JPH02132797A - Electric discharge lamp lighting circuits - Google Patents

Abstract

PURPOSE:To attempt the improvement of durability, reliability, stability and facilitation, relative to the lighting circuits in the title, by controlling a switching element in accordance with voltage in a feedback winding through a control circuit, and then keeping the output of a self-excited type inverter circuit constant and at the same time making a light adjustment through a light adjuster circuit. CONSTITUTION:When voltage in a feedback winding 11 ries with the large output of a self-excited type inverter circuit 3, a control circuit 21 controls a transistor 5 to lower the output of the self-excited type inverter circuit 3. When voltage in the feedback winding 11 also falls with the small output of the self-excited type inverter circuit 3, the control circuit 21 controls the transistor 5 to heighten the output of the self-excited inverter circuit 3. When a light adjuster circuit 20 is opened, then the self-excited inverter circuit 3 gives the entire light output thereof for putting the entire light to an electric discharge lamp 16. When the light adjuster circuit 20 is closed, part of the base current flowing through the transistor 5 is bypassed to lower the output of the transistor 5, with lowering the output of the self-excited type inverter circuit 3 to put a dimmed light to the electric discharge lamp 16. This makes it possible to attempt the improvement of durability, reliability, stability and facilitation, relative to the lighting circuits in the title.

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECTS OF THE INVENTION (Industrial Field of Application) The present invention relates to a lighting circuit for a discharge lamp, such as a fluorescent lamp, having a self-help inverter circuit.

(Prior art) As a conventional discharge lamp lighting circuit of this type, for example, a second
The circuit shown in the figure is known.

In Fig. 2, 1 is a commercial AC power supply, and to this commercial AC power supply 1, the input terminal of a DC conversion circuit 2 that rectifies and smoothes the commercial AC is connected, and the output terminal 10 of this DC conversion circuit 2 is an automatic type. It is connected to the inverter circuit 3. This self-excited inverter circuit 3 connects the positive output terminal of the DC conversion circuit 2 to the capacitor 4 and the collector of the NPN transistor.
It is connected to the negative output terminal of the DC conversion circuit 2 via the emitter. Further, a bias resistor 6 connected to the positive output terminal of the direct current converting circuit 2 is connected to the base of the transistor 5. The capacitor 4 is connected to the primary winding 8 of a step-up transformer 7. This transformer 7 has a step-up winding 1rA9 in addition to the primary winding 8. Further, the feedback transformer 10 includes a feedback winding 11 and a current limiting winding 1.
It has 2. One end of the feedback winding 11 is connected to the base of the transistor 5 via the coupling capacitor 12, and the other end is connected to the negative output terminal of the DC conversion circuit 2.

Furthermore, one end of the current-limiting winding 1a12 is connected to one end of the boost winding 9, and the other end of the boost winding 9 and the other end of the current-limiting winding 12 are connected to a filament 17 of a discharge lamp 16 made of, for example, a fluorescent lamp. 18 respectively connected to one end of filament 17. The other ends of 18 are connected to starting capacitors 19, respectively.

Then, the commercial AC from the commercial AC power supply 1 is rectified and smoothed by the DC converting circuit 2 to become DC. This direct current is charged in the capacitor 4, oscillated by the capacitor 4 and the primary winding 8, etc., and a positive voltage is applied to the collector of the transistor 5. For example, a base current is supplied to the transistor 5 via the bias resistor 6. By doing so, transistor 5
is turned on. In this way, capacitor 4 and primary I
As the transistor 5 repeats on and off according to the oscillation of Im8, etc., the voltage 8! is applied to the pressure winding 9. A voltage is induced. At this time, the period and base current of the transistor 5 are set according to the voltage induced in the feedback winding 111 of the transformer 10 from the current limiting winding 12 side.

Then, the discharge lamp 16 is turned on.

(Problems to be Solved by the Invention) However, the conventional discharge lamp circuit shown in FIG.
It has a dimming function, and the output fluctuates due to input fluctuations, environmental fluctuations such as temperature, and changes in the parts used.

Furthermore, in order to guarantee the starting voltage based on the low temperature of about 0℃, when it is difficult to light the discharge lamp, at high temperatures of 50℃ to 60℃, the heat generation of each element increases, and the output of the automatic inverter circuit 3 increases. This causes a problem in that the brightness of the discharge lamp 1G changes, resulting in a lack of durability, reliability, and stability.

The present invention was made in view of the above problems, and an object of the present invention is to provide a discharge lamp lighting circuit that is durable, reliable, and stable.

[Structure of the invention]

(Means for Solving the Problems) The discharge lamp lighting circuit of the present invention includes a self-help inverter circuit that controls a switching element using the output of a feedback winding, and a control that controls the switching element according to the voltage of the feedback winding. The control circuit includes a dimming circuit for avoiding changing the set output of the self-help inverter circuit.

(Function) The present invention operates the switching element at tI1 using the output of the feedback winding.
11III1 to control the output of the automatic inverter circuit. Further, the control circuit controls the output controlled by the switching element according to the voltage of the feedback winding, and changes the output of the self-help inverter circuit using the dimming circuit.

(Embodiment) Hereinafter, an embodiment of the discharge lamp lighting circuit of the present invention will be described with reference to FIG. Note that parts corresponding to those of the conventional discharge lamp lighting circuit shown in FIG. 1 are denoted by the same reference numerals, and a description thereof will be omitted.

The discharge lamp lighting circuit shown in FIG. 1 is obtained by connecting a control circuit 21 having a dimming circuit 20 to the discharge lamp lighting circuit shown in FIG. In this control circuit 21, the anode of a shunt diode 22 is connected to the connection point between the base of the transistor 5, the resistor 6, and the capacitor 12.
The cathode of the transistor 23 is connected to the collector of the transistor 23, and is connected to the negative output terminal of the DC conversion circuit 2 via the base resistor 24 of the transistor 23, and a resistor is connected between the base and the emitter of the transistor 23. 25 are connected.

Roughly speaking, a capacitor 26 is connected between the emitter of the transistor 23 and the negative output terminal of the DC conversion circuit 2, and a diode 27 is connected between the emitter and the connection point between the feedback winding 11 and the capacitor 12. .

A resistor 2 connected in series is used as a dimming circuit 20.
8 and a switch 29 are connected in parallel with the transistor 23, that is, between the collector and emitter of the transistor 23.

Next, the operation of the above embodiment will be explained. The basic operation is similar to the discharge lamp lighting circuit shown in FIG. The control circuit 21 changes the base current of the transistor 5 according to the voltage of the feedback winding 11 to control the output of the automatic inverter circuit 3.

First, the voltage induced in the feedback winding 11 is shunted to the transistor 23 via the shunting diode 22 in accordance with the return winding. If the output of the automatic inverter circuit 3 is small, for example under operating environments such as low temperatures or reduced input voltage, the feedback winding 1
1 decreases, and the impedance between the emitter and collector of transistor 23 increases. As a result, the base current bypassed to transistor 23 decreases, the base current of transistor 5 increases, and transistor 5
Due to the increase in the output of the self-help inverter circuit 3, the output of the self-help inverter circuit 3 increases.

On the other hand, in environments where the automatic inverter circuit has a large output, such as high temperatures and increased input voltage, the feedback winding 11
voltage increases, and the impedance between the emitter and collector of the transistor 23 decreases. As a result, the base current bypassed to the transistor 23 increases, and the output of the transistor 5 decreases, causing the self-help inverter circuit 3 to
output decreases.

When the switch 29 is opened, the self-excited inverter circuit 3 outputs a bright light, and the discharge lamp 16 is turned on at full brightness.

When the switch 29 is closed, a part of the base current flowing through the transistor 5 is bypassed by the resistor 28, and the output of the transistor 5 decreases, and the output of the self-help inverter circuit 3 decreases, so the discharge lamp 16 is dimmed. Light.

Further, the switch 29 is not limited to a mechanical switch, and a switching element such as a transistor or a thyristor may be used.
Multiple circuits may be connected in parallel.

According to the above embodiment, when the output of the automatic inverter circuit 3 exceeds the voltage of the feedback winding 11, the control circuit 21 controls the transistor 5 to reduce the output of the automatic inverter circuit 3. When the voltage of the feedback winding 11 is low and the output of the self-help inverter circuit 3 is small, the control circuit controls the transistor 5 to increase the output of the automatic inverter circuit 3, so the output of the self-help inverter circuit 3 is stabilized and the elements It is possible to prevent the heat generation etc. of the discharge lamp 16.
The brightness becomes stable.

〔Effect of the invention〕

According to the present invention, since the control circuit controls the switching element according to the voltage of the feedback winding and keeps the output of the self-commutated inverter circuit constant, the sag of the M lamp is also constant, improving durability, reliability, and stability. It is convenient because the light can be adjusted using a dimming circuit.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing an embodiment of the discharge lamp lighting circuit of the present invention, and FIG. 2 is a circuit diagram showing a conventional example. 3. Self-help inverter circuit, 5. Transistor as a switching element, 11. Feedback winding, 20. Light control circuit, 21. Control circuit.

Claims (1)

[Claims] (1) A self-excited inverter circuit that controls a switching element using the output of a feedback winding is provided with a control circuit that controls the switching element according to the voltage of the feedback winding, and this control circuit sets the self-excited inverter circuit. A discharge lamp lighting circuit characterized by having a dimming circuit that changes output.