| 摘要 |
PURPOSE:To remarkably simplify the circuit constitution by converting a PWM signal into a tone burst signal, outputting the result through a transformer and utilizing the result of full wave rectification as a drive voltage in a drive circuit of a PWM power amplifier utilizing a bridge type power amplifier circuit. CONSTITUTION:Transformers 9, 10 generate a tone burst signal of the same level at two secondary winding sides having a prescribed same winding ratio. An output of the secondary winding of the transformer with an intermediate tap is fed to full wave rectifiers 11, 12 of the transformer 9 and fed to full wave rectifiers 13, 14 of the transformer 10. Thus, four rectifier outputs subjected to full-wave rectification are fed to the bridge power amplifier circuit 15 as a drive signal. The bridge power amplifier circuit 15 switches the switching element while four rectifier output pulses in two pairs are used as the drive voltage. Thus, the drive circuit is of two-channel and one power supply is enough for the bridge power amplifier circuit.
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