| 摘要 |
PURPOSE: A power line communication circuit for a multi air-conditioner is provided to previously prevent a signal distortion or attenuation through an impedance matching with a power line using a two-wire power line communication type and embody a low cost and compactness. CONSTITUTION: A microcomputer(10) performs an entire control function regarding the transmission and receipt of information so that operations of an outdoor instrument and an indoor instrument are determined, and has a transmission port(11) and a receipt port(12). A carrier signal generating unit(20) has the first IC(20), third and fourth resistors(R3,R4), and first and second capacitors(C1,C2) for generating a carrier signal for receiving an inverse signal of a transmission signal outputted through the transmission port(11) and transmitting the receives signal when the transmission signal is inputted to the first transistor(Q1) through the first resistor(R1) and is inversely outputted. An amplifying unit(30) has second and third transistors(Q2,Q3) and sixth and seventh resistors(R6,R7) for amplifying the transmission signal when the transmission signal inserted into the carrier signal is received. A communication coil(41) is connected with a power line for performing a transmission and matching function of a signal. A coupling circuit unit has third and fourth capacitors(C3,C4) and a DC voltage supply unit(42). A signal demodulating unit(50) has tenth to thirteenth resistors(R10-R14), the forth transistor(Q4), and the second IC(51) for demodulating information received from the power line through the coupling circuit unit.
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