JPH02278698A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To prevent overheating with a simple circuit and a simple element by connecting thermostats into driving circuits of power transistors of an inverter circuit. CONSTITUTION:Thermostats 31 are provided in the vicinity of, or coming in contact with the heating parts 19 and 20 of an inverter circuit 8. The thermostats 31 are connected into driving circuits of power transistors 6 and 7 of the inverter circuit 8 for being made an LC resonance circuit and a parallel lighting circuit. Accordingly, when discharge lamps 21 and 22 come to the end of their life and filaments are broken, the circuit of only L is left and voltage to be impressed on the discharge lamps 21 and 22 drops so as to stop discharge for preventing discharge and to prevent generation of an accident such as in case of a linear lighting method, further, in case of not starting at the time of preheating, the thermostats 31 operate to stop oscillation. Thereby, a simple circuit and a simple element can prevent overheating.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a discharge lamp lighting device in which a discharge lamp is lit at high frequency using an inverter circuit, and particularly relates to a discharge lamp lighting device equipped with two discharge lamps. It is something.

BACKGROUND ART In general, a discharge lamp lighting device is configured to use a high frequency inverter circuit in place of a heavy ballast with a coil wound around an iron core, thereby reducing size, weight, and power consumption.

Among discharge lamp lighting devices using inverter circuits, 2
As shown in FIGS. 2 and 3, all of the lamps are of the series lighting type.

First, in the device shown in FIG. 2, a transformer 42 and a power transistor 43 are connected to a power source 41, and a switching control circuit 44 is connected to the power transistor 43. A lamp life detection circuit 45 is connected to this switching control circuit 44 . The transformer 42 also includes two discharge lamps/16 connected in series.
is connected. A capacitor 47 is connected in parallel to one discharge lamp 46.

Next, the one shown in FIG. 3 is equipped with a pair of power transistors 43, and two discharge lamps 46 connected in series with each other via a choke coil 48 are connected to a capacitor at the output terminal of a transformer 42. Connected via 49.50. A capacitor 47 is connected in parallel to one discharge lamp 46, and both discharge lamps 46
A capacitor 51 is connected to. Further, the choke coil 48 is provided with a detection winding 52 , a lamp life detection circuit 45 is connected to the detection winding 52 , and the lamp life detection circuit 45 is connected to the base circuit of one of the power transistors 43 . has been done.

Problems to be Solved by the Invention In such a series-type discharge lamp lighting device, when the active material in one part of the lamp cathode is exhausted at the end of the lamp life, current flows only through the other electrode, resulting in a rectified state. Become. For this reason, a direct current component is included in the discharge current, magnetic saturation occurs in the transformer or choke coil, the inductance value decreases, and the current increases.

Furthermore, even if the filament is broken, the voltage remains, so the spot gradually moves along the stem of the electrode, and when it reaches the holding part formed of glass, the stem breaks and falls, and in rare cases, the spot may break and fall. Cracks may appear in the parts, causing accidents where the discharge lamp falls.

Further, even if the device does not start up for some reason during preheating, the same phenomenon as described above occurs.

In order to prevent such adverse effects, as shown in FIG. 23, a detection winding 52 is attached to the choke coil 48, and a circuit is installed to feed back the voltage induced in the detection winding 52 to the oscillation circuit. It becomes necessary. Therefore, there are problems in that the circuit configuration becomes complicated and the price increases.

Means for Solving the Problem An inverter circuit that is connected to a DC power supply and a starting circuit and outputs a high frequency through semiconductor switching operation is provided, and two discharge lamps that resonate in LC series are connected in parallel to the output terminal of this inverter circuit. A thermostat was provided in proximity to or in contact with a heat generating component of the inverter circuit, and the thermostat was connected in a drive circuit for a power transistor of the inverter circuit.

By creating an LC series resonance and parallel lighting circuit, when the discharge lamp reaches the end of its life or the filament is broken, the circuit becomes L only, and the voltage applied to the discharge lamp decreases and the discharge stops. This prevents the above-mentioned accident from occurring.Furthermore, if the thermostat does not start during preheating, the thermostat operates and stops oscillation, which allows simple circuits and elements to This can prevent overheating.

Example An embodiment of the present invention will be described based on FIG.

First, a commercial power supply 1 is connected to a diode bridge circuit 3 through a filter circuit 2 for surge absorption and noise prevention. and smoothing capacitor 4. A rectifier circuit 5 as a DC power source made of (Co) is connected.

This rectifier circuit 5 includes 5EPP (
An inverter circuit 8 comprising a pair of power transistors 6.7 (Q□, Q2) connected (single-ended push-pull) is connected. The inverter circuit 8 is a self-excited series inverter of a saturable current transformer type, and the drive transformer 9 (T,) is a saturable current transformer, which has one primary winding W11 and two counter-wound secondary windings. It has lines W 2a and W 2b. The secondary winding W l 1 is inserted in series with the output J terminal of the inverter circuit 8, detects the load current flowing therein, and applies the corresponding secondary voltages of mutually opposite phases to each secondary winding. W 2
a and W2b, and these elements form a drive circuit for the power transistor 6.7. The secondary winding W2a is then connected to the base of the power l-transistor through a resistor 10(R,a). Further, connected to the base of the power transistor 6 are a transistor denoted Q3] and a diode 12 denoted D3. Further, the transistor 11 and the diode 12 are connected to a resistor 13 (Rb,) connected to the base of the transistor 11 and an emitter resistor 14 (Rr, :,) connected to the transistor 11 to light up the discharge lamp. It is a feedback circuit that sets the required lamp secondary voltage. Furthermore, the other secondary winding W2b is also connected to the base of the power transistor 7 via a resistor].circle (R2b), similarly to the secondary winding W2a. Further, a transistor 1.5 (Q, ) and a diode 16 (], ), ) are connected to the base of the power transistor 7. Furthermore, the transistor 15 and the diode]6 are connected to a resistor 17 (Rb2) connected to the base of the transistor 15 and an emitter resistor 18 (Rr:2) connected to the transistor 15, so that when the discharge lamp is lit, It is a feedback circuit that sets the required lamp secondary voltage.

Next, a choke coil 19 is connected to the output terminal of the inverter circuit 8. Discharge lamps 21...22 (F,,F,) are connected between the negative side DC horn terminal of the rectifier circuit 5 via CJ(,,CA-1,). , capacitors 23.24 (C4, , C42) are dividing capacitors, and capacitor 2 labeled C,3,cm
5. ．． 26 is the discharge lamp 21. ．． This is for starting 22.

In addition, a series circuit is connected to the negative side DC terminal via a resistor 27 (R,) and a capacitor 28 (C,) connected between the positive side DC inflow terminal J and the output terminal of the inverter circuit 8. A starting circuit for the inverter circuit 8 is activated by a relaxation oscillation circuit constituted by a bidirectional thyristor 29 (SS) connected in series from a contact point between the resistor 27 and the capacitor 28 to the base of one of the power transistors 7. 30 is formed.

In the discharge lamp lighting position of this embodiment, the 5 operating temperature is L.
], a thermostat 3] of about 0 degrees is connected between the primary winding W1 and the secondary windings W, a of the drive transformer 9. A print formed by a board! 'ji! The thermostat 3 is provided on a wire board, and the thermostat 3 is placed between choke coils 19 and 20, which are heat generating components.

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 27 to a capacitor 28.
Charge is accumulated in the As a result, when the potential of the connection between the resistor 27 and the capacitor 28 (%j) rises, and this exceeds the breakdown voltage of the bidirectional cylindrical IJ star 29, the two bidirectional cylindrical conductors become conductive and one side A base current is supplied to the power transistor W of the drive transformer 9, and the power transistor 7 becomes conductive.The current flowing through the power transistor 7 is the primary winding W of the drive transformer 9,
1. Choke coil 1.9, 20. It flows through the filament of the discharge lamp 21.22 and the starting capacitor 25.2f3, and is positively fed back to the base of the power transistor 7 via the secondary winding w2b. While the power transistor 7 is in a conductive state, the current flowing through the -order winding Wl+ increases with time, and the magnetic flux density in the core of the drive transformer 9 increases, eventually reaching saturation. Then, the secondary winding w
, 11 becomes zero, and the power transistor 7
is turned off. Therefore, when the current flowing through the negative secondary winding W11, that is, the magnetomotive force applied to the core of the drive transformer 9, decreases below a level that saturates the core, a positive voltage is induced in the secondary winding W2a. Power transistor 6 turns on. This on state continues until the drive transformer 9 is saturated due to positive feedback via the negative winding W1 and the secondary winding W2a. From then on,
Similarly, power transistors 6.7 are turned on alternately, and inverter circuit 8 continues to oscillate.

When the discharge lamps 21, 22 reach the end of their lifespan or the filament breaks, the circuit becomes an L-only circuit, and the voltage applied to the discharge lamps 21, 22 decreases to stop the discharge. Therefore, accidents caused by the rectifying action of the series lighting type as shown in FIGS. 2 and 3 will not occur.

On the other hand, due to reasons such as low ambient temperature, the discharge lamp 21.2
2 does not light up, a preheating current that is more than double the amount normally applied is applied to the choke coil J9.20, the power transistor 6.7, etc., and these parts generate heat. Then, this heat is rapidly conducted to the thermostat 31 by the printed wiring board 32. Therefore, this thermostat 31 interrupts the conduction between the primary winding W I + and the secondary winding W 2a of the drive transformer 9 to stop the oscillation of the inverter circuit 8. It goes without saying that when the temperature of the choke coils 19, 20, etc. decreases, the thermostat 3 restores conduction to the drive transformer 9 and the inverter circuit 8 operates again.

Effects of the Invention The present invention provides an inverter circuit that is connected to a DC power source and a starting circuit and outputs a high frequency signal through a semiconductor switching operation, and connects two LC series-resonant radiators to the output terminal of the inverter circuit. Electric lights are connected in parallel, a thermostat is provided in close proximity to or in contact with the heat generating components of the inverter circuit, and the thermostat is connected in the drive circuit of the power transistor of the inverter circuit, resulting in an LC resonant, parallel lighting circuit. As a result, when the discharge lamp reaches the end of its life or the filament breaks, the circuit becomes an L-only circuit, the voltage applied to the discharge lamp decreases, and the discharge can be stopped. This prevents accidents like those that occur with the series lighting system,
Furthermore, if the device does not start up during preheating, the thermostat operates to stop oscillation, which has the effect that overheating can be prevented with simple circuits and elements.

8. Inverter circuit, 21. ．． 22・Discharge illusion, Ko30
・Start circuit, 31 ・Thermostat application Tokyo Electric Co., Ltd.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, FIG. 2 is a circuit diagram showing a conventional example, and FIG. 3 is a circuit diagram showing another conventional example.

Claims (1)

[Claims] An inverter circuit is provided which is connected to a DC power supply and a starting circuit and outputs a high frequency through semiconductor switching operation, and two discharge lamps having LC series resonance are connected in parallel to the output terminal of this inverter circuit, and heat generating components of the inverter circuit are connected to the output terminal of the inverter circuit. A discharge lamp lighting device characterized in that a thermostat is provided near or in contact with the inverter circuit, and the thermostat is connected in a drive circuit for a power transistor of the inverter circuit.