JPS6050896A - 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 [Technical Field of the Invention] The present invention relates to a discharge lamp lighting device for lighting a discharge lamp with direct current.

[Technical backbone of the invention and its problems] Conventionally, this type of discharge lamp lighting device is shown in Figures 1 and 3.
The one shown in the figure is known. That is, the device shown in FIG.
F-driven base drive circuit 4 and inverter transformer 5
A chopper circuit 7 and a high voltage generation circuit 8 are connected to the secondary winding of the inverter transformer 5 in the inverter circuit 6 via diodes, and a low voltage circuit 9 is connected to the secondary winding. They are directly connected, and the outputs of the chopper circuit 7 and low voltage circuit 9 are supplied to the discharge lamp 11 via the diode and the starting circuit 10, and the output of the high voltage generating circuit 8 is supplied to the starting circuit 10. As shown in FIG. 2, the high voltage generating circuit 8 includes a pair of N and PN type transistors 12 and 13 which are switching elements, a primary winding connecting both transistors 12 and 13, and a secondary winding serving as an output terminal. An inverter circuit consisting of an inverter transformer 14 consisting of a winding and a base winding that drives the bases of both the transistors 12 and 13, and an inverter circuit connected to the secondary winding of the transformer 14 of this inverter circuit via a current limiting coil 15. die bridge circuit 16
It consists of The inverter circuit 6 and chopper circuit 7 constitute a lighting control circuit during normal operation.

However, although such a device can reduce the step-up ratio in the high voltage generating circuit 8, it requires transistors 12 and 13 with high withstand voltage, which is not economical and increases loss in the starting resistor 18, 19. As the efficiency of the high voltage generation circuit 8 decreases, the peak value of the current flowing through the transistors 2 and 3 of the inverter circuit 6 increases, resulting in an increase in circuit loss.

Furthermore, in the one shown in FIG. 3, an inverter lance 17 having a tertiary winding is provided in the inverter circuit 6, and a high voltage generating circuit 8 is connected to the tertiary winding via a diode.

However, in this case, an inverter transformer provided with a tertiary winding must be used, and a diode must also be used, which has the disadvantage of further worsening economic efficiency.

[Object of the Invention] The present invention has been made to eliminate such drawbacks, and an object thereof is to provide a discharge lamp lighting device that can improve economical efficiency and reduce circuit loss.

[Summary of the Invention] This invention provides a lighting control circuit that supplies a DC lamp current during steady lighting of a discharge lamp, a low voltage circuit that supplies a large DC current to the discharge lamp when the discharge lamp is started, and a lighting control circuit that supplies a DC lamp current to the discharge lamp when the discharge lamp is started. In a discharge lamp lighting device comprising a high voltage generating circuit consisting of a switching circuit that supplies energy necessary for transition to arc discharge, power is supplied to the high voltage generating circuit from the low voltage circuit.

[Embodiments of the invention] Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 4, an inverter circuit 22 is connected to the DC power supply 21.
are connected. The inverter circuit 22 has a pair of NP
It is formed of an N-type switching transistor 234, an inverter transformer 25 in which both transistors 23 and 24 are connected to the primary winding, and a base drive circuit 26 that drives both transistors 23 and 24 alternately on and off. There is. Both ends of the secondary winding of the inverter transformer 22 are connected to each other via diodes 27 and 28, respectively. A chopper circuit 29 is connected between the connection point of the diodes 27 and 28 and the midpoint of the secondary winding of the inverter transformer 25, and a 1QlJ voltage is connected between both ends of the secondary winding and the midpoint. A low voltage circuit 30 is connected between the intermediate taps. The chopper circuit 29 has a series circuit of an NPN transistor 31 and a current limiting coil 32 connected between one input terminal and one output terminal, and capacitors 33 and 34 are connected between the input terminals and between the output terminals, respectively. A diode 35 is connected between the output terminals via the current limiting coil 32 with the polarity shown. The transistor 31 is controlled on and off by, for example, a rectangular wave oscillation circuit 36. The output of the chopper circuit 29 is supplied to a discharge lamp 39 via a diode 37 and a starting circuit 38 in series. The inverter circuit 22, the diodes 27, 28, 37, and the chopper circuit 29 constitute a lighting control circuit for steady lighting of the discharge lamp and sometimes for supplying a DC lamp current. The low voltage circuit 30 connects the intermediate taps to each other at 11. Coils 40, 41 and diodes 42, 43 which are electrically coupled are connected in series, respectively, and a capacitor 44 is connected between the connection point and the middle point of the secondary winding of the inverter transformer 22. are doing. An input terminal of a high voltage generating circuit 45 is connected between both ends of the capacitor 44 of the low voltage circuit 30. The output end of the high voltage generation circuit 45 is connected to the starting circuit 3.
8 to the discharge lamp 39. The high voltage generation circuit 45 includes a pair of NPN transistors 46.47 which are switching elements, and both transistors 46.47.
A primary winding whose collectors are connected to both ends thereof and whose bases are connected to the midpoint through resistors 48 and 49, respectively, and a base winding which is connected between the bases of both transistors 46 and 47 through a resistor 50. The full-wave rectifier diode bridge circuit 53 is connected to the secondary winding of the inverter transformer 516 via a current-limiting coil 52. The low voltage circuit 30 connects the connection point of its diodes 42 and 43 to the anode of the diode 37 via a diode 54.

In the device according to the present invention configured as shown in FIG.
A voltage is applied to the high voltage generating circuit 45 and the high voltage generating circuit 45, respectively. The starting circuit 38 also operates. However, first the starting circuit 38
The discharge lamp 39 is started and glow discharge occurs. Then, the discharge lamp 39 shifts from glow bt electricity to arc discharge due to the application of high voltage from the high voltage generation circuit 45. Thereafter, the voltage across the discharge lamp 39 becomes low, and at this time, a large current is supplied to the discharge lamp 39 by the low voltage circuit 30 via the diode 54. In this way, the discharge lamp 39 eventually enters a steady lighting state. In this steady lighting state, the voltage across the discharge lamp 39 increases, so the diode 54 is reverse biased and the supply of current from the low voltage circuit 30 is stopped. Therefore, in this state, current is supplied from the two chopper circuits and the discharge lamp performs steady lighting.

Since the high voltage generating circuit 45 is supplied with power from the low voltage circuit 30, the transistors 46 and 47 used do not need to have high breakdown voltages. For example, chopper circuit 2
9 is approximately 150V and the voltage generated by the low voltage circuit 30 is approximately 50V]~Run raster 46.4
The withstand voltage of the battery can be reduced to about 1/3 of that of the conventional technology. Further, since a transistor with a high withstand voltage is not required, it is possible to improve the process efficiency. Furthermore, the inverter transformer 25 of the inverter circuit 22 is connected to the high voltage generating circuit 4 as in the conventional case.
There is no need to provide a separate winding for power supply to 5,
In this respect as well, economical efficiency can be improved.

Furthermore, due to the action of the diode 54, the output voltage from the chopper circuit 29 is not applied to the high voltage circuit 30 (the low voltage circuit is not destroyed).

Although an inverter-type high-voltage generation circuit is used in the embodiment, the present invention is not limited to this, and a chopper-type high-voltage generation circuit may also be used.

[Effects of the Invention] As detailed above, according to the present invention, switching elements such as transistors constituting the high voltage generation circuit can be used with low voltage resistance, and a separate winding can be used to supply power to the high voltage generation circuit. Therefore, it is possible to provide a discharge lamp lighting device that does not require the use of a circuit, improves economic efficiency, and can reduce circuit loss.

[Brief explanation of the drawing]

1 to 3 are circuit diagrams showing a conventional example, and FIG. 4 is a circuit diagram showing an embodiment of the present invention. 21... DC power supply, 22... Inverter circuit, 29
...Chopper circuit, 30...Low voltage circuit, 39...
Discharge lamp, 45...High voltage generation circuit. Applicant's agent Patent attorney Takehiko Suzue 9-

Claims (1)

[Claims] A lighting control circuit that supplies a DC lamp current when a discharge lamp is steadily lit; a lighting control circuit that supplies a large DC current to the discharge lamp when the discharge lamp is started; and when the discharge lamp is steadily lit, the supply of current is stopped. and a high-voltage generating circuit consisting of a switching circuit that is supplied with power from the low-voltage circuit to generate high voltage and supplies the energy necessary for transitioning the discharge lamp from glow discharge to arc discharge. A discharge lamp lighting device characterized by: