JP2003197394A - Discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems in continuous light control of a discharge lamp. <P>SOLUTION: After an alternating current power source 1 is rectified by a rectifier 2, a smoothed high direct current voltage VDC is generated in both ends of a capacitor C2 via a boosting chopper circuit 3. An output of an inverter circuit 4 including a pair of semiconductor switching elements Q1 and Q2 converting the direct current voltage CDC into a high frequency alternating current is fed to the discharge lamps 5 and 5 individually via resonance circuits such as capacitors C6 and C3, choke coils L1 and L2, and capacitors C4 and C5. In a full lighting mode of this discharge lamp lighting device, the discharge lamp 5 is lighted at a frequency ffull on a leading phase area side of a resonance curve (fig 2) in the resonance circuit system including the discharge lamp 5 in a shutoff time. For lighting the discharge lamp 5 in a continuous light control mode, a light control level can be continuously varied within a frequency range on the lagging phase area side of the resonance curve 6 of the resonance circuit system in a shutoff time. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting apparatus in which a dimming level is continuously variable in a predetermined dimming level range. 2. Description of the Related Art An output of an inverter circuit for converting a DC voltage to a high frequency is supplied to a discharge lamp via a resonance circuit, and the discharge lamp is turned on in an all-light mode and a resonance circuit including the discharge lamp when turned off. 2. Description of the Related Art Discharge lamp lighting devices for lighting at a frequency in the fast region of a resonance curve of a system are well known. And when dimming the discharge lamp, the dimming is often performed only at a specific dimming level called step dimming, but recently, the dimming level of the discharge lamp has been continuously changed. Discharge lamp lighting devices with a variable continuous dimming mode have also appeared. In this type of device, the discharge lamp is switched from an all-light lighting mode, that is, a 100% lighting mode, to a dimming level of about 20 to 30%.
In many cases, the dimming level is continuously variable. That is, the light output of the discharge lamp is 1
The dimming can be continuously performed from 00%, and the lower limit of the dimming level can be narrowed down to about 20 to 30%. [0003] However, in the all-lights-on mode, since the resonance curve of the resonance circuit system at the time of extinguishing is in the fast-advance region, if the frequency is increased and the dimming level is reduced. Inevitably, the light passes through the resonance point (resonance center frequency) of the resonance curve of the resonance circuit system when the light is turned off. When the user performs continuous dimming, it is sufficiently conceivable to keep the discharge lamp lit at the resonance point. Then, in this state, when the discharge lamp approaches the end of life and the emitter radiation disappears and goes out, the equivalent impedance of the discharge lamp becomes substantially infinite, so the resonance point voltage of the resonance curve of the resonance circuit system is extremely high. As a result, an excessive voltage is applied to the discharge lamp, and an excessive electric stress is applied to components of the resonance circuit, semiconductor switching elements of the inverter circuit, and the like. for that reason,
It is necessary to add a protection circuit and use a component having a large maximum rating, and it is unavoidable to increase the number of components and increase the cost. In view of such problems to be solved, an object of the present invention is to eliminate such a problem when a discharge lamp is continuously dimmed. According to the present invention, an output of an inverter circuit for converting a DC voltage into a high-frequency AC is supplied to a discharge lamp via a resonance circuit. A discharge lamp lighting device that lights up at a frequency on the fast region side of a resonance curve of a resonance circuit system including the discharge lamp when the light is turned off, and when the discharge lamp is turned on in a continuous dimming mode, A discharge lamp lighting device characterized in that a dimming level can be continuously varied within a frequency range on a side of a delay region of a resonance curve of the resonance circuit system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described, which are merely exemplary embodiments adopted based on the present invention, and the present invention is not limited to the specific embodiments. The technical interpretation of the present invention should be determined based on the matters stated in the claims and the matters substantially equivalent to the matters described in the claims. In the illustrated embodiment, an AC power supply 1 is connected to a rectifier 2
After the rectification, a high DC voltage VDC smoothed across the capacitor C2 is generated via the step-up chopper circuit 3. The output of the inverter circuit 4 including the pair of semiconductor switching elements Q1 and Q2 for converting the DC voltage VDC into high-frequency AC is output from the capacitors C6 and C3, the choke coils L1 and L2,
Discharge lamps 5 and 5 through resonance circuits such as capacitors C4 and C5
Respectively. In this discharge lamp lighting device, in the all-light lighting mode, the discharge lamp 5 is lit at the frequency ffull on the fast-phase side of the resonance curve 6 (FIG. 2) of the resonance circuit system including the discharge lamp 5 when the lamp is turned off. I have. Next, when the discharge lamp 5 is lit in the continuous dimming mode, the dimming level can be continuously varied within the frequency range on the side of the lag region of the resonance curve 6 of the resonance circuit system when the discharge lamp 5 is turned off. It is characterized by doing. [0007] The discharge lamp lighting device is controlled by a remote control transmitter 7, and an infrared signal from the remote control transmitter 7 is received by a remote control light receiving unit 9 in a lighting mode control circuit 8. When the lighting control circuit 10 requires only a fixed frequency other than the dimming mode of the discharge lamp 5, for example, a preheating / starting mode or an all-light lighting mode, the frequency setting of the inverter control circuit 11 is performed. A signal distinguished according to the mode is sent to the circuit 12. The frequency setting circuit 12 determines the signal and sets the frequency, and the oscillation circuit 13 oscillates at the frequency and sends an oscillation signal to the inverter circuit 4 via the pulse output circuit 14. This oscillation signal is supplied to the drive circuit 1
The switching elements Q1 and Q2 are respectively applied to the switching elements Q1 and Q2 via the switching elements 5 and 16, and the switching elements Q1 and Q2 are alternately turned on to output a high frequency. When the discharge lamp 5 is set in the dimming mode by controlling with the remote control transmitter 7, the lighting control circuit 10 outputs a PWM dimming signal which is a continuous dimming signal. This signal is d
uty signal, which is generated by the DC voltage conversion circuit 17
Converted to C voltage. In response to the DC voltage, the frequency modulation control circuit 18 of the inverter control circuit 11 can continuously change the frequency setting of the frequency setting circuit 12. In the continuous dimming mode, a continuous dimming signal (PWM dimming signal) from the lighting control circuit 10 is output so that continuous dimming can be performed after the dimming level is set to about 75% once. It is good to be done. When the light output is further reduced from a specific frequency at the time of stepwise dimming lighting, the frequency is increased. As the frequency is increased, the power of the discharge lamp is reduced and deeper dimming is possible, but if the discharge lamp 5 can be stably lit, the lower limit of the dimming level can be reduced to about 20 to 30%. Good. The specific frequency may be set to be the same as the frequency at the time of starting the discharge lamp 5. Also,
Immediately after the discharge lamp 5 is started, the discharge lamp 5 may be once lit at the specific frequency, and thereafter, may be shifted to the continuous dimming mode or the all-light lit mode. According to this embodiment, there is no danger that the resonance point voltage of the resonance curve of the resonance circuit system becomes extremely high and an excessive voltage is applied to the discharge lamp 5, and the components of the resonance circuit and the inverter circuit 4 Excessive electrical stress is not applied to the semiconductor switching element and the like. For this reason, it is not necessary to add a protection circuit or use a component having a large maximum rating, so that the number of components can be reduced, and the cost can be easily reduced.

[Brief description of the drawings] FIG. 1 is a circuit diagram showing an embodiment of the present invention. FIG. 2 is a resonance curve characteristic diagram of the resonance circuit system. [Explanation of symbols] VDC DC voltage 4 Inverter circuit 5 Discharge lamp 6 Resonance curve of the resonance circuit system when the light is off

Claims (1)

Claims: 1. An output of an inverter circuit for converting a DC voltage into a high-frequency AC is supplied to a discharge lamp via a resonance circuit,
In the all-light lighting mode, a discharge lamp lighting device that lights the discharge lamp at a frequency in a fast region of a resonance curve of a resonance circuit system including the discharge lamp when the lamp is turned off, wherein the discharge lamp is in a continuous dimming mode. Wherein the dimming level can be continuously varied within a frequency range on the side of the delay region of the resonance curve of the resonance circuit system when the lamp is turned off.