| 摘要 |
<p>The invention relates to a controllable or dimmable electronic ballast for a low pressure discharge lamp, especially a fluorescent lamp. A halfbridge inverter (TR1, TR2; V2, V3) supplies power to a load circuit (L2, C2, C3, LL). A regulation or control block (A1/I, II) regulates the frequency of the halfbridge inverter for regulating the light output of a lamp. One branch of the halfbridge inverter is provided with current measuring elements (R2, R3, C4), from which is obtained current measurement information proportional to the load circuit power for the regulation or control block, which is further supplied separately with measurement information about a direct current that has passed through the lamp and is proportional to the internal resistance of the lamp. The latter measurement information is used for controlling regulation of the lamp at low regula tion levels of the light output. <IMAGE></p> |
