JPH0372197B2 - - Google Patents

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 background of the invention and its problems] Conventionally, as this type of discharge lamp lighting device, those shown in FIGS. 1 and 3 are known. That is, the one shown in FIG. 1 includes an inverter circuit 6 consisting of a DC power source 1, NPN switching transistors 2 and 3, a base drive circuit 4 that alternately turns ON and OFF the transistors 2 and 3, and an inverter transformer 5. The chopper circuit 7 and the high voltage generation circuit 8 are connected to the secondary winding of the inverter transformer 5 in the inverter circuit 6 via a diode.
At the same time, a low voltage circuit 9 is connected to the secondary winding.
The outputs of the chopper circuit 7 and the 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 NPN type transistors 12, which are switching elements.
13. An inverter circuit consisting of an inverter transformer 14 consisting of a primary winding connecting both transistors 12 and 13, a secondary winding serving as an output end, and a base winding that drives the bases of both transistors 12 and 13. A diode bridge circuit 16 is connected to the secondary winding of the transformer 14 of this inverter circuit via a current limiting coil 15. The inverter circuit 6 and chopper circuit 7 constitute a lighting control circuit during normal operation.

However, with such a device, the boost ratio in the high voltage generation circuit 8 can be made small, but the transistors 12 and 1
3 is required to have a high withstand voltage, which is not economical, and increases loss in the starting resistors 18 and 19, lowering the efficiency of the high voltage generation circuit 8, which causes the flow to the transistors 2 and 3 of the inverter circuit 6. The disadvantage was that the peak value of the current became large and the circuit loss increased.

In addition, the one shown in FIG.
An inverter transformer 17 with a next winding is provided,
A high voltage generating circuit 8 is connected to the tertiary winding via a diode.

However, in this case, an inverter transformer with a tertiary winding must be used.
In addition, a diode must be used, which further deteriorates 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 economic 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 the 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] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 4, an inverter circuit 22 is connected to a DC power source 21. The inverter circuit 2
2 is a pair of NPN switching transistors 2
3 and 24, an inverter transformer 25 having primary windings connected to both transistors 23 and 24, and a base drive circuit 26 that alternately drives both transistors 23 and 24 on and off. 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 between the diodes 27 and 28 and the midpoint of the secondary winding of the inverter transformer 25, and
A low voltage circuit 30 is connected between intermediate taps provided between both ends of the next winding and the midpoint. The chopper circuit 29 has a series circuit of an NPN transistor 31 and a current limiting coil 32 connected between one input end and one output end, and capacitors 33 and 34 connected between the input ends and the output end, respectively. and a diode 3 is connected between the output terminals via the current limiting coil 32.
5 is connected 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, diodes 27, 28, 37, and chopper circuit 29 constitute a lighting control circuit that supplies DC lamp current during steady lighting of the discharge lamp. The low voltage circuit 30 connects coils 40, 41 and diodes 42, 43, which are magnetically coupled to each other, in series between both intermediate taps, and connects the connecting point and the inside of the secondary winding of the inverter transformer 22. A capacitor 44 is connected between the point
are connected. 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 generating circuit 45 is connected to the discharge lamp 39 via the starting circuit 38. The high voltage generating circuit 45 has a pair of NPN transistors 46 and 47 which are switching elements, the collectors of both transistors 46 and 47 are connected to both ends, and the bases are connected to resistors 48 and 47, respectively.
A resistor 50 is connected between the primary winding connected to the midpoint via 49 and the bases of both transistors 46 and 47.
an inverter transformer 51 having a base winding connected via the inverter transformer 51;
A full-wave rectifier diode bridge circuit 53 is connected to the secondary winding of the converter via a current-limiting coil 52. The low voltage circuit 30 has a connection point between its diodes 42 and 43 connected to the anode of the diode 37 via a diode 54.

In the device according to the present invention configured as described above, when the DC power supply 21 is supplied, a voltage is generated on the secondary winding side of the inverter circuit 22, and a voltage is generated in the chopper circuit 29, the low voltage circuit 30, and the high voltage generating circuit 45, respectively. A voltage is applied. The starting circuit 38 also operates. First, the discharge lamp 39 is started by the starting circuit 38, and a glow discharge occurs. Then, the discharge lamp 39 shifts from glow discharge 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 chopper circuit 29 and the discharge lamp performs steady lighting.
Since the high voltage generation circuit 45 is supplied with power from the low voltage circuit 30, the transistor 4 used
As for 6 and 47, those with high withstand voltage are not required.
For example, the voltage supplied to the chopper circuit 29 is approximately
At 150V, the voltage generated by the low voltage circuit 30 is approximately 50V
In this case, the breakdown voltage of the transistors 46 and 47 can be reduced to about 1/3 of the conventional voltage. Furthermore, since a transistor with a high breakdown voltage is not required, economical efficiency can be improved. Further, there is no need to provide a separate winding in the inverter transformer 25 of the inverter circuit 22 for supplying power to the high voltage generating circuit 45 as in the conventional case, and economical efficiency can also be improved in this respect.

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

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

[Effects of the Invention] As described in detail above, according to the present invention, switching elements such as transistors constituting the high voltage generation circuit can be used with low withstand voltage, 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 drawings]

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...Chiyotsupa circuit, 30...Low voltage circuit, 39
...Discharge lamp, 45...High voltage generation circuit.

Claims (1)

[Claims] 1 A lighting control circuit that supplies a DC lamp current during steady lighting of a discharge lamp, and a lighting control circuit that supplies a large DC current to the discharge lamp when the discharge lamp is started, and that supplies current when the discharge lamp is steadily lit. A high voltage generating circuit consisting of a low voltage circuit to be stopped and 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 comprising: