JP2008277083A - High-pressure discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent failures such as startup failure of a high-pressure discharge lamp and short life of a discharge gap, even if an initial breakdown voltage of the discharge gap fluctuates more highly than usual. <P>SOLUTION: The high-pressure discharge lamp lighting device includes: a step-down chopper circuit for receiving an output from a direct-current power source to supply power to the high-pressure discharge lamp; a full-bridge circuit for converting an output of the step-down chopper circuit into a high-frequency and a low-frequency alternating-current outputs to supply to the high-pressure discharge lamp; and an igniter circuit for receiving the high-frequency voltage output of the full-bridge circuit and generating pulse voltage for starting the high-pressure discharge lamp. The device includes a pulse-voltage generation number detecting circuit for detecting the number of generation per given hour of the pulse voltage at the igniter circuit. <P>COPYRIGHT: (C)2009,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.

  In recent years, the high pressure discharge lamp lighting device has become smaller and lighter due to the digitization, and the high pressure discharge lamp 50 is started at a high frequency by the combination of the step-down chopper circuit 20, the full bridge circuit 30, and the igniter circuit 40 as shown in FIG. High-pressure discharge lamp lighting devices that are stably lit with a low-frequency rectangular wave are becoming widespread.

  The operation of the conventional circuit of FIG. 2 will be described. The control method of the PWM control circuit 28 constituting the step-down chopper circuit 20 is as follows: a lamp 27 is proportional to the lamp current by the resistor 27; The signal is detected so that the lamp current signal and the lamp voltage signal are multiplied by a multiplier, or a voltage signal calculated by a microcomputer, and the high-pressure discharge lamp 50 can be lit at the rated lamp power in advance at the rated lamp voltage. The set reference voltage is compared with the error amplifier, and the duty ratio of the transistor 21 is controlled in pulse width so that the voltage signal obtained by multiplying the lamp current signal and the lamp voltage signal or the voltage signal calculated by the microcomputer becomes constant. The high-pressure discharge lamp 50 is lit with appropriate power (for example, Patent Document 1).

  Next, the operation of the full bridge circuit 30 which operates by receiving the limited DC output of the step-down chopper circuit 20 is alternately conducted at a frequency at which the transistors 31 and 34 and the transistors 32 and 33 are controlled by the bridge control circuit 35. -By repeating non-conduction, the DC output of the step-down chopper circuit 20 is converted into an AC current and supplied to the high-pressure discharge lamp 50.

  Here, when starting the high-pressure discharge lamp 50, the choke connected to the midpoints of the transistors 31 and 34 and the transistors 32 and 33 is increased by increasing the frequency controlled by the bridge control circuit 35 to several tens of kHz for a certain period of time. The series circuit of the coil 36 and the capacitor 37 resonates, and a resonance voltage having a high sine wave frequency determined by the inductance of the choke coil 36, the capacitance of the capacitor 37, and the frequency of the bridge control circuit 35 is generated at the ends of the choke coil 36 and the capacitor 37. The high-frequency resonance voltage is also applied to the end of the high-pressure discharge lamp 50 connected in parallel to the capacitor 37.

  Next, the operation of the igniter circuit 40 for starting the high pressure discharge lamp 50 is performed by the high frequency generated at the end of the capacitor 37 when the bridge circuit is operating at a high frequency of several tens of kHz by the bridge control circuit 35 described above. When a sine wave voltage is received and the connection point side of the choke coil 36 and the capacitor 37 has a positive potential, a current flows in the direction of the diode 41, the resistor 43, and the capacitor 45, and the capacitor 45 is charged. When the polarity of the high-frequency sine wave voltage is reversed and the connection point between the choke coil 36 and the capacitor 37 is a negative potential, a current flows in the direction of the capacitor 46, the resistor 44, and the diode 42, and the capacitor 46 is charged.

By repeating the above operation, the potential at the end of the series circuit of the capacitor 45 and the capacitor 46 gradually increases. Generally, the voltage generated at the end of the capacitor 37 is the inductance of the choke coil 36 as shown in FIG. And the resonance frequency f ₀ determined by the capacitance of the capacitor 37 is the maximum, and when the voltage (a) of the capacitor 37 at the frequency f ₁ is continuously supplied, the potential at the end of the series circuit of the capacitor 45 and the capacitor 46 becomes the discharge gap 48. When the reach the breakdown voltage V _0, the series circuit from the discharge gap 48, the primary winding of the pulse transformer 47 current flows in the primary winding of the pulse transformer 47 the voltage of the capacitor 45 and 46 to apply a capacitor 45 Will be.

  As a result, a pulse voltage corresponding to the step-up ratio of the pulse transformer 47 is generated in the secondary winding of the pulse transformer 47 with respect to the voltage applied to the primary winding. Since the voltage is applied to the discharge lamp 50, the high-pressure discharge lamp 50 breaks down by the pulse voltage and starts discharging.

However, in actual use, the inductance of the choke coil 36 and the capacity of the capacitor 37 vary, and the inductance and capacity of the wire connecting the high pressure discharge lamp lighting device and the high pressure discharge lamp 50 also affect this resonance. Therefore, as shown in FIG. 4, in actual use, the original resonance frequency f ₀ shifts to f ₀ ′ or f ₀ ″. Therefore, the discharge gap 48 is originally broken. the voltage a of the capacitor 37 at the frequency f ₁ which can be down a ', a ", and the may not be able to stabilize break down a certain frequency f ₁ in the discharge gap 48.

Further, as shown in FIG. 5, the discharge gap 48 also varies in the range of a ^{+ to} a ⁻ with respect to the center value a of the breakdown voltage, so that the voltage at the end of the capacitor 37 at the frequency f ₁ is constant. Even in this case, the discharge gap 48 may not be broken down stably.

Therefore, in the circuit of the conventional example, as shown in FIG. 6, the operation of the bridge control circuit 35 starts at _fstart where the voltage generated at the end of the capacitor 37 is low, and the voltage at the end of the capacitor 37 is changed by changing the frequency with time. The discharge gap 48 can be reliably and stably broken down even if there is variation in the resonance conditions of the choke coil 36 and the capacitor 37 and the breakdown voltage of the discharge gap 48.

  Even after the discharge gap 48 breaks down, if the frequency is changed, the voltage generated at the end of the capacitor 37 becomes higher than necessary until the high-pressure discharge lamp 50 starts discharging. At the time of down, the frequency of the bridge control circuit 35 is fixed as shown in FIG. 7, and stable breakdown can be repeated.

  Next, by operating the bridge circuit 30 at a high frequency from the bridge control circuit 35 for a certain period of time immediately after the high-pressure discharge lamp 50 starts discharging, the choke coil 36 is added to the step-down chopper circuit 20 and the current limiting element. Thus, the high-pressure discharge lamp 50 starts high-frequency lighting with the limited current.

  Then, when the bridge control circuit 35 operates the bridge circuit at several tens to several hundreds of Hz after a predetermined time has elapsed, the high pressure discharge lamp 50 shifts from high frequency lighting to low frequency rectangular wave lighting and maintains stable discharge.

At this time, the choke coil 36 and the capacitor 37 also serve as a filter circuit for reducing the ripple current generated by the switching operation of the chopper circuit 20 that flows to the high-pressure discharge lamp 50.
JP 2004-95334 A

By the way, as described above, the igniter circuit 40 of the conventional high pressure discharge lamp lighting device performs control to increase the frequency of the bridge circuit 30 with time from _fstart , so that the voltage at the end of the capacitor 37 gradually increases. Since it changes in the direction, it is possible to reliably break down the discharge gap 48 even if the resonance conditions and the breakdown voltage of each discharge gap vary.

However, the voltage discharge gap 48 breaks down, or initially significantly lower than the normal breakdown voltage V ₀ when the breakdown, which may or higher.
When the initial breakdown voltage is lowered, the operating frequency of the full bridge circuit is maintained as it is as shown in FIG. 8, so that the voltage at the capacitor 37 is also lowered, and therefore the voltage at the capacitors 45-46 is also slower than usual. As a result, the number of times the discharge gap 48 breaks down decreases, or the worst breakdown cannot be achieved. For this reason, the startability of the high-pressure discharge lamp 50 may be deteriorated, or the start may not be started.
Further, when the initial breakdown voltage is increased, the number of breakdowns of the discharge gap 48 is remarkably increased as shown in FIG. 9, and the life of the discharge gap 48 is shortened.

  A first aspect of the present invention for solving the above problems is a step-down chopper circuit that receives an output from a DC power source and supplies electric power to a high-pressure discharge lamp, and outputs the step-down chopper circuit to high-frequency and low-frequency AC outputs. An igniter circuit in a high-pressure discharge lamp lighting device comprising a full-bridge circuit that converts and supplies a high-voltage discharge lamp to a high-voltage discharge lamp that receives a high-frequency voltage output from the full-bridge circuit and generates a pulse voltage for starting the high-pressure discharge lamp It is a high pressure discharge lamp lighting device provided with the pulse voltage generation number detection circuit which detects the generation number of the pulse voltage per predetermined time.

  In the first aspect, a resonance circuit that generates a high-frequency voltage output by a switching operation of a full bridge circuit is provided, and the number of pulse voltage generations per predetermined time detected by the pulse voltage generation number detection circuit is greater than the predetermined number of pulse generations. In the case where there are few, the high-frequency voltage output is increased by changing the operating frequency of the full-bridge circuit.

  In the first aspect, a resonance circuit that generates a high-frequency voltage output by a switching operation of a full bridge circuit is provided, and the number of pulse voltage generations per predetermined time detected by the pulse voltage generation number detection circuit is greater than the predetermined number of pulse generations. When there were many, it was comprised so that the operating frequency of a full bridge circuit might be changed and a high frequency voltage output might be made low.

  According to a second aspect of the present invention, there is provided a light source device 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 a housing containing at least the high pressure discharge lamp lighting device. is there.

  According to the high pressure discharge lamp lighting device of the present invention, even if the initial breakdown voltage of the discharge gap varies significantly from the normal time, it is possible to prevent problems such as a defective start of the high pressure discharge lamp and a short life of the discharge gap.

Next, embodiments will be described. FIG. 1 is a circuit configuration diagram showing an embodiment of a high pressure discharge lamp lighting device according to the present invention. The same or corresponding members as those in the conventional example shown in FIG. Description is omitted.
The high pressure discharge lamp lighting device according to the present invention is different from the conventional example as follows. In other words, the igniter circuit 40 is provided with a pulse generation number detection circuit 491 so that the operation of the full bridge control circuit can be controlled by the detection result of the pulse generation number detection circuit.

  In the operation, when the initial breakdown voltage of the discharge gap 48 becomes low, the pulse generation number detection circuit 491 detects that the number of pulses generated per predetermined time of the igniter circuit 40 has fallen below the specified value range. Then, by increasing the operating frequency of the full bridge circuit and increasing the voltage at the capacitor 37 end, the number of pulses generated in the igniter circuit 40 is increased to a specified value range. FIG. 10 shows a change in voltage at the capacitor 37 end and a voltage change at the gap 48 end at this time.

  Further, when the initial breakdown voltage of the discharge gap 48 becomes high, the pulse generation number detection circuit 491 detects that the number of pulses generated per predetermined time of the igniter circuit 40 has exceeded the specified value range. Then, by lowering the operating frequency of the full bridge circuit, the voltage at the end of the capacitor 37 is lowered, and the number of pulses generated in the igniter circuit 40 falls within the specified value range. FIG. 11 shows changes in the voltage at the capacitor 37 and the voltage at the gap 48 at this time.

Note in the conventional example and embodiment is described with a higher operating frequency of the full bridge circuit and the resonance voltage increases, with the resonance voltage curve of the high-frequency side of the f ₀ of FIG. 3, the resonance voltage lowering frequency May be made higher.

  According to the above configuration, the resonance voltage generated in the capacitor 37 is controlled so as to be in an appropriate range, and thereby the number of breakdowns of the gap 48 per predetermined time is also maintained in an appropriate range. Even if there are fluctuations, it is possible to prevent problems such as poor starting of the high pressure discharge lamp and short life of the discharge gap.

  In the above embodiment, even when the initial breakdown voltage of the discharge gap fluctuates significantly from the normal time, the high pressure discharge lamp lighting device that can prevent problems such as a start failure of the high pressure discharge lamp and a short life of the discharge gap is shown. FIG. 12 shows a light source device as an application using the same. In FIG. 12, 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 described above, since the high-pressure discharge lamp lighting device that prevents problems such as poor starting of the high-pressure discharge lamp and short life of the discharge gap is incorporated, a highly reliable light source device that ensures startability can be obtained.

1 is a circuit configuration diagram showing an embodiment of a high pressure discharge lamp lighting device according to the present invention. Circuit configuration diagram showing a conventional high pressure discharge lamp lighting device The figure which shows the relationship between the bridge circuit switching frequency and the resonance voltage in the conventional example The figure which shows the relation between the bridge circuit switching frequency and the resonance voltage including the variation in the conventional example The figure which shows the relationship of the switching frequency of a bridge circuit in a prior art example, the resonance voltage, and the variation of the breakdown voltage of a discharge gap. The figure which shows the operation of the switching frequency of the bridge circuit in the conventional example The figure which shows the relation between the operation of the switching frequency of the actual bridge circuit and the discharge gap voltage under normal conditions The figure which shows the relationship between the operation of the switching frequency of a bridge circuit, and the discharge gap voltage when the initial breakdown voltage of the gap in a prior art example is low. The figure which shows the relationship between the operation of the switching frequency of a bridge circuit, and the discharge gap voltage when the first breakdown voltage of the gap in a prior art example is high The figure which shows the relationship between the operation | movement of the switching frequency of a bridge circuit, and the discharge gap voltage when the initial breakdown voltage of the gap in an Example is low. The figure which shows the relationship between the operation | movement of the switching frequency of a bridge circuit, and the discharge gap voltage when the initial breakdown voltage of the gap in an Example is high. The figure which shows the light source device of this invention

Explanation of symbols

10: DC power supply 20: Chopper circuit 30: Full bridge circuit 31, 32, 33, 34: Transistor 35: Bridge control circuit 36: Choke coil 37: Capacitor 40: Igniter circuit 41, 42: Diode 43, 44: Resistor 45 46: Capacitor 47: Pulse transformer 48: Discharge gap 491: Pulse voltage generation number detection circuit 50: High pressure discharge lamp

Claims (4)

A step-down chopper circuit that receives an output from a DC power source and supplies power to the high-pressure discharge lamp; a full-bridge circuit that converts the output of the step-down chopper circuit into a high-frequency and low-frequency AC output and supplies the high-pressure discharge lamp; In the high pressure discharge lamp lighting device comprising an igniter circuit that receives a high frequency voltage output of the full bridge circuit and generates a pulse voltage for starting the high pressure discharge lamp,
A high pressure discharge lamp lighting device comprising a pulse voltage generation number detection circuit for detecting the number of generations of a pulse voltage of the igniter circuit per predetermined time. The high pressure discharge lamp lighting device according to claim 1, further comprising a resonance circuit that generates the high-frequency voltage output by a switching operation of the full bridge circuit,
When the pulse voltage generation number per predetermined time detected by the pulse voltage generation number detection circuit is smaller than the predetermined pulse generation number, the operating frequency of the full bridge circuit is changed to increase the high frequency voltage output. Constructed high pressure discharge lamp lighting device. The high pressure discharge lamp lighting device according to claim 1, further comprising a resonance circuit that generates the high-frequency voltage output by a switching operation of the full bridge circuit,
When the number of pulse voltage generations per predetermined time detected by the pulse voltage generation number detection circuit is greater than the predetermined number of pulse generations, the operating frequency of the full bridge circuit is changed to lower the high frequency voltage output. Constructed high pressure discharge lamp lighting device.   A light source device comprising: the high pressure discharge lamp lighting device according to any one of claims 1 to 3; a high pressure discharge lamp; a reflector to which the high pressure discharge lamp is attached; and a housing that includes at least the high pressure discharge lamp lighting device.

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