Patent ID: 8115405
Filing Date: 2012-02-14
Classification: H05B,Y02B

Abstract:
1. A high pressure discharge lamp lighting device, comprising: a DC power source circuit; a power supply circuit for converting an output from the DC power source circuit into a square wave AC output to be supplied to a high pressure discharge lamp; a starting circuit for applying a high voltage output for lamp startup to the high pressure discharge lamp; a control circuit for controlling the DC power source circuit, the power supply circuit and the starting circuit; and a half-wave discharge detection circuit for detecting a half-wave discharge in which load voltages or load currents of two half periods of two different polarities of the square wave AC output are asymmetric with each other, wherein the half-wave discharge detection circuit detects the half-wave discharge at an initial stage of the lamp startup from dielectric breakdown of the high pressure discharge lamp until a lamp voltage of the high pressure discharge lamp approximates a rated lamp voltage, and judges that the half wave discharge has occurred, when the half-wave discharge detection circuit detects that the absolute value of a load voltage difference or a load current difference of the two different polarities is larger than a maximum variation of a load voltage difference or a load current difference of the two different polarities of the square wave AC output during lighting of the discharge lamp when the lamp voltage of the high pressure discharge lamp approximates the rated lamp voltage, and wherein the control circuit adjusts the output of each of at least one of the DC power source circuit, the power supply circuit, and the starting circuit when the half-wave discharge detection circuit detects the half-wave discharge, thereby controlling the magnitude of a voltage of a square wave half period of one polarity having a load voltage of a larger magnitude and that of a square wave half period of the other polarity having a load voltage of a smaller magnitude to approximate to each other.