JPH02215092A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To keep the light output of a discharge lamp constant even if the temperature of a saturable current transformer and stabilize the performance of a discharge lamp lighting device by connecting a temperature correcting circuit arranged with heat sensitive elements nearby on the saturable current transformer of an inverter circuit to luminous sections of photo-couplers. CONSTITUTION:When the temperature of a saturable current transformer 9 rises, the voltage value applied to a thermistor 31 is increased, the output voltage of a detection voltage reversing circuit 36 is decreased, currents inputted to luminous sections 42 and 43 of photo-couplers 40 and 41 are decreased, and base currents of transistors 11 and 15 are decreased. Base currents of transistors 6 and 7 are increased, the oscillation of an inverter circuit 8 is amplified, and the light output of a discharge lamp 20 is kept at a nearly constant value and stable because its decrease by the temperature characteristic of the saturable current transformer 9 is compensated. The light output of the discharge lamp is stabilized accordingly.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a discharge lamp lighting device adapted for wave lighting.

Conventional technology Generally, a pair of power switching transistors (main transistors) are used as a lighting device for discharge lamps such as fluorescent lamps.
A half-bridge type series inverter circuit is known.

Furthermore, a self-commutated type is known in which the output current of such a series inverter circuit is detected by a transformer and fed back to the base from the secondary winding of the transformer, thereby turning the transistors on and off alternately. . In such a lighting device, a discharge lamp as a load is connected to the output terminal of an inverter circuit via a current-limiting inductance.
In addition, a discharge lamp starting capacitor is connected in parallel with the discharge lamp. This example will be explained based on FIGS. 3 and 4.

The present invention first uses an inverter circuit to convert a discharge lamp into a high-rise DC power supply consisting of a commercial type [TL, a diode bridge circuit 3, a smoothing capacitor 4 (C, )] via a filter circuit 2 for surge absorption and noise prevention. A rectifier circuit 5 is connected.

This rectifier circuit 5 includes a pair of switching transistors 6.7 (Q,

An inverter circuit 8 with a Q, ) is connected.

This inverter circuit 8 is a self-excited series inverter of a saturable current transformer type, and the saturable current transformer 9
(T,) is one primary winding W1. and two mutually oppositely wound secondary windings W, a, W, b.

The second winding W1. is inserted in series with the output terminal of the inverter circuit 8, and the load current a'? flows therein. l
t LLI, and corresponding secondary voltages having opposite phases to each other are generated in each secondary winding W, a, W, b, and these elements are used to generate switching transistors 6, 6, and 6.
7 drive circuits are formed. The secondary winding W, a is then connected to the base of the switching transistor 6 via a resistor 10 (R, a). moreover,
A transistor l 1 (Q,) and a diode 12 (D,) are connected to the base of the switching transistor 6. Further, the transistor 11 and the diode 12 are connected to the base of the transistor 11 with a resistor 13 (Rb,) and the transistor 11 with an emitter resistor 14 (R, , ) connected to the transistor 11 and the diode 12, so that when the discharge lamp is lit, It is a feedback circuit that sets the required lamp secondary voltage. Furthermore, the other secondary winding Wsb is also connected to the base of the switching transistor 7 via a resistor 10 (R, b), similarly to the secondary windings W, a. Furthermore, a transistor 15 (Q,) and a diode 16 (D) are connected to the base of the switching transistor 7.
, ) are connected. Also, this transistor 15
and the diode 16, which is connected to the base of the transistor 15 and the emitter resistor 18 (R*,), which are connected to the base of the transistor 15 and the emitter resistor 18 (R*,). It is a feedback circuit that sets the voltage.

Next, the output terminal of the inverter circuit 8 is connected to the primary winding W of the saturable current transformer 9, and a ballast inductor 19 (L,
, ), a discharge lamp 20 (F) is connected in an alternating current manner to the negative side DC output terminal of the rectifier circuit 5. Here, the capacitors 21 and 22 (C4, , C, .) are dividing capacitors, and the capacitor 23 (Go) is for starting the discharge lamp 20.

Further, a series circuit connected between the positive side DC input terminal and the output terminal of the inverter circuit 8 and reaching the negative side DC terminal via a resistor 24 (R,) and a capacitor 25 (C,) in order; The inverter circuit 8 is activated by a relaxation oscillator circuit composed of a bidirectional thyristor 26 (SS) connected in series from the contact point of the resistor 24 and the capacitor 25 to the base of one of the switching transistors 7.
A starting circuit 27 is formed.

In such a configuration, when commercial power is turned on,
This AC output is rectified by a rectifier circuit 5, and the DC is supplied to an inverter circuit 8, and is passed through a resistor 24 to a capacitor 25.
Charge is accumulated in the As a result, the potential at the connection point between the resistor 24 and the capacitor 25 rises, and when this exceeds the breakdown voltage of the bidirectional thyristor 26, the bidirectional thyristor 26 becomes conductive and the base current flows into the switching transistor 7 on one side. is supplied, and the switching transistor 7 becomes conductive. The current flowing through this switching transistor 7 flows through the primary winding W l 1 of the saturable current transformer 9, the ballast inductor 19, the filament of the discharge lamp 20, and the starting capacitor 23, and this flows through the secondary windings W, b. It is positively fed back to the base of the switching transistor 7 via. While this switching transistor is in a conductive state, the current flowing through the -order winding W1 increases with time, and the saturable current transformer 9
The magnetic flux density in the core increases and finally reaches saturation.

Then, the induced voltage in the secondary windings W and b becomes zero, and the switching transistor 7 is turned off. Therefore, -th winding W
1. When the current flowing through the current transformer 9, that is, the magnetomotive force applied to the core of the saturable current transformer 9, decreases and becomes smaller than the level that saturates the core, a positive voltage is induced in the secondary windings W and a, and the switching transistor 6 turns on. This on state is the negative winding W3. and secondary winding W
, a until the saturable current transformer 9 is saturated due to positive feedback. Thereafter, similarly, switching transistors 6.7 are alternately turned on, and inverter circuit 8 continues to oscillate.

Problems to be Solved by the Invention In the discharge lamp lighting device as described above, as illustrated in FIG. 4, when the temperature of the saturable current transformer 9 rises due to changes in the atmosphere or self-heating, its temperature characteristics change. Therefore, the current input to the discharge lamp 20 decreases, and its light output decreases. That is, as shown in the B-H curve (magnetic field-current characteristics) of the transformer 9, when the temperature of the transformer 9 increases, the magnetic flux quickly shifts to saturation, and the saturation magnetic flux density decreases. Therefore, the oscillation frequency of the inverter circuit 8 increases, and the impedance of the inductor I9 increases. Then,
Since the current input to the discharge lamp 20 decreases, the light output of the discharge lamp 20 decreases.

For this reason, the performance of the discharge lamp lighting device is unstable.

Means for Solving the Problem An inverter circuit is provided which is connected to a DC power source and a starting circuit and outputs a high frequency through semiconductor switching operation.A discharge lamp is connected to the output terminal of this inverter circuit via an inductance element. A light receiving section of the photocoupler is connected in parallel to the main transistor drive circuit, and a temperature correction circuit in which a heat sensitive element is placed close to the saturable current transformer of the inverter circuit is connected to the light emitting section of the photocoupler.

The photocoupler's light receiving section is connected in parallel to the main transistor drive circuit of the inverter circuit, and a temperature compensation circuit with a heat-sensitive element placed close to the inverter circuit's saturable current transformer is connected to the photocoupler's light emitting section. Even if the temperature of the saturable current transformer changes due to changes in temperature or self-heating, the drive of the main transistor of the inverter circuit remains constant and the current input to the discharge lamp is uniform.

Embodiment An embodiment of the present invention will be explained based on FIGS. 1 and 2. Note that the same parts as those described in FIG. 3 are designated by the same reference numerals, and the description thereof will be omitted. This discharge lamp lighting device 28
In this case, a power supply winding 29 is wound around the ballast inductor 19, and a "temperature correction circuit 3" is connected to this power supply winding 29.
0 is connected. As the heat-sensitive element of the temperature correction circuit 30, a thermistor, a carbon resistor, or the like whose resistance value increases as the temperature rises can be used. Therefore, in this temperature correction circuit 30, for example, the thermistor 31 (RT□)
transistor 32 (Q,) and resistors 33 to 35 (RA
t Rc * Rゎ) Detection voltage inversion circuit 36
is connected. Furthermore, this detection voltage inversion circuit 36
An output voltage circuit 39 consisting of a transistor 37 and a resistor 38 (RE, ) is connected to the transistor 37 of the output voltage circuit 39, and photocouplers 40, 41
The light emitting units 42 and 43 of (PQ,,PQ,) are connected. Also, the light receiving section 44. of the photocoupler 40.41.
45 is connected together with a diode 46.47 between the secondary winding W, a, W, b of said saturable current transformer 9 and the base of said transistor 11.15. In addition,
The thermistor 31 of the temperature correction circuit 30 is placed close to the saturable current transformer 9.

In such a configuration, the discharge lamp lighting device 28 functions similarly to the discharge lamp lighting device illustrated in FIG. 3.

In this discharge lamp lighting device 28, when the temperature of the saturable current transformer 9 rises, the resistance value of the thermistor 31 increases, and the voltage value of the current applied thereto increases.

Then, the output voltage of the detection voltage inversion circuit 36 decreases and the base current of the transistor 37 decreases, so the current input to the light emitting sections 42 and 43 of the photocouplers 40 and 41 decreases. Therefore, when the light output of the light emitting sections 42.43 decreases and the amount of light received by the light receiving sections 44.45 decreases, the output current thereof decreases, and the base current of the transistor 11.15 decreases. Then, the shunt component of the base current of transistor 6.7 that was flowing through transistor 11.15 decreases, and the base current of transistor 6.7 increases by that amount. Therefore, the oscillation of the inverter circuit 8 is amplified, and the optical output of the discharge lamp 20 is stably maintained at a substantially constant value by compensating for the decrease due to the temperature characteristics of the saturable current transformer 9.

Furthermore, when the temperature of the saturable current transformer 9 decreases, an effect almost opposite to the temperature increase process described above occurs. There are also things that are not.

By controlling the current input to the discharge lamp 20 according to the temperature change of the saturable current transformer 9 as described above,
As illustrated in Figure 2, this current becomes approximately equal,
The light output of the discharge lamp 20 is stable.

Effects of the Invention As described above, the present invention connects the light receiving section of a photocoupler in parallel to the main transistor drive circuit of an inverter circuit, and uses a temperature correction circuit in which a heat sensitive element is placed close to the saturable current transformer of the inverter circuit as a photocoupler. By connecting to the light emitting part of the discharge lamp, even if the temperature of the saturable current transformer changes due to changes in the atmosphere or self-heating, the drive of the main transistor of the inverter circuit remains constant and the current input to the discharge lamp is approximately equalized. - Therefore, the light output of the discharge lamp is constant and the performance of the discharge lamp lighting device is stable.

45... Light receiving section

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is an explanatory diagram of temperature characteristics of a saturable current transformer, Fig. 3 is a circuit diagram of a conventional example, and Fig. 4 is a temperature characteristic of a saturable current transformer. FIG. 5... DC power supply, 6.7... Main transistor, 8.
...Inverter circuit, 9...Saturable current transformer, 2
0... Discharge lamp, 27... Starting circuit, 28... Discharge lamp lighting device, 30... Temperature correction circuit, 31... Heat sensitive element, 40° 41... Photo coupler, 42.43・・・
・Light emitting part, 44° - Figure 2 (cut out)

Claims (1)

[Claims] an inverter circuit that is connected to a DC power supply and a starting circuit and outputs a high frequency through semiconductor switching operation; a discharge lamp that is connected to the output terminal of the inverter circuit via an inductance element; and a main transistor drive circuit of the inverter circuit that receives light. A discharge lamp lighting device comprising: a photocoupler having portions connected in parallel; and a temperature correction circuit connected to the light emitting portion of the photocoupler and having a heat sensitive element disposed close to a saturable current transformer of the inverter circuit. .