JPH0845693A - Dimming method - Google Patents

Abstract

PURPOSE:To prevent flicker and hysteresis effectively and generate wide range dimming easily by setting the repeatitive frequency of pulse signals to a point in the neighborhood of the specific value. CONSTITUTION:The duty ratio of frequency signals in the neighborhood of the repetitive frequency 120 is varied by a waveform generator 2 in accordance with the brightness level set by the user and is subjected to PWM modulation, and the obtained pulse signals are fed to a lighting circuit 3. The pulse signals are received by the reception part 5 of the lighting circuit 3 and forwarded to a changeover part 6, and a signal transmitter 8 in the lighting circuit 3 oscillates stable high frequency signal and gives it to the changeover part 6. The changeover part 6 changes over the fed high frequency signal in conformity to the pulse signal and forwards it to a lamp driver 7. This prevents the hysteresis phenomenon due to high frequency and flicker due to low frequency which are likely to occur at the time of dimming, and PWM dimming can be performed even with a pulse width which may appear both in the lighting mode and exciting mode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dimming method, and can be applied to dimming by pulse width modulation of illumination using a high frequency magnetic field excitation type electrodeless fluorescent discharge lamp as a light source.

[0002]

2. Description of the Related Art Conventionally, incandescent lamps, fluorescent lamps, electrodeless fluorescent discharge lamps, etc. have been used as light sources for illumination. An incandescent lamp has a coil inside a glass bulb, and a filament or an electrode, which is a lighting source, is worn out by long-time lighting and blinking, and evaporates or burns out.

Therefore, a so-called high frequency magnetic field excitation type electrodeless fluorescent discharge lamp in which a coil is wound around the outer circumference of a glass bulb is used. In this electrodeless fluorescent discharge lamp, argon gas and a small amount of mercury are enclosed in a vacuum glass bulb, and an excitation coil is wound around the glass bulb several times. A high frequency magnetic field is generated by applying a high frequency current to the excitation coil. As a result, the mercury enclosed inside the glass bulb is excited and turned into plasma. This plasma generates ultraviolet rays of 253.7 [nm], and the ultraviolet rays cause the phosphor coated on the inner wall of the glass to emit light. Since the electrodeless fluorescent discharge lamp is a lighting system that uses a high-frequency current, it can blink instantaneously, and dimming and brightness can be adjusted by a PWM (Pulse Width Modulation) system that temporally changes the pulse width. Further, the electrodeless fluorescent discharge lamp has a longer life than incandescent lamps and fluorescent lamps.

When the electrodeless fluorescent discharge lamp is dimmed by the PWM system, the brightness may change abruptly. Therefore, the pulse width is changed after the electrodeless fluorescent discharge lamp is turned on, and the pulse width is discontinuous. Are avoiding.

[0005]

By the way, in the pulse width, a high-frequency current is passed through the excitation coil to excite the mercury in the glass bulb of the electrodeless fluorescent discharge lamp in the excited state, and the glass of the electrodeless fluorescent discharge lamp. There is a lighting mode in which mercury in a sphere is excited and turned into plasma and is in a lighting state. There is also a pulse width consisting of two modes: excitation mode and lighting mode. This electrodeless fluorescent discharge lamp is PWM dimmed when the pulse width is in the lighting mode.

FIG. 2A shows pulse widths PW1, PW2 and PW3 of the repetition period when PWM dimming the electrodeless fluorescent discharge lamp at an arbitrary repetition frequency. 2B, 2C, and 2D are waveforms of the peak-to-peak value (hereinafter, referred to as PP value) of the voltage at both ends of the excitation coil in the pulse widths PW1, PW2, and PW3 of the repetition period, respectively. Indicates. The pulse widths PW1, PW2, and PW3 have two modes, that is, an excitation mode in a portion where the voltage PP value is high and a lighting mode in a portion where the voltage PP value is low.

However, in such a pulse width consisting of two modes, when the pulse width of the driver input is gradually expanded from the excitation mode to the lighting mode, the duration of the excitation mode is extended as shown in FIG. 3 (A). Then, after that, the extended excitation mode rapidly shifts to the lighting mode, so that the duration of the excitation mode is shortened as shown in FIG. Further, when the pulse width of the driver input is gradually shortened from the lighting mode to the excitation mode, mode displacement occurs with a short input pulse width, as shown in FIGS.

For example, when the repetition frequency is a high frequency of 400 [Hz] and the mercury plasma amount at the time of transition from the excitation mode to the lighting mode is equal to the mercury plasma amount at the time of transition from the lighting mode to the excitation mode, Since the amount of residual plasma is small in the transition from the excitation mode, the excitation time is long, and the amount of residual plasma is large in the transition from the lighting mode, the lighting mode is long.

Due to such a hysteresis phenomenon, the dimming of the high frequency magnetic field excitation type electrodeless fluorescent discharge lamp, that is, the dimming when the repetition frequency is high, can be easily dimmed only in the lighting mode. Since there is hysteresis in a wide range of pulse widths over both the excitation mode and the lighting mode, there is a problem that dimming is difficult.

When the repetition frequency is low,
Even in the lighting mode, when it is in the vicinity of the transition point, it takes time to start the next cycle, so that the mercury plasma is almost extinguished. Therefore, hysteresis hardly occurs, but there is a problem in that flickering is felt due to human visual characteristics.

The present invention has been made in view of the above points, and proposes a dimming method capable of effectively preventing flickers and hysteresis when dimming the light source of the illumination by the PWM method. is there.

[0012]

In order to solve such a problem, according to the present invention, a pulse signal is generated in a dimming method for dimming a light source used for illumination by a pulse signal according to a set luminance level. Set the repetition frequency used for the operation to around 120 [Hz].

[0013]

By setting the repetition frequency used when generating the pulse signal to around 120 Hz, flickers and hysteresis can be effectively prevented.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, reference numeral 1 generally indicates the structure of an illuminating device using a high frequency magnetic field excitation type electrodeless fluorescent discharge lamp as a light source. This illuminating device 1 is for dimming the brightness by PWM, and includes a waveform generator 2, a lighting circuit 3, and an electrodeless fluorescent discharge lamp 4.

The waveform generator 2 has a repetition frequency of 120 [Hz].
The duty of the frequency signal in the vicinity is changed according to the brightness level set by the user and PWM-modulated, and the pulse signal obtained as a result is output to the lighting circuit 3. The lighting circuit 3 includes a receiving unit 5, a switching unit 6, a lamp driver 7 and an oscillator 8. The pulse signal is received by the receiving unit 5 and given to the switching unit 6. The oscillator 8 is a crystal oscillator,
For example, a stable high frequency of 13.56 [MHz] is oscillated and given to the switching unit 6. The switching unit 6 switches the high frequency signal input from the oscillator 8 according to the pulse signal and sends it to the lamp driver 7. Therefore, the electrodeless fluorescent discharge lamp 4 is excited intermittently.

In the above construction, the waveform generator 2 sets the repetition frequency to around 120 [Hz], performs pulse width modulation, and outputs pulse signals having different duties. The high frequency 13.56 [MHz] from the oscillator 8 is switched by the switching unit 6 according to the pulse signal and output, so that the lamp driver 7
Drive. Therefore, it is possible to prevent a hysteresis phenomenon due to a high frequency and a flickering due to a low frequency during dimming, and not only when the pulse width is in the lighting mode but also when the pulse width is in both the excitation mode and the lighting mode. Can be dimmed.

According to the above configuration, the repetition frequency is 1
By setting it near 20 [Hz], it is possible to prevent the hysteresis phenomenon due to high frequency and the flickering due to low frequency.
Therefore, PWM dimming can be easily performed not only when the pulse width is in the lighting mode but also when the pulse width is in both the excitation mode and the lighting mode.

In the above embodiments, the illumination using the electrodeless fluorescent discharge lamp of high frequency magnetic field excitation type as the light source has been described, but the present invention is not limited to this, and the illumination using the fluorescent light or the incandescent lamp as the light source is also possible. good.

[0020]

As described above, according to the present invention, when dimming the light source used for illumination, the repetition frequency is 120 [Hz].
By setting them in the vicinity, it is possible to prevent flickering and hysteresis phenomena and easily realize dimming in a wide range.

[Brief description of drawings]

FIG. 1 is a block diagram showing the overall configuration of a light control device.

FIG. 2 is a schematic diagram showing a PP value of a repetition frequency and a voltage.

FIG. 3 is a schematic diagram for explaining mode displacement in a hysteresis phenomenon.

[Explanation of symbols]

1 ... Lighting device, 2 ... Waveform generator, 3 ... Lighting circuit,
4 ... Electrodeless fluorescent discharge lamp, 5 ... Receiving part, 6 ... Switching part, 7 ... Lamp driver, 8 ... Oscillator.

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[Procedure amendment]

[Submission date] October 19, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Delete

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

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[0005]

In the light emitting state, a high-frequency current is passed through the excitation coil to excite the mercury in the glass bulb of the electrodeless fluorescent discharge lamp in the excited state, and in the glass of the electrodeless fluorescent discharge lamp. There is a lighting mode in which mercury in a sphere is excited and turned into plasma and is in a lighting state. This electrodeless fluorescent discharge lamp is PWM for both excitation and lighting modes.
Dimmed.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

For example, the repetition frequency is 400 [Hz]
In some cases, the transition from the excitation mode to the lighting mode requires a long excitation time due to the small amount of residual plasma, and the transition from the lighting mode to the excitation mode requires a large amount of the residual plasma, resulting in a long lighting mode.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

Due to such a hysteresis phenomenon, dimming of the high frequency magnetic field excitation type electrodeless fluorescent discharge lamp, that is, dimming when the repetition frequency is high, can be easily dimmed only within the lighting mode. Since there is hysteresis in a wide range of pulse widths over both the excitation mode and the lighting mode, there is a problem that dimming is difficult.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

Further, when the repetition frequency is low, even in the lighting mode, it takes time until the next cycle starts in the vicinity of the transition point, so that the mercury plasma is almost extinguished. Therefore, hysteresis hardly occurs, but there is a problem in that flickering is felt due to human visual characteristics.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

The present invention has been made in consideration of the above points, and proposes a dimming method capable of effectively preventing flickering and hysteresis when dimming the light source of the illumination in both modes by the PWM method. Is what you are trying to do.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Delete

Claims (2)

[Claims] 1. A dimming method for dimming a light source used for illumination by a pulse signal according to a set brightness level, wherein a repetition frequency used when the pulse signal is generated is set.
A dimming method characterized by setting around 120 [Hz]. 2. The dimming method according to claim 1, wherein the light source is an electrodeless fluorescent discharge lamp of high frequency magnetic field excitation type.