1. Field of the Invention
This invention relates to an apparatus for starting and operating a discharge lamp, using an inverter circuit.
2. Description of Background
An apparatus for starting and operating a discharge lamp, equipped with an inverter circuit has generally been used so as to achieve a small-sized unit with an improved efficiency. Japanese Patent Disclosure (KOKAI) No. 57-141895 discloses a conventional apparatus for starting and operating a discharge lamp. According to the invention, an AC power source is connected to a rectifier circuit including a rectifier and a smoothing capacitor, the output of the rectifier circuit being connected to an inverter circuit. The inverter circuit includes a parallel resonance circuit of an oscillation transformer and capacitor connected in parallel with a primary winding of the oscillation transformer. The resonance circuit is driven by a switching transistor. Between the base and the emitter of the transistor, a series circuit of a coupling capacitor and feedback coil magnetically coupled to the oscillation transformer is connected as a feedback circuit, via a diode. A series circuit of a diode and resistor is connected in parallel with the series circuit of the coupling capacitor and feedback coil, and a trigger resistor is connected in series with both the series circuits.
A discharge lamp is connected to a secondary coil of the oscillation transformer, via a current-limiting coil, and a starting circuit is comprised of a series circuit of diodes and silicon symmetrical switch element, and is connected in parallel with a discharge lamp.
According to the aforementioned apparatus for starting and operating a discharge lamp, since the starting circuit includes a series circuit of diodes and a silicon symmetrical switch element, a high-voltage pulse to be generated is regulated by the diode characteristic. It is, therefore, not possible to obtain an adequate high-voltage pulse.