JP2016162581A - Discharge lamp driving device, light source device and projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge lamp driving device, a light source and a projector that can use a coil having small inductance in a resonance circuit.SOLUTION: A discharge lamp driving device comprises a down chopper unit 71 which contains a coil 712 and a capacitor 714 connected in series and steps down an input DC voltage input, a power conversion unit 72 for inverting the polarity of the voltage output from the down chopper unit 71, a resonance circuit unit 73 which contains a coil 731 and a capacitor 733 connected in series, receives an input voltage from the power conversion unit 72 and outputs a voltage for turning on the discharge lamp 10, and a control unit 76 for controlling the down chopper unit 71 and the power conversion unit 72. When the discharge lamp 10 is started up, the control unit 76 approaches the frequency for controlling the DC voltage inputted to the down chopper unit 71 to the resonance frequency of the coil 712 and the capacitor 714.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a discharge lamp driving device, a light source device, and a projector.

In a conventional discharge lamp lighting device, there is a technology including a resonance circuit that sets a frequency of an alternating voltage from a polarity inversion circuit to a resonance frequency and outputs a high voltage for starting the discharge lamp to the discharge lamp (Patent Document) 1).
There is also a technique for supplying a relatively high frequency alternating current such as 1 kHz to the high pressure discharge lamp as a reference waveform current after shifting to stable lighting (see Patent Document 2).

JP 2010-33795 A JP 2008-153142 A

  However, when a high-frequency driving current is supplied to the discharge lamp after the discharge lamp is lit, the coil inductance increases due to the inductance of the coil included in the resonance circuit that lights the high-pressure discharge lamp. Will be distorted.

  The present invention realizes that a high voltage for starting a discharge lamp can be output to the discharge lamp, and a discharge lamp driving device capable of using a coil having a small inductance in a resonance circuit that outputs a high voltage to the discharge lamp, An object is to provide a light source device and a projector.

  To achieve the above object, a discharge lamp driving device according to one aspect of the present invention includes a first winding and a first capacitor connected in series, and a step-down circuit that steps down an input DC voltage; A polarity inversion circuit that inverts the polarity of the voltage output from the step-down circuit, a second winding and a second capacitor connected in series, and the voltage from the polarity inversion circuit is input to light the discharge lamp. A resonance circuit that outputs a voltage; and a control unit that controls the step-down circuit and the polarity inversion circuit, wherein the control unit controls the DC voltage input to the step-down circuit when the discharge lamp is started. The frequency to be made is close to the resonance frequency of the first winding and the first capacitor.

  The discharge lamp driving apparatus according to one aspect of the present invention can use a coil having a small inductance in the resonance circuit while outputting a high voltage for starting the discharge lamp to the discharge lamp by the resonance circuit. And the influence of the coil can be reduced and distortion of the waveform of the drive current can be suppressed.

  In the discharge lamp driving device according to one aspect of the present invention, the control unit sets a frequency for controlling the direct-current voltage input to the step-down circuit when the discharge lamp is started, as a voltage output from the step-down circuit. The frequency is set so as not to exceed the withstand voltage of the switching element constituting the polarity inversion circuit.

  With this configuration, in the discharge lamp driving device, a coil having a small inductance can be used in the resonance circuit, and the breakdown voltage of the switching element that constitutes the polarity inversion circuit can be prevented.

  A light source device according to one aspect of the present invention includes a discharge lamp that emits light and the discharge lamp driving device described above.

  In the light source device according to one aspect of the present invention, a coil having a small inductance can be used in the resonance circuit, so that the influence of the coil can be reduced and distortion of the waveform of the drive current can be suppressed.

  A projector according to an aspect of the present invention includes a light source device described above, a light modulation device that modulates light from the light source device according to image information, and a projection that projects light modulated by the light modulation device. And an optical device.

  In the projector according to one aspect of the present invention, a coil having a small inductance can be used in the resonance circuit, so that the influence of the coil can be reduced and distortion of the waveform of the drive current can be suppressed.

FIG. 2 is a block diagram illustrating an example of a functional configuration of a projector 1 according to the present embodiment. It is a figure which shows an example of a function structure of the discharge lamp lighting device. It is a figure which shows an output waveform when switching operation of the down chopper part 71 is carried out at the frequency of 73 kHz. It is a figure which shows an output waveform when switching operation of the down chopper part 71 is carried out with the resonant frequency of 13.97 kHz of the down chopper part 71. FIG. It is a figure which shows an output waveform when the down chopper part 71 is switched by the frequency of 25 kHz.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

FIG. 2 is a block diagram illustrating an example of a functional configuration of a projector 1 according to the present embodiment.
As shown in FIG. 1, the projector 1 according to the present embodiment includes a discharge lamp 10 (discharge lamp), a liquid crystal panel 20 (light modulation device), a projection optical system 30 (projection optical device), and an interface (I / F). : Interface) section 40, image processing section 50, liquid crystal panel driving section 60, discharge lamp lighting device 70 (discharge lamp driving device), and CPU (Central Processing Unit) 80.

  The discharge lamp 10 is used as a light source for the projector 1. In the present embodiment, the discharge lamp 10 is, for example, a high-pressure mercury lamp that uses arc discharge. The discharge lamp 10 is not particularly limited, and for example, any other discharge lamp such as a metal halide lamp or a xenon lamp may be used. The discharge lamp 10 and the discharge lamp lighting device 70 constitute a light source device.

The liquid crystal panel 20 modulates and transmits the irradiation light from the discharge lamp 10 according to image information. In the present embodiment, three liquid crystal panels are provided, and each liquid crystal panel 20 is separated from light from the discharge lamp 10 into three color lights of red light, green light, and blue light by a color separation optical system (not shown). Each color light thus modulated is modulated according to image information.
The projection optical system 30 projects the transmitted light transmitted through the liquid crystal panel 20 onto a screen (not shown).

The interface unit 40 converts an image signal SP input from a personal computer (not shown) into image data in a format that can be processed by the image processing unit 50.
The image processing unit 50 performs various image processing such as luminance adjustment and color balance adjustment on the image data supplied from the interface unit 40.
The liquid crystal panel driving unit 60 is for driving the liquid crystal panel 20 based on the image data subjected to the image processing by the image processing unit 50.

  The discharge lamp lighting device 70 includes a later-described resonance circuit unit 73 that functions as an igniter. The discharge lamp lighting device 70 is supplied with AC power supplied to the discharge lamp 10 in the steady lighting state of the discharge lamp 10 through the resonance circuit 73 when the discharge lamp 10 is started (at the time of dielectric breakdown). In comparison, high-frequency and high-voltage AC power is supplied. When the discharge lamp 10 is in a steady lighting state, the discharge lamp lighting device 70 supplies the discharge lamp 10 with AC power having a lower frequency and a lower voltage than that at the time of starting through the resonance circuit unit 73. Details thereof will be described later.

  The CPU 80 controls the image processing unit 50 and the projection optical system 30 according to the operation of a remote controller (not shown) or an operation button (not shown) provided on the main body of the projector 1. In the present embodiment, for example, when the user operates a power switch (not shown) of the projector 1, the CPU 80 instructs the discharge lamp lighting device 70 to turn on the discharge lamp 10.

Next, the configuration of the discharge lamp lighting device 70 will be described in more detail.
FIG. 2 is a diagram illustrating an example of a functional configuration of the discharge lamp lighting device 70.
The discharge lamp lighting device 70 includes a down chopper unit 71 (step-down circuit), a power conversion unit 72 (polarity inversion circuit), a resonance circuit unit 73 (resonance circuit), and a control unit 76.

The down chopper unit 71 converts DC power having a voltage Vin1 applied from a DC power source (not shown) between the input terminal TIN1 and the input terminal TIN2 into DC power having a predetermined DC voltage. .
The down chopper unit 71 includes an n-channel field effect transistor 711, a coil 712 (first winding), a diode 713, and a capacitor 714 (first capacitor). That is, the down chopper unit 71 includes a coil 712 and a capacitor 714 connected in series. According to the down chopper unit 71, the drive current flowing through the n-channel field effect transistor 711 is chopped based on the control signal S 711 supplied from the control unit 76, thereby depending on the frequency and duty ratio of the control signal S 711. DC power having a desired output voltage is obtained.

The power conversion unit 72 converts the DC power supplied from the down chopper unit 71 into AC power, and supplies the AC power to the discharge lamp 10 via a resonance circuit unit 73 described later. The power converter 72 is a full bridge circuit including n-channel field effect transistors 721, 722, 723, and 724 (switching elements).
The drains of the n-channel field effect transistors 721 and 722 are connected to a high potential node NH connected to the input terminal TIN1 through the n-channel field effect transistor 711 and the coil 712 that constitute the down chopper 71. The sources of the n-channel field effect transistors 721 and 722 are connected to the drains of the n-channel field effect transistors 723 and 724, respectively. Each source of the n-channel field effect transistors 723 and 724 is connected to a low potential node NL connected to the input terminal TIN2. In the present embodiment, the voltage applied between the high potential node NH and the low potential node NL is the output voltage Vout1 of the down chopper unit 71.

A control signal Sa is supplied from the control unit 76 to the gates of the n-channel field effect transistor 721 and the n-channel field effect transistor 724. A control signal Sb corresponding to an inverted signal of the control signal Sa is supplied from the control unit 76 to the gates of the n-channel field effect transistor 722 and the n-channel field effect transistor 723.
In the present embodiment, a connection portion between the source of the n-channel field effect transistor 721 and the drain of the n-channel field effect transistor 723 is defined as one output node N1 of the power converter 72. A connection portion between the source of the n-channel field effect transistor 722 and the drain of the n-channel field effect transistor 724 is defined as the other output node N 2 of the power conversion unit 72. In the present embodiment, the voltage applied between the output node N1 and the output node N2 is set as the input voltage Vin2 of the resonance circuit unit 73.

  A pair of n-channel field effect transistors 722 and 723 and a pair of n-channel field effect transistors 721 and 724 are complementarily switched based on a control signal S (Sa, Sb) supplied from the control unit 76. The input voltage Vin2 of the resonance circuit unit 73 is complementarily output from each of the output nodes N1 and N2. That is, the power conversion unit 72 converts DC power into AC power by the switching operation of the n-channel field effect transistors 721, 722, 723, and 724. The AC power is a rectangular wave, and the fundamental frequency is the frequency fs. The frequency fs of the AC power matches the clock frequency of the control signal S supplied from the control unit 76.

The resonance circuit unit 73 functions as an igniter that generates a high-frequency and high-voltage AC voltage compared to the AC voltage supplied to the discharge lamp 10 in a steady lighting state of the discharge lamp 10 at the time of dielectric breakdown of the discharge lamp 10. is there. The resonance circuit unit 73 includes a coil 731 (second winding) and a capacitor 733 (second capacitor). That is, the resonance circuit unit 73 includes a coil 712 and a capacitor 714 that are connected in series. The discharge lamp 10 is connected to the resonance circuit unit 73 via output terminals TOUT1 and TOUT2. In the present embodiment, the voltage applied between the output terminals TOUT1 and TOUT2 is the output voltage Vout2 of the resonance circuit unit 73.
One end of the coil 731 is connected to the output node N1 of the power converter 72, and the other end of the coil 731 is connected to the output terminal TOUT1. The other end of the coil 731 is connected to one electrode of the capacitor 733. The other electrode of the capacitor 733 is connected to the output node N2 and the output terminal TOUT2 of the power converter 72.

Here, as a conventional lighting method of the discharge lamp 10, in the discharge lamp lighting device 70, the down chopper unit 71 in each state at the time of dielectric breakdown of the discharge lamp 10 and steady lighting of the discharge lamp 10 by the control unit 76. An example of control of the power conversion unit 72 will be described. Further, the output level of the output voltage Vout1 of the down chopper unit 71, the input voltage Vin2 of the resonance circuit unit 73, and the output level of the output voltage Vout2 will be described.
The input voltage Vin1 of the down chopper unit 71 is 380V.

  The control unit 76 causes the down chopper unit to perform a switching operation at a frequency of 73 kHz both when the discharge lamp 10 is started (at the time of dielectric breakdown) and in a steady lighting state after the discharge lamp 10 is lit. At any time, 150 V was obtained as the output voltage Vout1 of the down chopper section and 150 V as the input voltage Vin2 of the resonance circuit section.

  In addition, the control unit 76 uses the resonance circuit unit 73 to generate a high voltage when starting the discharge lamp 10 (during breakdown), so that the power conversion unit 72 has a resonance frequency of the resonance circuit unit 73. The switching operation is performed at a frequency of 130 kHz which is about 1/3. In this way, at the time of dielectric breakdown of the discharge lamp 10, a high voltage of 3000 V was obtained as the output voltage Vout2 of the resonance circuit unit 73.

On the other hand, the control unit 76 may control the power conversion unit to change the frequency of AC power (AC voltage) supplied to the discharge lamp 10 in a steady lighting state after the discharge lamp 10 is lit. For example, the discharge lamp 10 is driven at a frequency of 150 Hz to 1350 kHz and a frequency of several kHz to several tens of kHz as a frequency for extending the life of the discharge lamp 10. However, several kHz to several tens of kHz are frequencies higher than 150 Hz to 1350 kHz, but are lower than 130 kHz when the discharge lamp 10 is started.
In other words, in the steady lighting state of the discharge lamp 10, the output voltage Vout2 of the resonance circuit unit 73 does not require a high voltage of 3000V as in the case of dielectric breakdown, and therefore an AC voltage of 150V having a lower frequency than that in the breakdown is generated. I wish I could get it.

That is, the coil 731 of the resonance circuit unit 73 is a coil required for dielectric breakdown. In order to increase the value of the output voltage Vout2 of the resonance circuit unit 73, the control unit 76 sets the power conversion unit 72. The switching operation is performed at a high frequency of 130 kHz, which is about 1/3 of the resonance frequency of the resonance circuit unit 73.
However, the coil 731 of the resonance circuit unit 73 has an adverse effect when an AC voltage having a high frequency of several kHz to several tens kHz is applied to the discharge lamp 10 in a steady lighting state after the discharge lamp 10 is lit. Specifically, since the impedance of the coil increases as the frequency increases, loss occurs. Further, since the frequency component is high when switching the polarity in the AC voltage, the waveform of the drive current is distorted by the impedance of the coil. When the frequency is low such as 150 Hz to 1350 kHz, the influence is small. However, when the frequency becomes high such as several kHz to several tens kHz, the influence of the distortion of the waveform of the drive current becomes large. Therefore, in the present embodiment, the coil 731 having a small inductance can be used in the resonance circuit unit 73, thereby reducing the influence of the coil and suppressing the distortion of the current waveform of the drive current.

Here, the input voltage Vin2 and the output voltage Vout2 are expressed by the following equation (1), where L is the inductance of the coil 731, C is the capacitance value of the capacitor 733, and R is the circuit impedance.
Vout2 = Vin2 × 1 / R × (L / C) ^0.5 (1)
From this equation, when it is desired to obtain the same output voltage Vout2 (set output voltage) between the conventional discharge lamp lighting device and the discharge lamp driving device 70 in the present embodiment as the output voltage Vout2 of the resonance circuit unit 73, the input voltage Vin2 is If it can be increased, it can be seen that the inductance of the coil 731 can be made smaller than when the input voltage Vin2 is low.

  That is, when the discharge lamp 10 is started, if the input voltage Vin2 of the resonance circuit unit 73 is increased, the inductance of the coil 731 can be reduced as compared with the case where the input voltage Vin2 is low. In the state, for example, distortion of the current waveform of the drive current when the frequency becomes high, such as several kHz to several tens kHz, can be suppressed.

Therefore, in the present embodiment, when the discharge lamp 10 is started, the output voltage Vout1 of the down chopper 71 is increased by using the resonance circuit in the down chopper 71 in order to increase the input voltage Vin2 of the resonance circuit 73. . Here, the resonance circuit in the down chopper unit 71 is an LC series resonance circuit including a coil 712 and a capacitor 714.
Here, as an example, it is assumed that the inductance of the coil 712 of the resonance circuit in the down chopper 71 is 130 μH (microhenry) and the capacitance value of the capacitor 714 is 1 μF (microfarad). In this case, the resonance frequency of the resonance circuit in the down chopper 71 is 13.97 kHz, and the resonance period is 71.60 μs.

The control unit 76 can change the output voltage Vout1 of the down chopper unit 71 and the input voltage Vin2 of the resonance circuit unit 73 by changing the switching frequency of the down chopper unit 71 (frequency of the control signal S711).
FIG. 3 shows voltage control in the down chopper unit 71 in the lighting method of the conventional discharge lamp 10. The output voltage Vout1 when the down chopper unit 71 is switched at a frequency of 73 kHz and the transistor 711 in the down chopper unit 71. Is a diagram showing a control signal S711 for chopping the current flowing through The control unit 76 switches the down chopper unit 71 at a frequency of 73 kHz and an on-duty of 39.5% with respect to an input voltage Vin1 (380 V) applied from a DC power supply (not shown). As a result, the output voltage Vout1 is settled around 150V. Therefore, the resonant circuit unit 73 includes a coil 731 having an inductance sufficient to generate 3000 V, which is the output voltage Vout2 required for starting the discharge lamp 10, from 150 V, which is the input voltage Vin2, when the discharge lamp 10 is started. It was necessary to prepare.

Next, a case where the switching frequency of the down chopper 71 is changed will be described.
FIG. 4 shows voltage control in the down chopper unit 71 in the present embodiment. The output voltage Vout1 when the down chopper unit 71 is switched at the resonance frequency of 13.97 kHz of the down chopper unit 71, and the down chopper unit 71. It is a figure which shows control signal S711 which chops the electric current which flows through the transistor 711 of. The control unit 76 switches the down chopper unit 71 at a frequency of 13.97 kHz and an on-duty of 50.0% for the input voltage Vin1 (380 V). As a result, the output voltage Vout1 gradually increases. However, in FIG. 4, the output voltage Vout1 exceeds the breakdown voltage (for example, 600 V in this embodiment) of the n-channel field effect transistors 721, 722, 723, and 724 constituting the power conversion unit 72.

Therefore, the control unit 76 brings the frequency for controlling the DC voltage input to the down chopper unit 71 close to the resonance frequency when the discharge lamp is started, and the output voltage Vout1 output from the down chopper unit 71 is converted into power. The frequency is set so as not to exceed the breakdown voltage of the n-channel field effect transistors 721, 722, 723, and 724 constituting the unit 72.
FIG. 5 shows voltage control in the down chopper 71 in this embodiment, and chops the output voltage Vout1 when the down chopper 71 is switched at a frequency of 25 kHz and the current flowing through the transistor 711 of the down chopper 71. It is a figure which shows control signal S711. For the input voltage Vin1 (380V), the control unit 76 has a frequency of 25 kHz, that is, a frequency close to the resonance frequency of 13.97 kHz shown in FIG. 4 from the frequency 73 kHz shown in FIG. The unit 71 is switched. As shown in FIG. 4, by controlling the input voltage Vin1 at a frequency close to the resonance frequency, the output voltage Vout1 is the withstand voltage of the n-channel field effect transistors 721, 722, 723, and 724 constituting the power converter 72. The peak voltage of the output voltage Vout1 is 580V without exceeding the voltage.

  That is, when the breakdown voltage of the n-channel field effect transistors 721, 722, 723, and 724 constituting the power conversion unit 72 is about 600 V, the control unit 76 sets the output voltage Vout1 to the n-channel field effect transistors 721, 722, It shows that the frequency is set not to exceed the breakdown voltage of 723 and 724. Further, this frequency indicates that the resonance circuit unit 73 only needs to include a coil 731 having an inductance sufficient to generate an output voltage Vout2 of 3000 V from an input voltage Vin2 of 580 V when the discharge lamp 10 is started. .

  Here, how much the inductance of the coil 731 can be made smaller than the inductance of the conventional coil 731 can be obtained from the above equation (1). That is, from the above equation (1), when the discharge lamp 10 is started, the same output voltage Vout2 (3000 V) is generated in the conventional discharge lamp 10 lighting method and the discharge lamp 10 lighting method in the present embodiment. In the conventional lighting method, the input voltage Vin2 is 150V. On the other hand, in the lighting method of this embodiment, the input voltage Vin2 is 580V. Therefore, from the equation (1), the inductance of the coil 731 in the present embodiment can be reduced to 0.067 times the conventional inductance.

  In the discharge lamp lighting device 70 of this embodiment, in order to increase the voltage value (input voltage Vin2) supplied to the resonance circuit unit 73, the coil 712 and the capacitor 714 are included, and the voltage supplied from the DC power supply is stepped down. A resonance phenomenon is generated in the down chopper 71.

  Since the voltage input to the resonance circuit unit 73 can be increased, the coil 731 having a small inductance can be used in the resonance circuit unit 73, that is, with respect to the set output voltage (3000 V in the present embodiment) of the resonance circuit unit 73. Since the inductance of the coil 731 can be reduced, the influence of the coil 731 can be reduced and distortion of the waveform of the drive current can be suppressed. In particular, when the discharge lamp 10 is driven at a high frequency of several kHz to several tens of kHz, for example, in a steady lighting state after the discharge lamp 10 is lit, the waveform of the drive current supplied to the discharge lamp 10 is distorted. It can be effectively suppressed.

  The present invention is not limited to the above-described embodiments and application examples, and various modifications as described below are possible. Moreover, the aspect of the deformation | transformation described below can also combine suitably arbitrarily selected 1 or several.

In the embodiment, the breakdown voltage of the n-channel field effect transistor constituting the power conversion unit 72 is set to 600V. This is an example, if the withstand voltage Vx is larger than 600V, the inductance of the coil 731, the conventional inductance (0.99 / ^Vx) of the description and ^twice, can be further reduced.

  In the above-described embodiment, an example in which the present invention is applied to a transmissive projector has been described. However, the present invention can also be applied to a reflective projector. Here, the “transmission type” means that a liquid crystal light valve including a liquid crystal panel or the like is a type that transmits light. “Reflective type” means that the liquid crystal light valve reflects light. The light modulation device is not limited to a liquid crystal panel or the like, and may be a light modulation device using a micromirror, for example.

  In the above-described embodiment, the example of the projector 1 using the three liquid crystal panels 20 has been described. However, the present invention is applied to a projector using only one liquid crystal panel or a projector using four or more liquid crystal panels. Is also applicable.

DESCRIPTION OF SYMBOLS 10 ... Discharge lamp, 20 ... Liquid crystal panel, 30 ... Projection optical system, 40 ... Interface part, 50 ... Image processing part, 60 ... Liquid crystal panel drive part, 70 ... Discharge lamp lighting device, 71 ... Down chopper part, 711, 721 , 722, 723, 724 ... n-channel field effect transistor, 712, 731 ... coil, 713 ... diode, 714, 733 ... capacitor, 72 ... power converter, 73 ... resonant circuit, 76 ... controller, 80 ... CPU , TIN1, TIN2 ... input terminal, NH ... high potential node, NL ... low potential node, N1, N2 ... output node, TOUT1, TOUT2 ... output terminal, Vin1, Vin2 ... input voltage, Vout1, Vout2 ... output voltage

Claims (4)

A step-down circuit including a first winding and a first capacitor connected in series and stepping down an input DC voltage;
A polarity inversion circuit for inverting the polarity of the voltage output from the step-down circuit;
A resonance circuit that includes a second winding and a second capacitor connected in series, receives a voltage from the polarity inversion circuit, and outputs a voltage for lighting the discharge lamp;
A controller that controls the step-down circuit and the polarity inversion circuit,
The controller is configured to bring a frequency for controlling the DC voltage input to the step-down circuit close to a resonance frequency of the first winding and the first capacitor when the discharge lamp is started. Electric light drive device.   The controller is configured to control a frequency for controlling the DC voltage input to the step-down circuit when the discharge lamp is started, so that a voltage output from the step-down circuit exceeds a withstand voltage of a switching element constituting the polarity inversion circuit. The discharge lamp driving device according to claim 1, wherein the frequency is set to a non-frequency. A discharge lamp that emits light;
The discharge lamp driving device according to claim 1 or 2,
A light source device comprising: A light source device according to claim 3;
A light modulation device that modulates light from the light source device according to image information;
A projection optical device for projecting light modulated by the light modulation device;
A projector comprising:

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