Lighting device for high pressure discharge lamp

Abstract

To prevent lamp extinction during dead time of an inverter circuit of a full bridge system, to reduce delays of the rising time and the falling time of rectangular waves which have been output by the inverter circuit and to prevent formation of a phenomenon of momentary darkening of the radiant light, the discharge lamp (3) is operated with an alternating current with rectangular waves which is produced by an inverter circuit of a full bridge system (2). When the inverter circuit of the full bridge system (2) is driven a dead time is taken in which all switching devices (Q2~Q5) are turned off (dead time Td). In the rear stage of the inverter circuit of the full bridge system (2), there is an inductance (L2). The value of the inductance (L2) is fixed such that LL>=VL / IL. Td (VL being the luminous voltage of the discharge lamp, IL being the current and Td the dead time). Current can flow in the discharge lamp (3) during the dead time by the energy stored in this inductance.

Description

technical field [0001] The present invention relates to a high-pressure discharge lamp lighting device for lighting a high-pressure discharge lamp used in a liquid crystal projector or the like. Background technique [0002] Conventionally, a lighting circuit that uses an electronic circuit to light a high-pressure discharge lamp with a rectangular wave, for example, has Figure 5 circuit shown. [0003] Figure 5 The circuit shown is composed of a switch element Q1, a DC power supply, switch elements Q2-Q5, a full-bridge circuit 2 composed of diodes D2-D5, and an igniter 4 to form a lighting circuit. [0004] The lighting circuit shown in the figure supplies voltage and current to the full-bridge circuit 2 from the DC power supply, and alternately conducts the switching elements Q2, Q5, Q3, and Q4 of the full-bridge circuit 2 to supply voltage and current to the high-pressure discharge lamp 3. The alternating rectangular wave voltage makes the high pressure discharge lamp ...

AI Technical Summary

Problems solved by technology

Therefore, it is difficult to quickly output the rectangular waves of the switching elements Q2 to Q5 of the full-bridge circuit 2, and the radiated light of the high-pressure discharge lamp becomes dark instantaneously.

This decrease in luminance is a fatal problem when used as a light source for a projection type projector device

In addition, L2 needs to use a large-scale product of 1mH, so it is difficult to reduce the size and weight of the lighting power supply

[0011] In addition, when C3 and L2 are set to the above values, the oscillating current flowing to the high-pressure discharge lamp has a frequency of about 16kHz and a period of about 63μsec, so waveform vibration, overshoot, and undershoot are likely to occur.

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