JP4865308B2 - Discharge lamp lighting device - Google Patents

Description

  The present invention relates to a discharge lamp lighting device, and more particularly to a discharge lamp lighting device suitable for a sequential color reproduction type display.

  Conventionally, high-pressure discharge lamps such as metal halide lamps and high-pressure mercury lamps have been used as light sources for sequential color reproduction type displays because of their high conversion efficiency and the ease of obtaining a point light source. For lighting, a dedicated discharge lamp lighting device that supplies voltage and current necessary for lighting is used.

A conventional discharge lamp lighting device has been proposed that includes a power control circuit that detects lamp voltage and lamp current to control lamp power, and an igniter circuit that generates a high voltage to start the discharge lamp. (For example, see Patent Document 1)
Japanese Patent Laid-Open No. 10-3996

  However, in the discharge lamp lighting device described in Patent Document 1 described above, when the pulse current is superimposed on the lamp current in order to reduce the flicker of the image, the color of the image changes due to the slow rise and fall of the pulse current. There is a problem that it is difficult to apply to a sequential color reproduction system display.

  An object of the present invention is to provide a discharge lamp lighting device that improves the above-mentioned drawbacks of the prior art and enables the pulse current to rise and fall faster.

In order to achieve the above object, as a first means according to the present invention,
A lighting circuit having a discharge lamp and an igniter circuit for generating a high voltage for starting the discharge lamp;
A lamp voltage detecting means for detecting a lamp voltage of the lighting circuit; a lamp current detecting means for detecting a voltage corresponding to a lamp current of the lighting circuit; and a PWM (Pulse Width Modulation) control circuit. A discharge lamp lighting device comprising a power control circuit for controlling a lamp current supplied to the discharge lamp,
An oscillation control circuit for controlling an oscillation waveform of an oscillation signal input to the PWM control circuit;
In the PWM control circuit, the power supplied to the lighting circuit is constant from the detected lamp voltage detected from the lamp voltage detecting means and the voltage corresponding to the detected lamp current detected from the lamp current detecting means. Thus, while controlling the pulse width of the PWM signal output,
By switching the pulse width of the PWM signal according to the oscillation waveform of the oscillation signal transmitted from the oscillation control circuit and making the duty variable directly, the pulse current is superimposed on the lamp current to rise the pulse current, The discharge lamp lighting device is characterized in that the fall is steep.

  As a second means according to the present invention, in the discharge lamp lighting device according to the first means, the oscillation waveform of the oscillation signal of the oscillation control circuit is converted to the oscillation frequency setting resistor of the oscillation circuit of the oscillation control circuit. The discharge lamp lighting device is characterized in that the resistance value is changed and switched in accordance with the lamp lighting signal.

  According to a third means of the present invention, in the discharge lamp lighting device according to the first means, the oscillation waveform of the oscillation signal of the oscillation control circuit is expressed by the capacitance of the oscillation frequency setting capacitor of the oscillation circuit of the oscillation control circuit. The discharge lamp lighting device is characterized in that the value is switched in accordance with the lamp lighting signal.

  According to the present invention, since the oscillation waveform of the PWM control circuit of the power control circuit is controlled to directly vary the duty of the oscillation waveform, the rising and falling speed of the pulse current can be increased.

    Hereinafter, an embodiment of a discharge lamp lighting device according to the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of a projection display of a sequential color reproduction system using a discharge lamp lighting device according to an embodiment of the present invention. This projection display includes a high-pressure discharge lamp 75 and a color filter. A light beam emitted from a high-pressure discharge lamp 75, which is composed of a sequential color device 78 such as a color wheel, an image display device 73, and a screen 71 and controlled by a discharge lamp lighting device 77 described later, is forwarded by a reflector 74. Light that has been condensed (right side in the figure), irradiated to an image display device 73 such as a liquid crystal display that is driven and controlled by an image display device drive circuit 76 via a sequential color device 78, and transmitted through the image display device 73 The image is magnified by an optical system 72 such as a magnifying lens. It projected on the screen 71. The image display device 73 is driven by the sequential color signal by the image display device drive circuit 76 to display an image, and a large screen image is obtained on the screen 71. Here, a transmission type example is shown as the image display device 73, but it goes without saying that the image display device 73 can be configured similarly even if it is a reflection type.

  2A is a sequential color signal 60 sent from the image display device drive circuit 76 to the image display device 73, and shows R (red), G (green), and B (blue) signals. (B) shows a lamp current 62 supplied to a discharge lamp, which will be described later, and a pulse current 61 superimposed on the lamp current 62 in order to prevent image flickering. FIG. 2 (C) shows the supply to the ballast. The synchronized signal 63 is shown. Here, during the generation of the low level signal 64 of the synchronization signal 63, the pulse current 61 will be described later so that it matches one of the R, G, and B signals of the sequential color signal 60 with the period of the low level signal 64. FIG. 2 shows an example that matches the period of the B signal. In this case, since the pulse current 61 does not change the color of the image, it is necessary to make the rising and falling edges of the pulse current 61 steep, and to the low level signal 64 of the synchronizing signal 63 sent at high speed. Correspondingly, the pulse current 61 needs to rise and fall at high speed.

  FIG. 3 is a circuit diagram of a discharge lamp lighting device according to an embodiment of the present invention, where 1 is a first power input terminal to which commercial AC power for lighting the discharge lamp 13 is supplied, and 2 is a MOS -FET, 3 is a diode, 4 is a choke coil, 5 is a capacitor, 6, 7 and 12 are resistors, 8 is a power control circuit, 9 is a lighting circuit, and 18 is a lamp-on signal input to which the synchronizing signal 63 is input. Reference numeral 19 denotes a second power supply input terminal for operating the PWM control circuit 22, 21 denotes a drive circuit for driving the MOS-FET 2 by a signal supplied from the PWM control circuit 22, and 23 denotes that the discharge lamp 13 is lit. Furthermore, when an overvoltage is detected by the resistor 6 as the lamp voltage of the lighting circuit 9, an overvoltage protection circuit 26 sends a signal to the PWM control circuit 22 to stop the operation of the discharge lamp 13, 26 An igniter circuit 31 for generating a high voltage for starting the discharge lamp 13 stops the operation of the overvoltage protection circuit 23 for a predetermined time so that the overvoltage protection circuit 23 does not operate due to an overvoltage generated when the discharge lamp 13 is started. A timer circuit 32 for supplying power to the PWM control circuit 22 supplied from the second power input terminal 19 in response to a lamp lighting signal from the lamp on signal input terminal 18 (in this embodiment, the synchronization signal 63). An intermittent switch circuit 40 is an oscillation control circuit that controls switching of an oscillation waveform of an oscillation signal sent to the PWM control circuit 22 by a lamp lighting signal from the lamp on signal input terminal 18, and 48 is output by the PWM control circuit 22. PWM signal output terminal.

  The discharge lamp lighting device of this embodiment includes a MOS-FET 2, a diode 3, a choke coil 4, a capacitor 5, resistors 6 and 7 for detecting a lamp voltage of a discharge lamp lighting circuit, and the lighting circuit. And a power control circuit 8 having a drive circuit 21 and a PWM control circuit 22, and the lamp of the lighting circuit 9 detected by the resistors 6, 7 and 12. The PWM control circuit 22 controls the lamp voltage and the lamp current of the lighting circuit 9 according to the detection result of the voltage and the lamp current.

  The PWM control circuit 22 is configured such that the power to the lighting circuit 9 from the voltage corresponding to the detected lamp current supplied from the lamp current detection voltage terminal 49 and the detected lamp voltage supplied from the lamp voltage detection voltage terminal 50 is, for example, The pulse width of the PWM signal output from the PWM signal output terminal 48 is controlled so as to be constant, and the pulse width of the PWM signal is switched according to the oscillation waveform of the oscillation signal transmitted from the oscillation control circuit 40 to directly use the duty cycle. Is variable.

  Next, specific examples of the PWM control circuit 22 and the oscillation control circuit 40 will be described with reference to FIGS.

4 shows one specific circuit diagram of the PWM control circuit 22 and the oscillation control circuit 40. FIG. 5 shows the oscillation waveform of the oscillation signal supplied from the oscillation control circuit 40 to the PWM control circuit 22. Is a comparator, 42 is a MOS-FET, 43 and 44 are oscillation frequency setting resistors, and 45 is such that the charging current of the oscillation frequency setting capacitor 46 is proportional to the current flowing through the oscillation frequency setting resistors 43 and 44. The RC oscillation circuit configured, 47 is an input terminal of a reference voltage V2 to be described later, 51 is an arithmetic circuit, 52 is an error amplifier, 53 is a comparator, 65 is an oscillation frequency setting resistor 43 and 44 connected in parallel, and the oscillation frequency oscillation waveform when using the setting capacitor 46, 66 is the oscillation waveform in the case of using the oscillation frequency setting resistor 44 and the oscillation frequency setting capacitor 46 Note that reference numerals 18, 48, 49 and 50 in FIG. 4 denote a lamp-on signal (synchronization signal 63) input terminal, a PWM signal output terminal, a lamp current detection voltage terminal, and a lamp, respectively, as described in FIG. Voltage detection voltage terminal.

  First, the operation of the PWM control circuit 22 will be described. The lamp current detection voltage detected by the resistor 12 is input to the non-inverting terminal of the error amplifier 52 through the input terminal 49 and detected by the resistor 6. The lamp voltage detection voltage is inputted to the inverting terminal of the error amplifier 52 through the arithmetic circuit 51 through the input terminal 50. The arithmetic circuit 51 calculates a lamp voltage of the lighting circuit 9 from the detected lamp voltage detection voltage, calculates a lamp current having a constant power according to the lamp voltage, and a voltage generated by the resistor 12 from the lamp current. Is input to the inverting terminal of the error amplifier 52. The error amplifier 52 compares the detected voltage with the lamp current detection voltage, and outputs an output signal V1 (see FIG. 5) from the error amplifier 52 according to the difference, and inputs the output signal V1 to the inverting terminal of the comparator 53. The oscillation waveform of the RC oscillation circuit 45 of the oscillation control circuit 40 is input to the inverting terminal of the comparator 53.

Now, when the MOS-FET 42 of the oscillation control circuit 40 is turned on or the output of the comparator 41 becomes low level, the oscillation frequency setting resistor 43 is connected in parallel to the oscillation frequency setting resistor 44. The oscillation signal of the oscillation waveform 65 (the waveform of the capacitor 46 ) shown in FIG. 5 having an oscillation frequency with a time constant determined by the resistor and the oscillation frequency setting capacitor 46 is input to the comparator 53, and this oscillation signal and the output By comparison with the signal V1, a PWM signal having a pulse width of D1 (see FIG. 5) is output from the output terminal 48. Accordingly, the drive circuit 21 is driven while the pulse width of D1 slightly fluctuates in accordance with the fluctuation of the voltage of the output signal V1, and the lamp current 62 shown in FIG. 2 is turned on while the lamp power is controlled to be constant, for example. It will flow to the circuit 9.

  Next, in this discharge lamp lighting device, it is necessary to superimpose the pulse current 61 on the lamp current 62 in correspondence with the low level signal 64 of the synchronization signal 63, as shown in FIG. However, the superposition of the pulse current 61 will be described.

  When the synchronizing signal 63 shown in FIG. 2C is input to the lamp-on signal input terminal 18, the MOS-FET 42 is turned on when the synchronizing signal 63 is at a high level and is turned off at a low level. On the other hand, the reference voltage V2 (see FIG. 5) of the terminal 47 is input to the inverting terminal of the comparator 41, and the voltage of the oscillation frequency setting capacitor 46 is input to the non-inverting terminal. When the reference voltage is lower than V2, the output of the comparator 41 is at a low level, and the oscillation frequency setting resistors 43 and 44 are connected in parallel. When the voltage of the oscillation frequency setting capacitor 46 is equal to or higher than the reference voltage V2, whether the resistors 43 and 44 are connected in parallel depends on whether the MOS-FET 42 is turned on or not. Is turned on, that is, when the synchronization signal 63 is at high level, the resistors 43 and 44 are connected in parallel, and the oscillation signal of the oscillation waveform 65 of FIG. 5 is input to the non-inverting terminal of the comparator 53 of the PWM control circuit 22. As described above, the PWM signal having the pulse width D1 is output from the output terminal 48.

  Next, when the voltage of the oscillation frequency setting capacitor 46 is higher than the reference voltage V2 and the MOS-FET 42 is turned off, that is, when the synchronization signal 63 is at a low level, the resistors 43 and 44 are connected in parallel. Since only the resistor 44 is activated, the time constant changes, and the oscillation waveform of the oscillation signal input to the non-inverting terminal of the comparator 53 changes as shown by the oscillation waveform 66 in FIG. 5 so as to have a pulse width D2. Thus, the duty of the PWM signal is increased, and the pulse current 61 is superimposed on the lamp current 62. Since such a change occurs almost simultaneously when the synchronization signal 63 changes to a low level, the rise and fall of the pulse current 61 become steep, and moreover, the change of the synchronization signal 63 can be appropriately handled. It is possible to suppress changes in the hue of the image.

  As described above, in the discharge lamp lighting device including the power control circuit that controls the lamp power by detecting the lamp voltage and the lamp current, the oscillation waveform supplied to the PWM control circuit of the power control circuit is controlled and directly used. Since the pulse current rises and falls at high speed, a discharge lamp lighting device suitable for a sequential color reproduction type projection display can be provided.

  In the specific example, the duty is changed by changing the resistance value of the oscillation frequency setting resistor of the oscillation circuit in the oscillation control circuit 40. However, even if the capacitance value of the oscillation frequency setting capacitor is changed. Similar effects can be achieved.

  Next, one specific example will be described with reference to FIG.

  FIG. 6 shows one specific example of the PWM control circuit 22 and the oscillation control circuit 40 whose basic configurations are substantially the same as those of the PWM control circuit 22 and the oscillation control circuit 40 shown in FIG. Are given the same reference numerals. In FIG. 6, 54 is a MOS-FET, 55 is an oscillation frequency setting resistor, 56 is a power supply terminal, and 57 is an oscillation frequency setting capacitor.

  The RC oscillation circuit is configured such that the charging current of the oscillation frequency setting capacitors 46 and 57 is proportional to the current flowing through the oscillation frequency setting resistor 44.

  Since the reference voltage V2 of the terminal 47 is input to the inverting terminal of the comparator 41 and the voltage of the capacitor 46 is input to the non-inverting terminal, the output of the comparator 41 is low when the voltage of the capacitor 46 is V2 or less. Thus, the MOS-FET 42 is turned off, the capacitor 57 is not connected in parallel with the capacitor 46, and the oscillation signal of the oscillation waveform 65 in FIG. 5 is input to the comparator 53.

  When the voltage of the capacitor 46 is equal to or higher than the reference voltage V2, whether the capacitor 57 is connected in parallel with the capacitor 46 depends on the ON / OFF operation of the MOS-FET 42. When the synchronizing signal 63 is input to the lamp-on signal input terminal 18, the MOS-FET 42 is turned on when the synchronizing signal 63 is at a low level and turned off when the synchronizing signal 63 is at a high level. When the synchronization signal 63 is at a low level and the voltage of the capacitor 46 is equal to or higher than the reference voltage V2, the capacitor 57 is connected in parallel to the capacitor 46, and the oscillation waveform (the waveform of the capacitor 46) is as shown by the waveform 66 in FIG. Become. When the synchronization signal 63 is at a high level, the capacitor 57 is not connected in parallel with the capacitor 46, and the oscillation waveform is as shown by the waveform 66 in FIG. As a result, assuming that the input voltage to the inverting terminal of the comparator 53 is V1, the duty of the waveform of the PWM signal that is the output of the comparator 53 is larger when the synchronization signal 63 is at the low level than when it is at the high level. The current increases and the pulse current is superimposed. Since switching between the oscillation waveforms 65 and 66 occurs instantaneously, the rise and fall of the pulse current are performed extremely steeply and at high speed.

  As described above, also in this embodiment, it is possible to achieve the same operations and effects as those in the case where the duty is varied by changing the resistance value of the oscillation frequency setting resistor shown in FIG.

  As described above, the discharge lamp lighting device according to the present invention can be suitably used for a sequential color reproduction type display, but lights up a high-pressure discharge lamp for other uses that require a change in the lamp current at a high speed. It can also be applied as a device.

It is a schematic block diagram of the projection display of the sequential color reproduction | regeneration system which uses the discharge lamp lighting device concerning one Embodiment of this invention. (A) is a diagram showing a sequential color signal sequence, (B) is a waveform diagram of a lamp current flowing in the lighting circuit, and (C) is a diagram showing a synchronization signal. It is a circuit diagram of the discharge lamp lighting device of one embodiment by the present invention. FIG. 2 is a circuit diagram of a PWM control circuit 22 and an oscillation control circuit 40 used in the discharge lamp lighting device of one embodiment according to the present invention. It is a figure which shows the oscillation waveform of the oscillation signal output with the oscillation control circuit 40 of embodiment by this invention. FIG. 4 is a circuit diagram of a PWM control circuit 22 and an oscillation control circuit 40 used in a discharge lamp lighting device according to another embodiment of the present invention.

Explanation of symbols

1 Power input terminal 2, 42, 54 MOS-FET
3 Diode 4 Choke coil 5 Capacitor 6, 7, 12 Resistor 8 Power control circuit 9 Lighting circuit 13 Discharge lamp 18 Lamp on signal input terminal 21 Drive circuit 22 PWM control circuit 40 Oscillation control circuit 41, 53 Comparator 43, 44, 55 Oscillation Frequency setting resistor 45 RC oscillation circuit 46, 57 Oscillation frequency setting capacitor 47 Reference voltage input terminal 48 PWM signal output terminal 49 Lamp current detection voltage terminal 50 Lamp voltage detection voltage terminal 51 Arithmetic circuit 52 Error amplifier 60 Sequential color signal 61 Pulse current 62 Lamp current 63 Sync signal 64 Low level signal 65, 66 Oscillation waveform

Claims (3)

A lighting circuit having a discharge lamp and an igniter circuit for generating a high voltage for starting the discharge lamp;
The discharge lamp includes a lamp voltage detection means for detecting a lamp voltage of the lighting circuit, a lamp current detection means for detecting a voltage corresponding to the lamp current of the lighting circuit, and a PWM control circuit. In a discharge lamp lighting device comprising a power control circuit for controlling a lamp current to be supplied,
An oscillation control circuit for controlling an oscillation waveform of an oscillation signal input to the PWM control circuit;
In the PWM control circuit, the power supplied to the lighting circuit is constant from the detected lamp voltage detected from the lamp voltage detecting means and the voltage corresponding to the detected lamp current detected from the lamp current detecting means. Thus, while controlling the pulse width of the PWM signal output,
By switching the pulse width of the PWM signal according to the oscillation waveform of the oscillation signal transmitted from the oscillation control circuit and making the duty variable directly, the pulse current is superimposed on the lamp current to rise the pulse current, A discharge lamp lighting device characterized by a steep fall. In the discharge lamp lighting device according to claim 1,
A discharge lamp lighting device that switches an oscillation waveform of an oscillation signal of the oscillation control circuit by changing a resistance value of an oscillation frequency setting resistor of the oscillation circuit of the oscillation control circuit according to the lamp lighting signal . In the discharge lamp lighting device according to claim 1,
A discharge lamp lighting device, wherein an oscillation waveform of an oscillation signal of the oscillation control circuit is switched by changing a capacitance value of an oscillation frequency setting capacitor of the oscillation circuit of the oscillation control circuit according to the lamp lighting signal.

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