JP2007299585A - Discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device capable of avoiding large size of a filament heating transformer by controlling filament heating current according to the operating mode of a discharge lamp. <P>SOLUTION: The discharge lamp lighting device is equipped with a resonance circuit system RC which includes a power supply DC, an inverter means INV, and a discharge lamp DL and is energized by the inverter means and a filament heating circuit FHC which includes a filament heating transformer FT to input the output of the inverter means and to output filament heating current and a switching means Q3 having an impedance to control input of the filament heating transformer and in which the switching means controls input to the filament heating transformer so that a filament heating current corresponding to the operating mode of the discharge lamp may be supplied. The DC current flowing to the filament heating transformer at the time of switching on of the switching means is reduced by resonance of the filament heating circuit and the resonance circuit system. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a discharge lamp lighting device including a filament heating transformer.

  A preheating circuit comprising a capacitor, a preheating transformer and switch means is connected to the output terminal of the inverter circuit for lighting the discharge lamp, and a preheating control circuit for controlling the switch means of the preheating circuit is provided. A discharge lamp lighting device is known in which the switch means is controlled by a preheating control signal output from the control circuit corresponding to the degree of light so as to control the filament current of the discharge lamp (see, for example, Patent Document 1). .)

JP 2005-235619 A

  When a discharge lamp is turned on at a high frequency using an inverter circuit as in the discharge lamp lighting device described in Patent Document 1, a discharge lamp and a resonant circuit system including its current limiting impedance are connected to the output terminal of the inverter circuit. The discharge lamp is connected to the inverter circuit through this resonance circuit system. Moreover, it is common to use a semiconductor switch as a switching means of the preheating circuit. Many semiconductor switches, particularly MOS-FETs, have impedances that cannot be ignored.

  However, in the discharge lamp lighting device described in Patent Document 1, since the direct current flows into the preheating circuit while being superimposed on the high frequency output of the inverter circuit while the switching means of the preheating circuit is on, It was found that there was a problem that the preheating transformer was enlarged because it was necessary to avoid saturation.

As a result of investigation and examination by the present inventor to solve this problem, the problem caused by the DC current superposition is that the preheating circuit as a whole as viewed from the input end including the impedance of the resonance circuit system and the impedance of the switching means. It has been found that this is caused by a transient resonance phenomenon when the switching means is on. In the discharge lamp lighting device described in Patent Document 1, the frequency of the output voltage V _HF of the inverter circuit shown in FIG. 9A is 50 kHz, for example, and the switching means of the preheating circuit as shown in FIG. on the gate drive signal V _G, the period T oFF is 1 second, when the on-duty 30%, transient direct current I _DC to the preheating current I _f, as shown in FIG. 9 (c) is outputted from the inverter circuit The current flows in the primary winding of the preheating transformer so as to be superimposed on the generated high frequency current.

  An object of the present invention is to provide a discharge lamp lighting device capable of controlling the filament heating current to a required level in accordance with the operation mode of the discharge lamp and avoiding an increase in the size of the filament heating transformer.

  A discharge lamp lighting device according to the present invention includes a power source that generates a direct current output; an inverter unit that includes a switching element and converts the direct current output of the power source into an alternating current by a switching operation; and a discharge lamp that includes a filament electrode. A resonance circuit system energized by the output; a filament heating transformer for inputting the output of the inverter means and outputting a filament heating current to the filament electrode of the discharge lamp; and an impedance control for controlling the input of the filament heating transformer And a filament heating circuit for controlling an input to the filament heating transformer so that a filament heating current corresponding to the operation mode of the discharge lamp is supplied, and impedance and resonance of the filament heating circuit Times It is characterized by being configured to reduce the direct current flowing through the filament heating transformer when the switching means by the resonance between the impedance of the system.

  In the present invention and each of the following inventions, the definitions and technical meanings of terms are as follows unless otherwise specified.

  The specific configuration of the power source that generates the DC output is not particularly limited as long as it generates the DC output. Therefore, for example, it is allowed to be a battery power source, a capacitor, a rectified DC power source, or the like. In addition, it is allowed to include a DC-DC conversion circuit such as a chopper circuit in order to input a DC voltage of a desired voltage to the inverter means and adjust or adjust the power supply voltage fluctuation.

  The inverter means is a circuit means that includes a switching element and converts direct current to alternating current by the switching operation of the switching element, and various known circuit type inverters can be employed. In the present invention, the output frequency of the inverter means is not particularly limited. However, when a discharge lamp such as a fluorescent lamp is lit at a high frequency, the luminous efficiency is increased, so that a high frequency is generally preferable. The output voltage is allowed to be output as a rectangular wave. Further, in order to dimm the discharge lamp, it is allowed to make the output frequency of the inverter means variable.

  Further, the inverter means can be configured to include a drive circuit for driving the switching means and a control circuit for controlling the drive circuit as is well known. Note that a microcomputer can be used for the control circuit as desired.

  The resonance circuit system is configured such that a discharge lamp that is lit is connected to the resonance circuit system, and the output of the inverter means is applied. The output of the applied inverter means is converted into a waveform by resonance, and the degree of resonance is adjusted to discharge the required voltage according to the operation mode of the discharge lamp, for example, preheating, starting and lighting or dimming. In addition to being applied to the lamp, a current limiting impedance is applied to the discharge lamp current during lighting. The waveform conversion is generally configured such that when the rectangular wave voltage of the inverter output is applied to the discharge lamp, it is converted to a sine wave.

  The filament heating circuit includes a filament heating transformer and switching means. The filament heating transformer inputs the output of the inverter means and outputs a filament heating current to the filament electrode of the discharge lamp.

  The switching means controls the input of the filament heating transformer by turning it on and off, and is optimal for the operation mode of the discharge lamp, for example, the preheating, starting and lighting operation stages and lighting modes, i.e. all light and dimming. Control is performed so that the filament heating current can be supplied to the filament electrode of the discharge lamp. In order to control the switching means, for example, a microcomputer of an inverter means can be used, or a dedicated control circuit can be provided.

  The filament heating circuit is configured to reduce the direct current flowing through the filament heating transformer when the switching means is turned on by resonance between the impedance of the switching means that cannot be ignored and the impedance of the resonance circuit system. In the present invention, the configuration for reducing the direct current is not particularly limited, but it is effective when configured as shown in the embodiments of the invention described later.

  Note that the impedance of the switching means cannot be ignored as follows. That is, when the configuration is merely for optimizing the filament heating current with respect to the lamp current as in Patent Document 1, the impedance of the switching means and the impedance of the resonance circuit system resonate to cause transient vibration. The impedance is such that As a result, a direct current is transiently superimposed on the input current of the filament heating transformer. When the direct current is superimposed on the current flowing through the filament heating transformer, it is necessary to make the core large.

  In the present invention, the filament heating circuit can include a filament heating transformer and switching means, and can connect a capacitor in series with the primary winding of the filament heating transformer.

  Next, main aspects included in the present invention will be described.

(First aspect)
In the first aspect, the switching means is turned off until the peak phase of the first vibration waveform in the transient DC current generated by the resonance between the impedance of the filament heating circuit and the impedance of the resonance circuit system viewed from the input end. The filament heating circuit is configured. Note that the ON start point of the switching means may be before or after the output voltage of the inverter means is applied between the input ends of the filament heating circuit.

  When the switching means is turned on and the DC current resulting from resonance between the impedance of the filament heating circuit and the impedance of the resonance circuit system is superimposed on the filament heating transformer beyond the peak phase, the effective value of the DC current increases. On the other hand, in the first aspect, since the switching means is turned off before the effective value increases, the effective value of the direct current superimposed on the output of the inverter means can be suppressed to a small value.

(Second aspect)
In the second aspect, the filament heating circuit is controlled so that the switching means is turned on before the output voltage of the inverter means is applied between the input ends of the filament heating circuit and turned off before the output voltage becomes zero. To do.

  In the second aspect, the effective value of the direct current superimposed on the output of the inverter means can be suppressed to a small value as in the first aspect. The on / off control of the switching means is preferably synchronized with the output frequency of the inverter means, but may be asynchronous if desired.

  In order to turn on the switching means before the output voltage of the inverter means is applied, for example, the following configuration may be used. For example, when the drive signal of the switching element of the inverter means is digitally controlled by the microcomputer, the number of steps of the counter in the microcomputer for forming the drive signal to be supplied to the switching means of the filament heating circuit is determined by the switching element of the inverter means. Is set to be smaller than the number of steps for forming the drive signal supplied to. Further, when the drive signal is controlled in an analog manner by clamping the triangular wave at a predetermined phase, the gate signal clamp voltage supplied to the switching means Q3 of the filament heating circuit FHC is used for the gate signal for the switching element of the inverter means INV. Less than the clamp voltage.

(Third aspect)
According to a third aspect, the filament heating circuit changes the on-duty by simultaneously changing the phase before and after the rising point of the output voltage of the inverter means, and according to the dimming degree of the discharge lamp. The filament heating amount is set to a required value.

  In the third aspect, the filament heating amount can be set to a required value according to the dimming degree of the discharge lamp, and the effective of the direct current superimposed on the output of the inverter means is the same as in the second aspect. The value can be suppressed to a small value.

(Fourth aspect)
In the fourth aspect, the switching means of the filament heating circuit is constituted by a MOS-FET.

  Since the MOS-FET has capacitance between its drain and source, between its drain and gate, and between its gate and source, one having an impedance of, for example, about 1000 pF is used. Therefore, when a MOS-FET having such an impedance is used as the switching means of the filament heating circuit, if the output frequency of the inverter means is about 50 kHz, for example, the impedance of the resonant circuit system and the impedance of the MOS-FET resonate. Transient direct current is superimposed on the inverter output and flows to the filament heating transformer.

  Therefore, by selectively adopting the first to third aspects according to the present invention, it is possible to effectively suppress the superposition of direct current.

(5th aspect)
In the fifth aspect, a MOS-FET having a small capacitance value of, for example, about 100 pF is employed as the switching element of the filament heating circuit in the present invention.

  According to the fifth aspect, since the MOS-FET having a small impedance is employed as the switching means, when the fifth aspect is introduced in the present invention and the first to fourth aspects, the DC current is further superimposed. Can be reduced. Further, if desired, the above-described MOS-FET is merely used as a switching means, and there is an effect of suppressing the superposition of direct current to some extent without adopting the first to fourth modes.

  According to the present invention, it is possible to control the filament heating current in accordance with the operation mode of the discharge lamp and to suppress the direct current flowing through the filament heating transformer, thereby providing a discharge lamp lighting device that avoids an increase in the size of the filament heating transformer. Can be

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

    1 to 4 show a first embodiment of a discharge lamp lighting device according to the present invention. FIG. 1 is a block circuit diagram, FIG. 2 is a circuit diagram, FIG. 3 is an equivalent circuit diagram of switching means, and FIG. It is a voltage and current waveform diagram. Note that the first embodiment corresponds to the first aspect of the present invention.

  As shown in FIG. 1, the discharge lamp lighting device of the present invention includes a power source DC, inverter means INV, resonance circuit system RC, and filament heating circuit FHC.

  The power source DC outputs a direct current and supplies it to inverter means INV described later. In the first embodiment, the power source DC is a rectified DC power source.

  The inverter means INV includes a switching element that performs a switching operation, and converts direct current into alternating current. In the first embodiment, the inverter means INV is composed of a half-bridge inverter having a pair of switching elements Q1 and Q2 that are connected in series to the power source DC and alternately switched as shown in FIG. Yes. Note that the switching of the pair of switching elements Q1 and Q2 is controlled by a gate drive circuit and a control circuit mainly composed of a microcomputer (not shown).

  Then, the inverter means INV outputs an alternating current having a voltage equal to the power supply voltage, for example, a high frequency alternating voltage.

  The resonant circuit system RC constitutes a load circuit, and the output of the inverter means INV is applied thereto, and the discharge lamp DL is connected. Then, waveform conversion and a required voltage to be applied to the discharge lamp DL are formed by resonance. In the first embodiment, the resonance circuit system RC includes an inductor L1 and capacitors C1 and C2, as shown in FIG.

  The inductor L1 is connected in series between the inverter means INV and the discharge lamp DL, and also acts as a current limiting impedance for the lamp current. The capacitor C1 is connected in series between the inverter means INV and the discharge lamp DL, and mainly functions as a DC cut capacitor. The capacitor C2 is connected in parallel to the discharge lamp DL and at the same time in series with the inductor L1.

  Thus, mainly the inductor L1 and the capacitor C2 of the resonance circuit system RC are in series resonance, and at that time, the terminal voltage of the capacitor C2 is applied between the pair of filament electrodes E and E of the discharge lamp DL. In addition, the degree of resonance of the resonance circuit RC changes as the output frequency of the inverter means INV changes according to the operation mode of the discharge lamp DL. As a result, the voltage applied between the pair of filament electrodes E, E of the discharge lamp DL appropriately changes according to the operation mode.

  The discharge lamp DL is preferably a fluorescent lamp, and includes a discharge vessel, a pair of filament electrodes E and E sealed inside both ends thereof, a discharge medium sealed inside the discharge vessel, and a discharge vessel. And a phosphor layer formed on the inner surface.

  The filament heating circuit FHC includes a filament heating transformer FT and switching means Q3, and controls the filament heating current supplied to the discharge lamp DL in accordance with the operation mode of the discharge lamp DL. In the first embodiment, the filament heating circuit FHC includes a filament heating transformer FT, a series circuit of a switching means Q3 and a capacitor C3, and a control circuit CC as shown in FIG. The series circuit is connected between the output terminals of the inverter means INV.

  The filament heating transformer FT includes a primary winding wp, a pair of secondary windings ws1 and ws2, and a core K. The primary winding wp is wound around the core K, and both ends thereof are connected in series with the switching means Q3 and the capacitor C3. The pair of secondary windings ws1 and ws2 are wound around the core K and are transformer-coupled to the primary winding wp, and are connected to both ends of the pair of filament electrodes E and E of the discharge lamp DL. .

  Then, when the primary winding wp is connected between the output terminals of the inverter means INV via the capacitor C3 and the switching means Q3, and the switching means Q3 is turned on, the filament heating transformer FT is operated and a pair of 2 Since a filament heating voltage is induced between both ends of the next windings ws1 and ws2, a filament heating current flows through the pair of filament electrodes E and E.

In the first embodiment, the switching means Q3 is composed of a MOS-FET. As shown in FIG. 3, the MOS-FET of the switching means Q3 has a capacitance C _D-S between the drain D and the source S, a capacitance C _D- G between the drain D and the gate _G , and a gate G-source S. have a capacitance C _G-S during have equal capacitance C _FET to the combined value of each electrostatic capacitance between Accordingly drain D- source S. Thus, the switching means Q3 would have an impedance based on the output frequency of the capacitance C _FET and inverter means INV.

The control circuit CC includes a lamp current detection circuit I _L D, a filament current detection circuit I _f D, and a switching control circuit SC. The lamp current detection circuit I _L D detects the lamp current flowing through the discharge lamp DL. The filament current detection circuit I _f D detects the filament current flowing into the filament electrode E. The switching control circuit SC includes a filament heating amount determination circuit that determines a required filament heating amount based on detection outputs of the lamp current detection circuit I _L D and the filament current detection circuit I _f D, and a gate corresponding to the required filament heating amount. A gate drive circuit that generates a drive signal and supplies it to the switching means Q3 is included.

  Next, the circuit operation in the first embodiment will be described.

In the waveform diagram shown in FIG. 4, (a) shows the waveform of the high frequency output voltage V _HF of the inverter means INV, (b) shows the waveform of the gate drive signal V _GQ3 of the switching means Q3, and (c) shows the filament heating current _If. The waveforms are shown respectively. As can be understood from FIGS. 4B and 4C, in the first embodiment, the filament heating circuit FHC can understand the ON period of the switching means Q3 shown in FIG. Thus, the direct current I _DC superimposed on the current flowing by the high frequency output reaches its peak phase in the first half cycle of the transient vibration waveform accompanying the resonance between the impedance of the switching means Q3 and the impedance of the resonance circuit RC. It is limited to flow only for a short period of time. The switching cycle of the switching means Q3 is set to about 10 times the switching cycle of the inverter means INV.

For this reason, before the effective value of the direct current superimposed on the high frequency output voltage _VHF becomes large, the gate drive signal V _GQ3 is turned off and the direct current is cut off, so that the effective value of the superimposed direct current is reduced. If the DC current is not interrupted in the middle, it starts to flow from the moment when the switching means Q3 is turned on, and gradually decreases by damped vibration.

On the other hand, the filament heating amount is shown in FIG. 4B so that the switching control circuit SC is supplied with the optimum filament heating current in accordance with the detection outputs of the lamp current detection circuit I _L D and the filament current detection circuit I _f D. By changing the on-duty of the gate drive signal _VGQ3 of the switching means Q3 shown, control can be performed regardless of the switching cycle.

  Therefore, according to the first embodiment, it can be understood that both the reduction of the lamp current detection circuit ID and the filament current detection circuit VD DC current and the optimization of the filament heating amount can be achieved.

  Hereinafter, other embodiments of the present invention will be described with reference to FIGS. In addition, in each figure, the same code | symbol is attached | subjected about the part same as FIG. 4, and description is abbreviate | omitted.

    FIG. 5 is a voltage and current waveform diagram of each part showing the second embodiment in the discharge lamp lighting device of the present invention. The present embodiment corresponds to a modification of the first embodiment.

  That is, in the second embodiment, the switching cycle of the switching means Q3 of the filament heating circuit FHC is set to be as small as about five times the switching cycle of the inverter means INV. For this reason, since the time during which the direct current flows is further shortened as compared with the first embodiment, the superimposition of the direct current is further reduced.

    FIG. 6 is a voltage and current waveform diagram of each part showing the third embodiment in the discharge lamp lighting device of the present invention. This embodiment corresponds to the second aspect of the present invention.

  That is, in the second embodiment, the switching means Q3 of the filament heating circuit FHC is turned on before the output voltage of the inverter means INV is turned on.

  Thus, according to the third embodiment, since the period in which the direct current is generated is shortened, the superposition of the direct current is reduced.

    FIG. 7 is a voltage and current waveform diagram of each part showing the fourth embodiment in the discharge lamp lighting device of the present invention. The present embodiment corresponds to a modification of the third embodiment.

  That is, in the fourth embodiment, when the filament heating amount of the filament heating circuit FHC is controlled so as to be optimized according to the operation mode of the discharge lamp DL, the on-duty is changed by changing the timing when the switching means Q3 is turned on. Adjust. FIG. 7 (b) shows a state in which the on-duty of the switching means Q3 is relatively small. However, as shown in FIG. 7 (c), the on-timing phase is advanced as shown in FIG. The duty can be increased.

  Thus, according to the fourth embodiment, since the on-duty of the switching means Q3 can be changed while the DC current generation period is kept constant in a short state, even if the filament heating amount changes. It can be kept constant in a state where the superposition of the direct current is reduced.

    FIG. 8 is a voltage and current waveform diagram of each part showing the fifth embodiment in the discharge lamp lighting device of the present invention. This embodiment corresponds to the third aspect of the present invention.

  That is, in the fifth embodiment, the filament heating amount of the filament heating circuit FHC is controlled to be optimized according to the dimming degree of the discharge lamp DL. Then, as indicated by arrows pointing in opposite directions on the phase axis in FIG. 8 (b), the on-timing of the switching means Q3 is changed in the advance direction around the phase at the rising point in the output voltage of the inverter means INV. At the same time, the on-duty of the switching means Q3 is set by changing the off timing in the delay direction. Thereby, it can control to the optimal filament heating amount.

  Thus, according to the fifth embodiment, the on-duty of the switching means Q3 can be set to an optimum value according to the dimming degree while the period in which the direct current is generated is maintained in a relatively short state. Depending on the degree of dimming, the filament heating amount can be controlled to an optimum state, and at the same time, the superposition of direct current can be reduced.

The block circuit diagram which shows 1st Embodiment in the discharge lamp lighting device of this invention Same circuit diagram Similarly equivalent circuit diagram of switching means Similarly, voltage and current waveforms for each part Voltage and current waveform diagram of each part showing the second embodiment in the discharge lamp lighting device of the present invention Voltage and current waveform diagram of each part showing the third embodiment in the discharge lamp lighting device of the present invention Voltage and current waveform diagram of each part showing the fourth embodiment in the discharge lamp lighting device of the present invention Voltage and current waveform diagram of each part showing the fifth embodiment in the discharge lamp lighting device of the present invention Voltage and current waveform diagram of each part in the discharge lamp lighting device described in Patent Document 1

Explanation of symbols

DC ... power source, INV ... inverter means, RC ... resonance circuit system, FHC ... filament heating circuit, Q1, Q2 ... switching element, DL ... discharge lamp, L1 ... inductor, C1, C2 ... capacitor, FT ... filament heating transformer, CC ... Control circuit, SC ... Switching control circuit, I _L D ... Lamp current detection circuit, I _f D ... Filament current detection circuit

Claims (5)

A power supply that produces a DC output;
Inverter means comprising a switching element and converting the direct current output of the power source into alternating current by the switching operation of the switching element;
A resonant circuit system to which a discharge lamp having a filament electrode is connected and to which the output of the inverter means is applied;
An operation mode of the discharge lamp including a filament heating transformer for inputting an output of the inverter means and outputting a filament heating current to the filament electrode of the discharge lamp and a switching means having an impedance to control the input of the filament heating transformer A filament heating circuit in which the switching means controls the input to the filament heating transformer so that a filament heating current in accordance with is supplied;
The discharge lamp lighting device is characterized in that the direct current flowing through the filament heating transformer is reduced when the switching means is turned on by resonance between the impedance of the filament heating circuit and the impedance of the resonance circuit system.   The switching means of the filament heating circuit is configured to be turned off until the peak phase of the direct current flowing through the filament heating transformer due to resonance between the impedance of the filament heating circuit viewed from the input end and the impedance of the resonance circuit system. The discharge lamp lighting device according to claim 1.   The filament heating circuit is controlled so that the switching means is turned on before the output voltage of the inverter means is applied between its input terminals, and is turned off before the output voltage becomes zero. Item 3. The discharge lamp lighting device according to Item 1 or 2.   The filament heating circuit changes the on-duty by simultaneously changing the phase before and after the rising point of the output voltage of the inverter means, so that the filament heating amount is required according to the dimming degree of the discharge lamp. The discharge lamp lighting device according to claim 1, wherein the discharge lamp lighting device is configured to have a value.   5. The discharge lamp lighting device according to claim 1, wherein the switching means of the filament heating circuit is a MOS-FET.

Images