JP2830041B2 - Discharge lamp lighting device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device, and more particularly to an improvement in an inverter circuit thereof.

[Prior Art] In recent years, a discharge lamp lighting device for lighting a discharge lamp such as a fluorescent lamp at a high frequency using an inverter circuit has been developed, and the discharge lamp lighting device has been reduced in size and weight and luminous efficiency has been improved.
An optical output without flicker can be obtained.

Conventionally, as such a discharge lamp lighting device, a device provided with a one-stone self-excited inverter circuit shown in FIG. 4 is known.

The discharge lamp lighting device shown in FIG. 1 converts an AC voltage from an AC power supply 10 into a DC voltage using a full-wave rectifier 12 and a smoothing capacitor 14, supplies the DC voltage to an inverter circuit 16, converts the voltage into a high-frequency current, and lights a fluorescent lamp 18. It is to let.

In the inverter circuit 16, a parallel resonance circuit 24 including an oscillation choke 20 and a resonance capacitor 22 and a switching transistor 26 for turning on / off the parallel resonance circuit 24 are connected in series.

Further, one electrode 18a of the fluorescent lamp 18 as a load is connected to the full-wave rectifier 12 via a ballast choke 28,
The other electrode 18b is connected to a contact between the parallel resonance circuit 24 and the collector of the switching transistor 26 via the primary winding 30a of the current transformer 30.

A starting capacitor 32 is connected to the non-power supply side of the fluorescent lamp 18.

On the other hand, one end of the current transformer 30 secondary winding 30b is connected to the base of the switching transistor 26, and the other end is connected to the emitter of the switching transistor 26 via the capacitor 34.

The series circuit of the resistor 326 and the diode 38 is connected between the base and the emitter of the switching transistor 26,
The starting resistor 40 is connected to the base of the switching transistor 26.

The discharge lamp lighting device according to the illustrated example is configured roughly as described above, and its operation will be described next.

First, when the AC power supply 10 is turned on, a DC voltage rectified and smoothed by the full-wave rectifier 12 and the smoothing capacitor 14 is generated. With this DC voltage, a base current is slightly supplied to the switching transistor 26 via the starting resistor 40, and the switching transistor 26 is turned on.

Therefore, the parallel resonance circuit 24, the ballast choke 28,
Fluorescent lamp electrode 18a, starting capacitor 32, fluorescent lamp electrode 18
b, a current flows through the path of the primary winding 30a of the current transformer 30, and the switching transistor 2 is connected to the secondary winding 30b of the current transformer 30.
Current flows so that positive feedback is applied to 6 and capacitor 34
Is charged.

As a result, the base current of the switching transistor 26 increases, and the collect current also increases.

Here, since the base current of the switching transistor 26 is an oscillating current, the base current flows in the reverse direction after a certain time, and when the accumulated charge of the switching transistor 26 is exhausted, the switching transistor 26 is turned off. For this reason, the oscillation choke 20 resonates with the resonance capacitor 22 due to the electromagnetic energy accumulated in the oscillation choke 20, and a resonance voltage is generated. Due to this resonance voltage, the current limited by the ballast choke 28 is applied to the electrodes 18a of the fluorescent lamp 18,
Starting capacitor 32, fluorescent lamp 18 power 18b, current transformer 30
Flows through the primary winding 30a.

Further, a current flows through the secondary winding 30b of the current transformer 30 in a direction in which a reverse bias is applied to the base of the switching transistor 26. Then, after a certain time, a current flows again in the secondary winding 30b of the current transformer 30 in a direction in which the switching transistor 26 is turned on, and the inverter circuit 16 maintains oscillation.

In addition, the starting capacitor 32 resonates with the ballast choke 28 and the impedance is reduced.
Current flows through 18a and 18b, and at the same time, the starting capacitor 32
The fluorescent lamp 18 is turned on because a resonance voltage is generated at both ends of the fluorescent lamp 18. Then, after lighting, the current limited by the ballast choke 28 flows through the fluorescent lamp 18 to perform high-frequency lighting.

[Problems to be Solved by the Invention] However, in the above-described discharge lamp lighting device, the electrodes 18a and 18b of the fluorescent lamp 18 are lit before the electrodes 18a and 18b are sufficiently preheated. There were problems such as blackening near the electrodes, disconnection of the electrodes, etc. appearing early.

That is, the LC condition of the inverter circuit 16 changes the fluorescent lamp 18
If the condition is set so that the fluorescent lamp 18 can be maintained, a high voltage is generated across the starting capacitor 32 at the same time when the AC power supply 10 is turned on, and the fluorescent lamp 18 is immediately turned on.

On the other hand, the LC resonance condition of the inverter
If the conditions are set so that the electrodes 18a and 18b can be sufficiently preheated without turning on, the electrodes 18a and 18b are only preheated and the fluorescent lamp 18 cannot start discharging.

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the related art, and has as its object to provide a discharge lamp lighting device capable of sufficiently preheating electrodes of a discharge lamp when power is turned on and capable of discharging an appropriate discharge lamp. Is to do.

Means for Solving the Problems To achieve the above object, a discharge lamp lighting device according to the present invention includes a timer circuit for setting a desired preheating time from power-on, and the timer circuit is in a preheating period. And a preheating circuit for supplying a DC current to the secondary winding of the current transformer and for interrupting the DC current flowing through the secondary winding of the current transformer when the timer circuit has passed a preheating period. It is characterized by.

It is preferable that the preheating circuit includes a switch that conducts to a timer circuit, and a DC power supply that can supply a DC current to a secondary winding of the current transformer via the switch.

Further, the DC power supply of the preheating circuit may be a DC power supply obtained by rectifying and smoothing a voltage generated in a secondary winding wound around an oscillation choke or a ballast choke.

[Operation] The discharge lamp lighting device according to the present invention includes the above-described means. When the power is turned on, a direct current flows through the secondary winding of the current transformer for a certain period of time while the timer circuit is operating, so that both ends of the starting capacitor. The electrode is preheated while the discharge of the discharge lamp is suppressed by lowering the voltage generated in the discharge lamp. Then, after the elapse of the preheating time, the DC current flowing through the secondary winding of the current transformer was interrupted, so that the LC resonance condition of the inverter circuit became a condition for lighting the discharge lamp, and the voltage at the end of the starting capacitor increased. The discharge of the discharge lamp is started.

Therefore, since the discharge is started after the electrodes of the discharge lamp are sufficiently preheated, the blackening of the electrodes and the disconnection of the electrodes can be prevented, and good starting and lighting can be maintained.

Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a circuit configuration of a discharge lamp lighting device according to a first embodiment of the present invention, and portions corresponding to those in FIG.

A feature of the present invention is that a timer circuit and a preheating circuit are provided so as to allow sufficient time for preheating the electrodes of the discharge lamp. For this reason, in this embodiment, the timer circuit 150 and the preheating circuit 152 are provided. And

Here, the preheating circuit 152 includes a DC power supply 154 and the DC power supply.
A resistor 156 for limiting DC current of 154 and a normally closed switch 158
, A diode 160, and a series circuit including the capacitor 134 and the secondary winding 130b of the current transformer 130.

The timer circuit 150 is configured to operate for a predetermined time after the AC power supply 110 is turned on, and to turn off the switch 158.

The discharge lamp lighting device according to the present embodiment is configured as outlined above, and its operation will be described next.

First, when the AC power supply 110 is turned on, the one-stone self-excited inverter circuit 116 is activated and starts oscillating by the same operation as the conventional example.

Here, when the AC power supply 110 is turned on, the switch 158 is closed, and the DC power supply 154 supplies the resistor 156, the switch 158, the diode 160, the secondary winding 130b of the current transformer 130, and the DC power supply 154.
DC current flows through the path.

Then, by passing a DC current through the secondary winding 130b of the current transformer 130, a DC magnetic flux is generated.
The apparent saturation magnetic flux density of 0 becomes smaller. Therefore, the oscillation frequency of the switching transistor 126 is
Is higher than when is off.

Depending on the high oscillation frequency, the voltage generated between both ends of the starting capacitor 132 becomes low and the fluorescent lamp 118 cannot be turned on, but its electrodes 118a and 118b are sufficiently preheated.

Here, the timer circuit 150 is set so that the switch 158 is turned off when a certain time has elapsed after the AC power supply 110 is turned on. Then, the preheating time is set to the electrode 118a of the fluorescent lamp 118,
If the time is set so that 118b is sufficiently preheated, the switch 158 is turned off after the electrode is sufficiently preheated, and the current transformer 1 is turned off.
DC current flowing through 30 is cut off. As a result, the apparent saturation magnetic flux density of the current transformer 130 also returns to the conventional value.

Accordingly, the oscillation frequency of the switching transistor 126 becomes lower than the electrode preheating of the fluorescent lamp 118, and at the same time, the terminal voltage of the starting capacitor 132 becomes higher, so that the fluorescent lamp 118 starts discharging. In addition, since the switch 158 is kept open after lighting, the fluorescent lamp 118 maintains lighting as in the conventional case.

As described above, according to the discharge lamp lighting device according to the present embodiment, the preheating time set in the timer circuit 150, the fluorescent lamp 1
Since the eighteen electrodes 118a and 118b are sufficiently preheated and then turned on, blackening near the electrodes due to insufficient preheating and early disconnection of the electrodes can be prevented.

FIG. 2 shows a discharge lamp lighting device according to a second embodiment of the present invention, in which parts corresponding to those in the first embodiment are denoted by reference numeral 100, and description thereof is omitted.

A characteristic of the present embodiment is that a DC power supply is not provided separately as in the first embodiment, but a DC power supply is obtained by rectifying and smoothing an AC current of an AC power supply 210.

That is, in the present embodiment, the timer circuit 250
72, 274, a capacitor 276 having one end connected between the two resistors 272, 274, a constant voltage diode 277 and a resistor 278 connected in series with the capacitor 276, and the accumulated charge in the capacitor 276 increases. As a result, when the terminal voltage increases and reaches the Zener voltage of the constant voltage diode 277, a DC current cutoff signal to the preheating circuit 252 is output.

On the other hand, the preheating circuit 252 includes a secondary winding 228a wound around the ballast choke 228, a diode 280 for rectifying and smoothing a current induced in the secondary winding 228a, and a capacitor 282.

The switch is composed of two transistors 284 and 286 and two resistors 288 and 290.

Then, when the AC power supply 210 is turned on, the inverter circuit 216 starts oscillating similarly to the first embodiment, a voltage is induced in the secondary winding 228a of the ballast choke 228, and the capacitor 282 is immediately charged and Power supply.

Then, the transistor 284 is turned on because the base current is supplied through the resistor 290, and the transistor 284 is turned on.
The current limited by the resistor 288 flows through the secondary winding 230b of the current transformer 230. As a result, the switching transistor
The oscillation frequency of 226 increases, and the electrodes 218a and 218 of the fluorescent lamp 218
b is preheated.

On the other hand, when the AC power supply 210 is turned on, the capacitor 276 constituting the timer circuit 250 is also charged. When the voltage exceeds the Zener voltage of the constant voltage diode 277, the transistor 286 is turned on and the transistor 284 is turned off.

As a result, the secondary winding of the current transformer 230 via the resistor 288
The DC current flowing through 230b is cut off, and the oscillation frequency of switching transistor 226 decreases. Then, the terminal voltage of the starting capacitor 232 increases, and the fluorescent lamp 218 starts lighting.

As described above, according to the discharge lamp lighting device according to the second embodiment, there is no need to provide a separate DC power supply.

FIG. 3 shows a third embodiment of the present invention, in which parts corresponding to those in FIG.

A characteristic of this embodiment is that the DC power is not obtained from the ballast choke 328 but from the secondary winding 320a wound around the oscillation choke 320.

In each of the above embodiments, the AC power supply is rectified by a full-wave rectifier.
Although the example in which the discharge lamp is turned on using the smoothed DC voltage has been described, it is also possible to use a normal DC power supply.

[Effects of the Invention] As described above, according to the discharge lamp lighting device of the present invention, the DC current is supplied to the current transformer for a certain period of time from the time when the power is turned on. It is possible to prevent early blackening near the electrodes, disconnection of the electrodes, and the like.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of a discharge lamp lighting device according to a first embodiment of the present invention, FIG. 2 is a circuit configuration diagram of a discharge lamp lighting device according to a second embodiment of the present invention, and FIG. FIG. 4 is a circuit configuration diagram of a discharge lamp lighting device according to the third embodiment, and FIG. 4 is a circuit configuration diagram of a conventional discharge lamp lighting device. 10,110,210,310… AC power supply 12,112,212,312… Full wave rectifier 16,116,216,316… Inverter circuit 18,118,218,318… Fluorescent lamp (discharge lamp) 24,124,224,324… Parallel resonance circuit 26,126,226,326… Switching transistor (switching element) 28,128,228,328… Ballast choke 30,130,230,330… 32,132,232,332 …… Starting capacitor 150,250,350 …… Timer circuit 152,252,352 …… Preheating circuit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-202494 (JP, A) JP-A-64-77898 (JP, A) JP-A-62-180898 (JP, U) JP-A-62-180898 (JP, U) 96698 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05B 41/24

Claims (3)

(57) [Claims] 1. A rectifier circuit for rectifying an AC power supply from an AC power supply and outputting a DC voltage, a parallel resonance circuit connected to the rectification circuit and comprising a resonance choke and a resonance capacitor, and connected in series to the parallel resonance circuit. A switching circuit, a ballast choke, a discharge lamp, a lighting circuit in which a series circuit of a current transformer is connected to the parallel resonance circuit, and a starting capacitor is connected to a non-power supply side of the discharge lamp. In a discharge lamp lighting device including a single-stone self-excited inverter that drives the switching element by a secondary winding of a current transformer, a timer circuit for setting a desired preheating time from power-on, and the timer circuit is in a preheating period. A DC current is passed through the secondary winding of the current transformer, and when the timer circuit has passed the preheating period, the direct current flowing through the secondary winding of the current transformer is passed. The discharge lamp lighting apparatus comprising: the preheating circuit breaking current, the. 2. The apparatus according to claim 1, wherein said preheating circuit includes a switch linked to a timer circuit, and a DC power supply capable of flowing a DC current to a secondary winding of a current transformer via said switch. And a discharge lamp lighting device. 3. The apparatus according to claim 1, wherein the DC power supply of the preheating circuit is obtained by rectifying and smoothing a voltage generated in a secondary winding wound around an oscillation choke or a ballast choke. Discharge lamp lighting device characterized by the above-mentioned.