1 voltage high limit circuit / anti lightning circuit

When the socket P9 input voltage is too high (FireWire, and the zero line) or have access to lightning and elevated voltage at the two ends of the varistor ZN402. When the above voltage protection to ZN402 ZN402 voltage, input current increases, the F401 (8a), F402 (8a) due to the overcurrent and open circuit. Thus to protect the circuit level is not due to high voltage damage. When the fire wire and the ground wire of high voltage, the voltage by S402, S401 the zn404, when the zn404 voltage exceeds the zn404 protective voltage value, the input current increases, F401, F402 due to overcurrent and open circuit, protection circuit level is not due to high voltage damage.

2 line filter circuit

Electromagnetic interference filter, also known as EMI filter. Grid interference noise can be classified into two categories: a class is grid is introduced into the equipment of outside interference; another kind is the interference generated by the device itself by the interference of power transmission line to the grid, electronic equipment is not only noise disturbance in object and a interference source. Therefore, the filter must be a two-way filter, on the one hand to filter out the electromagnetic interference of the input device, on the other hand to avoid the noise feedback power generated by the electronic device. According to the characteristics of noise, the noise can be divided into differential mode interference and common mode interference. Differential mode interference is the noise between two power supply lines, and the common mode interference is the noise of the two power supply lines. Therefore, the feed line filter should have a filtering effect on the differential mode interference and common mode interference.

The filter circuit of the machine is composed of C470, 1404, C476, C473 and LA06. Ia04 and IA06 is the common mode coils. Two common mode filter network, filter the grid or power generation of symmetric interference signal, the differential mode interference, contrast to the flux generated by the interference with the current in the common mode coils, coil inductance is almost zero, the differential mode signal had no inhibitory effect.

The C470, C476 and C473 constitute the unbalanced filter network, and filter out the asymmetric interference signals generated by the power supply and the power supply. Circuit C476, C473,.C470 is a safety capacitor, high voltage requirements.