| 摘要 |
PROBLEM TO BE SOLVED: To reduce a radio noise, by suppressing a high-frequency oscillation being generated when a switching element that is connected to the primary coil of a transformer is turned on. SOLUTION: A voltage generation circuit 38 supplies voltage from a power supply Vcc to a primary side coil 60A of a transformer 60, inputs a switching signal from a duty control circuit 58 to the gate of MOSFETs 50 and 52 at a specific timing and turns off current to the primary side coil 60A of the transformer 60. An AC voltage is induced at a secondary side coil 60B of the transformer 60, is subjected to all wave rectification by diodes 62 and 64, and is smoothed by a transformer 66 and a capacitor 68, and then a DC voltage is supplied to A and B phase amplification circuits 42 and 44. At this time, a resonance circuit is formed by the capacitance of the MOSFET 50, a primary side coil 60A of the transformer 60, and a capacitor 72, and is oscillated at a high frequency, thus generating a radio noise. However, ferrite beads 54 and 56 do not pass 10 MHz or higher frequency component, thus suppressing oscillation and preventing the radio noise from being generated. |
