JP3284624B2 - Electrodeless lighting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrodeless lighting device for supplying high frequency power to an electrodeless discharge lamp to emit light.

[0002]

2. Description of the Related Art Conventionally, electrodeless discharge lamps have been studied as light sources having characteristics such as high brightness and long life. FIG. 3 shows a block diagram of a lighting device of the electrodeless discharge lamp. In the figure, 1 is an oscillation circuit, 4 is a matching circuit, 6 is an amplifier circuit, 7 is an electrodeless discharge lamp, 8 is an induction coil for excitation, 9 is a switch, and 10 is a power supply. The oscillation circuit 1 oscillates at a low power. The oscillation output from the oscillation circuit 1 is amplified by the amplification circuit 6 to the required power. The output of the amplifier circuit 6 is applied to the driving coil 8 via the matching circuit 4. The matching circuit 4 performs impedance matching between the amplifier circuit 6 and the coil 8. The coil 8 is wound so as to be close to the electrodeless discharge lamp 7 and supplies high-frequency power to the gas in the electrodeless discharge lamp 7. The power supply 10 includes the oscillation circuit 1 and the amplification circuit 6
, And the drive power is supplied via the switch 9. That is, the switch 9 is a switch for turning on / off the power.

FIG. 4 is a specific circuit diagram of a conventional electrodeless lighting device. In the figure, 1 is an oscillation circuit using a crystal resonator X, constitutes a tuning circuit of a low Q by the coil L ₆ and the capacitor C _15, has an oscillator unregulated. The preamplifier 2 for amplifying the oscillation output of the oscillation circuit 1 includes a transistor Q ₄
And performing class C amplification by, and configured to tune the oscillation frequency by the coil L ₅ and the capacitor C _17.
Circuit comprising resistors R ₈ to R ₁₀ constitute a reduction哀器.
The filter circuit 3 includes a choke coil L ₃ , a capacitor C
_{4 and the} like to prevent the high frequency from returning to the power supply 10. Main amplifier 5 to be further high-frequency power amplifying an output of the preamplifier 2, a power MOSFET (hereinafter, referred to as transistors) has an amplifier according to Q _5. The matching circuit 4 is composed of a capacitor C ₁₈ -C ₂₀ or the like, is performed inductance matching between the output and the rear stage of the electrodeless discharge lamp 7 and the driving coil 8 in the main amplifier 5. The electrodeless discharge lamp 7 has a rare gas, mercury vapor or the like sealed therein, and a driving coil 8 which is an air-core coil of several turns is arranged close to the outer periphery of the electrodeless discharge lamp 7. The driving coil 8 supplies high-frequency power input from the matching circuit 4 to the luminescent gas in the electrodeless discharge lamp 7.

[0004] The overcurrent detection circuit 12 is for protecting the lighting circuit when the electrodeless discharge lamp 7 is not mounted or has an abnormality. When the electrodeless discharge lamp 7 is not mounted or when there is an abnormality, the matching (matching) by the impedance matching circuit 4 is shifted as compared with the case where the electrodeless discharge lamp 7 is turned on. Flows from Due to this excessive input current, the voltage drop of the resistor R15 increases, and the comparator I ₁₅
Since the voltage of the positive input terminal of C ₁ is higher than the voltage of the input terminal on the negative side, the potential of the output terminal of the comparator IC ₁ 'becomes the High level. Thus, the transistor Q ₃ of the flasher circuit 11 is turned on to stop the oscillation. In this way, when the abnormality of the electrodeless discharge lamp 7 continues, the lighting circuit is protected by the overcurrent detection circuit 12 and the blinking circuit 11.

[0005]

In the above conventional example, there is a problem that the inductance matching of the matching circuit 4 is not stable. That is, even if the constant of the matching circuit 4 is set, there are some components that are difficult to start due to variations in components and variations in the electrodeless discharge lamp 7, and in some cases,
Some did not start. Further, even when the constant of the matching circuit 4 is set without the electrodeless discharge lamp 7, the same problem may occur.

In the design of the overcurrent detection circuit 12, the input current also changes depending on the setting of the impedance matching circuit 4, and the overcurrent detection circuit 12 does not operate or does not operate in the absence of the electrodeless discharge lamp 7. In the state where the normal electrodeless discharge lamp 7 is mounted, the overcurrent detection circuit 1
In some cases, a problem such as non-lighting may occur due to the operation of No. 2.

The present invention has been made in view of the above points, and an object of the present invention is to provide an electrodeless lighting device that supplies high frequency power to an electrodeless discharge lamp to emit light. It is another object of the present invention to provide a matching circuit that can optimally set the impedance matching with the driving coil of the above and to optimally set an overcurrent detection circuit that detects an abnormal state of the discharge lamp.

[0008]

According to the present invention, in order to solve the above-mentioned problems, as shown in FIG. 1, an induction coil 8 is provided near an electrodeless discharge lamp 7 in which a discharge gas is sealed. The high-frequency output of the high-frequency oscillation circuit 1 is applied to the induction coil 8, and the discharge gas in the electrodeless discharge lamp 7 is discharged by the high-frequency electric field induced by the induction coil 8. Is turned on, an impedance matching circuit 4 is interposed between the induction coil 8 and the high-frequency oscillation circuit 1, and an overcurrent detection circuit 12 for detecting an abnormal state of the electrodeless discharge lamp 7 is provided. In the electrodeless lighting device in which the discharge lamp 7 is controlled to blink by the signal of the circuit 12, the time from the application of the high-frequency output to the ignition of the discharge lamp 7 is shortened. Input current when no load To the extent that the ignition starting current) becomes the maximum will be described later, the impedance matching circuit 4
Is constituted.

[0009]

FIG. 5 is an operation waveform diagram for explaining the operation of the present invention. In the figure, (a) is the input current flowing from the power supply 10, and (b) is the output voltage across the induction coil 8. At time t _1, switch 9 when the power supply 10 is turned on is turned on, a high voltage across the induction coil 8 is applied. At this time, as the input current, FIG.
As shown in FIG. Then, at time t _2, the the electrodeless discharge lamp 7 is lighted, the voltage across the induction coil 8, the input current is reduced together. A period T from time t ₁ to time t _{2 is a} time from when a voltage is applied to the induction coil 8 until the discharge lamp 7 is turned on, and is referred to as “ignition start time” here. FIG. 6 shows a change in the output voltage V ₀ (V) when the discharge lamp 7 is not loaded with respect to the ignition start time T (msec) and a change in the capacitance of the capacitor Cv in the matching circuit 4 shown in FIG. Show. As is clear from this figure, when the ignition start time T is minimum, the voltage V ₀ across the induction coil 8 when the discharge lamp 7 is not loaded is almost maximum. Therefore, when the ignition start time T is minimized, the discharge lamp 7 is most easily ignited. Therefore, regardless of the variation of components, the variation of the discharge lamp 7, etc., in each electrodeless lighting device, the firing start time T
Is minimized, the discharge lamp 7 does not start.

The large current I ₀ flowing between times t _{1 and} t _{2 in} FIG. 5A is approximated to the current when the discharge lamp 7 is in a no-load state, and is referred to herein as a “ignition starting current”. With respect to the capacitance change of the capacitor Cv in the matching circuit 4 shown in FIG.
FIG. 6 shows the change in the ignition starting current I ₀ described above. here,
If the ignition starting current I ₀ is close to the input current I _{1 for} stable lighting, there is a problem that the overcurrent detection circuit 12 malfunctions. Therefore, the larger the difference between the ignition starting current I ₀ and the input current I ₁ at the time of stable lighting is, the larger the overcurrent detection circuit 12
It is easy to detect the abnormal state of the discharge lamp 7 due to the above.

In FIG. 6, the condition of the matching circuit 4 in which the ignition starting current I ₀ is maximum is different from the condition of the matching circuit 4 in which the ignition starting time T is minimum. According to the present invention, the operation point (Cv = Cv ₁ ) where the ignition start time T is minimum and the operation point (Cv) where the ignition start current I ₀ is maximum with respect to a change in the capacitance of the capacitor Cv in the matching circuit 4. = Cv ₂ ) to set the impedance matching circuit 4. Thereby, the discharge lamp 7 is easily started, and the detection of the no-load state of the discharge lamp 7 is also facilitated.

[0012]

FIG. 1 is a circuit diagram of a preferred embodiment of the present invention. In the circuit shown in FIG. 4, it is necessary to turn on the power switch 9 and observe the input current waveform to adjust the variable capacitor Cv so as to minimize the ignition start time T. Only when the ignition start time T
, It is extremely difficult to adjust the variable capacitor Cv to an optimum value. Therefore, in the circuit of FIG. 1, in the circuit of FIG.
₁ and D ₂ are added so that a blinking control signal can be input via a diode D ₂ , and other circuit configurations are the same. The flasher circuit 11 includes a MOS transistor Q _3, consists discharge resistor R ₁₄ connected to its gate, the drain of the MOS transistor Q ₃ are connected to the base of the transistor Q ₄ of the preamplifier 2, a source ground It is connected to the. And MO
The gate of the S transistor Q _3, blinking control signal via the diode D ₂ is input.

In this embodiment, the MOS transistor Q
When the gate-source voltage of the ₃ is zero or an open state, MOS transistor Q ₃ between the drain and source becomes open, the base of the transistor Q ₄ are applied to the normal output from the oscillator circuit 1, no The electrode discharge lamp 7 lights up. Incidentally, when the base voltage of the transistor Q ₄ becomes negative voltage, a current flows between the drain and source of the MOS transistor Q _3, transistor Q ₄
The base voltage is closer to 0, the transistor Q ₄ at a negative base voltage even 0 is independent so turned off.

However, the MOS transistor Q_Three Game
Voltage sufficiently high (for example, NEC 2SK654
6V or more), the MOS transistor Q_Three No
A short circuit occurs between the rain source and the
Jista Q_Four Becomes 0, and the preamp 2
No amplification is performed, and the electrodeless discharge lamp 7 is turned off. At this time,
MOS transistor Q_Three Of the oscillation circuit 1
The impedance suddenly changes, causing oscillation stop and other phenomena.
To avoid that happening, the resistor R₉ About 10Ω
Inserting an anti. This resistance R₈ ~ R_TenComposed of
The attenuator reduces the effect of load fluctuations during the operation of the electrodeless discharge lamp 7.
I'm frustrated. Also, the transistor Q_FourIs open
When the main amplifier 5 self-oscillates,
Resistor R to avoid₁₁Is inserted, the resistance R₁₁
May be omitted. Coil L₇ Is the transistor Q_Five Entering
Inserted to counteract the force capacitance
R ₁₂Is the transistor Q_Five The input impedance of
Connected to match the output of amplifier 2
May be omitted.

FIG. 2 shows operation waveforms of the circuit shown in FIG. In the figure, (a) is a blink control signal, (b) is an input current,
(C) is an output voltage generated at both ends of the coil 8. FIG.
When the blinking control signal is applied during the period Ta in FIG.
S transistor Q ₃ is turned on, oscillation of the main amplifier 5 is stopped. Then, when the blinking control signal becomes zero in the period Tb, MOS transistor Q ₃ is turned off, the oscillation starts in the main amplifier 5, after the elapse of the ignition starting time T,
The discharge lamp 7 lights stably. Therefore, by applying a blinking control signal to intermittently MOS transistors Q _3,
The ignition start time T is observed for each cycle, and by changing the capacity of the variable capacitor Cv, the first operation point at which the ignition start time T is minimized, and the ignition start current (input current at no load) ) Is easily set between the second operating points at which the maximum value is obtained.

In this embodiment, in FIG. 1, the capacitance of the capacitor Cv is set between the point at which the ignition starting time T becomes minimum and the point at which the ignition starting current becomes maximum. The ignition start time T is not necessarily limited to only the minimum point, and may be set near the minimum point as long as it is equal to or higher than the output voltage required for starting the discharge lamp 7. Similarly, the ignition starting current is not limited to only the maximum point. If the ignition starting current is equal to or more than the ignition starting current necessary for detecting the no-load state of the discharge lamp 7, the ignition starting current is set near the maximum point. Is also good.

[0017]

According to the present invention, as described above, the impedance matching means is interposed between the induction coil and the high-frequency oscillator so that the abnormal state of the electrodeless discharge lamp continues.
In an electrodeless lighting device having means for protecting a circuit ,
From the operating point at which the time until the discharge lamp is ignited after applying the high-frequency output to the second operating point at which the current until the discharge lamp is ignited is the impedance, Since the matching means is constituted, it is easy to start and it is possible to easily detect when the discharge lamp is in a no-load state.

As described in the embodiment, if the electrodeless discharge lamp is intermittently controlled to blink by the blinking control signal, the period from when a high-frequency output is applied to the electrodeless discharge lamp to when the discharge lamp is ignited. The time and the ignition starting current can be measured for each cycle of the blinking control signal, and the work of adjusting the circuit constant can be easily performed.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a preferred embodiment of the present invention.

FIG. 2 is an operation waveform diagram of a preferred embodiment of the present invention.

FIG. 3 is a block diagram showing a schematic configuration of a conventional example.

FIG. 4 is a circuit diagram showing a specific configuration of a conventional example.

FIG. 5 is a waveform chart for explaining the operation of the present invention.

FIG. 6 is a characteristic diagram for explaining the operation of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Oscillation circuit 2 Preamplifier 3 Filter circuit 4 Matching circuit 5 Main amplifier 6 Amplification circuit 7 Electrodeless discharge lamp 8 Induction coil for excitation 9 Switch 10 Power supply 11 Flashing circuit 12 Overcurrent detection circuit

Claims (1)

(57) [Claims] An induction coil is arranged in proximity to an electrodeless discharge lamp in which a discharge gas body is sealed, a high-frequency output of a high-frequency oscillator is applied to the induction coil, and an electrodeless electrode is generated by a high-frequency electric field induced in the induction coil. Discharging the discharge gas in the discharge lamp to light the electrodeless discharge lamp, interposing impedance matching means between the induction coil and the high-frequency oscillator ,
Protects the circuit when the abnormal state of the electrodeless lamp continues.
In electrodeless lighting device having means that, a first operating point time is shortened to the discharge lamp from application of the high frequency output ignites, current until the discharge lamp ignites is maximum An electrodeless lighting device, wherein a circuit constant of the impedance matching means is set between a second operating point.