Patents Examined by Haissa Phuogene
  • Patent number: 6051940
    Abstract: A series resonant ballast safety control circuit for controlling the operation of a ballast when a lamp is removed from a lamp fixture. The safety control circuit senses a diode clamp current and activates a transistor to ground one of the terminals of a dimming control circuit. The dimming control circuit reduces the duty cycle of one of the inverter transistors to decrease the available output voltage and reduce the through-lamp leakage current to safe levels. Once the lamp is replaced in the lamp fixture, the safety control circuit no longer controls the dimming control circuit and the ballast returns to normal operation. In another embodiment, the safety control circuit is used with a boost power factor correction circuit in a non-dimming ballast system to reduce the current provided to the lamp load.
    Type: Grant
    Filed: April 30, 1998
    Date of Patent: April 18, 2000
    Assignee: MagneTek, Inc.
    Inventor: Ganesh Arun