JPH0529088A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To prevent generation of a lamp current idle time in a discharge lamp lighting device using a resonance type inverter. CONSTITUTION:An inductance element 50 is in series connected to a discharge lamp 15 and a phasial difference is made between output voltage of a high-frequency inverter 12 and lamp voltage in order to compensate required for restrike of the discharge lamp 15. Generation of a lamp current idle time is prevented so as to thereby avoid fluctuation of an arc and generation of a noise.

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 starting a discharge lamp and controlling lighting.

[0002]

2. Description of the Related Art Conventionally, as a lighting system for suppressing the distortion of the lamp current and for adjusting the discharge lamp while maintaining a constant lighting frequency, see page 16 of the 1987 National Convention of the Lighting Society of Japan. A resonance type self-excited half-bridge inverter, which is a PWM dimming method, is known.

Generally, when a discharge lamp, especially a high-intensity discharge lamp such as a metal halide lamp is lit by using an AC power source, the lamp is re-ignited when the input power is changed, that is, when the direction of the lamp current flow is changed. A compensating voltage needs to be applied across the lamp.

[0004]

However, when the lamp is lit by using a sine wave output AC power source having a slow alternating speed of power such as a resonance type high frequency inverter, the rise of the output voltage follows the change of the lamp voltage. It is not possible to supply sufficient voltage across the lamp to compensate for lamp re-ignition.

For this reason, there is a problem that a quiescent period occurs in the lamp current when the input power is alternated, which causes flickering of the lamp and noise.

[0006]

In order to solve the above-mentioned problems, a discharge lamp lighting device of the present invention includes a DC power source, a high frequency inverter driven by the DC power source and oscillating, and an output terminal of the high frequency inverter. A resonance circuit composed of a series circuit of a connected choke coil and a capacitor, a series circuit composed of a discharge lamp and an inductance element connected to the connection point of the choke coil and a capacitor, and the discharge lamp via the pulse transformer. A starting pulse generator connected to apply a high voltage pulse, a detector for detecting a characteristic relating to a lamp characteristic, and an output signal of the detector to change the oscillation frequency or duty ratio of the high frequency inverter to change the discharge. A lighting control device for controlling lighting of the lamp is provided.

[0007]

With the above configuration, by shifting the output voltage phase of the high frequency inverter and the voltage phase of the discharge lamp,
At the time of switching the lamp current, a voltage for compensating the re-ignition of the discharge lamp is supplied from the high-frequency inverter to avoid the occurrence of a rest period in the lamp current and to prevent the lamp from flickering and generating noise.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a configuration diagram showing a first embodiment in which the discharge lamp lighting device of the present invention is applied to a series inverter. In FIG. 1, 11 is a DC power supply, 12 is a high frequency inverter, 13 is a capacitor, 14 is a choke coil, 15
Is a discharge lamp, 16 is a starting pulse generator, 17 and 18
Is a capacitor, 19 is a detection device, 20 is a lighting control device, and the DC power supply 11 has a high-frequency inverter 12, a capacitor 13, a choke coil 14, and a secondary winding constituting the starting pulse generation device 16 that functions as an inductance element. The discharge lamp 15 is connected via the secondary winding of the pulse transformer 21 so as to start and light the discharge lamp 15.

The high frequency inverter 12 is an FET which is a pair of switching elements that perform 0N-0FF in opposite phases.
22, 23 and drive circuits 24, 2 for driving them
5 and the oscillation circuit 26, and the DC power supply 1
1 as input, capacitor 13, choke coil 14,
A series circuit including the discharge lamp 15 and the pulse transformer 21 and capacitors 17 and 18 connected in parallel to the discharge lamp 15 and the pulse transformer 21 operate as loads.

The oscillating circuit 26 is controlled by the lighting control device 20, so that the oscillating frequency of the high-frequency inverter 12 is such that the capacitors 13 and 1 constituting the LC series resonance circuit.
When the resonance frequency is controlled to be a resonance frequency determined by the capacitances of the capacitors 7 and 18 and the inductance of the choke coil 14 and the secondary winding of the pulse transformer 21, the capacitance of the capacitor 13 arranged in parallel with the discharge lamp 15 is controlled. A sine wave voltage (resonance voltage) is generated at both ends, and the lamp voltage also becomes a sine wave.

The inductance component of the choke coil 14 becomes an inductance that limits the lamp current when the discharge lamp 15 is turned on. Further, the capacitor 13 is charged with electric charge while the FET 22 is on and the FET 23 is off, and conversely, the FET 22 is off and the FET 2 is
3 has a function of maintaining the lighting of the discharge lamp 15 by discharging the electric charge during the ON period.

The capacitors 17 and 18 are the capacitors 1
3. A series resonance circuit is formed between the choke coil 14 and the choke coil 14 and also has a function of circulating the high voltage pulse generated by the start pulse generator 16 and protecting the high frequency inverter 12.

Here, the starting pulse generator 16 includes a pulse transformer 21, a FET 27 which is a switching element,
A flyback that is generated at both ends of the primary winding of the pulse transformer 21 when the FET 27 connected in series with the primary winding of the pulse transformer 21 is turned on at high speed after being turned on. The voltage is boosted via the pulse transformer 21 and applied to the discharge lamp 15 as a high voltage pulse.

The discharge lamp lighting device of this embodiment is characterized in that the secondary winding of the pulse transformer 21 constituting the starting pulse generator 16 has a sufficiently large inductance.

The operation of the discharge lamp lighting device having the above configuration will be described. When power is supplied to the lighting device, a start signal is first sent from the lighting control device 20 to the DC power supply 11, the DC power supply 11 operates, and the output voltage thereof is supplied to the high frequency inverter 12. At the same time, the oscillation circuit 26 that constitutes the high-frequency inverter 12 starts to oscillate, and the FETs 22, 2
The drive circuits 24 and 25 for driving 3 respectively operate, and the FETs 22 and 23 repeat 0N-0FF in mutually opposite phases.

In the series inverter of this embodiment, the FE
The output power is supplied from the DC power supply 11 to the load in the subsequent stage only when T22 is turned on, and the supplied power is maximum when the ON duty of the FET 22 is maximum (50%). It should be noted that the FETs 22 and 23 are controlled so that one of them is turned on except for a minimum mutual pause period for avoiding simultaneous ON.

When the high frequency inverter 12 is driven, until the discharge lamp 15 is lit, the load of the high frequency inverter 12 is the capacitor 13, the choke coil 14,
There is an LC series resonance circuit that forms a closed loop composed of the capacitors 17 and 18, and a resonance voltage is generated across the capacitors 17 and 18. This resonance voltage corresponds to the output open voltage of the high frequency inverter 12 supplied to the discharge lamp 15, and the higher the ON duty of the FET 22, the higher the resonance voltage.

From the lighting control device 20, an activation signal is further sent to the oscillation control circuit 28 which constitutes the activation pulse generator 16, and the oscillation control circuit 28 issues a gate signal to generate the F signal.
Turn ET27 on and off.

The FET 27 forms a closed loop with the DC power supply 11 via the primary winding of the pulse transformer 21. Therefore, the FET 27 is turned on and the OF is suddenly changed.
Then, at the moment when the FET 27 is turned off at high speed due to the inductance of the primary winding of the pulse transformer 21, a flyback voltage is generated across the primary winding of the pulse transformer 21. This voltage is further boosted by the pulse transformer 21, and a high voltage pulse is supplied to the discharge lamp 15 so as to establish conduction between the main electrodes of the discharge lamp 15.

When the main electrodes of the discharge lamp 15 are electrically connected, that is, when the discharge lamp 15 is activated, a lamp current flows to the detection resistor 29, and a potential difference is generated across the detection resistor 29 whose one side is grounded. The detection device 19 detects this, and the lighting control device 20 to which the detection signal is sent determines that the discharge lamp 15 is turned on, and sends a signal to the oscillation control circuit 28 constituting the starting pulse generation device 16 to start up. Stop pulse generation. The impedance of the detection resistor 29 is extremely small and does not affect the lighting state of the discharge lamp 15. When the discharge lamp 15 is activated, the lamp voltage drops sharply. After that, as the gas pressure in the arc tube of the lamp rises, the lamp voltage gradually increases to reach the rated lighting. In the present embodiment, the detection device 19 has a voltage corresponding to the lamp voltage, that is, the secondary winding of the pulse transformer 21, the discharge lamp 15, and the detection resistor 29. The voltage generated at both ends of 18 is divided by a capacitor, that is, the voltage at the connection point between the capacitors 17 and 18 is detected, and a detection signal is sent to the lighting control device 20.

The lighting control device 20 sends a control signal to the oscillating circuit 26 which constitutes the high frequency inverter 12 in response to the detection signal, and the ON duty of the FETs 22 and 23,
Alternatively, the oscillation frequency is changed to control the lighting of the discharge lamp 15.

In this embodiment, for example, the O of the FET 22 is
By controlling the N duty to supply a constant starting frequency, that is, a resonance frequency, to the discharge lamp 15 with a starting current larger than that at the time of rated lighting, and controlling lighting, the lighting frequency at this time is Lamp 15
Frequency inverter 1 including the inductance component of the secondary winding of the pulse transformer 21 connected in series to the
It matches the resonance frequency determined by the parallel load circuit connected to 2. Therefore, during this period, the lamp current waveform changes while maintaining a substantially sine wave.

However, when the lamp is lit by using a sine wave output AC power supply having a slow alternating speed of power, such as a resonance type high frequency inverter, the increase in the output voltage of the high frequency inverter cannot follow the change of the lamp voltage. It may not be possible to provide sufficient voltage across the lamp to compensate for lamp re-ignition. Therefore, as shown in FIG. 2, there is a problem in that a quiescent period occurs in the lamp current when the input electric power alternates, which causes flickering of the lamp and noise.

Therefore, in this embodiment, the inductance of the secondary winding of the pulse transformer 21 constituting the starting pulse generator 16 is sufficiently large. That is,
In FIG. 1, a pulse transformer is provided between the voltage generated across the capacitors 17 and 18 connected to the output terminal of the high frequency inverter 12 and the voltage across the discharge lamp 15 including the detection resistor 29, that is, the lamp voltage. A phase difference occurs due to the inductance of the secondary winding 21. Utilizing this phase difference, at the time of switching of the lamp current, a voltage for compensating the re-ignition of the discharge lamp is supplied from the high-frequency inverter, and it is possible to avoid the occurrence of a pause period in the lamp current. It is the point.

In this embodiment, since the discharge lamp 15 is lit at a high frequency of about 10 [kHz] during rated lighting, the power factor is close to 1 and the phases of the lamp voltage and the lamp current are almost in phase. Is. Therefore, providing the phase difference between the output voltage of the high frequency inverter 12 and the lamp voltage is equivalent to providing the phase difference between the lamp current and the lamp current. At this time, the phase difference between the voltage at the output terminal of the high frequency inverter 12, that is, the voltage generated across the capacitors 17 and 18, and the lamp voltage is about 2 in FIG.
It is necessary to have 0 degrees, and in order to satisfy this, the inductance of the secondary winding of the pulse transformer 21 must be sufficiently large.

As in the present embodiment, the pulse lamp 21 having an inductance of the secondary winding of about 1 [mH] is used to provide a phase difference between the output voltage of the high frequency inverter 12 and the lamp current, and the discharge lamp. Fig. 3 shows the lamp current waveform when 15 is turned on and the occurrence of the lamp current rest period is avoided.
Shown in. From FIG. 3, a phase difference occurs between the voltage generated across the capacitors 17 and 18 which is the output voltage of the high frequency inverter 12 and the lamp current, and a voltage of about 60 [V] is discharged when the lamp current is switched. It can be seen that the voltage supplied to the lamp 15 is compensated for the voltage required for re-ignition.

In this embodiment, the series inverter is applied as the high frequency inverter, but any other one having a similar function such as a half bridge inverter may be used.

The control method of the lamp current may be a combination of the oscillation frequency control of the high frequency inverter 12 and the PWM control of the switch element.

Further, in the present embodiment, the lamp current flowing through the detection resistor 29 is detected as means for detecting the activation / lighting of the discharge lamp 15, but in addition to this, the lamp voltage, lamp power, light output, etc. Other lamps may be used as long as they are related to the lamp characteristics capable of confirming the start and lighting of the lamp. Further, in this embodiment, the switching element is F
Although ET is used, a bipolar transistor or the like may be used.

Next, a second embodiment of the present invention will be described. A configuration diagram of the discharge lamp lighting device in the present embodiment is shown in FIG. The basic operation of the discharge lamp lighting device according to the present embodiment is the same as that according to the first embodiment. The difference from the former of the present embodiment is that of the pulse transformer 21, which should generate a phase difference between the lamp voltage and the voltage at the output terminal of the high frequency inverter 12, that is, the voltage generated across the capacitors 17 and 18. Instead of reducing the inductance of the secondary winding, the pulse transformer 21
That is, another inductance element 30 is connected in series to the secondary winding of FIG. Since the other components are the same, the same reference numerals are given and description thereof is omitted.

As a result, the pulse transformer 21 can be downsized, and the starting pulse generator 16 can be downsized. Generally, in order to prevent the high voltage pulse from being attenuated and the noise from being generated, when the starting pulse generator 16 is placed separately from the main body of the discharge lamp lighting device, that is, the high frequency inverter 12 part and is placed in the immediate vicinity of the discharge lamp 15, Being able to downsize the activation pulse generator 16 is very beneficial.

Next, a third embodiment of the present invention will be described. FIG. 5 shows a configuration diagram of the discharge lamp lighting device according to the present embodiment. The basic operation of the discharge lamp lighting device according to the present embodiment is the same as that according to the first embodiment. The difference from the former of the present embodiment is that the inductance element 30, that is, the capacitors 17 and 1 connected in the second embodiment.
A switch element 31 is connected in parallel to another inductance element 30 which is connected in series to the secondary winding of the pulse transformer 21 in order to generate a phase difference between the voltage generated across 8 and the lamp voltage. Is. Since the other components are the same, the same reference numerals are given and description thereof is omitted.

In the present embodiment, first, the switch element 3 is supplied during a period in which the starting voltage is supplied from the starting pulse generator 16 to the discharge lamp 15, that is, a high voltage pulse application period.
1 is cut off and the inductance element 30 is short-circuited, and the inductance and impedance of the inductance element 30 disappear. As a result, the starting voltage can be supplied to the discharge lamp 15 without attenuating the high voltage pulse generated by the starting pulse generator 16.

Even during the starting current supply period after the main electrodes of the discharge lamp 15 are electrically connected, the switching element 31 is cut off and the inductance element 30 is kept short-circuited, so that the inductance and the impedance of the inductance element 30 disappear. . As a result, a quick rise of the light output is realized, and a decrease in efficiency during the starting current supply period is prevented.

When the discharge lamp 15 reaches the vicinity of the rated lighting state, the switch element 31 is opened to allow the lamp current to flow through the inductance element 30, and the inductance of the inductance element 30 causes the lamp current idle period to occur. To prevent.

The series of controls is performed by the lighting control device 20 which receives a signal from the detection device 19 which detects the lighting state of the discharge lamp.

[0037]

With the above structure, by providing a phase difference between the output voltage of the high frequency inverter and the lamp voltage, it is possible to prevent the lamp current waveform during the rated lighting from having a pause period. This makes it possible to provide a discharge lamp lighting device that suppresses flicker and arc bending.

[Brief description of drawings]

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

FIG. 2 is a control diagram of lamp voltage and current in a conventional device.

FIG. 3 is a control diagram of lamp voltage / current in the discharge lamp lighting device shown in FIG.

FIG. 4 is a configuration diagram of a discharge lamp lighting device according to another embodiment of the present invention.

FIG. 5 is a configuration diagram of a discharge lamp lighting device according to another embodiment of the present invention.

[Explanation of symbols]

11 power supply 12 high frequency inverter 13 capacitors 14 choke coil 15 discharge lamp 16 Starting pulse generator 17 Capacitor 18 capacitors 19 Detector 20 Lighting control device 21 pulse transformer

Continued front page    (72) Inventor Masataka Ozawa             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Kazutaka Koyama             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd.

Claims (3)

[Claims] 1. A direct current power supply, a high frequency inverter driven by the direct current power supply to oscillate, a resonance circuit comprising a series circuit of a choke coil and a capacitor connected to an output end of the high frequency inverter, the choke coil and a capacitor. A series circuit consisting of a discharge lamp and an inductance element connected to the connection point of the starting lamp, a start pulse generator connected to apply a high voltage pulse to the discharge lamp via the inductance element, and characteristics relating to lamp characteristics. And a lighting control device for controlling lighting of the discharge lamp by changing an oscillation frequency or a duty ratio of the high frequency inverter according to an output signal of the detection device. 2. The discharge lamp lighting device according to claim 1, wherein the inductance element connected in series to the discharge lamp is composed of a series circuit of at least two inductance elements. 3. The discharge lamp lighting device according to claim 1, wherein at least one inductance element of the series circuit of the inductance elements connected in series to the discharge lamp is connected in parallel with the switch element.