| 摘要 |
PURPOSE:To make the primary and the secondary circuit of an inverter transformer perfectly insulated to each other so as to construct a preheating circuit with elements of relatively low withstanding voltages by absorbing spike voltages generated during preset preheating time with a spike voltage absorbing circuit. CONSTITUTION:In a lighting circuit for a fluorescent lamp using a high frequency inverter, when a power source circuit 1 is turned on, an inverter driving circuit 4 and a preheating timer 2 are started, and a filament preheating time is set by the timer 2, during which a spike voltage absorbing circuit 3 is operated. Then spike voltage generated in an inverter transformer 6 are absorbed with the circuit 3. The driving circuit 4 operates the transformer 6 through a transistor 5 to generate AC voltages with no spike in the secondary windings S1-S3 of the transformer 6, and these voltages are applied to a fluorescent lamp 8 through a capacitor 7 to preheat the lamp 8 with a voltage lower than its starting voltage under no current. Thereby the primary and the secondary windings of the inverter transformer can be made perfectly insulated to each other to construct a preheating circuit with elements of relatively low withstanding voltages. |
