JPH08273867A - Power supply unit, discharge lamp lighting device and image display device - Google Patents

Abstract

PURPOSE: To prevent malfunction caused by noise to avoid abnormal oscillation or circuit breakage by synchronizing a control frequency of a switching element in a DC power supply unit with an operation frequency of a switching circuit in an inverter circuit. CONSTITUTION: Alternating current form a commercial AC power supply unit 3 is converted into direct current in a DC power supply unit 4 in a power supply unit 1, further converted into high frequency alternating current in an AC conversion part 5, then supplied to a discharge lamp 2 to light it. In this discharge lamp lighting device, the DC power supply unit 4 is constituted with a rectifier circuit 6 for rectifying alternating current, a chopper circuit 1 for controlling an electric power, and a smoothing circuit 8 comprising a capacitor. The chopper circuit 7 has a switching element Q which is turned on and off with a control frequency f1 from an oscillator 10 and conducts chopping operation, a step-up and down coil L, and a diode D. The AC conversion part 5 consists of an inverter circuit 11, and in a switching circuit 12, a pair of switching elements Q1 , Q4 , and a pair of switching elements Q2 , Q3 are turned on and off with an operation frequency f2 synchronized with the control frequency f1 through a divider 15 of a synchronizing means 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device, a discharge lamp lighting device and an image display device.

[0002]

2. Description of the Related Art In general, when looking at a power supply device for lighting a discharge lamp, an AC conversion circuit including an inverter circuit is often used to supply AC power to the discharge lamp and maintain lighting. A DC power supply unit is connected to the input stage of the conversion circuit in order to supply DC power from a commercial AC power supply. Here, the DC power supply unit is usually
A full-wave rectifier circuit, a chopper circuit (for example, a step-down chopper circuit), and a smoothing circuit are used.
It is configured to supply the constant-voltage DC power to the inverter circuit side by on / off driving at a high control frequency of about several hundred kHz. On the other hand, the inverter circuit is configured, for example, as a full-bridge type inverter circuit having a switching circuit in which four switching elements are bridge-connected, and the switching elements in the switching circuit are turned on and off at a predetermined operating frequency by a drive control circuit. By doing so, the AC power of a desired frequency is supplied to the discharge lamp side. In the case of a high-pressure discharge lamp such as a metal halide lamp, it is not possible to light it at a high frequency because of the problem of acoustic resonance (acoustic resonance).
Lighting is maintained by low frequency AC power of up to 1000 Hz.

[0003]

However, the drive control circuit for driving the switching element of the chopper circuit of the DC power supply section on and off at the control frequency and the drive control circuit for driving the switching circuit in the inverter circuit on and off at the operating frequency are provided. Since they are provided separately and operate independently, the frequency relationship between them is random. As a result, for example, while the switching element in the chopper circuit is on or off, load current noise synchronized with the operation of the inverter circuit enters the DC power supply side, and the switching element changes from the on state to the off state. To be switched to, or switched from the off state to the on state,
Such a malfunction is highly likely to occur. If the load current noise is large, it may cause abnormal oscillation of the chopper circuit system and may lead to circuit breakdown, which is not preferable.

Further, in the case of a high-pressure discharge lamp, glow discharge does not occur between the electrodes of the discharge lamp only by supplying low-frequency AC power at the time of starting, so that 2
A starter is used to apply a high voltage pulse of approximately 0 kV to the discharge lamp. The no-load open circuit voltage in this case is set to a value such as 250 to 400 V based on the glow-arc transition voltage requirement of the high-pressure discharge lamp. As a result, a high-voltage pulse of 20 kV is applied by the starter to cause the inter-electrode dielectric breakdown of the discharge lamp, and the glow-arc transition is caused by the no-load open voltage 250 to 400 V to start and light the discharge lamp. For this reason, the breakdown voltage of semiconductor elements such as switching elements used in chopper circuits and the like is set to about 500V.

However, even a high-pressure discharge lamp has a stable load voltage during lighting of about 100 V, and a withstand voltage of about 500 V of a semiconductor element is necessary only at the time of starting, and it is considered to be wasteful. In particular, when considering the loss as a lighting circuit, most of it is the loss due to the on resistance of the semiconductor element in the chopper circuit, etc.When using a semiconductor element with a high breakdown voltage, the on resistance is proportional to the breakdown voltage. Therefore, it is preferable to avoid using a semiconductor element having a high breakdown voltage as much as possible because it causes an increase in circuit loss and a decrease in efficiency.

Therefore, the present invention provides a power supply device which can operate normally without being adversely affected on the DC power supply side by noise synchronized with the operating frequency of the inverter circuit due to a load current, and a discharge lamp lighting device using this power supply device, Still another object is to provide an image display device using this discharge lamp lighting device.

Furthermore, when it is necessary to apply a high-voltage pulse, the withstand voltage required for the semiconductor element of the DC power supply unit can be lowered, and the reduction of circuit loss and the reduction of efficiency can be suppressed. It is also an object to provide an image display device using this discharge lamp lighting device.

[0008]

According to a first aspect of the present invention, there is provided a power supply device including a switching element that is switched based on a control frequency, and a DC power supply section that outputs DC power; and a switching element that is turned on and off at the control frequency. An AC conversion unit that has a first drive control unit for controlling; and an inverter circuit including a switching circuit that is switched based on an operating frequency, converts DC power output from the DC power supply unit into AC power, and supplies the AC power to a load. And; second drive control means for driving the switching circuit on and off at the operating frequency; and synchronizing means for synchronizing the control frequency and the operating frequency.

In the present invention, the DC power output from the DC power supply unit includes a DC voltage. Further, in the DC power supply unit, the switching element is configured to be included in, for example, a chopper circuit, and the chopper circuit may be a step-up chopper circuit or a step-down chopper circuit, and may be used properly according to the application. On the other hand, the inverter circuit in the AC conversion unit may be one that outputs AC power in accordance with the switching operation, and the circuit form of the switching circuit may be a full bridge type, a half bridge type, or a one-stone type. It may be.

According to a second aspect of the invention, there is provided the power supply device according to the first aspect, wherein the synchronizing means comprises a frequency divider for dividing the control frequency to obtain an operating frequency. Here, it means that the control frequency is a frequency several steps higher than the operating frequency.

A third aspect of the present invention is the power supply device according to the first or second aspect, in which the DC power supply section has a step-down chopper circuit including a switching element.

The invention according to claim 4 is the invention according to claims 1 to 3.
The power supply device according to any one of 1 to 3, wherein the inverter circuit is a full-bridge type inverter circuit.
Therefore, the configuration includes a switching circuit including four switching elements, and the second drive control circuit alternately turns on and off the pair of switching elements.

The discharge lamp lighting device according to the invention of claim 5 is
A power supply device according to any one of claims 1 to 4; and a discharge lamp as a load.

The invention according to claim 6 is the discharge lamp lighting device according to claim 5, wherein the discharge lamp is a high-pressure discharge lamp;
Further, it has a starter connected between the DC power supply unit and the discharge lamp to apply a high-voltage pulse when the discharge lamp is started. The starter includes, for example, a pulse transformer that outputs a high-voltage pulse.

An image display device according to a seventh aspect of the present invention is the discharge lamp lighting device according to the fifth aspect; an image data output device for outputting image data of an image to be displayed; an irradiation light of the discharge lamp and an image data output. An image forming unit that receives the image data output from the apparatus and forms an image according to the image data. Here, the image display device includes a liquid crystal video projector, a projection device, an overhead projector, and the like. The liquid crystal video projector may be a screen projection system or a system in which an image displayed on the liquid crystal itself is directly viewed. The image data output device and the image forming unit are used according to the image display device. For example, in the case of a liquid crystal video projector,
A device that outputs a video signal according to the NTSC system, a liquid crystal device, or the like is used.

[0016]

According to the invention of claim 1, a control frequency for turning on and off the switching element of the DC power supply unit,
Since the operating frequency for driving the switching circuit in the inverter circuit of the AC conversion unit to be turned on and off is synchronized by the synchronizing means, even if noise that is synchronized with the operating frequency occurs in the load current, this noise is generated by the switching element. It is synchronized with the on / off timing, and no malfunction occurs.

According to the second aspect of the present invention, since the synchronizing means is a frequency divider, an operating frequency synchronized with the control frequency can be easily generated.

According to the third aspect of the invention, since the DC power supply section is formed by the step-down chopper circuit, the necessary DC power can be reliably supplied to the AC conversion section.

According to the invention of claim 4, since the inverter circuit is formed by a full-bridge type inverter circuit, the AC power can be supplied to the load side as usual, and for example, switching is performed at the time of starting after the power is turned on. It is also possible to switch the set of switching elements that are turned on in the circuit at each start, and by making the direction of the current applied to the load different at each start, it is possible to equalize the damage to both electrodes. Become.

According to the invention of claim 5, claim 1
Since the discharge lamp is lit by using the power supply device according to any one of items 1 to 4, the discharge lamp can be lit stably without a malfunction of the DC power supply unit due to the noise of the load current.

According to the sixth aspect of the invention, even when the high-pressure discharge lamp is turned on, the discharge lamp is stably turned on without a malfunction of the DC power supply unit due to noise of the load current.

According to the invention of claim 7, claim 5
Since the image display device is configured by using the described discharge lamp lighting device as a light source, stable image display is performed under stable irradiation light.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the power supply device and discharge lamp lighting device of the present invention will be described with reference to FIG.

FIG. 1 is a circuit diagram. The power supply device 1 of the present embodiment is configured as a circuit for supplying AC power to the discharge lamp 2 by using the discharge lamp 2 as a load. This power supply device 1 roughly includes a DC power supply unit 4 that outputs DC power based on a commercial AC power supply 3, and an AC conversion that converts the DC power output from the DC power supply unit 4 into AC power and outputs the AC power. It is constituted by connecting the parts 5 in order. The DC power supply unit 4 includes a rectifier circuit 6 that rectifies AC, a chopper circuit 7 that controls electric power for the rectified output, and a smoothing circuit 8. As the rectifier circuit 6, for example, a full-wave rectifier circuit is used. As the chopper circuit 7, for example, a step-down chopper circuit is used, which includes a switching element Q, a rectifying diode D, and a step-down coil L.
Here, as the switching element Q, for example, FET
The semiconductor element is used, and the switching element Q is connected to the first drive control means 9 for driving the switching element Q on and off at a predetermined control frequency f ₁ . An oscillator 10 for defining the control frequency f ₁ is connected to the first drive control means 9. Smoothing circuit 8
For example, a capacitor C such as an electrolytic capacitor
Is used.

Next, the AC converter 5 is the inverter circuit 1
1 is a main component. This inverter circuit 1
1, for example, four switching elements Q _{1 to} Q
A full-bridge type inverter circuit having a switching circuit 12 in which ₄ are bridge-connected is used. FETs are also used as the switching elements Q _{1 to} Q ₄ , for example. For such an inverter circuit 11, a pair of switching elements Q ₁ and Q ₄ located on the opposite side and a pair of switching elements Q ₂ and Q ₃ located on the opposite side are alternately arranged at a predetermined operating frequency f ₂ . Second drive control means 1 for turning on and off and oscillating driving
3 is connected.

Further, a synchronizing means 14 is provided between the second drive control means 13 and the oscillator 10. As the synchronizing means 14, for example, a frequency divider 15 is used. More specifically, the control frequency f ₁ for the switching element Q is set to f ₁ = 51.2 kHz, and the oscillator 10 is set to generate and output a pulse of this control frequency f ₁ . Also, the frequency divider 15
Is used, the operating frequency f ₂ for the inverter circuit 11 is f ₂ = 400 Hz, and it is set so as to be synchronized with the control frequency f ₁ .

Next, the operation of this embodiment will be described.
First, the AC power supplied from the commercial AC power supply 3 is rectified by the rectifier circuit 6 and converted into DC. Further, under the control of the first drive control means 9, the chopper operation by the switching element Q which turns on and off at the control frequency of f ₁ = 51.2 kHz is performed. The output of the switching element Q is stepped down to a predetermined DC voltage level by passing through the step-down coil L after being rectified by the diode D. Further, the smoothing circuit 8 receives a smoothing action by the capacitor C to obtain a DC voltage in which the level fluctuation is small, and the DC voltage is supplied to the inverter circuit 5 as a power source.

In the inverter circuit 11 of the AC conversion unit 5 which receives such DC power from the DC power supply unit 4, under the control of the second drive control means 13, the switching element Q ₁ , at the operating frequency f ₂ = 400 Hz, The pair of Q _{4 and} the pair of switching elements Q ₂ and Q ₃ are alternately turned on and off to perform an oscillating operation, so that the operating frequency is 400H.
It is converted into alternating current power corresponding to z and supplied as a load current across the discharge lamp 2 to maintain lighting.

In such an operation, even if the load current for the discharge lamp 2 generates noise in synchronization with the operating frequency f ₂ due to the oscillation operation of the inverter circuit 11 and enters into the DC power supply unit 4 side, the DC power supply unit 4 Since the switching element Q in _No. 4 is also turned on and off at the control frequency f ₁ synchronized with f ₂ , no malfunction occurs. Therefore, it is possible to avoid the inconvenience that the load current noise causes the chopper circuit 7 and the like to abnormally oscillate and the circuit to be destroyed.

In the present embodiment, the inverter circuit 11
As a full-bridge type inverter circuit is used as the above, when a high-pressure discharge lamp that requires a starter is used as a load, as in the example described below, the starter causes a gap between the electrodes of the high-pressure discharge lamp every time the power is turned on. This is convenient for averaging the electrode wear by alternately switching the direction of the direct current flowing through the electrodes (see JP-A-6-283290).

FIG. 2 shows an embodiment of the discharge lamp lighting device of the present invention.
This will be described below. The same parts as those shown in the above-mentioned embodiment are designated by the same reference numerals, and their explanations are omitted.

FIG. 2 is a schematic circuit diagram mainly showing the starter in the discharge lamp lighting device. In the figure, the discharge lamp 2
A high pressure discharge lamp is used as The high pressure discharge lamp is, for example, a metal halide lamp. Further, the capacitor C shows the smoothing circuit 8, which is the DC power supply unit 4
It shows that it is a DC power output part.

Here, in the case of the discharge lamp 2 of the high-pressure discharge lamp, at the time of starting, it cannot start and light only by supplying AC power of low frequency such as 400 Hz, and therefore, between the DC power supply unit 4 and the discharge lamp 2. Is connected to a starter 21. In this starter 21, the DC power supplied from the DC power supply unit 4 charges the capacitor C ₁ through the resistor r, and when the potential across the capacitor C ₁ rises to a predetermined potential, the thyristor SCR turns on. , Transformer T
_A pulse-like potential is generated on the secondary side via ₁ .
When the capacitor C ₂ is charged through the diode D ₁ by the current generated by the voltage generated on the secondary side of the transformer T _{1 and} the potential across the capacitor C ₂ reaches the discharge potential of the gap GAP, the pulse transformer T ₂ The voltage is boosted by utilizing the current flowing to the side to generate a high-voltage pulse voltage on the secondary side of the pulse transformer T ₂ , and the voltage is applied between the electrodes of the discharge lamp 2.

The starter 21 is provided with a starting switch 22 which is turned on in synchronization with a power switch (not shown) and is controlled so that the turning-on state is continued only at the time of starting.

By applying the high-voltage pulse by the starter 21, the starting operation of the discharge lamp 2 by the high-pressure discharge lamp is performed.

Here, in this embodiment, the pulse transformer T
₂ inputs, that is, the maximum output of the inverter circuit 11 is 2
It is set to be 80 V or less. That is, the no-load open circuit voltage is set so as not to exceed 280 V for any input voltage. The pulse transformer T ₂ that outputs such a high-voltage pulse is EE
A transformer having a structure using an R core is used. According to this, the breakdown voltage required for the semiconductor element such as the switching element Q in the DC power supply unit 4 can be set to 300 V or less. As a result, the ON resistance of the switching element Q and the like is reduced, so that the circuit loss can be suppressed low and the efficiency can be improved. In this embodiment, since the structure using the EER core is used as the pulse transformer T ₂ , the pulse shape generated by winding the primary and secondary windings without folding can be made sharp. Therefore, the start of the discharge lamp 2 is not hindered.

An embodiment of the image display device of the present invention will be described with reference to FIG.

FIG. 3 is a block diagram showing the outline of the image display device. This image display device shows an application example to a liquid crystal video projector, and displays an image on a screen 3.
It is a method of projecting on 1. This image display device is a discharge lamp lighting device 32 having a configuration as shown in FIG. 1 or 2.
And an image data output device 33 and an image forming unit 34. As the image forming unit 34, for example,
An image forming liquid crystal system is used.

In such a structure, the irradiation light from the discharge lamp 2 is given to the image forming section 34. On the other hand, the image data output device 33 supplies image data according to, for example, the NTSC method to the image forming unit 34, and drives it according to the image data. Therefore, the image forming unit 34 forms an image according to the irradiation light of the discharge lamp 2 and the image data given by the image data output device 33. This image is projected on the screen 31.

According to such an image display device, the discharge lamp 2 functioning as a backlight stably illuminates and illuminates without causing malfunction or circuit destruction due to load current noise as described above. Therefore, stable image display is performed.

[0041]

According to the invention described in claim 1, the control means for driving the switching element of the DC power supply section on and off and the operating frequency for driving the switching circuit in the inverter circuit of the AC conversion section on and off are synchronized with each other. Since the noise is synchronized with the operating frequency in the load current, this noise can be synchronized with the on / off timing of the switching element, thus preventing malfunctions and abnormalities in the DC power supply section. Inconveniences such as oscillation and circuit destruction can be avoided.

According to the invention described in claim 2, since the synchronizing means is constituted by the frequency divider, in obtaining the effect of the invention described in claim 1, the operating frequency synchronized with the control frequency can be easily obtained from the control frequency. Can be generated.

According to the invention described in claim 3, since the DC power supply section is formed by the step-down chopper circuit, in addition to the effect of the invention described in claim 1 or 2, the DC power necessary for the AC conversion section is generated. It can be surely supplied.

According to the invention described in claim 4, since the inverter circuit is formed by the full-bridge type inverter circuit, according to the effect of the invention described in any one of claims 1 to 3, the alternating current is normally applied to the load side. In addition to supplying power,
For example, it is also possible to switch the set of switching elements that are turned on in the switching circuit at the time of startup after the power is turned on, and to change the direction of the current applied to the load at the time of startup to prevent damage to both electrodes. It is also possible to equalize.

According to the invention described in claim 5, since the discharge lamp is lit by using the power supply device according to any one of claims 1 to 4, the direct current power supply part caused by the noise of the load current is A discharge lamp lighting device capable of stably lighting a discharge lamp without malfunction can be provided.

According to the sixth aspect of the invention, even when the high pressure discharge lamp is lit, the discharge lamp lighting device is capable of steadily lighting the discharge lamp without malfunction of the DC power supply unit due to noise of the load current. Can be provided.

According to the invention described in claim 7, since the discharge lamp lighting device according to claim 5 is used as a light source, it is possible to provide an image display device capable of performing stable image display under stable irradiation light.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a power supply device and a discharge lamp lighting device of the present invention.

FIG. 2 is a schematic circuit diagram showing an embodiment of a discharge lamp lighting device of the present invention.

FIG. 3 is a block configuration diagram showing an embodiment of an image display device of the present invention.

[Explanation of symbols]

1 Power Supply Device 2 Discharge Lamp 4 DC Power Supply Unit 5 AC Conversion Unit 7 Chopper Circuit 9 First Drive Control Means 11 Inverter Circuit 12 Switching Circuit 13 Second Drive Control Means 14 Synchronizing Means 15 Divider 21 Starter 32 Discharge Lamp Lighting device 33 Image data output device 34 Image forming unit Q switching element f ₁ Control frequency f ₂ Operating frequency

Claims (7)

[Claims] 1. A direct-current power supply unit that includes a switching element that is switched based on a control frequency and outputs direct-current power; a first drive control means that drives the switching element on and off at a control frequency; and is switched based on an operating frequency. An AC converter that has an inverter circuit including a switching circuit that converts the DC power output from the DC power supply unit to AC power and supplies the AC power to a load; a second drive that drives the switching circuit on and off at an operating frequency. A power supply device comprising: control means; synchronization means for synchronizing a control frequency and an operating frequency. 2. The power supply device according to claim 1, wherein the synchronizing means comprises a frequency divider that divides the control frequency to obtain an operating frequency. 3. The DC power supply unit has a step-down chopper circuit including a switching element;
Alternatively, the power supply device according to item 2. 4. The inverter circuit is a full-bridge type inverter circuit;
The power supply device according to any one of 1. 5. A discharge lamp lighting device, comprising: the power supply device according to claim 1; and a discharge lamp as a load. 6. The discharge lamp is a high pressure discharge lamp; and the discharge lamp has a starter connected between the DC power supply unit and the discharge lamp to apply a high pressure pulse when the discharge lamp is started. 5. The discharge lamp lighting device according to item 5. 7. A discharge lamp lighting device according to claim 5, an image data output device for outputting image data of an image to be displayed, and an irradiation light of the discharge lamp and image data output by the image data output device. And an image forming unit for forming an image according to image data;