JP2523396B2 - Discharge lamp lighting device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device for a dimmable discharge lamp such as a hot cathode fluorescent lamp used for back lighting of a liquid crystal display device or the like.

[Conventional technology]

Liquid crystal display devices, which are often used for displays such as laptop personal computers, use, for example, hot cathode fluorescent lamps as a light source for back lighting. This hot cathode fluorescent lamp is usually equipped with a light control means for adjusting the display brightness, and at the time of start-up, the preheat heater (cathode) is energized to preheat in advance, and then a high-voltage lighting voltage is applied. Therefore, the supply of high-voltage lighting voltage is stopped for a certain period (1-2 _SEC ) after the switch is turned on.

FIG. 3 is a block diagram showing a circuit configuration of a conventional discharge lamp lighting device for lighting a discharge lamp such as the hot cathode fluorescent lamp. In the figure, 1 is a main power source such as a battery, and 2 is an oscillating circuit including an LC circuit and the like, which outputs a sine wave oscillating signal. 3 is a driving power supply circuit including a lighting power supply (high voltage power supply) for a fluorescent lamp (discharge lamp) used in the light emitting display means 4 and a heater power supply for a preheater thereof, and 5 is a predetermined time (preheating time) at the time of starting the fluorescent lamp. ) A timer circuit that stops the supply of high-voltage lighting voltage, and starts operation when the power is turned on (when the switch is turned on). Reference numeral 6 is a dimming circuit for adjusting the brightness of the fluorescent lamp, and a voltage varying means 7 for supplying a variable power source to the input portion of the lighting power source is connected to the preceding stage. Reference numeral 8 is a cancel circuit for supplying a starting voltage (maximum voltage) for a predetermined time (starting time) when the fluorescent lamp is started, and starts the operation after the operation of the timer circuit 5 is completed. The cancel circuit 8, the oscillator circuit 2, and the timer circuit 5 are mainly powered by the main power source 1.

The fluorescent lamp used in the light emitting display means 4 has a preheat heater (cathode). When the power is turned on, the heater is energized to preheat, and then high-voltage lighting is performed from the lighting power supply in the drive power supply circuit 3. A voltage is supplied and the lamp is lit by discharging in the tube. That is, only the high-voltage lighting power supply,
The voltage supply is stopped by the timer circuit 5 until the preheating is completed.

Further, a voltage varying means 7 is connected to the front stage of the dimming circuit 6, and is adjusted by, for example, a volume (variable resistance) or the like to supply a variable power source to the input portion of the lighting power source, thereby driving the fluorescent lamp. Dimming control is performed. At that time, in order to improve the low temperature startability of the fluorescent lamp, the variable power source is set to the maximum value (Fu11 light emission) by the cancel circuit 8 when the power source is turned on.

[Problems to be Solved by the Invention]

However, in the conventional discharge lamp lighting device as described above, there is a problem that the lamp life is shortened because a high-voltage lighting voltage is applied even when the heater power supply is out of order. Since both the timer circuit and the cancel circuit are supplied from the main power source and are related to each other, the set time of the cancel circuit must be longer than the operating time of the timer circuit. ) There is a problem that the conditions cannot be set.

The present invention has been made in view of these problems, and it is an object of the present invention to obtain a discharge lamp lighting device capable of preventing the lamp life from being shortened and capable of individually setting the preheating time and the starting time. Has an aim.

[Means for solving the problem]

The discharge lamp lighting device of the present invention is configured as follows.

I. In a discharge lamp lighting device having a preheating heater, a driving power supply circuit having a lighting power supply for the discharge lamp and a heater power supply for driving the preheating heater, and an operation of receiving an output of the heater power supply, A timer circuit for operating the lighting power supply after a predetermined time, a voltage adjusting means for adjusting the input voltage of the lighting power supply, and a cancel circuit for supplying the starting voltage to the discharge lamp for a predetermined time when the discharge lamp is started. Prepare,
The cancel circuit is operated by the output after the elapse of the set time of the timer.

II. In the discharge lamp lighting device of the above I, the output power of the inverter was used as the lighting power supply and the heater power supply.

III. In the discharge lamp lighting device of the above II, the output transformer of the heater power supply is a first transformer having a primary winding, a secondary winding, and a feedback winding for control, and its primary winding and secondary winding. A second transformer having only a primary winding and a secondary winding having the same specifications as the wire is provided, and the measurement signal of the timer circuit is supplied from the output of the second transformer.

IV. In the discharge lamp lighting device according to any one of I to III above,
On the input side of the heater power supply, a series circuit of a temperature fuse provided in the electrode part of the discharge lamp was interposed.

[Action]

In the discharge lamp lighting device of the present invention, the timer circuit operates after the heater power is output, and the cancel circuit operates by the output of the timer circuit. Therefore, when the heater power fails, high-voltage lighting power is supplied to the discharge lamp. The preheating time and the starting time can be set individually.

In addition, the output transformer of the inverter is used for the heater power supply, and this output transformer is the first with the feedback winding.
And a second transformer without a feedback winding, and by supplying the measurement signal of the timer circuit from the output of the second transformer, the lighting power is reliably supplied after preheating, and the heater power It is possible to prevent overheating of the discharge lamp by interposing a temperature fuse provided on the electrode side of the discharge lamp on the input side.

〔Example〕

FIG. 1 is a diagram showing a basic circuit configuration of a discharge lamp lighting device according to the present invention. In the figure, 1 is a main power source such as a battery, 2 is an oscillation circuit including an LC circuit connected to the main power source 1 through a switch SW, 3 is a lighting power source (high voltage power source) for a discharge lamp such as a fluorescent lamp, and the like. A driving power supply circuit having a heater power supply for driving a preheating heater (cathode), 4 is a light emitting display means using the discharge lamp for back lighting, and 10 is a predetermined time (preheating time) after the heater power is output. A timer circuit for operating a high-voltage lighting power supply, which is composed of a diode D1 for half-wave rectifying the output of a heater power supply, a charging circuit for a resistor R1 and a capacitor C1, and a diode D2 on the output side. Reference numeral 11 is a switching power supply circuit which constitutes a dimming circuit together with a voltage adjusting means 12 for dimming which adjusts the input voltage of the lighting power supply, and which has a plurality of input parts and a timer circuit in the first input part (IN1). The output voltage of 10 is input, and the output voltage of the voltage varying means 12 is input to the second input section (IN2) via the resistor R3. The main part of the switching power supply circuit 11 is that an oscillation circuit, a comparator circuit, a reference power supply, a flip-flop and a plurality of gates are configured on one dedicated IC chip, and the voltage varying means 12
Is configured such that the output voltage can be manually changed using, for example, a volume. 13 is a smoothing circuit provided in the latter stage of the switching power supply circuit 11.
The switching element such as transistor Tr1 and the inductance element L that switch the input power supply by the output of
It consists of the LC circuit of 1 and capacitor C3. R4 and R5 are resistors and D5 is a diode. Reference numeral 14 denotes a cancel circuit for supplying a high-voltage starting voltage to the discharge lamp for a predetermined time (starting time) at the time of starting the discharge lamp, which is operated by the output of the timer circuit 10. The cancel circuit 14 is configured as a timer circuit having a CR charging circuit for the resistor R2 and the capacitor C2. D3 and D4 are diodes. The cancel circuit 14 and the voltage varying means 12 are supplied with power from the smoothing circuit 13.

In the circuit having the above-mentioned configuration, the discharge lamp in the light emitting display means 4 is first energized by the preheater for a certain time (set time of the timer circuit 10) at the time of starting, as in the conventional case, and during that time (1 to 2 _sec ).
Supply of high-voltage lighting voltage is stopped. Then, when the preheating is completed, the high-voltage starting voltage for all-light lighting is supplied for a fixed time (the setting time of the cancel circuit 14), and then the normal lighting voltage is supplied.

At that time, in the circuit of FIG. 1, since the output of the heater power supply in the drive power supply circuit 3 is input to the timer circuit 10,
The timer circuit 10 operates and the switch SW is turned off (OF
Since the capacitor C1 is discharged at the time of F), the timer circuit 10 operates after the heater power supply operates reliably. Therefore, even if the heater power source fails, the high-voltage lighting power source is not applied before the preheating is completed, which prevents the lamp life of the discharge lamp from being shortened.

Further, the output voltage of the timer circuit 10, that is, the voltage at the point A is input to the switching power supply circuit 11, but the voltage at the point A gradually rises with the rise of the heater power supply and reaches a predetermined voltage (in the switching power supply circuit 11). The voltage of the reference power source of
When the voltage reaches 5 V), the switching power supply circuit 11 starts operating. The output of the switching power supply circuit 11 controls the switching of the main power supply 1 in the smoothing circuit 13, and the output voltage of the main power supply 1 is DC-DC.
(DC-DC) conversion is performed, and the voltage of 12V is variably controlled from 12V to 5V. The output of this smoothing circuit 13 is supplied to the input part of the lighting power supply in the drive power supply circuit 3, and by varying this input voltage, DC dimming (not PWM dimming) of the discharge lamp at the DC level is performed. Be seen.

On the other hand, the cancel circuit 14 has the switch SW as described above.
Is configured as a timer circuit that discharges the capacitor C2 when off, and the cathode side of the diode D4 is connected to the point B (connection point of the capacitor C2 and the resistor R2), and the anode side of the diode D4 is connected to the switching power supply circuit 11. It is connected to the second input section. Then, when the voltage at the point B is low, the signal of the input section L ₀ (low level) of the switching power supply circuit 11 is input, and when the voltage at the point B gradually rises and reaches a predetermined voltage, By inputting the output signal to the input section, the cancel circuit 14 starts to operate at the same time as the operation of the switching power supply circuit 11 and the smoothing circuit 13 starts regardless of the output level of the voltage varying means 12, and the cancel circuit 14 starts operating for a certain period (0.1 ~ 0.5
_sec ) dimming is canceled. That is, the startup from the dimming state is eliminated, and the startup from the full (all) light emitting state is always performed for a substantially constant time, thereby ensuring the startability at low temperature regardless of the dimming state.

Here, since the cancel circuit 14 operates from the start of the operations of the switching power supply circuit 11 and the smoothing circuit 13 as described above and is separated from the timer circuit 10, the timer circuit
It is possible to set individual times for the cancel circuit 14 and the cancel circuit 14, that is, to set individual conditions for the above-mentioned preheating time and starting time, and it is extremely easy to adjust the settings without being influenced by each other.

The voltage varying means 12 has, for example, a center tap of a three-terminal volume as an output terminal, one of the other two terminals is connected to the output of the smoothing circuit 13, and the other is grounded via a resistor. ing. This resistance is for setting the lower limit value of the output voltage level. Further, by connecting the resistor R3 in series to the output part of the voltage varying means 12,
For example, the resistance R2 of the cancel circuit 14 and the capacitor C2 prevent the time constant of the charging circuit from changing. That is, the resistor R3 is used to increase the input impedance of the input section (IN2) of the switching power supply circuit 11. For example, the values of the resistors R2 and R3 are R2 = R3 = 10KΩ to 47K.
Ω is desirable. Further, it is necessary that the value of the volume of the voltage varying means 12 described above is sufficiently smaller than the values of the resistors R2 and R3 so that the input impedance of the switching power supply circuit 11 is not affected. Therefore, it is desirable that the value of R3 be about 5 KΩ.

FIG. 2 is a circuit diagram showing an embodiment of the present invention in which a lighting device for a hot cathode fluorescent lamp is applied by applying the above-mentioned circuit, and the same reference numerals as those in FIG. 1 indicate corresponding parts. The main power supply 1 is composed of, for example, a vehicle-mounted 12V battery. Oscillation circuit 2
Are provided in two systems corresponding to the lighting power supply 3a and the heater power supply 3b of the drive power supply circuit 3, and the inductance elements L2a, L2a,
LC circuit of L2b and capacitors C4a, C4b and inverters 2a, 2b
It has. The inverter 2a consists of transistors Tr2a and Tr3.
a, a capacitor C5a and resistors R6a and R7a. Similarly, the inverter 2b is similarly composed of transistors Tr2b and Tr3b, a capacitor C5b and resistors R6b and R7b. The lighting power source 3a and the heater power source 3b are configured by using the output transformers of the inverters 2a and 2b. In addition, C6
Is a smoothing capacitor.

The drive power supply circuit 3 has the high-voltage lighting power supply 3a and the heater power supply 3b as described above, and the above-mentioned inverter
It is configured using output transformers 2a and 2b. The lighting power source 3a has a single transformer T1 and includes a feedback winding for control in addition to the primary winding and the secondary winding. The heater power supply 3b includes a first transformer T2 having a primary winding, a secondary winding, and a feedback winding for control, and a primary winding and a secondary winding having the same specifications as the primary winding and the secondary winding. The second transformer T3 having only the line is provided, and the measurement signal of the timer circuit 10 is supplied from the output of the second transformer T3. Then, the lighting power source 3a and the heater power source
Each secondary winding 3b is connected to the electrodes of the hot cathode fluorescent lamps FL1 to FL4 which are discharge lamps in the light emitting display means 4.

Further, in the switching power supply circuit 11, the switching power supply 11a of the main part is integrated into an IC as described above, and the LC circuit of the inductance element L3 and the capacitor C7 is provided in the input part. As described above, the voltage detecting means 12 is a volume controller.
The center tap of VR1 serves as an output terminal, one end of this volume VR1 is connected to the smoothing circuit 13 and the cancel circuit 14 via the resistor R8, and the other end is grounded (GND) via the resistor R3. . The smoothing circuit 13 has a two-stage configuration, and the bases of the switching transistors Tr1a and Tr1b are connected to the switching power supply circuit 11 via resistors R4a and R4b.
Of the transistors Tr1a and Tr1b, and resistors R5a and R5b are connected between the emitters and bases of the transistors Tr1a and Tr1b.
Further, an RC circuit of a resistor R10 and a capacitor C8 is connected to the output side of each transistor Tr1a, Tr1b, and a capacitor C9 is connected to the input part of one switching circuit.

A series circuit of temperature fuses F1 to F8 provided on each electrode portion of the fluorescent lamps FL1 to FL4 is provided on the input side of the heater power source 3b (in the example shown in the figure, before the oscillation circuit 2). .

In FIG. 2, F9 is a power fuse, C10 to C26 are capacitors, R11 to R14 are resistors, and P1 to P13 are connector terminals.

In the circuit of FIG. 2, the output voltage of the heater power supply 3b is detected by the output of the second transformer T3 having no feedback winding. This is because, for example, when the first transformer T2 fails, the oscillation circuit 2 connected to the transformers T2 and T3 stops oscillating and the outputs of the transformers T2 and T3 disappear. Further, when the second transformer T3 fails, the oscillation of the oscillation circuit 2 continues if the first transformer T2 is normal, but since the second transformer T3 fails,
There is no T3 output. Therefore, by detecting the output of the second transformer T3, both outputs of the transformers T2 and T3 can be detected.

The temperature fuses F1 to F8 are fluorescent lamps FL1 to FL4.
Are arranged on the left and right electrode parts (near the filament). This is to prevent overheating of the fluorescent lamps FL1 to FL4. That is, the emitter (electron emissive) substance applied to the filaments of the fluorescent lamps FL1 to FL4 gradually evaporates with the passage of time of discharge, and if this disappears, the filament will overheat and adversely affect the surrounding lamps and lighting circuits. Sometimes. Therefore, when the above-mentioned emitter material is exhausted, the life of the fluorescent lamp is determined and
Power supply is stopped at the set temperature of F1 to F8 (about 102 ℃). At that time, since each of the temperature fuses F1 to F8 is connected in series, the heater power supply 3b is stopped regardless of which of the temperature fuses is in the open state, and accordingly the timer circuit 10
With the function of, the high-voltage lighting power supply is also forcibly stopped. Therefore, the rated capacities of the temperature fuses F1 to F8 can be determined only by the capacity of the current consumption of the power supply unit on the heater side and can be set with a small capacity.

Here, in the above-described embodiment, the timer circuit 10 has both the operation detection function of the heater power supply 3b by the diode D1 and the capacitor C1, and the high voltage driving timer function of the lighting power supply 3a by the resistor R1 and the capacitor C1. , The number of parts is reduced and the cost is reduced. In addition, since a dedicated IC is used for the switching power supply circuit 11, the number of parts is similarly reduced, and even when multiple fluorescent lamps are turned on, it is possible to change the constants of some parts and increase the transformer of the heater power supply 3b. It is possible to easily turn on a large number of fluorescent lamps at a minimum cost. Furthermore, heater power supply 3b
At the time of failure, not only the supply of the high voltage power supply is stopped, but also the determination of the failure can be easily confirmed by turning on or off the lamp.

〔The invention's effect〕

As described above, according to the present invention, the timer circuit operates after a predetermined time has elapsed from the time when the heater power was output,
When the heater power fails, the high-voltage lighting power is not supplied to the discharge lamp, preventing the lamp life from being shortened.
Further, since the cancel circuit operates by the output after the elapse of the set time of the timer, there is an effect that the preheating time and the starting time can be individually set.

In addition, by using the output transformer of the inverter as the heater power supply and dividing this transformer into a plurality of parts to obtain the measurement signal of the timer circuit from the transformer without the feedback winding, the discharge lamp can be reliably operated after the heater is preheated. Further, the series circuit of the temperature fuses provided in the electrode portion of the discharge lamp is provided on the input side of the heater power source so that the discharge lamp can be prevented from overheating with the temperature fuse having a small capacity.

[Brief description of drawings]

FIG. 1 is a basic circuit configuration diagram of a discharge lamp lighting device according to the present invention, and FIG. 2 is a circuit diagram showing an embodiment of the present invention as a lighting device for a hot cathode fluorescent lamp by applying the circuit of FIG. , Third
The figure is a block diagram showing a circuit configuration of a conventional device. 1 ... Main power supply 2 ... Oscillation circuit 2a, 2b ... Inverter 3 ... Drive power supply circuit 3a ... Lighting power supply 3b ... Heater power supply 4 ... Emitting display means 10 ... Timer circuit 11 ... Switching power supply circuit 12 ...... Voltage changing means 13 ...... Smoothing circuit 14 ...... Cancellation circuit FL1 to FL4 ...... Hot cathode fluorescent lamp (discharge lamp) T2 ...... First transformer T3 ...... Second transformer F1 to F8 ...... Thermal fuse

Claims (4)

(57) [Claims] 1. A discharge lamp lighting device having a preheating heater, wherein a driving power supply circuit having a lighting power supply for the discharge lamp and a heater power supply for driving the preheating heater and an operation of receiving an output of the heater power supply are operated. A timer circuit that starts and operates the lighting power supply after a predetermined time, a voltage adjusting means for adjusting the input voltage of the lighting power supply, and a cancel for supplying the starting voltage to the discharge lamp for a predetermined time when the discharge lamp is started A discharge lamp lighting device, comprising: a circuit, wherein a cancel circuit is operated by an output after a lapse of a set time of the timer. 2. The discharge lamp lighting device according to claim 1, wherein an output transformer of an inverter is used for the lighting power supply and the heater power supply. 3. The output transformer of the heater power supply has a first transformer having a primary winding, a secondary winding, and a feedback winding for control, and a transformer having the same specifications as the primary winding and the secondary winding. The discharge lamp lighting device according to claim 2, further comprising: a second transformer having only a primary winding and a secondary winding, and the measurement signal of the timer circuit is supplied from an output of the second transformer. 4. The discharge lamp lighting device according to claim 1, wherein a series circuit of a temperature fuse provided in an electrode portion of the discharge lamp is provided on the input side of the heater power supply.