PIEZOELECTRIC TRANSFORMER LIGHT ADJUSTING NOISE REDUCTION CIRCUIT

摘要

Provided is a light adjusting noise reduction circuit in which the vibration noise accompanying turning ON/OFF of a piezoelectric transformer. A full bridge circuit (2) is controlled by a full bridge drive circuit (5) so as to switch an input voltage (VB1) from an input voltage source (1) and outputs it to a low pass filter (3). The output from the low pass filter (3) is supplied to a piezoelectric transformer (4). The output current (IO) from the piezoelectric transformer (4) is supplied to a discharge tube. Each of FET of the full bridge circuit (2) has a drive frequency decided by a voltage control type oscillator (9). The full bridge circuit (5) is connected to a duty variable circuit (6) and a peak value control circuit (22). The peak value control circuit (22) forms a rise and a fall of a waveform to be (1 - cosÉt).