| 摘要 |
PURPOSE: A zero crossing detection apparatus of a power line communication system is provided to enhance a transmission reliability of a power line communication signal by measuring a rising edge of a zero crossing pulse, a pulse average time of a falling edge, a falling period time from a falling edge to the next falling edge, computing a zero crossing synchronous time by subtracting a pulse average time from a falling period time, toggling a signal after the zero crossing synchronous time at the falling edge time and accurately detecting the position of a zero crossing. CONSTITUTION: A zero crossing detection unit(20) includes divide voltages(R1 and R2) which divide a direct current voltage rectified by a bridge rectifier(13) of a power unit(10), a condenser(C4) for filtering a noise component included in a direct current voltage rectified by the bridge rectifier(13), a transistor(TR1) turned on/off by receiving a voltage signal divided by the divide voltages(R1,R2). Resistors(R3,R4) input a high level voltage signal which is synchronous to a zero crossing of an alternating voltage into a controller(30) when the transistor(TR1) is turned on, and a condenser(C5) for filtering a noise component included in a voltage signal inputted into the controller(30).
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