Signal conversion circuit, heart rate sensor and electronic device

A heart rate sensor, comprising a signal conversion circuit, wherein the signal conversion circuit comprises:

• a photoelectric conversion circuit, configured to convert an optical signal into a current signal, wherein the current signal in a first phase comprises a signal converted from a useful optical signal, a modulated optical signal and a background optical signal in the optical signal, and the current signal in a second phase comprises a signal converted from the background optical signal;
• a differential signal conversion circuit, connected to the photoelectric conversion circuit, and configured to convert the current signal into a first differential signal and a second differential signal, wherein the first differential signal is an integration signal of the current signal in the first phase, and the second differential signal is an integration signal of the current signal in the second phase;
• and
• a subtraction amplifier, connected to the differential signal conversion circuit, and configured to subtract the second differential signal from the first differential signal and amplify an obtained difference value to generate a third differential signal.