Patent ID: 8599944

Claim:
A pulse modulation circuit comprising: an intermittent operation circuit that intermittently outputs a transmission signal according to a control signal; and a control circuit that, according to transmission data controls switching of the intermittent operation circuit between a transmission mode in which a first transmission signal is outputted and a pre-charge mode in which a second transmission signal of a lower amplitude or lower frequency than the first transmission signal is outputted, wherein the control circuit comprises a function for variably controlling a switching timing to the pre-charge mode according to a parasitic capacity of the intermittent operation circuit, and the control circuit controls the intermittent operation circuit to operate in a transmission mode when the transmission data is 1, controls the intermittent operation circuit to operate in the pre-charge mode when the transmission data is 0 and controls the intermittent operation circuit such that a period of the pre-charge mode is shorter than a period of the transmission mode.