| 摘要 |
PURPOSE:To prevent the electric shock in the no-load state of a fluorescent lamp with an electric circuit by providing an oscillation stopping control circuit which outputs a signal to stop the generation of the control signal to a control signal generating circuit based on the no-load signal detected with a choke in a no-load detecting circuit. CONSTITUTION:A no-load detecting circuit 10 detects the no-load state of a fluorescent lamp 4 such as that the fluorescent lamp 4 is extinguished at the life end or taken off from the socket depending on the current in a choke coil. When the fluorescent lamp is in the no-load state the current in the choke coil is cut off, then no voltage is induced in the secondary winding 12 of the choke coil to make a transistor(TR)Q3 from on-state to off-state. When the TRQ3 is made to off-state a TRQ4 is made to on-state and a voltage is applied to the emitter of the TRQ4 from a DC voltage source E through a resistance R3, and this voltage is inputted to the operation stopping input terminal P2 of an IC in a control signal generating circuit 7 as a command signal to stop the oscillation. The operation of the said circuit 7 is stopped, thus no pulse is applied to an oscillation circuit 6 to stop the oscillation of the said circuit 6. Thereby the electric shock can be prevented. |
