| 摘要 |
PURPOSE:To detect a phase accurately by differentiating the output of a transformer or current transformer at the front stage of an amplifying circuit. CONSTITUTION:A transformer or current transformer detects a power voltage or load current to output a sine wave to its secondary side. A slicing circuit D is connected to the secondary side to obtain a trapezoid pulse waveform. This pulse waveform is differentiated by a C-R differentiating circuit C to generate small pulses at zero-cross points of the trapezoid pulse waveform. Then, the output of a detector A is differentiated at the front stage of an amplifier B to generate plus clock pulses synchronizing securely with the power voltage or load current. Therefore, even if the power voltage or load current varies in amplitude, the phase detection never shifts in pulse generation position, so accurate phase detection is performed. |
