| 摘要 |
PURPOSE:To reliably inform a user of the necessity to replace a discharge lamp by displaying the emissionless state via the flickering of the discharge lamp when the discharge lamp becomes the emissionless state and displaying the emissionless state every time a dimmer switch is operated after the emissionless state display. CONSTITUTION:While a display lamp l1 is fully lit, if it approaches the life terminal stage and performs the half-wave discharge, a high-level emissionless state detection signal is outputted from an emissionless state detecting circuit 2, a counter circuit 3 is counted up once, and this signal passes an AND circuit A5 to reset a preheat timer circuit Tph. The preheating operation is thereby performed for a fixed time, then the start operation is performed again. When a dimmer switch Sd is turned on, the output of an AND circuit A8 is changed to a low level, a trigger signal is outputted from a trigger signal generating circuit 7 to set the counter circuit 3. The output signal of the counter circuit 3 becomes a low level. The emissionless state detection signal passes the AND circuit A5 again, the preheat timer circuit Tph is reset, the preheating operation and the restart operation are performed, and the emissionless state is displayed. |
