ELECTRONIC BALLAST HAVING A DIMMING-CONTROLLING PART INCLUDING INITIAL DIMMING-CONTROLLING CIRCUIT

摘要

An electronic ballast having a dimming-controller including an initial dimming-control circuit is provided to uniformly maintain currents of an inverter and lamp by calculating a reference voltage and a comparing voltage in a comparing circuit. In an electronic ballast having a dimming-controller including an initial dimming-control circuit, a bridge rectifying unit(2) rectifies power of a power input unit(1). An inverter unit(5) drives a lamp(14) by inverting the power to a high frequency signal. The power is rectified by the bridge rectifying unit(2). A frequency oscillating unit(4) generates an oscillation frequency and applies the oscillation frequency to the inverter(5) to control brightness of the lamp(14). A frequency control unit(6) is coupled to the frequency oscillating unit(4). The frequency control unit(6) controls the oscillation frequency of the frequency oscillating unit(4). An illumination control unit generates a control signal of the frequency control unit(6). The illumination control unit includes an initial dimming control unit(10) outputting a control signal having a high level on initial driving of the ballast to have high level inverter output and outputting a control signal having a low level to have low level inverter output after a predetermined time.