Signal detection circuit and signal system

The embodiment of the invention provides a signal detection circuit and a signal system, the signal detection circuit is applied to a system comprising an isolation circuit, a control end circuit andan isolated side circuit, and the circuit comprises a signal acquisition module, a signal sending module and a microprocessor; the signal acquisition module is used for acquiring a to-be-detected signal of the control end circuit and generating a level detection signal according to the to-be-detected signal; the signal sending module comprises a first photoelectric coupler; the input end of the first photoelectric coupler is connected with the output end of the signal acquisition module, the first output end of the first photoelectric coupler is connected with a detection pin of a microprocessor, and the signal sending module is used for sending the level detection signal to the microprocessor; and the microprocessor generates a detection result according to the level detection signal. Thesignal detection circuit