JP2010135195A - High pressure discharge lamp-lighting device, projector and starting method of high pressure discharge lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance startability of a lamp, without increasing cost, by using a conventional circuit constitution, in a high pressure discharge lamp-lighting device. <P>SOLUTION: The high pressure discharge lamp-lighting device for lighting a high pressure discharge lamp having a pair of electrodes includes a full bridge circuit (30) for applying AC voltage on the high pressure discharge lamp by converting DC voltage into the AC voltage, and a control means (900) for controlling the full bridge circuit, wherein the lighting device is configured such that the AC voltage is composed of repetition of a first period T<SB>Long</SB>and a second period T<SB>Short</SB>being reversed polarity to the first period T<SB>Long</SB>and shorter than the first period T<SB>Long</SB>in a predetermined period including discharge starting time. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an improvement of a high pressure discharge lamp lighting device for lighting a high pressure discharge lamp, and particularly to an improvement of a starting method of the high pressure discharge lamp.

  In recent years, the high pressure discharge lamp lighting device has been reduced in size and weight by computerization, and includes a step-down chopper circuit 20, a full bridge circuit 30, an igniter circuit 40, and a control means 900 as shown in FIG. 1, as shown in FIG. 2. Description of the Related Art High-pressure discharge lamp lighting devices that are started by applying a rectangular wave voltage to a high-pressure discharge lamp (hereinafter referred to as “lamp”) 50 and then stably lighting with an arbitrary waveform are becoming widespread. In the following description, high frequency means a frequency higher than 1 kHz, and low frequency means a frequency not higher than 1 kHz.

  In the step-down chopper circuit 20, a lamp voltage is detected by a resistor 26, and a lamp current is detected by a resistor 27. Then, in the control of the PWM control circuit 28, the step-down chopper circuit 20 outputs a desired output current or output power based on the detected lamp current or a multiplication value (lamp power) of the detected lamp current and the lamp voltage. Thus, the duty ratio of the transistor 21 is pulse width controlled. As a result, a predetermined DC voltage is applied to the full bridge circuit 30 described later, and the lamp 50 is lit with a desired current or power after the lamp is lit.

  In the full bridge circuit 30, the pair of transistors 31 and 34 and the pair of transistors 32 and 33 are controlled by the driver circuit 37 so as to repeat conduction and non-conduction alternately at a predetermined frequency, whereby the DC output of the step-down chopper circuit 20 is controlled. Is converted into an alternating current and supplied to the lamp 50. The drive frequency and on-duty by the driver circuit 37 are determined by the control means (microcomputer) 900. In general, a positive and negative symmetrical rectangular wave current as shown in FIG. 3 is applied to the lamp.

  When a high-pressure pulse from the igniter circuit 40 is applied to the lamp 50 at the start, the lamp 50 breaks down and glow discharge is started. Thereafter, the glow discharge is changed to the arc discharge, and the light flux rises (over about 1 to 15 minutes).

  Here, in the case of rectangular wave starting, the current is temporarily interrupted at the moment when the polarity of the rectangular wave is switched. Therefore, in the period immediately after the starting when the electrode temperature is low, the current may disappear when the polarity is reversed. As described above, there is a case where the conventional rectangular wave start cannot smoothly shift to the arc discharge.

  In order to solve this problem, for example, Patent Document 1 discloses a configuration in which the frequency at the start of the rectangular wave is lowered and the electrode temperature is raised quickly to reduce the disappearance when the polarity is reversed. However, even if the frequency is lowered, the temperature on the cathode side does not increase greatly even if the temperature rise on the anode side for each cycle is obtained, so the risk of disappearance at the time of polarity reversal is not eliminated.

  As a starting method for making a transition to a smooth arc discharge, there is a DC starting as disclosed in Patent Document 2. Since the polarity is not reversed in the direct current start, there is no danger of turning off the light and the startability is good. In the direct current lighting, the direct current voltage / current is supplied to the lamp 50 by turning on either the pair of transistors 31 and 34 or the pair of transistors 32 and 33 in FIG.

FIG. 2 is a detailed view of the full bridge circuit 30 (particularly the driver circuit 37) of the conventional high pressure discharge lamp lighting device shown in FIG. It should be noted that the igniter circuit 40 and the step-down chopper circuit 20 in the figure are not described in nature and are simplified. The step-down chopper circuit 20 is indicated by a single circuit symbol 20 (hereinafter also referred to as “DC output circuit 20”).
Here, it is assumed that the DC output circuit 20 outputs DC 200V and the low voltage source 92 for IC outputs DC 20V.

  In the full bridge circuit 30 of FIG. 2, the first arm (31, 32) and the second arm (33, 34) are controlled by the first and second half bridge drivers 79 and 89, respectively, and the transistors 31 and 34 are controlled. And the pair of transistors 33 and 32 are alternately turned on / off.

  First, when the pair of transistors 31 and 34 is in the on state, the source terminal of the transistor 34 is connected to the ground, so that the gate terminal of the transistor 34 can be turned on with the voltage of the low voltage source 92. However, since the transistor 31 is on, the potential at the point B becomes 200 V, which is the output voltage of the step-down chopper circuit 20, and in order to keep the transistor 31 on, a voltage of 200 V plus α is applied to the gate terminal of the transistor 31. In this state, a potential difference from point B (source terminal) must be provided. Therefore, a bootstrap capacitor 77 is connected to obtain a voltage corresponding to the plus α. It is assumed that the bootstrap capacitor 77 is charged by the low voltage source 92 before the transistor 31 is turned on. When the transistor 31 is turned on, the voltage at the point B and the voltage of the bootstrap capacitor 77 are respectively input to the half bridge driver 79, and the sum of these voltages (200V plus 220V at the low voltage source 92 in FIG. 2) is 220V. The voltage is applied to the gate terminal of the transistor 31. Thereby, the transistor 31 can be turned on.

  On the other hand, paying attention to the ON state of the low-side transistor 34, the potential at the point D becomes equal to the ground, so that the bootstrap capacitor 87 is charged by the low voltage source 92. Thus, the bootstrap capacitor 77/78 is charged by turning on the low-side transistor 32/34. In general, the capacity of the bootstrap capacitor is 0.47 μ to 2.2 μF.

Next, when the pair of transistors 33 and 32 is on, the transistor 32 can be turned on by the voltage of the low voltage source 92. In the transistor 33, the voltage at the point D and the voltage of the bootstrap capacitor 87 charged before inversion are input to the half-bridge driver 89, and the sum of these voltages is added to the gate terminal of the transistor 33. ) By the potential difference with When the transistor 32 is turned on, the potential at the point B becomes equal to the ground, and the bootstrap capacitor 77 is charged. Thereby, the transistor 31 can be turned on in the next inversion.
The half-bridge driver used in the above configuration is generally called a bootstrap type half-bridge driver (and also in this specification).
JP-A-6-119984 JP 2001-273984 A

However, in the configuration shown in FIG. 1, the bootstrap type half-bridge driver 79/89 operates while the voltage charged in the bootstrap capacitor 77/87 is being discharged (strictly speaking, the voltage is applied to the threshold voltage of the transistor). The high-side transistor 31/33 can only be turned on. Thus, since the high-side transistor 31/33 can be turned on only during the discharge time of the bootstrap capacitor 77/87, a dedicated power source is required to continue supplying voltage to the bootstrap capacitor 77/87 in order to start DC. become. However, the configuration in which the dedicated power source is provided has a large number of parts and increases the cost.
Therefore, it is an object to provide a high pressure discharge lamp lighting device that outputs a start waveform having startability equivalent to that of direct current start without increasing the cost from the conventional high pressure discharge lamp lighting device for AC lighting.

According to a first aspect of the present invention, there is provided a full-bridge circuit (30) for converting a DC voltage into an AC voltage and applying the converted voltage to a high-pressure discharge lamp, and a high-pressure discharge lamp having a control means (900) for controlling the full-bridge circuit. A first and second bootstrap type device in which a full bridge circuit drives a first arm (31, 32), a second arm (33, 34), a first and a second arm, respectively. Half-bridge driver (79, 89) and first and second bootstrap capacitors (77, 87) connected to the first and second half-bridge drivers, respectively, for a predetermined period including immediately after the start of discharge In FIG. 2, the AC voltage is changed to (A) while the high side transistor of one arm and the low side transistor of the other arm are turned on. A first time period T _Long that-up capacitor is discharged, is charged one arm side of the bootstrap capacitor during the high-side transistor is on the low side transistor and the other arm of one arm (B), first The second period T _Short shorter than the period T _Long is repeated, and the half bridge driver controls so that the repetition frequency is 10 Hz to 1 kHz and the second period T _Short is 30 μs to 700 μs. A high pressure discharge lamp lighting device controlled by means.

A second aspect of the present invention is a high-pressure discharge lamp lighting device for lighting a high-pressure discharge lamp having a pair of electrodes, which converts a DC voltage into an AC voltage and applies it to the high-pressure discharge lamp (30). and a control means for controlling the full bridge circuit (900), in a predetermined period including the time of discharge start, the AC voltage and the first time period T _Long, the first period T _Long and opposite polarity second This is a high pressure discharge lamp lighting device in which the full bridge circuit is controlled by the control means so as to repeat the second period T _Short shorter than the one period T _Long .
Here, the repetition frequency of the first period T _Long and the second period T _Short is set to 10 Hz to 1 kHz, and the second period T _{Short is set} to 30 μs to 700 μs.

In the first and second aspects, the control means is configured so that the lengths of the first period T _Long and the second period T _Short become equal after a predetermined time has elapsed.
In addition, after the high pressure discharge lamp is turned off, the first period T _Long is formed by using the electrode having a large amount of mercury as the cathode and the other as the anode among the pair of electrodes.

  The third aspect of the present invention is a projector including the high pressure discharge lamp lighting device, the high pressure discharge lamp, the reflector to which the high pressure discharge lamp is attached, and the high pressure discharge lamp lighting device and the casing that includes the reflector. is there.

According to a fourth aspect of the present invention, there is provided a high pressure discharge lamp by a full bridge circuit having first and second arms and bootstrap type first and second half bridge drivers for driving the first and second arms, respectively. In a predetermined period including immediately after the start of discharge, (A) a high-side transistor of one arm and a low-side of the other arm during a first period T _Long Discharging the bootstrap capacitor connected to the half-bridge driver on one arm side while turning on the transistor; and (B) one arm in a second period T _Short shorter than the first period T _Long. While the low side transistor of the other arm and the high side transistor of the other arm are turned on, the half bridge driver on one arm side In this starting method, the step of charging the bootstrap capacitor connected to the inverter is repeated at a frequency of 10 Hz to 1 kHz, and the second period T _Short is 30 μs to 700 μs.

  According to the present invention, it is possible to obtain startability equivalent to direct current start without increasing the number of parts from the conventional high pressure discharge lamp for alternating current lighting.

Since the circuit configuration of the high pressure discharge lamp lighting device of the present invention is the same as the general circuit configuration diagram of FIG. 1, the description of the configuration is omitted. The control of the present invention will be described below.
FIG. 4 shows a time chart of the operation of each transistor 31-34 in the present invention. As shown in the figure, the control means 900 controls the driver circuit 37 (half-bridge drivers 79 and 89 so that the on-time of the transistors 31 and 34 is long in the period T _Long and the on-time of the transistors 32 and 33 is short in the period T _Short . ) To control. It is assumed that the driving frequency by the half bridge drivers 79 and 89 (that is, the repetition frequency of the period T _Long and the period T _Short ) is 10 Hz to 1 kHz. The lower limit value of the drive frequency can be lowered as the capacitance of the bootstrap capacitors 77 and 87 is increased and the impedance of the gate circuit resistors 71 and 81 of the high side transistors is increased, but the impedance of the gate circuit resistor is 220Ω. When the capacity of the bootstrap capacitors 77 and 87 is set to 2.2 μF when it is set to ˜1 kΩ or less, the drive frequency can be set to 10 Hz.

FIG. 5A shows the output voltage waveform (lamp voltage with reference to point D) of the full bridge circuit 30 in the operation of FIG. 4, and the output voltage waveform is an asymmetric rectangular wave as shown.
Conversely, if the control is performed so that the on-time of the transistors 32 and 33 is long and the on-time of the transistors 31 and 34 is short, the output voltage waveform becomes an asymmetric rectangular wave as shown in FIG. 5B.
The asymmetric rectangular wave consisting of the periods T _Long and T _Short is applied when the lamp 50 is started and when the luminous flux rises thereafter. Therefore, the duration of the asymmetric rectangular wave may be about 1 to 10 seconds after the start of the discharge of the lamp (the lamp 50 is for alternating current lighting. It is better not to continue quasi-DC lighting longer than necessary).
The selection of the waveform in FIG. 5A or 5B will be described later.

The inventors have found that the startability is improved with the above waveform. Specifically, in the test, when the period T _Short was gradually shortened, it was confirmed that if the time was about 700 μs or less, the disappearance at the time of polarity reversal in the time zone immediately after the start of the lamp discharge did not occur. did. This is because the period T _Short ends and the polarity reverses before the discharge electrons in the lamp bulb extinguish due to polarity reversal (positive to negative reversal in FIG. 5A), and the next period Since T _Long is started, it is considered that the discharge is maintained and continued.

Further, the charging time of the bootstrap capacitor (the bootstrap capacitor 77 in the control of FIG. 5A and the bootstrap capacitor 87 in the control of FIG. 5B) connected to the arm-side half bridge driver in which the low-side transistor is turned on during the period T _Short is set. Since it is necessary to ensure, the length of the period T _Short needs to be 30 μs or more.

  As described above, when shifting from glow discharge to arc discharge, if the temperature rise of the electrode is insufficient, it may disappear. The waveform of the present invention has a very short time during which the polarity is inverted, that is, the polarity immediately returns even if the polarity is inverted, and thus disappears. As a result, extremely good startability can be obtained.

  That is, since it is possible to perform lighting close to direct current lighting in a time zone where the extinction is most likely to occur, it is possible to effectively prevent the lamp from extinguishing. Furthermore, it is not necessary to provide a separate dedicated power source for keeping the high-side transistor 31 or 33 on, and a conventional AC lighting circuit can be used as it is, so that there is no cost increase and versatility is high.

Here, it is desirable to appropriately select the polarity of the pair of lamp electrodes and the asymmetric rectangular wave. In general, the adhesion of mercury to the electrode when the lamp is turned off is not uniform. Although it depends on the shape and size of the electrode, the heat capacity of the electrode is small when mercury adheres little (or does not adhere). If this electrode becomes the cathode side during glow discharge, the temperature rise becomes excessive. When the transition from glow discharge to arc discharge is performed in this state, the so-called discharge mark is formed, in which tungsten of the electrode material is excessively scattered at the moment of arc discharge start and adheres to the inside of the bulb near the electrode.
Since the tungsten in the discharge trace does not return to the electrode even in the halogen cycle during lamp operation, the blackening and devitrification of the bulb proceed from this discharge trace, resulting in a short lamp life.

Therefore, it is desirable to adjust the polarity so that the time when an electrode with a large amount of mercury is a cathode is long and the time when an electrode with a small amount of mercury is a cathode is short. That is, in the long period T _Long , the electrode with much mercury adhesion has a low potential with respect to the other, and in the short period T _Short , the electrode with little mercury adhesion has a low potential with respect to the other. It is desirable to form polarity.
Note that which of the pair of electrodes has a large amount of mercury mainly depends on the cooling condition of the lamp, and after the lamp is extinguished, a large amount of mercury adheres to the electrode whose temperature decreases quickly.

Note that the lighting waveform of FIG. 5A or 5B is maintained for a predetermined period after the lamp is lit. This is because, according to the above-mentioned asymmetric waveform, the temperature of the electrode having a longer anode time after the lamp start increases due to the collision of electrons, but the temperature of the shorter electrode does not increase immediately. For this reason, if the waveform is switched to the normal waveform immediately after lighting, it may disappear. Therefore, the lighting with the same waveform is maintained, and the normal waveform (e.g., for example, after ensuring the period in which the electrode having the shorter time as the anode sufficiently rises in temperature due to the heat radiation from the arc or the temperature rise of the entire bulb) It is preferable to switch to a symmetrical rectangular wave. Since the optimum value varies depending on the structure and dimensions of the electrodes and the current value at the start of the start, the predetermined period may be obtained experimentally for the actually employed lamp.
In addition, as described above, the duration of the asymmetric waveform is appropriately 1 to 10 seconds. However, since an appropriate value varies depending on the structure and dimensions of the electrodes, control is performed so that the asymmetric waveform is gradually changed to the normal symmetric waveform. May be.

A test for confirming the startability of the lamp was performed using the waveform of the present invention. The circuit configuration diagram is the same as that of FIG. FIG. 7 shows the starting waveform of the present invention used in the experiment. The frequency was 50 Hz, the longer period T _Long was 19.5 ms, and the shorter period T _Short was 500 μs. In the test method, the lamp was turned on for 3 minutes, restarted after turning off for 1 minute, and it was confirmed whether arc discharge occurred after dielectric breakdown. Ten lamps were tested. As other conditions, the pulse applied at the start was 3 kV, and air cooling was adjusted so that mercury adhered to both electrodes to the same extent.

  In order to compare the results, the same experiment was performed for the conventional symmetrical rectangular wave start and DC start. FIG. 8 shows a symmetric rectangular wave used for starting a symmetric rectangular wave, and the frequency is 50 Hz (each period is 10 ms). FIG. 9 shows a DC waveform used for DC starting.

As a result of the above three types of experiments, 10 out of 10 in the asymmetric rectangular wave start of the present invention, 7 out of 10 in the rectangular wave start, and 10 out of 10 in the DC start do not disappear after dielectric breakdown. It moved to. In other words, it was confirmed that the asymmetric rectangular wave start of the present invention has better startability than the conventional symmetric rectangular wave start and can achieve the startability equivalent to the DC start.
As a result of experiments, it was found that the shorter the period T _Short , the lower the possibility of disappearance. Specifically, it was found that good effects can be obtained when the inversion time is set to 700 μSec or less.

In the above-described embodiment, the high pressure discharge lamp lighting device capable of obtaining a good startability comparable to the direct current start with the configuration of the conventional high pressure discharge lamp is shown. However, a projector as an application using the high pressure discharge lamp is illustrated. 10 shows. In FIG. 10, 61 is a high pressure discharge lamp lighting device of the embodiment described above, 62 is a reflector to which the high pressure discharge lamp 50 is attached, 63 is a housing containing the high pressure discharge lamp lighting device 61, the high pressure discharge lamp 50 and the reflector 62. Is the body. In addition, the figure is a schematic illustration of the embodiment, and the dimensions, arrangement, and the like are not as illustrated. Then, a projector is configured by appropriately arranging a video system member or the like (not shown) in the housing 63.
As a result, it is possible to obtain a projector having good startability and high reliability without increasing the cost.

It is a circuit block diagram of a general high pressure discharge lamp lighting device. It is a circuit block diagram of a general high pressure discharge lamp lighting device. It is a figure which shows the conventional lamp current waveform. It is a time chart figure of transistor operation of the present invention. It is a figure which shows the lamp current waveform of this invention. It is a figure which shows the lamp current waveform of this invention. It is a figure which shows the arc tube of a high pressure discharge lamp. It is a figure which shows the lamp current waveform of the asymmetrical rectangular wave start of this invention. It is a figure which shows the lamp current waveform of the conventional symmetrical rectangular wave starting. It is a figure which shows the lamp current waveform of direct current | flow start. It is a figure which shows the light source device of this invention.

Explanation of symbols

10: DC power supply 20: DC output circuit (step-down chopper circuit)
21: transistor 22: diode 23: choke coil 24: capacitors 25, 26, 27: resistor 28: PWM control circuit 30: full bridge circuits 31, 32, 33, 34: transistor 37: driver circuit 40: igniter circuit 50: high voltage Discharge lamp 61: High pressure discharge lamp lighting device 62: Reflector 63: Housings 71, 72, 73, 74, 81, 82, 83, 84: Resistors 75, 76, 78, 85, 86, 88: Diodes 77, 87: Bootstrap capacitors 80, 90: capacitors 79, 89: half-bridge driver ICs
92: Low voltage source 900: Control means (microcomputer)

Claims (7)

A high-pressure discharge lamp lighting device comprising a full-bridge circuit (30) for converting a DC voltage into an AC voltage and applying the converted voltage to a high-pressure discharge lamp, and a control means (900) for controlling the full-bridge circuit,
The full bridge circuit includes a first arm (31, 32), a second arm (33, 34), and bootstrap type first and second half bridges that drive the first and second arms, respectively. A driver (79, 89) and first and second bootstrap capacitors (77, 87) connected to the first and second half-bridge drivers, respectively;
In a predetermined period including immediately after the start of discharge, the AC voltage causes (A) the bootstrap capacitor on one arm to be discharged while the high-side transistor on one arm and the low-side transistor on the other arm are turned on. A first period T _Long ; and (B) the bootstrap capacitor on the one arm side is charged while the low-side transistor of the one arm and the high-side transistor of the other arm are turned on. A waveform in which a second period T _Short shorter than the period T _Long is repeated,
The high-pressure discharge lamp lighting device in which the half-bridge driver is controlled by the control means so that the repetition frequency is 10 Hz to 1 kHz and the second period T _Short is 30 μs to 700 μs. A high pressure discharge lamp lighting device for lighting a high pressure discharge lamp having a pair of electrodes,
A full bridge circuit (30) for converting a DC voltage into an AC voltage and applying the converted voltage to the high pressure discharge lamp, and a control means (900) for controlling the full bridge circuit;
In a predetermined period including the start of discharge, the AC voltage has a first period T _Long and a second period T _Long having a polarity opposite to that of the first period T _Long and shorter than the first period T _Long. A high pressure discharge lamp lighting device in which the full bridge circuit is controlled by the control means so as to consist of repetitions of _short . 3. The high pressure discharge lamp lighting device according to claim 2, wherein the repetition frequency of the first period T _Long and the second period T _Short is 10 Hz to 1 kHz, and the second period T _Short is 30 μs to 700 μs. High pressure discharge lamp lighting device. 3. The high pressure discharge lamp lighting device according to claim 1, wherein the control means is configured such that after the predetermined time has elapsed, the lengths of the first period T _Long and the second period T _Short are equal. High pressure discharge lamp lighting device. 3. The high-pressure discharge lamp lighting device according to claim 1, wherein after the high-pressure discharge lamp is extinguished, the first period T _Long is formed by using, as the cathode, an electrode with a large amount of mercury attached, and the other as an anode. High pressure discharge lamp lighting device.   A high pressure discharge lamp lighting device according to claim 1, a high pressure discharge lamp, a reflector to which the high pressure discharge lamp is attached, and a projector including the high pressure discharge lamp lighting device and a housing that contains the reflector. A high voltage discharge for applying an AC voltage to the high pressure discharge lamp by a full bridge circuit having first and second arms and bootstrap type first and second half bridge drivers for driving the first and second arms, respectively. A method for starting an electric light,
In a predetermined period including immediately after the start of discharge,
(A) Discharging the bootstrap capacitor connected to the half-bridge driver on one arm side while turning on the high-side transistor on one arm and the low-side transistor on the other arm in the first period T _Long And (B) during a second period T _Short shorter than the first period T _Long , while the low-side transistor of the one arm and the high-side transistor of the other arm are turned on, A starting method in which a step of charging a bootstrap capacitor connected to a half-bridge driver is repeated at a frequency of 10 Hz to 1 kHz, and the second period T _Short is 30 μs to 700 μs.

Images