JP2004119032A - Discharge lamp lighting device and lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device and an illumination device that has a boosting and deboosting circuit wherein the voltage to appear in a switching element can be made lower even in impressing of a surge voltage. <P>SOLUTION: The capacity of a capacitor C1 connected in parallel to the output edge of a rectifying circuit 3 which converts AC voltage into DC voltage, is set as 1% or more against the capacity of a smoothing capacitor C2 employed at the boosting and deboosting circuit 4 to boost or deboost DC voltage obtained in the rectifying circuit 3. By this, the voltage impressed on the switching element FET of the boosting and deboosting circuit 4 is suppressed low. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device for lighting a discharge lamp at a high frequency and a lighting device.
[0002]
2. Description of the Related Art In general, a discharge lamp lighting device includes an LC resonance type inverter circuit. When the discharge lamp is started, the inverter circuit starts oscillating at a high frequency, and gradually lowers the frequency so that the resonance frequency of the LC resonance circuit is reduced. Approach. Thereby, the secondary voltage of the inverter circuit increases, and when the secondary voltage reaches the starting voltage of the discharge lamp, the discharge lamp starts discharging and lights up. Once the discharge lamp is lit, the frequency of the inverter circuit is further reduced, and the discharge lamp is continuously lit at a stable lighting frequency (frequency at lighting).
[0003]
In the case of a high-pressure discharge lamp, a transition from a glow discharge to an arc discharge is started, so that a high secondary voltage needs to be applied for a predetermined time for the arc discharge transition. Therefore, the booster circuit provided before the inverter circuit controls the output voltage value at the start of the high-pressure discharge lamp to a higher output voltage value than at the time of lighting, so that even when the inverter circuit generates a high secondary voltage, Is kept low (see Patent Document 1).
[0004]
On the other hand, when a surge voltage is superimposed on the power supply voltage of the discharge lamp lighting device, an overvoltage appears on the switch element. Therefore, it is necessary to take measures to prevent the switch element from being destroyed even when the surge voltage is applied. In the case of a discharge lamp lighting device having a booster circuit, a smoothing capacitor is connected in parallel with a switch element via a diode to help absorb surge voltage, but a discharge lamp lighting device using a step-up / down circuit In the case of (1), since the smoothing capacitor is not connected in parallel with the switch element, it does not help to absorb the surge voltage. Therefore, in the case of a discharge lamp lighting device using a step-up / step-down circuit, the switch element of the step-up / step-down circuit needs to be a high withstand voltage switch element.
[0005]
[Patent Document 1]
JP 2000-58284 A
However, a switch element having a high withstand voltage has a large on-resistance and a large switching loss, so that the circuit efficiency is deteriorated. Further, the addition of a surge absorbing element (varistor) or the like causes an increase in circuit size and cost.
[0007]
An object of the present invention is to provide a discharge lamp lighting device and a lighting device having a step-up / step-down circuit capable of reducing a voltage appearing at a switch element even when a surge voltage is applied.
[0008]
According to a first aspect of the present invention, there is provided a discharge lamp lighting apparatus comprising: a rectifier circuit for converting an AC voltage into a DC voltage; and a buck-boost circuit for raising and lowering the DC voltage obtained by the rectifier circuit. An inverter circuit for supplying high-frequency power to the discharge lamp through a resonance circuit based on the voltage stepped up and down by the step-up / step-down circuit; and an inverter connected in parallel to an output terminal of the rectifier circuit and used for the step-up / step-down circuit. A capacitor set to a capacity of 1% or more with respect to the capacity of the smoothing capacitor.
[0009]
In the present invention and the following inventions, definitions and technical meanings of terms are as follows unless otherwise specified.
[0010]
The rectifier circuit is composed of, for example, a rectifier of a diode bridge, and converts a commercial AC voltage into a DC voltage. The step-up / step-down circuit is for stepping up / down the DC voltage obtained by the rectifier circuit, and is constituted by a step-up / step-down chopper circuit. The input stage of the buck-boost circuit has a capacitor connected in parallel to the rectifier, and the output stage has a smoothing capacitor connected in parallel to the inverter circuit. A capacitor connected to the output terminal of the rectifier bypasses high frequencies and absorbs applied surge voltage. The capacity of the capacitor is set to 1% or more of the capacity of the smoothing capacitor. This suppresses the switching element to a voltage that does not destroy the switching element when a surge voltage is applied.
[0011]
The inverter circuit supplies high-frequency power to the discharge lamp via a resonance circuit based on the DC voltage obtained by the step-up / step-down circuit, and has, for example, two switch elements, and receives a DC voltage from a rectifier circuit. A half-bridge type that alternately turns on and off two switch elements to output a high-frequency voltage to the output side, and supplies high-frequency power to a discharge lamp connected to the output side of the inverter circuit via a resonance circuit .
[0012]
The discharge lamp includes a mercury lamp, a metal halide lamp, a high-pressure sodium lamp and the like, and also includes a ceramic discharge lamp using an alumina tube as an arc tube. The resonance circuit includes an inductor and a capacitor, and generates a high voltage near the resonance frequency of the resonance circuit according to the frequency of the high frequency voltage input from the inverter circuit.
[0013]
According to the present invention, since the capacity of the capacitor connected in parallel to the output terminal of the rectifier is set to 1% or more of the capacity of the smoothing capacitor used in the step-up / step-down circuit, when a surge voltage is applied. Even in this case, the voltage applied to the switch element can be suppressed low.
[0014]
A lighting device according to a second aspect of the present invention is characterized by comprising: the discharge lamp lighting device according to the first aspect; and a fixture main body to which a discharge lamp to be lighted by the discharge lamp lighting device is mounted. According to the present invention, a lighting device having the effect of claim 1 is obtained.
[0015]
Embodiments of the present invention will be described below. FIG. 1 is an explanatory view of a discharge lamp lighting device according to a first embodiment of the present invention. FIG. 1 (a) is a block diagram, and FIG. 1 (b) is a circuit diagram of a rectifier circuit and a step-up / step-down circuit portion. It is.
[0016]
As shown in FIG. 1A, a power supply voltage from a commercial AC power supply 1 is input to a noise filter circuit 2 and then to a rectifier circuit 3. The rectifier circuit 3 is configured by a rectifier of a diode bridge, and converts an AC voltage into a DC voltage. The DC voltage obtained by the rectifier circuit is input to the step-up / step-down circuit 4, where the DC voltage is stepped up and down. Assuming that the output voltage of the step-up / step-down circuit 4 is 270 V DC, the step-up / step-down circuit 4 performs a step-up operation at 100 V AC and a step-down operation at 240 V AC, and can supply a constant DC voltage to the inverter circuit 6 over a range of 100 V to 240 V AC. it can.
[0017]
The DC voltage stepped up / down by the step-up / step-down circuit 4 is input to the inverter circuit 6, converted into a high-frequency voltage by turning on / off a switch element of the inverter circuit 6, and supplying high-frequency power to the discharge lamp 5 via the resonance circuit 7. The inverter circuit 6 has two switch elements, and is configured as a half-bridge type that receives the DC voltage from the rectifier circuit 4 as input and alternately controls the two switch elements to turn on and off to output a high-frequency voltage to the output side. . The resonance circuit 7 includes an inductor and a capacitor. When the discharge lamp 5 is started, a high voltage is generated near the resonance frequency of the resonance circuit 7 in accordance with the frequency of the high-frequency voltage input from the inverter circuit 6 to discharge. The lamp 5 is turned on.
[0018]
As shown in FIG. 1B, the rectifier circuit 3 is bridge-connected by four diodes D1 to D4, and a capacitor C1 is connected in parallel to an output terminal of the rectifier circuit 3. The step-up / step-down circuit 4 includes an inductor L, a diode D5, and a switch element FET, and the gate control unit 8 controls the switch element FET on-time (duty control). A smoothing capacitor C2 is connected to the output stage of the step-up / step-down circuit 4 in parallel with the inverter circuit 6.
[0019]
Here, the capacitance of the capacitor C1 is set so as to be a voltage that does not destroy the switch element FET of the step-up / step-down circuit 4 when a surge voltage is applied. Hereinafter, selection of the capacitance of the capacitor C1 will be described.
[0020]
Normally, when a discharge lamp 5 having a load of 35 W or less is used as a load, the capacity of the smoothing capacitor C2 of the step-up / step-down circuit 4 is selected to be about 22 μF or less, and a capacitor having a capacity smaller than 22 μF is set for downsizing. . On the other hand, in the discharge lamp 5 of 35 W or more, the capacitor of the smoothing capacitor C2 of the step-up / step-down circuit 4 is selected to be a capacitor of 22 μF or more. In the discharge lamp lighting device having a discharge lamp 5 of 35 W or more as a load, harmonic regulation is performed. Therefore, the case where the capacitance of the smoothing capacitor C2 is 22 μF and the capacitance of the capacitor C1 is changed will be examined.
[0021]
FIG. 2 shows the voltage across the switch element FET of the step-up / step-down circuit 4 when the voltage of the step-up / step-down circuit 4 is 6 kV and the voltage surge is 6 μV when the capacity of the smoothing capacitor C2 is 22 μF and the capacity of the capacitor C1 is changed. FIG. 5 is a characteristic diagram of V1 and a capacitance ratio C1 / C2 of the capacitance of the capacitor C1 and the capacitance of the smoothing capacitor C2. As can be seen from FIG. 2, the voltage applied to the voltage V1 across the switch element FET decreases as the capacitance ratio C1 / C2 increases, that is, as the capacitance of the capacitor C1 approaches the capacitance of the smoothing capacitor C2.
[0022]
FIG. 3 is a waveform diagram of the input current I of the discharge lamp lighting device when the capacitance ratio C1 / C2 between the capacitance of the capacitor C1 and the capacitance of the smoothing capacitor C2 is changed. S1 is the waveform of the input current I when the capacitance of the capacitor C1 is 10 μF (C1 / C2 = 45%), and S2 is the waveform of the input current I when the capacitance of the capacitor C1 is 2.2 μF (C1 / C2 = 10%). A waveform S3 is a waveform of the input current I when the capacitance of the capacitor C1 is 0.1 μF (C1 / C2 = 0.45%). As can be seen from FIG. 3, when the capacitance of the capacitor C1 is 0.1 μF (C1 / C2 = 0.45%) or 2.2 μF (C1 / C2 = 10%), the waveform of the input current I is good. Although satisfying the harmonic specification, when the capacitance of the capacitor C1 is 10 μF (C1 / C2 = 45%), the waveform of the input current I is considerably accompanied by distortion.
[0023]
From the above, when the discharge lamp 5 has a power of 35 W or less, there is no harmonic regulation. Therefore, taking into account the withstand voltage of the switch element FET, the capacity of the capacitor C1 is larger than the capacity of the smoothing capacitor C2. The capacity is selected so that the capacity ratio C1 / C2 is 1% or more. This makes it possible to suppress the voltage of the switch element FET of the step-up / step-down circuit 4 at the time of application of the surge voltage to the breakdown voltage or less.
[0024]
On the other hand, when the discharge lamp 5 has a power of 35 W or more, there is a harmonic regulation. Therefore, taking into account the withstand voltage and harmonics of the switching element FET, the capacity of the capacitor C1 is larger than the capacity of the smoothing capacitor C2. , The capacity ratio C1 / C2 is selected to be 1% to 10%. This makes it possible to suppress the voltage applied to the switch element FET of the step-up / step-down circuit 4 when the surge voltage is applied to be equal to or lower than the withstand voltage, and to suppress the harmonics since the input current waveform becomes substantially sinusoidal.
[0025]
FIG. 4 is an explanatory diagram of a lighting device according to a second embodiment of the present invention. FIG. 4 shows a case where the discharge lamp 5 is a high-pressure discharge lamp. The discharge lamp lighting device 9 according to the first embodiment constitutes an illumination device together with the fixture body 10 to which the discharge lamp 5 is mounted. As shown in FIG. 4, the discharge lamp 5 is mounted on the socket 11 of the appliance body 10 and is turned on by the discharge lamp lighting device 9. Light from the lit discharge lamp 5 is reflected by the reflector 12 on the front side and is emitted through the front glass 13. According to the lighting device of the second embodiment, a lighting device having the effect of the discharge lamp lighting device 9 of the first embodiment can be obtained.
[0026]
As described above, according to the first aspect of the present invention, it is not necessary to increase the withstand voltage of the switch element of the step-up / step-down circuit, so that small components can be used and the circuit efficiency can be improved. it can. Also, since there are no special additional parts, cost increase is small. Further, according to the invention of claim 2, a lighting device having the effect of claim 1 is obtained.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a discharge lamp lighting device according to a first embodiment of the present invention.
FIG. 2 shows the voltage across the switch element FET of the step-up / step-down circuit 4 when a voltage surge of 1.2 μs / 48 μs and 6 kV voltage surge is applied to the step-up / step-down circuit 4 when the capacity of the smoothing capacitor C2 is 22 μF and the capacity of the capacitor C1 is changed. FIG. 6 is a characteristic diagram of V1 and a capacitance ratio C1 / C2 of the capacitance of the capacitor C1 and the capacitance of the smoothing capacitor C2.
FIG. 3 is a waveform diagram of the input current I of the discharge lamp lighting device when the capacitance ratio C1 / C2 between the capacitance of the capacitor C1 and the capacitance of the smoothing capacitor C2 is changed.
FIG. 4 is an explanatory diagram of a lighting device according to a second embodiment of the present invention.
[Description of Signs] 1 ... AC power supply, 2 ... Noise filter circuit, 3 ... Rectifier circuit, 4 ... Step-up / step-down circuit, 5 ... Discharge lamp, 6 ... Inverter circuit, 7 ... Resonant circuit, 8 ... Gate control unit, 9 ... Discharge lamp lighting device, 10: appliance body, 11: socket, 12: reflector, 13: front glass

Claims (2)

A rectifier circuit for converting an AC voltage to a DC voltage;
A buck-boost circuit for buck-boost the DC voltage obtained by the rectifier circuit;
An inverter circuit for supplying high-frequency power to the discharge lamp via a resonance circuit based on the voltage stepped up and down by the step-up / step-down circuit;
A capacitor connected in parallel to an output terminal of the rectifier circuit and having a capacitance set to 1% or more of a capacitance of a smoothing capacitor used in the buck-boost chopper;
A discharge lamp lighting device comprising: A discharge lamp lighting device according to claim 1;
An appliance body on which a discharge lamp to be lit by the discharge lamp lighting device is mounted;
A lighting device comprising:

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