| 摘要 |
PURPOSE:To make a final life term of a discharge lamp exactly detectable with simple circuit composition by providing a circuit in which a change in a voltage level at a connection point of a capacitor and a diode is used to discriminate a full-wave discharge state from a half-wave discharge state in the discharge lamp. CONSTITUTION:A series circuit of a capacitor C3 and a diode D3 is formed so as to have a relation parallel to a discharge lamp DL1. A circuit, in which a change in e voltage level et a connection point of the capacitor C3 and the diode D3 is used to discriminate a full-wave discharge state from a half-wave discharge state in the discharge lamp DL1, is formed. Namely, a voltage Vc3 across the capacitor C3 on the full-wave discharge state is made different from that on the half-wave discharge state, and so the full-wave discharge state in the discharge lamp DL1 can be discriminated from the half-wave discharge state in it by the use of the change in the voltage level at the connection point of the capacitor C3 and the diode D3. Accordingly, discrimination of the half- wave discharge state enables the detection of a final term of the discharge lamp. |
