of the half-bridge inverter 2 is set to a frequency between the first frequency and the second frequency described above due to the acoustic resonance phenomenon and the restriction of noise regulation, For example, the frequency of the second harmonic corresponds to a band related to noise regulation, and may exceed the noise regulation value depending on the magnitude of the harmonic component at that time. In this case, in consideration of the characteristics shown in FIGS. 3 and 5, the duty ratio to be controlled is limited to a range from a predetermined value to 50%, so that noise regulation can be prevented.

Next, frequency setting and duty ratio control procedures will be described based on the results of actual measurement by the inventors of a high-pressure discharge lamp having an assumed capacity.
In the case of a 100 W high-pressure discharge lamp, the disappearance of the acoustic resonance phenomenon was confirmed at about 350 kHz, although there were some differences depending on the manufacturer and type. In consideration of individual differences, changes in characteristics of high-pressure discharge lamps due to long-time lighting, environmental changes, and the like, it is desirable for 100 W high-pressure discharge lamps to light at 400 kHz or higher, and in consideration of noise regulation, 500 kHz It is desirable to light up in the following. When the lighting frequency was 450 kHz, the power of the high-pressure discharge lamp could be 100 W with a duty ratio of 34%.
When the duty ratio was 50%, about 130 W of power was input to the high pressure discharge lamp at 450 kHz. The electric power described here is electric power when the high-pressure discharge lamp is sufficiently stabilized after lighting, and is a process in which the gas pressure inside the high-pressure discharge lamp is increased for about 3 minutes immediately after starting. Therefore, excessive current flows if the power is forced to match the rated power, and the circuit of the high pressure discharge lamp lighting device may be damaged.

  On the other hand, when the duty ratio was fixed to 50% and the power was controlled by the frequency, 100 W could be input to the high pressure discharge lamp at 470 kHz. In this way, with the high pressure discharge lamp lighting device of the present invention, the resonant frequency after lighting can be made sufficiently low, so the power of the high pressure discharge lamp is lit at a desired frequency and controlled to the rated power. Also, a high duty ratio can be maintained. A high duty ratio at the time of lighting is very important in a high-pressure discharge lamp lighting device that lights at such a high frequency. That is, as the duty ratio is decreased, the second harmonic component increases. Since the frequency of the secondary harmonic component is twice that of the fundamental wave, if the frequency of the fundamental wave, that is, the rectangular wave voltage output from the half-bridge inverter 2 is, for example, 250 kHz to 526.5 kHz, the secondary harmonic is 500 kHz to 1053 kHz. This frequency range is a frequency range where a low noise terminal voltage is required as a standard in the Electrical Appliance and Material Safety Law and CISPR15. Therefore, when the second-order harmonic component becomes large, the filter must be made to have a high performance, and it is inevitable that the cost is increased or the circuit board is enlarged. However, in the high-pressure discharge lamp lighting device of the present invention, the duty ratio is set to a predetermined high range, so that it was possible to satisfy the Electrical Appliance and Material Safety Law and CISPR15 noise regulations without using a special high-performance filter. .

In the above description, the power of the high pressure discharge lamp is 100 W, but the power of the high pressure discharge lamp is not limited to this. When the rated power of the high-pressure discharge lamp was 150 W, the disappearance of the acoustic resonance phenomenon was confirmed at about 300 kHz or more. When the rated power was 200 W, the disappearance of the acoustic resonance phenomenon was confirmed at about 250 kHz. When the rated power was 300 W, the disappearance of the acoustic resonance phenomenon was confirmed at about 200 kHz.
However, if the frequency at which the high-pressure discharge lamp is lit is 200 kHz, the second harmonic is 400 kHz, so that the upper limit value (second frequency) of the frequency where no noise restriction exists is 500 or 526. In the case of 5 kHz, the present invention does not have to be close to the present invention, but when the disappearance of the acoustic resonance phenomenon is 250 kHz or more as confirmed when the rated power is 200 W, the second harmonic is 500 kHz or more. Therefore, the present invention is effective to satisfy the noise regulation.

  When the rated power of the high-pressure discharge lamp is 70 W, the disappearance of the acoustic resonance phenomenon was confirmed at about 400 kHz. However, when the rated power was 30 W, the disappearance of the acoustic resonance phenomenon was not confirmed even at 500 kHz. . Therefore, when the upper limit (second frequency) of the frequency where no noise regulation exists is 500 kHz, the present invention is effective for a high-pressure discharge lamp with a rated power of 70 W, but the high-pressure discharge lamp with a rated power of 30 W. Then, since the lighting frequency must be 500 kHz or more, the application of the present invention is not effective.

Therefore, on the premise of the characteristics of the high pressure discharge lamp exemplified above and the actual state of noise regulation, the high pressure discharge lamp lighting device of the present invention generally has a lighting frequency of 250 kHz to 526 when the rating of the high pressure discharge lamp is 70 W to 200 W. .5 kHz, while avoiding the acoustic resonance phenomenon, the second harmonic can be kept low, and the circuit board of the high-pressure discharge lamp lighting device can be realized in a small size and at low cost.
However, depending on the improvement of the high-pressure discharge lamp itself related to the acoustic resonance phenomenon and the content of the noise regulation in the commercial AC power supply, the application of the present invention can be expected to be effective even outside the above range.

Next, the inventors examined a prototype that applied the configuration of the resonance circuit of the high pressure discharge lamp lighting device disclosed in Patent Document 1 in the process of completing the invention of the present application. Will be described below. A circuit configuration of a conventional high-pressure discharge lamp lighting device is shown in FIG.
The resonance frequency f3 before lighting of the conventional high pressure discharge lamp lighting device is:

It is represented by Since the voltage applied to the high-pressure discharge lamp before the high-pressure discharge lamp is lit is the voltage across the capacitor C3, the capacitor C3 needs to withstand a high voltage of about 1 to 3 kV necessary for starting the discharge of the high-pressure discharge lamp. . Since the capacitor C2 and the capacitor C3 are connected in series in the resonance circuit before lighting, the voltages at both ends of the capacitor C2 and the capacitor C3 are in phase, and the capacitance of the capacitor C3 is the capacitance of the capacitor C2. The smaller the value, the more advantageous a large voltage is generated across the capacitor C3. However, as can be seen from the equation (3), the smaller the capacitor C3, the smaller the combined capacitance of the capacitor C2 and the capacitor C3, so that the resonance frequency f3 before lighting increases.

As described above, since the AC withstand voltage of the capacitor decreases as the frequency increases, if the resonance frequency f3 before lighting is too high, a high voltage necessary for lighting the high-pressure discharge lamp 50 is generated at both ends of the capacitor C3. Sometimes the capacitor C3 may break down due to dielectric breakdown. Moreover, it is necessary to use a switching element having excellent high frequency characteristics, which hinders cost reduction. Therefore, it is difficult to use a capacitor having a small capacitance as the capacitor C3. On the other hand, even if a capacitor having a small capacitance is used as the capacitor C3, if the inductance of the inductor L1 is increased, the resonance frequency before lighting can be lowered to ensure a sufficient withstand voltage of the capacitor C3. When the inductor L1 increases, the loss of the inductor L1 increases, and it is necessary to cool the inductor L1 by special means or increase the size of the inductor L1. Since the inductor L1 is originally a relatively large component, increasing the inductor L1 hinders miniaturization because the circuit board of the high-pressure discharge lamp lighting device becomes large. Therefore, it is substantially difficult to increase the inductance of the inductor L1 and reduce the capacitance of the capacitor C3.
In addition, when the capacitor C3 is made small, there is a method of starting the discharge of the high pressure discharge lamp using other high voltage generating parts such as an igniter without using the high voltage generated by resonance. Since there are new parts, it is obvious that it is disadvantageous in terms of cost reduction and miniaturization.

Considering the above limitation, consider the case where the capacitor C3 is increased. Consider a case where the high-pressure discharge lamp lighting device of the present invention is lit at the same resonance frequency as the resonance frequency before lighting. When the capacitor C2 is 4000 pF and the capacitor C3 is 4000 pF, the combined capacitance of the capacitor C2 and the capacitor C3 is 2000 pF. Therefore, when the inductor L1 is 60 μH, the resonance frequency is about 459 kHz, which is the same as the case of the present invention. To do.
Therefore, similarly to the high-pressure discharge lamp lighting device of the present invention, the discharge of the high-pressure discharge lamp can be started by gradually sweeping and reducing the frequency from the frequency of 500 kHz.
However, the voltage applied to the capacitor C3 connected in parallel with the high-pressure discharge lamp is divided by the series connection of the capacitor C2 and the capacitor C3, so that the voltage is half that of the high-pressure discharge lamp lighting device of the present invention. The reliability of the start of discharge is inferior. Moreover, although a high voltage of about 1 to 3 kV necessary for starting the discharge of the high voltage lamp is applied, the AC withstand voltage is lower than that of the present invention due to the large capacitance, and the sufficient withstand voltage. It is also difficult to secure the voltage. Furthermore, since a high voltage is also applied to the capacitor C2, it is impossible to use a chip multilayer ceramic capacitor for the capacitor C2, which prevents the circuit board from being downsized.

In order to use a chip multilayer ceramic capacitor for the capacitor C2, it is necessary to increase the capacitance of the capacitor C2. For example, if the capacitor C2 is an 80000 pF chip multilayer ceramic capacitor, the capacitor C3 has 2050 pF and substantially the same resonance frequency. When the high-pressure discharge lamp is turned on, a large current, which is the sum of the current flowing through the high-pressure discharge lamp and the current flowing through the capacitor C3, flows through the capacitor C2, and must be able to withstand the large current. However, since it is difficult to obtain a capacitor that can withstand a large current with a large capacitance of 80,000 pF, it is necessary to connect a plurality of chip multilayer ceramic capacitors having a small capacitance substantially in parallel. Costing is hindered.
On the other hand, in the high pressure discharge lamp lighting device of the present invention, since only the current flowing through the high pressure discharge lamp flows through the first capacitor C1, a chip multilayer ceramic capacitor that is normally available is sufficient.

  Next, consider after the high-pressure discharge lamp is lit. When the capacitor C2 was 80000 pF and the capacitor C3 was 2050 pF, the power of the high-pressure discharge lamp could be 100 W at a duty ratio of 34% at 450 kHz as in the above-described high-pressure discharge lamp of the present invention. Further, when the duty ratio was 50%, it could be 100 W at 500 kHz. As described above, if a capacitor having a large capacitance can be used as the capacitor C2, it is possible to turn on the high-pressure discharge lamp with the rated power while suppressing the second harmonic as in the present invention. It is difficult to downsize a circuit board using a capacitor. On the other hand, when the capacitors C2 and C3 are set to 4000 pF, the power of the high-pressure discharge lamp can be set to 100 W when the duty ratio is 14%. However, since the duty ratio is low, the second harmonic component becomes large.

  Further, in each modification of the present invention, the converter includes an AC / DC converter that converts the AC voltage of the commercial AC power source into a DC voltage, and a connection so that the converter can be used by being connected to a plurality of types of commercial AC power sources having different voltages. In general, a booster chopper that is less expensive than a buck-boost chopper is used for a device that has a booster chopper that converts a DC voltage from an AC / DC converter into a predetermined constant DC voltage regardless of the type of commercial AC power supply used. Thus, there is an advantage that a constant DC voltage can be realized.

  The resonance circuit has an inductor and a second capacitor connected in series to the AC output terminal of the half-bridge inverter, and a first capacitor and a high-pressure discharge lamp connected in series between the terminals of the second capacitor. In particular, a relatively high voltage is not applied to the first capacitor, and a capacitor having a relatively low withstand voltage specification can be used.

  In addition, when the chip capacitor is used as the first capacitor, the surface mount type of the substrate is used, so that the withstand voltage characteristic is relatively low but the size is small. realizable.

It is a figure which shows the structure of the high pressure discharge lamp lighting device by Embodiment 1 of this invention. The definition of the output voltage waveform and duty ratio of the half-bridge inverter 2 when it is regarded as a complete rectangular waveform is shown. FIG. 2 shows the relationship between the duty ratio and the harmonic component by performing a Fourier transform on the rectangular waveform of FIG. It is a figure which shows the voltage and current waveform actual value of the half-bridge inverter 2 when Duty ratio differs small and large. It is a figure which shows the frequency spectrum of the noise terminal voltage measurement result of a high voltage | pressure discharge lamp lighting device when Duty ratio differs small and large. It is a figure which shows the structure of the conventional high pressure discharge lamp lighting device.

Explanation of symbols

1 converter, 2 half-bridge inverter, 3 resonant circuit,
4 High pressure discharge lamp, 5 AC / DC converter, 6 Boost chopper, 9 Control circuit,
10 commercial AC power supply, L1 inductor, C1 first capacitor,
C2 Second capacitor.

Claims (5)

A converter that is connected to a commercial AC power source and converts the AC voltage of the commercial AC power source into a predetermined constant DC voltage, a half-bridge inverter that includes a switching element and converts the DC voltage of the converter into a variable frequency AC voltage, and this half-bridge inverter The high-pressure discharge lamp in the resonance circuit is controlled by turning on and off an inductor and a capacitor that form a resonance circuit connected to the AC output terminal of the high-frequency discharge lamp and resonates at a predetermined frequency, and a switching element of the half-bridge inverter. In a high-pressure discharge lamp lighting device comprising a control circuit for controlling the duty ratio of the half-bridge inverter so as to start a discharge by applying a high voltage to the high-pressure discharge lamp and maintain the power of the high-pressure discharge lamp at a predetermined value during discharge,
When the lower limit value of the frequency at which the acoustic resonance phenomenon does not occur in the high pressure discharge lamp is the first frequency, and the upper limit value of the frequency at which noise regulation due to current outflow to the commercial AC power supply does not exist, the second frequency,
The control circuit sets the output frequency of the half-bridge inverter between the first frequency and the second frequency, and the harmonic component of the output of the half-bridge inverter does not exceed the noise regulation. A high-pressure discharge lamp lighting device characterized in that the duty ratio of the half-bridge inverter is controlled within a predetermined range. The converter includes an AC / DC converter that converts an AC voltage of the commercial AC power source into a DC voltage and a type of the commercial AC power source to be connected so that the converter can be used by connecting to a plurality of types of commercial AC power sources having different voltages. 2. The high pressure discharge lamp lighting device according to claim 1, further comprising a step-up chopper that converts the DC voltage from the AC / DC converter into the predetermined constant DC voltage. The capacitor includes a first capacitor and a second capacitor, and the resonance circuit connects the inductor and the second capacitor in series to an AC output terminal of the half-bridge inverter, and further 3. The high pressure discharge lamp lighting device according to claim 2, wherein the first capacitor and the high pressure discharge lamp are connected in series between terminals of two capacitors. 4. The high pressure discharge lamp lighting device according to claim 3, wherein a chip capacitor is used as the first capacitor. 5. A high-pressure discharge lamp lighting device according to any one of claims 1 to 4, and an illumination device comprising the high-pressure discharge lamp that is lit by the high-pressure discharge lamp lighting device.

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