JP2001217092A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a cold start of a discharge lamp, while supplying necessary advance preheating current, in a device for lighting a discharge lamp with an inverter having practically a pulse current power source. SOLUTION: With the discharge lamp lighting device provided with a rectifier circuit 2 for outputting practically a pulse voltage (A-point voltage) after full- wave rectification of an alternating current 1, an inverter 3 for converting the pulse voltage into a high-frequency output, a discharge lamp 5 supplied with the high-frequency output of the inverter 3 through a resonant circuit 4, and a control circuit 6 for controlling the inverter 3, the control circuit 6 sets the oscillation frequency of the inverter 3 relatively low at a prescribed interval near the lowest point of the above pulse voltage, and sets the same relatively high at other intervals than that near the lowest point, during preheating the discharge lamp 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for lighting a discharge lamp by an inverter using a substantially pulsating voltage as a power supply.

[0002]

2. Description of the Related Art A rectifier circuit for full-wave rectifying an AC power supply to output a pulsating voltage substantially, an inverter for converting the pulsating voltage to a high-frequency output, and a high-frequency output of the inverter connected via a resonance circuit The discharge lamp lighting device including the supplied discharge lamp and a control circuit for controlling the inverter does not require a large-capacity smoothing capacitor for smoothing the pulsating voltage to be connected to the output of the rectifier circuit. This is advantageous for cost reduction.

[0003]

However, when a normal method of obtaining an advance preheating current by operating the inverter at a constant oscillating frequency when preheating the discharge lamp is adopted, the pulsating voltage near the valley point can be obtained. The preheating current cannot be obtained due to the voltage drop. Also, if the oscillation frequency of the inverter is reduced to gain the preheating current, the voltage applied to the discharge lamp near the peak of the pulsating voltage is too high, so that the discharge lamp cold starts and the discharge lamp There is a problem that the life is shortened. Therefore, an object of the present invention is to provide a necessary preheating current to a discharge lamp and prevent a cold start of the discharge lamp in a device for lighting a discharge lamp by an inverter using a voltage that is a substantially pulsating current as a power supply. It is in.

[0004]

Means for solving the problems are as described in the claims.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described. However, this is merely an exemplary embodiment adopted based on the present invention, and the present invention will be described based on matters unique to the embodiment. Therefore, the technical scope of the present invention should be determined based on the matters stated in the claims and matters substantially equivalent to the matters.

The illustrated embodiment comprises a rectifier circuit 2 for full-wave rectifying an AC power supply 1 and outputting a substantially pulsating voltage (point A voltage), and an inverter 3 for converting the pulsating voltage to a high-frequency output. In the discharge lamp lighting device including the discharge lamp 5 to which the high frequency output of the inverter 3 is supplied via the resonance circuit 4 and the control circuit 6 for controlling the inverter 3, the control circuit 6 In some cases, the oscillation frequency of the inverter 3 is relatively reduced to f2 in a predetermined section near the valley point of the pulsating voltage, and the oscillation frequency of the inverter 3 is relatively increased in a predetermined section other than the vicinity of the valley point. f
1 is a discharge lamp lighting device provided with a control means. By doing so, the impedance of the resonance circuit 4 decreases in a predetermined section near the valley point of the pulsating voltage, so that a relatively large preheating current is applied to the discharge lamp 5. Further, in a predetermined section other than the vicinity of the valley point, the impedance of the resonance circuit 4 becomes large, so that the voltage applied to the discharge lamp 5 can be suppressed, so that a cold start of the discharge lamp 5 can be prevented. In addition, the oscillation frequency of the inverter 3 in a predetermined section near the valley point of the pulsating voltage is set to f2 which is the same as the oscillation frequency when the discharge lamp 5 is turned on by all light.
The complexity of the frequency setting element can be avoided. Also, a small-capacity capacitor C1 (for example, 2.2 μF
Are connected in parallel. If the impedance of the AC power supply 1 is substantially zero, the capacitor C1 is not particularly required. However, in the case of a commercial AC power supply, its impedance is relatively high in a high frequency range.
The small-capacity capacitor C1 is often required as a power supply source to the inverter 3.

More specifically, the AC power supply 1 is full-wave rectified by a full-wave rectifier DB1 using a diode bridge, the capacitor C1 is charged by the pulsating output voltage, and the charge of the capacitor C1 is supplied to the inverter 3. . The inverter 3 is, for example, of a half-bridge type. The output of the control circuit 6 is applied to the control terminals of the semiconductor switching elements Q1 and Q2 such as transistors via the drive circuits 7 and 8, so that the semiconductor switching elements Q1 and Q2 are alternately arranged. When turned on, a high-frequency output is obtained. Inverter 3
Is supplied to the discharge lamp 5 via a DC cut capacitor C2 and a current limiting choke coil L1.
The resonance capacitor C3 is connected in parallel to the secondary side of. The resonance circuit 4 is preferably a series resonance type including a capacitor C2, a choke coil L1, a discharge lamp 5, and a resonance capacitor C3, as in this embodiment.

The main element of the control circuit 6 is that the oscillation circuit 10 oscillates at the frequency set by the oscillation frequency setting circuit 9 based on the resistors R1 and R2, and the output of the oscillation circuit 10 is output via the pulse output circuit 11 as described above. This is a known circuit added to the driving circuits 7 and 8. On the other hand, the output of the rectifier circuit 2 is a resistor R
3, non-inverting input terminal (+) of comparator CP1 via R4
The non-inverting input terminal (+) has a resistor R5
Are connected in parallel. The output VCC of the DC power supply 12 for stabilizing the output of the rectifier circuit 2 at a low voltage is determined by the comparator CP1.
And a comparator CP1 via a resistor R6.
, And a resistor R7 is connected in parallel to the inverting input terminal (-). The output of the comparator CP1 is connected to a connection point between the resistors R1 and R2.
The output VCC of the DC power supply 12 is also supplied to the oscillation frequency setting circuit 9, the oscillation circuit 10, and the pulse output circuit 11.

Next, a control operation at the time of preheating the discharge lamp 5 will be described. In a predetermined section near the valley point of the pulsating voltage, the resistance R
4, the connection point voltage of R5 is lower than the connection point voltage of the resistors R6 and R7 (hereinafter referred to as reference voltage).
The output of 1 becomes L level, the resistor R2 is short-circuited, and only the resistor R1 becomes effective. Then, the frequency set by the oscillation frequency setting circuit 9 becomes lower and f2 (for example, 5
0 kHz), and the inverter 3 also has the oscillation frequency f2
Oscillates at In this case, since the impedance of the resonance circuit 4 becomes small, a relatively large preheating current is given to the discharge lamp 5 despite the low pulsating voltage section.
In a predetermined section other than the vicinity of the valley point, the resistances R4, R4
5 is higher than the reference voltage, the comparator C
The output of P1 becomes H level, the resistor R2 is not short-circuited, and the series total resistance of the resistors R1 and R2 becomes effective. Then, the frequency set by the oscillation frequency setting circuit 9 increases to f1 (for example, about 60 kHz), and the inverter 3 also oscillates at the oscillation frequency f1. In this case, since the impedance of the resonance circuit 4 increases, the voltage applied to the discharge lamp 5 can be suppressed in spite of the section in which the pulsating voltage is high, so that the cold start of the discharge lamp 5 can be prevented.

FIG. 2 is a timing chart showing when the discharge lamp 5 is preheated. In a section where the pulsating voltage at point A is relatively low, the output of the comparator CP1 is at L level and the inverter 3 is relatively driven. Oscillates at a low oscillation frequency f2, and a relatively large preheating current is given. In a section where the pulsating voltage at point A is relatively high, the output of comparator CP1 becomes H level,
The inverter 3 oscillates at a relatively high oscillation frequency f1,
Since the voltage applied to the discharge lamp 5 is suppressed, a cold start of the discharge lamp 5 can be prevented. Therefore, according to the present embodiment, in the apparatus for lighting the discharge lamp 5 by the inverter 3 using the voltage that is a substantially non-smooth pulsating current that does not smooth the output of the rectifier circuit 2,
To provide the necessary pre-heating current for
Cold start of the discharge lamp 5 can be prevented.
Although not particularly described because it has nothing to do with the present invention, when the preliminary preheating of the discharge lamp 5 is completed, the discharge is performed by the inverter 3 based on a circuit function (not shown) for controlling the oscillation frequency setting circuit 9, for example. After a voltage required for starting the electric lamp 5 is applied, the discharge lamp 5 is led to a lighting state, which is achieved by a known technique.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram.

FIG. 2 is a timing chart showing the same operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 AC power supply 2 Rectifier circuit 3 Inverter 4 Resonance circuit 5 Discharge lamp 6 Control circuit C1 Small capacity capacitor

Claims (3)

[Claims] 1. A rectifier circuit for outputting a substantially pulsating voltage by full-wave rectifying an AC power supply, an inverter for converting the pulsating voltage to a high-frequency output, and a high-frequency output of the inverter connected via a resonance circuit. A discharge lamp to be supplied, and a discharge lamp lighting device including a control circuit for controlling the inverter,
The control circuit, when preheating the discharge lamp, relatively lowers the oscillation frequency of the inverter in a predetermined section near the valley of the pulsating voltage, and relatively lowers the oscillation frequency of the inverter in a predetermined section other than near the valley. A discharge lamp lighting device provided with a control means for raising the height. 2. The discharge lamp lighting device according to claim 1, wherein the oscillation frequency of the inverter in a predetermined section near the valley point of the pulsating voltage is the same as the oscillation frequency for all-lighting the discharge lamp. 3. The discharge lamp lighting device according to claim 1, wherein a small-capacity capacitor is connected in parallel to an output of the rectifier circuit.