JP2001313189A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To support start of a cold-cathode discharge lamp by lighting auxiliary light source like a LED, an electric bulb or the like only when it is difficult to light because of darkness or the like. SOLUTION: For the discharge lamp lighting device comprising a cold-cathode discharge lamp 3, an inverter lighting device 2 lighting the cold-cathode discharge lamp, and a auxiliary light source 1, the light source 1 is turned on only when the output voltage Vo, which is detected by the inverter lighting device 2, exceeds the prescribed voltage, or only when the output current does not flow at the state that the power source is turned on. The current, flowing when the light source 1 is lighted, is limited within a prescribed current.

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 for lighting a cold cathode discharge lamp.

[0002]

2. Description of the Related Art Generally, a cold cathode discharge lamp is discharged by applying a lighting voltage to its electrode, and electrons are emitted from a cathode side electrode. It is considered that these electrons are generated by irradiation of the cathode side electrode with an electron beam such as light or cosmic rays, or by electrons escaping from residual ions. If the cold cathode discharge lamp is left in the dark, efficient excitation by light is lost, and the residual ions disappear with the passage of time. Therefore, when the cold cathode discharge lamp is left for a long time in the dark, it is necessary to rely only on cosmic rays and escaped electrons to turn on the cold cathode discharge lamp.

There is an inverter lighting device for efficiently lighting a cold cathode discharge lamp. However, when lighting is performed in a dark state, the time required for lighting is extremely long. Although there is a means for increasing the voltage to be applied to increase the probability of starting, the voltage that can be output from the inverter lighting device is limited by the size and the withstand voltage resistance, and there is a problem that it cannot be adequately dealt with.

In order to solve this problem, for example, Japanese Patent Laid-Open No. 4-71
No. 158 proposes to provide an auxiliary light source for irradiating light toward a cold cathode discharge lamp. As a result, electron emission from the cathode side electrode of the cold cathode discharge lamp is promoted, and the start-up becomes quick.

[0005]

However, in the above-mentioned known example, the auxiliary light source is always turned on when the cold cathode discharge lamp is turned on. Therefore, the auxiliary light source is turned on even when it is not dark, and unnecessary auxiliary light sources are not turned on. There is a problem that the efficiency is reduced by lighting. Further, when the auxiliary light source is a light bulb or the like, there is a disadvantage that the life is shortened by extra lighting.

Accordingly, the present invention has been made to solve such a problem, and a control method for turning on an auxiliary light source using an LED, a light bulb or the like only when the cold cathode discharge lamp is difficult to turn on in the dark or the like. The purpose is to propose.

[0007]

According to the discharge lamp lighting device of the present invention, as shown in FIG. 1, a cold cathode discharge lamp 3 and a cold cathode discharge lamp 3 are provided to solve the above-mentioned problems. In the discharge lamp lighting device including the inverter lighting device 2 to be turned on and the auxiliary light source 1, the output voltage Vo of the inverter lighting device 2 is detected, and the auxiliary light source 1 is turned on only when the output voltage exceeds a predetermined output voltage. It is characterized by the following.

[0008]

(Embodiment 1) FIG. 1 is a circuit diagram of Embodiment 1 of the present invention. The lighting device includes a cold cathode discharge lamp 3, an inverter circuit 2 for lighting the cold cathode discharge lamp 3, a power supply Vdd for the inverter circuit 2, and an auxiliary light source for lighting when the cold cathode discharge lamp 3 is difficult to turn on. LE
D1 and the output voltage Vo of the inverter circuit 2 are detected,
It comprises an auxiliary light source control circuit 4 for controlling on / off of the LED 1.

The auxiliary light source control circuit 4 is composed of, for example, a circuit surrounded by a broken line in FIG. 1, detects an output voltage Vo of the inverter circuit 2 by voltage dividing resistors R2 and R3, and detects the detected voltage by a diode D1 and a capacitor C1. Rectified and smoothed, and input to the base of the transistor Tr1 to turn on the transistor Tr1 with a predetermined detection voltage,
LED connected to d and the collector of transistor Tr1
The lighting control of 1 is performed. Also, the transistor Tr
A resistor R1 connected to the emitter of the transistor T1
There is a role of adjusting the collector current (current flowing through LED1) according to the magnitude of the detection voltage input to the base of r1.

Generally, the inverter circuit 2 has a characteristic that the maximum output voltage is output when the output impedance is Δ, and the output voltage decreases as the impedance decreases. Before the cold cathode discharge lamp 3 of the load is turned on, a large voltage is output because the output impedance of the inverter circuit 2 is ∞. However, when the cold cathode discharge lamp 3 is turned on, the impedance decreases, and the output voltage Vo becomes the lighting maintenance voltage. Down to. For example, in an inverter circuit having a rated lighting voltage of 350 V and a cold cathode fluorescent lamp of φ3 × 220 mm as a load, the maximum output voltage is about 1.5 KV.

At this time, if a predetermined detection voltage for turning on the transistor Tr1 of the auxiliary light source control circuit 4 is set to a value equal to or higher than the lighting voltage of the cold cathode discharge lamp 3 and equal to or lower than the maximum output voltage of the inverter circuit 2, FIG. As shown in the timing chart, the output voltage Vo is equal to or higher than the predetermined detection voltage during the period t0 to t1 from when the power is turned on until the cold cathode discharge lamp 3 is turned on, so that the base voltage of the transistor Tr1 becomes H level. Light LED1. After the cold cathode discharge lamp 3 is turned on, the output voltage Vo becomes equal to or lower than the predetermined detection voltage, so that the base voltage of the transistor Tr1 becomes L level and the LED 1 is turned off.

According to this configuration, since the auxiliary light source is turned on only before the cold cathode discharge lamp is turned on, it is possible to solve the problems of extra reduction in efficiency and shortening of service life. The current that flows when the LED 1 is lit is based on the base voltage of the transistor Tr1 and the resistance R
1 and a predetermined current flows. For example LE
Even if the power supply Vdd, which is also the power supply of D1, greatly changes,
Since the current of ED1 is limited to a predetermined value, the auxiliary light source L
It is hard to give stress to ED1. In this example, the auxiliary light source is an LED. However, it goes without saying that a similar effect can be obtained with a light bulb or the like.

Further, as shown in the example of FIG.
If a transistor Tr2 is connected to r1 in Darlington, the effect on the current adjusting resistor R1 and the detecting voltage dividing resistors R2 and R3 can be reduced by increasing the amplification degree.

(Embodiment 2) FIG. 4 shows Embodiment 2 of the present invention.
FIG. This lighting device includes a cold cathode discharge lamp 3 and
An inverter circuit 2 for lighting the cold cathode discharge lamp 3;
The power supply Vdd of the inverter circuit 2 and the cold cathode discharge lamp 3
LED1 as an auxiliary light source that lights up when it is difficult to light up,
When the output current Io of the inverter circuit 2 is detected, the LED 1
And an auxiliary light source control circuit 4 for controlling on / off of the light source.

The auxiliary light source control circuit 4 of this embodiment is constituted by a circuit surrounded by a broken line in FIG. 4, and detects an output current Io of the inverter circuit 2 by a detection resistor R2, and detects a detection voltage by a diode D1 and a capacitor C1. Rectifying and smoothing N
The voltage inverted by the OT circuit IC1 is applied to the transistor Tr1.
When the lamp current is not flowing, the transistor Tr1 is turned on, and the LED1 connected to the collector of the transistor Tr1 is turned on by the power supply Vdd.
It is turned on by the current from. Further, the resistor R1 connected to the emitter of the transistor Tr1 has a role of adjusting the collector current (current flowing through the LED1) according to the magnitude of the detection voltage input to the base of the transistor Tr1.

FIG. 6 shows a timing chart of this embodiment. During the period t0 to t1 from when the power is turned on to when the cold cathode discharge lamp 3 is turned on, the output current Io is zero, so that the base voltage of the transistor Tr1 is at the H level and the LED 1 is turned on. Further, since the output current Io flows after the cold cathode discharge lamp 3 is turned on, the transistor Tr
The 1 base voltage becomes the L level, and the LED 1 is turned off.

According to this configuration, since the auxiliary light source is turned on only before the cold cathode discharge lamp is turned on, it is possible to solve the problems of extra reduction in efficiency and shortening of service life. The current that flows when the LED 1 is lit is based on the base voltage of the transistor Tr1 and the resistance R
1 and a predetermined current flows. For example LE
Even if the power supply Vdd, which is also the power supply of D1, greatly changes,
Since the current of ED1 is limited to a predetermined value, the auxiliary light source L
It is hard to give stress to ED1. In this example, the auxiliary light source is an LED. However, it goes without saying that a similar effect can be obtained with a light bulb or the like. Also, as in the example of FIG.
C1 may be replaced with a transistor Tr2 and a resistor R3.

(Embodiment 3) FIG. 7 shows Embodiment 3 of the present invention.
FIG. This lighting device has a configuration in which the inverter circuit 2 of the first embodiment in FIG. 1 is an inverter circuit using a piezoelectric transformer driven by frequency control.
In the figure, 21 is a drive circuit, 22 is a piezoelectric transformer, and 23 is a frequency control circuit. Piezoelectric transformers have a steep frequency characteristic and are highly load-dependent, and are well-matched to cold-cathode discharge lamp loads, and thus are often used in cold-cathode discharge lamp lighting devices.

When a piezoelectric transformer inverter is used in the configuration of the first embodiment, as shown in the timing chart of FIG. 8, the output voltage Vo of the piezoelectric transformer inverter turns on the cold cathode discharge lamp 3 after the power is turned on. During the period t0 to t2, the time increases in proportion to time. This is because the frequency is controlled so as to gradually approach the resonance frequency from a frequency fH sufficiently higher than the resonance frequency of the piezoelectric transformer. When the output voltage Vo increases with time in this manner, the transistor Tr1 of the auxiliary light source control circuit 4
At time t1 when a predetermined detection voltage is reached to turn on LED1
Starts to light up. After the cold cathode discharge lamp 3 is turned on at time t2, the output voltage Vo becomes equal to or lower than the predetermined detection voltage, so that the base voltage of the transistor Tr1 becomes L level and the LED 1 is turned off.

In this case, for example, when the cold cathode discharge lamp is in a light place and is in a state where it is easy to start and light, the cold cathode discharge lamp is turned on before the output voltage Vo reaches a predetermined detection voltage.
At this time, the auxiliary light source LED1 does not need to be turned on. In other words, according to this configuration, the auxiliary light source is not only turned on until the cold cathode discharge lamp is turned on, but also emits light only when the cold cathode discharge lamp is difficult to turn on. The problem of shortening the life can be solved. The current flowing when the LED 1 is lit is based on the base voltage of the transistor Tr1 and the resistance R
A predetermined current determined by 1 flows. For example LE
Even if the power supply Vdd, which is also the power supply of D1, greatly changes,
Since the current of ED1 is limited to a predetermined value, the auxiliary light source L
It is hard to give stress to ED1. In this example, the auxiliary light source is an LED. However, it goes without saying that a similar effect can be obtained with a light bulb or the like.

(Embodiment 4) FIG. 9 shows Embodiment 4 of the present invention.
FIG. This lighting device has a configuration in which a diode D is connected to an output terminal in the inverter circuit 2 of the first embodiment in FIG. The cold cathode discharge lamp of the load is a neon tube 3 '. Generally, it is said that a neon tube has a higher luminous efficiency with a distorted waveform, but especially when a half-wave output is used, a half-wave lighting method is adopted for a neon load, in addition to an increase in luminous efficiency, such as prevention of moving stripes. May be In the case of a half-wave output, current flows only in one direction, and only one electrode 31 becomes a cathode. Therefore, only one electrode 31 needs to be provided with light by the auxiliary light source in the dark as shown in FIG. 10, which has the effect of reducing the number of auxiliary light sources such as LEDs. Needless to say, the same effects as those of the first embodiment can be obtained.

[0022]

According to the first or second aspect of the present invention, since the auxiliary light source is turned on only before the cold cathode discharge lamp is turned on, there is a problem that the efficiency is further reduced and the life is shortened. Can be solved. According to the configuration of claim 3, since the current of the auxiliary light source is limited to a predetermined value, it is difficult to apply stress to the auxiliary light source.

According to the structure of the fourth aspect, the auxiliary light source emits light only when the cold cathode discharge lamp is difficult to light, so that the effect can be further enhanced. According to the configuration of claim 6, only one electrode needs to supply light with the auxiliary light source, and there is an effect that the number of auxiliary light sources such as LEDs can be reduced.

[Brief description of the drawings]

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

FIG. 2 is a circuit diagram of a modification of the first embodiment of the present invention.

FIG. 3 is a waveform chart for explaining the operation of the first embodiment of the present invention.

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

FIG. 5 is a circuit diagram of a modification of the second embodiment of the present invention.

FIG. 6 is a waveform chart for explaining the operation of the second embodiment of the present invention.

FIG. 7 is a circuit diagram according to a third embodiment of the present invention.

FIG. 8 is a waveform chart for explaining the operation of the third embodiment of the present invention.

FIG. 9 is a circuit diagram according to a fourth embodiment of the present invention.

FIG. 10 is an explanatory diagram showing a main part configuration of a fourth embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 LED (auxiliary light source) 2 inverter circuit 3 cold cathode discharge lamp 4 auxiliary light source control circuit

Claims (6)

[Claims] 1. A discharge lamp lighting device comprising a cold cathode discharge lamp, an inverter lighting device for lighting the cold cathode discharge lamp, and an auxiliary light source, wherein an output voltage of the inverter lighting device is detected and a predetermined output voltage is detected. A discharge lamp lighting device characterized in that the auxiliary light source is turned on only when the above occurs. 2. In a discharge lamp lighting device comprising a cold cathode discharge lamp, an inverter lighting device for lighting the cold cathode discharge lamp, and an auxiliary light source, a power supply is turned on by detecting an output current of the inverter lighting device. A lighting device for lighting the auxiliary light source only when no output current flows. 3. The discharge lamp lighting device according to claim 1, wherein a current flowing when the auxiliary light source is turned on is limited to a predetermined current value or less. 4. The discharge lamp lighting device according to claim 1, wherein the inverter lighting device increases the output voltage at the time of starting in proportion to time. 5. The discharge lamp lighting device according to claim 4, wherein the inverter lighting device has a piezoelectric transformer driven by frequency control. 6. The discharge lamp lighting device according to claim 1, wherein the inverter lighting device has a half-wave output.