JPS6129097A - Device for firing discharge lamp - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a discharge lamp lighting device, and an object thereof is to reduce circuit loss and improve efficiency in such a device.

BACKGROUND OF THE INVENTION Conventionally, a discharge lamp lighting device having a configuration as shown in FIG. 8 has been used. In the figure, l is a rectifier circuit, 2 is a starting circuit, 8 is an inverter circuit, and 4 is a discharge lamp lighting circuit. The inverter circuit 8 consists of two transistors 'l'r'l
The first transistor 'l'rl is connected in series with the discharge lamp lighting circuit 4, and the transistor Tr8 of lJ2 is connected in parallel with the discharge lamp lighting circuit 4. The transistor Trl is connected in series with the first transistor Trl.

The oscillation transformer T1 has an excitation coil lh and two induction coils 1gs ls , and the excitation coil 1) is inserted in series into the discharge lamp lighting circuit 4. Two induction coils I! 2m1m is connected so that voltages of opposite polarity are induced by the current flowing through the excitation cobble 1), and this voltage is applied between the base and emitter of the two transistors 'l'r1 t Trg. The commutating capacitor C1 is inserted in series with the discharge lamp lighting circuit 4.

The discharge lamp lighting circuit 4 includes a discharge lamp, a □ capacitor C1, and a current limiting element T1 for preheating the filament of the discharge lamp and making it resonate with T1. Also, the starting circuit 2 includes a starting resistor R and a trigger capacitor C! It consists of a series circuit with. Then, connect the trigger capacitor C2 between the midpoint A of the starting resistor hole and the trigger capacitor C2 and the base of the first transistor. An element that becomes conductive when the charging voltage reaches a certain voltage or higher, such as a diac Dia
It is connected via c.

Next, the lighting operation in the above configuration will be explained. At the same time as the power is turned on, the trigger capacitor 02 connects to the starting resistor R.
is charged at a predetermined time constant.

When this charging pressure reaches a certain value or more, the diac pi
ac conducts, and the charge of the capacitor is discharged through this diac. This triggers the first transistor Trl to conduct, commutating capacitor C1, capacitor Ox, m current element T, first transistor. T
A preheating current flows through r1 to the filament of the discharge lamp. Then, preheating is eventually completed and the discharge lamp is turned on by applying a high resonant voltage. At this time, after the preheating current and discharge lamp lighting, the lamp current IL flows through the excitation coil 1) of the oscillation transformer T1 and the commutating capacitor C1, so the polarity of the induction coil wound around the oscillation transformer T1 is changed to the first polarity. The polarity of the other induction coil 1m is changed to the second transistor rllr, in the direction that maintains the conduction of the transistor 'l'r1.
If you wind it in the direction that keeps it non-conducting, the oscillation transformer T1
Eventually, the lamp current IT, gradually decreases due to the magnetic saturation of the excitation coil I! 1 as well, the oscillation transformer T1 is magnetized in the opposite direction, and therefore the polarity of the voltage induced in the induction coil/gsj's is also reversed. This induced voltage increases as the lamp current decreases. Then, almost at the same time that the lamp current stops flowing, the first transistor Trl activates the induction coil l! The voltage generated in the induction coil 1m causes the transistor 'l'rg in the other section 2 to become conductive triggered by the voltage generated in the induction coil 1m. When the second transistor TrB becomes conductive, the charge accumulated in the commutating capacitor C1 is transferred to the second transistor Tr→excitation circuit I! 1→
Discharge occurs through the closed loop of current-limiting element T, discharge lamp L, and capacitor C1, lighting the discharge lamp. In this case, since the discharge current decreases with time, the magnetization direction of the oscillation transformer T1 is reversed again. Then, almost at the same time as the discharge current stops flowing, due to the voltage generated in the induction coil lsmls! The transistor Tr1 of g1 becomes conductive, while the second transistor Trg turns non-conductive. Then, a lamp current flows through the loop of rectifier circuit 1 → commutator capacitor C1 → discharge lamp L → excitation coil lx → transistor of Igl → rectifier circuit 1, and lighting is maintained. Hereinafter, by utilizing the magnetic saturation of this oscillating "is" Tl, the first and second transistors Tr
l*'l'rl is alternately made conductive and non-conductive to maintain lighting of the discharge lamp. In the figure, D is a diode for discharging the charge of the trigger capacitor CI through the first transistor 'I'r1.

The problem that the invention attempts to solve.

By the way, in the discharge lamp lighting device as described above, the starting circuit 2 is connected to the resistor hole and the trigger capacitor C! Since it is constructed from a series circuit with , it has the following drawbacks.

That is, it is sufficient for the starting circuit 2 to act to start the inverter circuit 8, and it is undesirable for the starting circuit 2 to act even after the inverter circuit has been started because it increases circuit loss. Since the trigger capacitor O can be charged at any time through the starting resistor R, and can be discharged through the diode D at any time when the first transistor D is conductive, the trigger is activated not only at startup but also thereafter. Since the capacitor CI is repeatedly charged and discharged, a current flows through the starting resistor R, resulting in increased circuit loss and a corresponding deterioration in efficiency.

In view of this, the present invention attempts to eliminate the above-mentioned drawbacks by using a switching element that is conductive only when the inverter circuit is started, in place of the starting resistor. [
.

Embodiment FIG. 1 shows an embodiment of the present invention, and the same parts and elements as those of the conventional device shown in FIG. 8 are given the same reference numerals.

Reference numeral 5 denotes a switch element that is conductive for a short time immediately after the power is turned on, and in the illustrated example, it consists of one transistor Tr8, a diode DS1 inserted in series I (inserted in the base circuit), and an electrolytic capacitor 04. 5 operates as follows. First, when the power is turned on, a DC voltage with a positive potential on the %B1 side is generated between the output terminals B1- and B9 of the rectifier circuit 1. This DC voltage is applied to the diode Dg,
The electrolytic capacitor C4 is connected to the base of the transistor Tr, causing the base current to flow.
Make a conductive. When the transistor Tr becomes conductive,
The trigger capacitor C2 is connected to the transistor TrB.
charged by the output voltage of the rectifier circuit.

Then, when the charging voltage of the trigger capacitor C2 reaches a certain voltage, the diac Di ac becomes conductive, discharging the charge of the capacitor C2, and triggering the transistor @1. This activates the inverter circuit 8. Once started, the oscillation transformer T
Oscillation is sustained by magnetic saturation of 1. On the other hand, in the switch element, the electrolytic capacitor C4 begins to be charged due to the base current flowing through the transistor Trm.

Since the charging time constant is made small by reducing the capacitance and series resistance of the electrolytic capacitor, charging of the electrolytic capacitor C4 is completed soon after the inverter circuit 8 is started. When the electrolytic capacitor 04 is fully charged, the base current stops flowing and the transistor Trg
becomes non-conducting. Here, since the electrolytic capacitor C4 is charged with a polarity opposite to that of the diode Dl as shown in the figure, its discharge resistance is extremely high, and therefore the charge stored in the capacitor O4 is not easily discharged. Therefore, the switching element 5 is not turned on for a short period of time immediately after the WE power is turned on, and is not turned on during the subsequent four periods of inverter oscillation. still,
As the switch element, other than the configuration shown in the drawings, for example, a type called a non-contact switch such as a thyristor can also be used. Furthermore, the transistors of the inverter circuit 8 can be of the pnp type in addition to the npn type shown in the figure, and furthermore, a MOSFET can be used. NPN-type and PNP-type transistors operate with current signals, while MOSFETs operate with voltage signals, but they are basically the same in that conduction and non-conduction are controlled by base input or gate input. be. 1st. FIG. 2 shows an embodiment in which a MOSFET is used as the second transistor. In the figure, Ml and Mg are MO
It is an SFET.

Effects of the Invention In the present invention, as explained above, the starting circuit is configured with a series circuit of a switch element that conducts only for a short period of time immediately after power is turned on, and a trigger capacitor. Although it is charged with the power supply voltage and discharged through elements such as diacs, there is very little charging or discharging during the subsequent inverter oscillation period, so the startup circuit consumes power only when starting the inverter circuit. Compared to conventional devices that constantly charge the trigger capacitor through the starting resistor and discharge it every half cycle through the diac and diode, the circuit loss is significantly lower, and the efficiency is therefore higher. The table below lists actual measurement data for the device of the present invention and the conventional device. In this data, the circuit loss is 1.7W for the device of the present invention and 2.04W for the conventional device, and the difference between the two is 0.84W. This difference in circuit loss is considered to be due to the difference in the configuration of the starting circuit. Although the difference in circuit loss of 0.84W seems numerically small,
If we focus only on the circuit loss, it is 2.04 (W) 16.
This means that 0.84 (W), which corresponds to 7 (%), has been reduced, resulting in a circuit loss reduction of 16.7%.

[Brief Description of the Drawings] Figure Wt is an overall circuit diagram of a discharge lamp lighting device as an embodiment of the present invention, and Fig. 2 is an overall circuit diagram of a discharge lamp lighting device as another embodiment of the invention. FIG. 8 is an overall circuit diagram of a conventional discharge lamp lighting device. l... Rectifier circuit, 2... Starting circuit, 8... Inverter circuit, 4... Discharge lamp lighting circuit, 5... Switch element, Trl, Ml... First switching means,'
l'r1゜M! ...Second switching means, Tl.
...Oscillation transformer, /1...excitation coil sl*, 1m
... Induction coil, 01 ... Commutation capacitor, C2.
...Trigger capacitor, Di ac... element.

Claims (3)

[Claims] (1) Consisting of a rectifier circuit, a starting circuit, an inverter circuit, and a discharge lamp lighting circuit, the inverter circuit includes first and second switching means, an oscillation transformer, and a commutating capacitor, and the first switching means is used for lighting the discharge lamp. The second switching means is connected in series with the first switching means while being connected in parallel with the discharge lamp lighting circuit, and the oscillation transformer is inserted in series with the discharge lamp lighting circuit. It has an excitation coil and two induction coils, 2
The two induction coils induce voltages of opposite polarity to each other by the lamp current flowing through the excitation coils, and this voltage is transferred to the first and second coils.
In addition to the first switching means, both switching means are configured to be made conductive and non-conductive alternately, and a commutating capacitor is inserted in series with the discharge lamp lighting circuit and is charged when the first switching means is conductive. In a discharge lamp lighting device configured to discharge when the second switching means is conductive, the starting circuit comprises a series circuit of a trigger capacitor and a switch element that conducts for a short time immediately after power is turned on; The intermediate point between the element and the trigger capacitor is connected to the first switching means via an element that becomes conductive when the charging voltage of the trigger capacitor reaches a certain voltage or higher. discharge lamp lighting device. (2) The discharge lamp lighting device according to claim (1), wherein the first and second switching means are transistors or MOSFETs. (3) The switch element is composed of one transistor and a series circuit of a capacitor and a diode inserted in the base circuit of this transistor. Immediately after the power is turned on, base current flows through the diode and capacitor and the transistor becomes conductive. However, when the charging of the capacitor is completed, the base current stops flowing and the transistor becomes non-conductive. lighting device.