JP2002231483A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device capable of reducing a filament current at lighting time while securing a sufficient preceding preheating current. SOLUTION: This discharge lamp lighting device has a boosting chopper part 11 for converting an AC power source into DC voltage, and a discharge lamp 13 for supplying a high frequency AC power source via a resonance circuit composed of an inductor L2 and a capacitor C4. A second resonance circuit composed of a capacitor C9 and a preheating transformer T2 is arranged on the output end of an inverter part 12, and a pair of coils on the secondary side of the preheating transformer T2 are respectively connected to a pair of filaments of the discharge lamp 13. The discharge lamp lighting device is provided with a chopper control part 16 for controlling the boosting chopper part 11 so that output voltage of the boosting chopper part 11 of a lighting period reduces more than output voltage of a preceding preheating period, and an inverter control part 14 for controlling the inverter part 12 so that an oscillating frequency of the inverter part 12 of the preceding preheating period reduces more than a resonance frequency of the second resonance circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[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 by converting a low-frequency AC power supply from a commercial power supply into a high-frequency AC power supply.

[0002]

2. Description of the Related Art A circuit according to a first conventional example of this type of discharge lamp lighting device is shown in FIG. The low-frequency AC power from the commercial power supply is rectified by a diode bridge composed of diodes D1 to D4 of the step-up chopper 51, and the choke coil L
1, the voltage is boosted by a boosting chopper circuit including a transistor Q1 and a diode D5. Electrolytic capacitor C2
, A DC voltage of, for example, 300 V is obtained. This DC voltage is converted into a high-frequency AC power supply by the following inverter unit 52 and becomes a power supply to the discharge lamp 53.

The inverter section 52 has a half-bridge inverter circuit composed of a pair of transistors Q2 and Q3, and the control section 54 performs on / off driving for turning on the transistors Q2 and Q3 alternately, thereby obtaining a high frequency. Outputs current. The high-frequency current passes through the DC cut capacitor C3, passes through the inductor L2, and discharges the lamp 53.
Flows through the other filament through the capacitor C4.

The frequency of the on / off drive by which the control unit 54 turns on the transistors Q2 and Q3 alternately depends on the discharge lamp 5
3 is controlled to a different value according to each control state of preheating, starting, rated lighting, and dimming lighting. With reference to the resonance frequency of the resonance circuit formed by the inductor L2 and the capacitor C4 through which the high-frequency current output from the inverter unit 52 flows,
By changing the driving frequency of the transistors Q2 and Q3, appropriate operation in each control state of preheating, starting, rated lighting, and dimming lighting is realized.

FIG. 6 shows the characteristics of the resonance circuit of the inductor L2 and the capacitor C4 in each of the control states of preheating, starting, rated lighting, and dimming lighting, and the transistors Q2 and Q3.
6 is a graph showing a relationship with the setting of the driving frequency. FIG.
, Curves a, b, and c show the resonance characteristics of the resonance circuit formed by the inductor L2 and the capacitor C4 in the extinguished state, the dimmed lighting state, and the rated lighting state of the discharge lamp 53, respectively.

During the preheating period, that is, immediately after the lighting operation of the discharge lamp 53, the discharge lamp 53 is turned off.
The resonance characteristics are as shown by curve A. The driving frequency f (pre) at this time is determined by the inductor L2 and the capacitor C2.
4 is set to a value sufficiently higher than the resonance frequency (no-load resonance frequency) f0. By doing so, the discharge lamp 53
Of the pair of filaments can be performed while maintaining the voltage V1a between both ends lower than the discharge starting voltage. That is, the supplied current (resonant current) at this time all flows through the one and the other filaments of the discharge lamp 53 via the capacitor C4.

After the preheating period, the controller 54 lowers the drive frequency f to approach the no-load resonance frequency f0. Then, the voltage V1a across the discharge lamp 53 along the characteristics of the curve A
Rises and eventually reaches the discharge starting voltage, the discharge lamp 53
Starts discharging. As a result, the resonance characteristic changes to become as shown by curve C. Thereafter, by lowering the driving frequency f to f (FULL) along the resonance characteristic of the curve C, a stable lamp current and lamp voltage at the time of rated lighting are obtained, and the lighting state of the discharge lamp 53 is maintained.

At the time of lighting control, the driving frequency f is increased so as to be away from the resonance frequency f1 at lighting, and f (DIM)
Set to. As a result, the lamp current is reduced, and the resonance characteristics as shown by the curve B are obtained.

At the time of dimming lighting, the voltage V1 across the discharge lamp 53
a rises and the impedance of the capacitor C4 decreases due to the increase in the driving frequency.
The current flowing through the filament No. 3 tends to increase as compared with the rated lighting.

If the preheating current flowing through the filament is too large when the discharge lamp 53 is turned on, a phenomenon that the inner wall of the lamp tube near the filament becomes black at an early stage may adversely affect the lamp life. Are known. Therefore, as described below, the discharge lamp 53
A circuit has been proposed to reduce the preheating current flowing through the filament when the LED is in the lighting state.

FIG. 7 is a circuit diagram of a discharge lamp lighting device according to a second conventional example. In this circuit example, the capacitor C4 in FIG. 5 is divided into capacitors C5 and C6 and connected to the discharge lamp 53. By setting C4 = C5 + C6 with respect to the capacitance of each capacitor, the resonance characteristic of the circuit of FIG. 7 becomes as shown in FIG. 6, similarly to the circuit of FIG. However, comparing C4 and C5 in which the preheating current flowing in the filament of the discharge lamp 53 flows, C4> C5, so that the impedance with respect to the high-frequency current becomes larger in C5, and the filament current can be reduced.

FIG. 8 is a circuit diagram of a discharge lamp lighting device according to a third conventional example. In this circuit example, the inverter unit 52
And a second resonance circuit (resonance circuit for filament current) comprising a capacitor C9 and a transformer T2. The characteristic of this resonance circuit can be such that the filament current during lighting is small and the filament current during the preheating period is large, as shown by the curve d in FIG. The control power generation unit 55
Is configured by a step-down chopper circuit or the like, generates a low DC voltage (for example, 12 V), and supplies the low DC voltage to the control unit.

[0013]

However, in the discharge lamp lighting device according to the second prior art, the voltage at both ends of the discharge lamp 53 during the preheating period is kept low and a sufficient preheating current is secured. The combinations of capacitors C5 and C6 that satisfy the conditions are limited. Among them, the effect is limited in order to keep the filament current during lighting small. Moreover, the degree of freedom in design is reduced.

In the discharge lamp lighting device according to the third conventional example, in order to make the filament current at the time of lighting smaller than that in the preceding preheating period, the frequency f (pre) in the preceding preheating period is used.
And the frequency f (FULL) at the time of lighting must be largely separated. That is, as shown by the curve d in FIG. 9, it is necessary to set the gradient of the filament current at the frequency f (pre) during the preheating period as small as possible. Otherwise, a slight shift in the oscillation frequency causes a large change in the preheating current. If the filament current during lighting is reduced while the filament current during the preheating period is sufficiently supplied, the frequency f (pre) during the preheating period and the frequency f (FULL) during lighting are largely separated from each other. Become.

Further, it is necessary to take care to eliminate the influence on the frequency used for the infrared remote controller (remote control device). For example, the lighting frequency f (FULL), which is the lower frequency, is set to about 50 kHz. Then, the frequency f (pre) during the preheating period is set to about 150 kHz. In this case, the inverter unit 52 is approximately 50 k
It is necessary to perform stable operation in a relatively wide frequency range from Hz to 150 kHz. Inverter section 5
The two pairs of transistors Q2 and Q3 are switched with a dead-off time (a period during which they are simultaneously turned off) so as not to be turned on at the same time. As the switching frequency increases, the ratio of the dead-off time increases, and the variation in output increases. Alternatively, strict control of the oscillation frequency is required.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a discharge lamp lighting device capable of suppressing a filament current at the time of lighting while securing a sufficient preheating current. Aim.

[0017]

To achieve the above object, a discharge lamp lighting device according to the present invention comprises a DC converter for receiving an AC voltage from an AC power supply, converting the AC voltage into a DC voltage, and outputting the DC voltage. A discharge lamp lighting device, comprising: an inverter unit for receiving the high-frequency AC voltage; and a discharge lamp to which a high-frequency AC power output from the inverter unit is supplied via a resonance circuit including an inductor and a capacitor. A second resonance circuit including a capacitor and a preheating transformer is provided at the output end of the unit, and a pair of windings on the secondary side of the preheating transformer are connected to a pair of filaments of the discharge lamp, respectively, to light the lamp. A DC voltage controller that controls the DC converter so that the output voltage of the DC converter is lower than the output voltage during the pre-heating period; and Wherein the oscillation frequency of the serial inverter portion is provided and an inverter control unit for controlling the inverter unit so as to be lower than the resonance frequency of the second resonant circuit.

As shown in FIG. 10, the filament current during the pre-heating period is as shown by curve d, and the filament current at the time of lighting is as shown by curve e. Therefore, the frequency f (pre) for obtaining the same preheating current can be set low. In other words, it is possible to reduce the difference between the oscillation frequency at the time of lighting and at the time of advance reservation, which is necessary to suppress the filament current at the time of dimming lighting while securing a sufficient preceding preheating current.

Preferably, the oscillation frequency of the inverter unit at the time of rated lighting is 50 kHz or more, and the oscillation frequency of the inverter unit during the preheating period is 100 kHz or less.

Further, the discharge lamp lighting device is capable of dimming, and the lower limit of the luminous flux at the time of the dimming lighting is 30% of the luminous flux at the time of the rated lighting.
% Is also preferable.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of a discharge lamp lighting device according to a first embodiment of the present invention. A low-frequency AC power supply from a commercial power supply is rectified by a diode bridge composed of diodes D1 to D4 of a step-up chopper section (corresponding to a DC conversion section) 11, and is composed of a choke coil L1, a transistor Q1, and a diode D5. The voltage is boosted by the boost chopper circuit. At both ends of the electrolytic capacitor C2,
For example, a DC voltage of 300 V is obtained. This DC voltage is converted into a high-frequency current by the following inverter unit 12 and becomes a lighting current of the discharge lamp 13.

The inverter section 12 has a half-bridge inverter circuit composed of a pair of transistors Q2 and Q3, and the inverter control section 14 performs on / off driving for turning on the transistors Q2 and Q3 alternately. Outputs high frequency current. The high frequency current is supplied to the filament of the discharge lamp 13 through the DC cut capacitor C3 and the inductor L2.

The control power generation section 15 is composed of a step-down chopper circuit or the like, generates a low DC voltage (for example, 12 V), and supplies it to the inverter control section 14. The chopper control unit (corresponding to a DC voltage control unit) 16 is a control IC
(For example, Motorola MC33262)
A gate control signal for the transistor Q1 of the boost chopper unit 11 is generated. The inverter control unit 14 converts a signal oscillated using a general-purpose control IC (for example, μPC494 manufactured by NEC) into a driver circuit (for example, IR211 manufactured by IR).
1) to the gates of the transistors Q2 and Q3 of the inverter section 12.

When the power is turned on, the chopper controller 16
And the inverter control unit 14 starts oscillating, the output voltage Vdc of the step-up chopper unit 11 becomes 300 V, and the oscillation frequency fINV of the inverter unit 12 is f (pre) = 95 k
Hz. At this time, since the voltage between the filaments of the discharge lamp 13 is lower than the discharge starting voltage, the discharge lamp 13 does not start discharging.

The high-frequency current output from the inverter section 12 also flows to the transformer T2 through the capacitor C9. The current induced on the secondary side of the transformer T2 flows to the filament of the discharge lamp 13 through the capacitor C7 or C8. This current becomes the preheating current, for example, 70
It is about 0 mA.

After pre-heating for about 2 to 3 seconds, the oscillation frequency fINV of the inverter section 12 is increased to f (str) = 75 kHz.
Lower to z. As a result, the voltage between the filaments of the discharge lamp 13 rises to the discharge starting voltage, and the discharge starts. Thereafter, the oscillation frequency fINV of the inverter unit 12 is changed to f (F
ULL) = 55 kHz, the discharge lamp 1
3 is in a rated lighting state.

In the case of performing dimming lighting in which the discharge lamp 13 is lit at a luminance lower than the rated lighting luminance, a dimming signal is given to the chopper controller 16 and the inverter controller 14 as shown in FIG. As a result, the oscillation frequency fINV of the inverter section 12 becomes f (DIM) = 80 kHz, and the output voltage Vdc of the step-up chopper section 11 becomes 250V.
Thus, the discharge lamp 13 enters the dimming lighting state.

As described above, by making the output voltage Vdc of the step-up chopper section 11 during dimming lighting lower than the preceding preheating period, it becomes possible to reduce the difference between the oscillation frequencies at the time of lighting and during the preceding reservation. . That is, it is possible to minimize the difference between the oscillation frequency at the time of lighting and at the time of advance reservation necessary for suppressing the filament current at the time of dimming lighting while securing a sufficient preceding preheating current.

FIG. 2 is a circuit diagram of a discharge lamp lighting device according to a second embodiment of the present invention. The same components as those in the circuit of FIG. The configuration of the step-up chopper section 11, the inverter section 12, and the like is the same as that of FIG. 1, and is different from the circuit of FIG. 1 in that a transformer T3 is interposed in series with one of the filaments of the discharge lamp 13.
The secondary side of the transformer T3 is input to the lighting detection unit 17, and the output of the lighting detection unit 17 is input to the chopper control unit 16.

As in the first embodiment, during the preheating period, the output voltage Vdc of the step-up chopper 11 is 300 V, and the oscillation frequency fINV of the inverter 12 is f (pre) = 95 k.
It operates under the condition of Hz, and thereafter, the discharge is started by lowering the oscillation frequency fINV of the inverter section 12 to f (str) = 75 kHz.

In the circuit shown in FIG. 2, when the discharge lamp 13 is not lit, the electromotive force generated by the two complementary windings on the temporary side cancel each other, so that no voltage is generated on the secondary side. When the discharge starts and the discharge lamp 13 is turned on, the temporary side 2
Since the balance of the electromotive force generated by the three windings is lost, a voltage corresponding to the difference is generated on the secondary side. When this voltage is detected by the lighting detection unit 17 and its detection output is given to the chopper control unit 16, the chopper control unit 16 sets the duty ratio of the transistor Q1 so that the output voltage Vdc of the boost chopper unit 11 becomes 250V. Control.

That is, the output voltage V of the step-up chopper 11
dc is controlled to 300 V during the pre-heating period and before the start of discharge, and 250 V after the start of discharge and at the time of rated lighting and dimming lighting.
V. As described above, the output voltage Vdc of the step-up chopper 11 during the dimming operation is controlled to be lower than the preceding preheating period. As a result, it is necessary to suppress the filament current during the dimming operation while securing a sufficient advance preheating current. The difference between the oscillating frequencies at the time of proper lighting and at the time of advance reservation can be made as small as possible.

FIG. 3 is a circuit diagram of a discharge lamp lighting device according to a third embodiment of the present invention. The same components as those in the circuit of FIG. Figure 1
The discharge lamp lighting device of the first embodiment shown in FIG. 3 is a lighting device that performs dimming control stepwise, whereas the discharge lamp lighting device of the third embodiment shown in FIG. Is a lighting device that performs the following. That is, in FIG. 3, the control unit 18 responds to a signal from the dimming signal unit 19 to turn on the inverter unit 1 at the time of lighting.
2 within a predetermined range (for example, 50 kHz
(z to 85 kHz). This allows
The lamp current flowing through the discharge lamp 13 changes continuously, and continuous dimming is performed.

In FIG. 3, a transformer T1 is a step-up transformer, and when the discharge lamp 13 is of a type having a high discharge starting voltage (for example, a high efficiency type lamp), the transistor Q1
2 and Q3 are used to reduce the stress (source-drain voltage). Further, a capacitor C5 is added to the resonance circuit of the inductor L2 and the capacitor C4 in consideration of operation modes such as rated lighting and dimming lighting.

In this embodiment, as in the second embodiment, before the start of discharge, such as in the preceding preheating period, the lighting detector 17 is turned on.
Control unit 18 based on the signal from
The duty ratio of the transistor Q1 is controlled so that the output voltage Vdc of 1 becomes 250V. FIG. 4 shows the boosting chopper sections 11 in the lighting state and before the start of discharge.
Output voltage Vdc and the oscillation frequency fI of the inverter section 12
The relationship with NV is shown by a graph.

Thereafter, when the discharge lamp 13 is in the lighting state, the control unit 18 changes the oscillation frequency fINV of the inverter unit 12 at the same time as the output of the step-up chopper unit 11 according to the signal from the dimming signal unit 19. The voltage Vdc is also changed (see FIG. 4).

At rated lighting, when the oscillation frequency fINV of the inverter section 12 is f (FULL) = 55 kHz, the output voltage Vdc of the boost chopper section 11 is 300 V, but the deepest dimming state (for example, 25% of rated lighting) % Luminance) and the oscillation frequency fINV of the inverter 12 is f (D
When IM2) = 85 kHz, the step-up chopper unit 11
Output voltage Vdc is reduced to 250V.

As the dimming becomes deeper and the oscillation frequency fINV of the inverter 12 becomes higher, the filament current increases, as can be seen from the curve d in FIG. Therefore, when a discharge lamp lighting device capable of dimming to a low luminance (low luminous flux) region is realized as in this embodiment, the output voltage Vdc of the boosting chopper unit 11 during dimming lighting is set to the output during the preceding preheating period. By controlling the voltage to be lower than the voltage Vdc, it is possible to reduce the difference between the oscillation frequency at the time of lighting and at the time of advance reservation, which is necessary to suppress the filament current at the time of dimming lighting while securing a sufficient preceding preheating current. . For example, as described in the above embodiment, the oscillation frequency of the inverter unit 12 at the time of rated lighting is 50 kHz or more, and the oscillation frequency of the inverter unit 12 during the preheating period can be set to 100 kHz or less. Further, in the filament current characteristic shown by the curve d in FIG. 9, the lower limit luminous flux (luminance) at the time of dimming lighting
Can be set to be 30% or less of the luminous flux at the time of rated lighting.

As described above, with respect to the discharge lamp lighting device of the present invention,
Several embodiments have been described. However, the present invention is not limited to the above embodiment, but can be implemented in various other forms.

[0040]

As described above, according to the discharge lamp lighting device of the present invention, the output voltage Vdc of the DC converter (step-up chopper) at the time of lighting is changed to the output voltage Vdc during the pre-heating period.
By lowering the control, it is possible to reduce the difference between the oscillation frequency at the time of lighting and at the time of advance reservation necessary to suppress the filament current at the time of dimming lighting while securing a sufficient preheating current. As a result, the influence of the dead-off time of the inverter unit on the output (luminance of the discharge lamp) can be suppressed.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a discharge lamp lighting device according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a discharge lamp lighting device according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram of a discharge lamp lighting device according to a third embodiment of the present invention.

FIG. 4 is a graph showing a relationship between an output voltage of each step-up chopper unit and an oscillation frequency of an inverter unit before a lighting state and before discharge starts.

FIG. 5 is a circuit diagram of a discharge lamp lighting device according to a first conventional example.

FIG. 6 is a graph showing the relationship between the characteristic of the resonance circuit of the inductor and the capacitor and the drive frequency of the inverter in the control states of preheating, starting, rated lighting, and dimming lighting.

FIG. 7 is a circuit diagram of a discharge lamp lighting device according to a second conventional example.

FIG. 8 is a circuit diagram of a discharge lamp lighting device according to a third conventional example.

FIG. 9 is a graph obtained by adding a filament current characteristic by a second resonance circuit to the graph of FIG. 6;

FIG. 10 is a graph showing a relationship between a filament current and a frequency.

[Explanation of symbols]

 Reference Signs List 11 Step-up chopper (DC converter) 12 Inverter 13 Discharge lamp 14 Inverter controller 16 Chopper controller (DC voltage controller)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Koji Saeki 1048 Kazuma Kadoma, Kadoma City, Osaka Prefecture F-term in Matsushita Electric Works, Ltd. (reference) 3K072 AA02 BA05 BB01 BC01 BC03 DC08 DD03 DD04 GA02 GB12 GC04 HA06 3K098 CC41 DD37 EE06 EE13 EE14 EE32 GG02

Claims (3)

[Claims] 1. A DC converter for converting an AC voltage from an AC power supply into a DC voltage and outputting the DC voltage, an inverter for converting the DC voltage into a high-frequency AC voltage, and a high-frequency AC power supply output from the inverter. Is a discharge lamp lighting device having a discharge lamp supplied through a resonance circuit including an inductor and a capacitor, wherein a second resonance circuit including a capacitor and a preheating transformer is provided at an output terminal of the inverter unit, and the preheating is performed. A pair of windings on the secondary side of the transformer are connected to a pair of filaments of the discharge lamp, respectively, and the output voltage of the DC converter during the lighting period is lower than the output voltage during the preheating period. A DC voltage control unit that controls a DC conversion unit, and an oscillation frequency of the inverter unit during the preceding preheating period is lower than a resonance frequency of the second resonance circuit. The discharge lamp lighting apparatus characterized by comprising an inverter control unit for controlling the inverter unit so. 2. The discharge lamp lighting device according to claim 1, wherein the oscillation frequency of the inverter unit at the time of rated lighting is 50 kHz or more, and the oscillation frequency of the inverter unit during the preheating period is 100 kHz or less. . 3. The discharge lamp lighting device according to claim 1 or 2, wherein the discharge lamp lighting device is capable of dimming, and the lower limit light flux at the time of dimming lighting is 30% or less of the light flux at the time of rated lighting. apparatus.