JP2658042B2 - Discharge lamp lighting device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a device for lighting a preheated discharge lamp such as a fluorescent lamp, and more particularly, to a device for switching the discharge lamp between at least a full light state and a predetermined dimming state. The lamp can be lit at two dimming levels, and at the time of starting, the inverter is set to the same operating state as the predetermined dimming state, thereby preheating the discharge lamp without lighting, thereby ensuring the lamp life. The present invention relates to a discharge lamp lighting device.

[Related Art] When a so-called cold start in which a preheated discharge lamp (lamp) is discharged (lighted) without being sufficiently preheated is repeated, the life of the lamp is shortened, such as so-called blackening. Therefore, DC power is converted to AC power (for example, 20 to 100 kHz).
Conventionally, a device for lighting such a lamp with this AC power has a voltage applied to the lamp for a predetermined time immediately after the power is turned on, and the voltage applied to the lamp is kept at a level lower than the discharge starting voltage of the lamp to light the lamp. It has a so-called soft-start function that preheats without doing so.

[Problems to be Solved by the Invention] By the way, in order to provide such a soft start function, conventionally, terminals between both filaments of the lamp that are not connected to the inverter transformer are short-circuited only during the preheating period. The winding for supplying lamp current and the filament winding are wound independently on the inverter transformer, and the lamp current supply circuit is cut off during preheating, or
As described in Japanese Patent No. 956, a switching transistor of a constant current push-pull inverter is operated in class A only during a preheating period to reduce a voltage applied to a lamp.

However, the conventional lighting device has a disadvantage that the circuit configuration is complicated and the cost is high because the soft start circuit is provided separately from the dimming circuit.

SUMMARY OF THE INVENTION In view of the above-mentioned problems in the conventional type, an object of the present invention is to provide a switching frequency and / or a switching frequency in an inverter.
Another object of the present invention is to provide a discharge lamp lighting device for dimming a lamp by varying the on / off duty so as to add a soft start function for ensuring lamp life with a simple circuit configuration and at low cost.

Means for Solving the Problems In order to achieve the above object, the present invention provides an inverter that generates an AC output from a DC power supply, and switches the inverter to two or more modes having different switching frequencies and / or on / off duties. In a discharge lamp lighting device that operates the lamp with all light and dimming operation, the inverter is set to the same operating state as that at the time of dimming lighting at the time of starting, and the lamp is preheated.

[Operation and Effect] According to the above configuration, the lamp life can be ensured by the soft start function of keeping the voltage applied to the lamp low when the lamp is preheated. Further, the soft start circuit for this purpose only controls the dimming circuit with a timer, so that it can be realized with a simple circuit configuration and at low cost.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a block circuit of a discharge lamp lighting device according to one embodiment of the present invention. The apparatus shown in FIG. 1 includes a DC power supply circuit 1, an inverter circuit 2, a dimming switching circuit 3, an all-optical starting circuit 4, a soft start circuit 5, a power supply voltage / temperature compensation circuit 6, a no-load stop circuit 7, and a switching improvement circuit. 8 is provided.

The DC power supply circuit 1 includes a full-wave rectifier circuit DB and a smoothing capacitor C4, and generates a smoothed DC voltage from an AC power supply (not shown).

The inverter circuit 2 uses a quasi-E class self-excited single-transistor inverter circuit. An LC resonance circuit including an inductor L1 and a capacitor C1 and a current limiting (current limiting) are provided between the collector of the switching transistor Tr1 and the DC power supply positive terminal a. Ballast) inductor L2 and fluorescent lamp FL as load
The feedback winding connected to the inductor L2
One end of L2f is connected to the base of the transistor Tr1 via a series circuit of the capacitor C3 and the inductor L3, and the other end is connected to the DC power supply negative terminal b. In addition, transistor Tr
A variable resistor VR is connected between the base of the DC power supply 1 and the DC power supply negative terminal b, and the emitter of the transistor Tr1 is connected to the DC power supply negative terminal via a diode D7. Further, a lamp starting capacitor C2 is connected between the non-power supply side terminals f2 and f4 of each filament of the fluorescent lamp FL.

Next, the operation of the inverter circuit 2 will be described. In FIG. 1, when an AC power supply (not shown) is turned on and a DC voltage is generated from the DC power supply circuit 1, a base current is supplied to the transistor Tr1 via a startup resistor (not shown), and the collector current of the transistor Tr1 is connected to the inductor L1. Parallel resonance circuit with capacitor C1 and inductor L2 and capacitor
Flows through a series resonant circuit with C2. As a result, the transistor Tr1 starts oscillating due to positive feedback from the collector to the base via the inductor L2, the feedback winding L2f, the capacitor C3 and the inductor L3, and resonance of the collector circuit including L1, L2, C1, and C2. .

In FIG. 1, a capacitor C3 and an inductor L3
Is for reducing the switching loss of the transistor Tr1 by extracting the base current when the transistor Tr1 is turned off. The variable resistor VR transfers the charge stored in the capacitor when the transistor Tr1 is turned on to the transistor Tr1.
This is a capacitor reset resistor that is discharged when 1 is off.

The inverter circuit 2 can vary the oscillation frequency of the inverter circuit 2 by varying the reset resistor VR. That is, referring to FIG. 2, during the ON period Ton of the transistor Tr1, a base current flows through the transistor Tr1 via the capacitor C3, and the direction of the capacitor C3 becomes + on the feedback winding L2f side and − on the base side of the transistor Tr1. Is charged. The electric charge of the capacitor C3 is discharged through the variable resistor VR and the inductor L3 by the voltage induced in the feedback winding L2f in the reverse direction during the next off period TOff of the transistor Tr1.

When the resistance value of the variable resistor VR is increased, the time constant of discharge (reset) of the capacitor C3 becomes longer. Here, the off period TOff of the transistor Tr1 is substantially constant because it is determined by the resonance system connected to the collector of the transistor Tr1. Therefore, the amount of charge discharged during the off period TOff of the transistor Tr1, that is, the amount of charge that can be charged during the on period Ton is reduced. That is, when the transistor Tr1 is on, the capacitor C3 is charged early when the base current of the transistor Tr1 flows, and the base current of the transistor Tr1 decreases early and is turned off by the positive feedback. As a result, the ON period Ton of the transistor Tr1 is shortened, and the oscillation frequency increases.

In this device, since the natural frequency of the collector load resonance system of the transistor Tr1 is set lower than the oscillation frequency of the inverter circuit 2, the lamp current is reduced by increasing the oscillation frequency of the inverter circuit 2 and moving it away from the natural frequency. On the other hand, if the oscillation frequency of the inverter circuit 2 is decreased to approach the natural frequency, the lamp current increases.
Therefore, in this device, the lamp FL is set to a predetermined value to turn on the lamp FL with all light, and the oscillation of the inverter circuit 2 is changed or changed to a value higher than the resistance of the variable resistor VR. By increasing the frequency and reducing the lamp current, the lamp FL can be dimmed and lit.

The dimming switching circuit 3 includes a dimming / all-light switching switch and the like, and is a circuit for setting a lighting state of the lamp FL in a steady state.

The soft start circuit 5 operates the inverter circuit 2 in the same state as the time of dimming for a predetermined time immediately after the power is turned on, keeps the voltage applied to the lamp FL lower than the discharge start voltage, and preheats the lamp FL without lighting it. Circuit for

After the lamp FL is sufficiently preheated by the above preheating, the all-light starting circuit 2 operates the inverter circuit 2 in the same state as in the case of all light, applies a voltage sufficiently higher than the discharge starting voltage to the lamp FL, and starts the lamp FL. This is a circuit for lighting.

The power supply voltage / temperature compensation circuit 6 controls the resistance value of the variable resistor VR of the inverter circuit 2, that is, the oscillation frequency, compensates for lamp power fluctuation due to power supply voltage fluctuation, and raises the lamp voltage at low temperature to increase the starting characteristics and the lamp. Compensate for brightness.

The no-load stop circuit 7 is used to remove the lamp FL,
This is a circuit for detecting an unloaded state such as a one-way discharge state and stopping the operation of the inverter circuit 2.

The switching improvement circuit 8 is a circuit for further improving the switching characteristics of the transistor Tr1 of the inverter circuit 2.

Since the operations of these circuits 3 to 8 are common to those of the apparatus of FIG. 3, description will be made with reference to a more detailed circuit diagram of FIG.

FIG. 3 shows a circuit configuration of a discharge lamp lighting device according to a second embodiment of the present invention. In this device, two lamps FL1 and FL2 are lit in series.

Also, a transistor Tr8 is used instead of the variable resistor VR in FIG.
And the like. Variable resistor VR
1 is for adjusting the operating point of the transistor Tr8. The equivalent resistance of the transistor Tr8 changes according to the base current supplied from the power supply voltage / temperature compensation circuit 6. In the device of FIG. 3, the base of the transistor Tr8 has a lower voltage (determined by the zener voltage of the zener diode ZD) according to the operations of the soft start circuit 5, the all-optical start circuit 4, and the dimming switching circuit 3. A current flows based on a voltage obtained by further compensating for two types of voltages, that is, a higher voltage (during all light) determined by the rectified output of the diode D6 and a power supply voltage and temperature.

 Next, the operation of the apparatus shown in FIG. 3 will be described.

In FIG. 3, a rotary switch SW1 serves both as a power switch and an all-light / dimming changeover switch, and is set to the position shown in FIG. For example, AC power of 100 V is supplied from a power supply AC. During all light, AC power is supplied only to the DC power supply circuit 2.

When the rotary switch SW1 is switched from the power-off state to the dimming state, the AC voltage from the AC power supply AC is composed of a protection circuit composed of a fuse F, a positive temperature coefficient thermistor PTH, etc. and a varistor ZNR and a balance transformer T1 etc. Is supplied to the DC power supply circuit 1 through a noise prevention / surge absorption circuit. The DC power supply circuit 1 converts this AC voltage into a full-wave rectifier circuit.
Rectified by DB and smoothed by capacitor C4 to generate DC voltage. This DC voltage is applied to the starting resistor R3 of the inverter circuit 2.
It is supplied to the base of the switching transistor Tr1 via the switching transistor Tr1. Thereby, the inverter circuit 2 starts oscillating,
An AC voltage Vc1 (FIG. 2) is generated at the collector of the transistor Tr1. The single-turn transformer T2 has a winding L1 that forms a parallel resonance circuit with the capacitor C6, and also boosts the AC voltage Vc1 and passes through the inductor L2, which is the primary winding of the transformer T3, to a lamp including the capacitor C2 and the lamps FL1 and FL2. Apply to the circuit.

Here, since the lamps FL1 and FL2 are not yet lit and are in an open state, the Q of the resonance system connected to the collector of the transistor Tr1 is high. Therefore, the inductor L
A larger current flows through the path of 1, L2, capacitor C2 and fluorescent lamps F1 and F2 than when the inductor L2 and capacitor C2 and the like are turned on due to resonance, whereby the fluorescent lamps F1 and F2 are preheated. At this time, a higher voltage is generated at both ends of the capacitor C2, that is, at both ends of the series circuit of the fluorescent lamps F1 and F2, than at the time of lighting due to the resonance, and this voltage is discharged when the fluorescent lamps F1 and F2 are cooled. If the voltage is higher than the starting voltage, the fluorescent lamps F1 and F2 are immediately turned on (cold start) without being preheated after the power is turned on. To prevent such a cold start, a soft start circuit 5 described later is provided. The AC voltage induced in the secondary winding of the transformer T3 is rectified and smoothed by the diode D6 and the capacitor C17, and supplied to the circuits 3 to 7.

The soft start circuit 5 will be described below with reference to the time chart of FIG. 4. When the power is turned on, the terminal voltage of the capacitor C13 of the all-optical start circuit 4 is zero and the transistor Tr5 is off. The transistor Tr6 is on. Therefore, from the soft start circuit 5, the same voltage as that at the time of dimming, which is the zener voltage of the zener diode ZD, is applied to the base of the transistor Tr8 of the variable resistance circuit VR via the power supply voltage / temperature compensation circuit 7. As a result, the equivalent resistance of the transistor Tr8 becomes the same higher resistance value as that at the time of dimming, the oscillation frequency of the inverter circuit 2 is higher than that at the time of the all-optical mode operation, and the current flowing through the resonance circuit and the voltage generated across the capacitor C2. Operate in a dimming mode lower than in the all-optical mode operation. The current and the voltage in the dimming mode can be set by selecting the value of the capacitor C2 without substantially affecting the lighting characteristics. Here, the voltage generated across the capacitor C2 when the lamps F1 and F2 are off is lower than the voltage at which the lamps F1 and F2 start discharging when the inverter circuit 2 is operated in the dimming mode. Is set so as to be higher than the voltage at which the lamps F1 and F2 are started to discharge.

In the all-light starting circuit 4, the capacitor C13 is charged via the resistor R9. Then, after turning on the power, the capacitor C1
When the terminal voltage of terminal 3 rises and the transistor Tr5 is turned on by a voltage obtained by dividing the terminal voltage by the resistors R12 and R13 (time t1 in FIG. 4), the transistor of the soft start circuit 5
Tr6 turns off, the base current of the transistor Tr8 of the variable resistance circuit VR switches to the larger one, and the inverter circuit 2 enters the all-optical mode. As a result, a voltage higher than the discharge starting voltage is applied to the lamps F1 and F2, and the lamps F1 and F2 start discharging and turn on. After lighting, since the lamps F1 and F2 connected in parallel with the starting capacitor C2 have low impedance, the Q of the load resonance system decreases, and the lamps F1 and F2 are stably lit by limiting the current by the inductor L2. I do.

In the dimming switching circuit 3, an AC voltage input via the rotary switch SW1 set to a dimming state is rectified and smoothed by the diode D1 and the capacitor C12 and supplied to the base of the transistor Tr2. As a result, the transistor Tr2 is turned on and the transistor Tr3 is turned off.

In this state, in the all-light starting circuit 4, the capacitor
C13 is further charged through the resistor R9 and its terminal voltage rises, and the transistor Tr4 is turned on by the voltage obtained by dividing this terminal voltage by the resistors R10 and R11 (time t2 in FIG. 4).
Transistor Tr5 is turned off and the soft start circuit 5
Transistor Tr6 is turned on, the base current of the transistor Tr8 of the variable resistance circuit VR is switched to the smaller one, and the inverter circuit 2 enters the dimming mode. Thereby, the lamps F1 and F2 are turned on in the dimming state thereafter.

On the other hand, when the rotary switch SW1 is set to the all-light lighting position, no AC voltage is supplied to the dimming switching circuit 3, and the transistor Tr2 is turned off. Therefore, the transistor Tr3 is turned on, the transistor Tr4 is turned off, the transistor Tr5 is turned on, and the transistor Tr6 is turned off.The higher current flows through the base of the transistor Tr8 of the variable resistance circuit VR, and the equivalent resistance value of the transistor Tr8 is lower. Therefore, the inverter circuit 2 is in the all-optical mode. As a result, the lamps F1 and F2 are all lit.

In FIG. 4, a solid line indicates the operation of each unit when the rotary switch SW1 is set to the dimming state, and a broken line indicates the operation of each unit when the rotary switch SW1 is set to the all-light state.

In addition, as can be seen from the above, in this device,
The capacitor C13 and the resistor R9 also serve as a timer circuit for both the soft start circuit 5 and the all-light lighting circuit 4.

In the power supply voltage / temperature compensation circuit 6, a voltage obtained by dividing the DC limit voltage by the resistor R1 and the thermistor ER2 is applied to the base of the transistor Tr7. Therefore, when the power supply voltage increases, the base voltage of the transistor Tr7 increases, the collector current of the transistor Tr7, that is, the base current of the transistor Tr8 decreases, the equivalent resistance value of the transistor Tr8 increases, and the oscillation frequency of the inverter circuit 2 increases. Rise and the lamp current decreases. On the other hand, when the power supply voltage decreases, the lamp current increases contrary to the above. This makes it possible to stabilize the lamp current with respect to fluctuations in the power supply voltage.

When the temperature decreases, the resistance values of the thermistors ER1 and ER2 decrease. Then, the emitter voltage of the transistor Tr7 increases due to the decrease in the resistance value of the thermistor ER1,
The decrease in the resistance value of the thermistor ER2 lowers the base voltage of the transistor Tr7. Therefore, the transistor Tr7
, The base current of the transistor Tr8 increases, the equivalent resistance value of the transistor Tr8 decreases, the oscillation frequency of the inverter circuit 2 decreases, and the lamp voltage during start-up and the lamp current during lighting increase. Thereby, the starting performance at low temperature and the light output at low temperature lighting can be ensured.

In the device shown in FIG. 3, when the lamps F1 and F2 are off, that is, when there is no load, a resonance current by the inductor L2 and the capacitor C2 flows through the transistor Tr1. Since this resonance current is larger than when the lamp is turned on, if this state continues, stress will be accumulated in the transistor Tr1, or in the worst case, the transistor Tr1 will be thermally runaway and destroyed. The no-load stop circuit 7 is for preventing this.

At no load, a larger current flows through the inductor L2 than at the time of load. Therefore, the voltage induced in the secondary winding L2s of the transformer T3 is larger when no load is applied. In the no-load stop circuit 7, when no load is applied, the rectified output of the diode D6 rises, and if this state continues for a predetermined time, the capacitor C14
Is charged via the resistors R17, R18, etc., and the terminal voltage increases. When this terminal voltage becomes higher than the ON voltage of the constant voltage element SB5, SB5 turns on. This allows
The thyristor SCR turns on, the transistor Tr9 turns on and the transistor Tr1 turns off, and the inverter circuit 2 stops oscillating. This stop state continues until the power is once turned off and turned on again.

FIG. 5 shows a circuit configuration of a discharge lamp lighting device according to a third embodiment of the present invention. The device shown in the figure is a dimming switching circuit 3, an all-light lighting circuit 4, a soft start circuit 5 of the device shown in FIG.
Also, the no-load stop circuit 7 is formed as an IC except for a time constant circuit. In the apparatus shown in FIG. 5, a time constant for soft start and a time constant for all-light lighting are separately provided.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a discharge lamp lighting device according to one embodiment of the present invention, FIG. 2 is a waveform diagram of each part of the inverter circuit in FIG. 1, and FIG. 3 is another embodiment of the present invention. FIG. 4 is a circuit diagram of the discharge lamp lighting device, FIG. 4 is a timing chart for explaining the operation of each part of the device of FIG. 3, and FIG. 5 is a discharge lamp lighting device according to still another embodiment of the present invention. FIG. 1: DC power supply circuit, 2: Inverter circuit, 3: Dimming switching circuit, 4: All light lighting circuit, 5: Soft start circuit.

Continuation of the front page (72) The inventor Nanjo Aoike 1-4-2, Mita, Minato-ku, Tokyo Toshiba Denshi Co., Ltd. (56) References JP-A-57-107599 (JP, A) JP-A-58-142800 (JP, A) JP-A-63-69197 (JP, A) JP-A-63-244599 (JP, A) JP-A-63-245275 (JP, A) JP-A-63-4598 (JP, A) Sho 63-244594 (JP, A) Sho 58-66599 (JP, U)

Claims (1)

(57) [Claims] An inverter having a switching element and generating an AC output from a DC power supply, a preheated discharge lamp that is supplied with the AC output and lights up, and a variable on / off duty and / or frequency of the switching element. Then, the inverter is driven by the discharge lamp to emit all light.
And the second mode in which the discharge lamp is lit in a predetermined dimming state
A discharge lamp lighting device comprising dimming control means for setting at least two operation modes, the first operation of the inverter in the second mode at the time of starting, and the preheating without discharging the discharge lamp. Then, the discharge lamp is started to discharge by operating in the first mode, and thereafter, the discharge lamp is operated in the operation mode set by the dimming control means, so that the discharge lamp is all-lighted or dimmed. A discharge lamp lighting device comprising a timer control means.