| 摘要 |
PURPOSE:In a half-bridge type inverter for a discharge lamp, to protect a circuit reducing the output of the inverter in the last stage of lifetime or an overload operation of the lamp by providing protecting circuit of suitable time constant operated synchronously to one of power transistors(TR). CONSTITUTION:When one of transistors TR 3 in a TR inverter is turned on, a capacitor 9 constructing a protecting circuit of a time constant together with a resistance 8 is charged up synchronously. When the ON-duty of the TR 3 is elongated in the last stage of lifetime or an overload operation of the discharge lamp 4, the charged voltage of the capacitor 9 is elevated to turn on a TR 10, then the base current of TR 3 supplied from a current transformer 5 is shunted to prevent the elongation of the ON-duty and to reduce the output, so that the circuit of the transistor inverter can be protected with no emitter resistance for current detection and with no operation interruption. |
