JPH06267686A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To surely and easily control the output of a discharge lamp. CONSTITUTION:The device is equipped with a self exciting type inverter circuit which makes a DC power supply 1 input, also makes a resonance circuit load, which is made up of a choke coil 7, a capacitor 6, and of a discharge lamp 5, a capacitor 16 is rested in a closed circuit including a switching element 3 and a feedback winding n3 for the self exciting type inverter circuit, and a variable resistor 17 which changes and controls the output of the discharge lamp 5, is connected to the capacitor 16 in parallel. When the value of the variable resistor 17 is changed, the base control condition of the switching element (transistor) 3 is changed, the oscillating frequency of the self exciting type inverter circuit is accordingly changed, so that current to the discharge lamp 5 is thereby changed.

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 provided with a self-excited inverter circuit which receives a direct current power supply and uses a resonance circuit composed of a choke coil, a capacitor and a discharge lamp as a load. In particular, a parallel circuit of a capacitor and a variable resistor R is connected in series with the feedback winding in the self-excited inverter circuit, and the variable resistance value is changed to easily control the discharge lamp output.

[0002]

2. Description of the Related Art In a conventional apparatus, as shown in FIG. 3, a sub-switching element 20 is connected in parallel to a base / emitter of a main switching element 3, and the sub-switching element 20 is turned on / off to turn on / off a discharge lamp 6. Control output.

[0003]

The above-mentioned conventional device is disadvantageous in that the control of the sub-switching element 20 is complicated and the device is downsized. The present invention aims to control discharge lamp output more simply and easily.

[0004]

To achieve the above object, a capacitor is inserted in a closed circuit including a switching element and a feedback winding in a self-excited inverter circuit, and a capacitor for controlling discharge lamp output is provided in parallel with the capacitor. Connect a variable resistor.

[0005]

As shown in FIG. 1, for example, the switching element Q ₂
A parallel circuit of a capacitor 16 and a variable resistor 17 is connected to the base portion on the third side, and the variable resistor 17 changes the base current I _B. As a result, the ON period of the switching element Q ₂ changes, and t _on (Q ₁ )> t _on (Q ₂ ) and the oscillation frequency changes. Thereby, the output of the discharge lamp 6 can be controlled.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. This lighting device includes a self-excited inverter circuit that receives a DC power supply 1 as an input and a transistor 2 that is a switching element.
.3, the diodes 20 and 21, the drive transformer 8 which is a current transformer, and the capacitors 4 and 10. The load of the self-excited inverter circuit is composed of a resonance circuit including a choke coil 7, a capacitor 6 and a discharge lamp 5.
The primary winding n ₁ of the drive transformer 8 is inserted in series with the load 5, 6, 7, in the current flowing through the resonant circuit as a load 5, 6, 7, of different polarity the secondary winding n ₂ , N ₃ is fed back to the bases of the transistors 2 and ₃ to induce a voltage,
The transistors 2 and 3 are switched alternately. In addition,
The circuit composed of the resistor 9, the capacitor 10 and the voltage sensitive element 11 is a starting circuit, which starts the conduction operation of the transistors 2 and 3 when the DC power supply 1 is turned on. Here, the capacitor 16 connected in series with the secondary winding n ₃ of the drive transformer
The variable resistors 17 are control circuits unique to the present invention, which are parallel to each other. The resistors 14 and 15 are for controlling the base current of the transistors 2 and 3. First of all, capacitors 16 and 1
The case where there is no 7 will be described. Note that it is assumed that the relationship is n ₂ = n ₃ R ₁₄ = R ₁₅ (the resistance values of the resistors 14 and 15 are equal). When the DC power supply 1 is turned on, the capacitor 10 is charged via the resistor 9. Then, when the voltage of the capacitor 10 reaches the breakover voltage of the voltage sensitive element 11, the capacitor 10 is discharged through the base-emitter of the transistor 3. As a result, the transistor 3 becomes conductive. Therefore, a current flows through the DC power supply 1 → capacitor 4 → figment of the discharge lamp 5 → capacitor 6 → filament of the discharge lamp 5 → choke coil 7 → n _{1 of the} drive transformer 8 → transistor 2 → DC power supply 1 and the capacitor 4 To charge. Since this current flows through n _{1 of the} drive transformer 8, 2
A voltage is induced in each of the secondary windings n ₂ and n ₃ . Secondary winding n
Induced voltage of ₃ has a polarity which maintains the conductive state of the transistor 3. After that, the current that tries to charge the capacitor 4 increases, but the current gradually decreases as the charging progresses, and when the current approaches zero, the feedback voltage from the drive transformer 8 is applied to the transistor 2 as a forward voltage. A reverse voltage is applied to the transistor 3, the transistor 3 is turned off, and the transistor 2 is turned on. Therefore, the load circuit,
And be closed circuit n ₁ and transistor 2 of drive transformer 8, the capacitor 4 starts to discharge. By repeating the charging and discharging of the capacitor such that the transistor 2 is turned off and the transistor 3 is turned on by the vibration caused by this capacitor discharge, the both transistors 2 and 3 are alternately turned on and off to cause a current to flow to the load, The voltage of the capacitor 6 is applied to the discharge lamp 5 to light the discharge lamp 5. The waveform of each part at this time is shown in FIG. In this case, the transistor (Q ₁ ) 2 and the transistor 3 are
The ON periods of (Q ₂ ) 3 are almost equal. next,
A case where the capacitor 16 and the variable resistor 17 are connected will be described. In this case, the variable resistor 17 causes the transistor 3
The base current of is reduced compared to when the capacitor 16 and the resistor 17 are not provided. Therefore, the collector current of the transistor 3 (that is, the charging current of the capacitor 4) is reduced, the charging period of the capacitor 4 is shortened, and the discharging of the capacitor 16 accelerates the turning off of the transistor 3. That is, of the transistors 2 and 3, the conduction time of the transistor 3 is shortened and the oscillation frequency is increased. The waveform of each part at this time is shown in FIG. Therefore,
Since the variable resistor 17 can arbitrarily control the base current of the transistor 3, the conduction time of the transistor 3 can be varied, so that the oscillation frequency can be changed and the output of the discharge lamp 5 can be controlled. FIG. 2 shows another embodiment. The switch 19 is connected in parallel with the capacitor 16 to change the output in two stages. That is, when the switch 19 is on, all light is emitted, and when the switch 19 is off, dimming is performed. The resistor 18 and the switch 19 in FIG. 2 function as a kind of variable resistor. Although the parallel circuit of the capacitor and the variable resistor is connected to only one of the two transistors in the above embodiment, the same parallel circuit may be connected to both of the two transistors.

[0007]

According to the present invention, the output of the discharge lamp can be controlled by adding simple elements such as a capacitor and a variable resistor,
Further, by continuously changing the variable resistance value, continuous dimming becomes possible.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a device of the present invention.

FIG. 2 is a circuit diagram showing another embodiment.

FIG. 3 is a circuit diagram of a conventional device.

FIG. 4 is an operation explanatory diagram with and without a capacitor 16 and a variable resistor 17 in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... DC power supply, 2/3 ... switching element, 4 ... capacitor, 5 ... discharge lamp, 6 ... resonance capacitor, 7 ... resonance choke coil, 8 ... drive transformer, 16 ... control capacitor, 17 ... base current Variable resistor for control

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[Procedure amendment]

[Submission date] May 14, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

[Figure 3]

[Figure 4]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H05B 41/29 Z 9249-3K

Claims (1)

[Claims] 1. A self-excited inverter circuit having a DC power supply as an input and a resonance circuit composed of a choke coil, a capacitor, and a discharge lamp as a load, and a closed circuit of a switching element and a feedback winding in the self-excited inverter circuit. A discharge lamp lighting device, wherein a capacitor is inserted in the capacitor, and a variable resistor for controlling the discharge lamp output is connected in parallel with the capacitor.