Patent ID: 8885349

Claim:
A daughter circuit board for interface signal conversion, comprising: a) a plurality of circuit units integrated on the daughter circuit board; and b) eight ports for communicating with a control system of a user terminal; wherein said eight ports comprise: M 1 : a signal input port of analog control, which has a voltage of 9-40 V DC, a frequency of 75-166 Hz, and a current of <10 Ma, and signals passing through the port being converted by a first signal conversion circuit ( 1 ) of the daughter circuit board; M 2 : a signal port for activating a fan mode, signals passing through the port being converted by a second signal conversion circuit ( 2 ) of the daughter circuit board; M 3 and M 4 : signal ports of speed feedback, which are connected to a third signal conversion circuit ( 3 ) of the daughter circuit board, and output n pulses per rotation; M 5 : a reserved signal port, signals passing through the port being converted by a fourth signal conversion circuit ( 4 ) of the daughter circuit board; M 6 : a port of component object mode (COM), which is a ground line of signal lines and a common terminal of control signals; M 7 : a port of DC power supply, which has a voltage of 8-30 V, and a current of <30 mA; and M 8 : a R/T port, which is connected to a bidirectional asynchronous half-duplex communication data line ( 5 ) of the daughter circuit board, for data transmission between the daughter circuit board and the control system of the user terminal.