JPH11135284A - Lighting device for discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lighting device for a discharge lamp which has a control function to turn off/turn on a discharge lamp by an external control signal and another function to apply pre-heating current when it is turned off so that it can be shifted from lights-out condition to lighting condition instantly, and in which the discharge lamp can be reliably turned off when shifting from lighting condition to light-out condition. SOLUTION: This device is equipped with an inverter to apply a high frequency voltage to a discharge lamp LAMP and a control circuit 2 to control light output of the discharge lamp LAMP by controlling an oscillating frequency of the inverter. Power supply to the discharge lamp LAMP is blocked by stopping oscillation of the inverter for a specific time, and after detecting that the high frequency voltage becomes lower than a reignition voltage value, it is shifted to a pre-heating waiting condition where sufficient pre-heating current is supplied to start the discharge lamp LAMP after a specific time has elapsed.

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, and more particularly to a discharge lamp lighting device having a discharge lamp extinguishing / lighting control function by an external control signal.

[0002]

2. Description of the Related Art FIG. 6 is a circuit diagram of a conventional example according to the present invention.
FIG. 8 shows a specific circuit of the control circuit 2, and FIG.
Shown in

This circuit comprises a DC power supply circuit 1 connected to an AC power supply Vac between input terminals to output a DC voltage, and a smoothing capacitor connected to both ends of the DC power supply circuit 1 for smoothing the DC voltage output of the DC power supply circuit 1. C1, a series circuit of two switching elements S1 and S2 connected to both ends of the smoothing capacitor C1, an inductor Lo connected at one end to a connection point between the switching element S1 and the switching element S2,
Capacitor C having one end connected to the other end of inductor Lo
And a discharge lamp LAMP connected to both ends of the switching element S2 via the inductor Lo and the capacitor C, and a preheating capacitor Co connected between the non-power-supply-side terminals of the discharge lamp LAMP. Then, the switching element S1 and the switching element S2 are alternately turned on and off by a drive signal from the control circuit 2, thereby converting the voltage Vdc across the smoothing capacitor C into an AC high-frequency voltage. It is supplied to the discharge lamp LAMP via Co. Further, at least the switching elements S1 and S2 constitute an inverter.

In this circuit, a DC voltage is used as the control signal 3, and the dimming and extinguishing of the discharge lamp LAMP are performed by changing the oscillation frequency of the inverter by, for example, changing between 0V and 10V. That is, as shown in FIG.
The output of the discharge lamp LAMP is dimmed by changing the voltage at 9 V or less, and is turned off when the DC voltage exceeds 9 V.

[0005] In order to instantaneously change the discharge lamp from the extinguished state to the lit state, as shown in JP-A-6-223991, when the lamp is extinguished, a preheating state in which the lamp can be turned on instantaneously and the lamp applied voltage is re-ignited. The oscillation frequency of the inverter is shifted so as not to reach the voltage, and when the lamp is lit, the oscillation frequency of the inverter is shifted so that the lamp applied voltage becomes the re-ignition voltage.

When the discharge lamp transitions from a lighting state to an extinguishing state by fading out as shown in FIG. 9 (a), the lamp applied voltage is reduced to a re-ignition voltage as shown in FIG. 9 (b). If the oscillation frequency of the inverter is shifted to a higher frequency that cannot be reached, the re-ignition voltage of the discharge lamp is not supplied from the inverter side, and the discharge lamp is turned off. Then, by stopping the oscillation of the inverter by the control circuit 2 for a certain time T, the power supply to the discharge lamp LAMP is cut off for a certain time T, and the discharge lamp LAMP is turned off.

FIG. 8 shows a specific example of the control circuit 2.
The circuit shown in FIG. 8 includes a series circuit of a resistor R1 and a resistor R2, a series circuit of a resistor R5 and a resistor R6, a resistor R9 and a resistor R10, which are connected in parallel with each other between input terminals of the control signal 3.
, A series circuit of resistors R3 and R4, a series circuit of resistors R7 and R8, and a resistor R1 and a resistor R2 connected in parallel between the output terminals of the external power supply Vcc.
An oscillation circuit 4 that outputs an oscillation signal corresponding to a control signal 3 input through the oscillating circuit 4; a drive circuit 5 that is driven by the oscillation signal of the oscillation circuit 4 to drive the switching elements S1 and S2; External power supply Vcc
A switching element S3 connected to the input terminal of the switch and controlling the input voltage from the external power supply Vcc;
A comparator ICo that obtains a comparison output between the voltage divided by the resistor R9 and the voltage divided by the resistor R9 and the resistor R10, and the resistor R3 and the resistor R
4 and a comparator IC1 that obtains a comparison output of the voltage division by the resistors R5 and R6, and an AND circuit IC2 that obtains an AND output of the comparator ICo and the comparator IC1.
And a timer circuit 6 that receives the output of the AND circuit IC2 and outputs a timer, and an inversion circuit IC3 that inverts the output of the timer circuit 6 and supplies the output to the switching element S3.

[0008] The oscillation circuit 4 drives the drive circuit 4 at an oscillation frequency corresponding to the DC voltage of the control signal 3. Also,
The voltage divided by the resistors R5 and R6 is the discharge lamp LAMP.
The comparator IC1 outputs a low-level signal when the voltage exceeds the reference voltage due to the voltage division of the resistors R3 and R4. (At 9 VDC). The voltage divided by the resistors R9 and R10 limits the light-off operation. If the voltage exceeds the reference voltage due to the voltage division of the resistors R7 and R8,
The comparator ICo outputs a high-level signal. (DC
9.1V). When the control signal 3 exceeds 9 V, the AND circuit IC2 outputs a high-level signal, and turns the switching element S3 off via the timer circuit 6 and the inverting circuit IC3.
F, the fixed time T set by the timer circuit 6
Only the oscillation of the oscillation circuit 4 is stopped.

[0009]

However, in the above conventional example, the following problems occur.

The time until the discharge lamp is turned off depends on the variation of the discharge lamp and the ambient temperature. As shown in FIG. 9A, the power supply to the discharge lamp LAMP is cut off for a certain time by stopping the oscillation of the inverter. May not be turned off. In this state, the preheating standby state is entered, and when the oscillation of the inverter is started again, if a voltage exceeding the re-ignition voltage of the discharge lamp LAMP occurs transiently, the tube end may become bright for a moment or in an extreme case. Reaches the re-ignition voltage of the discharge lamp LAMP, and the discharge lamp is lit (slightly discharged) in spite of the extinguishing mode.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a function for controlling the turning off / on of a discharge lamp by an external control signal, and to provide a lighting state immediately after turning off. Provided is a discharge lamp lighting device having a function of applying a preheating current when the lamp is turned off so that the discharge lamp can be shifted to the lighting state. It is.

[0012]

According to the first aspect of the present invention, there is provided an inverter for applying a high-frequency voltage to a discharge lamp, and a discharge lamp by controlling an oscillation frequency of the inverter. Control means for controlling the light output of the discharge lamp, by stopping the oscillation of the inverter for a certain time to cut off the power supply to the discharge lamp and supplying a sufficient preheating current to start the discharge lamp after a certain time has elapsed. The discharge lamp lighting device that shifts to the preheating standby state is characterized in that it detects that the high-frequency voltage has fallen below the re-ignition voltage value of the discharge lamp and shifts to the preheating standby state.

According to a second aspect of the present invention, when the discharge lamp shifts to an oscillation frequency sufficient for turning off the discharge lamp, the discharge lamp shifts to a preheating standby state.

According to a third aspect of the present invention, when the discharge lamp shifts to an oscillation frequency sufficient for turning off the discharge lamp, the process shifts to a preheating standby state.

[0015]

Embodiment

(Embodiment 1) A circuit diagram of a first embodiment according to the present invention is shown in FIG. 1, a specific circuit of the control circuit 2 is shown in FIG. 2, and an operation waveform diagram is shown in FIG.

The difference between the circuit shown in FIG. 1 and the conventional example shown in FIG. 6 is that the resistor R11 is connected between the power supply side terminals of the discharge lamp LAMP.
And a series circuit of a resistor R12, a rectifier D1 connected to both ends of the resistor R12, and a DC voltage output d of the rectifier D1 input to the control circuit 2 so that a voltage applied to the discharge lamp LAMP can be detected. The description is omitted by assigning the same reference numerals to the same components as those of the other conventional examples.

The difference between the circuit shown in FIG. 2 and the conventional example shown in FIG. 8 is that a series circuit of a resistor R13 and a resistor R14 connected between input terminals of a DC voltage output d and an external power supply V
A resistor R15 and a resistor R16 connected between the input terminals of cc
, A comparator IC7 that obtains a comparison output of the voltage divided by the resistors R13 and R14 and the voltage divided by the resistors R15 and R16, an inverting circuit IC6 that inverts the output of the comparator IC7, and a comparator. An AND circuit IC5 from which an AND output of the ICo and the inverting circuit IC6 is obtained, and an OR output of the timer circuit 6 and the AND circuit IC5 are connected to the inverting circuit IC3.
And an OR circuit IC4 for inputting the same. The same components as those of the conventional example are denoted by the same reference numerals, and description thereof is omitted.

Next, the operation will be briefly described with reference to FIG. As shown in FIG. 3C, when the lamp applied voltage falls below the detection voltage value (= reignition voltage), that is, the DC voltage output d divided by the resistors R13 and R14 is changed to the resistors R15 and R16. , The comparator IC7 outputs a high level signal, the inverting circuit IC6 outputs a low level, the AND circuit IC5 outputs a high level, the OR circuit IC4 outputs a high level, and the inverting circuit IC
3 outputs a low-level signal, and the resistance R13 and the resistance R
The switching element S3 is turned off until the DC voltage output d divided by 14 falls below the reference voltage due to the voltage division of the resistors R15 and R16, and the oscillation of the oscillation circuit 4 is stopped. When the control signal 3 becomes 9.2 V or more, the comparator IC
o outputs a low level signal, and the switching element S3 is turned on via the AND circuit IC2, the timer circuit 6, the OR circuit IC4, and the inverting circuit IC3, and starts oscillating. That is, the oscillation of the oscillation circuit 4 is stopped for the fixed time T set by the timer circuit 6, and the discharge lamp LAMP is reliably turned off at the time of transition from the on state to the off state.

(Embodiment 2) FIG. 4 shows a circuit diagram of a second embodiment according to the present invention.

The difference from the first embodiment shown in FIG. 1 is that two discharge lamps LAMP are connected in parallel to both ends of a switching element S2 via an inductor Lo and a capacitor C, and one discharge lamp LAMP is connected. Between the power supply side terminals of
1 and a series circuit of a resistor R12, and the other discharge lamp L
By connecting a series circuit of the resistor R17 and the resistor R18 between the power supply side terminals of the AMP, connecting the rectifier D1 to both ends of the resistor R12 and the resistor R18, and inputting the DC voltage output d of the rectifier D1 to the control circuit 2, That the lamp applied voltage of the two discharge lamps LAMP can be detected.
The description of the same components as those of the other first embodiment will be omitted by retaining the same reference numerals.

(Embodiment 3) FIG. 5 shows a circuit diagram of a third embodiment according to the present invention.

The difference from the first embodiment shown in FIG. 2 is that the resistors R7 to R10, the AND circuit IC2 and the AND circuit IC5 are omitted, and the outputs of the timer circuit 6 and the inverting circuit IC6 are input to the OR circuit IC4. By so doing, the configuration is such that the preheating standby state is ensured when the inverter stops oscillating. The same components as those of the first embodiment are denoted by the same reference numerals and description thereof is omitted.

[0023]

According to the first to third aspects of the present invention, the discharge lamp has an off / on control function by an external control signal and can be instantaneously shifted from the off state to the on state. In a discharge lamp lighting device having a function of applying a preheating current when turned off, it is possible to provide a discharge lamp lighting device capable of surely turning off a discharge lamp when transitioning from a lighting state to a light-off state.

[Brief description of the drawings]

FIG. 1 shows a circuit diagram of a first embodiment according to the present invention.

FIG. 2 shows a specific circuit diagram of the control circuit 2 of the embodiment.

FIG. 3 shows an operation waveform diagram of the embodiment.

FIG. 4 shows a circuit diagram of a second embodiment according to the present invention.

FIG. 5 shows a circuit diagram of a third embodiment according to the present invention.

FIG. 6 shows a circuit diagram of a conventional example according to the present invention.

FIG. 7 is a characteristic diagram showing a relationship between a control signal and an optical output ratio according to the present invention.

FIG. 8 is a specific circuit diagram of the control circuit 2 of the conventional example.

FIG. 9 shows an operation waveform diagram of the conventional example.

[Explanation of symbols]

 LAMP discharge lamp 2 control circuit

Claims (3)

[Claims] 1. An inverter for applying a high-frequency voltage to a discharge lamp, and control means for controlling the light output of the discharge lamp by controlling the oscillation frequency of the inverter, wherein the inverter stops oscillating for a fixed time. In the discharge lamp lighting device, the power supply to the discharge lamp is interrupted, and after a lapse of the predetermined time, the discharge lamp lighting device shifts to a preheating standby state for supplying a preheating current sufficient for starting the discharge lamp. A discharge lamp lighting device characterized in that the discharge lamp lighting device detects that the voltage has fallen below a re-ignition voltage value of the discharge lamp and shifts to the preheating standby state. 2. The discharge lamp lighting device according to claim 1, wherein the operation shifts to the preheating standby state when the discharge lamp shifts to an oscillation frequency sufficient for turning off the discharge lamp. 3. The discharge lamp lighting device according to claim 1, wherein the transition to the preheating standby state is performed when the oscillation frequency of the discharge lamp is changed to a sufficient oscillation frequency to turn off the discharge lamp.