JP3400468B2 - Discharge lamp 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 a discharge lamp lighting device having a function of switching between full lighting and dimming lighting.

[0002]

2. Description of the Related Art FIG. 7 shows a conventional discharge lamp lighting device of this type. As shown in the figure, it comprises an inverter circuit 2 for starting and lighting the discharge lamp 1 at a high frequency, and a control unit 3 for on / off controlling the switching elements Q ₁ and Q ₂ of the inverter circuit 2. The inverter circuit 2 converts the DC voltage of the DC power supply E into a high frequency voltage and applies it to the discharge lamp 1 to start and light it.

In the control unit 3, the discharge lamp 1 which is a load
The lamp voltage of the discharge lamp 1 to detect the abnormality of
The detection circuit 4 and the detection voltage detected by the detection circuit 4
Anti-R ₁~ R₃And the reference voltage determined by
The output of the inverter circuit 2 is reduced or the output of the inverter circuit 2 is reduced.
Control circuit 5 to stop shaking and discharge lamp 1 are all lit or dimmed
Control circuit 6 etc. that switches the level of the reference voltage by lighting
It is composed of.

The control circuit 5 includes an oscillation circuit 7 for controlling the oscillation of the inverter circuit 2 at a predetermined frequency, a comparator 9 for comparing the detection voltage of the detection circuit 4 with a reference voltage, and when the detection voltage is high. The output of the comparator 9 includes, for example, a latch circuit 8 that outputs an oscillation stop signal to the oscillation circuit 7. The latch circuit 8 is reset when the power is turned on.

Further, in the case of full lighting and dimming lighting, the control circuit 6 is constituted by the inverter gate G ₁ , the transistor Q _3, etc. so as to switch the reference voltage between the high level and the low level. Here, the load abnormality detection means that when the discharge lamp 1 reaches the end of its life, the thermionic emission material (emitter) applied to the filament is scattered, and the electron emission from the filament on one side disappears. Indicates the case of half-wave discharge. In this case, saturation of the current limiting choke may occur, and the current of the switching elements Q ₁ and Q ₂ of the circuit increases, causing a temperature rise or switching elements Q ₁ and Q 2.
_It can lead to the destruction of ₂ . Therefore, the detection circuit 4 that detects an increase in the lamp voltage at the end of the life is provided to protect the circuit when an abnormality occurs.

[0006]

The reference voltage, which is the threshold value for detecting the lamp voltage at the end of the life, changes the normal lamp voltage of the discharge lamp 1 with respect to the lamp current. The reference voltage and the reference voltage during dimming lighting are switched. As shown in FIG. 8, the reference voltage at the time of dimming lighting is set high, and is set higher than the detection voltage so that the normal time and the end of life are not erroneously detected.

As shown in FIGS. 7 and 8, since the dimming signal is at the L level at the time of full lighting, the output of the inverter gate G ₁ becomes the H level, the transistor Q ₃ is turned on, and the resistor R ₃ is turned on. ₂ and R ₃ are connected in parallel to lower the reference voltage. Further, when the dimming is turned on, the dimming signal becomes the H level, the output of the inverter gate G ₁ becomes the L level, the transistor Q ₃ is turned off, and the reference voltage is the divided voltage of the resistors R ₁ and R _2. As a result, the reference voltage is increased.

Here, the output side of the detection circuit 4 is connected to the foreign node.
Capacitor C so that it is not affected by noise₀Connect
ing. Dimming the inverter circuit 2 from full lighting
When switching from lighting and dimming lighting to full lighting,
False detection may occur when switching from light lighting to full lighting.
there were. That is, the dimming signal changes from H level to L level.
When it changes, the reference voltage instantly changes to L level,
The detection voltage is the above-mentioned noise prevention capacitor C. ₀By
And the characteristics of the discharge lamp 1 did not change rapidly.
Therefore, as shown by the broken line in Fig. 8 (b), switch slowly.
It becomes a strange waveform.

Therefore, there is a problem that the detection voltage exceeds the reference voltage at the moment of switching and is erroneously detected, the output of the inverter circuit 2 is reduced or the oscillation is stopped, and the discharge lamp 1 is extinguished. The present invention has been provided in view of the above points, and an object thereof is to enable switching to full lighting without erroneous detection by the detection circuit even when switching from dimming lighting to full lighting. The discharge lamp lighting device is provided.

[0010]

SUMMARY OF THE INVENTION According to the present invention, an inverter circuit for converting a DC voltage into a high frequency voltage and applying it to a discharge lamp for starting and lighting, and a switching element in the inverter circuit are turned on and off to change the frequency. A first control circuit that switches between full lighting and dimming lighting, a detection circuit that detects the tube voltage of the discharge lamp, and a detection voltage of the detection circuit and a predetermined reference voltage are compared. A second control circuit for reducing the output of the device or stopping the oscillation,
In a discharge lamp lighting device including a third control circuit that changes the level of the reference voltage by full lighting and dimming lighting, when the reference voltage shifts from a high level to a low level, the reference voltage changes A control means for further delaying is provided.

In the second aspect, when the level of the reference voltage is switched, a period in which the detection voltage is not detected is provided for a certain period.

[0012]

Since the reference voltage is delayed from the change in the detected voltage, the detected voltage does not exceed the reference voltage. Therefore, the malfunction of the inverter circuit does not occur when the dimming lighting is switched to the full lighting. The discharge lamp does not go out due to output drop or oscillation stop.

Further, according to the second aspect, when the level of the reference voltage is switched, the detection voltage is set to a non-detection period for a certain period, so that the detection voltage is changed when the dimming lighting is switched to the full lighting. Since it is not detected, the discharge lamp does not go out due to a reduction in output of the inverter circuit or a stop of oscillation without malfunction.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 shows a circuit of a main part of the embodiment 1. still,
The overall circuit configuration is the same as in FIG. As shown,
A transistor Q ₄ is connected between the reference voltage side and the comparator 9, and the transistor Q ₄ and the resistor R _{1 form} an emitter follower circuit. The capacitor C ₁ is connected in parallel with the resistor R ₁ . The transistor Q ₄ , the resistor R ₁ , the capacitor C _1, etc. constitute the control means.

Next, the operation will be described with reference to FIGS. The transistor Q ₃ is turned on when all the lights are on, and turned off when the dimming lights are on. Since the transistor Q ₃ is turned on at the time of full lighting, the reference voltage Vkf at the time of full lighting can be expressed as follows. Vkf = (Vcc × R ₃ #R ₄ ) / (R ₂ + R ₃ #R ₄ ) −V _BE where V _BE is the base-emitter voltage of the transistor Q ₄ and the collector-emitter voltage is substantially zero. .
The symbol # means parallel connection.

The reference voltage Vkd at the time of dimming lighting when the transistor Q ₃ is off is expressed by the following equation. _{Vkd = (Vcc × R 3)} / (R 2 + R 3) -V BE At this time, the transistors Q _4, since the capacitor C ₁ is charged rapidly rising voltage is faster (t ₁ in FIG. 2).

When switching from dimming lighting to full lighting, t = -RC due to the time constant of the capacitor C ₁ and the resistor R _1.
After a time of ln (Vkd / Vkf), the reference voltage drops from Vkd to Vkf. By setting this time t to be longer than the change time of the detection voltage, the detection voltage does not exceed the reference voltage when switching from the dimming lighting to the full lighting, and therefore erroneous detection does not occur.

(Embodiment 2) Embodiment 2 is shown in FIG. 3 and FIG. In this embodiment, the dimming signal is supplied to the resistor R ₁ and the capacitor C.
Delayed through ₁ , buffer G ₂ and NOR gate G ₃
The signal b is obtained by delaying the time t from the fall of the dimming signal via. Here, when the dimming signal changes from the L level to the H level, the output a of the buffer G ₂ becomes the H level after a predetermined time delay due to the resistor R ₁ and the capacitor C ₁ . The output b of the NOR gate G ₃ becomes H level at the same time as the H level of the dimming signal, as shown in FIG.

When the dimming signal changes from the H level to the L level, the signal a is at the H level for the delay time due to the capacitor C _1. Therefore, the output b of the NOR gate G ₃ is at the H level, but a predetermined time has elapsed. After that, the output a becomes L level, the output b becomes H level, and the reference voltage becomes low after the delay time t. Since the transistor Q ₃ is turned on at the time of full lighting, the reference voltage Vkf at the time of full lighting can be expressed as follows.

Vkf = (Vcc × R ₃ #R ₄ ) / (R ₂ + R ₃ #R ₄ ) Further, the reference voltage Vkd at the time of dimming lighting when the transistor Q ₃ is off is expressed by the following equation. Vkd = (Vcc × R ₃ ) / (R ₂ + R ₃ ) The delay time t is expressed by the following equation, where V _TH is the threshold voltage of the buffer G ₂ and V is the dimming signal voltage.

T = −R ₁ · C ₁ ln (V−V _TH ) / V By setting the delay time t longer than the fall time of the detection voltage, the detection voltage is changed when switching from dimming lighting to full lighting. It does not exceed the reference voltage and erroneous detection can be avoided. (Embodiment 3) Embodiment 3 is shown in FIGS. In this embodiment, when the level of the reference voltage is switched, the detection voltage is not detected for a certain period of time to eliminate erroneous detection.
That is, the transistor Q ₅ is connected to the output side of the detection circuit 4, and the transistor Q ₅ is turned on when the dimming signal rises and falls so that the detection voltage is not detected.

The circuit controlling this transistor Q ₅ is
Inverter gates G ₁ and G ₃ , AND gate G ₂ ,
It is composed of G ₄ , an OR gate G ₅ , a resistor R ₁ , a capacitor C _1, etc., and outputs an H level signal (pulse) from the OR gate G ₅ when the dimming signal rises and falls, It turns on the transistor Q ₅ .

At the time of rising of the dimming signal, the output b of the inverter gate G ₁ is at H level for a certain period of time due to the resistor R ₁ and the capacitor C _1. Therefore, as shown in FIG. Output, transistor Q ₅
Is turned on and the detection voltage is not detected. At this time, the output f of the AND gate G ₄ remains at L level due to the inverter gate G ₃ .

Next, when the dimming signal falls,
NAND gate G_FourResistor R provided on the side₁And capacitor C₁To
The output e is kept at H level for a certain period of time, and
G ₃AND gate G at the H level of the inverted output of_Fourof
Output f goes high and transistor Q_FiveTurn on
The detection voltage is not detected. Also, at this time, AND gate G
₂Since one input of L is at L level, AND gate G
₂Does not output an H level signal.

In this way, the signal g which is at the H level is generated for a certain period t of the rising and falling edges of the dimming signal, and during that period, the output of the detection circuit 4 is forcibly reduced and the detection prohibited period is set. Is provided. Therefore, when the dimming lighting is switched to the full lighting, the detected voltage does not become higher than the reference voltage, and erroneous detection is prevented. Here, the period t is represented by the following equation.

T = -R ₁ C ₁ ln (V-V _TH ) / V where V represents the voltage of the signal a and V _TH represents the threshold voltage. Further, in each embodiment, the discharge lamp lighting device can be controlled by a remote controller or the like to switch between full lighting and dimming lighting in both directions, so that highly convenient lighting can be realized. In addition, the inverter circuit can be commonly used, such as a half-bridge inverter, a single stone inverter, and a push-pull inverter.

[0027]

As described above, according to the present invention, an inverter circuit for converting a DC voltage into a high frequency voltage and applying it to a discharge lamp to start and light it, and a switching element in the inverter circuit are turned on and off to change the frequency. A first control circuit that switches between full lighting and dimming lighting, a detection circuit that detects the tube voltage of the discharge lamp, and a detection voltage of the detection circuit and a predetermined reference voltage are compared. In the discharge lamp lighting device including the second control circuit for reducing the output of the device or stopping the oscillation, and the third control circuit for changing the level of the reference voltage by full lighting and dimming lighting, the reference voltage is high. Since the control means is provided to delay the reference voltage from the change in the detection voltage when the level shifts from the level to the low level, the reference voltage is delayed from the change in the detection voltage. The quasi-voltage is not exceeded, so that there is no malfunction when switching from dimming lighting to full lighting, and there is an effect that the discharge lamp does not go out due to output reduction or oscillation stop of the inverter circuit. .

Further, according to the second aspect, when the level of the reference voltage is switched, the detection voltage is set to a non-detection period for a certain period, so that the detection voltage is changed when the dimming lighting is switched to the full lighting. Since it is not detected, the discharge lamp does not go out due to a reduction in output of the inverter circuit or a stop of oscillation without malfunction.

[Brief description of drawings]

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

FIG. 2 is an operation waveform diagram of FIG. 1 above.

FIG. 3 is a circuit diagram of a second embodiment of the above.

FIG. 4 is an operation waveform diagram of FIG. 3 above.

FIG. 5 is a circuit diagram of Embodiment 3 of the above.

FIG. 6 is an operation waveform diagram of FIG. 5 above.

FIG. 7 is a circuit diagram of a conventional example.

8 is an operation waveform diagram of FIG. 7 above.

[Explanation of symbols]

1 discharge lamp 2 Inverter circuit 4 Detection circuit

Claims (2)

(57) [Claims] 1. An inverter circuit for converting a DC voltage into a high frequency voltage and applying it to a discharge lamp for starting and lighting, and an ON / OFF control of a switching element in the inverter circuit to change the frequency to switch between full lighting and dimming lighting. The first control circuit, the detection circuit that detects the tube voltage of the discharge lamp, and the detection voltage of the detection circuit are compared with a predetermined reference voltage, and when the voltage exceeds the reference voltage, the output of the inverter circuit is reduced or oscillation is stopped. In a discharge lamp lighting device comprising a second control circuit for controlling and a third control circuit for changing the level of the reference voltage by full lighting and dimming lighting, when the reference voltage shifts from a high level to a low level. A discharge lamp lighting device, comprising: a control unit that delays the reference voltage from a change in the detected voltage. 2. The discharge lamp lighting device according to claim 1, wherein a period during which the detection voltage is not detected is provided for a certain period when the level of the reference voltage is switched.